Electric power converter management device and DC grid system

Abstract

A CEMS (3) manages at least one electric power converter (6, 9a to 9n) disposed in a DC electric power distribution grid (21) and each having droop characteristics, the CEMS generating a command value for each of the electric power converters (6, 9a to 9n). The CEMS (3), upon formulating a command value on the basis of a measurement result of each interconnection point voltage with the DC grid (21) and output electric power to the DC grid (21) for each of the electric power converters (6, 9a to 9n), calculates an estimated value of each interconnection point voltage when each of the electric power converters (6, 9a to 9n) operates, in accordance with the formulated command value. When at least one of the estimated values of the interconnection point voltages deviates from a predetermined voltage range, the command values of the electric power converters (6, 9a to 9n) are corrected.

Description

Power converter management device and DC power system

[0001] The present invention relates to a power converter management device and a DC power system, and more particularly to a management device for a power converter such as a DC / DC converter and / or an AC / DC converter having droop characteristics connected to a DC power system, and a DC power system including the management device.

[0002] In recent years CO ２ The adoption of renewable energy sources (hereafter referred to as "renewable energy"), such as solar and wind power, is progressing due to the need to reduce environmental impacts, such as emissions, and the depletion of energy resources. Renewable energy sources, such as photovoltaic (PV) power, output DC power, making them highly compatible with DC transmission and distribution. Data centers are already adopting DC power. To promote electrification in non-electrified regions of India and African countries, efforts are underway to develop AC trunk grids. In areas where trunk grid development is lagging, DC microgrids are being constructed, primarily powered by renewable energy sources such as PV. Going forward, the interconnection of neighboring DC microgrids and their connection to AC trunk grids (hybrid DC microgrids) is expected to become more common. Furthermore, Europe is scheduled to introduce a "border carbon tax" in 2026, which is expected to accelerate the adoption of renewable energy sources, such as solar power, in factories. As mentioned above, DC transmission and distribution, which has a high affinity with direct current, is expected to become more widespread in a variety of applications in the future, including factories, office buildings, local government disaster prevention centers, and the DC microgrids mentioned above, provided that its economic rationality can be guaranteed.

[0003] In general, DC transmission and distribution does not require frequency management compared to AC transmission and distribution, making converter control simpler, but it lacks the inertia inherent in AC transmission and distribution systems. In AC transmission and distribution systems, sudden changes in load power consumption or renewable energy generation can be addressed by using the inertia (the inertia of a rotating body) of a synchronous generator installed in a thermal power plant, for example. Specifically, when there is surplus power in the transmission and distribution system, the surplus power is converted into kinetic energy and stored in the rotating body (the rotational speed of the rotating body increases, causing the AC system frequency to rise). When there is a power shortage, the kinetic energy of the rotating body is converted into electrical energy and output (the rotational speed of the rotating body decreases, causing the AC system frequency to fall). However, DC transmission and distribution systems lack the inertia inherent in synchronous generators.

[0004] For this reason, development is underway of technology that imparts a pseudo-inertial force (drooping characteristic) to a DC / DC converter that transfers DC power output from a distributed power source such as a storage battery between a DC transmission and distribution system. For example, International Publication No. 2023 / 063073 (Patent Document 1) discloses a method of imparting a drooping characteristic to a DC / DC converter that boosts, boosts / bucks, or bucks DC power input from a DC power source and outputs the boosted DC power, thereby controlling the voltage at the interconnection point with the DC system.

[0005] Specifically, Patent Document 1 describes a power conversion device and a DC power supply system that include a measurement unit that measures the output current and output voltage output from a DC / DC converter and a control unit that controls the output voltage output from the DC / DC converter. The control unit includes an output current target value that is a target value of the output current output from the DC / DC converter, a correction value generation unit that generates an output current correction value that corrects the output current value based on the output current value, and a droop control unit that droops an output voltage target value that is a target value of the output voltage output from the DC / DC converter based on the output current value corrected by the output current correction value. The document describes controlling the output voltage of the DC / DC converter based on the drooped output voltage target value.

[0006] International Publication No. 2023 / 063073

[0007] When configuring a factory or microgrid with a DC distribution system, there are cases where one or more distributed power sources such as storage batteries and renewable energy devices are connected to the DC distribution system via power conversion devices to create a DC microgrid. In such cases, in addition to maintaining and managing the voltage of the DC distribution system, it is important to control the power flow between the connected distributed power sources and loads and the DC distribution system.

[0008] The power conversion device and DC power supply system described in Patent Document 1 have the current-voltage drooping characteristic as described above. Therefore, when the technology of Patent Document 1 is applied to the above-mentioned DC power distribution system, while multiple power conversion devices in the DC power distribution system can operate as masters (voltage sources), there is a concern that power flow control may be insufficient because the power flow is not taken into consideration.

[0009] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to manage a power conversion device having drooping characteristics connected to a DC system so as to perform sufficient power flow control.

[0010] In one aspect of the present disclosure, there is provided a power converter management device. The power converter management device manages one or more power converters having drooping characteristics that are installed in a DC system and exchange DC power with the DC system. The power converter management device includes a measurement result collection unit, a command value generation unit, and a command value output unit. The measurement result collection unit collects voltage measurement results at the interconnection point with the DC system managed by each power converter, and measurement results of the output current, output power, or both the output current and the output power of each power converter. The command value generation unit generates command values ​​for each power converter, including one or more of a voltage command value, a power command value, and a current command value. The command value output unit outputs the command values ​​generated by the command value generation unit to the one or more power converters. The command value generation unit estimates an interconnection point voltage between each power converter and the DC system based on the generated command values, and performs control to correct the generated command values ​​if the estimated interconnection point voltage deviates from a predetermined voltage range.

[0011] In another aspect of the present disclosure, there is provided a DC grid system including one or more power converters having droop characteristics that are installed in a DC grid to exchange DC power with the DC grid, and the management device for managing the one or more power converters.

[0012] According to the present disclosure, when an estimated value of the interconnection point voltage of each power converter with a DC grid deviates from a predetermined voltage range when each power converter operates according to a formulated command value, the power converter management device can correct the command value and output to each power converter a command value generated so that the estimated value of the interconnection point voltage falls within the predetermined voltage range. As a result, for example, it is possible to control the interconnection point voltage of each power converter to fall within a predetermined voltage range, taking into account the drooping characteristics of each power converter installed in the DC grid as well as voltage drops due to the impedance of the DC grid (resistance components are dominant in DC grids), and it is also possible to smoothly control the power flow even when load fluctuations, etc. occur.

[0013] 1 is a block diagram illustrating an example of the configuration of a DC system including a DC distribution system to which a management device for power converters according to a first embodiment is connected. FIG. 1 is a block diagram illustrating an example of the configuration of a CEMS shown in FIG. 1. FIG. 2 is a block diagram illustrating an example of the configuration of an operation plan creation circuit in the CEMS shown in FIG. 2. FIG. 3 is a block diagram illustrating an example of the configuration of a control parameter generation circuit in the CEMS shown in FIG. 2. FIG. 4 is a block diagram illustrating an example of the configuration of an AC / DC converter shown in FIG. 1. FIG. 5 is a block diagram illustrating an example of the configuration of a power converter for a distribution system storage battery shown in FIG. 1. FIG. 6 is a block diagram illustrating an example of the configuration of a power converter for a consumer PV shown in FIG. 1. FIG. 7 is a block diagram illustrating an example of the configuration of a first control circuit shown in FIG. 5. FIG. 6 is a block diagram illustrating an example of the configuration of a second control circuit shown in FIG. 7. FIG. 8 is a block diagram illustrating an example of the configuration of a first voltage target generation circuit shown in FIG. 8 and a second voltage target generation circuit shown in FIG. 9. FIG. 11 is a block diagram illustrating an example of the configuration of a first governor control circuit shown in FIG. 11. FIG. 12 is a block diagram illustrating an example of the configuration of a first mass point system calculation circuit shown in FIG. 12. FIG. 13 is a block diagram illustrating an example of the configuration of a power target generation circuit shown in FIG. 19 is a block diagram illustrating an example of the configuration of the second governor control circuit shown in FIG. 14. FIG. 19 is a block diagram illustrating an example of the configuration of the second mass system calculation circuit shown in FIG. 14. FIG. 20 is a conceptual diagram illustrating an example of the drooping characteristic of the first voltage target generation circuit or the second voltage target generation circuit. FIG. 20 is a conceptual diagram illustrating an example of the drooping characteristic of the power target generation circuit. FIG. 21 is a conceptual diagram for explaining the operating principle of the management device for the power converter according to embodiment 1. FIG. 21 is a conceptual waveform diagram illustrating a first example of the response waveform of each converter when the load power consumption by the consumer load group changes stepwise in the DC power distribution system shown in FIG. 19. FIG. 22 is a conceptual waveform diagram illustrating a second example of the response waveform of each converter when the load power consumption by the consumer load group changes stepwise in the DC power distribution system shown in FIG. 19. FIG. 22 is a sequence diagram during normal operation of the management device for the power converter according to embodiment 1. FIG. 23 is a flowchart illustrating control processing as the management device for the power converter according to embodiment 1 of the CEMS shown in FIG. 1. FIG. 24 is a flowchart illustrating detailed control processing of operation plan creation 1 in FIG.23. FIG. 24 is a flowchart illustrating detailed control processing for planning charge / discharge power for a distribution system battery in FIG. 24. FIG. 25 is a flowchart illustrating detailed control processing for predicting voltage at each power receiving point in FIG. 24. FIG. 26 is a first flowchart illustrating detailed control processing for reviewing charge / discharge power for a distribution system battery in FIG. 26. FIG. 27 is a second flowchart illustrating detailed control processing for reviewing charge / discharge power for a distribution system battery in FIG. 26. FIG. 28 is a first flowchart illustrating detailed control processing for determining whether to correct an operation plan in FIG. 23. FIG. 29 is a second flowchart illustrating detailed control processing for whether to correct an operation plan in FIG. 23. FIG. 29 is a flowchart illustrating detailed control processing for correction of a power command value for a distribution system battery in FIG. 29A. FIG. 29B is a first flowchart illustrating detailed control processing for correction of a power command value in FIG. 29B. FIG. 29B is a second flowchart illustrating detailed control processing for correction of a power command value in FIG. 29B. 37 is a flowchart illustrating detailed operation of the first AC / DC conversion circuit shown in FIG. 5. 38 is a flowchart illustrating detailed control processing of the first AC / DC conversion circuit control in FIG. 32. 39 is a flowchart illustrating detailed operation of the first DC / DC conversion circuit shown in FIG. 6. 40 is a flowchart illustrating detailed control processing of the first DC / DC conversion circuit control in FIG. 34. 41 is a flowchart illustrating control processing as a management device for the power converter according to embodiment 2 of the CEMS shown in FIG. 1. 42 is a flowchart illustrating detailed control processing of operation plan creation 2 in FIG. 36. 43 is a flowchart illustrating detailed control processing of each power receiving point voltage prediction 2 in FIG. 37. 44 is a first flowchart illustrating detailed control processing of reviewing the voltage command value of the distribution system storage battery 8 in FIG. 37. 45 is a second flowchart illustrating detailed control processing of reviewing the voltage command value of the distribution system storage battery 8 in FIG. 37. 46 is a first flowchart illustrating detailed control processing of operation plan correction 2 in FIG. 36. 47 is a second flowchart illustrating detailed control processing of operation plan correction 2 in FIG. 36.40A is a first flowchart illustrating detailed control processing for review 2 of the voltage command value of the distribution system storage battery 8 in FIG. 40A. FIG. 40B is a second flowchart illustrating detailed control processing for review 2 of the voltage command value of the distribution system storage battery 8 in FIG. 40A. FIG. 40C is a flowchart illustrating control processing as a management device for a power converter according to embodiment 3 of the CEMS shown in FIG. 1. FIG. 42 is a flowchart illustrating details of control processing for operation plan creation 3 in FIG. 42. FIG. 43 is a flowchart illustrating detailed control processing for review of the voltage and power command values ​​of the distribution system storage battery 8 in FIG. 43. FIG. 42 is a first flowchart illustrating detailed control processing for operation plan correction 3 in FIG. 42. FIG. 42 is a second flowchart illustrating detailed control processing for operation plan correction 3 in FIG. 42. FIG. 45B is a first flowchart illustrating detailed control processing for review 3 of the voltage command value and power command value of the distribution system storage battery 8 in FIG. 45B. FIG. 11 is a block diagram for calculating a transfer function of the first voltage target generation circuit or the second voltage target generation circuit shown in FIG. 11. FIG. 14 is a block diagram for calculating a transfer function of the power target generation circuit shown in FIG. 14. 10 is a block diagram illustrating an example of the configuration of a first voltage target value control circuit shown in Fig. 9. FIG. 11 is a block diagram illustrating an example of the configuration of a power target value control circuit shown in Fig. 9.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their description will not be repeated in principle.

[0015] First Embodiment. FIG. 1 is a block diagram showing a configuration example of a DC system including a DC distribution system 21 to which a power converter management device according to a first embodiment of the present disclosure is connected. In the first embodiment, the standard DC voltage (reference voltage) of the DC distribution system 21 is 1500 V, and the appropriate voltage range is 1350 V to 1650 V (i.e., the appropriate voltage range is ±10% of the standard DC voltage). The reference voltage is not limited to 1500 V, but can be any voltage value such as 600 V, 380 V, or 6000 V. The appropriate voltage range is also not limited to ±10% of the standard appropriate voltage, but can be any range such as ±5% of the standard appropriate voltage, or −10% to +2%.

[0016] Referring to FIG. 1 , the DC power system according to the first embodiment includes a substation 1, a DSO (Distribution System Operator) 2 as a power distribution automation system, a CEMS (Community Energy Management System) 3 corresponding to a “power converter management device,” a switch 5, an AC / DC converter 6, and a DC power distribution system 21.

[0017] The AC power from the substation 1 is input to the switch 5 via the AC distribution system 20a. The output of the switch 5 is connected to the AC / DC converter 6 via the AC distribution system 20b. In the first embodiment, the AC power from the substation 1 is described as being three-phase AC, but the AC power is not limited to three-phase AC and may be single-phase AC, single-phase three-wire AC, or the like.

[0018] The AC / DC converter 6 converts AC power supplied from the AC distribution system 20b into DC power and outputs it (forward current) to the DC distribution system 21. Furthermore, if there is surplus power in the DC distribution system 21, the AC / DC converter 6 converts the surplus DC power of the DC distribution system 21 into AC power and outputs it (reverse current) to the AC distribution system 20b. In this way, the AC / DC converter 6 has a power conversion function between AC power and DC power for connecting the DC distribution system 21 to the AC distribution system 20b.

[0019] Power converters 9a to 9n for distribution system batteries and consumer load groups 10a to 10n, which respectively control the charging and discharging of n (n: natural number) storage batteries (hereinafter referred to as "distribution system batteries") 8a to 8n arranged as distributed power sources for the distribution system, are connected to the DC distribution system 21 via distribution system impedances (simply referred to as "impedances" in the figure) 7a to 7n. In Figure 1, the connection points of the DC distribution system 21 with the power converters 9a to 9n and the consumer load groups 10a to 10n are denoted as DC distribution systems 21a to 21n.

[0020] The power converters 9a to 9n are arranged corresponding to the power distribution system batteries 8a to 8n (denoted as "BAT" in FIG. 1), respectively. The power converters 9a to 9n exchange DC power with the DC power distribution systems 21a to 21n using the charging and discharging power of the power distribution system batteries 8a to 8n. That is, the power converters 9a to 9n output DC power (charging power or discharging power) from the power distribution system batteries 8a to 8n to the DC power distribution systems 21a to 21n. The power converters 9a to 9n can also charge the power distribution system batteries 8a to 21n using surplus power in the DC power distribution systems 21a to 21n.

[0021] The consumer load groups 10a to 10n are configured to include consumer loads 11a to 11n, PV panels 12a to 12n, and consumer PV power converters 13a to 13n, respectively. The power converters 13a to 13n output DC power generated by the PV panels 12a to 12n to DC distribution systems 21a to 21n.

[0022] In the following, when referring collectively to the distribution system impedances 7a to 7n, the distribution system batteries 8a to 8n, the power converters 9a to 9n for the distribution system batteries, the consumer load groups 10a to 10n, the consumer loads 11a to 11n, the PV panels 12a to 12n, and the power converters 13a to 13n for consumer PV, they will be referred to as the distribution system impedance 7, the distribution system battery 8, the power converter 9 (for distribution system batteries), the consumer load group 10, the consumer load 11, the PV panel 12, and the power converter 13 (for consumer PV).

[0023] In the following description of the first embodiment, for ease of understanding, consumer loads 11, which are the power consumption loads of multiple nearby consumers, PV panels 12 attached to the consumer's homes, and power converters 13 for the consumer's PV, are grouped together as a consumer load group 10. The following description will be continued assuming that a power generation amount prediction database 351 and a power consumption prediction database 352, which will be described later, are constructed for each consumer load group.

[0024] The DSO 2 collects, via the CEMS 3, for example, 30-minute power consumption of each consumer load group 10, power generation and status information of the PV panels 12, charge / discharge power of the distribution system storage batteries 8, SOC (State of Charge), and SOH (State of Health) information. Furthermore, based on the collected results, the DSO 2 generates, for example, 30-minute supply power information from the upper (trunk) system and outputs it to the CEMS 3. The SOC is an index indicating the amount of charged power (charging energy) of each distribution system storage battery 8, and is expressed, for example, as a percentage of the current charge amount relative to the full charge capacity. The SOH is an index indicating the degree of deterioration of each distribution system storage battery 8, and is expressed, for example, as a percentage of the current (degraded) full charge capacity relative to the full charge capacity in the initial state.

[0025] The CEMS 3 collects and manages information such as charge / discharge power, SOC, and SOH of the distribution system storage battery 8 via the communication line 22, generates power command values ​​and voltage command values ​​for the AC / DC converter 6 and each power converter 9 (creates a storage battery operation plan), and generates and manages drooping characteristics.

[0026] In the first embodiment, the weather forecast server 4 outputs weather forecast information every 30 minutes. The weather forecast information is used to predict the amount of power generation of the PV panel 12. Note that the information from the weather forecast server 4 is not limited to every 30 minutes, and may be output at shorter time intervals (for example, every minute) or at longer time intervals (for example, every six hours).

[0027] In the first embodiment, under normal circumstances, the DC distribution system 21 is interconnected with the AC distribution system via the AC / DC converter 6. On the other hand, during a power outage, the DC distribution system 21 is disconnected from the upper transmission (main) system by the switch 5, and the DC distribution system 21 can configure a DC independent system (DC microgrid) using n distribution system batteries 8. The DC distribution system 21 corresponds to an example of a "DC system" both when it is interconnected with the AC distribution system and when it is operating as a DC independent system.

[0028] When configuring a DC microgrid, the power converter 9 for the distribution system battery is controlled so that the voltage at the interconnection point with the DC distribution system is 1500 V. If a sudden change in the consumer load 11 n of consumer load group n causes a power shortage, the DC voltage of the DC distribution system 21 n drops in response to the power shortage. This causes the power converter 9 n to detect the power shortage and operate to increase the discharge power of the distribution system battery 8 n.

[0029] Similarly, the power converter 9 for the other power distribution system connected via the power distribution system impedance 7n also supplies excess or shortage power until a steady state is reached (if the power converter 9 for the power distribution system does not have a drooping characteristic, this refers to a state in which the DC voltage of the DC distribution system 21n converges to 1500 V).

[0030] After the steady state is reached, if the control target value of each interconnection point voltage by each power converter 9 is the same (for example, 1500 [V]), the power shortage due to the power consumption of the consumer load 11n will be shared only by the distribution system storage battery 8n. Therefore, in order to operate all of the distribution system storage batteries 8a to 8n in a coordinated manner, it is necessary to give the power converter 9 for each distribution system storage battery a drooping characteristic and to appropriately set the control target value of the interconnection point voltage (i.e., the voltage command value and power command value (or current command value) of the power converters 9a to 9n).

[0031] In the above-described DC microgrid, the power converter 9 manages the voltage at the interconnection point with the DC distribution system 21, thereby enabling management of the flow of power (current) through the DC distribution system 21. However, for power flow management, it is necessary to generate voltage command values ​​and power command values ​​for the power converter 9 of each distributed power source, taking into account not only the drooping characteristic of the power converter 9 of each distributed power source (distribution system storage battery 8), but also the voltage drop due to the distribution system impedances 7a to 7n (dominantly resistance components) of the DC distribution system 21. In this regard, while the power conversion device and DC power supply system of Patent Document 1 disclose that the converters have the drooping characteristic as described above, they do not sufficiently consider the flow of power.

[0032] Fig. 2 is a block diagram illustrating an example of the configuration of the CEMS 3 shown in Fig. 1. Referring to Fig. 2, the CEMS 3 includes a communication circuit 31, a memory circuit 32, a control parameter generation circuit 33, an operation plan creation circuit 34, a transmission data generation circuit 35, and a distributed power source management unit control circuit 36.

[0033] The communication circuit 31 sends measurement information to the DSO 2, receives control commands (24-hour demand plans) from the DSO 2, collects measurement data from communication terminals in the consumer load groups 10a to 10n (for example, smart meters (not shown) installed at each consumer), collects measurement data from the power converters 9a to 9n for the distribution system storage batteries and the AC / DC converter 6, and transmits command values ​​(voltage command values ​​and power command values) to the AC / DC converter 6 and the power converters 9a to 9n via the communication line 22. Hereinafter, the AC / DC converter 6 and the power converters 9a to 9n for the distribution system storage batteries will be collectively referred to as "each converter."

[0034] The memory circuitry 32 stores various information (measurement data, status information of each dispersed power source, etc.) obtained via the communication circuitry 31, various transmission data including command value information notified to each converter, and the drooping characteristics of each converter. The control parameter generation circuitry 33 determines the control mode of each converter (the definition of the control mode will be described later) and generates the drooping characteristics. As will be described later, in the first embodiment, the drooping characteristics include the inertia constant M, the damping coefficient Dg, the speed adjustment rate Kgd, and the governor time constant Tg.

[0035] The operation plan creation circuit 34 creates an operation plan for each converter (the AC / DC converter 6 and the power converters 9a to 9n) based on a control command (for example, a 24-hour demand plan) from the DSO 2. For example, in the first embodiment, an operation plan for 24 hours at 30-minute intervals is created. Furthermore, the operation plan creation circuit 34 determines whether the operation plan needs to be modified based on measurement information of each converter (the AC / DC converter 6 and the power converters 9a to 9n) collected at five-minute intervals, as well as SOC and SOH information of the distribution system storage batteries 8a to 8n. If the operation plan creation circuit 34 determines that a modification is necessary, it modifies the operation plan for the period until the next control command is notified from the DSO 2.

[0036] In the first embodiment, the AC / DC converter 6 and the power converters 9a to 9n for the distribution system storage batteries constitute one example of "one or more power converters having drooping characteristics." Furthermore, the AC / DC converter 6 corresponds to one example of "a power converter for interconnection." Furthermore, the function of the "drooping characteristics generation unit" can be realized by the control parameter generation circuit 33.

[0037] The transmission data generation circuit 35 generates transmission data (transmission packets) based on the drooping characteristic information (inertia constant M, damping coefficient Dg, speed adjustment rate Kgd, and governor time constant Tg) of each converter output from the control parameter generation circuit 33, the voltage command value and power command value of each converter output from the operation plan creation circuit 34, and the control output output from the distributed power source management unit control circuit 36.

[0038] The transmission data generated by the transmission data generation circuit 35 is transmitted via the communication circuit 31 based on a transmission command from the distributed power source management unit control circuit 36. The distributed power source management unit control circuit 36 ​​manages the operations of the communication circuit 31, the memory circuit 32, the control parameter generation circuit 33, the operation plan creation circuit 34, and the transmission data generation circuit 35 within the CEMS 3.

[0039] 2, the function of the "measurement data collection unit" can be realized by the communication circuit 31 and the memory circuit 32, and the function of the "command value creation unit" can be realized by the operation plan creation circuit 34. Furthermore, the function of the "command value output unit" can be realized by the transmission data generation circuit 35.

[0040] FIG. 3 is a block diagram illustrating an example of the configuration of the operation plan creation circuit 34 in the CEMS 3 shown in FIG.

[0041] Referring to Figure 3, the operation plan creation circuit 34 includes a battery operation plan creation circuit 341, a power generation amount prediction circuit 342, a power consumption prediction circuit 343, a battery operation plan correction circuit 344, an operation plan creation unit management circuit 346, a power flow current estimation circuit 347, a system voltage estimation circuit 348, a converter command value generation circuit 349, a system impedance estimation circuit 350, a power generation amount prediction database 351, and a power consumption prediction database 352.

[0042] The battery operation plan generation circuit 341 generates an operation plan (every 30 minutes, a 24-hour plan) for the power converters 9a to 9n for the distribution system battery based on the control command notified from the DSO2 (information regarding the planned value (every 30 minutes, a 24-hour plan) of the power (supply power) to be supplied from the substation 1 to the DC distribution system 21), the total value of the predicted results of the power generation of the PV panels 12 in each consumer load group 10 predicted by the power generation prediction circuit 342, and the total value of the power consumption prediction information in each consumer load group 10 predicted by the power consumption prediction circuit 343.

[0043] The power generation prediction circuit 342 obtains 24-hour weather forecast information from the weather forecast server 4 via the communication circuit 31, and predicts the total power generation value of the PV panels 12 in each consumer load group 10 based on the obtained weather forecast information, clock information (date, time) from the clock inside the CEMS 3 (not shown), and information from the power generation prediction database 351.

[0044] The power consumption prediction circuit 343 predicts the total power consumption by the consumer loads 11 in each consumer load group 10 connected to the DC distribution system 21 based on the above clock information (year, month, date, day of the week, time) and information from the power consumption prediction database 352.

[0045] The battery operation plan correction circuit 344 determines whether the operation plan generated by the battery operation plan generation circuit 341 needs to be modified, based on the grid interconnection point voltage information, output power information, drooping characteristic information, and voltage / power command value information related to the AC / DC converter 6 and the power converters 9 a to 9 n (each converter) for the distribution system storage battery, and the status information (SOC and SOH information) of the distribution system storage battery 8, all of which are collected via the communication circuit 31. If it is determined that the operation plan needs to be modified, the battery operation plan correction circuit 344 modifies the operation plan of each converter.

[0046] The operation plan creation unit management circuit 346 verifies the validity of the command values ​​by estimating the DC distribution system voltage using the power flow current estimation circuit 347 and the system voltage estimation circuit 348 based on the voltage command values ​​and power command values ​​of each converter generated by the battery operation plan generation circuit 341, the battery operation plan correction circuit 344, and the converter command value generation circuit 349. For example, if the estimated DC distribution system voltage is outside a predetermined voltage range (hereinafter also referred to as the "voltage control range (described later)"), the operation plan creation unit management circuit 346 instructs the battery operation plan generation circuit 341 (when creating the operation plan) or the battery operation plan correction circuit 344 to recreate (modify) the operation plan so as to generate command values ​​(voltage command value and power command value) again. Alternatively, if the actual voltage value (measured value) of the DC power distribution system voltage, rather than the estimated value, is outside the voltage control range, the regeneration (modification) of the operation plan may be instructed so that command values ​​(voltage command value and power command value) are generated again.

[0047] The power flow current estimation circuit 347 estimates the power flow current between each consumer load group 10 based on the control command and power command value notified from the DSO2, the power generation power prediction result of the PV panels 12 installed in each consumer load group 10 predicted by the power generation amount prediction circuit 342, and the power consumption prediction result of the consumer load in each consumer load group 10 predicted by the power consumption prediction circuit 343. The system voltage estimation circuit 348 estimates the interconnection point voltage with each converter on the DC distribution system 21 based on the power flow current estimation result output from the power flow current estimation circuit 347 and the distribution system impedance estimation result between each consumer load group 10 output from the system impedance estimation circuit 350.

[0048] The converter command value generation circuit 349 checks whether the interconnection point voltages of each converter with the DC power distribution system 21 output from the system voltage estimation circuit 348 are within a predetermined voltage control range, which will be described later, and if even one interconnection point voltage is outside the voltage control range, it reviews all command values. Note that if all interconnection point voltages are within the voltage control range, the converter command value generation circuit 349 notifies the operation plan creation unit management circuit 346 to that effect.

[0049] The system impedance estimation circuit 350 estimates the distribution system impedance 7 (7a to 7n) based on the measurement results of the voltage at the interconnection point of each converter with the DC distribution system 21, the current (DC) flowing through the DC distribution system 21, and the drooping characteristics of each converter, which are stored in the memory circuit 32. The operation plan creation unit management circuit 346 manages the operations of the power flow current estimation circuit 347, the system voltage estimation circuit 348, the converter command value generation circuit 349, the system impedance estimation circuit 350, the power generation amount prediction database 351, and the power consumption prediction database 352.

[0050] FIG. 4 is a block diagram of the control parameter generating circuit 33 in the CEMS 3 shown in FIG.

[0051] Referring to FIG. 4, the control parameter generating circuit 33 includes a drooping characteristic gradient determining circuit 331 and a control parameter determining circuit 332 .

[0052] In the first embodiment, the AC / DC converter 6 operates in a fixed voltage control mode to manage the DC distribution system voltage. On the other hand, the power converters 9a to 9n for the distribution system storage batteries are equipped with a power control mode in addition to the voltage control mode, and operate in one of the voltage control mode and the power control mode in accordance with instructions from the CEMS 3, depending on the configuration of the distribution system, etc. A detailed description of each control mode will be given later.

[0053] Drooping characteristic slope determination circuit 331 determines the slope of the drooping characteristic of each converter (AC / DC converter 6 and power converters 9a to 9n). In the first embodiment, power and voltage are converted into per unit (PU), and the slope is determined so that the slope of the PU-converted drooping characteristic is approximately the same between control modes.

[0054] The control parameter determination circuit 332 determines control parameters (the inertia constant M, the damping coefficient Dg, the speed adjustment rate Kgd, and the governor time constant Tg) based on the drooping characteristic gradient information output from the drooping characteristic gradient determination circuit 331 .

[0055] Fig. 5 is a block diagram illustrating an example configuration of AC / DC converter 6 shown in Fig. 1. Referring to Fig. 5, AC / DC converter 6 includes voltmeters 61a and 61b, ammeters 62a and 62b, a first AC / DC conversion circuit 63, a first control circuit 64, a first communication interface circuit 65, a voltmeter 66, and an ammeter 67.

[0056] The voltmeters 61a and 61b measure the AC voltage (AC system voltage) transmitted via the switch 5. The ammeters 62a and 62b measure the AC current from the switch 5. The first AC / DC conversion circuit 63 converts the AC voltage transmitted via the switch 5 into a first DC voltage. The first control circuit 64 controls the first AC / DC conversion circuit 63. The first communication interface circuit 65 communicates with the CEMS 3 and the like via the communication line 22. The voltmeter 66 measures the DC voltage (first DC voltage) output from the first AC / DC conversion circuit 63. The ammeter 67 measures the DC current output from the first AC / DC conversion circuit 63.

[0057] FIG. 6 is a block diagram illustrating an example of the configuration of the power converter 9 for the distribution system storage battery shown in FIG.

[0058] Referring to FIG. 6 , the power converter 9 for a distribution system battery includes a voltmeter 91, an ammeter 92, a first DC / DC conversion circuit 93, a second control circuit 94, a second communication interface circuit 95, a voltmeter 96, and an ammeter 97.

[0059] The voltmeter 91 measures a DC voltage (second DC voltage) corresponding to the output voltage of the distribution system battery 8. The ammeter 92 measures a DC current corresponding to the charge / discharge current of the distribution system battery 8. The first DC / DC conversion circuit 93 converts the second DC voltage of the distribution system battery 8 into a third DC voltage that is output to the DC distribution system 21. The second control circuit 94 controls the first DC / DC conversion circuit 93. The second communication interface circuit 95 communicates with the CEMS 3 and the like via the communication line 22. The voltmeter 96 measures the DC voltage of the DC distribution system 21 (third DC voltage). The ammeter 97 is an ammeter that measures a DC current between the first DC / DC conversion circuit 93 and the DC distribution system 21.

[0060] FIG. 7 is a block diagram illustrating an example of the configuration of the power converter 13 for the customer PV installed in the customer load group 10 shown in FIG.

[0061] Referring to Figure 7, the power converter 13 for the consumer PV includes a voltmeter 131, an ammeter 132, a second DC / DC conversion circuit 133, a third control circuit 134, a third communication interface circuit 135, a voltmeter 136, and an ammeter 137.

[0062] The voltmeter 131 measures the DC voltage (fourth DC voltage) output from the PV panel 12. The ammeter 132 measures the DC current output from the PV panel 12. The second DC / DC conversion circuit 133 converts the DC voltage (fourth DC voltage) output from the PV panel 12 into a fifth DC voltage that is output to the DC distribution system 21. The third control circuit 134 controls the second DC / DC conversion circuit 133. The third communication interface circuit 135 communicates with the CEMS 3 and the like via the communication line 22. The voltmeter 136 measures the DC voltage (fifth DC voltage) output from the second DC / DC conversion circuit 133. The ammeter 137 measures the DC current output from the second DC / DC conversion circuit 133.

[0063] FIG. 8 is a block diagram illustrating an example of the configuration of the first control circuit 64 that controls the first AC / DC conversion circuit 63 of the AC / DC converter 6 shown in FIG.

[0064] Referring to FIG. 8, the first control circuit 64 includes a current control circuit 640, a phase detection circuit 641, a first sine wave generation circuit 642, a fourth control circuit 647, a first power calculation circuit 681, and a first voltage target generation circuit 682.

[0065] The phase detection circuit 641 detects the frequency and phase of the AC system voltage using the measurement value of the AC system voltage measured by the voltmeter 61. The first sine wave generation circuit 642 generates a sine wave synchronized with the AC system voltage using the frequency and phase detection results output from the phase detection circuit 641 and voltage amplitude information of the AC system voltage output from the fourth control circuit 647. The generated sine wave is used for current control.

[0066] The current control circuit 640 has a subtractor 643 , a first PI (proportional integral) control circuit 644 , a multiplier 645 , a subtractor 646 , a second PI control circuit 648 , and a first PWM conversion circuit 649 .

[0067] The subtractor 643 subtracts the DC system voltage measured by the voltmeter 66 from the voltage target value of the DC power distribution system 21 output from the fourth control circuit 647. The voltage target value is a voltage target value generated by the first voltage target generation circuit 682 and output to the subtractor 643 via the fourth control circuit 647.

[0068] The first PI control circuit 644 performs PI control so that the output of the subtractor 643 becomes zero. The multiplier 645 multiplies the output of the first sine wave generating circuit 642 by the output of the first PI control circuit 644. The subtractor 646 subtracts the output of the ammeter 62 from the output of the multiplier 645.

[0069] The second PI control circuit 648 performs PI control so that the output of the subtractor 646 becomes zero. The first PWM conversion circuit 649 performs PWM modulation on the current command value output from the second PI control circuit 648 to generate a control command value for the first AC / DC conversion circuit 63.

[0070] The first power calculation circuit 681 calculates the output power of the AC / DC converter 6 from the output of the voltmeter 66 and the output of the ammeter 67. The first voltage target generation circuit 682 generates a voltage target value from the output of the first power calculation circuit 681 and the output of the voltmeter 66. As described above, the voltage target value is input to the subtractor 643 via the fourth control circuit 647. The first voltage target generation circuit 682 is configured to have a drooping characteristic, which will be described later.

[0071] The fourth control circuit 647 collects measurement results relating to the DC power distribution system 21 output from the voltmeter 66 and the ammeter 67, measurement results relating to the AC power distribution system 20 output from the voltmeters 61a, 61b and the ammeters 62a, 62b, and the voltage target value output from the first voltage target generation circuit 682, and notifies the information to the CEMS 3, etc. via the first communication interface circuit 65. The fourth control circuit 647 also stores various information notified from the CEMS 3 via the first communication interface circuit 65 (e.g., control parameters relating to the drooping characteristic, power command values, voltage command values, and control parameters of the first PI control circuit 644 and the second PI control circuit 648, etc.) in a register (not shown) and outputs the information to each circuit.

[0072] FIG. 9 is a block diagram illustrating an example of the configuration of the second control circuit 94 that controls the first DC / DC conversion circuit 93 of the power converter 9 for the distribution system storage battery shown in FIG.

[0073] Referring to FIG. 9, the second control circuit 94 has a second power calculation circuit 941, a second voltage target generation circuit 942, a power target generation circuit 943, a second voltage target value control circuit 945, a power target value control circuit 946, a first switching circuit 947, a current limiting circuit 948, and a fifth control circuit 949.

[0074] The second power calculation circuit 941 calculates the charge / discharge power of the distribution system storage battery 8 using the voltage measurement value of the DC distribution system 21 by the voltmeter 96 and the DC current measurement value by the ammeter 97. The second voltage target generation circuit 942 generates a voltage target value for the voltage control mode based on the output of the second power calculation circuit 941 and the output of the voltmeter 96. The second voltage target generation circuit 942 has a drooping characteristic when the power converter 9 for the distribution system storage battery operates in the voltage control mode.

[0075] The power target generating circuit 943 generates a power target value for the power control mode based on the output of the second power calculation circuit 941 and the output of the voltmeter 96. The power target generating circuit 943 has a drooping characteristic when the power converter 9 for the distribution system storage battery operates in the power control mode.

[0076] The second voltage target value control circuit 945 generates a current command value to be output to the first DC / DC conversion circuit 93 based on the voltage target value output from the second voltage target generation circuit 942. The power target value control circuit 946 generates a current command value to be output to the first DC / DC conversion circuit 93 based on the power target value output from the power target generation circuit 943.

[0077] The first switching circuit 947 selectively outputs one of the outputs (current command values) of the second voltage target value control circuit 945 and the power target value control circuit 946 in accordance with a control signal from the fifth control circuit 949. The current limiting circuit 948 limits the current command value output from the first switching circuit 947 and performs PWM modulation on the current command value after the limiting to generate a control command value for the first DC / DC conversion circuit 93.

[0078] The first switching circuit 947 is controlled so that when the control mode of the power converter 9 is the voltage control mode, it outputs the current command value generated by the second voltage target value control circuit 945, and when the control mode is the power control mode, it outputs the current command value generated by the power target value control circuit 946.

[0079] The fifth control circuit 949 collects measurement results relating to the output of the distribution system storage battery 8 and the DC distribution system 21, which are output from the voltmeters 91, 96 and the ammeters 92, 97, the voltage target value output from the second voltage target generation circuit 942, and the power target value output from the power target generation circuit 943, and notifies the information to the CEMS 3 and the like via the second communication interface circuit 95. The fifth control circuit 949 also stores various information (control parameters relating to drooping characteristics, power command values, voltage command values, control parameters of the second voltage target value control circuit 945 and the power target value control circuit 946, etc.) notified from the CEMS 3 via the second communication interface circuit 95 in a register (not shown), and outputs the information to each circuit.

[0080] FIG. 10 is a block diagram illustrating an example of the configuration of the third control circuit 134 that controls the second DC / DC conversion circuit 133 of the power converter 13 for the customer PV shown in FIG.

[0081] Referring to FIG. 10, the third control circuit 134 includes a maximum power point tracking (MPPT) control circuit 1341 , a PV voltage control circuit 1342 , a second switching circuit 1343 , and a sixth control circuit 1344 .

[0082] For so-called maximum power point tracking control, the MPPT control circuit 1341 searches for the maximum power point of the PV panel 12 for extracting the maximum amount of power from the PV panel 12, based on the measurement values ​​of the voltmeter 131 and the ammeter 132. Specifically, the MPPT control circuit 1341 generates a control command value for the second DC / DC conversion circuit 133 for controlling the DC voltage measured by the voltmeter 131 to a voltage corresponding to the maximum power point.

[0083] The PV voltage control circuit 1342 generates a control command value for the second DC / DC conversion circuit 133 based on the measurement value of the voltmeter 131, in order to maintain the DC voltage (fifth DC voltage) of the DC distribution system 21 at a predetermined target voltage.

[0084] The sixth control circuit 1344 outputs control parameters, control target values, etc. to the MPPT control circuit 1341 and the PV voltage control circuit 1342, and manages the power generation state, etc. of the PV panel 12. The sixth control circuit 1344 further outputs a control signal to the second switching circuit 1343.

[0085] The second switching circuit 1343 selectively outputs one of the outputs of the MPPT control circuit 1341 and the PV voltage control circuit 1342 (control command value of the second DC / DC conversion circuit 133) as the control command value of the third DC / DC conversion circuit 133 in accordance with a control signal from the sixth control circuit 1344.

[0086] The second DC / DC conversion circuit 133 is controlled in an MPPT mode or a PV voltage control mode. In the MPPT mode, the second switching circuit 1343 is controlled to output a control command value generated by the MPPT control circuit 1341, while in the PV voltage control mode, the second switching circuit 1343 is controlled to output a control command value generated by the PV voltage control circuit 1342.

[0087] Next, a description will be given of the drooping characteristic employed in embodiment 1. In embodiment 1, a DC / DC converter (power converter 9) or an AC / DC converter 6 installed in a DC power distribution system is provided with a virtual synchronous generator (VSG) control mechanism that applies the inertial force, synchronizing force, and braking force of a synchronous generator to an inverter device (static inverter) installed in an AC system.

[0088] First, a brief description will be given of the virtual synchronous generator control technique used in an inverter of an AC system.

[0089] Synchronous generators, typically used in thermal power plants, have several functions: a governor function that adjusts output power according to frequency, an inertial force that maintains angular velocity, a synchronizing force that synchronizes with AC grid voltage, an automatic voltage regulator (AVR) function that regulates the main grid voltage, and a function that allows continuous operation even during momentary drops in AC grid voltage that occur during grid faults and other events. Virtual synchronous generator control technology simulates the functions of a synchronous generator by controlling the transient response of a static inverter. Specifically, the inverter is controlled to simulate three functions: a governor function, a function that simulates a mass system model (dynamic characteristics of a rotating machine) based on an oscillation equation, and an AVR function.

[0090] In the first embodiment, a case will be described in which a governor function and a function simulating a mass system model based on an oscillation equation are implemented in order to provide an inertial force and a braking force to a DC power distribution system. The description will proceed assuming that an AVR function is not implemented in the first embodiment. The governor function and the function simulating a mass system model based on an oscillation equation will be specifically described below.

[0091] First, let us explain the governor function. A governor in a power plant controls the output power of a generator by adjusting the output of a gas turbine in a thermal power plant, a gas turbine in a nuclear power plant, or a steam turbine, or the guide vanes of a water turbine in a hydroelectric power plant. In an AC power system, when the demand for power exceeds the supply of power, the frequency of the AC system voltage drops. In thermal power generators and hydroelectric power generators that are capable of output control, the governor is given a droop characteristic, and is controlled to increase the generated power when the frequency drops.

[0092] On the other hand, when the power supply exceeds the power demand, the frequency of the AC grid voltage rises. Similarly, in thermal power generators and hydroelectric power generators that are capable of output control, the governor is given a droop characteristic, which controls the output so that the generated power decreases when the frequency rises. The Institute of Electrical Engineers of Japan (IEEJ) provides a standard model of a governor that operates in this way, including one configured as a first-order delay.

[0093] In the first embodiment, the operation of the governor is described when it is approximated by a model configured with the above-described first-order lag system. The transfer function GB(s) of the governor is shown in the following equation (1). In equation (1), -1 / Kgd represents the proportional gain of the governor (Kgd: speed adjustment rate), and Tg represents the time constant of the first-order lag system (Tg: governor time constant).

[0094] GB(s) = -1 / (Kgd × (1 + s × Tg)) (1) Next, we will explain the function of simulating a mass system model based on the oscillation equation. A synchronous generator has a generator rotor with an inertia constant M. For example, if the power generated by several hundred PV panels 12 suddenly decreases due to a sudden change in solar radiation, the governor control described above cannot instantaneously cover the power shortage. In this case, the synchronous generator converts the rotational energy stored in the generator rotor into electricity and outputs it to the grid. At that time, the angular velocity (number of rotations) of the generator rotor decreases. When the angular velocity of the generator rotor decreases, the energy supplied by the governor control increases, supporting the balance between supply and demand.

[0095] The following equation (2) shows an oscillation equation that simulates the mass system model of the generator rotor. The oscillation equation is expressed as an equation related to the amount of change in torque T obtained by dividing power P by angular velocity ω. In equation (2), Dg represents a damping coefficient, and M represents the inertia constant described above.

[0096] Tin-Tout=M×(dω / dt)+Dg×ω (2) In the first embodiment, the concept of equations (1) and (2) (i.e., the drooping characteristic) is used to control a DC / DC converter (power converter 9) or an AC / DC converter 6 installed in a DC power distribution system, and an example of control that simulates inertial forces and braking forces in the DC power distribution system will be described.

[0097] Here, a control example will be described in which a drooping characteristic is incorporated into the output control of the first DC / DC conversion circuit 93 of the power converter 9 and / or the first AC / DC conversion circuit 63 of the AC / DC converter 6, thereby simulating the inertial force, synchronizing force, and braking force of a synchronous generator with respect to the DC power distribution system 21. In the first embodiment, two types of control modes will be described: a voltage control mode that provides a power-voltage drooping characteristic (see FIG. 17 for details, which will be described later), and a power control mode that provides a voltage-power drooping characteristic (see FIG. 18 for details, which will be described later). As described above, the power converter 9 operates by selecting either the voltage control mode or the power control mode. On the other hand, the AC / DC converter 6 operates fixedly in the voltage control mode.

[0098] First, the first voltage target generation circuit 682 and the second voltage target generation circuit 942 that operate in a voltage control mode that provides a power-voltage drooping characteristic will be described with reference to FIGS. 11 to 13. FIG.

[0099] 11 is a block diagram illustrating an example configuration of the first voltage target generation circuit 682 (FIG. 8) and the second voltage target generation circuit 942 (FIG. 9). The first voltage target generation circuit 682 and the second voltage target generation circuit 942 can have the same configuration, so in FIG. 11, the configuration of the first voltage target generation circuit 682 is shown, and the configuration of the second voltage target generation circuit 942 is indicated by a reference symbol in parentheses.

[0100] Referring to FIG. 11, the first voltage target generation circuit 682 (second voltage target generation circuit 942) includes a subtractor 6821 (9421), a first governor control circuit 6822 (9422), an adder 6823 (9423), a subtractor 6824 (9424), and a first mass system calculation circuit 6825 (9425).

[0101] The subtractor 6821 (9421) subtracts the voltage command value (Vref1) from the CEMS 3, which is output from the fourth control circuit 647 (fifth control circuit 949), from the actual measurement result of the voltmeter 66 (96). The output of the subtractor 6821 (9421) is input to the first governor control circuit 6822 (9422). The detailed operation of the first governor control circuit 6822 (9422) will be described later.

[0102] The adder 6823 (9423) generates the control power target value of the first mass point system calculation circuit 6825 (9425) by adding the offset value output from the first governor control circuit 6822 (9422) and the power command value (Pref1) from CEMS3 output from the fourth control circuit 647 (fifth control circuit 949).

[0103] The subtractor 6824 (9424) subtracts the measured effective power output from the first power calculation circuit 681 (second power calculation circuit 941) from the control power target value output from the adder 6823 (9423). The output of the subtractor 6824 (9424) is input to the first mass point system calculation circuit 6825 (9425). As will be described in detail later, the first mass point system calculation circuit 6825 (9425) generates voltage target values ​​for the output of each converter, specifically, the first AC / DC conversion circuit 63 (first DC / DC conversion circuit 93), so that the output of the subtractor 6824 (9424) becomes zero, and outputs voltage target value information indicating the voltage target values.

[0104] In the first embodiment, the control parameters (speed adjustment rate Kgd, governor time constant Tg, inertia constant M, and braking coefficient Dg) of the first governor control circuit 6822 (9422) and the first mass system calculation circuit 6825 (9425) are notified via the fourth control circuit 647 (fifth control circuit 949) as numerical values ​​notified from CEMS3.

[0105] Fig. 12 is a block diagram illustrating an example of the configuration of the first governor control circuit 6822 (9422) shown in Fig. 11. Note that the configuration and operation of the first governor control circuit 9422 are the same as those of the first governor control circuit 6822, and therefore only the first governor control circuit 6822 will be described below.

[0106] 12, the first governor control circuit 6822 has a multiplier 68221, a first-order lag model (denoted as 1 / (1+s×Tg1) in the figure) 68222, and a first limiter circuit 68223.

[0107] The multiplier 68221 multiplies the output of the subtractor 6821 by the proportional gain (denoted as -1 / Kgd in the figure) output from the fourth control circuit 647. The output of the multiplier 68221 is input to the first-order lag model 68222. In the first embodiment, an example will be described in which the first-order lag standard model proposed by the Institute of Electrical Engineers of Japan is used for governor control. Therefore, the first-order lag model 68222 implements the first-order lag model (1 / (1+s×Tg1)) shown in FIG. 12. The output of the first-order lag model 68222 is subjected to limiter processing by the first limiter circuit 68223 and then output to the adder 6823 as shown in FIG. 11.

[0108] Fig. 13 is a block diagram illustrating an example of the configuration of the first mass point system calculation circuit 6825 (9425) shown in Fig. 11. Note that the configuration and operation of the first mass point system calculation circuit 9425 are the same as those of the first mass point system calculation circuit 6825, so only the first mass point system calculation circuit 6825 will be described below.

[0109] Referring to FIG. 13, the first mass system arithmetic circuit 6825 has a subtractor 68251 , an integrator (denoted as 1 / (M1×s) in the drawing) 68252 , a multiplier 68253 , and an adder 68254 .

[0110] Subtractor 68251 subtracts the output of multiplier 68253 from the output of subtractor 6824 ( FIG. 11 ) (i.e., the value obtained by subtracting the measured effective power from the control power target value). The subtraction result of subtractor 68251 is input to integrator 68252. Integrator 68252 calculates the differential voltage (ΔV) between the voltage target value and the voltage command value (Vref1) by multiplying the output of subtractor 68251 by (1 / M1) and integrating it. Then, adder 68254 adds the output of integrator 68252 and the voltage command value (Vref1) to generate a voltage target value, and outputs voltage target value information indicating this voltage target value.

[0111] The voltage target value information is output to a fourth control circuit 647 in the first control circuit 64 (FIG. 8) of the first AC / DC conversion circuit 63 and provided to a subtractor 643 (FIG. 8). On the other hand, the voltage target value information is provided to a second voltage target value control circuit 945 (FIG. 9) in the second control circuit 94 (FIG. 9) of the first DC / DC conversion circuit 93.

[0112] Here, the transfer function of the vibration equation part of the first mass system arithmetic circuit 6825 (9425) shown in FIG. 11 will be explained.

[0113] The transfer function G(s) of the oscillation equation can be expressed as a first-order lag system of proportional gain (1 / Dg_v) and time constant (M_v / Dg_v), as shown in the following equation (3).

[0114]

[0115] The mass system calculation unit time constant (M_v / Dg_v) in the virtual synchronous generator control used in equation (3) can be determined in accordance with the response speed required for the system. The relationship between the coefficients in the first voltage target generation circuit 682 or the second voltage target generation circuit 942 shown in Figures 11 to 13 and the coefficients in equation (3) is expressed as Tg1=Tg_v, Kgd1=Kgd_V, M1=M_v, and Dg1=Dg_v.

[0116] FIG. 47A shows a block diagram for calculating the transfer function F(s) of the first voltage target generation circuit 682 or the second voltage target generation circuit 942 shown in FIG.

[0117] Regarding the coefficients used in FIG. 47A, the relationship between the coefficients in the first voltage target generation circuit 682 or the second voltage target generation circuit 942 shown in FIGS. 11 to 13 and the coefficients in equation (3) is shown as Tg1=Tg_v, Kgd1=Kgd_V, M1=M_v, and Dg1=Dg_v.

[0118] Referring to Figure 47A, the transfer function F(s) = (ΔV / ΔP) with power change ΔP as input and voltage change ΔV as output is represented by the feedback connection of transfer functions F11(s) and F12(s) in Figure 47A, and can be expressed by equation (4).

[0119]

[0120] Therefore, according to the final value theorem, the relational expression of the voltage change amount ΔV relative to the power change amount ΔP in a steady state can be expressed by the following equation (5). (ΔV / ΔP) obtained from equation (5) corresponds to the slope of the drooping characteristic (1 / (Dg_v+1 / Kgd_v)) in virtual synchronous generator control.

[0121]

[0122] FIG. 48 is a block diagram illustrating the configuration of the second voltage target value control circuit 945 shown in FIG.

[0123] Referring to FIG. 48, the second voltage target value control circuit 945 has a subtractor 9451 and a third PI control circuit 9452 .

[0124] The subtractor 9451 subtracts the actual voltage measured by the voltmeter 96 from the voltage target value output from the second voltage target generation circuit 942. The output of the subtractor 9451 is input to a third PI control circuit 9452, and PI control is performed so that the output of the subtractor 9451 becomes zero. The output of the third PI control circuit 9452 (PI control calculation result) is output to the first switching circuit 947 as a control command value for the first DC / DC conversion circuit 93, as shown in FIG.

[0125] Next, the power target generating circuit 943 implemented in the second control circuit 94 in the power converter 9, which operates in a power control mode that provides a voltage-power drooping characteristic, will be described with reference to FIGS.

[0126] FIG. 14 is a block diagram illustrating an example of the configuration of the power target generating circuit 943 shown in FIG.

[0127] Referring to FIG. 14, the power target generating circuit 943 includes a subtractor 9431 , a second governor control circuit 9432 , an adder 9433 , a subtractor 9434 , and a second mass system calculation circuit 9435 .

[0128] The power command value (Pref2) output from the fifth control circuit 949 ( FIG. 9 ) is input to a subtractor 9431 and a second mass system calculation circuit 9435. The subtractor 9431 subtracts the power command value (Pref2) from the measured power calculation result output from the second power calculation circuit 941. The output of the subtractor 9431 is input to a second governor control circuit 9432. In the first embodiment, the second governor control circuit 9432 also uses a first-order lag system model such as that shown in the above-described equation (1), similar to the first governor control circuit 9422 ( FIG. 11 ).

[0129] 15 is a block diagram illustrating an example of the configuration of the second governor control circuit 9432. Referring to Fig. 15, the second governor control circuit 9432 has a multiplier 94321, a first-order lag model (denoted as 1 / (1+s×Tg2) in the figure) 94322, and a second limiter circuit 94323.

[0130] The multiplier 94321 multiplies the output of the subtractor 9431 by the proportional gain (denoted as -1 / Kgd2 in the figure) output from the fifth control circuit 949. The output of the multiplier 94321 is output to a first-order lag model 94322. As with the first-order lag model 68222 in FIG. 12, the first-order lag standard model proposed by the Institute of Electrical Engineers of Japan is also used for the first-order lag model 94322. The output of the first-order lag model 94322 is limited to a predetermined range by limiting processing by the second limiter circuit 94323, and then output from the second governor control circuit 9432 to the adder 9433 ( FIG. 14 ).

[0131] Returning to Fig. 14 , the output of the second governor control circuit 9432 is added by an adder 9433 to the voltage command value (Vref2) from the CEMS 3, which is output from the fifth control circuit 949. The output of the adder 9433 is input to a subtractor 9434. The subtractor 9434 subtracts the output (measured voltage) of the voltmeter 96 from the output of the adder 9433. The result of the subtraction by the subtractor 9434 is input to a second mass system calculation circuit 9435. In the first embodiment, the second mass system calculation circuit 9435 also uses the oscillation equation model shown in the above-mentioned equation (2), similar to the first mass system calculation circuit 9425 (Fig. 11).

[0132] Fig. 16 is a block diagram illustrating a configuration example of the second mass point system calculation circuit 9435. Referring to Fig. 16, the second mass point system calculation circuit 9435 has a subtractor 94351, an integrator (denoted as 1 / (M2 × s) in the drawing) 94352, a multiplier 94353, and an adder 94354.

[0133] The subtractor 94351 subtracts the output of the multiplier 94353 from the output of the subtractor 9434. The subtraction result of the subtractor 94351 is input to the integrator 94352. The integrator 94352 multiplies the output of the subtractor 94351 by (1 / M2) and integrates it. M2 is an inertia coefficient and is input from the fifth control circuit 949.

[0134] The output of the integrator 94352 is input to a multiplier 94353 and an adder 94354. The multiplier 94353 multiplies the output of the integrator 94352 by a damping coefficient (Dg2) output from the fifth control circuit 949. The output of the multiplier 94353 (the multiplication result) is input to a subtractor 94351. Meanwhile, the adder 94354 adds the output of the integrator 94352 to a power command value (Pref2) from the CEMS 3 to generate a power target value. Power target value information indicating the power target value is input from the second mass system calculation circuit 9435 to the power target value control circuit 946 and the fifth control circuit 949 as the output of the power target generation circuit 943, as shown in FIG. 9 . In the first embodiment, the power target value in the power control mode is generated by the power target generation circuit 943 in this manner.

[0135] FIG. 47B shows a block diagram for calculating the transfer function of the power target generating circuit 943, similar to FIG. 47A.

[0136] 47B , the transfer function F′(s)=(ΔP / ΔV), which takes a voltage change amount ΔV as an input and a power change amount ΔP as an output, is represented by the feedback connection of transfer functions F21(s) and F22(s) in FIG. 47B. By applying the final value theorem to the transfer function F′(s) calculated in the same manner as in FIG. 47A , the relationship between the voltage change amount ΔV and the power change amount ΔP in the steady state can be expressed by the following equation (6). The value (ΔP / ΔV) calculated from equation (6) corresponds to the slope of the drooping characteristic (1 / (Dg_p+1 / Kgd_v)).

[0137]

[0138] FIG. 49 is a block diagram illustrating an example of the configuration of the power target value control circuit 946 shown in FIG.

[0139] Referring to FIG. 49, the power target value control circuit 946 has a subtractor 9461 and a fourth PI control circuit 9462 .

[0140] The subtractor 9461 subtracts the actual power calculation result calculated by the second power calculation circuit 941 from the power target value output from the power target generation circuit 943. The output of the subtractor 9461 is input to a fourth PI control circuit 9462, and PI control is performed so that the output of the subtractor 9461 becomes zero. The output of the fourth PI control circuit 9462 (PI control calculation result) is output to the first switching circuit 947 as a control command value for the first DC / DC conversion circuit 93, as shown in FIG.

[0141] Next, an outline of the operation of the first embodiment will be described with reference to Fig. 17 to Fig. 21. Fig. 17 is a conceptual diagram showing an example of the drooping characteristics of the first voltage target generation circuit 682 or the second voltage target generation circuit 942.

[0142] An example of a power-voltage droop characteristic that defines a voltage change relative to a power change, used in the voltage control mode, is shown in Fig. 17. The droop characteristic shown in Fig. 17 corresponds to an example of a "first droop characteristic."

[0143] Fig. 18 is a conceptual diagram showing an example of the drooping characteristic of the power target generating circuit 943. Fig. 18 shows an example of a voltage-power drooping characteristic that defines a change in power relative to a change in voltage, used in the power control mode. The drooping characteristic shown in Fig. 18 corresponds to an example of a "second drooping characteristic."

[0144] As shown in FIGS. 17 and 18 , in the first embodiment, the drooping characteristics implemented in the AC / DC converter 6 and the power converter 9 are converted into PU by dividing the output power of each converter by the capacity of that converter, and are also converted into PU by dividing the DC voltage output by each converter by the reference voltage of the DC power distribution system (for example, 1500 V), and are set so that the slope of the PU-converted drooping characteristics is equivalent between the voltage control mode and the power control mode.

[0145] In FIGS. 17 and 18 , Pmax denotes the converter capacity on the discharging side and indicates the maximum discharge power. Similarly, Pmin denotes the converter capacity on the charging side and indicates the maximum charge power. Furthermore, Vmax and Vmin respectively denote the maximum and minimum values ​​of the appropriate voltage range of the DC distribution system. For example, in the first embodiment, the appropriate voltage range of the DC distribution system is set to within ±10% (e.g., 1350 V to 1650 V) of the reference voltage of the DC distribution system (e.g., 1500 V). Furthermore, Vrange_max and Vrange_min in FIGS. 17 and 18 denote the upper and lower limits, respectively, of a predetermined voltage control range corresponding to the “predetermined voltage range” of the interconnection point voltage. As described above, to ensure a margin for load fluctuations and the like, Vrange_max<Vmax and Vrange_min>Vmin are set.

[0146] FIG. 19 is a conceptual diagram for explaining the operation principle of the management device for the power converter according to the first embodiment.

[0147] In the example of Fig. 19, four (n = 4) consumer load groups 10a to 10d and power converters 9a to 9d for distribution system storage batteries are connected to a DC distribution system 21. Here, when the consumer load groups 10a to 10d are the same, conventional control does not take into account the power flow or the distribution system impedances 7a to 7d of the DC distribution system 21, and therefore the same voltage command value (Vref) and power command value (Pref) are commonly notified to the power converters 9a to 9d. Note that, for simplicity of explanation, the power flow in the example of Fig. 19 is assumed to be forward (current (power) flows from the AC / DC converter 6 to the consumer load group 10d).

[0148] At the bottom of FIG. 19, the vertical axis shows the voltages at the interconnection points of the power converters 9a to 9d with the DC power distribution system 21 at the installation positions of the power converters 9a to 9d for the distribution system storage batteries shown on the horizontal axis.

[0149] 19, in conventional control (for example, Patent Document 1) plotted by the dotted line, power flow and distribution system impedances 7a to 7d are not taken into consideration, and therefore, due to a voltage drop caused by power flow, the voltage at the interconnection point of power converters 9a to 9d with DC distribution system 21 drops below output voltage Vdc_0 (for example, 1500 V) of the AC / DC converter. As a result, each power converter 9 determines that there is a power shortage in DC distribution system 21 and increases the discharge power from each distribution system storage battery 8 based on the drooping characteristic.

[0150] As a result, in the example of Figure 19, power converters 9c and 9d are outside the predetermined voltage control range (Vrange_max to Vrange_min in Figures 17 and 18) of the DC distribution system due to the voltage drop caused by the power flow. As described above, with conventional control, in cases where the distribution system impedance 7 of DC distribution system 21 or the like cannot be ignored, there is a risk that the voltage of the DC distribution system cannot be maintained within the voltage control range due to the voltage drop caused by the power flow, even if the AC / DC converter 6 and the power converter 9 are given drooping characteristics. In addition, there is a concern that the voltage drop caused by the power flow will cause the discharge power of a certain distribution system storage battery 8 located further downstream in the current direction of the power flow to become larger, making it difficult for the CEMS 3 to manage the state of charge (SOC) of each distribution system storage battery 8.

[0151] In contrast, in the first embodiment, a power command value (Pref) is created as described below. Note that, although details will be described later, in the first embodiment, when the CEMS 3 creates the power command values ​​(Pref) for the AC / DC converter 6 and the power converters 9a to 9n, the CEMS 3 generates the power command values ​​by using an operation plan creation circuit 34 shown in Fig. 2 to reflect the supply and demand plan notified from the DSO 2, the supply and demand forecast results for the consumer load groups 10a to 10n (predicted from the predicted power generation amount of the PV panel 12 and the predicted power consumption results of the consumer load 11), and the SOC information of the distribution system storage batteries 8a to 8n.

[0152] Then, the CEMS 3 predicts the power flow (current direction) of the DC distribution system 21 using the calculated power command values ​​of the AC / DC converter 6 and the power converters 9a to 9n, the drooping characteristics of the AC / DC converter 6 and the power converters 9a to 9n, and the above-mentioned supply and demand prediction.

[0153] Furthermore, the CEMS 3 estimates in advance the impedance of the DC distribution system 21 based on the measurement results of voltage and current notified from the AC / DC converter 6, the consumer load groups 10a to 10n, and the power converters 9a to 9n. Then, based on the estimated impedance information (distribution system impedances 7a to 7n) and the power flow prediction results, the CEMS 3 estimates the interconnection point voltage of each power converter 9 with the DC distribution system 21, and checks whether the estimated interconnection point voltage is within the voltage control range (Vrange_max to Vrange_min).

[0154] If any of the estimated interconnection point voltages is not within the voltage control range (Vrange_max to Vrange_min), the power command values ​​(Pref) of all the power converters 9 are created (corrected) again.

[0155] 19, the voltage at the interconnection point between power converters 9c and 9d and DC distribution system 21 deviates from the voltage control range (Vrange_max to Vrange_min). This is due to the voltage drop caused by the distribution system impedance 7 described above. First, the voltage at the interconnection point between power converter 9a and the DC distribution system becomes lower than the reference voltage of the distribution system (1500 V in the first embodiment) due to the voltage drop caused by distribution system impedance 7a.

[0156] On the other hand, because power converter 9a has a drooping characteristic (see FIGS. 17 and 18), the output power (discharge power) of power converter 9a becomes larger than the power command value (Pref) from the CEMS 3. Similarly, due to a similar drooping characteristic, the discharge power from power converters 9b to 9d also becomes larger than the power command value (Pref) from the CEMS 3. Note that in an actual DC distribution system 21, as the discharge power from each power converter 9 increases, the forward current power from AC / DC converter 6 decreases.

[0157] Next, the re-creation (modification) of the above-mentioned power command value (Pref) will be described. Hereinafter, the power command value Pref, the DC voltage Vdc at the interconnection point, and the DC current Idc corresponding to each of the power converters 9a to 9n will be denoted as Pref_x, Vdc_x, and Idc_x using the same subscripts as those of the power converter 9x (9a to 9n).

[0158] 19 , a DC current Idc_0 is output as a power flow current, and a DC voltage Vdc_0 equivalent to a reference voltage (1500 V) is output from the AC / DC converter 6. The voltage drop due to the distribution system impedance 7a (impedance value R_a) is R_a×Idc_0, so the voltage Vdc_a at the interconnection point between the power converter 9a and the DC distribution system is Vdc_a=(Vdc_0−R_a×Idc_0).

[0159] Here, in the first embodiment, based on the drooping characteristics of the power converter 9a, when the interconnection point voltage with the DC distribution system is Vdc_a, a power command value (Pref_a') is generated so that the power command value (Pref_a: power command value of the power converter 9a) becomes the initial (previous if executed multiple times) power command value (Pref_a: power command value of the power converter 9a). When the generation of the power command value (Pref_a') for the power converter 9a is completed, the CEMS 3 calculates the DC current I_a (I_a = (P_cm_P_a - P_pv_P_a - Pref_a) / Vdc_a) flowing from the power converter 9a to the consumer load group 10a using the power generation amount (P_pv_P_a) of the PV panel 12a and the power consumption prediction result (P_cm_P_a) of the consumer load group 10a.

[0160] When the re-creation of the power command value for the power converter 9 a for the distribution system storage battery is completed, the CEMS 3 calculates the DC current Idc_a (Idc_a = Idc_0 - I_a) flowing through the distribution system impedance 7 b, and based on the calculation result, calculates the voltage drop (= R_b × Idc_a) due to the distribution system impedance 7 b (impedance value R_b). Due to this voltage drop, the interconnection point voltage Vdc_b of the power converter 9 b with the DC distribution system 21 becomes Vdc_b = (Vdc_a - R_b × Idc_a).

[0161] Here, as in the case of power converter 9a, a power command value (Pref_b') is generated based on the drooping characteristics of power converter 9b so that the power command value (Pref_b: power command value of power converter 9b) becomes the first (previous if executed multiple times) power command value when the interconnection point voltage is Vdc_b. When the generation of the power command value (Pref_b') for power converter 9b is completed, CEMS 3 calculates a DC current I_b (DC current I_b = (P_cm_P_b - P_pv_P_b - Pref_b) / Vdc_b) flowing from power converter 9b to consumer load group 10b using the power generation amount prediction result (P_pv_P_b) of PV panel 12b and the power consumption prediction result (P_cm_P_b) of consumer load group 10b.

[0162] Thereafter, the CEMS 3 performs the same operation for each consumer load group 10 (power converter 9) up to the consumer load group 10 at the end of the DC distribution system 21 (consumer load group 10d in the example of Figure 19).

[0163] When the re-creation of the power command value (Pref') is completed up to the consumer load group 10 at the end of the DC distribution system 21 (consumer load group 10d in FIG. 19), the CEMS 3 checks whether the estimated interconnection point voltages (Vdc_a to Vdc_d) of each power converter 9 with the DC distribution system are within the voltage control range (Vrang_max to Vrang_min). If any of them is not within the voltage control range, the original power command values ​​(Pref_a' to Pref_d') are reviewed.

[0164] 19, the operation of correcting (recreating) the power command values ​​is repeated until all of the estimated interconnection point voltages (Vdc_a to Vdc_d) are within the voltage control range (Vrang_max to Vrang_min), accompanied by review of the power command values ​​so as to increase the discharge power of power converters 9a to 9d so as to reduce the power flow through DC distribution system 21. At the bottom of Fig. 19, the interconnection point voltages of each power converter 9 with the DC distribution system after review of the power command values ​​are plotted as a solid line labeled "present application (with control)."

[0165] In the first embodiment, a control example in which the power command value (Pref) is reviewed (modified or recreated) has been described, but as will be described in detail in subsequent embodiments, the same effect can also be obtained by reviewing the voltage command value (Vref) output to each power converter 9 (described in the second embodiment), or by reviewing both the power command value (Pref) and the voltage command value (Vref) (described in the third embodiment).

[0166] Next, the operation of the power converter management device according to the first embodiment will be described with reference to Figures 1 to 35. Referring again to Figure 1, the power distribution system to which the power converter management device according to the first embodiment is connected will be described.

[0167] In the first embodiment, an AC distribution system 20 connected to a main system (not shown) via a substation 1 is connected to an AC / DC converter 6 via a switch 5. The AC / DC converter 6 converts a three-phase AC voltage input from an AC distribution system 20b into a DC voltage and outputs the DC voltage to a DC distribution system 21.

[0168] The DC voltage output from the AC / DC converter 6 is input to a DC distribution system 21a connected to the power converter 9a, the consumer load group 10a, and the distribution system impedance 7b via a distribution system impedance 7a. As described above, each consumer load group 10 includes a consumer load 11 and a consumer PV power converter 13. In the first embodiment, the consumer loads 11 are connected to a plurality of consumers (e.g., approximately 10 to 50 general consumers (detached houses)), and the consumer PV power converter 13 is installed for each PV panel of the plurality of consumers in the consumer load group 10 and connected to the DC distribution system 21.

[0169] In embodiment 1, as shown in Figure 1, the DC distribution system 21 is configured by connecting n sets of distribution system impedances 7, power converters 9 for distribution system storage batteries, and consumer load groups 10 in series.

[0170] Furthermore, the distribution automation system (DSO 2), the CEMS 3, the weather forecast server 4, the power converters 9a to 9n for the distribution system storage batteries, the consumer loads 11a to 11n in the consumer load group 10, and the power converters 13a to 13n for the consumer PV are connected to one another via a communication line 22. It should be noted that the multiple consumers constituting the consumer load 11 are also connected to the communication line 22 via a smart meter or the like (not shown). Furthermore, in the first embodiment, the power converters 9a to 9n for the distribution system storage batteries are equipped with at least one of a second voltage target generation circuit 942 and a power target generation circuit 943, thereby applying a pseudo-inertial force to the DC distribution system 21.

[0171] Here, we will explain the operation of the system that supports the DC distribution system 21 using power supplied from the substation 1, power generated by the PV panels 12a to 12n, and charging / discharging power input / output from the distribution system storage batteries 8a to 8n.

[0172] FIG. 22 shows a sequence diagram of normal operation of the power converter management device (CEMS 3) centered around the CEMS 3 shown in FIG.

[0173] As shown in Figure 22, steady-state processing during normal operation consists of two processes: a first process performed every 30 minutes and a second process performed every 5 minutes. Note that the processing periods of the first and second processes are not limited to 30 minutes and 5 minutes, respectively. For example, the first processes may be performed every hour or 15 minutes, and the second processes may be performed every 1 minute or 30 seconds. However, the second process may be performed every shorter period than the first process.

[0174] 22 , when the first process (30-minute cycle process) is started, the DSO 2 outputs an output request for collected measurement data to the CEMS 3 via the communication line 22. Upon receiving the output request from the DSO 2, the CEMS 3 transmits output requests for measurement data, etc. to each connected device, such as the AC / DC converter 6, the power converters 9 a to 9 n, and the consumer load groups 10 a to 10 n, for collecting measurement data and status information (such as the SOC and SOH of the distribution system storage battery 8), and executes collection of the measurement data, etc.

[0175] Furthermore, the CEMS3 calculates the amount of power consumed by each consumer load group 10, the amount of power generated by the PV panel 12, and the amount of power charged and discharged by the distribution system storage battery 8 for 30 minutes, in combination with the 25 minutes of data collected in the second processing (5 minutes period) following the previous first processing (30 minutes period), and transmits this to the DSO2 together with information such as the SOC and SOH of the distribution system storage battery 8 as measurement data for the output request.

[0176] When the DSO 2 receives measurement data and the like (measurement results) from the CEMS 3, it creates a 24-hour demand plan at 30-minute intervals, which is necessary to create an operation plan for the distribution system storage batteries 8a to 8n, and notifies the CEMS 3 of the created plan. The demand plan includes information on the total supply power to be supplied to the AC distribution system 20 (DC distribution system 21) via the substation 1 for 30 minutes.

[0177] Upon receiving the demand plan information from the DSO 2, the CEMS 3 creates an operation plan (power command value (Pref) and voltage command value (Vref)) and control parameters, etc. for the distribution system storage battery 8 based on the collected SOC information, SOH information, power generation forecast information (details will be described later) for the PV panels 12 a to 12 n, and demand forecast information (details will be described later) for the consumer load group 10. Details of the method for creating the operation plan and control parameters will be described later.

[0178] When the CEMS 3 completes creating the operation plan and control parameters for the distribution system storage battery 8, it transmits the operation plan and control parameters to the AC / DC converter 6 and the power converters 9a to 9n, and ends the first process (30-minute periodic process).

[0179] Furthermore, in the second process with a 5-minute cycle, the CEMS 3 collects measurement data from the AC / DC converter 6, the power converters 9a to 9n, and the consumer load groups 10a to 10n. Then, based on the collected data, the CEMS 3 checks the difference between the power command value (Pref) and the actual charge / discharge power, as well as the actually measured voltage of the DC distribution system 21, and determines whether or not the operation plan needs to be modified.

[0180] In the first embodiment, the CEMS 3 modifies and recalculates the operation plan (power target value (command value)) when (1) the difference between the power command value (Pref) and the actual measured power value is outside a predetermined range, (2) the measured voltage of the DC distribution system 21 is outside the voltage control range (Vrange_max to Vrange_min), or (3) the SOC of the distribution system storage battery 8 rises above a predetermined upper limit (overcharging) or falls below a predetermined lower limit (overdischarging). The CEMS 3 notifies the AC / DC converter 6 and each power converter 9 (for the distribution system storage battery) of the recalculation result corresponding to the modified operation plan. The specific content of this recalculation process will be described later.

[0181] Next, a detailed operation of the CEMS 3 will be described with reference to Fig. 23. Fig. 23 is a flowchart illustrating a control process of the CEMS 3 shown in Fig. 1 as a management device for the power converter according to the first embodiment.

[0182] 23 , when processing is started, the operation plan creation circuit 34 of the CEMS 3 checks in step (hereinafter simply referred to as “S”) 101 whether or not an output request for measurement data, etc. has been received from the DSO 2. If an output request has been received (YES in S101), in S102, an output request for measurement data is transmitted via the communication line 22 to the AC / DC converter 6, the power converters 9 a to 9 n for the distribution system storage batteries, and the consumer load groups 10 a to 10 n, and the latest measurement data, etc. are collected. The collected measurement data, etc. is temporarily stored in the memory circuit 32 via the communication circuit 31.

[0183] In S102, the collected measurement data, etc. are used to update the power generation prediction database 351 for the PV panels 12a to 12n and the power consumption prediction database 352 for the consumer loads 11a to 11n (FIG. 3) in the operation plan creation circuit 34 described in FIG. 3.

[0184] Then, in S103, the operation plan creation circuit 34 combines the latest measurement data, etc. collected in S102 with the 25-minute data collected in the 5-minute cycle before S102, which is stored in the memory circuit 32, to calculate the amount of power generated by each consumer load group (the amount of power consumed by each consumer) 10a to 10n, the PV panels 12a to 12n, and the amount of charge / discharge power of the distribution system storage batteries 8a to 8n for 30 minutes, and transmits this, along with information such as the SOC and SOH of the distribution system storage batteries 8a to 8n, to the DSO 2 via the communication circuit 31 as measurement data, etc., in response to an output request. In the first embodiment, when the CEMS 3 completes transmitting the measurement data, etc. (S103), the memory circuit 32 erases the measurement data, etc. collected over the 30 minutes.

[0185] After transmitting the measurement data in S103, or when the determination result in S101 is NO, the operation plan creation circuit 34 checks in S104 whether or not the above-mentioned demand plan has been received from the DSO 2. If the demand plan has been received (when the determination result in S104 is YES), an operation plan for the distribution system storage battery 8 is created in S105 (operation plan creation 1). Note that in the first embodiment, the DSO 2 notifies the CEMS 3 of a supply and demand plan for power supplied from the trunk system to the DC distribution system 21 for 24 hours at 30-minute intervals.

[0186] FIG. 24 shows a flowchart illustrating details of the control process of S105 (operation plan creation 1) in FIG.

[0187] As shown in FIG. 24, when the process of operation plan creation 1 (S105) is started, the CEMS 3 (operation plan creation circuit 34) executes power generation amount prediction of the PV panels 12a to 12n in S1051.

[0188] 2 and 3 again, upon receiving the demand plan notification from the DSO 2, the distributed power source management unit control circuit 36 ​​instructs the operation plan creation unit management circuit 346 in the operation plan creation circuit 34 to create an operation plan. Upon receiving the instruction, the operation plan creation unit management circuit 346 instructs the power generation amount prediction circuit 342 via the battery operation plan generation circuit 341 to predict the power generation amount of the PV panels 12 a to 12 n.

[0189] Upon receiving the instruction, the power generation amount prediction circuit 342 obtains a 24-hour weather forecast from the weather forecast server 4 via the communication line 22, and predicts the amount of power generated by the PV panels 12a to 12n for 24 hours using the obtained weather forecast (weather forecast information) and data in the power generation amount prediction database 351 managed by the power generation amount prediction circuit 342. Specifically, the amount of power generated by each of the PV panels 12a to 12n is predicted using time information (not shown) and the weather forecast information from the weather forecast server 4. In the first embodiment, the DSO 2 notifies the DC power distribution system 21 of a supply and demand plan for 24 hours at 30-minute intervals. Therefore, the power generation amount prediction database 351 is constructed based on the actual power generation amounts of the PV panels 12a to 12n, actual weather information, and time information (year, month, date, and time information) collected over a 30-minute period. The details of the method for constructing the power generation amount prediction database 351 are not relevant to the main points of this disclosure, and therefore will not be described here.

[0190] Referring again to FIG. 24, when the CEMS 3 has finished predicting the power generation amounts of the PV panels 12a to 12n in S1051, it predicts the power consumption of the consumer loads 11a to 11n in S1052.

[0191] Returning to Figure 3, when the operation plan creation unit management circuit 346 receives the power generation prediction results of the PV panels 12a to 12n from the power generation prediction circuit 342, it instructs the power consumption prediction circuit 343 via the battery operation plan generation circuit 341 to predict the power consumption of the consumer loads 11a to 11n.

[0192] Upon receiving the instruction, the power consumption prediction circuit 343 predicts the power consumption of the consumer loads 11a to 11n for 24 hours using data in the power consumption prediction database 352 managed by the power consumption prediction circuit 343. Note that, like the power generation amount prediction database 351, the power consumption prediction database 352 is constructed based on the power consumption of the consumer loads 11a to 11n collected over a 30-minute period, date, time information, and weather information. Note that the details of how the power consumption prediction database 352 is constructed are not relevant to the main points of this disclosure, and therefore will not be described here.

[0193] Referring again to FIG. 24, when the CEMS 3 finishes predicting the power consumption of the consumer load groups 10a to 10n in S1052, it starts creating a demand plan in S1053.

[0194] 3 , upon receiving the predicted results of the power consumption of the consumer loads 11 a to 11 n from the power consumption prediction circuit 343, the battery operation plan generation circuit 341 in the operation plan creation circuit 34 calculates the total value of the charging and discharging power of the distribution system storage batteries 8 a to 8 n every 30 minutes. This total value is calculated based on the predicted results of the power generation amount of the PV panels 12 a to 12 n from the power generation amount prediction circuit 342, the predicted results of the power consumption of the consumer loads 11 a to 11 n from the power consumption prediction circuit 343, and the demand plan notified from the DSO 2. As described above, in the first embodiment, the demand plan corresponds to a 24-hour power supply plan every 30 minutes that is planned for the DC distribution system 21 below the substation 1.

[0195] Referring to Figure 24, when the CEMS 3 finishes creating the demand plan in S1053, it formulates the charge / discharge power (equivalent to the power command value of each power converter 9) of the distribution system storage batteries 8a to 8n in S1054 (distribution system storage battery charge / discharge power formulation 1).

[0196] 2 and 3 , the operation plan creation circuit 34 acquires, via the communication circuit 31, the SOC information of the distribution system batteries 8 a to 8 n and the battery capacities of the distribution system batteries 8 a to 8 n collected in the memory circuit 32, and determines (pro-rataly allocates) the charge / discharge power of the distribution system batteries 8 a to 8 n every 30 minutes. In the first embodiment, when creating a 24-hour operation plan for the batteries, the operation plan is created so that the SOCs of the distribution system batteries 8 a to 8 n are zero at almost the same time, are fully charged at almost the same time, or all of the distribution system batteries 8 are still able to be charged / discharged 24 hours later. This is for the following reason.

[0197] For example, when the charging power of the distribution system storage batteries 8a and 8b becomes zero, consumer loads 11a and 11b in consumer load groups 10a and 10b are supplied with power generated by PV panels 12a and 12b and power supplied from DC distribution system 21. In this case, other distribution system storage batteries 8c to 8n operate to supply the power shortage in consumer load groups 10c to 10n, and as a result, power from AC / DC converter 6 is supplied to consumer load groups 10a and 10b.

[0198] As a result, the power (i.e., DC currents Idc_a and Idc_b) supplied from the DC distribution system 21 to the consumer load groups 10a and 10b increases, resulting in a larger voltage drop across the distribution system impedances 7a and 7b. As a result, the voltage at the interconnection points of the distribution system batteries 8a to 8n with the DC distribution system 21 decreases, resulting in a case where the voltage falls outside the predetermined voltage control range. On the other hand, when the distribution system batteries 8a to 8n are operating (discharging), each distribution system battery 8 compensates for the decrease in power generated by the PV panel 12 in each consumer load group 10, so the power supply from the AC / DC converter 6 does not increase to compensate. This prevents the voltage at the interconnection points of the power converters 9a to 9n with the DC distribution system 21 from decreasing as described above, resulting in a case where the voltage falls outside the voltage control range.

[0199] For this reason, when creating an operation plan for the distribution system storage batteries 8a to 8n using the CEMS 3, it is understood that it is desirable to create an operation plan so that the charge states of the distribution system storage batteries 8a to 8n are aligned and the SOCs reach zero or are fully charged at almost the same time, as described above.

[0200] Next, the control process of S1054 (distribution system battery charge / discharge power planning 1) in FIG. 24 will be described in detail with further reference to the flowchart in FIG.

[0201] 25 and 3, when the flow (S1054) for formulating distribution system battery charge / discharge power (power command value) 1 is started, the operation plan creation unit management circuit 346 (FIG. 3) in the operation plan creation circuit 34 instructs the battery operation plan generation circuit 341 (FIG. 3) to generate power command values ​​for the power converters 9a to 9n. In S10541, in response to the operation plan creation instruction from the operation plan creation unit management circuit 346, the battery operation plan generation circuit 341 instructs the power generation amount prediction circuit 342 (FIG. 3) and the power consumption prediction circuit 343 (FIG. 3) to predict the amount of power generated by the PV panels 12a to 12n in the consumer load groups 10a to 10n and the amount of power consumed by the loads.

[0202] When the power generation amount prediction circuit 342 receives an instruction to predict the power generation amounts of the PV panels 12a to 12n from the battery operation plan generation circuit 341, the power generation amount prediction circuit 342 predicts the power generation amounts of the PV panels 12a to 12n using a power generation amount prediction database 351 based on the weather forecast information received from the weather forecast server 4 via the memory circuit 32 and the date and time information and day of the week information from a time information generation unit (not shown) within the operation plan creation circuit 34. Although not described in detail, the power generation amount prediction database 351 calculates the power generation amount for 30 minutes of each PV panel 12 collected in the 5-minute period processing (second processing in FIG. 22 ) and the 30-minute period processing (first processing in FIG. 22 ), and can update the data in the power generation amount prediction database 351 based on the calculation results of the power generation amount, date and time information, day of the week information, and actual weather information.

[0203] Similarly, when the power consumption prediction circuit 343 receives an instruction from the battery operation plan generation circuit 341 to execute a power consumption prediction for the consumer loads 11a to 11n in the consumer load group 10a to 10n, the power consumption prediction circuit 343 predicts the power consumption of each consumer load 11 using the power consumption prediction database 352 based on the weather forecast information (including temperature information) received from the weather forecast server 4 and the date and time information and day of the week information output from a time information generation unit (not shown) in the operation plan creation circuit 34, which are transmitted from the memory circuit 32. Note that, although not described in detail, the power consumption prediction database 352 calculates the 30-minute power consumption of each consumer load 11 collected in the 5-minute periodic processing (second processing in FIG. 22 ) and the 30-minute periodic processing (first processing in FIG. 22 ), and can update the data in the power consumption prediction database 352 based on the power consumption calculation results, date and time information, day of the week information, and actual weather information.

[0204] When S10541 is completed, the battery operation plan generation circuit 341 collects status information (SOC information in the first embodiment) of the distribution system batteries 8 a to 8 n in S10542. When S10542 is completed, the battery operation plan generation circuit 341 calculates the demand (difference) power of each consumer load group 10 from the power generation amount prediction results of each PV panel 12 and the power consumption prediction results of the consumer load 11 collected in S10541 in S10543.

[0205] When S10543 is completed, the battery operation plan generation circuit 341 allocates the demand power from the AC / DC converter 6 (demand plan notified from the DSO2) to each consumer load group 10 in S10544 based on the SOC and battery capacity information of the distribution system battery 8, and the converter capacity information of the power converter 9.

[0206] For example, in the first embodiment, in S10544, the demand power from the AC / DC converter 6 is allocated based on the power difference (surplus / deficiency) calculated in S10543 and the SOC information of the distribution system storage batteries 8 so that the SOCs of the distribution system storage batteries 8 after 30 minutes are approximately the same. Specifically, the power surplus / deficiency in the consumer load group 10 is calculated as "(the predicted power consumption of the consumer load 11) - (the predicted power generation amount of the PV panel 12)", and at that time, the supply power planned in the supply and demand plan notified by the DSO 2 can be allocated according to the magnitude of the SOC of the distribution system storage batteries 8. At that time, a power command value (Pref) for the AC / DC converter 6 is also generated. Specifically, the supply power planned in the supply and demand plan notified by the DSO 2 can be set as is as the power command value (Pref) for the AC / DC converter 6.

[0207] When S10544 is completed, in S10545 the battery operation plan generation circuit 341 creates a power command value to be notified to each power converter 9. Specifically, the power command value is calculated by subtracting the power demand allocated in S10544 from the power difference (surplus or shortage) calculated in S10543.

[0208] In S10546, the battery operation plan generation circuit 341 checks whether the charge / discharge power (power command value) calculated in S10545 exceeds the capacity of the first DC / DC conversion circuit 93 in the power converter 9. If it exceeds the capacity (NO in S10546), the process returns to S10544, where the demand power from the AC / DC converter 6 is reallocated. On the other hand, if it does not exceed the capacity (YES in S10546), the process proceeds to S10547, where it is checked whether the charge / discharge power (i.e., power command value (Pref)) of all power converters 9 (DC / DC converters for distribution system batteries) has been calculated.

[0209] If the charge / discharge power of all power converters 9 has not been calculated (NO in S10547), the process returns to S10545 to generate a power command value (Pref) for the next power converter 9. On the other hand, if the charge / discharge power of all power converters 9 has been calculated (YES in S10547), the battery operation plan generation circuit 341 notifies the operation plan creation unit management circuit 346 of this fact and ends the process of S1054 (distribution system battery charge / discharge power planning 1).

[0210] 24 again, when the operation plan creation unit management circuit 346 in the operation plan creation circuit 34 is notified of the completion of S1054, in S1055 it instructs the power flow current estimation circuit 347 to calculate the power flow current of the DC distribution system 21. Upon receiving the instruction to calculate the power flow current, the power flow current estimation circuit 347 instructs the system impedance estimation circuit 350 to output the impedance estimation results of the distribution system impedances 7a to 7n. In response to the instruction, the system impedance estimation circuit 350 outputs the estimation results of the distribution system impedances to the power flow current estimation circuit 347.

[0211] Here, a brief description will be given of the impedance estimation method of the grid impedance estimation circuit 350. As described above, the forward flow power flowing through the distribution grid impedances 7a-7n can be calculated based on the voltage measurement information at the interconnection points of the AC / DC converter 6 and each power converter 9a-9n with the DC distribution grid 21, the output power measurement results of the AC / DC converter 6 and each power converter 9a-9n, the power consumption of the consumer loads 11 in the consumer load group 10, and the measurement results of the power generated by the PV panel 12, all of which are received during the 30-minute cycle process (first process in FIG. 22 ) and the 5-minute cycle process (second process in FIG. 22 ). The output power measurement results of the AC / DC converter 6 and each power converter 9a-9n and the calculation results of the forward flow power can then be used to estimate the values ​​of the distribution grid impedances 7a-7n. This estimation result is merged with the distribution grid impedance estimation result stored in a database (not shown) and stored in the database as new data.

[0212] More specifically, referring to FIG. 19 , the impedance value of the distribution system impedance 7a can be calculated as (Vdc_0-Vdc_a) / Idc_0 from the actual measured values ​​of the output voltage (Vdc_0) and output current (Idc_0) of the AC / DC converter 6 and the actual measured value of the interconnection point voltage (Vdc_a) of the power converter 9a with the DC distribution system 21 (21a). The calculated impedance value can be used to update the impedance estimate of the distribution system impedance 7a stored in the distribution system impedance estimation database. For example, the impedance estimate can be updated using an exponential smoothing method that adds (1-α) times the current database value and α times the calculation result (e.g., α = 0.01). Note that the method for updating the impedance estimate is not limited to the above, and any method can be used.

[0213] Next, a method for calculating the distribution system impedance 7b one level downstream in FIG. 19 will be described. First, to calculate the DC current I_a in FIG. 19, the excess or shortage of power in the consumer load group 10a (i.e., the value obtained by subtracting the actual measured power generation of the PV panel 12 from the actual measured power consumption of the consumer load 11) is calculated. Then, the output power (charge power or discharge power) to the DC distribution system 21a can be calculated by subtracting the actual measured output power of the power converter 9a from the calculated subtraction value. The DC current Idc_a flowing through the distribution system impedance 7b (Idc_a = (Idc_0 - I_a)) can be calculated by dividing the output power by the actual measured voltage (Vdc_a) at the interconnection point between the power converter 9a and the DC distribution system 21 (21a). Therefore, similar to the distribution system impedance 7a, the impedance value of the distribution system impedance 7b can also be calculated as "(Vdc_a - Vdc_b) / Idc_a." Similarly to the above, the calculation result of the impedance value of the power distribution system impedance 7b can be stored in the power distribution system impedance estimation database along with updating the impedance estimation value. Note that the method for constructing the power distribution system impedance estimation database is not directly related to the point of the present disclosure, and therefore further explanation will be omitted.

[0214] 24 again, upon completion of reading the estimation results of the distribution system impedances 7a to 7n (S1055), the power flow current estimation circuit 347 calculates the power flow current in the DC distribution system 21 in S1056. Specifically, the power flowing through each of the distribution system impedances 7a to 7n is calculated from the estimation results of the excess or shortage of power in each consumer load group 10 calculated in S1054, the charging / discharging power (equivalent to Pref) from each power converter 9, and the demand power (equivalent to Pref) supplied from the AC / DC converter 6. Then, a current value is calculated from the calculation results of the power.

[0215] When the calculation of the power flow current flowing through the DC distribution system 21 (S1056) is completed, the system voltage estimation circuit 348 (Figure 3) predicts the voltage value of the interconnection point (power receiving point) of each power converter 9 with the DC distribution system 21 (each power receiving point voltage prediction 1) in S1057.

[0216] FIG. 26 shows a flowchart illustrating the detailed control process of S1057 (each receiving point voltage prediction 1) in FIG.

[0217] 26 , when the flow of each power receiving point voltage prediction 1 (S1057) starts, the power flow current estimation circuit 347 collects drooping characteristic information of the AC / DC converter 6 by reading it from the memory circuit 32 via the operation plan creation unit management circuit 346 in S10571. After completing S10571, the power flow current estimation circuit 347 collects power command value information (Pref) of the AC / DC converter 6 by reading it from the operation plan creation unit management circuit 346 in S10572. After completing the collection of the power command value information of the AC / DC converter 6 (S10572), the power flow current estimation circuit 347 calculates the output voltage (voltage command value) of the AC / DC converter 6 in S10573. As described above, in the first embodiment, it is assumed that the output voltage (voltage command value) of the AC / DC converter 6 is the reference voltage (1500 [V]).

[0218] Once the output voltage of the AC / DC converter 6 is determined in S10573, the power flow current estimation circuit 347 selects in S10574 the power converter 9a located immediately downstream of the AC / DC converter 6. Furthermore, in S10575, the power flow current estimation circuit 347 collects drooping characteristic information of the first DC / DC conversion circuit 93 in the power converter 9 (9a) selected in S10574.

[0219] Before proceeding with the explanation of the control process in FIG. 26 , the two types of drooping characteristics of the first DC / DC conversion circuit 93 in the power converter 9 of the distribution system storage battery 8, which were explained in FIGS. 17 and 18 , will be explained in detail.

[0220] Fig. 17 shows an example of the drooping characteristics of the first DC / DC conversion circuit 93 operating in the voltage control mode, while Fig. 18 shows an example of the drooping characteristics of the first DC / DC conversion circuit 93 operating in the power control mode.

[0221] 11 to 13 show configuration examples of the second voltage target generation circuit 942 (FIG. 9) that operates in the voltage control mode and is mounted in the second control circuit 94 in the power converter 9. Furthermore, as described in FIG. 11, the first voltage target generation circuit 682 (FIG. 8) in the AC / DC converter 6 that operates in the voltage control mode also has a circuit configuration similar to that of the second voltage target generation circuit 942 (first DC / DC conversion circuit 93).

[0222] Next, the characteristics of the voltage control mode and the power control mode will be described with reference to FIGS. 17, 18, 20, and 21. FIG.

[0223] First, the voltage control mode will be described. In the voltage control mode, in the first DC / DC conversion circuit 93 (FIG. 6) in the power converter 9 for the distribution system storage battery, the second voltage target generation circuit 942 (FIG. 9) in the second control circuit 94 controls the target value of the DC voltage to be output to the DC distribution system 21.

[0224] Specifically, the first DC / DC conversion circuit 93 compares the DC voltage of the DC power distribution system 21 with a voltage command value (Vref), and when the DC voltage of the DC power distribution system 21 is lower than the voltage command value (Vref), it determines that the amount of power supply is small and operates to increase the discharge power of the power distribution system storage battery 8 (or decrease the charge power during charging). At this time, the DC voltage of the DC power distribution system 21 output by the first DC / DC conversion circuit 93 decreases as the output power increases, in accordance with the drooping characteristics shown in Fig. 17 .

[0225] On the other hand, when the DC voltage of the DC power distribution system 21 is higher than the voltage command value (Vref), the first DC / DC conversion circuit 93 determines that excessive power is being supplied, and operates to reduce the discharge power of the power distribution system storage battery 8 (or increase the charge power during charging operation). At that time, the DC voltage of the DC power distribution system 21 output by the first DC / DC conversion circuit 93 increases in accordance with the decrease in output power, in accordance with the drooping characteristic shown in Fig. 17 .

[0226] As described above, in the voltage control mode, the voltage at the interconnection point with the DC distribution system 21 is controlled based on the drooping characteristic shown in Fig. 17 , which is based on the power charged and discharged by the first DC / DC conversion circuit 93. Therefore, when the load fluctuation (fluctuation in the power consumption of the consumer load 11) or the power generation amount (power generation) of the PV panel 12 fluctuates, the first DC / DC conversion circuit 93 operating in the voltage control mode first supplies the excess or shortage of power to the DC distribution system 21. At that time, the voltage of the DC distribution system 21 is controlled based on the implemented drooping characteristic.

[0227] The features of the voltage control mode are described below. In the voltage control mode, the power converter 9 for the distribution system storage battery manages the interconnection point voltage of the DC distribution system 21, and therefore, as described above, can detect load fluctuations and fluctuations in the power generation amount (power generation) of the PV panel 12. Therefore, when multiple power converters 9 operating in the voltage control mode are connected to the DC distribution system 21, the (transient) response changes depending on the magnitude of the distribution system impedance 7 from the point where the load fluctuation and the power generation amount fluctuation of the PV panel 12 (hereinafter also referred to as "load fluctuation, etc.") occur to each power converter 9 operating in the voltage control mode. Specifically, differential power is preferentially supplied from the power converter 9 with the smallest distribution system impedance 7 to the point where the load fluctuation or power generation amount fluctuation occurs.

[0228] Fig. 20 shows a first example of response waveforms of each converter when the load power consumption of consumer load group 10a changes stepwise in DC power distribution system 21 shown in Fig. 19. In the first example, power converter 9a operates in voltage control mode.

[0229] For simplicity, it is assumed that the consumer loads 10b to 10d and the corresponding power converters 9b to 9d other than the consumer load 10a are stopped. In this case, the power converter 9a is connected to the consumer load 10a with an impedance of "zero," and the AC / DC converter 6 (operating in voltage control mode) is connected to the consumer load 10a via the distribution system impedance 7a.

[0230] At time t0, when the output power of the power converter 9a (DC / DC converter) and the AC / DC converter 6 is stable and the load power consumption by the consumer load group 10a increases stepwise, the output of the first DC / DC conversion circuit 93 in the power converter 9a increases, as shown by the dotted line in Figure 20, and all of the differential power, which is the increase in load power consumption, is first supplied by the power converter 9a, which has a small impedance between it and the consumer load group 10a.

[0231] Thereafter (after time t0), as shown in FIG. 20 , the AC / DC converter 6 operating in the voltage control mode supplies power based on the implemented drooping characteristic, and ultimately, in the example shown in FIG. 20 (where the first DC / DC conversion circuit 93 in the power converter 9a and the AC / DC converter 6 have the same drooping characteristic), the power increased due to the load fluctuation is divided proportionally between the first DC / DC conversion circuit 93 in the power converter 9a and the AC / DC converter 6, and the output power of both becomes stable.

[0232] Next, the power control mode will be described. As described above, in the power control mode, the first DC / DC conversion circuit 93 of the power converter 9 controls the charge / discharge power of the distribution system storage battery 8 in accordance with the DC voltage at the interconnection point of the DC distribution system 21. Therefore, in the power control mode, unlike the voltage control mode, the power converter 9 cannot detect load fluctuations and fluctuations in the amount of power generated by the PV panel 12.

[0233] Therefore, when a load fluctuation or the like occurs, the power converter 9 or AC / DC converter 6 operating in the voltage control mode first supplies the differential power to the load, and the DC voltage of the DC distribution system 21 that it manages (outputs) is controlled in accordance with the drooping characteristic in accordance with the supplied differential power. As a result, in accordance with changes in the DC voltage of the DC distribution system 21, the first DC / DC conversion circuit 93 in the power converter 9 operating in the power control mode controls the charge / discharge power based on the drooping characteristic shown in Fig. 18.

[0234] The features of the power control mode are described below. In the power control mode, charging and discharging power is controlled according to the interconnection point voltage of the DC distribution system 21. Therefore, the DC distribution system 21 cannot be constructed solely with distributed power sources (power converters 9 and distribution system batteries 8) that operate in the power control mode. That is, at least one distributed power source that operates in the voltage control mode is required to manage the DC voltage of the DC distribution system 21.

[0235] When the power converter 9 or AC / DC converter 6 operating in the voltage control mode manages the DC voltage of the DC distribution system 21, if a load fluctuation or the like occurs, the power converter 9 or AC / DC converter 6 operating in the voltage control mode supplies excess or shortage power (differential power) as described above, and manages (outputs) the DC voltage of the DC distribution system 21 based on the drooping characteristic. On the other hand, the power converter 9 operating in the power control mode controls the charge / discharge power of the distribution system storage battery 8 based on the interconnection point voltage of the DC distribution system 21.

[0236] Fig. 21 shows a second example of the response waveforms of each converter when the load power consumption of consumer load group 10a in DC power distribution system 21 shown in Fig. 19 changes stepwise. In the second example, power converter 9a operates in power control mode. In Fig. 21, as in Fig. 20, consumer load groups 10b to 10d other than consumer load group 10a and their corresponding power converters 9b to 9d are stopped, and AC / DC converter 6 operates in voltage control mode.

[0237] At time t0, as in Figure 20, when the load power consumption by the consumer load group 10a increases stepwise, the output of the power converter 9 in power control mode does not change in direct response to the load fluctuation, and as shown by the solid line in Figure 21, the excess or shortage of power (differential power) due to the load fluctuation is supplied by the AC / DC converter 6 operating in voltage control mode.

[0238] At this time, the AC / DC converter 6 controls the DC voltage of the DC distribution system 21 based on the drooping characteristic shown in Fig. 17, thereby reducing the voltage at the interconnection point of the power converter 9a with the DC distribution system 21. In response to this, the power converter 9a increases its output power (the discharge power of the distribution system storage battery 8a) based on the drooping characteristic shown in Fig. 18. As a result, after time t0, the output power of the AC / DC converter 6 gradually decreases, while the output power of the power converter 9a gradually increases. Finally, as in Fig. 20, the power increased due to the load fluctuation is proportionally divided between the first DC / DC conversion circuit 93 in the power converter 9a and the AC / DC converter 6, and the output power of both becomes stable.

[0239] In the voltage control mode, if the DC voltage of the DC distribution system 21 falls outside the voltage range covered by the drooping characteristic (Vmax to Vmin in FIG. 17 ), there is a possibility that each converter will stop due to an overcurrent or the like. In contrast, the power control mode is characterized in that, even if the DC voltage of the DC distribution system 21 falls outside the voltage range covered by the drooping characteristic (Vmax to Vmin in FIG. 17 ), operation can be continued with the charging / discharging power fixed at the maximum charging / discharging power (converter capacity). In other words, the power control mode is more advantageous in terms of system operation continuity. Note that a specific method for constructing the DC distribution system 21 using such a voltage control mode and a power control mode is not directly related to the main points of the present disclosure, and therefore further description thereof will be omitted.

[0240] Returning to FIG. 26, the detailed control process of each receiving point voltage prediction 1 (S1057: FIG. 24) by the system voltage estimation circuit 348 (FIG. 3) of the CEMS 3 will be described again.

[0241] When the power flow current estimation circuit 347 completes collection of drooping characteristic information of the first DC / DC conversion circuit 93 in the power converter 9 selected in S10574 (S10575), it acquires power command value (Pref) information to be notified to the first DC / DC conversion circuit 93 in the selected power converter 9 in S10576.

[0242] Then, in S10577, the power flow current estimation circuit 347 estimates the power flow current and outputs the estimation result to the system voltage estimation circuit 348, which then calculates a voltage drop value based on the power flow current estimation result.

[0243] When the calculation of the voltage drop value due to the power flow current in S10577 is completed, the system voltage estimation circuit 348 calculates in S10578 the output voltage of the first DC / DC conversion circuit 93 in the power converter 9 selected in S10574, i.e., the voltage at the interconnection point with the DC distribution system 21. The calculation result is output to the operation plan creation unit management circuit 346.

[0244] In S10579, the operation plan creation unit management circuit 346 uses the interconnection point voltage calculated in S10578 and the drooping characteristic information collected in S10575 to calculate the output power (charge power or discharge power) from the first DC / DC conversion circuit 93 in the selected power converter 9. Then, based on the calculated charge / discharge power, the calculation result of the power flow current of the DC distribution system 21 is corrected.

[0245] When the correction to the power flow current calculation result of the DC power distribution system 21 in S10579 is completed, the operation plan creation unit management circuit 346 checks in S10580 whether or not estimation of the output voltage of the first DC / DC conversion circuit 93 for all power converters 9 is completed. If estimation of the output voltage of the first DC / DC conversion circuit 93 for all power converters 9 is not completed (NO in S10580), in S10581, a new power converter 9 located one step downstream from the currently selected power converter 9 is selected, and the process returns to S10575. For example, if S10581 is executed when power converter 9a has been selected in S10574, a new power converter 9b is selected, and the processes of S10575 to S10580 are executed.

[0246] Therefore, until the most downstream power converter 9n (FIG. 9) is selected and the processes of S10575 to S10580 are executed, a NO determination is made in S10580, and the processes of S10575 to S10580 are repeated. When estimation of the output voltage of the first DC / DC conversion circuit 93 for all power converters 9 is completed, a YES determination is made in S10580, and the operation plan creation unit management circuit 346 ends the process of S1057 (each power receiving point voltage prediction 1).

[0247] Returning to FIG. 24 , upon completing S1057, the operation plan creation unit management circuit 346 checks in S1058 whether the voltages at the interconnection points of the AC / DC converter 6 and all power converters 9 with the DC distribution system 21 (i.e., all voltages at the power receiving points) predicted in S1057 are within the voltage control range (the range of Vrange_max to Vrange_min in FIG. 19 ). In the first embodiment, as described above, if the appropriate voltage range of the DC distribution system 21 is set to, for example, a reference voltage (1500 V) ±0.1 (10%), the voltage control range can be set to, for example, the reference voltage ±0.075 (7.5%). In this case, (0.1 - 0.075) = 2.5% corresponds to a margin for when a load fluctuation or the like occurs.

[0248] When the determination in S1058 is NO, that is, when even one estimated value of the interconnection point voltage (power receiving point voltage) of the power converter 9 with the DC power distribution system 21 is outside the voltage control range, the operation plan creation unit management circuit 346 proceeds to the process in S1059 and executes review 1 of the charging / discharging power of the power distribution system storage battery 8. The review of the charging / discharging power of the power distribution system storage battery 8 corresponds to a modification (correction) of the power command value of the power converter 9.

[0249] 27A and 27B show a flowchart illustrating detailed control processing of review 1 of charge / discharge power of the distribution system storage battery 8 in S1059 (FIG. 24).

[0250] 27A , when S1059 is started, the operation plan creation unit management circuit 346 extracts in S10591 power converters 9 whose estimated values ​​(S1057) of the interconnection point voltages (receiving point voltages) of the power converters 9 with the DC power distribution system 21 are outside the voltage control range. Furthermore, in S10592, it is determined whether or not the interconnection point voltages (receiving point voltages) of the power converters 9 that are outside the voltage control range deviate on the lower limit voltage side (i.e., whether or not the connecting point voltages are less than the control lower limit voltage Vrange_min).

[0251] When the voltage at the point of power reception deviates to the lower limit voltage side (YES in S10592), the operation plan creation unit management circuit 346 proceeds to S10593 and selects the power converter 9 (power converter 9a in the example of FIG. 9 ) connected downstream of the AC / DC converter 6. Furthermore, in S10594, the operation plan creation unit management circuit 346 collects the power command value (Pref) of the power converter 9 selected in S10593.

[0252] In the first embodiment, a case will be described in which, when the interconnection point voltage (receiving point voltage) deviates from a predetermined voltage control range, the power command value is changed to deal with the deviation. Therefore, when the receiving point voltage deviates from the lower limit of the voltage control range, it is determined that the current (power) flowing forward through the DC distribution system 21 is large, and the power command value of each power converter 9 is increased (i.e., the discharge power is increased or the charge power is decreased). On the other hand, when the receiving point voltage deviates from the upper limit of the voltage control range, it is determined that the current (power) flowing forward through the DC distribution system 21 is small (or the reverse power is large), and the power command value of each power converter 9 is decreased (i.e., the discharge power is decreased or the charge power is increased).

[0253] When the operation plan creation unit management circuit 346 has completed collection of the power command value (Pref) of the selected power converter 9 (S10594), it checks in S10595 whether the grid interconnection point voltage (power receiving point voltage) of the selected power converter 9 deviates from the voltage control range. If the determination in S10595 is YES, in order to increase the power command value of the power converter 9, a constant α is added to the power command value (Pref) collected in S10594 (Pref = Pref + α) in S10596.

[0254] On the other hand, when the determination in S10595 is NO, for the power command value of the power converter 9 whose receiving point voltage is within the voltage control range, in S10597, a constant β is added to the power command value (Pref) collected in S10594 (Pref = Pref + β). Note that the constants α (S10596) and β (S10597) are set so that α > β. In this way, by relatively increasing the amount of correction of the power command value of the power converter 9 whose receiving point voltage deviates from the lower limit of the voltage control range, it is possible to effectively allocate and suppress forward power.

[0255] Upon completing the processing of S10596 or S10597, the operation plan creation unit management circuit 346 checks in S10598 whether the corrected power command value exceeds the converter capacity (maximum power Pmax that can be output (discharged)) of the first DC / DC conversion circuit 93 in the power converter 9. If the corrected power command value exceeds the maximum power Pmax (YES determination in S10598), the power command value (Pref) is changed to Pmax in S10599, and the process proceeds to S10600. On the other hand, if NO determination is made in S10598, the corrected power command value is equal to or less than the maximum power Pmax, so the corrected power command value is maintained, and the process proceeds to S10600.

[0256] In S10600, the operation plan creation unit management circuit 346 checks whether the power command values ​​of the first DC / DC conversion circuits 93 have been corrected for all power converters 9. If the correction of the power command values ​​of the first DC / DC conversion circuits 93 for all power converters 9 has not been completed (NO in S10600), the operation plan creation unit management circuit 346 selects a new power converter 9 located one step downstream from the currently selected power converter 9 in S10601 and returns to S10594. The operation plan creation unit management circuit 346 then executes the processes of S10594 to S10600 for the power converter 9 newly selected in S10601. When the correction estimation of the power command values ​​of the first DC / DC conversion circuits 93 for all power converters 9 has been completed, a YES determination is made in S10600, and the process proceeds to S10611.

[0257] On the other hand, when the determination in S10592 is NO, that is, when the voltage at the power receiving point deviates to the upper limit voltage side of the voltage control range, the operation plan creation unit management circuit 346 proceeds to the process of S10603 in Fig. 27B . As described above, when the voltage at the power receiving point deviates to the upper limit value side of the predetermined voltage control range, it means that the current (power) flowing forward through the DC distribution system 21 is small or the power flowing backward is large.

[0258] 27B , in S10603, similarly to S10593, the operation plan creation unit management circuit 346 selects the power converter 9 (power converter 9 a in the example of FIG. 9 ) connected downstream of the AC / DC converter 6. Furthermore, in S10604, the operation plan creation unit management circuit 346 collects the power command value (Pref) of the power converter 9 selected in S10603.

[0259] When the operation plan creation unit management circuit 346 has completed collection of the power command value (Pref) of the selected power converter 9 (S10604), it checks in S10605 whether the grid interconnection point voltage (receiving point voltage) of the selected power converter 9 deviates from the voltage control range. If the determination in S10605 is YES, for the power command value of the power converter 9 whose receiving point voltage deviates from the voltage control range, in S10606, a constant γ is subtracted from the power command value (Pref) collected in S10604 (Pref = Pref - γ).

[0260] On the other hand, when the determination in S10605 is NO, for the power command value of the power converter 9 whose receiving point voltage is within the voltage control range, in S10607, a constant ε is subtracted from the power command value (Pref) collected in S10604 (Pref = Pref - ε). Note that the constants γ (S10606) and ε (S10607) are set so that γ > ε. In this way, by relatively increasing the amount of correction of the power command value of the power converter 9 whose receiving point voltage deviates toward the upper limit of the voltage control range, it is possible to suppress reverse power flow or increase forward power flow through efficient allocation.

[0261] When the operation plan creation unit management circuit 346 finishes the processing of S10606 or S10607, it checks in S10608 whether the corrected power command value exceeds the converter capacity (maximum power Pmin that can be input (charged)) of the first DC / DC conversion circuit 93 in the power converter 9. If the corrected power command value exceeds the maximum power Pmin (YES determination in S1060), the power command value (Pref) is changed to Pmin in S10609, and the process proceeds to S10610. On the other hand, if NO determination is made in S10608, the corrected power command value (charging side) is equal to or less than the maximum power Pmin, so the corrected power command value is maintained, and the process proceeds to S10610.

[0262] In S10610, the operation plan creation unit management circuit 346 checks whether the power command values ​​of the first DC / DC conversion circuits 93 have been corrected for all power converters 9. If the correction of the power command values ​​of the first DC / DC conversion circuits 93 for all power converters 9 has not been completed (NO in S10610), the operation plan creation unit management circuit 346 selects a new power converter 9 located one step downstream from the currently selected power converter 9 in S10611 and returns to S10604. The operation plan creation unit management circuit 346 then executes the processes of S10604 to S10610 for the power converter 9 newly selected in S10611. When the correction estimation of the power command values ​​of the first DC / DC conversion circuits 93 for all power converters 9 has been completed, a YES determination is made in S10610, and the process proceeds to S10611 in FIG. 27A . That is, when the operation plan creation unit management circuit 346 completes the correction of the power command value of the first DC / DC conversion circuit 93 for all power converters 9 for both the YES judgment and the NO judgment of S10592, it executes the processing of S10611.

[0263] Referring again to Figure 27A, in S10611, the operation plan creation unit management circuit 346 generates a power command value (Pref) for the AC / DC converter 6 based on the corrected power command value of the power converter 9, the predicted power consumption results of each consumer load 11 in each consumer load group 10, and the predicted power generation amount results of the PV panel 12.

[0264] Specifically, the power command value (Pref) of the AC / DC converter 6 can be calculated by subtracting the total value of the predicted power generation amounts of the PV panels 12 from the total value of the predicted power consumption values ​​of the consumer loads 11, and further subtracting the total value of the corrected power command values ​​of the power converters 9. When S10611 is completed, the processing of S1059 in Fig. 24 is completed.

[0265] In the first embodiment, the constants α, β, γ, and ε are set so that the correction amount (offset amount) of the power command value is larger for a power converter 9 (first DC / DC conversion circuit 93) whose interconnection point (power receiving point) voltage deviates from the voltage control range compared to a power converter 9 whose voltage does not deviate from the voltage control range. However, the setting of such offset amounts is not limited to the above example. For example, the offset amount may be set depending on the SOC of the corresponding distribution system storage battery 8. For example, the offset amount can be set larger for a power converter 9 corresponding to a distribution system storage battery 8 with a larger SOC.

[0266] Alternatively, the offset amount may be set depending on the connection position of the power converter 9. For example, a larger offset amount can be set for a power converter 9 closer to the upstream side of the power flow current (smooth or reverse current). It is also possible to set the offset amount for correcting the power command value for each power converter 9 depending on the distance between the power converter 9 and the AC / DC converter 6 (the magnitude of the distribution system impedance 7) or the combination of the connection position of the power converter 9 and the current direction in the DC distribution system 21 (smooth / reverse current).

[0267] 24 , the operation plan creation unit management circuit 346 executes the processes of S1056 to S1058 using the power command value corrected in S1059 (review 1 of charge / discharge power of the distribution system storage battery 8). Correction of the voltage command value of the first DC / DC conversion circuit 133 of the power converter 9 by review 1 of charge / discharge power of the distribution system storage battery 8 (S1059) is repeatedly executed until a YES determination is made in S1058. Then, when the voltage command values ​​of the first DC / DC conversion circuits 133 of all the power converters 9 are set so that all estimated values ​​of the interconnection point voltages (power receiving point voltages) of the power converter 9 with the DC distribution system 21 are within the voltage control range, the "operation plan creation 1" in S105 ( FIG. 23 ) is terminated.

[0268] Returning to FIG. 23 , when the creation of the operation plan in S105 is completed, in S110 the operation plan creation unit management circuit 346 transmits the power command values ​​set in the operation plan created in S105 to the AC / DC converter 6 and each of the power converters 9 a to 9 n.

[0269] On the other hand, if the operation plan creation circuit 34 has not received an operation plan creation request (24-hour supply and demand plan) from the DSO 2 in S104 (NO in S104), it checks in S106 whether it is the time to collect various measurement results, specifically, whether it is the start time of the 5-minute periodic processing in Fig. 22. If it is not the collection time (NO in S106), the process returns to S101 and continues.

[0270] On the other hand, if it is the collection time (YES in S106), the operation plan creation circuit 34 instructs the transmission data generation circuit 35 in S107 to generate a measurement data output request packet that requests the connected devices of the DC distribution system 21 (AC / DC converter 6, power converters 9a to 9n, consumer loads 11a to 11n, and power converters 13a to 13n for consumer PV) to transmit measurement data.

[0271] 1 to 3 , when the transmission data generation circuit 35 receives the request to generate the measurement data output request packet, it generates a measurement data output request packet to be transmitted to each connected device and outputs the generated measurement data output request packet to the communication circuit 31. At that time, the transmission data generation circuit 35 notifies the operation plan creation circuit 34 and the distributed power source management unit control circuit 36 ​​that the measurement data output request packet has been output to the communication circuit 31.

[0272] When the distributed power source management unit control circuit 36 ​​receives the output notification of the measurement data output request packet from the transmission data generation circuit 35, it instructs the communication circuit 31 to transmit the input measurement data output request packet to the communication line 22. In response to the instruction, the communication circuit 31 transmits the measurement data output request packet from the transmission data generation circuit 35 and waits until it receives the measurement data from the connected device at the transmission destination.

[0273] Then, when the communication circuit 31 receives the measurement data, it stores the received measurement data in the memory circuit 32 and notifies the distributed power source manager control circuit 36 ​​that the measurement data has been received. When the distributed power source manager control circuit 36 ​​receives the notification, it instructs the transmission data generation circuit 35 to generate the next measurement data output request packet to request the measurement results of the next connected device. At that time, the operation plan creation circuit 34 is also notified that the measurement data has been received. The above-mentioned operation is executed for all devices that are connected to the DC distribution system 21 and are measuring the interconnection point voltage, power flow, etc. of the DC distribution system 21.

[0274] Then, when collection of all the measurement data is completed, the operation plan creation unit management circuit 346 in the operation plan creation circuit 34 instructs the power generation amount prediction circuit 342 and the power consumption prediction circuit 343 via the battery operation plan generation circuit 341 to update the power generation amount prediction database 351 and the power consumption prediction database 352 based on the collected measurement data. Upon receiving this instruction, the power generation amount prediction circuit 342 and the power consumption prediction circuit 343 calculate the amount of power generated by each PV panel 12 and the amount of power consumed by each consumer load 11 for five minutes from the received data in order to update the power generation amount prediction database 351 and the power consumption prediction database 352. Furthermore, the power generation amount prediction circuit 342 and the power consumption prediction circuit 343 add the calculated values ​​to the amounts of power generated and consumed up to that point stored in registers (not shown), and check whether it is time to update the databases.

[0275] In the first embodiment, as described above, the power generation amount prediction database 351 and the power consumption prediction database 352 construct the amount of power generated by the PV panels 12 a to 12 n and the power consumption of the consumer loads 11 a to 11 n for every 30 minutes. Therefore, the power generation amount prediction database 351 and the power consumption prediction database 352 update their data based on the date, time, day of the week, and weather information when measurement data for the amount of power generated and the amount of power consumed for 30 minutes are collected. When the databases are updated, the addition data for the 30 minutes stored in the register (not shown) is cleared, and the register is used to add the measurement data for the following 30 minutes.

[0276] Returning to Figure 23, when the operation plan creation unit management circuit 346 completes the construction (updating) of the above-mentioned power generation prediction database 351 and power consumption prediction database 352 in S107, it checks the collected measurement data in S108 and determines whether or not the operation plan needs to be revised.

[0277] Specifically, in the first embodiment, the determination of whether to correct the operation plan (S108) is made by checking (1) whether the interconnection point voltage (receiving point voltage) of the AC / DC converter 6 and the power converters 9a to 9n with the DC power distribution system 21 is within a predetermined voltage control range, (2) whether the SOC of the power distribution system storage battery 8 is within a predetermined range, and (3) whether the output power from the AC / DC converter 6 is within a predetermined range centered on the demand power notified by the DSO2.

[0278] 28A and 28B show a flowchart illustrating detailed control processing for determining whether to modify the operation plan in S108 (FIG. 23).

[0279] 28A , when S108 is started, the operation plan creation unit management circuit 346 clears (sets to "0") a register (not shown) for the "operation plan correction flag" in S10801. An "operation plan correction flag" is provided for each converter, that is, for each of the AC / DC converter 6 and the power converters 9a to 9n.

[0280] Furthermore, in S10802 and S10803, the operation plan creation unit management circuit 346 collects actual measurement results of the voltage and power at the power receiving points (interconnection points) of the AC / DC converter 6 and the power converters 9a to 9n from the memory circuit 32. Furthermore, in S10804, the operation plan creation unit management circuit 346 collects SOC information of the distribution system storage battery 8 from the memory circuit 32.

[0281] In S10805, the operation plan creation unit management circuit 346 calculates the actual value of the power flow current using the actual measured value of the demand power of the consumer load groups 10a to 10n, and the measured voltage and output power of the AC / DC converter 6 and the power converters 9a to 9n collected in S10802 and S10803.

[0282] Upon completing the calculation of the power flow current in S10805, the operation plan creation unit management circuit 346 selects the AC / DC converter 6 in S10806, and checks in S10807 whether the voltage at the power receiving point (connection point) of the AC / DC converter 6 selected in S10806 is within the voltage control range (the range of Vrange_max to Vrange_min shown in FIG. 19 ). If the power receiving point voltage is not within the voltage control range (NO in S10807), the operation plan creation unit management circuit 346 sets a register (not shown) of an "operation plan correction flag" (set to "1") in S10809.

[0283] On the other hand, if the voltage at the power receiving point is within the voltage control range (YES in S10807), the operation plan creation unit management circuit 346 checks in S10808 whether the output power is within the planned range. Specifically, it checks whether the output power of the AC / DC converter 6 is within a predetermined range centered on the demand power notified by the DSO 2. If the output power of the AC / DC converter 6 is not within the predetermined range (NO in S10808), the operation plan creation unit management circuit 346 sets an "operation plan correction flag" register (not shown) (set to "1") in S10809.

[0284] If the determination in S10808 is YES, or in response to completion of setting the operation plan correction flag in S10809, the process proceeds to S108010 in Fig. 28B . In S10810, the operation plan creation unit management circuit 346 selects the power converter 9 (power converter 9 a in the example in Fig. 9 ) connected downstream of the AC / DC converter 6.

[0285] In S10811, the operation plan creation unit management circuit 346 checks whether the actual measurement value of the voltage at the receiving point of the power converter 9 selected in S10810 is within the voltage control range. If the voltage at the receiving point (actual measurement value) is outside the voltage control range (NO in S10811), an "operation plan correction flag" register (not shown) is set (set to "1") in S10815, and then the processing proceeds to S10816.

[0286] If the power receiving point voltage (actual measurement value) is within the voltage control range (YES determination in S10811), the operation plan creation unit management circuit 346 further checks in S10812 whether the output power (actual measurement value) of the power converter 9 selected in S101810 is within the planned range (for example, the range of Pmax to Pmin in FIGS. 17 and 18). If the output power (actual measurement value) is outside the planned range (NO determination in S10812), the "operation plan correction flag" register (not shown) is set (set to "1") in S10815, and then the processing proceeds to S10816.

[0287] If the output power (actual measured value) is within the planned range (YES in S10812), the operation plan creation unit management circuit 346 further checks in S10813 whether the SOC of the distribution system storage battery 8 controlled by the power converter 9 selected in S101810 is within a predetermined range. For example, in the first embodiment, if the SOC is outside the range of 5% to 90% then S10813 returns NO, i.e., it can be determined that the SOC is outside the predetermined range.

[0288] If the SOC is outside the predetermined range (NO in S10813), the "operation plan correction flag" register (not shown) is set (set to "1") in S10815, and then the process proceeds to S10816.

[0289] On the other hand, if the SOC is within the predetermined range (YES in S10813), the operation plan creation unit management circuit 346 checks in S10814 whether the power flow current (actual measured value) calculated in S10805 is within the predetermined range.

[0290] If the flow current (actual measured value) is outside the specified range (NO judgment in S10814), S10815 sets the ``operation plan correction flag'' register (not shown) (sets it to ``1''), and then processing proceeds to S10816.

[0291] On the other hand, if the power flow current (actual measured value) is within a predetermined range (YES determination in S10814), that is, if all of S10811 to S10814 are YES determinations, the operation plan creation unit management circuit 346 proceeds to S10816 to check whether the checks in S10811 to S10804 have been executed for all power converters 9. If the checks in S10811 to S10804 have not been completed for all power converters 9 (NO determination in S10816), the operation plan creation unit management circuit 346 selects a new power converter 9 located one step downstream from the currently selected power converter 9 in S10817, and returns the process to S10811.

[0292] Then, the operation plan creation unit management circuit 346 executes the processes of S10811 to S10815 for the power converter 9 newly selected in S10817. When the confirmations of S10811 to S10804 are completed for all of the power converters 9a to 9n, a YES determination is made in S10816, and it is determined whether or not the operation plan needs to be corrected according to the "operation plan correction flag."

[0293] Referring again to FIG. 23 , if the “operation plan correction flag” is set (“1”) for at least any of the converters (the AC / DC converter 6 and each power converter 9) at the end of the processing of S28A and S28B, the operation plan creation unit management circuit 346 determines YES in S108 and executes “operation plan correction 1” in S109.

[0294] 29A and 29B show a flowchart illustrating the detailed control process of "correction 1 of operation plan" in S109 (FIG. 23).

[0295] 29A, when S109 is started, the operation plan creation unit management circuit 346 collects in S10901 the actual measured values ​​of power supply and demand (the difference between the power consumption of the consumer load 11 and the power generated by the PV panel 12) of each of the consumer load groups 10a to 10n. Furthermore, in S10902, the operation plan creation unit management circuit 346 reads out the estimated value of impedance (the estimation result in S1055 of FIG. 24), and in S10903, extracts the converters (AC / DC converter 6 and / or power converter 9) for which the operation plan correction flag is set.

[0296] 28A , the operation plan creation unit management circuit 346 checks in S10904 whether the output power of the AC / DC converter 6 is within a predetermined range centered on the power demand notified by the DSO 2. If the output power is outside the predetermined range (NO in S10904), the operation plan creation unit management circuit 346 executes correction 1 of the power command value of the distribution system storage batteries 8 a to 8 n in S10905.

[0297] FIG. 30 shows a flowchart illustrating detailed control processing for correction 1 of the power command values ​​for the distribution system batteries 8a to 8n in S10905 of FIG. 29A.

[0298] 30 , when S10905 is started, the operation plan creation unit management circuit 346 reads, in S109051, the supply and demand plan collected from the DSO 2 from the storage circuit 32. Next, in S109052, the operation plan creation unit management circuit 346 reads the actual measured power value of the AC / DC converter 6 from the storage circuit 32 and generates a power command value (Pref) for the AC / DC converter 6.

[0299] In the first embodiment, the power command value (Pref) of the AC / DC converter 6 is basically set to the actually measured output power value of the AC / DC converter 6. However, if the actually measured power value deviates from a predetermined range centered on the power demand notified from the DSO 2, the power command value (Pref) is set to the upper limit value (if it deviates to the upper side) or the lower limit value (if it deviates to the lower side) of the predetermined range.

[0300] In S109054, the operation plan creation unit management circuit 346 calculates the power difference between the actual measured power value of the AC / DC converter 6 and the power command value (Pref) calculated in S109053, and allocates the calculated power difference to each power converter 9. This power difference becomes the power surplus or shortage in the DC power distribution system 21. In the first embodiment, this power surplus or shortage is covered by the power converters 9a to 9n installed in the DC power distribution system 21. For example, in the first embodiment, when a power difference occurs, the power difference is allocated in accordance with the ratio of the power command values ​​of the power converters 9 generated when the operation plan was created.

[0301] When the allocation of the power difference in S109054 is completed, the operation plan creation unit management circuit 346 generates power command values ​​for the power converters 9a to 9n based on the actual measured power of the power converters 9a to 9n in S109055. Specifically, the power command values ​​are generated by adding the power allocated in S109054 to the output power (actual measured power) of each power converter 9.

[0302] In S109056, the operation plan creation unit management circuit 346 checks whether the power command value generated in S109055 exceeds the capacity of the first DC / DC conversion circuit 93 of each power converter 9. If the power command value exceeds the converter capacity (YES in S109056), the process returns to S109054, and the allocation of the differential power among the power converters 9a to 9n is changed. For example, in the first embodiment, after correcting the power command value of the power converter 9 that exceeds the converter capacity in S109056 to a value equivalent to the converter capacity (for example, the maximum discharge power or the maximum charge power), the allocation to the power converter 9 that does not exceed the converter capacity can be corrected.

[0303] If the power command value of each power converter 9 does not exceed the converter capacity in S10906 (YES in S109056), the process proceeds to S109057 to check whether the power command values ​​of all power converters 9a to 9n have been calculated. If there is a power converter 9 for which a power command value has not been calculated (NO in S109057), the process returns to S109055, and the processes of S109055 to S109057 are repeated until S109057 returns YES. On the other hand, when the calculation of the power command values ​​of all power converters 9a to 9n is completed (YES in S109057), the operation plan creation unit management circuit 346 ends correction 1 (S10905) of the power command value of the distribution system storage battery 8.

[0304] Returning to FIG. 29A , when S10905 (correction 1 of the power command value of the distribution system storage battery 8) is completed, the operation plan creation unit management circuit 346 calculates the power flow current of the DC distribution system 21 based on the actual measurement data in S10906.

[0305] Specifically, using the power command value newly calculated in S10905, the power flow current can be calculated using the output power of the AC / DC converter 6, the charging and discharging power of the power converters 9a to 9n, the actual measured values ​​of the power consumption of the consumer loads 11a to 11n, and the actual measured values ​​of the power generated by the PV panels 12a to 12n.

[0306] When the determination in S10904 is YES, or after completing the processing of S10905 and S10906 when the determination in S10904 is NO, the operation plan creation unit management circuit 346 selects the power converter 9a installed downstream of the AC / DC converter 6 in S10907, and proceeds to S10908 in FIG. 29B.

[0307] 29B , in S10908, the operation plan creation unit management circuit 346 checks whether the SOC of the distribution system storage battery 8 controlled by the power converter 9 selected in S10907 is within a predetermined range similar to S10813 in Fig. 28B . If the SOC is outside the predetermined range (NO in S10908), the operation plan creation unit management circuit 346 corrects the power command value based on the SOC in S10909.

[0308] It is generally known that lithium-ion batteries rapidly deteriorate when overcharged or overdischarged. To prevent overcharging, for example, chargers installed in electric vehicles are controlled to charge using constant current control when the SOC is 90% or less, and switch to constant voltage control when the SOC exceeds 90%. In addition, to prevent overdischarge, such chargers are often configured to reduce discharge power when the SOC is 5% or less.

[0309] Furthermore, it is known that while typical lead-acid batteries do not deteriorate as rapidly when overcharged as lithium-ion batteries, overdischarging causes rapid battery deterioration. Thus, although characteristics vary depending on the type of battery, charging in a high SOC range and discharging in a low SOC range have the disadvantage of accelerating battery deterioration. Therefore, in the first embodiment, assuming that a lithium-ion battery is used as the power distribution system battery 8, the predetermined SOC range is set as described above, and the power command value is modified to throttle the charging and discharging power when the SOC is 90% or higher and when the SOC is 5% or lower.

[0310] 31A and 31B show a flowchart illustrating the detailed control process for correcting the power command value in S10909 of FIG. 29B.

[0311] 31A , when S10909 is started, the operation plan creation unit management circuit 346 checks in S109091 whether the SOC of the distribution system storage battery 8 controlled by the power converter 9 selected in S10907 ( FIG. 29A ) exceeds the upper limit value of a predetermined range (for example, 90(%) in the first embodiment). If the SOC exceeds the upper limit value (90(%)) (YES determination in S109091), the process proceeds to S109092 in FIG. 31B in S109092.

[0312] Referring to FIG. 31B, in S109092, the operation plan creation unit management circuit 346 checks whether the distribution system storage battery 8 is under discharge control, and if the discharging control that reduces the SOC is in progress (YES determination in S10902), there is no particular problem in terms of battery protection, so the process returns to FIG. 31A and ends the processing of S10909.

[0313] On the other hand, when the distribution system storage battery 8 is under charge control (NO in S109092), the operation plan creation unit management circuit 346 checks in S109093 whether the power command value (charging) of the power converter 9 is equal to or greater than a predetermined value. As described above, from the viewpoint of battery protection, it is better to switch the charging of the distribution system storage battery 8 to constant voltage control. However, for simplicity of explanation, in the first embodiment, this is handled by changing the power command value. For example, in S109093, it can be checked whether the power command value is equal to or greater than 10% of the converter capacity (charging) of the first DC / DC conversion circuit 93.

[0314] If the power command value (charging) is less than the predetermined value (NO in S10903), there is no particular problem in terms of battery protection, so the operation plan creation unit management circuit 346 returns to FIG. 31A and ends the processing of S10909.

[0315] On the other hand, if the power command value (charging) is equal to or greater than the predetermined value (YES in S10903), the operation plan creation unit management circuit 346 changes the power command value in S109094. For example, in the first embodiment, the power command value is set to a value equivalent to the predetermined value (10(%) of the converter capacity (charging) of the first DC / DC conversion circuit 93).

[0316] When the SOC is equal to or lower than the upper limit (90(%)) (NO in S109091), the operation plan creation unit management circuit 346 checks in S109095 whether the SOC is lower than the lower limit of a predetermined range (for example, 5(%) in the first embodiment). When the SOC is equal to or higher than the lower limit (NO in S10905), there is no particular problem in terms of battery protection, and the processing of S10909 is terminated.

[0317] On the other hand, if the SOC is less than the lower limit (5(%)) (YES determination in S109095), the operation plan creation unit management circuit 346 checks in S10906 whether the distribution system storage battery 8 is under discharge control, and if it is under charge control in which the SOC is increasing (NO determination in S10906), there is no particular problem in terms of battery protection, so the processing of S10909 is terminated.

[0318] If the distribution system storage battery 8 is under discharge control in S109096 (YES in S109096), the operation plan creation unit management circuit 346 checks in S109097 whether the power command value (discharge) of the power converter 9 is equal to or greater than a predetermined value. In the first embodiment, similar to the case of charging, also during discharging, in S109097, it is checked whether the power command value (discharge) of the power converter 9 is equal to or greater than a predetermined value. For example, in S109097, it can be checked whether the power command value is equal to or greater than 10% of the converter capacity (discharge) of the first DC / DC conversion circuit 93, similar to the case of charging.

[0319] If the power command value (discharge) is equal to or less than the predetermined value (YES in S10907), the operation plan creation unit management circuit 346 ends the processing of S10909 because there is no particular problem in terms of protecting the battery.

[0320] On the other hand, if the power command value (discharge) exceeds the predetermined value (NO in S10907), the operation plan creation unit management circuit 346 changes the power command value in S109098. For example, in the first embodiment, the power command value can be set to a value equivalent to the predetermined value (10% of the converter capacity (discharge) of the first DC / DC conversion circuit 93). When the power command value is changed in S109098 or S109094, the processing of S10909 is terminated.

[0321] Referring again to FIG. 29B, when the operation plan creation unit management circuit 346 has finished checking the SOC of the distribution system storage battery 8 controlled by the power converter 9 selected in S10907 in S10908 (if the result is YES) or S10909 (if the result is NO in S10908), it checks in S10910 whether the SOC has been checked for all of the distribution system storage batteries 8a to 8n.

[0322] If there is a distribution system storage battery 8 whose SOC has not been confirmed (NO in S10910), the operation plan creation unit management circuit 346 selects a new power converter 9 that is located one step downstream from the currently selected power converter 9 in S10911, and returns the processing to S10908.

[0323] Then, the operation plan creation unit management circuit 346 executes the processes of S10908 to S10910 for the distribution system storage battery 8 controlled by the power converter 9 newly selected in S10911. When confirmation of the SOC in S10908 and S10909 is completed for all of the distribution system storage batteries 8a to 8n, a YES determination is made in S10910, and the process proceeds to S10912.

[0324] In S10912, the operation plan creation unit management circuit 346 calculates (estimates) the power flow current of the DC power distribution system 21 using the corrected power command values ​​of the AC / DC converter 6 and the power converters 9a to 9n. Furthermore, when the operation plan creation unit management circuit 346 finishes calculating (estimating) the power flow current in S10912, it executes each power receiving point voltage prediction 1 (S1057) similar to that in Fig. 24. In S1057, the control processing in Fig. 26 already described is executed.

[0325] When the voltage prediction for each power receiving point in S1057 is completed, the operation plan creation unit management circuit 346 checks in S10913 whether all the power receiving point voltages predicted in S1057 are within the voltage control range (the range of Vrange_max to Vrange_min in FIG. 19 ). The processing of S10913 is the same as the processing of S1058 in FIG. 24 .

[0326] When the determination in S10913 is NO, that is, when even one estimated value of the interconnection point voltage (power receiving point voltage) of the power converter 9 with the DC distribution system 21 is outside the voltage control range, the operation plan creation unit management circuit 346 proceeds to the process of S1059 similar to that in Fig. 24 , performs review 1 of the charge / discharge power of the distribution system storage battery 8, and performs review of the charge / discharge power (power command value of the power converter 9) of the distribution system storage battery 8. In S1059, the control process already described in Figs. 27A and 27B is executed.

[0327] Furthermore, in S10914, the operation plan creation unit management circuit 346 calculates the power flow current of the DC power distribution system 21 using the power command values ​​(Pref) of the AC / DC converter 6 and the power converter 9 after correction in S1059. Then, using the calculation result of the power flow current in S10914, voltage prediction 1 of each power receiving point is executed in S1057, and it is confirmed in S10915 whether or not all power receiving point voltages predicted in S1057 are within the voltage control range.

[0328] When S10915 is determined to be NO, the process returns to S1059, and review 1 of the charge / discharge power of the distribution system storage battery 8 is executed again. That is, the processes of S105, S10914, S1057, and S10915 are repeated until S10915 is determined to be YES. When S10915 is determined to be YES, or when S10913 described above is determined to be YES, the operation plan creation unit management circuit 346 ends the process of "operation plan revision 1" in S109 ( FIG. 23 ). Therefore, it can be understood that when "operation plan revision 1" in S109 ( FIG. 23 ) is completed, the estimated values ​​of all interconnection point voltages (power receiving point voltages) are within the voltage control range.

[0329] Returning to FIG. 23 , when the operation plan creation process in S105 or the modification of the operation plan in S109 is completed, the CEMS 3 (operation plan creation unit management circuit 346) notifies the transmission data generation circuit 35 and the communication circuit 31 in S110 to notify the AC / DC converter 6 and the power converters 9 a to 9 n of the operation plan including the power command value (Pref).

[0330] When the transmission of the operation plan in S110 is completed, the CEMS 3 (operation plan creation unit management circuit 346) determines in S111 whether to terminate the operation of the CEMS 3. If the determination in S111 is YES, the operation of the CEMS 3 is stopped, whereas if the determination in S111 is NO, the process returns to S101, and the CEMS 3 continues to execute the subsequent processes.

[0331] As described above, according to the power converter management device of the first embodiment, in order to manage the voltage of the DC power distribution system 21, the power command value (Pref) output to the AC / DC converter 6 and the power converters 9a to 9n (each converter) is estimated based on the drooping characteristics of the AC / DC converter 6 and the power converters 9a to 9n, each power command value (Pref), the predicted results of the power consumption of the consumer loads 11 and the power generation of the PV panels 12 in the consumer load groups 10a to 10n, and the estimated results of the distribution system impedance of the DC power distribution system 21, and the power command value (Pref) is generated so that the estimated result (connection point voltage) falls within a predetermined voltage control range. This makes it possible to appropriately manage the interconnection point (connection point) voltage of the DC power distribution system 21 to which the AC / DC converter 6 and the power converters 9a to 9n are connected.

[0332] Furthermore, even if the voltage at the interconnection point (power receiving point) of each converter with the DC distribution system 21 falls outside the appropriate range (voltage control range) due to load fluctuations or the like, the power command value (Pref) can be controlled to be corrected based on the actual measurement results. This allows the voltage at the interconnection point (power receiving point) of the DC distribution system 21 to be appropriately managed. In the first embodiment, measurement data is collected from the AC / DC converter 6, the power converters 9a to 9n, and each consumer load group 10 at five-minute intervals. However, the measurement data collection period is not limited to this example. To appropriately manage the voltage at the interconnection point (power receiving point), the collection period can be set to a shorter time (e.g., 30 seconds or 1 minute) as long as the CEMS 3 can perform calculations in time.

[0333] Next, the operations of AC / DC converter 6 and power converter 9 will be further described with reference to Figures 5 to 16 and Figures 32 to 35. As described above, in the first embodiment, the AC / DC converter 6 operates in a voltage control mode, and the power converters 9a to 9n for the distribution system storage batteries are assumed to be operable by selectively applying two control modes, a voltage control mode and a power control mode.

[0334] The operation of the AC / DC converter 6 will be described below with reference to Fig. 5. In the first embodiment, the AC / DC converter 6 operates in current control mode for the AC power distribution system 20, but at the same time, controls the voltage of the DC power distribution system 21 so as to be managed in voltage control mode.

[0335] Referring again to FIG. 5 , voltmeters 61a and 61b measure the voltage of the three-phase AC system. Ammeters 62a and 62b measure the current of the three-phase AC system. Phase voltages and phase currents to which no voltmeter or ammeter is connected can also be calculated from the values ​​measured by voltmeters 61a and 61b and ammeters 62a and 62b. Voltmeter 66 and ammeter 67 measure the DC voltage and DC current of DC distribution system 21. The measurement results of voltmeters 61a and 61b, ammeters 62a and 62b, voltmeter 66, and ammeter 67 are input to first control circuit 64.

[0336] Next, detailed operation of the first control circuit 64 will be described with reference to Fig. 8. Referring again to Fig. 8, the phase detection circuit 641 detects zero-crossing points of the AC system voltage waveform of the AC power distribution system 20b measured by the voltmeter 61. The first sine wave generation circuit 642 generates a reference sine wave synchronized with the AC system voltage waveform of the AC power distribution system 20b from information on the zero-crossing points detected by the phase detection circuit 641 and the AC system voltage waveforms output from the voltmeters 61a and 61b. The reference sine wave used during current control is output from the first sine wave generation circuit 642 to a multiplier 645.

[0337] The measurement result (DC voltage of DC power distribution system 21) by voltmeter 66 is input to subtractor 643 and fourth control circuit 647 in current control circuit 640. Note that current control circuit 640 executes current control to output power in synchronization with AC system voltage, which is the same control method as that used in general power converters for solar power generation installed in homes.

[0338] The fourth control circuit 647 stores a target voltage of the DC power distribution system 21, and the target voltage is output from the fourth control circuit 647 to the subtractor 643. As will be described in detail later, the target voltage of the DC power distribution system 21 is generated by the first voltage target generation circuit 682 and output to the subtractor 643 in the current control circuit 640 via the fourth control circuit 647. The current control circuit 640 controls the AC current output from the first AC / DC conversion circuit 63 so that the DC voltage of the DC power distribution system 21 measured by the voltmeter 66 becomes the target voltage.

[0339] The output of the subtractor 643, i.e., the value obtained by subtracting the output of the voltmeter 66 (the DC voltage of the DC power distribution system 21) from the target voltage, is input to a first PI control circuit 644. The first PI control circuit 644 performs PI control so that the subtracted value output from the subtractor 643 becomes zero. The output of the first PI control circuit 644 is input to a multiplier 645 and multiplied by the output of the first sine wave generating circuit 642, thereby being converted into a current command value (AC).

[0340] The current command value output from the multiplier 645 is input to the subtractor 646. The subtractor 646 outputs a value obtained by subtracting the AC current value of the AC power distribution system 20b measured by the ammeter 62 from the current command value. The subtracted value output from the subtractor 646 is input to a second PI control circuit 648, which performs PI control so that the value subtracted by the subtractor 646 becomes zero. The output of the second PI control circuit 648 is PWM-modulated by a first PWM conversion circuit 649 and input to the first AC / DC conversion circuit 63. The first AC / DC conversion circuit 63 operates in accordance with the control command value (PWM-modulated signal) output from the first PWM conversion circuit 649, and outputs an AC current.

[0341] The fourth control circuit 647 collects measurement results related to the DC power distribution system 21 output from the voltmeter 66 and the ammeter 67, as well as measurement results related to the AC power distribution system 20 output from the voltmeters 61a, 61b and the ammeters 62a, 62b. The information collected by the fourth control circuit is notified to the CEMS 3 and the like via the first communication interface circuit 65. The effective voltage of the AC power distribution system 20b and the effective voltage of the AC system measured by an effective voltage measurement unit (not shown) are also notified to the CEMS 3 and the like. Furthermore, information on active power and reactive power measured by an active power measurement unit (not shown) and a reactive power measurement unit (not shown) of the AC system can also be notified from the fourth control circuit 647 to the CEMS 3 via the first communication interface circuit 65.

[0342] Next, the detailed operation of the first AC / DC conversion circuit 63 will be described with reference to the flowchart of FIG.

[0343] 32, when control of the first AC / DC conversion circuit 63 is started, the fourth control circuit 647 initializes various parameters in the first control circuit 64 in S201, and initializes the power command value to "0" and the voltage command value to "1500 [V]" in S202. Then, the fourth control circuit 647 collects information from various voltmeters and ammeters in S203, and executes control of the first AC / DC conversion circuit 63 in S204.

[0344] FIG. 33 shows a flowchart for explaining the detailed control process of the first AC / DC conversion circuit 63 in S204 of FIG.

[0345] 33 , when S204 (control of the first AC / DC conversion circuit 63) in FIG. 33 is started, the fourth control circuit 647 acquires the measurement results of the AC-side voltmeters 61a and 61b in S2041. Furthermore, the fourth control circuit 647 instructs the phase detection circuit 641 to detect the phase and frequency of the AC voltage of the AC power distribution system 20b in S2042 and S2043. For example, in the first embodiment, the phase detection circuit 641 detects zero-crossing points from the AC voltage waveform output from the AC-side voltmeters 61a and 61b and detects the frequency of the AC system voltage from the zero-crossing point detection result. The frequency information, along with the zero-crossing point information, is output to the first sine wave generation circuit 642.

[0346] More specifically, the phase detection circuit 641 detects zero-crossing points (more specifically, the times at which the zero-crossing points are measured) from the AC voltage waveform measured by the AC-side voltmeters 61a and 61b (S2042), and detects the frequency from the time interval between the detected zero-crossing points (the time difference between the time of the previously detected zero-crossing point and the time of the currently detected zero-crossing point) (S2043). Note that the detection of the frequency of the AC system voltage is not limited to a method that uses the detection results of the zero-crossing points. Note that in the first embodiment, the phase of the AC power distribution system 20b is detected using the detection times of the zero-crossing points.

[0347] Meanwhile, in S2945, the voltmeter 66 and the ammeter 67 measure the voltage and current of the DC power distribution system 21. In S2946, the first power calculation circuit 681 calculates the power output from the AC / DC converter 6 to the DC power distribution system 21 from the voltage and current information measured in S2045. In S2047, the first voltage target generation circuit 682 generates a target voltage for the DC power distribution system 21 based on the drooping characteristic, using the measured power (S2046) calculated by the first power calculation circuit 681. As described with reference to FIGS. 11 to 13 , the first voltage target generation circuit 682 (second voltage target generation circuit 942) calculates the target voltage so as to have the drooping characteristic, using the first governor control circuit 6822 (9422) configured by a first-order system lag model and the first mass system calculation circuit 6825 (9425) to which an oscillation equation model is applied.

[0348] When the fourth control circuit 647 completes generation of the voltage target value in S2047, it generates a control command value for the first AC / DC conversion circuit 63 in S2048. Specifically, as described above, the control command value is generated by the current control circuit 640 in Fig. 8. This ends the control of the first AC / DC conversion circuit in S204.

[0349] As described above, in the current control circuit 640, a control command value for the first AC / DC conversion circuit 63 is generated by the first PI control (first PI control circuit 644) in accordance with the target voltage (S2047) and the second PI control (first PI control circuit 648) in accordance with the current command value (AC) set reflecting the result of the first PI control.

[0350] Specifically, the frequency and phase of the current command value (AC) are synchronized with the AC voltage waveform measured by the voltmeters 61a and 61b, and the amplitude of the current command value (AC) is set in accordance with a PI control calculation value (first PI control circuit 644) for reducing to zero the voltage difference between the target voltage (S2047) of the DC distribution system 21 and the DC measurement value measured by the voltmeter 66.

[0351] Furthermore, the PI control calculation result (second PI control circuit 648) for nulling the difference between the current command value (AC) and the AC current measured by the ammeters 62 a and 62 b is PWM-modulated to generate a control command value for the first AC / DC conversion circuit 63. The first AC / DC conversion circuit 63 outputs the AC current controlled by the control command value to the DC system.

[0352] Returning to FIG. 32 , upon completing the processing of S204, the fourth control circuit 647 checks in S205 whether a transmission request for measurement information has been received from the CEMS 3. If the transmission request has been received (YES in S205), the fourth control circuit 647 outputs the measurement information stored in memory (not shown) to the first communication interface circuit 65 in S206. Upon receiving the measurement data from the fourth control circuit 647, the first communication interface circuit 65 converts the measurement data into a predetermined format and transmits it to the CEMS 3 via the communication line 22. Upon completing transmission of the measurement data in S206, the fourth control circuit 647 proceeds to S207. Furthermore, if NO in S205, S206 is skipped and the processing proceeds to S207.

[0353] In S207, the fourth control circuit 647 checks whether control information (information such as a voltage command value and a power command value) has been received from the CEMS 3. If control information has been received (YES in S207), the fourth control circuit 647 sets the received power command value (Pref1) and voltage command value (Vref1) in a register (not shown) within the fourth control circuit 647 in S208. The fourth control circuit 647 then returns the process to S203 and continues to execute the processes from S203 onward using the power command value (Pref1) and voltage command value (Vref1) set in the register. On the other hand, if control information has not been received (NO in S207), the power command value (Pref1) and voltage command value (Vref1) are not updated, and the process returns to S203 and continues to execute the processes from S203 onward.

[0354] Next, the operation of the power converter for a distribution system storage battery will be described with reference to FIGS. 6, 9, 11 to 16, 34, and 35.

[0355] In the first embodiment, the power converter 9 shown in Fig. 6 has two modes: a voltage control mode and a power control mode. When operating in the voltage control mode, a power target value is generated by a second voltage target generation circuit 942 shown in Fig. 9. Then, based on the power target value generated by the second voltage target generation circuit 942, a second voltage target value control circuit 945 (Fig. 9) generates a current command value for controlling the first DC / DC conversion circuit 93. As described above, the configuration and operation of the second voltage target generation circuit 942 are the same as those of the first voltage target generation circuit 682.

[0356] On the other hand, when the power converter 9 operates in the power control mode, a power target value is generated by a power target generating circuit 943 ( FIG. 9 ). Then, based on the power target value generated by the power target generating circuit 943, a power target value control circuit 946 generates a current command value for controlling the first DC / DC conversion circuit 93. In FIG. 6 , the output voltage of the distribution system storage battery 8 measured by a voltmeter 91 and the DC current (charge current or discharge current) of the distribution system storage battery 8 measured by an ammeter 92 are input to a second control circuit 94. Similarly, the DC voltage of the DC distribution system 21 measured by a voltmeter 96 (corresponding to the output voltage of the power converter 9) and the current of the DC distribution system 21 measured by an ammeter 97 (corresponding to the output current (charge / discharge current) from the power converter 9 to the DC distribution system 21) are also input to the second control circuit 94.

[0357] Next, detailed operation of the second control circuit 94 will be described using Fig. 9. Referring again to Fig. 9, the second power calculation circuit 941 calculates the actual charge / discharge power of the power converter 9 by multiplying the DC voltage output by the power converter 9 measured by the voltmeter 96 by the DC current output by the power converter 9 measured by the ammeter 97. Note that the actual charge / discharge current can also be calculated from the measurement results of the voltage and current of the distribution system storage battery 8 measured by the voltmeter 91 and the ammeter 92.

[0358] The measured charge / discharge power calculated by the second power calculation circuit 941 is input to the second voltage target generation circuit 942, the power target generation circuit 943, the power target value control circuit 946, and the fifth control circuit 949. In the first embodiment, the fifth control circuit 949 also manages the measurement information measured by the voltmeters 91 and 96 and the ammeters 92 and 97, the charge / discharge power information calculated by the second power calculation circuit 941, and the SOC and SOH of the distribution system storage battery 8 calculated using the charge / discharge power information.

[0359] The measurement data, charge / discharge power, and SOC / SOH calculation results can be temporarily stored in a memory (not shown) and output to the CEMS 3 via the second communication interface circuit 95 when a request to transmit measurement data is received from the CEMS 3. The SOH can be estimated based on temperature information of the distribution system storage battery 8 measured by a thermometer (not shown), voltage transition information and charge / discharge power of the distribution system storage battery 8, the time during which the SOC is 90% or more, etc. However, the method for estimating the SOH is not the focus of the present disclosure, and therefore a detailed description thereof will be omitted.

[0360] The second voltage target generation circuit 942 starts generating a voltage target value when the calculation result of the actually measured charge / discharge power is input from the second power calculation circuit 941. The configuration (see FIGS. 11 to 13) and operation of the second voltage target generation circuit 942 are similar to those of the first voltage target generation circuit 682, and therefore detailed description thereof will not be repeated. The voltage target value output from the second voltage target generation circuit 942 is input to a second voltage target value control circuit 945.

[0361] As shown in FIG. 48 , in the second voltage target value control circuit 945, PI control (third PI control circuit 9452) is executed so that the subtraction value obtained by subtracting the actual voltage measured by the voltmeter 96 from the voltage target value from the second voltage target generation circuit 942 becomes zero, thereby calculating the control command value of the first DC / DC conversion circuit 93 in the voltage control mode.

[0362] 9, the power target generation circuit 943 starts generating a power target value when the calculation result of the measured charge / discharge power is input from the second power calculation circuit 941. As described in FIGS. 14 to 16, the power target generation circuit 943 calculates the power target value so as to have a drooping characteristic by using the second governor control circuit 9432 configured by a first-order system delay model and the second mass system calculation circuit 9435 to which an oscillation equation model is applied.

[0363] The output of the power target generation circuit 943 is input to a power target value control circuit 946 and a fifth control circuit 949. As shown in Fig. 49 , in the power target value control circuit 946, PI control (fourth PI control circuit 9462) is executed so that the subtraction value obtained by subtracting the measured charge / discharge power calculated by the second power calculation circuit 941 from the power target value from the power target generation circuit 943 becomes zero, thereby calculating a control command value for the first DC / DC conversion circuit 93 in the power control mode.

[0364] 9 , the first switching circuit 947 selectively outputs one of the output of the second voltage target value control circuit 945 and the output of the power target value control circuit 946 in accordance with a control signal output from the fifth control circuit 949. The fifth control circuit 949 generates a control signal for the first switching circuit 947 so as to select the output of the second voltage target value control circuit 945 when the power converter 9 is operated in the voltage control mode, and to select the output of the power target value control circuit 946 when the power converter 9 is operated in the power control mode.

[0365] The output of the first switching circuit 947 is input to a current limiting circuit 948. The current limiting circuit 948 performs current limiting when the output current of the first DC / DC conversion circuit 93 exceeds a predetermined value, and when the output current is less than the predetermined value, it outputs the first switching circuit 947 as is. Furthermore, in the first embodiment, the current command value processed by the current limiting circuit 948 is PWM modulated by a PWM modulation circuit (not shown) to generate a control command value for the first DC / DC conversion circuit 93.

[0366] Next, the detailed operation of the first DC / DC conversion circuit 93 (FIG. 6) in the power converter 9 for the distribution system storage battery will be described with reference to the flowchart of FIG.

[0367] 34, when control of the first DC / DC conversion circuit 93 is started, the fifth control circuit 949 initializes various parameters in the second control circuit 94 in S301, and initializes the power command value to "0" and the voltage command value to "1500 V" in S302. Then, the fifth control circuit 949 collects information from various voltmeters and current meters in S303, and executes control of the first DC / DC conversion circuit 93 in S304.

[0368] FIG. 35 shows a flowchart for explaining the detailed control process of the first DC / DC conversion circuit 93 in S304 of FIG.

[0369] Referring to FIG. 35 , when S304 (control of the first DC / DC conversion circuit 93) is started, the second power calculation circuit 941 reads the voltage (measurement result of the voltmeter 96) and current (measurement result of the ammeter 97) of the DC power distribution system 21 in S3041, and calculates the charge / discharge power of the DC power distribution system 21, which corresponds to the output power of the first DC / DC conversion circuit 93, in S3042.

[0370] When S3042 is completed, the fifth control circuit 949 checks in S3043 whether to operate the power converter 9 for the distribution system storage battery in the voltage control mode. In the first embodiment, the control mode of the power converter 9 is notified from the CEMS 3. That is, in S3043, it is checked whether the voltage control mode or the power control mode has been instructed by the CEMS 3.

[0371] In the voltage control mode (YES in S3043), the second voltage target generation circuit 942 generates a voltage target value for the DC power distribution system 21 based on the drooping characteristic in S3044.

[0372] 9 , in S3045, the voltage target value generated by the second voltage target generation circuit 942 is input to the second voltage target value control circuit 945 and the fifth control circuit 949. When the voltage target value is input, the second voltage target value control circuit 945 outputs a command value for the first DC / DC conversion circuit 93 to the first switching circuit 947, for setting the voltage of the DC power distribution system 21 to the voltage target value. When the voltage control mode is instructed in accordance with the control signal from the fifth control circuit 949, the first switching circuit 947 outputs the command value for the first DC / DC conversion circuit 93 output by the second voltage target value control circuit 945 to the current limiting circuit 948.

[0373] On the other hand, in the case of the power control mode (NO in S3043), the power target value (DC) of the output power of the first DC / DC conversion circuit 93 is generated by the power target generating circuit 943 in S3046 based on the drooping characteristic.

[0374] 9 , in S3047, the power target value generated by the power target generation circuit 943 is input to the power target value control circuit 946 and the fifth control circuit 949. When the power target value is input, the power target value control circuit 946 outputs a command value for the first DC / DC conversion circuit 93, the command value being the output power (charge / discharge power) of the first DC / DC conversion circuit 93 (power converter 9) for the DC power distribution system 21, to the first switching circuit 947. When the power control mode is instructed in accordance with the control signal from the fifth control circuit 949, the first switching circuit 947 outputs the command value for the first DC / DC conversion circuit 93 output by the power target value control circuit 946 to the current limiting circuit 948.

[0375] In S3048, if the output current of the first DC / DC conversion circuit 93 exceeds a predetermined current value based on the measurement result of the ammeter 97, the current limiting circuit 948 imposes a restriction to reduce the output current on the first DC / DC conversion circuit 93 (voltage control mode) from the second voltage target value control circuit 945 or the first DC / DC conversion circuit 93 (power control mode) from the power target value control circuit 946. On the other hand, if the output current of the first DC / DC conversion circuit 93 is less than the predetermined current value, the restriction is not imposed.

[0376] Furthermore, as described above, the current limiting circuit 948 performs PWM modulation on the command value of the first DC / DC conversion circuit 93 after the above processing, thereby generating a control command value for the first DC / DC conversion circuit 93. The first DC / DC conversion circuit 93 outputs a DC current controlled by the control command value.

[0377] Returning to FIG. 34 , upon completing the processing of S304, the fifth control circuit 949 checks in S305 whether a transmission request for measurement information has been received from the CEMS 3. If the transmission request has been received (YES in S305), the fifth control circuit 949 outputs the measurement information stored in memory (not shown) to the second communication interface circuit 95 in S306. Upon receiving the measurement data from the fifth control circuit 949, the second communication interface circuit 95 converts the measurement data into a predetermined format and transmits it to the CEMS 3 via the communication line 22. Upon completing transmission of the measurement data in S306, the fifth control circuit 949 proceeds to S307. Furthermore, if NO in S305, S306 is skipped and the processing proceeds to S307.

[0378] In S307, the fifth control circuit 949 checks whether control information (information such as a voltage command value and a power command value) has been received from the CEMS 3. If control information has been received (YES in S307), the fifth control circuit 949 sets the received power command value (Pref2) and voltage command value (Vref2) in a register (not shown) within the fifth control circuit 949 in S308. The fifth control circuit 949 then returns the process to S303 and continues to execute the processes from S303 onward using the power command value (Pref2) and voltage command value (Vref2) set in the register. On the other hand, if control information has not been received (NO in S307), the power command value (Pref2) and voltage command value (Vref2) are not updated, and the process returns to S303 and continues to execute the processes from S303 onward.

[0379] Next, the operation of the power converter 13 for the consumer PV will be described using Figures 7 and 10. The power converter 13 outputs DC power (generated power) output from the PV panel 12 installed in the consumer's home to the DC power distribution system 21. As described above, the power converter 13 will be described as implementing two types of control: MPPT control, which maximizes the extraction of power generated by the PV panel 12, and voltage control, which controls the output voltage of the PV panel 12 to control the amount of power generated.

[0380] 7 again, in the power converter 13 for the consumer PV, a voltmeter 131 measures the output voltage of the PV panel 12, and an ammeter 132 measures the output current from the PV panel 12. Furthermore, a voltmeter 136 measures the voltage of the DC power distribution system 21 (the output voltage of the power converter 13), and an ammeter 137 measures the output current of the power converter 13 to the DC power distribution system 21.

[0381] The DC power generated by the PV panel 12 is input to the second DC / DC conversion circuit 133. The second DC / DC conversion circuit 133 outputs the DC power to the DC power distribution system 21 based on a command value output from the third control circuit 134. The third control circuit 134 also stores in a memory (not shown) measurement data from the voltmeters 131 and 136, measurement data from the ammeters 132 and 137, and information such as the control method of the PV panel 12. This stored information is transmitted to the communication line 22 via the third communication interface circuit 135 based on a measurement data output request from the CEMS 3.

[0382] Referring again to FIG. 10, the operation of the third control circuit 134 of the power converter 13 for the customer PV will be described.

[0383] The MPPT control circuit 1341 searches for the maximum power point of the PV panel 12 based on the measurement values ​​of the voltmeter 131 and the ammeter 132 in order to extract the maximum amount of power generated by the PV panel 12. This executes maximum power point tracking control. Specifically, the MPPT control circuit 1341 generates a control command value for the second DC / DC conversion circuit 133 to control the DC voltage measured by the voltmeter 131 to a voltage corresponding to the maximum power point.

[0384] The PV voltage control circuit 1342 generates a control command value for the second DC / DC conversion circuit 133 based on the measurement value of the voltmeter 136, in order to maintain the DC voltage of the DC distribution system 21 at a predetermined target voltage.

[0385] The second switching circuit 1343 selectively outputs one of the outputs of the MPPT control circuit 1341 and the PV voltage control circuit 1342 as a control command value for the second DC / DC conversion circuit 133 in accordance with a control signal from the sixth control circuit 1344. This allows the second DC / DC conversion circuit 133 to be controlled in the MPPT mode or the voltage control mode.

[0386] For example, when the DC system voltage exceeds a predetermined value, the sixth control circuit 1344 switches the control of the PV panel 12 from MPPT control to voltage control and suppresses an increase in the voltage at the grid interconnection point (power receiving point) of the DC distribution system 21. Furthermore, when a control mode is received from the CEMS 3, or when the increase in the voltage at the grid interconnection point (power receiving point) of the DC distribution system 21 is suppressed to a predetermined voltage by voltage control and can be maintained for a predetermined time, in the first embodiment, the sixth control circuit 1344 switches the control of the PV panel 12 from voltage control to MPPT control. Note that MPPT control or voltage control is a control method for power conversion devices for photovoltaic power generation that is installed in ordinary homes.

[0387] At the end of the first embodiment, a concept for selecting a control mode for a power converter for a distribution system storage battery will be described. When configuring the DC distribution system 21, at least one converter that operates in a voltage control mode is required to manage the system voltage of the DC distribution system 21.

[0388] When selecting a converter to operate in voltage control mode, it is necessary to ensure that the converter capacity is large enough to cover the magnitude of the expected load fluctuations, etc., taking into consideration that if a load fluctuation or the like occurs, the converter operating in voltage control mode will initially supply excess or shortage of power.

[0389] Therefore, when selecting a converter to operate in voltage control mode, it is preferable to give priority to selecting a converter with a large capacity, or in the case of power converter 9, a converter with a large storage capacity of the distribution system storage battery 8 that controls charging and discharging. Note that between voltage control mode and power control mode, the transient response during fluctuations such as load fluctuations differs, and it is preferable to select the control mode for each converter by estimating the convergence value in a steady state.

[0390] Once the selection of the converters to operate in the voltage control mode has been completed in this manner, the operation modes of the remaining converters are then determined. It is not appropriate to impart a drooping characteristic to converters connected to power sources whose output power cannot be controlled (for example, PV or wind power generators). Therefore, in the first embodiment, the power converter 9 for the distribution system storage battery is given a drooping characteristic. All of the other converters (power converters 9) may be controlled in the voltage control mode, or, since the AC / DC converter 6 operates in the voltage control mode, all may be controlled in the power control mode.

[0391] The selection of the voltage control mode and the power control mode in the power converter 9 can be considered as follows.

[0392] As described above, the voltage control mode is characterized by the fact that the voltage at the grid-connection point is managed by the inverter itself, and therefore it is not possible to output a DC voltage that deviates from the voltage management range (Vmax to Vmin) of the DC distribution system 21 shown in Fig. 17. For this reason, it is not possible to adequately respond to power fluctuations that deviate from the voltage management range (Vmax to Vmin), and there is a possibility that the power converter 9 will stop due to the occurrence of an overcurrent or the like.

[0393] On the other hand, in the power control mode, the output power is limited within the range from the maximum power Pmax on the discharge side (upper limit side) to the maximum power Pmin (converter capacity) on the charge side (lower limit side) shown in Fig. 18, but the power converter 9 can continue to operate even if the voltage of the DC power distribution system 21 deviates from the voltage control range (Vmax to Vmin). However, in the power control mode, it is difficult to respond to the instantaneous supply of excess or deficiency of power when a sudden load fluctuation or the like occurs.

[0394] Therefore, in each embodiment of the present disclosure, for example, in each consumer load group 10, the control mode of each power converter 9 can be selected based on the relationship between the fluctuations in the load of the consumer load 11 and the power generation amount of the PV panel 12 in that consumer load group 10 and the converter capacity of the corresponding power converter 9 for the distribution system storage battery. Specifically, if the converter capacity of the power converter 9 is sufficiently large compared to the fluctuations in the consumer load group 10, the voltage control mode can be selected, and if not, the power control mode can be selected.

[0395] Note that the selection of the voltage control mode and the power control mode is not limited to the above. For example, when creating an operation plan in the CEMS 3, the control mode for each power converter 9 may be selected based on the result of estimating the voltage fluctuation range at the grid connection point of each power converter 9 when a load fluctuation or the like occurs from the direction and magnitude of the power flow current. In this case, the power control mode may be selected for the power converters 9 corresponding to the grid connection points where the voltage fluctuation range deviates from a predetermined range (for example, approximately ±5% of the reference voltage), while the voltage control mode may be selected for the power converters 9 corresponding to the grid connection points where the voltage fluctuation range does not exceed the predetermined range.

[0396] As described above, in the power converter management device according to the first embodiment, when creating an operation plan (power command value (Pref) and voltage command value (Vref)) for the power converter 9 for the distribution system storage battery, the power flow current is estimated using the predicted power consumption of the consumer loads 11 in the consumer load group 10 and the predicted power generation amount of the PV panels 12, and the voltage at the interconnection point of each power converter with the DC distribution system 21 is estimated based on the estimated distribution system impedance 7 and the drooping characteristics of each power converter 9, taking into account the voltage drop in the DC distribution system 21 due to the power flow current. Then, the power command value (Pref1) is generated, corrected (recreated) if necessary, so that the interconnection point voltage falls within a predetermined voltage control range. This has the effect of stably controlling the voltage at the interconnection point of each power converter 9 with the DC distribution system 21 to stay within the voltage range, and smoothly controlling the power flow even when load fluctuations or the like occur.

[0397] 23 and 24 described in the first embodiment, S102 and S107 in FIG. 23 correspond to an example of processing by the "measurement data collection unit," S1054 by the operation plan creation circuit 34 shown in FIG. 24 corresponds to an example of "formulation processing," S1057 (voltage prediction 1 at each power receiving point) corresponds to an example of "voltage estimation processing," and S1059 (review 1 of charge / discharge power of distribution system storage battery) corresponds to an example of "correction processing."

[0398] In the first embodiment, a configuration example ( FIG. 1 ) has been described in which the DC distribution system 21 is connected to the AC distribution system 20b via the AC / DC converter 6. However, it will be noted that similar control can be applied to achieve similar effects even when an AC main system experiences a power outage and the DC distribution system 21 is disconnected from the AC main system using the switch 5 to form an independent system. In the case of forming an independent system, the DC voltage of the DC distribution system 21 can be managed by operating at least one power converter 9 other than the AC / DC converter 6 in a voltage control mode.

[0399] Furthermore, if at least one of the power converters 9 installed in the DC distribution system 21 is configured to operate in voltage control mode, there is an effect that the DC distribution system 21 can transition to an isolated system without momentary interruption even if the main system experiences a power outage due to an accident or the like. That is, if the DC distribution system 21 is paralleled off and separated from the main system using the switch 5 immediately after a fault is detected, the DC distribution system 21 can maintain the distribution system voltage using the power converter 9 operating in the voltage control mode. Note that when transitioning to an isolated system, the AC / DC converter 6 can be controlled to be separated from the DC distribution system 21 by a gate block or a DC switch (not shown).

[0400] Furthermore, in the power converter management device according to the first embodiment, by providing each of the AC / DC converter 6 and the power converter 9 (each converter) with a power-voltage drooping characteristic (voltage control mode) or a voltage-power drooping characteristic (power control mode), it is possible to apply a virtual inertial force to the DC power distribution system 21. As a result, even when a load fluctuation or a fluctuation in the amount of power generated by an energy generating device such as a renewable energy device occurs, the converters having the drooping characteristic can operate independently and cooperatively without mutual information exchange to supply excess or shortage of power due to the fluctuation, thereby making it possible to maintain the voltage of the DC power distribution system 21 within an appropriate range.

[0401] Furthermore, by appropriately arranging distributed power sources capable of controlling output power, such as each power converter 9 controlled by a power-voltage drooping characteristic (voltage control mode: FIG. 17) or a voltage-power drooping characteristic (power control mode: FIG. 18), it becomes possible to supply excess or shortage of power to the DC power distribution system 21 when a load fluctuation or the like occurs, without concentrating the power in one distributed power source.

[0402] Embodiment 2 In the first embodiment, an example has been described in which, when creating an operation plan (power command value (Pref) and voltage command value (Vref)) for the AC / DC converter 6 and the power converter 9 (each converter) for the distribution system storage battery, the power command value (Pref) is generated with correction to bring the interconnection point voltage (estimated value) of each power converter 9 with the DC distribution system 21, which is estimated based on the estimated results of the power flow current and the impedance of the DC distribution system 21 and the drooping characteristics of each power converter 9, into a predetermined voltage control range.

[0403] In the second embodiment, a control example for achieving the same effect by modifying the voltage command value (Vref) instead of the power command value (Pref) will be described. Hereinafter, the second embodiment will be described, focusing on the operation of the parts that differ from the first embodiment (the operation of the CEMS 3). In the second embodiment, only the operation of creating (including modifying) an operation plan (power command value (Pref) and voltage command value (Vref)) of the CEMS 3 differs from the first embodiment, and therefore the operation of the CEMS 3 will be described, focusing on the operation of creating the operation plan. In other words, the circuit configurations (FIGS. 2 to 16, 47A to 49, etc.) of the CEMS 3, the AC / DC converter 6, the power converter 9, and the power converter 13 for the customer PV will not be described again.

[0404] Next, detailed operations of the CEMS 3 as a management device for the power converter according to the second embodiment will be described with reference to FIGS. 2 to 4 and 36 to 41B.

[0405] FIG. 36 is a flowchart illustrating a control process of the CEMS 3 shown in FIG. 1 as a management device for power converters according to the second embodiment.

[0406] 36, when processing starts, the operation plan creation circuit 34 in the CEMS 3 executes steps S101 to S104 similar to those in FIG. 23. As a result, when a measurement data output request is received from the DSO 2 (YES determination in S101), data for the most recent 30 minutes is collected for the AC / DC converter 6, the power converters 9a to 9n for the distribution system storage batteries, and the consumer load groups 10a to 10n in steps S102 and S103, and transmitted to the DSO 2 (S103). At this time, as in the first embodiment, the amounts of power generated by the PV panels 12a to 12n and the amounts of charge and discharge power of the distribution system storage batteries 8a to 8n are calculated, and information such as the SOC and SOH of the distribution system storage batteries 8a to 8n is also transmitted to the DSO 2. Furthermore, the collected measurement data is used to update the power generation amount prediction database 351 for the PV panels 12a to 12n and the power consumption prediction database 352 for the consumer loads 11a to 11n in the operation plan creation circuit 34.

[0407] Then, when the operation plan creation circuit 34 has received the demand plan notification from the DSO 2 (YES determination in S104), the operation plan creation circuit 34 executes creation of an operation plan according to the second embodiment in S120 (creation of operation plan 2). Note that in the second embodiment, as in the first embodiment, the DSO 2 notifies the CEMS 3 of a supply and demand plan for power supplied from the main grid to the DC distribution grid 21 at 30-minute intervals for 24 hours.

[0408] FIG. 37 shows a flowchart illustrating the details of the control process of S120 (operation plan creation 2) in FIG.

[0409] As shown in Fig. 37, when the process of operation plan creation 2 (S120) is started, the CEMS 3 (operation plan creation circuit 34) executes the processes of S1051 to S1056 similar to those in Fig. 24. As a result, similar to the first embodiment, a demand plan is created based on the predicted amounts of power generation of the PV panels 12a to 12n and the predicted amounts of power consumption of the consumer loads 11a to 11n (S1051 to S1053), and the charge / discharge power of the distribution system storage batteries 8a to 8n is determined (S1054).

[0410] Furthermore, similarly to the first embodiment, the impedances of the distribution system impedances 7a to 7n are estimated (S1055), and the power flow current in the DC distribution system 21 is calculated (S1056). Specifically, the power flowing through each of the distribution system impedances 7a to 7n is calculated from the result of the estimation of the excess or shortage of power in each consumer load group 10 calculated in S1054, the charging / discharging power (Pref) from each power converter 9, and the demand power (Pref) supplied from the AC / DC converter 6, and a current value is calculated from the result of the power calculation using the impedance estimation results of the distribution system impedances 7a to 7n.

[0411] When the operation plan creation circuit 34 completes the calculation of the power flow current in S1056, it executes the process of "Each receiving point voltage prediction 2" in S1060 to predict the voltage value of the interconnection point (receiving point) of each power converter 9 with the DC distribution system 21.

[0412] FIG. 38 shows a flowchart illustrating the detailed control process of S1060 (each receiving point voltage prediction 2) in FIG.

[0413] 38 , when the flow of each power receiving point voltage prediction 2 (S1060) starts, the power flow current estimation circuit 347 collects power command value (Pref) and voltage command value (Vref) information of the power converters 9a to 9n in S10601X in accordance with an instruction from the operation plan creation unit management circuit 346 in the operation plan creation circuit 34. When the collection of the power command value (Pref) and voltage command value (Vref) information in S10601X is completed, the operation plan creation unit management circuit 346 instructs the power flow current estimation circuit 347 in S10571 to read out drooping characteristic information of the AC / DC converter 6 (via the operation plan creation unit management circuit 346) from the memory circuit 32.

[0414] Furthermore, upon completion of S10571, the power flow current estimation circuit 347 collects, in S10605X, power command value information (Pref) and voltage command value information (Vref) for the AC / DC converter 6 in accordance with instructions from the operation plan creation unit management circuit 346. Upon completion of S10605X, the power flow current estimation circuit 347 calculates, in S10573 similar to that of FIG. 26 , the output voltage (DC voltage value) of the AC / DC converter 6 based on the drooping characteristic of the AC / DC converter 6 collected in S10571 and the power command value and voltage command value of the AC / DC converter 6 collected in S10605X. Note that, in the second embodiment as well, as in the first embodiment, the description will continue assuming that the output voltage of the AC / DC converter 6 is the reference voltage (1500 V).

[0415] When the processing of S10573 is completed, the power flow current estimation circuit 347 selects the power converter 9a located immediately downstream of the AC / DC converter 6 in S10574 similar to that in FIG.

[0416] Next, in S10575, the power flow current estimation circuit 347 collects drooping characteristic information of the first DC / DC conversion circuit 93 in the power converter 9 selected in S10574 or the subsequent S10581. Specifically, the power flow current estimation circuit 347 reads out the drooping characteristic information from the memory circuit 32 via the operation plan creation unit management circuit 346. Note that the two types of drooping characteristics possessed by the first DC / DC conversion circuit 93 in the power converter 9 are the same as those in the first embodiment, and therefore description thereof will not be repeated.

[0417] In S10606X, the power flow current estimation circuit 347 collects the voltage command value (Vref) and power command value (Pref) of the selected DC / DC converter. After S10606X is completed, S10577 to S10579, which are similar to those in FIG. 26 , are executed. As a result, the power flow current estimation circuit 347 estimates the power flow current and outputs the estimation result to the grid voltage estimation circuit 348. The grid voltage estimation circuit 348 calculates the voltage drop at the grid interconnection point (power receiving point) of the selected power converter 9 with the DC distribution grid 21 based on the estimation result of the power flow current and the estimation result of the impedances of the distribution grid impedances 7a to 7n estimated in S1055 (see FIG. 37 ) (S10577). Then, based on this voltage drop, the output voltage of the first DC / DC conversion circuit 93 in the selected power converter 9, i.e., the interconnection point voltage with the DC distribution system 21, is calculated, and the calculation result is output to the operation plan creation unit management circuit 346 (S10578).

[0418] Furthermore, the interconnection point voltage calculated in S10578 and the drooping characteristic information collected in S10575 are used to calculate the charge / discharge power output from the first DC / DC conversion circuit 93 in the selected power converter 9. Then, based on the calculated charge / discharge power, the calculation result of the power flow current of the DC distribution system 21 is corrected (S10579).

[0419] When the processing of S10579 is completed, the operation plan creation unit management circuit 346 checks whether estimation of the output voltages of the first DC / DC conversion circuits 93 for all power converters 9 is completed in S10580 similar to that of Fig. 26 . If estimation of the output voltages of the first DC / DC conversion circuits 93 for all power converters 9 is not completed (NO in S10580), a new power converter 9 located one step downstream from the currently selected power converter 9 is selected in S10581 similar to that of Fig. 26 , and the processing returns to S10575. For example, if S10581 is executed when power converter 9a has been selected in S10574, a new power converter 9b is selected, and the processing of S10575 to S10580 is executed.

[0420] Therefore, until the most downstream power converter 9n (FIG. 9) is selected and the processes of S10575 to S10580 are executed, a NO determination is made in S10580, and the processes of S10575, S10606X, and S10577 to S10580 are repeated. When estimation of the output voltage of the first DC / DC conversion circuit 93 for all power converters 9 is completed, a YES determination is made in S10580, and the operation plan creation unit management circuit 346 ends the process of S1060 (each power receiving point voltage prediction 2).

[0421] Returning to Figure 37, when the operation plan creation unit management circuit 346 completes S1060 (each receiving point voltage prediction 2), it checks, using S1058 similar to Figure 24, whether all receiving point voltages predicted in S1060 are within the same voltage control range as in embodiment 1 (the range of Vrange_max to Vrange_min in Figure 19).

[0422] If the judgment in S1058 is NO, that is, if any of the estimated values ​​of the interconnection point voltage (receiving point voltage) of the AC / DC converter 6 and the power converter 9 with the DC distribution system 21 is outside the above-mentioned voltage control range, the operation plan creation unit management circuit 346 proceeds to S1065 and revises the voltage command values ​​of the AC / DC converter 6 and the distribution system storage battery 8.

[0423] 39A and 39B show a flowchart illustrating the detailed control process for reviewing the voltage command value for the distribution system storage battery 8 in S1065 (FIG. 37).

[0424] Referring to Figure 39A, when S1065 is started, the operation plan creation unit management circuit 346 detects, in S10651, the maximum value (Vp_max) of the predicted values ​​of the interconnection point voltages between the AC / DC converter 6 and each power converter 9 (each converter) and the DC distribution system 21, which were predicted in S1060.

[0425] Similarly, in S10652, the operation plan creation unit management circuit 346 detects the minimum value (Vp_min) of the predicted values ​​of the interconnection point voltages between the AC / DC converter 6 and each power converter 9 (each converter) and the DC distribution system 21, which were predicted in S1060.

[0426] In S10653, the operation plan creation unit management circuit 346 uses Vp_max and Vp_min detected in S10651 and S10652 to determine whether the estimated interconnection point voltage deviates from the lower limit voltage side of the voltage control range.

[0427] In the second embodiment, in the case where there are both converters whose interconnection point voltage (estimated value) with the DC distribution system 21 exceeds the control upper limit voltage and converters whose interconnection point voltage is below the control lower limit voltage, after S10653 is judged as YES, the interconnection point voltage of the converter that detected Vp_max is set as the control upper limit voltage (Vrange_max), and the interconnection point voltages of the other converters are corrected to "estimated value - (Vp_max - Vrange_max)", and processing from S10654 onwards is performed.

[0428] In addition, in the second embodiment, for the sake of simplicity, it is assumed that the power flow in the DC distribution system 21 is maintained smoothly (current flows from the AC / DC converter 6 toward the power converter 9n) or reversely (current flows from the power converter 9n toward the AC / DC converter 6).

[0429] If the determination in S10653 is YES, the operation plan creation unit management circuit 346 checks whether there is a converter whose interconnection point voltage (estimated value) with the DC distribution system 21 exceeds the control upper limit voltage, and if there is a converter whose control upper limit voltage is exceeded, executes the above-mentioned correction process (processing in which the interconnection point voltage of the converter that detected Vp_max is set as the control upper limit voltage (Vrange_max), and the interconnection point voltages of the other converters are corrected to "estimated value - (Vp_max - Vrange_max)"). Then, in S10654, it is checked whether the power flow in the DC distribution system 21 is forward.

[0430] If the current is in-flow (YES in S10654), the operation plan creation unit management circuit 346 selects, in S10655, the DC / DC converter (power converter 9n) that is located furthest downstream in the power flow current from among all the converters (AC / DC converter 6 and power converters 9a to 9n). In S10656, the operation plan creation unit management circuit 346 sets the voltage command value of the converter selected in S10655 in accordance with the lower limit voltage (control lower limit voltage) Vrange_min of the voltage control range. For example, using a constant ζ, the voltage command value is set to "Vrange_min + ζ".

[0431] For example, in the second embodiment, the constant ζ can be calculated as ζ={(Vrange_max-Vrange_min)-(Vp_max-Vp_min)} / 2''.

[0432] After completing S10656, the operation plan creation unit management circuit 346 selects the converter (power converter 9m in this example) immediately upstream of the terminal converter (power converter 9n) in S10657. Furthermore, the operation plan creation unit management circuit 346 calculates the voltage drop (ΔVdiff) based on the power flow current prediction result in S10658. Specifically, if the grid-tie point voltage of the currently selected kth converter is Vp(k) and the grid-tie point voltage of the (k-1)th converter selected immediately before (i.e., immediately downstream) is Vp(k-1), ΔVdiff can be calculated as ΔVdiff=Vp(k)-Vp(k-1).

[0433] When the operation plan creation unit management circuit 346 completes S10658, in S10659, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., the one downstream).

[0434] Then, in S10660, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10659 exceeds the upper limit voltage of the voltage control range (control upper limit voltage Vrange_max). If the voltage command value exceeds the control upper limit voltage (YES determination in S10660), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control upper limit voltage Vrange_max in S10661. Note that, in the second embodiment, an example is described in which, when YES determination is made in S10660, the voltage command value is limited to the control upper limit voltage Vrange_max in S10661; however, the processing of S10660 and S10661 may be omitted without executing this limitation.

[0435] If the determination result in S10660 is NO, or after the completion of S10661, the operation plan creation unit management circuit 346 checks in S10662 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) has been completed. If the correction has been completed (if the determination result in S10662 is YES), the process of reviewing the voltage command value of the distribution system storage battery 8 (S1065: FIG. 37) is terminated, as shown in FIG. 39B.

[0436] On the other hand, if the determination in S10662 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately upstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10663, and returns the process to S10658. As a result, the processes of S10658 to S10662 are executed for the newly selected converter. The processes of S10658 to S10662 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a YES determination is made in S10662.

[0437] Returning to S10654 in FIG. 39A , when the power flow is reverse (NO in S10654), the operation plan creation unit management circuit 346 selects, in S10675, the AC / DC converter 6 that is located furthest downstream in the power flow current among all the converters (the AC / DC converter 6 and the power converters 9a to 9n). After completing S10675, the operation plan creation unit management circuit 346 sets, in S10676, the voltage command value of the converter (AC / DC converter 6) selected in S10675 in accordance with the control lower limit voltage Vrange_min. For example, using a constant η, the voltage command value is set to "Vrange_min + η."

[0438] For example, in the second embodiment, η can be calculated as follows: η={(Vrange_max-Vrange_min)-(Vp_max-Vp_min)} / 2. In this way, the constants ζ and η can be the same value, but they can also be different values.

[0439] When the operation plan creation unit management circuit 346 finishes S10676, it selects the converter (power converter 9a) immediately downstream of the AC / DC converter 6 in S10677, and calculates the voltage drop (ΔVdiff) based on the power flow current prediction result in S10678. Specifically, if the grid-tied point voltage of the currently selected kth converter is Vp(k) and the grid-tied point voltage of the previously selected (k-1)th converter, i.e., the converter located immediately upstream, is Vp(k-1), then ΔVdiff can be calculated as ΔVdiff=Vp(k)-Vp(k-1).

[0440] When the operation plan creation unit management circuit 346 completes S10678, in S10679, similar to S10659, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., one step upstream).

[0441] Then, in S10680, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10679 exceeds the upper limit voltage of the voltage control range (control upper limit voltage Vrange_max). If the voltage command value exceeds the control upper limit voltage (YES determination in S10680), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control upper limit voltage Vrange_max in S10681. Note that the processes of S10680 and S10681 can also be omitted, similar to S10660 and S10661.

[0442] If the determination result in S10680 is NO, or after the completion of S10681, the operation plan creation unit management circuit 346 checks in S10682 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) has been completed. If the correction has been completed (if the determination result in S10682 is YES), the process of reviewing the voltage command value of the distribution system storage battery 8 (S1065: FIG. 37) is terminated, as shown in FIG. 39B.

[0443] On the other hand, if the determination in S10682 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately downstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10683, and returns the process to S10678. As a result, the processes of S10678 to S10682 are executed for the newly selected converter. The processes of S10678 to S10682 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a determination of YES is made in S10682.

[0444] Returning to S10653 in Figure 39A, if the deviated interconnection point voltage does not deviate from the lower limit voltage side of the voltage control range (i.e., the control lower limit voltage Vrange_min) (when S10653 is judged as NO), the operation plan creation unit management circuit 346 proceeds to S10693 in Figure 39B.

[0445] In S10693, the operation plan creation unit management circuit 346 determines whether Vp_max and Vp_min detected in S10651 and S10652 deviate from the upper limit voltage side of the voltage control range (control upper limit voltage Vrange_max). If the determination in S10693 is NO, both Vp_max and Vp_min are within the voltage control range (Vrange_max to Vrange_min), so the operation plan creation unit management circuit 346 determines that it is not necessary to modify the voltage command value and ends the process of reviewing the voltage command value for the distribution system storage battery 8 (S1065: FIG. 37 ).

[0446] On the other hand, if the determination in S10693 is YES, the operation plan creation unit management circuit 346 checks in S10694 whether the power flow in the DC distribution system 21 is forward.

[0447] If the current is in-flow (YES in S10694), the operation plan creation unit management circuit 346 selects, in S10695, the AC / DC converter 6 that is located most upstream in the flow current among all the converters (AC / DC converter 6 and power converters 9a to 9n).

[0448] After completing S10695, the operation plan creation unit management circuit 346 sets the voltage command value of the converter (AC / DC converter 6) selected in S10695 in accordance with the control upper limit voltage Vrange_max in S10696. For example, using the same constant η as in S10676 in Fig. 39A, the voltage command value is set to "Vrange_max - η".

[0449] When the operation plan creation unit management circuit 346 finishes S10696, in S10697, it selects the converter (power converter 9a) immediately downstream of the AC / DC converter 6, and in S10698, it calculates the voltage drop (ΔVdiff) based on the power flow current prediction result. Specifically, if the grid-tie point voltage of the currently selected kth converter is Vp(k) and the grid-tie point voltage of the (k-1)th converter selected immediately before (i.e., immediately upstream) is Vp(k-1), then ΔVdiff can be calculated as Vp(k) - Vp(k-1).

[0450] When the operation plan creation unit management circuit 346 completes S10698, in S10699, similar to S10659, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., one step upstream).

[0451] Then, in S10700, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10699 is less than the lower limit voltage (control lower limit voltage) Vrange_min of the voltage control range. If the voltage command value is less than the control lower limit voltage (YES determination in S10770), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control lower limit voltage Vrange_min in S10701. Note that the processes of S107000 and S10701 can also be omitted, similar to S10680 and S10681.

[0452] If the determination in S107000 is NO, or after the completion of S10701, the operation plan creation unit management circuit 346 checks in S10702 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) has been completed. If the correction has been completed (if the determination in S10702 is YES), the process of reviewing the voltage command value of the distribution system storage battery 8 (S1065: FIG. 37) is terminated.

[0453] On the other hand, if the determination in S10702 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately downstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10703, and returns the process to S10698. As a result, the processes of S10698 to S10702 are executed for the newly selected converter. The processes of S10698 to S10702 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a determination of YES is made in S10702.

[0454] Returning to S10694, if the power flow is reverse (NO in S10694), the operation plan creation unit management circuit 346 selects the DC / DC converter (power converter 9n) located most upstream of the power flow current in S10715. In S10716, the operation plan creation unit management circuit 346 sets the voltage command value of the converter selected in S10715 in accordance with the upper limit voltage of the voltage control range (control upper limit voltage Vrange_max). For example, using the same constant ζ as in S10656 of FIG. 39A, the voltage command value is set to "Vrange_max - ζ".

[0455] After completing S10716, the operation plan creation unit management circuit 346 selects the converter (power converter 9m in this example) immediately upstream of the terminal converter (power converter 9n) in S10717. Furthermore, the operation plan creation unit management circuit 346 calculates a voltage drop (ΔVdiff) based on the power flow current prediction result in S10718. Specifically, ΔVdiff can be calculated in the same manner as in S10568 of FIG. 39A .

[0456] When the operation plan creation unit management circuit 346 completes S10718, in S10719, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., the one downstream).

[0457] Then, in S10720, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10719 is less than the lower limit voltage (control lower limit voltage) Vrange_min of the voltage control range. If the voltage command value is less than the control lower limit voltage (YES determination in S10720), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control lower limit voltage Vrange_min in S10721. Note that the processes of S10720 and S10721 can also be omitted.

[0458] If the determination in S10720 is NO, or after the completion of S10721, the operation plan creation unit management circuit 346 checks in S10722 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed. If the correction is completed (if the determination in S10722 is YES), the process of reviewing the voltage command value of the distribution system storage battery 8 (S1065: FIG. 37) is terminated.

[0459] On the other hand, if the determination in S10722 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately upstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10723, and returns the process to S10718. As a result, the processes in S10718 to S10722 are executed for the newly selected converter. The processes in S10718 to S10722 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a YES determination is made in S10722.

[0460] In this way, the voltage command values ​​of the converters (AC / DC converter 6 and power converters 9a to 9n) are corrected for each combination of the YES / NO judgment of S10653 in Figure 39A and the direction of the current (S10654, S10694).

[0461] 37 , the operation plan creation unit management circuit 346 executes the processes of S1056, S1060, and S1058 using the power command value corrected in S1065 (reviewing the voltage command value for the distribution system battery 8). The correction of the voltage command value for each converter (AC / DC converter 6 and power converters 9a to 9n) in S1065 (reviewing the voltage command value for the distribution system battery 8) is repeatedly executed until a YES determination is made in S1058. Then, when the voltage command values ​​for each converter (AC / DC converter 6 and power converters 9a to 9n) are set so that the estimated values ​​of the interconnection point voltages (power receiving point voltages) of each converter with the DC distribution system 21 are all within the voltage control range, the "operation plan creation 2" in S120 ( FIG. 36 ) is terminated.

[0462] Returning to Figure 36, when operation plan creation 2 in S120 is completed, the operation plan creation unit management circuit 346 outputs the operation plan (power command values, voltage command values, etc.) created in S120 to the transmission data generation circuit 35 (see Figure 2) in S110, and notifies the distributed power source management unit control circuit 36 ​​of this.

[0463] Upon receiving the notification, the distributed power source management control circuit 36 ​​instructs the communication circuit 31 to transmit an operation plan. When the communication circuit 31 completes transmission of the operation plan (voltage command values, power command values, etc.) to all the distributed power sources, the distributed power source management control circuit 36 ​​notifies the operation plan creation unit management circuit 346 in the operation plan creation circuit 34 of that effect.

[0464] On the other hand, if the operation plan creation circuit 34 has not received an operation plan creation request (24-hour supply and demand plan) from the DSO 2 in S104 (NO in S104), it checks in S106 whether it is the time to collect various measurement results, specifically, whether it is the start time of the 5-minute periodic processing in Fig. 22. If it is not the collection time (NO in S106), the process returns to S101 and continues.

[0465] On the other hand, if it is the collection time (YES in S106), the operation plan creation circuit 34 instructs the transmission data generation circuit 35 to generate a measurement data output request packet in S107, which requests the connected devices (AC / DC converter 6, power converters 9a-9n, consumer loads 11a-11n, and consumer PV power converters 13a-13n) of the DC distribution system 21 to transmit measurement data. Then, when all the measurement data has been collected, the operation plan creation unit management circuit 346 instructs the power generation amount prediction circuit 342 and the power consumption prediction circuit 343 via the battery operation plan creation circuit 341 to update the power generation amount prediction database 351 and the power consumption prediction database 352 based on the collected measurement data. The processing content of S107 is the same as that in the first embodiment, and therefore will not be described again.

[0466] Upon completing the process of S107, the operation plan creation unit management circuit 346 checks the collected measurement data and determines whether or not the operation plan needs to be modified in S108. The details of the determination in S108 are the same as those in the first embodiment, and therefore detailed description will not be repeated.

[0467] If the operation plan creation unit management circuit 346 determines NO in S108, that is, if it determines that the operation plan does not need to be modified, it returns to S101 and continues to execute the subsequent processes.

[0468] On the other hand, when it is determined that the operation plan needs to be modified (YES in S108), the operation plan creation unit management circuit 346 executes "Modification 2 of operation plan" in S125.

[0469] 40A and 40B show a flowchart illustrating the detailed control process of "Modification 2 of operation plan" in S125 (FIG. 36).

[0470] 40A , when S125 starts, the operation plan creation unit management circuit 346 collects the output voltage and actual power measurement values ​​of each converter (AC / DC converter 6 and power converters 9 a to 9 n) in S10921. When S10921 ends, the operation plan creation unit management circuit 346 executes S10902 to S10907 similar to those in FIG. 29A .

[0471] As a result, in S10902, the estimation result of the distribution system impedances 7a to 7n (the result estimated in S1054 in FIG. 24) is read out. Furthermore, in S10903, the converters (AC / DC converter 6 and / or power converter 9) for which the operation plan correction flag (FIGS. 28A and 28B) is set are extracted. Furthermore, in S10904, it is confirmed whether the output power of the AC / DC converter 6 is within a predetermined range centered on the power demand notified by the DSO 2, and in S10905, the power command values ​​of the distribution system storage batteries 8a to 8n are corrected. The processing of S10905 is the same as in the first embodiment, and therefore detailed description thereof will not be repeated.

[0472] When correction 1 of the power command value for the distribution system storage battery 8 in S10905 is completed, the operation plan creation unit management circuit 346 calculates the power flow current of the DC distribution system 21 based on the actual measurement data in S10906. In S10906, as in the first embodiment, the power command value newly generated in S10905 can be used to calculate the power flow current using the output power of the AC / DC converter 6, the charge / discharge power of the power converters 9a to 9n, the actual measured values ​​of the power consumption of the consumer loads 11a to 11n, and the actual measured values ​​of the power generation power of the PV panels 12a to 12n.

[0473] As in the first embodiment, when the determination in S10904 is YES, or after the processing of S10905 and S10906 is completed when the determination in S10904 is NO, the operation plan creation unit management circuit 346 selects the power converter 9a installed downstream of the AC / DC converter 6 in S10907, and proceeds to S10908 in FIG. 40B.

[0474] 29B , and whether the SOC of the distribution system storage battery 8 selected in S10907 is within a predetermined range is confirmed in the same manner as in the first embodiment. If the SOC is outside the predetermined range, the power command value is corrected based on the SOC in S10909, which is the same as in the first embodiment. Note that the content of the process of correcting the power command value based on the SOC in S10909 is the same as in the first embodiment, and therefore detailed description thereof will not be repeated.

[0475] When S10909 is completed or when the determination result of S10908 is YES, the operation plan creation unit management circuit 346 executes S10910 and S10911 similar to those of the first embodiment ( FIG. 29B ). As a result, when confirmation of the SOCs of all the distribution system storage batteries 8 a to 8 n by S10908 and S10909 is completed, the determination result of S10910 is YES, and the process proceeds to S10912.

[0476] The operation plan creation unit management circuit 346 calculates (estimates) the power flow current of the DC power distribution system 21 using the corrected power command values ​​of the AC / DC converter 6 and the power converters 9a to 9n in S10912, as in the first embodiment (FIG. 29B). Furthermore, when the operation plan creation unit management circuit 346 finishes calculating (estimating) the power flow current in S10912, it executes in S1060 a voltage prediction 2 for each power receiving point, as in FIG. 37. In S1060, the control processing in FIG. 38, which has already been described, is executed.

[0477] When the operation plan creation unit management circuit 346 completes the voltage prediction for each power receiving point in S1060, it checks in S10913 whether all power receiving point voltages predicted in S1060 are within the voltage control range (the range of Vrange_max to Vrange_min in FIG. 19 ). If all interconnection point (power receiving point) voltages are within the voltage control range (YES in S10913), the operation plan correction 2 (S125) process ends.

[0478] In contrast, when S10913 is judged as NO, that is, when the estimated value of any interconnection point voltage (receiving point voltage) is outside the above-mentioned voltage control range, the operation plan creation unit management circuit 346 proceeds to S10925 and executes processing for reviewing the voltage command value 2 of the distribution system storage battery 8.

[0479] 41A and 41B show a flowchart illustrating detailed control processing of review 2 of the voltage command value for the distribution system storage battery 8 in S10925 (FIG. 40B).

[0480] Referring to FIG. 41A , when S10925 is started, the operation plan creation unit management circuit 346 detects the maximum value (Vp_max) of the actually measured interconnection point voltages (actual measured values) of the AC / DC converter 6 and each power converter 9 (each converter) with the DC distribution system 21 in S109251.

[0481] Similarly, in S109252, the operation plan creation unit management circuit 346 detects the minimum value (Vp_min) of the actually measured voltages (actual measured values) at the interconnection points of the AC / DC converter 6 and each power converter 9 (each converter) with the DC distribution system 21.

[0482] In S10653, the operation plan creation unit management circuit 346 uses Vp_max and Vp_min detected in S109251 and S109252 to determine whether the interconnection point voltage (actual measurement value) deviates from the lower limit voltage side of the voltage control range.

[0483] In the process of reviewing the voltage command value 2 of the distribution system battery 8 (FIGS. 41A and 41B), similar to the process of reviewing the voltage command value of the distribution system battery 8 shown in FIGS. 39A and 39B, if there are converters whose interconnection point voltage with the DC distribution system 21 exceeds the upper limit voltage and converters whose interconnection point voltage is below the lower limit voltage, the voltage of the converter that detected Vp_max is set as the upper limit voltage (Vrange_max), and the interconnection point voltages of the other converters with the DC distribution system 21 are corrected to “estimated value−(Vp_max−Vrange_max)”, and the process from S10654 onwards is performed.

[0484] In addition, in the second embodiment, for the sake of simplicity, it is assumed that the power flow in the DC distribution system 21 is normal (current flows from the AC / DC converter 6 toward the power converter 9n) or reverse (current flows from the power converter 9n toward the AC / DC converter 6).

[0485] If the determination in S10653 is YES, the operation plan creation unit management circuit 346 checks whether there is a converter whose interconnection point voltage (estimated value) with the DC distribution system 21 exceeds the control upper limit voltage, and if there is a converter whose control upper limit voltage is exceeded, executes the above-mentioned correction process (processing in which the interconnection point voltage of the converter that detected Vp_max is set as the control upper limit voltage (Vrange_max), and the interconnection point voltages of the other converters are corrected to "estimated value - (Vp_max - Vrange_max)"). Then, in S10654, it is checked whether the power flow in the DC distribution system 21 is forward.

[0486] If the current is in-flow (YES in S10654), the operation plan creation unit management circuit 346 selects, in S10655, the DC / DC converter (power converter 9n) that is located furthest downstream in the power flow current from among all the converters (AC / DC converter 6 and power converters 9a to 9n). After completing S10655, the operation plan creation unit management circuit 346 sets, in S10656, the voltage command value of the converter selected in S10655 in accordance with the lower limit voltage (control lower limit voltage) Vrange_min of the voltage control range. For example, using the constant ζ, the voltage command value is set to "Vrange_min+ζ". As described above, in the second embodiment, the constant ζ can be calculated as ζ={(Vrange_max-Vrange_min)-(Vp_max-Vp_min)} / 2".

[0487] After completing S10656, the operation plan creation unit management circuit 346 selects the converter (power converter 9m in this example) immediately upstream of the terminal converter (power converter 9n) in S10657, and then calculates the voltage drop (ΔVdiff) based on the measured grid tie point voltage result in S109253. Specifically, if the grid tie point voltage of the currently selected kth converter is Vp(k) and the grid tie point voltage of the (k-1)th converter selected immediately before (i.e., immediately downstream) is Vp(k-1), then ΔVdiff can be calculated as ΔVdiff=Vp(k)-Vp(k-1).

[0488] When the operation plan creation unit management circuit 346 completes S109253, in S10659, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected immediately before (i.e., the converter one downstream).

[0489] Then, in S10660, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10659 exceeds the upper limit voltage of the voltage control range (control upper limit voltage Vrange_max). If the voltage command value exceeds the control upper limit voltage (YES determination in S10660), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control upper limit voltage Vrange_max in S10661. Note that, in the second embodiment, an example is described in which, when YES determination is made in S10660, the voltage command value is limited to the control upper limit voltage Vrange_max in S10661; however, the processing of S10660 and S10661 may be omitted without executing this limitation.

[0490] If the determination result in S10660 is NO, or after the completion of S10661, the operation plan creation unit management circuit 346 checks in S10662 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is complete. If the correction is complete (if the determination result in S10662 is YES), the process of reviewing the voltage command value 2 of the distribution system storage battery 8 (S10925: FIG. 40B) is terminated, as shown in FIG. 41B.

[0491] On the other hand, if the determination in S10662 is NO, the operation plan creation unit management circuit 346 selects a new converter one upstream of the currently selected converter (AC / DC converter 6 or power converter 9) selected in S10657 or S10663, and returns the process to S10923. As a result, the processes of S10923 to S10662 are executed for the newly selected converter. The processes of S10923 to S10662 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a determination of YES is made in S10662.

[0492] Returning to S10654, if the power flow is reverse (NO in S10654), the operation plan creation unit management circuit 346 selects, in S10675, the AC / DC converter 6 located furthest downstream in the power flow current from among all converters (the AC / DC converter 6 and the power converters 9a to 9n). After completing S10675, the operation plan creation unit management circuit 346 sets, in S10676, the voltage command value of the converter (AC / DC converter 6) selected in S10675 in accordance with the control lower limit voltage Vrange_min. For example, using the constant η, the voltage command value is set to "Vrange_min + η." As described above, in the second embodiment, η can be calculated as η = {(Vrange_max - Vrange_min) - (Vp_max - Vp_min)} / 2. In this way, the constants ζ and η can be the same value, but they can also be different values.

[0493] When the operation plan creation unit management circuit 346 finishes S10676, in S10677, it selects the converter (power converter 9a) immediately downstream of the AC / DC converter 6, and in S109254 calculates the voltage drop (ΔVdiff) based on the measured grid tie point voltage. Specifically, if the grid tie point voltage of the currently selected kth converter is Vp(k) and the grid tie point voltage of the (k-1)th converter selected immediately before, i.e., located immediately upstream, is Vp(k-1), then ΔVdiff = Vp(k) - Vp(k-1) can be calculated based on the measured grid tie point voltage.

[0494] When the operation plan creation unit management circuit 346 completes S109524, it calculates the voltage command value (Vref(k)) of the kth converter described above in S10679 as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., the one upstream).

[0495] Then, in S10680, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10679 exceeds the upper limit voltage of the voltage control range (control upper limit voltage Vrange_max). If the voltage command value exceeds the control upper limit voltage (YES determination in S10680), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control upper limit voltage Vrange_max in S10681. Note that the processes of S10680 and S10681 can also be omitted, similar to S10660 and S10661.

[0496] If the determination result in S10680 is NO, or after the completion of S10681, the operation plan creation unit management circuit 346 checks in S10682 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is complete. If the correction is complete (if the determination result in S10682 is YES), the process of reviewing the voltage command value 2 of the distribution system storage battery 8 (S10925: FIG. 40B) is terminated, as shown in FIG. 41B.

[0497] On the other hand, if the determination in S10682 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately downstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10683, and returns the process to S109254. As a result, the processes of S109254 to S10682 are executed for the newly selected converter. The processes of S109254 to S10682 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a determination of YES is made in S10682.

[0498] Returning to S10653, if the deviated interconnection point voltage does not deviate from the lower limit voltage side of the voltage control range (i.e., the control lower limit voltage Vrange_min) (when the judgment at S10653 is NO), the operation plan creation unit management circuit 346 proceeds to S10693 in Figure 41B.

[0499] In S10693, the operation plan creation unit management circuit 346 determines whether Vp_max and Vp_min based on the actual measurement values ​​detected in S109251 and S109252 deviate from the upper limit voltage side of the voltage control range (control upper limit voltage Vrange_max). If the determination in S10693 is NO, both Vp_max and Vp_min are within the voltage control range (Vrange_max to Vrange_min). Therefore, the operation plan creation unit management circuit 346 determines that correction of the voltage command value is not necessary and terminates the process of reviewing the voltage command value for the distribution system storage battery 8 (S10925: FIG. 40B ).

[0500] On the other hand, if the determination in S10693 is YES, the operation plan creation unit management circuit 346 checks in S10694 whether the power flow in the DC distribution system 21 is in-flow. If the power flow is in-flow (if the determination in S10694 is YES), the operation plan creation unit management circuit 346 selects in S10695 the AC / DC converter 6 that is located most upstream in the power flow current from among all the converters (the AC / DC converter 6 and the power converters 9a to 9n).

[0501] After completing S10695, the operation plan creation unit management circuit 346 sets the voltage command value of the converter (AC / DC converter 6) selected in S10695 in accordance with the control upper limit voltage Vrange_max in S10696. For example, using the same constant η as in S10676 in Fig. 41A, the voltage command value is set to "Vrange_max - η".

[0502] After completing S10696, the operation plan creation unit management circuit 346 selects the converter (power converter 9a) immediately downstream of the AC / DC converter 6 in S10697, and calculates the voltage drop (ΔVdiff) based on the measured grid tie point voltage result in S109255. Specifically, if the grid tie point voltage of the currently selected kth converter is Vp(k) and the grid tie point voltage of the (k-1)th converter selected immediately before (i.e., immediately upstream) is Vp(k-1), then Vdiff can be calculated as Vp(k) - Vp(k-1) based on the measured grid tie point voltage.

[0503] When the operation plan creation unit management circuit 346 completes S109225, in S10699, similar to S10679, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., one step upstream).

[0504] Then, in S10700, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10699 is less than the lower limit voltage (control lower limit voltage) Vrange_min of the voltage control range. If the voltage command value is less than the control lower limit voltage (YES determination in S10770), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control lower limit voltage Vrange_min in S10701. Note that the processes of S107000 and S10701 can also be omitted, similar to S10680 and S10681.

[0505] When the determination in S10700 is NO, or after the completion of S10701, the operation plan creation unit management circuit 346 checks in S10702 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed. If the correction is completed (when the determination in S10702 is YES), the process of reviewing the voltage command value 2 of the distribution system storage battery 8 (S10925: FIG. 40B) is terminated.

[0506] On the other hand, if the determination in S10702 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately downstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10703, and returns the process to S109255. As a result, the processes of S109255 to S10702 are executed for the newly selected converter. The processes of S109255 to S10702 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a YES determination is made in S10702.

[0507] Returning to S10694, if the power flow is reverse (NO in S10694), the operation plan creation unit management circuit 346 selects the DC / DC converter (power converter 9n) located most upstream of the power flow current in S10715. In S10716, the operation plan creation unit management circuit 346 sets the voltage command value of the converter selected in S10715 in accordance with the upper limit voltage of the voltage control range (control upper limit voltage Vrange_max). For example, using the same constant ζ as in S10656 in FIG. 41A, the voltage command value is set to "Vrange_max - ζ".

[0508] After completing S10716, the operation plan creation unit management circuit 346 selects the converter (here, power converter 9m) immediately upstream of the terminal converter (power converter 9n) in S10717. Furthermore, the operation plan creation unit management circuit 346 calculates a voltage drop (ΔVdiff) based on the measured grid tie-point voltage in S109256. Specifically, ΔVdiff can be calculated in the same manner as in S109253 of FIG. 41A.

[0509] When the operation plan creation unit management circuit 346 completes S10718, in S10719, it calculates the voltage command value (Vref(k)) of the kth converter described above as Vref(k) = Vref(k-1) + ΔVdiff using the voltage command value Vref(k-1) of the (k-1)th converter selected one step previously (i.e., the one downstream).

[0510] Then, in S10720, the operation plan creation unit management circuit 346 determines whether the voltage command value (Vref(k)) calculated in S10719 is less than the lower limit voltage (control lower limit voltage) Vrange_min of the voltage control range. If the voltage command value is less than the control lower limit voltage (YES determination in S10720), the operation plan creation unit management circuit 346 sets the voltage command value to be equal to the control lower limit voltage Vrange_min in S10721. Note that the processes of S10720 and S10721 can also be omitted.

[0511] If the determination in S10720 is NO, or after the completion of S10721, the operation plan creation unit management circuit 346 checks in S10722 whether the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is complete. If the correction is complete (if the determination in S10722 is YES), the process of reviewing the voltage command value 2 of the distribution system storage battery 8 (S10925: FIG. 40B) is terminated.

[0512] On the other hand, if the determination in S10722 is NO, the operation plan creation unit management circuit 346 selects a new converter immediately upstream of the currently selected converter (AC / DC converter 6 or power converter 9) in S10723, and returns the process to S109256. As a result, the processes of S109256 to S10722 are executed for the newly selected converter. The processes of S109256 to S10722 are repeated until the correction of the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) is completed and a determination of YES is made in S10722.

[0513] In this way, the voltage command values ​​of the converters (AC / DC converter 6 and power converters 9a to 9n) are corrected for each combination of the YES / NO judgment of S10653 in Figure 41A and the direction of the current (S10654, S10694).

[0514] As a result, in review 2 of the voltage command value of the distribution system storage battery 8 according to Figures 41A and 41B, unlike the review of the voltage command value based on the power flow current prediction results according to Figures 39A and 39B, it is possible to correct the voltage command values ​​of all converters (AC / DC converter 6 and power converters 9a to 9n) based on the actual measurement results of the power flow current.

[0515] 40B , when the control processing in FIGS. 41A and 41B is finished and review 2 of the voltage command value of the distribution system storage battery 8 in S10925 is completed, the operation plan creation unit management circuit 346 calculates the power flow current of the DC distribution system 21 in S10914 similar to that in FIG. 29B and re-executes voltage prediction 2 at each power receiving point in S1060. The control processing in S1060 is the same as that described in FIG. 38 , and therefore detailed description thereof will not be repeated.

[0516] In S10915, the operation plan creation unit management circuit 346 checks whether all of the voltages at the power receiving points predicted in S1060 are within a predetermined voltage control range.

[0517] If the determination in S10915 is NO, the process returns to S10925, and review 2 of the voltage command value for the distribution system storage battery 8 is executed again. That is, the processes of S10925, S10914, and S1060 are repeated until the determination in S10915 is YES.

[0518] When the determination result of S10915 is YES or when the determination result of S10913 is YES, the operation plan creation unit management circuit 346 ends the processing of "operation plan correction 2" in S125 (FIG. 36). Therefore, it can be understood that when the "operation plan correction 2" in S125 (FIG. 36) ends, the estimated values ​​of all interconnection point voltages (power receiving point voltages) are within the predetermined voltage control range.

[0519] Returning to FIG. 36 , when the process of “Creating an operation plan 2” in S120 or the process of “Modifying an operation plan 2” in S125 is completed, the CEMS 3 (operation plan creation unit management circuit 346) notifies the transmission data generation circuit 35 and the communication circuit 31 in S110 to notify the AC / DC converter 6 and the power converters 9 a to 9 n of the operation plan including the voltage command value (Vref).

[0520] When the transmission of the operation plan in S110 is completed, the CEMS 3 (operation plan creation unit management circuit 346) determines in S111 whether to terminate the operation of the CEMS 3. If the determination in S111 is YES, the operation of the CEMS 3 is stopped, whereas if the determination in S111 is NO, the process returns to S101, and the CEMS 3 continues to execute the subsequent processes.

[0521] As described above, the power converter management device according to the second embodiment generates the voltage command value (Vref) and power command value (Pref) to be output to the AC / DC converter 6 and the power converters 9a to 9n (each converter) to manage the voltage of the DC power distribution system 21. The device estimates the interconnection point (power receiving point) voltage of each converter based on the drooping characteristics of the AC / DC converter 6 and the power converters 9a to 9n, the voltages and power command values ​​(Vref, Pref), the predicted power consumption of the consumer loads 11 and the generated power of the PV panels 12 in the consumer load groups 10a to 10n, and the estimated distribution system impedance of the DC power distribution system 21. The device then corrects the voltage command value (Vref) so that the estimated result (interconnection point voltage) falls within a predetermined voltage control range. This allows the voltage of the interconnection point (power receiving point) of the DC power distribution system 21 to which the AC / DC converter 6 and the power converters 9a to 9n are connected to be appropriately managed.

[0522] 36 and 37 described in embodiment 2, S102 and S107 in FIG. 36 correspond to an example of processing by the "measurement data collection unit," S1054 by the operation plan creation circuit 34 shown in FIG. 37 corresponds to an example of "formulation processing," S1060 (voltage prediction 2 at each power receiving point) corresponds to an example of "voltage estimation processing," and S1065 (review of distribution system battery voltage command value 1) corresponds to an example of "correction processing."

[0523] Also in the second embodiment, as in the first embodiment, when an operation plan (power command value (Pref) and voltage command value (Vref)) is created for the power converter 9 for the distribution system storage battery, the power flow current is estimated using the predicted power consumption of the consumer loads 11 in the consumer load group 10 and the predicted power generation amount of the PV panels 12, and the voltage at the interconnection point of each power converter with the DC distribution system 21 is estimated based on the estimated distribution system impedance 7 and the drooping characteristics of each power converter 9, taking into account the voltage drop in the DC distribution system 21 due to the power flow current. Then, by generating a voltage command value (Vref) with correction as necessary so that the interconnection point voltage falls within a predetermined voltage control range, the voltage at the interconnection point of each power converter 9 with the DC distribution system 21 can be stably controlled to fall within the voltage control range, and the power flow can be smoothly controlled even when load fluctuations or the like occur.

[0524] Furthermore, compared to the first embodiment, the second embodiment allows the voltage command value to be freely set within a predetermined range based on the results of the power flow current (power) prediction. As a result, the second embodiment has the advantage of being able to keep the voltage at the receiving point of each converter within a predetermined voltage control range even if a load fluctuation or a fluctuation in the amount of power generation occurs that deviates from a predetermined voltage range. This is because the first embodiment creates an operation plan based on the grid reference voltage (1500 V).

[0525] Furthermore, in the second embodiment, the voltage at the interconnection point of each converter with the DC power distribution system 21 is predicted using the prediction result of the power flow current, and a voltage command value for each converter is generated based on the prediction result, so that it is possible to generate a voltage command value that takes into account a voltage drop (or rise) in the power distribution system impedance 7. As a result, in the first embodiment, charge / discharge power that differs from the planned power command value is output from each converter due to the voltage drop (or rise) due to the power distribution system impedance 7 and the influence of the drooping characteristics of each converter. However, in the second embodiment, a voltage command value that takes into account the voltage drop (or rise) in the power distribution system impedance 7 is generated, so that it is possible to output charge / discharge power from each power converter 9 that is approximately the planned value.

[0526] Furthermore, similarly to the first embodiment, even if the interconnection point (receiving point) voltage of the DC power distribution system 21 falls outside the voltage control range due to load fluctuations or the like, the voltage command value (Vref) is controlled to be corrected based on the actual measurement results, thereby achieving the effect of appropriately managing both the interconnection point (receiving point) voltage of the DC power distribution system 21 and the power.

[0527] In the second embodiment, as in the first embodiment, an example has been described in which measurement data is collected from the AC / DC converter 6, the power converters 9a to 9n, and each consumer load group 10 at five-minute intervals, but the measurement data collection interval is not limited to this example. That is, in order to appropriately manage the interconnection point (power receiving point) voltage, the collection interval can be set to a shorter time (for example, 30 seconds or 1 minute) as long as the calculation processing of the CEMS 3 is in time.

[0528] Also in the second embodiment, similarly to the first embodiment, the DC distribution system 21 is not limited to the configuration example ( FIG. 1 ) in which it is connected to the AC distribution system 20 b via the AC / DC converter 6, and similar effects can be achieved by applying similar control even when an AC main system experiences a power outage and the DC distribution system 21 is disconnected from the AC main system using the switch 5 to form an independent system. Furthermore, similar to the first embodiment, when an independent system is formed, the DC voltage of the DC distribution system 21 can be managed by operating at least one power converter 9 other than the AC / DC converter 6 in a voltage control mode.

[0529] Furthermore, in the second embodiment, as in the first embodiment, each of the AC / DC converter 6 and the power converter 9 (each converter) can be provided with a power-voltage drooping characteristic (voltage control mode) or a voltage-power drooping characteristic (power control mode), thereby applying a virtual inertial force to the DC power distribution system 21. As a result, even when a load fluctuation or a fluctuation in the amount of power generated by an energy generating device such as a renewable energy device occurs, the converters having the drooping characteristic can operate independently and cooperatively without mutual information exchange to supply excess or shortage of power due to the fluctuation, thereby making it possible to maintain the voltage of the DC power distribution system 21 within an appropriate range.

[0530] Furthermore, by appropriately arranging distributed power sources capable of controlling output power, such as each power converter 9 controlled by a power-voltage drooping characteristic (voltage control mode: FIG. 17) or a voltage-power drooping characteristic (power control mode: FIG. 18), it becomes possible to supply excess or shortage of power to the DC power distribution system 21 when a load fluctuation or the like occurs, without concentrating it in a single distributed power source.

[0531] Embodiment 3. In the first or second embodiment, a control example was described in which, when creating an operation plan (power command value (Pref) and voltage command value (Vref)) for the AC / DC converter 6 and the power converter 9 (each converter) for the distribution system storage battery, consideration was given to ensuring that the interconnection point voltage (estimated value) of each power converter 9 with the DC distribution system 21, which is estimated based on the estimated results of the power flow current and the impedance of the DC distribution system 21 and the drooping characteristics of each power converter 9, falls within a predetermined voltage control range. More specifically, in the first embodiment, a control example was described in which a power command value (Pref) for each power converter 9 is generated so that all interconnection point voltages (estimated values) fall within the voltage control range, and in the second embodiment, a control example was described in which a voltage command value (Vref) for each converter is generated.

[0532] In embodiment 3, a control example is described in which an operation plan is created so that all interconnection point voltages (estimated values) fall within a predetermined voltage control range, involving correction of both the power command value (Pref) and the voltage command value (Vref).

[0533] The following describes embodiment 3, focusing on the operation of the parts that differ from embodiments 1 and 2 (the operation of the CEMS 3). Note that in embodiment 3, only the operation of creating (including correcting) an operation plan (power command value (Pref) and voltage command value (Vref)) of the CEMS 3 differs from embodiments 1 and 2, and therefore the operation of the CEMS 3 will be described focusing on the operation of creating an operation plan. That is, the circuit configurations of the CEMS 3, AC / DC converter 6, power converter 9 for the distribution system storage battery, and power converter 13 for consumer PV are the same as those in embodiment 1 (FIGS. 2 to 16, 47A to 49), and descriptions of matters common to embodiment 1 will not be repeated.

[0534] Hereinafter, detailed operations of the CEMS 3 as a management device for the power converter according to the third embodiment will be described with reference to FIGS. 2 to 4 and 42 to 46.

[0535] FIG. 42 is a flowchart illustrating a control process of the CEMS 3 shown in FIG. 1 as a management device for power converters according to the third embodiment.

[0536] 42, when processing starts, the operation plan creation circuit 34 in the CEMS 3 executes steps S101 to S104 similar to those in FIG. 23. As a result, similar to the first and second embodiments, when there is a request for output of measurement data from the DSO 2 (YES determination in S101), data for the most recent 30 minutes is collected in steps S102 and S103 for the AC / DC converter 6, the power converters 9a to 9n for the distribution system storage batteries, and the consumer load groups 10a to 10n, and transmitted to the DSO 2 (S103). At this time, similar to the first and second embodiments, the amount of power generated by the PV panels 12a to 12n and the amount of charge / discharge power of the distribution system storage batteries 8a to 8n are calculated, and information such as the SOC and SOH of the distribution system storage batteries 8a to 8n is also transmitted to the DSO 2. Furthermore, the collected measurement data is used to update the power generation amount prediction database 351 for the PV panels 12a to 12n and the power consumption prediction database 352 for the consumer loads 11a to 11n in the operation plan creation circuit 34.

[0537] Then, when the operation plan creation circuit 34 has received the demand plan notification from the DSO 2 (YES determination in S104), the operation plan creation circuit 34 executes creation of an operation plan according to the third embodiment in S140 (creation of operation plan 3). Note that, in the third embodiment, as in the first and second embodiments, the DSO 2 notifies the CEMS 3 of a supply and demand plan for power supplied from the main grid to the DC distribution grid 21 at 30-minute intervals for 24 hours.

[0538] FIG. 43 shows a flowchart illustrating the details of the control process of S140 (operation plan creation 3) in FIG.

[0539] As shown in Fig. 43, when the process of operation plan creation 3 (S140) is started, the CEMS 3 (operation plan creation circuit 34) executes the processes of S1051 to S1056 similar to those of Fig. 24. As a result, similar to the first and second embodiments, a demand plan is created based on the predicted amounts of power generation of the PV panels 12a to 12n and the predicted power consumption of the consumer loads 11a to 11n (S1051 to S1053), and the charge / discharge power of the distribution system storage batteries 8a to 8n is determined (S1054).

[0540] Furthermore, similarly to the first and second embodiments, the impedance of the distribution system impedances 7a to 7n is estimated (S1055), and a power flow current in the DC distribution system 21 is calculated (S1056). Specifically, the power flowing through each of the distribution system impedances 7a to 7n is calculated from the result of the estimation of the excess or shortage of power in each consumer load group 10 calculated in S1054, the charging / discharging power (Pref) from each power converter 9, and the demand power (Pref) supplied from the AC / DC converter 6, and a current value is calculated from the calculation result of the power using the impedance estimation result of the distribution system impedances 7a to 7n.

[0541] Upon completing the calculation of the power flow current in S1056, the operation plan creation circuit 34 executes the process of "each power receiving point voltage prediction 2" in S1060 to predict the voltage value of the interconnection point (power receiving point) of each power converter 9 with the DC power distribution system 21. The process of each power receiving point voltage prediction 2 in S1060 is the same as that described in the second embodiment ( FIG. 38 ), and therefore detailed description thereof will not be repeated.

[0542] When the operation plan creation unit management circuit 346 completes S1060 (each receiving point voltage prediction 2), it checks, using S1058 similar to that in Figure 24, whether all receiving point voltages predicted in S1060 are within the same voltage control range as in embodiments 1 and 2 (the range of Vrange_max to Vrange_min in Figure 19).

[0543] If the judgment in S1058 is NO, that is, if even one estimated value of the interconnection point voltage (receiving point voltage) of each converter (AC / DC converter 6 and power converter 9) with the DC distribution system 21 is outside the above-mentioned voltage control range, the operation plan creation unit management circuit 346 proceeds to processing in S1067 and reviews the voltage and power command values ​​of the distribution system storage battery 8.

[0544] FIG. 44 shows a flowchart illustrating detailed control processing of review 1 of the voltage and power command values ​​of the distribution system storage battery 8 in S1067 (FIG. 43).

[0545] 44, when S1067 is started, the operation plan creation unit management circuit 346 reviews the voltage command value of the distribution system storage battery in S1065 similar to that in Fig. 37. Note that the processing content of S1065 is similar to that in the flowcharts of Figs. 39A and 39B described in the second embodiment, and therefore detailed description thereof will not be repeated.

[0546] When S1065 (review of the voltage command value of the power distribution system storage battery 8) is completed, the operation plan creation unit management circuit 346 executes each power receiving point voltage prediction 2 in S1060. The processing content of S1060 is the same as that of the flowchart in Fig. 38 described in the second embodiment, and therefore detailed description thereof will not be repeated.

[0547] When S1060 (each receiving point voltage prediction 2) is completed, the operation plan creation unit management circuit 346 checks whether all receiving point voltages are within the voltage control range in S1058. In S1058, it is checked whether all receiving point voltages predicted in S1...

Claims

1. A power converter management device that manages one or more power converters having drooping characteristics that are installed in a DC system and exchange DC power with the DC system, comprising: a measurement result collection unit that collects voltage measurement results at the interconnection point with the DC system managed by each of the power converters, and measurement results of the output current or output power of each of the power converters; a command value generation unit that generates command values ​​for each of the power converters, including one or more of a voltage command value, a power command value, and a current command value; and a command value output unit that outputs the command values ​​generated by the command value generation unit to the one or more power converters, wherein the command value generation unit estimates the interconnection point voltage between each of the power converters and the DC system based on the generated command value, and if the estimated interconnection point voltage deviates from a predetermined voltage range, performs control to correct the generated command value.

2. The power converter management device according to claim 1, wherein each of the power converters is controlled to operate in one of a voltage control mode having a first drooping characteristic that defines a voltage change in response to a power change, and a power control mode having a second drooping characteristic that defines a power change in response to a voltage change, in accordance with an instruction from the power converter management device; wherein in the voltage control mode, each of the power converters operates to control the output voltage to the DC grid in accordance with a voltage target value obtained by correcting the voltage command value from the power converter management device by a difference between the output power of the power converter and the power command value from the power converter management device, in accordance with the first drooping characteristic; and wherein in the power control mode, each of the power converters operates to control the output power or output current to the DC grid in accordance with a power target value or current target value obtained by correcting the power command value or the current command value from the power converter management device by a difference between the interconnection point voltage of the power converter and the voltage command value from the power converter management device, in accordance with the second drooping characteristic.

3. The power converter management device according to claim 2, wherein the one or more power converters include a power converter having a power conversion function between AC power and DC power for interconnecting the DC system to an AC system, and the interconnecting power converter is operated in the voltage control mode and operates to control the output voltage to the DC system according to a voltage target value obtained by correcting the voltage command value from the power converter management device by a difference between the output power of the power converter and the power command value from the power converter management device, according to the first drooping characteristic.

4. The power converter management device according to claim 3, wherein the interconnecting power converter is controlled to be disconnected from the DC system when a power outage occurs in the AC system.

5. The power converter management device according to any one of claims 1 to 4, wherein the command value generation unit includes: a power generation prediction unit that predicts the power generated at each time of an energy generation device included in consumer equipment connected to the DC system based on weather forecast information; and a power consumption prediction unit that predicts the load power consumption at each time of a consumer load included in the consumer equipment, and the command value generation unit generates the power command value or the current command value for each of the power converters based on a power surplus or shortage predicted using the prediction results of the power generation prediction unit and the power consumption prediction unit.

6. A power converter management device as described in claim 5, wherein the one or more power converters include a power converter connected to a storage battery arranged as a distributed power source and configured to transfer charging / discharging power of the storage battery to the DC system, and the command value generation unit generates the power command value for the power converter connected to the storage battery using the prediction result of the power surplus / deficit and information indicating the charge state of the storage battery.

7. The power converter management device according to claim 5 or 6, wherein the one or more power converters include a power converter arranged for each consumer group constituted by one or more consumer facilities, the power generation prediction unit predicts a total value of power generation by the energy creation devices in each consumer group, the power consumption prediction unit predicts a total value of load power consumption of the consumer loads in each consumer group, and the command value generation unit generates the power command value or the current command value for the power converter arranged for each consumer group based on a power surplus or shortage predicted using the prediction results of the total value for each consumer group by the power generation prediction unit and the power consumption prediction unit.

8. The power converter management device according to claim 6 or 7, further comprising a drooping characteristic generation unit that generates a drooping characteristic of each of the power converters, wherein the drooping characteristic generation unit generates the drooping characteristic using at least one of the converter capacity of each of the power converters, the predicted power generation amount by the power generation amount prediction unit, the load power consumption by the power consumption prediction unit, and information indicating the amount of charged power of the storage battery connected to the DC grid via the power converter.

9. The power converter management device according to any one of claims 5 to 8, wherein the command value generation unit further includes: a power flow current estimation unit that predicts a power flow current in the DC system based on the power generation power prediction result by the power generation amount prediction unit, the load power consumption by the power consumption prediction unit, and the power command value or the current command value of each of the power converters generated by the command value generation unit; and a system voltage estimation unit that estimates a voltage at the interconnection point of each of the power converters using the power flow current prediction result by the power flow current estimation unit.

10. The power converter management device according to claim 9, wherein the command value generation unit further includes a grid impedance estimation unit that estimates a grid impedance value between a connection point of each of the power converters with the DC grid, the grid impedance estimation unit being configured to estimate the grid impedance value based on measurement results of the output power of each of the power converters and the voltage of the grid connection point based on data collected by the measurement result collection unit, actual measurement results of the generated power of the energy creation equipment notified from the consumer facility, and actual measurement results of the load power consumption of the consumer load, and the grid voltage estimation unit is configured to estimate the voltage of the grid connection point of each of the power converters based on the voltage drop caused by the power flow current predicted by the power flow current estimation unit and the grid impedance value estimated by the grid impedance estimation unit.

11. A power converter management device according to claim 9 or 10, wherein the command value generation unit generates the voltage command value using the voltage estimation result of the interconnection point estimated by the system voltage estimation unit when generating the command value.

12. The power converter management device according to any one of claims 9 to 11, wherein the command value generation unit is configured to execute: a formulation process for formulating the command value based on the collected measurement results; a voltage estimation process for estimating the voltage at the interconnection point of each of the power converters when each of the power converters operates in accordance with the formulated command value; and a correction process for correcting the command value if the voltage at the interconnection point estimated by the voltage estimation process deviates from the predetermined voltage range; and when generating the command value, the command value generation unit executes the voltage estimation process by estimating, by the grid voltage estimation unit, the voltage at the interconnection point when each of the power converters operates in accordance with the command value; and when the voltage at the interconnection point estimated by the grid voltage estimation unit does not fall within the predetermined voltage range, the command value generation unit executes the correction process to correct the command value.

13. A power converter management device according to claim 12, wherein the command value generation unit corrects the command value by executing the correction process so as to revise the power command value or the current command value when the voltage estimate value at the interconnection point by the system voltage estimation unit does not fall within the predetermined voltage range.

14. The power converter management device according to claim 12, wherein the command value generation unit corrects the command value by executing the correction process so as to revise the voltage command value when the voltage estimate value at the interconnection point by the system voltage estimation unit does not fall within the predetermined voltage range.

15. A power converter management device as described in claim 12, wherein, when the voltage estimate value at the interconnection point by the system voltage estimation unit is not within the predetermined voltage range, the command value generation unit corrects the command value by executing the correction process so as to review both the voltage command value and the power command value or the current command value.

16. A power converter management device according to any one of claims 1 to 15, wherein the command value generation unit further includes a grid voltage monitoring unit that monitors the measured value of the voltage at the interconnection point of each of the power converters based on the data collected by the measurement result collection unit, and the command value generation unit recreates the command value when the grid voltage monitoring unit detects that the measured voltage value at the interconnection point of at least any of the one or more power converters has deviated from the predetermined voltage range.

17. The power converter management device according to claim 16, wherein, when the grid voltage monitoring unit detects that the voltage measurement value has deviated from the predetermined voltage range, the command value generation unit corrects the command value using at least the measurement results of the output power of each of the power converters and the voltage at the interconnection point based on data collected by the measurement result collection unit, and information on the current command value and drooping characteristic of each of the power converters.

18. A power converter management device according to claim 17, wherein the command value generation unit regenerates the voltage command value for at least each of the power converters when the system voltage monitoring unit detects that the voltage measurement value has deviated from the predetermined voltage range.

19. A power converter management device according to claim 17, wherein the command value generation unit regenerates the power command value or the current command value for at least each of the power converters when the system voltage monitoring unit detects that the voltage measurement value has deviated from the predetermined voltage range.

20. A power converter management device according to any one of claims 1 to 5, wherein the one or more power converters include a power converter connected to a storage battery arranged as a distributed power source and configured to exchange charging / discharging power of the storage battery with the DC grid, and when the amount of charging power of each storage battery estimated based on data collected by the measurement result collection unit falls outside a predetermined range, the power converter management device recreates the command value of the power converter connected to the storage battery so as to correct at least the power command value or the current command value.

21. A power converter management device according to any one of claims 1 to 8, wherein the command value generation unit is configured to execute: a formulation process for formulating the command value based on the collected measurement results; a voltage estimation process for estimating the voltage at the interconnection point of each of the power converters when each of the power converters operates in accordance with the formulated command value; and a correction process for correcting the command value when the voltage at the interconnection point estimated by the voltage estimation process deviates from the predetermined voltage range.

22. A DC power system comprising: at least one power converter having droop characteristics arranged in a DC power system; and a power converter management device according to any one of claims 1 to 21 for managing the one or more power converters.