Distributed power-supply management apparatus and power distribution system

Abstract

Provided is a distributed power-supply management apparatus (31) for managing one or more distributed power supplies. Each of the one or more distributed power supplies is connected to a power grid and operates as a voltage source. The relationship between the frequency and power of each of the one or more distributed power supplies has a droop characteristic, and is adjusted such that a command value for frequency (Fref) and a command value for power (Pref) correspond to each other. The distributed power-supply management apparatus (31) is provided with: an AC-frequency collecting unit (313) that collects information on the AC frequency of the power grid, and on the basis of the collected AC-frequency information, determines a representative value (Fmeasure) for the AC frequency; and a frequency command-value generating unit (315) that on the basis of the representative value for the AC frequency, generates respective frequency command values (Fref) for the one or more distributed power supplies.

Description

Distributed Power Management Equipment and Power Distribution Systems

[0001] The present disclosure relates to a distributed power source management device and a power distribution system, and more particularly to a method for generating control command values ​​to be given to one or more distributed power sources having drooping characteristics when connecting the distributed power sources to an AC power distribution system, such as when implementing virtual synchronous generator control. In this disclosure, the multiple distributed power sources include energy creation devices (hereinafter also referred to as "energy creation devices") that use renewable energy such as solar cells, and / or energy storage devices (hereinafter also referred to as "energy storage devices") such as fuel cells and storage batteries.

[0002] In recent years, in order to reduce the environmental burden, the introduction of power generation systems that use natural energy such as solar cells, which do not emit carbon dioxide, has been accelerating. Also, in order to respond to the power shortages that have occurred since the Great East Japan Earthquake, efforts are being made to commercialize systems equipped with storage batteries, systems that use electric vehicles as storage batteries, and systems that combine solar cells and storage batteries. All of these systems use static inverters.

[0003] On the other hand, as the amount of electricity generated by renewable energy increases, the cost of generating electricity, including management costs, of thermal power plants, which serve as balancing capacity, is expected to increase in the future. Synchronous generators used in thermal power plants, etc., have the potential to suppress fluctuations in system frequency (known as inertia force or synchronizing force). Therefore, if the number of synchronous generators decreases due to the closure of thermal power plants, it will become more difficult to ensure system stability.

[0004] To solve the above problems, various companies are developing virtual synchronous generator control technology that gives static inverters the functionality of a synchronous generator.

[0005] For example, Japanese Patent Laid-Open Publication No. 2019-176584 (Patent Document 1) discloses a method for setting control parameters of a distributed power source (more specifically, a static inverter) that implements virtual synchronous generator control technology. Specifically, this document describes a static inverter that connects a distributed power source to a power grid based on either a required inertia value requested by a grid operator or a virtual inertia value calculated based on the specifications and operating state of the distributed power source.

[0006] More specifically, the total virtual inertia value Jopt, which is the sum of the virtual inertias of the individual static inverters, is set as follows: First, the grid interconnection control device receives a virtual inertia value Jreq requested by the grid operator for the distributed power source. Next, the grid interconnection control device sets an upper limit value Jmax,i of the virtual inertia for each static inverter and a lower limit Dmin,i of the virtual damping constant when operating at the virtual inertia upper limit value Jmax,i, based on the operating state of the renewable energy system and specification data of the renewable energy system. Then, the grid interconnection control device determines whether the total value ΣJmax,i of the upper limits Jmax,i is smaller than the requested virtual inertia value Jreq. If the total value ΣJmax,i of Jmax,i is smaller than the requested virtual inertia value Jreq, the grid interconnection control device sets a total virtual inertia value Jopt suitable for the renewable energy system to Jopt = ΣJmax,i. On the other hand, when the total value ΣJmax,i of Jmax,i is larger than the required virtual inertia value Jreq, the grid interconnection control device is configured to set Jopt = Jreq. Furthermore, Patent Document 1 describes that a total virtual damping constant value Doptimal (i.e., an optimal value) suitable for a renewable energy system can also be set in a similar manner.

[0007] JP 2019-176584 A

[0008] In the case of Patent Document 1, the control parameters (i.e., the total virtual inertia value and the total virtual damping constant value) for virtual synchronous generator control of a static inverter equipped with a virtual synchronous generator control function are calculated and set by the above-mentioned method. According to this method, the inertial force of the system intended by the system manager is guaranteed, but the following problems arise when load fluctuations occur or when the amount of power generation changes.

[0009] That is, when a load fluctuation or a change in power generation occurs, each distributed power source shares the excess or shortage of power according to its respective virtual synchronous generator characteristics (i.e., drooping characteristics). More specifically, each distributed power source (more specifically, a static inverter) operates in a manner simulating a synchronous generator based on drooping characteristics such as virtual synchronous generator control, thereby supplying the excess or shortage of power caused by the load fluctuation or the change in power generation. In this case, each distributed power source determines the frequency of the grid AC voltage it outputs based on the difference between the power command value from a host EMS (Energy Management System) and the power it outputs. Meanwhile, the frequency of the grid AC voltage is managed by a large-capacity synchronous generator connected to the utility grid. In other words, the large-capacity synchronous generator dominates the frequency of the grid AC voltage. Even if a distributed power source implementing virtual synchronous generator control installed in a power distribution system supplies excess or shortage of power according to the drooping characteristics, it has almost no effect on the frequency of the grid AC voltage. Furthermore, the frequency of the AC grid voltage that can be covered by a distributed power source implementing virtual synchronous generator control is determined by the drooping characteristics and the power command value from the host EMS. Generally, the frequency of a utility grid varies by approximately ±0.2 Hz from the rated frequency. Meanwhile, a distributed power supply implementing virtual synchronous generator control (i.e., a distributed power supply with drooping characteristics that operates as a voltage source) limits the upper and lower frequency limits of the AC grid voltage that it can cover in order to operate stably, and the frequency range that the utility grid can cover is wider than this frequency range. Therefore, if the frequency of the AC grid voltage deviates from the frequency range that a distributed power supply implementing virtual synchronous generator control can cover, the distributed power supply implementing virtual synchronous generator control will stop operating, which is a problem.

[0010] The present disclosure has been made to solve the above-mentioned problems and relates to a distributed power management device (i.e., a higher-level EMS). The purpose of the present disclosure is to generate a control command value by the distributed power management device so that, in a power system where multiple static inverters implementing a virtual synchronous generator control method are installed, even if the frequency of the AC system voltage changes due to fluctuations or sudden changes in load consumption or fluctuations or sudden changes in power generated by energy-generating devices such as renewable energy, the static inverters having virtual synchronous generator characteristics (more generally, drooping characteristics) do not deviate from a frequency range that can be managed by the drooping characteristics, and the static inverters can continue operating without stopping.

[0011] According to one aspect of the present disclosure, there is provided a distributed power management device that manages one or more distributed power sources. Each of the one or more distributed power sources is connected to a power grid and operates as a voltage source. The relationship between the frequency and power of each of the one or more distributed power sources has a drooping characteristic, and the frequency command value and the power command value are adjusted so that they correspond to each other. The distributed power management device includes an AC frequency collection unit that collects information about AC frequencies of the power grid and determines a representative value of the AC frequency based on the collected AC frequency information, and a frequency command value generation unit that generates a frequency command value for each of the one or more distributed power sources based on the representative value of the AC frequency.

[0012] According to another aspect of the present disclosure, there is provided a distributed power management device that manages one or more distributed power sources. Each of the one or more distributed power sources is connected to a power grid and operates as a voltage source. The relationship between the frequency and power of each of the one or more distributed power sources has a drooping characteristic, and the frequency command value and the power command value are adjusted so that they correspond to each other. The distributed power management device includes an AC frequency collection unit that collects information about AC frequencies of the power grid and determines a representative value of the AC frequency based on the collected AC frequency information, and a power command value correction unit that corrects the power command value of each of the one or more distributed power sources based on the representative value of the AC frequency.

[0013] According to the present disclosure, a frequency command value or power command value to be given to each distributed power source is determined based on the actual measured AC frequency of the power grid. As a result, even if the frequency of the AC grid voltage changes due to fluctuations or sudden changes in the power generated by energy-creating devices such as renewable energy sources supplied to the grid due to fluctuations or sudden changes in the power consumption of the load or sudden changes in solar radiation, the frequency range managed by the static inverter that implements virtual generator control characteristics (more generally, drooping characteristics) and the like will not deviate, and the distributed power source can continue to operate without being shut down.

[0014] 1 is a block diagram showing the configuration of a power distribution system including a distributed power management device according to a first embodiment and a plurality of distributed power sources controlled by the device; FIG. 1 is a block diagram showing the configuration of the CEMS shown in FIG. 1; FIG. 2 is a block diagram showing the configuration of an operation plan creation circuit in the CEMS shown in FIG. 2; FIG. 3 is a block diagram showing the configuration of an AC frequency collection circuit in the CEMS shown in FIG. 1; FIG. 5 is a block diagram explaining the configuration of a first control circuit for controlling the first DC / DC conversion circuit of the power conversion device for a storage battery shown in FIG. 5; FIG. 6 is a block diagram explaining the configuration of a second control circuit for controlling the first DC / AC conversion circuit of the power conversion device for a storage battery shown in FIG. 5; FIG. 7 is a block diagram explaining the configuration of an AC frequency detection circuit shown in FIG. 7; FIG. 8 is a block diagram explaining the configuration of an inverter current control circuit shown in FIG. 7; FIG. 9 is a block diagram explaining the configuration of an inverter voltage control circuit shown in FIG. 7; FIG. 10 is a block diagram explaining the configuration of a virtual synchronous generator control circuit shown in FIG. 11; FIG. 12 is a block diagram explaining the configuration of a governor control circuit shown in FIG. 13; FIG. 14 is a block diagram explaining the configuration of a mass system calculation circuit shown in FIG. 14; 21 is a diagram showing an example of drooping characteristics of virtual synchronous generator control shown in the first embodiment. FIG. 22 is a diagram showing an example of the results of actually measuring the frequency of a distribution system voltage at a cycle of one second for 25 hours. FIG. 23 is a diagram showing an example of drooping characteristics of a power conversion device for a storage battery in the distribution system of the first embodiment. FIG. 24 is a diagram for explaining a method of creating a frequency command value in the distributed power management device of the first embodiment. FIG. 25 is a diagram showing a frequency command value when a drooping characteristic of a comparative example is used. FIG. 26 is a diagram showing a frequency command value when the drooping characteristic of the first embodiment is used. FIG. 27 is a sequence diagram during normal operation of the distributed power management system centered on the CEMS shown in FIG. 1. A flowchart showing control processing of the CEMS shown in FIG. 1. A flowchart showing detailed operations of the operation plan creation processing in step S105 of the flowchart shown in FIG. 21. A flowchart showing a procedure for generating a frequency command value. FIG. 28 is a diagram showing an example of drooping characteristics of a power conversion device for a storage battery in the distributed power management system of the first embodiment.23. FIG. 35 is a flowchart showing a procedure for generating a frequency command value in step S10574 of FIG. 23. FIG. 35 is a diagram for explaining a procedure for correcting a frequency command value. FIG. 35 is a flowchart showing a procedure for determining whether or not an operation plan needs to be corrected. FIG. 35 is a flowchart showing a procedure for correcting an operation plan. FIG. 35 is a flowchart mainly showing the operation of a second control circuit. FIG. 35 is a flowchart showing a control procedure for a first DC / AC conversion circuit. FIG. 35 is a block configuration diagram of a CEMS in embodiment 2. FIG. 35 is a diagram for explaining a method for generating a power command value in the CEMS of embodiment 2 (before correction of the power command value). FIG. 35 is a diagram for explaining a method for generating a power command value in the CEMS of embodiment 2 (after correction of the power command value). FIG. 35 is a diagram showing a frequency range of an inverter when a drooping characteristic of a comparative example is used. FIG. 35 is a diagram showing a power command value and a frequency of an inverter when the drooping characteristic of embodiment 2 is used. FIG. 35 is a flowchart showing detailed operations of the operation plan creation process in step S105 of FIG. 21 in embodiment 2. FIG. 35 is a flowchart showing a procedure for generating a power command value. FIG. 35 is a diagram showing an example of drooping characteristic of a power conversion device for a battery in the distributed power management system of embodiment 2. 1 is a flowchart showing a procedure for correcting an operation plan in a distributed power management device of embodiment 2. FIG. 2 is a diagram showing an example of a linear drooping characteristic when a power conversion device for a storage battery performs charging and discharging. FIG. 3 is a diagram showing an example of a linear drooping characteristic with a dead band when a power conversion device for a storage battery performs charging and discharging. FIG. 4 is a diagram showing an example of a curved drooping characteristic when a power conversion device for a storage battery performs charging and discharging. FIG. 5 is a diagram showing an example of a linear drooping characteristic with a dead band when a power conversion device for a storage battery only performs discharging. FIG. 6 is a diagram showing an example of a curved drooping characteristic with a dead band when a power conversion device for a storage battery only performs charging. FIG. 7 is a diagram showing an example of a curved drooping characteristic with a dead band when a power conversion device for a storage battery only performs charging.12 is a diagram showing an example of a linear drooping characteristic when the power conversion device for a storage battery only performs charging. FIG. 13 is a diagram showing an example of a linear drooping characteristic with a dead zone when the power conversion device for a storage battery only performs discharging. FIG. 14 is a diagram showing an example of a linear drooping characteristic with a dead zone when the power conversion device for a storage battery only performs charging. FIG. 15 is a diagram showing a schematic representation of a governor function. FIG. 16 is a block configuration diagram shown for calculating the transfer function F(s) of the virtual synchronous generator control circuit 4093 shown in FIG. 11.

[0015] Each embodiment will be described in detail below with reference to the drawings. In the following, the same or corresponding parts in the drawings will be given the same reference characters, and their description will not be repeated in principle.

[0016] Embodiment 1. [Configuration example of a distributed power management device and a power distribution system] Fig. 1 is a block diagram showing the configuration of a distributed power management device according to embodiment 1 and a power distribution system including a plurality of distributed power sources controlled by the distributed power management device. Note that in embodiment 1, a three-phase system will be described as an example of the power distribution system, but it goes without saying that the distributed power management device of embodiment 1 may also be applied to a single-phase system.

[0017] 1 , the power distribution system 1 includes a substation 20, a main distribution line 24m drawn from the substation 20, branch distribution lines 24a to 24d branching from the main distribution line 24m, and a plurality of automatic voltage regulators 23 arranged in series with the main distribution line 24m. In the first embodiment, an SVR (Step Voltage Regulator) is used as the automatic voltage regulator 23. Hereinafter, the automatic voltage regulator 23 will also be referred to as an SVR 23. Furthermore, the main distribution line 24m and the branch distribution lines 24a to 24d will be collectively referred to as a distribution line 24. 1 , power distribution line 24 is connected to consumers such as building 102, apartment building 103, town A 100a, town B 100b, town C 100c, town D 100d, and factory 101, mega solar power conversion device 27, storage battery power conversion devices 41a, 41b, and 41c, and synchronous generators 30a and 30b. Mega solar power conversion device 27 is connected to mega solar 26, and storage batteries 40a, 40b, and 40c are connected to storage battery power conversion devices 41a, 41b, and 41c, respectively.

[0018] Furthermore, the power distribution system 1 includes a plurality of voltmeters 22 (22a to 22x) connected to the main distribution line 24m, a power distribution automation system 21, and a community energy management system (CEMS) 31. Hereinafter, the power distribution automation system 21 will also be referred to as a DSO (Distribution System Operator) 21. The CEMS 31 corresponds to the distributed power source management device in this disclosure. The CEMS 31, together with the DSO 21, the battery power conversion device 41, the voltmeter 22, and the like, will be referred to as a distributed power source management system.

[0019] In this embodiment, each voltmeter 22 calculates the effective voltage value and frequency of the AC system voltage based on the measured voltage information of the distribution line 24 of the power distribution system 1. Each voltmeter 22 notifies the DSO 21 and the CEMS 31 of the calculated effective voltage value and frequency at predetermined intervals (for example, every one minute).

[0020] In this embodiment, each SVR 23 periodically notifies the distribution automation system (DSO) 21 of tap position information, primary voltage information, and secondary voltage information. Furthermore, when a tap is changed, the SVR 23 irregularly notifies the distribution automation system (DSO) 21 of the tap position information, primary voltage information, and secondary voltage information.

[0021] The CEMS 31 collects various measurement result information, such as power consumption, from smart meters (not shown) installed in each consumer (i.e., town A 100a, town B 100b, town C 100c, town D 100d, building 102, condominium 103, factory 101) at predetermined intervals (e.g., one-minute intervals). Furthermore, the CEMS 31 collects various measurement result information, such as power generation power of each energy generation device, from the mega solar power conversion device 27, synchronous generators 30a and 30b, and storage battery power conversion devices 41a, 41b, and 41c at predetermined intervals (e.g., one-minute intervals). At this time, the CEMS 31 notifies the DSO 21 of the collected data upon request from the DSO 21. In the first embodiment, the communication period between the CEMS 31 and the DSO 21 is 30 minutes.

[0022] In the above, the communication cycle between the DSO 21 and the CEMS 31 is set to 30 minutes, but it is not limited to this and may be, for example, a 15-minute cycle or a 1-hour cycle. Furthermore, it is also not limited to one minute for the communication cycle between the CEMS 31 and each voltmeter 22 and the battery power converter 41, and it may be, for example, a 1-second cycle, a 10-second cycle, a 30-second cycle, a 2-minute cycle, or the like.

[0023] Fig. 2 is a block diagram of the CEMS 31 shown in Fig. 1. Referring to Fig. 2, the CEMS 31 includes a communication circuit 311, a memory circuit 312, an AC frequency collection circuit 313, an operation plan creation circuit 314, a frequency command value generation circuit 315, a distributed power source drooping characteristic management circuit 316, a transmission data generation circuit 317, and a CEMS internal control circuit 318.

[0024] The communication circuit 311 communicates via communication line 25 with the DSO 21, each voltmeter 22, each SVR 23, each consumer (i.e., Town A 100a, Town B 100b, Town C 100c, Town D 100d, Building 102, Apartment 103, Town 100, and Factory 101), mega solar power conversion device 27, synchronous generators 30a, 30b, and storage battery power conversion devices 41a, 41b, 41c.

[0025] The memory circuitry 312 stores various information obtained via the communication circuitry 311, such as measurement results and status information for each distributed power source.

[0026] The AC frequency collection circuit 313 generates a representative value (Fmeasure) of the frequency of the measured AC system voltage based on the measurement results of the frequency of the AC system voltage received from the voltmeter 22, the measurement results of the frequency of the AC system voltage received from the storage battery power conversion devices 41a, 41b, and 41c, and the measurement results of the frequency of the AC system voltage received from the mega solar power conversion device 27. In the first embodiment, the AC frequency collection circuit 313 calculates and outputs an average value as a representative value from the frequencies at each point of the AC system voltage measured by the voltmeters 22a to 22x. This averages out the measurement errors of each voltmeter 22.

[0027] Note that the method for generating the representative value of frequency in the AC frequency collection circuit 313 is not limited to the above. For example, it goes without saying that the output of one voltmeter 22 may be used as the representative value, or the representative value may be determined using the frequency measurement results of the AC system voltage measured by the battery power conversion device 41 or another distributed power source. If the distribution system 1 is an independent system, the representative value of AC frequency may be a calculated value of AC frequency collected from the distributed power source with the largest power capacity among multiple distributed power sources, or from the distributed power source corresponding to the largest power command value among the power command values ​​generated by the battery operation plan generation circuit 3141 of the operation plan creation circuit 314 described later.

[0028] The operation plan creation circuit 314 creates operation plans for the storage battery power conversion devices 41a, 41b, and 41c based on control commands from the DSO 21. In the first embodiment, the operation plan creation circuit 314 generates operation plans for 24 hours at 30-minute intervals. Furthermore, the operation plan creation circuit 314 determines whether or not the operation plan needs to be modified based on information such as measurement results and SOC (State Of Charge) of the storage battery power conversion devices 41a, 41b, and 41c collected every minute. If the operation plan creation circuit 314 determines that the operation plan needs to be modified, it modifies the operation plan for the period until the next control command is notified from the DSO 21.

[0029] The frequency command value generating circuit 315 generates a frequency command value (Fref) based on a representative value (Fmeasure) of the measurement result of the frequency of the AC system voltage output from the AC frequency collecting circuit 313 .

[0030] The distributed power supply drooping characteristic management circuit 316 stores and manages the drooping characteristics of the battery power conversion devices 41a, 41b, and 41c. In the first embodiment, the distributed power supply drooping characteristic management circuit 316 stores and manages virtual synchronous generator control parameters (i.e., a speed adjustment ratio: Kgd, a governor time constant: Tg, an inertia constant: M, and a damping coefficient: Dg) described below. It goes without saying that the distributed power supply drooping characteristic management circuit 316 may manage the drooping characteristics themselves, or may be configured to manage the slope ΔP / ΔF of the drooping characteristics. Furthermore, the drooping characteristics of the distributed power supplies are not limited to virtual synchronous generator control, and any drooping characteristics having a P (power)-F (frequency) characteristic may be used. It goes without saying that the distributed power supply drooping characteristic management circuit 316 may be configured to acquire and manage the control parameters (i.e., the drooping characteristics) from the virtual synchronous generator control circuit 4093 of the battery power conversion device 41.

[0031] The transmission data generation circuit 317 stores the operation plan output from the operation plan creation circuit 314 and the frequency command value (Fref) output from the frequency command value generation circuit 315. Then, the transmission data generation circuit 317 outputs the stored data to the communication circuit 311 based on a transmission command from the CEMS control circuit 318. The communication circuit 311 transmits the data output from the communication data generation circuit 317 in accordance with a control signal output from the CEMS control circuit 318.

[0032] The CEMS control circuit 318 controls the operation of each of the communication circuit 311, memory circuit 312, AC frequency collection circuit 313, operation plan creation circuit 314, frequency command value generation circuit 315, distributed power source drooping characteristic management circuit 316, and transmission data generation circuit 317, which are provided within the CEMS 31.

[0033] Fig. 3 is a block diagram of the operation plan creation circuit 314 in the CEMS 31 shown in Fig. 2. Referring to Fig. 3, the operation plan creation circuit 314 includes a battery operation plan generation circuit 3141, a power generation amount prediction circuit 3142, a power consumption prediction circuit 3143, a battery operation plan correction circuit 3144, a power command value storage and transmission circuit 3145, and a management circuit 3146.

[0034] The battery operation plan generation circuit 3141 generates operation plans (specifically, frequency command values ​​and power command values) for the battery power conversion devices 41 a, 41 b, 41 c every 30 minutes and for 24 hours, based on control command information notified from the DSO 21, the power generation amount prediction result of the mega solar power plant 26 predicted by the power generation amount prediction circuit 3142, and power consumption prediction information of consumers predicted by the power consumption prediction circuit 3143. Here, the control information notified from the DSO 21 is a planned value (for example, a 30-minute, 24-hour plan) of the power consumed on the load side of the substation 20 (i.e., the supply power supplied from the substation 20 to the load side).

[0035] The power generation amount prediction circuit 3142 obtains weather forecast information for 24 hours from a weather forecast server (not shown) via the communication circuit 311. The power generation amount prediction circuit 3142 predicts the power generation amount of the mega solar power plant 26 based on the obtained weather forecast information, clock information (date, time) inside the CEMS 31 (not shown), and database information (not shown) prepared for power generation amount prediction.

[0036] The power consumption prediction circuit 3143 predicts the total power consumption of each consumer based on the internal clock information (i.e., date, day of the week, and time) of the CEMS 31 (not shown) and database information prepared for power consumption prediction (not shown).

[0037] The battery operation plan correction circuit 3144 determines whether or not the operation plan needs to be revised based on the charge / discharge power amounts of the battery power conversion devices 41a, 41b, and 41c collected via the communication circuit 311 and the notified power command value information, and if it determines that the operation plan needs to be revised, generates a revised value for the operation plan.

[0038] The power command value storage and transmission circuit 3145 stores the power command values ​​of each distributed power source generated by the battery operation plan generation circuit 3141 and the battery operation plan correction circuit 3144, and outputs the power command values ​​to the frequency command value generation circuit 315 based on a control signal output from the management circuit 3146 in the operation plan creation circuit 314.

[0039] The management circuit 3146 in the operation plan creation circuit 314 manages the operations of the battery operation plan generation circuit 3141 , the power generation amount prediction circuit 3142 , the power consumption prediction circuit 3143 , the battery operation plan correction circuit 3144 , and the power command value storage and transmission circuit 3145 .

[0040] Fig. 4 is a block diagram of the AC frequency collection circuit 313 in the CEMS 31 shown in Fig. 2. Referring to Fig. 4, the AC frequency collection circuit 313 includes an averaging circuit 3131, a multiplier 3132, an adder 3133, a multiplier 3134, and a register 3135. As shown in Fig. 4, in the first embodiment, the AC frequency collection circuit 313 is configured to remove noise components from the output of the averaging circuit 3131 using a first-order IIR (Infinite Impulse Response) filter and output the output.

[0041] The averaging circuit 3131 is notified of the frequency of the AC system voltage collected by the voltmeter 22 at one-minute intervals from the control circuit 318 in the CEMS. The averaging circuit 3131 calculates the average value of the notified frequency of the AC system voltage. The multiplier 3132 multiplies the average value of the frequency output from the averaging circuit 3131 by a multiplication constant k output from the control circuit 318 in the CEMS. The adder 3133 adds the output of the multiplier 3132 and the output of the multiplier 3134, and outputs the addition result to the frequency command value generation circuit 315 and a register 3135. The register 3135 stores the addition result of the adder 3133. The multiplier 3134 multiplies the value of the register 3135 by a multiplication constant (1-k), and outputs the multiplication result to the adder 3133.

[0042] Fig. 5 is a block diagram of the battery power conversion device 41 shown in Fig. 1. Referring to Fig. 5, the battery power conversion device 41 includes a voltmeter 401, an ammeter 402, a first DC / DC conversion circuit 403, a first control circuit 404, a DC bus 405, a voltmeter 406, an ammeter 407, a first DC / AC conversion circuit 408, a second control circuit 409, a voltmeter 410, an ammeter 411, and a communication interface circuit 412.

[0043] The voltmeter 401 measures the voltage (i.e., DC voltage) output from the storage battery 40. The ammeter 402 measures the current (i.e., DC current) output from the storage battery 40. The first DC / DC conversion circuit 403 converts the first DC voltage (DC power) output from the storage battery 40 into a second DC voltage (DC power). The first control circuit 404 controls the first DC / DC conversion circuit 403 based on the measurement values ​​of the voltmeters 401 and 406 and the measurement value of the ammeter 402. The DC bus 405 supplies the second DC voltage output from the first DC / DC conversion circuit 403 to the first DC / AC conversion circuit 408.

[0044] [Correction based on Rule 91 05.11.2024] The voltmeter 406 measures the voltage of the DC bus 405. The ammeter 407 measures the DC current output from the first DC / DC conversion circuit 403. The first DC / AC conversion circuit 408 converts the DC power output from the first DC / DC conversion circuit 403 into AC power. The second control circuit 409 controls the first DC / AC conversion circuit 408 based on the measurement values ​​of the voltmeters 406 and 410 and the measurement values ​​of the ammeters 407 and 411. The voltmeter 410 measures the voltage (i.e., AC voltage) output from the first DC / AC conversion circuit 408. The ammeter 411 measures the current (i.e., AC current) output from the first DC / AC conversion circuit 408. The communication interface circuit 412 communicates between the battery power conversion device 41 and the CEMS 31.

[0045] Note that known DC / DC converter and inverter configurations can be appropriately used for the first DC / DC conversion circuit 403 and the first DC / AC conversion circuit 408. In the configuration of Fig. 5, the first DC / AC conversion circuit 408 corresponds to an embodiment of a "static inverter unit." The second control circuit 409 corresponds to an embodiment of a "static inverter control unit."

[0046] FIG. 6 is a block diagram illustrating the configuration of the first control circuit 404 that controls the first DC / DC conversion circuit 403 of the battery power conversion device 41 shown in FIG.

[0047] Referring to FIG. 6, the first control circuit 404 includes a charge control circuit 4041 , a discharge control circuit 4042 , a first switching circuit 4043 , and a third control circuit 4044 .

[0048] The charge control circuit 4041 generates a control command value for the first DC / DC conversion circuit 403 when controlling charging of the storage battery 40, based on the measurement values ​​of the voltmeters 401 and 406 and the measurement value of the ammeter 402. The discharge control circuit 4042 generates a control command value for the first DC / DC conversion circuit 403 when controlling discharging from the storage battery 40, based on the measurement values ​​of the voltmeters 401 and 406 and the measurement value of the ammeter 402.

[0049] The third control circuit 4044 outputs control parameters, control target values ​​(command values), etc. to the charge control circuit 4041 and the discharge control circuit 4042, and manages the charge amount, charge current, discharge power amount, etc. of the storage battery 40. Furthermore, the third control circuit 4044 outputs a control signal to the first switching circuit 4043.

[0050] The first switching circuit 4043 selectively outputs one of the outputs of the charge control circuit 4041 and the discharge control circuit 4042 as a control command value for the first DC / DC conversion circuit 403 in accordance with a control signal from the third control circuit 4044. When an instruction to charge the storage battery 40 is given, the first switching circuit 4043 is controlled to output the control command value generated by the charge control circuit 4041. When an instruction to discharge the storage battery 40 is given, the first switching circuit 4043 is controlled to output the control command value generated by the discharge control circuit 4042.

[0051] FIG. 7 is a block diagram illustrating the configuration of the second control circuit 409 that controls the first DC / AC conversion circuit 408 of the battery power conversion device 41 shown in FIG.

[0052] Referring to FIG. 7 , the second control circuit 409 includes an AC frequency detection circuit 4091, an effective power calculation circuit 4092, a virtual synchronous generator control circuit 4093, an inverter current control circuit 4094, an inverter voltage control circuit 4095, a second switching circuit 4096, and a fourth control circuit 4097.

[0053] The AC frequency detection circuit 4091 detects the phase and frequency from the AC voltage waveform measured by the voltmeter 410. In the first embodiment, the AC frequency detection circuit 4091 detects zero-crossing points from the AC voltage waveform and detects the frequency from the time interval between the detected zero-crossing points. It goes without saying that the method for detecting the AC voltage frequency is not limited to the method using the detection result of the zero-crossing points.

[0054] The effective power calculation circuit 4092 calculates effective power from AC voltage information and AC current information measured by the voltmeter 410 and ammeter 411. In the first embodiment, the effective power calculation circuit 4092 calculates effective power by integrating the power for one cycle of the AC voltage waveform based on the zero-crossing point detection information and AC frequency information output from the AC frequency detection circuit 4091. Note that the method for calculating effective power is not limited to the above method. For example, it goes without saying that if the AC system is three-phase AC, the effective power may be calculated using dq transformation or the like.

[0055] The virtual synchronous generator control circuit 4093 provides the first DC / AC conversion circuit 408 (i.e., the static inverter) with the inertial force, synchronizing force, and braking force of a synchronous generator based on the AC voltage frequency information and AC effective power information output from the AC frequency detection circuit 4091 and the effective power calculation circuit 4092.

[0056] Below, we briefly explain virtual synchronous generator control technology. Synchronous generators, such as those used in thermal power plants, have functions such as adjusting the power output according to frequency (i.e., governor function), maintaining angular velocity (i.e., inertia force), synchronizing with AC grid voltage (i.e., synchronizing force), regulating the main grid voltage (i.e., AVR function: Automatic Voltage Regulator), and continuing 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, it simulates three functions: a governor function, a function simulating a mass system model based on an oscillation equation (i.e., the dynamic characteristics of a rotating machine), and an AVR function.

[0057] In this first embodiment, a case will be described in particular where a governor function and a function simulating a mass system model based on an oscillation equation are implemented. Fig. 42 shows a conceptual diagram for explaining virtual synchronous generator control technology. Note that the AVR function of the synchronous generator is not implemented in this first embodiment, as it is a function that is controlled mainly based on an output voltage command or a reactive power command value notified from a higher-level system (CEMS 31 in the first embodiment). Below, the governor function and the function simulating a mass system model based on an oscillation equation will be specifically described.

[0058] First, let us explain the governor function. In a power plant, a governor controls the output of a gas or steam turbine in a thermal or nuclear power plant, or the guide vanes of a water turbine in a hydroelectric power plant, thereby controlling the generator's output power. In an AC power system, when demand exceeds supply, the frequency of the AC system voltage drops. In thermal and hydroelectric power generators that are capable of output control, the governor is given a droop characteristic, and when the frequency drops, the governor controls the power generation to increase. On the other hand, when supply exceeds demand, the frequency of the AC system voltage rises. Similarly, in this case, in thermal and hydroelectric power generators that are capable of output control, the governor is given a droop characteristic, and when the frequency rises, the governor controls the power generation to decrease.

[0059] FIG. 42 is a schematic diagram showing the governor function. As shown in FIG. 42, when the angular velocity ω of the synchronous generator increases, the valve regulating the energy inflow moves to the right, decreasing the energy supplied to the synchronous generator. On the other hand, when the angular velocity of the synchronous generator decreases, the valve regulating the energy inflow moves to the left, increasing the energy supplied to the synchronous generator. This allows the energy output from the synchronous generator to be independently controlled by the frequency of the AC system voltage at its own end (i.e., the angular velocity of the synchronous generator). Even when the above operation is performed individually by the synchronous generators, load sharing between the generators is possible because it is managed by the frequency of the AC system voltage. The Institute of Electrical Engineers of Japan (IEEE) provides a standard governor model, such as a first-order delay model.

[0060] In this first embodiment, we will explain the operation when the governor is approximated by a model configured with the above-mentioned first-order lag system. The transfer function of the governor is expressed by the following equation (1). Note that 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).

[0061]

[0062] Next, we will explain the function of simulating a mass system model based on an oscillation equation. As shown in Figure 42, a synchronous generator has a generator rotor with a unit inertia constant M. For example, if the power generated by the mega solar power plant 26 suddenly decreases due to a sudden change in solar radiation, the governor control described above cannot instantaneously cover the power shortage. The synchronous generator converts the rotational energy stored in the generator rotor into electric power and outputs it to the grid. During this process, the angular velocity of the generator rotor (i.e., the number of rotations per unit time) decreases. When the angular velocity of the generator rotor decreases, the energy supplied by the governor control increases, supporting both demand and supply. The following equation (2) shows the oscillation equation simulating the mass system model (generator rotor). In equation (2), energy P is divided by angular velocity ω and converted into torque T. In equation (2), Dg represents the damping coefficient, and M represents the inertia constant described above.

[0063]

[0064] In this first embodiment, we will explain the case where equations (1) and (2) are incorporated into the control of a static inverter (i.e., the first DC / AC conversion circuit 408) to simulate the inertial force, synchronizing force, and braking force of a synchronous generator.

[0065] 7 , inverter current control circuit 4094 generates a control command value for controlling first DC / AC conversion circuit 408 by current control, based on the outputs of voltmeter 406, ammeter 411, and AC frequency detection circuit 4091. Inverter voltage control circuit 4095 generates a control command value for controlling first DC / AC conversion circuit 408 by voltage control (i.e., a control method in which AC system voltage is output from first DC / AC conversion circuit 408), based on the outputs of voltmeter 410 and AC frequency detection circuit 4091. Second switching circuit 4096 switches between the control command value from inverter current control circuit 4094 and the control command value from inverter voltage control circuit 4095, based on the output of fourth control circuit 4097.

[0066] The fourth control circuit 4097 collects measurement results regarding the DC bus 405 output from the voltmeter 406 and ammeter 407, measurement results regarding the AC system output from the voltmeter 410 and ammeter 411, and status information of the first DC / DC conversion circuit 403 output from the first control circuit 404, and notifies the information to the CEMS 31, etc. via the communication interface 412.

[0067] The fourth control circuit 4097 also notifies the CEMS 31 and the like of various control parameters of the virtual synchronous generator control circuit 4093, the inverter current control circuit 4094 (more specifically, the first PI control circuit 40942 and the second PI control circuit 40945), and the inverter voltage control circuit 4095 (more specifically, the third PI control circuit 40953 and the first current limiting circuit 40955) described above via the communication interface 412. Furthermore, the fourth control circuit 4097 also notifies the CEMS 31, via the communication interface 412, of the effective voltage of the AC system measured by an AC system effective voltage measurement unit (not shown), and information on active power and reactive power measured by an AC system active / reactive power measurement unit (not shown). Furthermore, the fourth control circuit 4097 also notifies the third control circuit 4044 of the measurement results of the effective voltage, active power, and the like of the AC system.

[0068] Fig. 8 is a block diagram illustrating the configuration of the AC frequency detection circuit 4091 shown in Fig. 7. Referring to Fig. 8, the AC frequency detection circuit 4091 includes a phase detection circuit 40910, a frequency detection circuit 40911, and a first sine wave generation circuit 40912.

[0069] The phase detection circuit 40910 detects zero-crossing points from the voltage waveform of the AC system output from the voltmeter 410. The frequency detection circuit 40911 detects the frequency based on the zero-crossing point detection result of the phase detection circuit 40910. It goes without saying that the phase detection method used by the phase detection circuit 40910 is not limited to zero-crossing point detection. Furthermore, when detecting zero-crossing points in an actual device, errors occur due to errors in detecting the zero point of the voltmeter 410 (mainly offset errors), errors in detecting the amplitude of the voltmeter 410 (mainly linearity errors), errors in the sampling period when sampling the system AC voltage waveform (for example, variations in the time from carrier interrupt to actual sampling when sampling is performed using a microcomputer, etc.), and the like. It goes without saying that the phase detection circuit 40910 may be configured to correct for these errors and detect the zero-crossing points.

[0070] The first sine wave generating circuit 40912 generates a sine wave synchronized with the AC system voltage based on the zero-cross point detection result from the phase detection circuit 40910, the frequency detection result from the frequency detection circuit 40911, and the system AC voltage amplitude output from the CEMS 31. The AC frequency detection circuit 4091 outputs the zero-cross point detection result (i.e., the zero-cross point detection time), the frequency detection result, and information related to the sine wave (i.e., the voltage, frequency, phase, and sine wave waveform).

[0071] Fig. 9 is a block diagram illustrating the configuration of inverter current control circuit 4094 shown in Fig. 7. Referring to Fig. 9, inverter current control circuit 4094 includes a subtractor 40941, a first PI control circuit 40942, a multiplier 40943, a subtractor 40944, a second PI control circuit 40945, and a first PWM conversion circuit 40946.

[0072] The inverter current control circuit 4094 generates a control command value for controlling the first DC / AC conversion circuit 408 based on the DC voltage of the DC bus 405 output from the voltmeter 406. The DC voltage of the DC bus 405 output from the voltmeter 406 is subtracted by a subtractor 40941 from the target value of the DC bus voltage output from the fourth control circuit 4097, and the result is input to the first PI control circuit 40942. The first PI control circuit 40942 outputs a command value based on the control parameters (i.e., proportional gain and integral time) output from the fourth control circuit 4097 so that the DC voltage of the DC bus 405 becomes a predetermined value.

[0073] The command value output from the first PI control circuit 40942 is multiplied by a sine wave synchronized with the AC voltage waveform (i.e., sine wave waveform) output from the first sine wave generating circuit 40912 in a multiplier 40943. This generates a current command value. The current command value output from the multiplier 40943 is subtracted by a subtractor 40944 from the current value of the AC system measured by the ammeter 411, and the result is input to a second PI control circuit 40945. The second PI control circuit 40945 outputs a control command value to a first PWM conversion circuit 40946 based on the control parameters (i.e., proportional gain and integral time) output from the fourth control circuit 4097, so that the subtraction result output from the subtractor 40944 becomes zero. When the first PWM conversion circuit 40946 receives a control command value from the second PI control circuit 40945 , it performs PWM modulation and outputs the result as a command value to the first DC / AC conversion circuit 408 .

[0074] As described above, the fourth control circuit 4097 also notifies the control parameters of the first PI control circuit 40942 and the second PI control circuit 40945 .

[0075] Fig. 10 is a block diagram illustrating the configuration of inverter voltage control circuit 4095 shown in Fig. 7. Referring to Fig. 10, inverter voltage control circuit 4095 includes a second sine wave generating circuit 40951, a subtractor 40952, a third PI control circuit 40953, a first current limiting circuit 40955, and a second PWM conversion circuit 40954.

[0076] The inverter voltage control circuit 4095 outputs a control command value for controlling the first DC / AC conversion circuit 408 based on frequency and phase information output from a virtual synchronous generator control circuit 4093, the details of which will be described later, and amplitude information of the AC system voltage output from a fourth control circuit 4097 (in the first embodiment, this information is input via a first sine wave generating circuit 40912).

[0077] The sine wave information (i.e., frequency, phase, and amplitude information) from the AC frequency detection circuit 4091 and the frequency and phase information from the virtual synchronous generator control circuit 4093 are input to the second sine wave generation circuit 40951. However, in the first embodiment, the virtual synchronous generator control circuit 4093 does not perform QV control (reactive power-voltage control), so the amplitude is not controlled. The second sine wave generation circuit 40951 generates a target value of the AC system voltage to be output from the first DC / AC conversion circuit 408 based on the input frequency, phase, and amplitude information.

[0078] The subtractor 40952 subtracts the voltage measured by the voltmeter 410 from the output of the second sine wave generating circuit 40951 and outputs the subtraction result to the third PI control circuit 40953. The third PI control circuit 40953 generates a voltage command by PI control so that the input subtraction result becomes zero, and outputs the generated voltage command to the first current limiting circuit 40955. The control parameters of the third PI control circuit (i.e., control gain and integral time) are output from the fourth control circuit 4097. The first current limiting circuit 40955 limits the command value output from the third PI control circuit 40953 based on the measurement result of the ammeter 411 input via the fourth control circuit 4097. The command value output from the first current limiting circuit 40955 is PWM modulated by the second PWM conversion circuit 40954 and then output to the first DC / AC conversion circuit 408.

[0079] Fig. 11 is a block diagram illustrating the configuration of the virtual synchronous generator control circuit 4093 shown in Fig. 7. Referring to Fig. 11, the virtual synchronous generator control circuit 4093 includes a subtractor 40932, a governor control circuit 40933, an adder 40935, a subtractor 40936, and a mass system calculation circuit 40937.

[0080] The subtractor 40932 subtracts the frequency command value (Fref) output from the fourth control circuit 4097 from the actual measurement result of the frequency. The output of the subtractor 40932 is input to the governor control circuit 40933. The detailed operation of the governor control circuit 40933 will be described later. The adder 40935 generates a control power target value (command value) for the mass system calculation circuit 40937 by adding an offset value to be added to the power target value (command value) output from the governor control circuit 40933 and the power command value (Pref) output from the fourth control circuit 4097.

[0081] The subtractor 40936 subtracts the effective power output from the effective power calculation circuit 4092 from the control power target value (command value) output from the adder 40935. The output of the subtractor 40936 is input to the mass system calculation circuit 40937. As will be described in detail later, the mass system calculation circuit 40937 calculates the frequency and phase of the AC system voltage output from the battery power conversion device 41 so that the output of the subtractor 40936 becomes zero. In the first embodiment, the control parameters (speed adjustment rate Kgd, governor time constant Tg, inertia constant M, and damping coefficient Dg) of the governor control circuit 40933 and the mass system calculation circuit 40937 are notified from the CEMS 31 and are notified via the fourth control circuit 4097.

[0082] Fig. 12 is a block diagram illustrating the configuration of the governor control circuit 40933 shown in Fig. 11. Referring to Fig. 12, the governor control circuit 40933 includes a multiplier 409331, a first-order lag model (denoted as 1 / (1+s×Tg) in the figure) 409332, and a limiter circuit 409333.

[0083] Multiplier 409331 multiplies the output of subtractor 40932 by the proportional gain (denoted as -1 / Kgd in the figure) output from fourth control circuit 4097. The output of multiplier 409331 is output to first-order lag model 409332. In this first embodiment, a case will be described in which governor control uses the first-order lag standard model proposed by the Institute of Electrical Engineers of Japan (IEEE). Therefore, first-order lag model 409332 implements a first-order lag model (i.e., 1 / (1+s×Tg)) as shown in FIG. 12. The output of first-order lag model 409332 is subjected to limiter processing by limiter circuit 409333 and then output.

[0084] Fig. 13 is a block diagram illustrating the configuration of the mass point system calculation circuit 40937 shown in Fig. 11. Referring to Fig. 13, the mass point system calculation circuit 40937 includes a subtractor 409371, an integrator (denoted as 1 / (M×s) in the figure) 409372, a multiplier 409373, a divider 409374, an adder 409375, and a phase calculation circuit 409376.

[0085] Subtractor 409371 subtracts the output of multiplier 409373 from the output of subtractor 40936 in FIG. 11 (i.e., the result of subtracting the measured effective power from the power target value (command value)). The subtraction result is input to integrator 409372. Integrator 409372 generates the difference value (Δω) between the generator rotor angular velocity and the generator rotor angular velocity command value shown in FIG. 42 by multiplying the output of subtractor 409371 by 1 / M and integrating it. In this first embodiment, the frequency command value is set to 60 [Hz]. Therefore, the angular velocity command value is 2 × π × 60 [rad / s]. The output of integrator 409372 is input to multiplier 409373, where it is multiplied by a damping coefficient Dg output from fourth control circuit 4097. The subtractor 409371 subtracts the output of the multiplier 409373 from the output of the subtractor 40936 , and the mass system calculation circuit 40937 simulates the braking force of the synchronous generator in the control of the first DC / AC conversion circuit 408 .

[0086] [Correction based on Rule 91 05.11.2024] The output (Δω) of integrator 409372 is converted into frequency difference information (Δf) by dividing it by 2 × π in divider 409374. The frequency difference information (Δf) is converted into the generator rotor frequency (rotational frequency) by adding it to the frequency target value (60 Hz) in adder 409375. The output of adder 409375 is input to phase calculation circuit 409376, which calculates the phase of the generator rotor based on information from fourth control circuit 4097 (i.e., zero-cross detection information, frequency detection information, new power supply start command, etc.).

[0087] Next, we will explain the transfer function of the oscillation equation part of the mass system calculation circuit 40937. The transfer function of the oscillation equation part can be expressed as a first-order lag system having a proportional gain of 1 / Dg and a time constant of M / Dg, as shown in the following equation (3). Note that the governor time constant (Tg) and the mass system calculation part time constant (M / Dg) in the virtual synchronous generator control circuit 4093 are determined based on the response speed required for the system.

[0088]

[0089] Fig. 43 is a block diagram shown for calculating the transfer function F(s) of the virtual synchronous generator control circuit 4093 shown in Fig. 11. The transfer function F(s) (i.e., Δf / ΔP) of the block diagram shown in Fig. 43 is expressed by the following equation (4).

[0090]

[0091] Therefore, according to the final value theorem, the following equation (5) holds: Equation (5) corresponds to the gradient of the drooping characteristic of the virtual synchronous generator control unit (i.e., 1 / (2×π×Dg+1 / Kgd)).

[0092]

[0093] [Outline of Operation of Distributed Power Supply Management Apparatus] Next, an outline of operation of the distributed power supply management apparatus according to the first embodiment will be described with reference to FIGS. 14 to 19. FIG.

[0094] FIG. 14 is a diagram showing the range covered by the virtual synchronous generator control implemented in the battery power conversion device 41. In FIG. 14, the horizontal axis represents the response time, and the vertical axis represents the demand fluctuation range. As shown in the figure, the virtual synchronous generator control implemented in the static inverter covers minute fluctuations of tens of milliseconds to several minutes, as well as short-period fluctuations. Control lasting more than several minutes is handled by load frequency control (LFC) or economic load dispatching control (EDC). Therefore, in the following description of the first embodiment, the response performance of the virtual synchronous generator control circuit 4093 is assumed to be less than one second.

[0095] FIG. 15 is a diagram illustrating an example of the drooping characteristic of the virtual synchronous generator control described in the first embodiment. The horizontal axis of FIG. 15 represents frequency, and the frequency command value (Fref) is shown. In this disclosure, the difference between the measured frequency (Fmeasure) and the frequency command value is referred to as Δfrequency (Fmeasure-Fref). The vertical axis of FIG. 15 represents the difference (Δpower) between the power command value (Pref) and the measured effective power (Pmeasure). Equation (5) shows the slope of the drooping characteristic shown in FIG. 15. For ease of explanation, the diagram illustrates an example in which the power command value (Pref) is set to "zero." The drooping characteristic is adjusted so that the power command value (Pref) is obtained at the frequency command value (Fref).

[0096] Next, we will briefly explain the drooping characteristics of a power distribution system (i.e., the drooping characteristics of a main power system). Generally, the upper and lower limits of the frequency of the AC system voltage of a main power system are approximately 1 to 2% of the system frequency (i.e., the rated frequency). Therefore, when the system frequency is 60 Hz, the upper limit frequency is approximately 61.2 to 60.6 Hz, and the lower limit frequency is approximately 59.4 to 58.8 Hz. Furthermore, the frequency of the power distribution system is constantly changed within the above frequency range.

[0097] Fig. 16 shows an example of the results of measuring the frequency of a power distribution system voltage over 25 hours at a cycle of 1 second. As shown in the figure, it can be seen that the frequency fluctuates constantly within ±0.2 Hz around 60 Hz.

[0098] [Correction based on Rule 91, 13.03.2025] Figure 17 is a diagram showing an example of the drooping characteristics of the battery power converter 41 in the distribution system 1 according to the first embodiment. In the figure, the horizontal axis represents the frequency of the AC system voltage, and the vertical axis represents power. Fmax on the horizontal axis represents the maximum possible frequency of the battery power converter 41, and Fmin represents the minimum possible frequency of the battery power converter 41. 60.1 Hz represents the maximum possible frequency of the distribution system voltage, and 59.9 Hz represents the minimum possible frequency of the distribution system voltage. Hereinafter, the frequency range of the distribution system voltage is also referred to as the rated frequency range. Fref represents the frequency command value for virtual synchronous generator control, and Pref represents the power command value. Note that in the first embodiment, the upper and lower limits of the frequency of the distribution system voltage are ±0.1 Hz. For simplicity, the first embodiment will be described assuming that the battery power converter 41 only discharges power. It goes without saying that the upper and lower limits of the frequency of the distribution system voltage are not limited to ±0.1 Hz, but may be, for example, ±0.2 Hz, which is the target of major electric power companies, or upper and lower limit values ​​of frequency (for example, ±0.15 Hz) determined by the distribution system operator of the microgrid when constructing the microgrid.

[0099] Here, when a static inverter (operating as a voltage source) implementing virtual synchronous generator control is connected to a utility grid, when multiple static inverters (each operating as a voltage source) each implementing virtual synchronous generator control are connected to an independent grid, or when multiple types of main power sources (operating as voltage sources) such as synchronous generators are connected to an independent grid, a large damping factor Dg is required to ensure stable operation of the static inverter (operating as a voltage source) implementing virtual synchronous generator control. Increasing the damping factor Dg narrows the frequency range ΔF that can be covered by the drooping characteristic of the virtual synchronous generator control, as shown in Equation (5). As a result, the frequency range (Fmin to Fmax) covered by the drooping characteristic of the virtual synchronous generator control becomes narrower compared to the rated frequency range of the AC grid voltage (59.9 Hz to 60.1 Hz in the first embodiment), as shown in FIG. 16 . As a result, when the frequency of the grid AC voltage becomes lower than Fmin or higher than Fmax, the battery power conversion device 41 cannot maintain operation and shuts down. For example, if Fmin is 59.95 Hz and the frequency of the system AC voltage is 59.94 Hz, the voltage phase will shift by the difference between the frequency of the AC system voltage that the battery power conversion device 41 can output and the frequency of the system AC voltage, which will cause the battery power conversion device 41 to stop for protection purposes.

[0100] FIG. 18 is a diagram for explaining a method for generating a frequency command value (Fref) in the distributed power management apparatus according to the first embodiment. As will be described in detail later, in the first embodiment, when the CEMS 31 generates the frequency command value Fref for each storage battery power conversion device 41, the operation plan generation circuit 314 shown in FIG. 2 generates a power command value Pref (i.e., operation plan power command value information) for each storage battery power conversion device 41. After completing the generation of the power command value Pref, the CEMS 31 generates a drooping characteristic by assuming that the frequency command value Fref is equal to the rated frequency (e.g., 60 Hz) of the utility grid, as shown in part A of FIG. 18 . Then, the CEMS 31 compares the frequency command value Fref with the actual measurement result (Fmeasure) of the AC system voltage collected by the AC frequency collection circuit 313. If, for example, Fmeasure is lower than Fmin, the current drooping characteristic will shut down the storage battery power conversion device 41, as described above. In this first embodiment, in such a case, the details will be described later, but for example, as shown in part B of the figure, CEMS 31 sets the frequency command value Fref to the actual measurement result (Fmeasure) and notifies the storage battery power conversion device 41. In this case, as shown in the figure, the drooping characteristic shifts to the left, allowing the storage battery power conversion device 41 to continue operating.

[0101] Next, the effect of the above-described method for generating a frequency command value will be described with reference to FIGS. 19A and 19B . FIG. 19A illustrates a frequency command value when a drooping characteristic of a comparative example is used. This figure shows a case in which the load decreases over time and the frequency of the AC grid voltage increases in a ramp-like manner. As shown in the figure, when the frequency command value (Fref) is constant at the rated frequency (60 Hz) of the utility grid, the area inside the thick dashed line corresponds to the frequency range (also referred to as the frequency management range) of the battery power conversion device 41 (inverter). As shown in the figure, as the frequency of the grid voltage gradually increases, the frequency of the grid voltage deviates from the inverter frequency range that can be controlled by the battery power conversion device 41 (inverter) (the NG region in the figure), causing the virtual synchronous generator control (VSG control) to fail and the battery power conversion device 41 to stop.

[0102] 19B is a diagram showing a frequency command value when the drooping characteristic of the first embodiment is used. As shown in the figure, the frequency command value (Fref) is controlled based on the actual measurement result of the frequency of the AC system voltage. Specifically, in the first embodiment, the frequency of the AC system voltage is measured at one-minute intervals, and the frequency command value (Fref) is controlled based on the measurement result, as will be described in detail later. As shown in the figure, since the frequency command value (Fref) is appropriately controlled based on the frequency of the AC system voltage, even if the frequency of the system voltage gradually increases, the actual system frequency does not deviate from the frequency management range of the power conversion device 41 (inverter) for the storage battery, and grid-connected operation can be continued.

[0103] As described above, when a power conversion device having a static inverter implementing a droop characteristic (i.e., a droop characteristic) represented by virtual synchronous generator control is connected to an AC system, the distributed power management device is configured to generate a frequency command value (Fref) of the droop characteristic (i.e., a droop characteristic) based on the frequency of the AC system voltage. This has the effect of enabling the power conversion device to be controlled without the measured system frequency deviating from the frequency management range of the power conversion device having a static inverter implementing the droop characteristic (i.e., a droop characteristic) even if the frequency of the main system deviates from the rated frequency (e.g., 60 Hz).

[0104] [Details of Operation of the Distributed Energy Management System (CEMS)] Next, the operation of the distributed energy management system (CEMS 31) according to the first embodiment will be described in detail with reference to FIGS. 1 to 30. Referring again to FIG. 1, the power distribution system to which the distributed energy management system according to the first embodiment is connected will be described. In the first embodiment, the power distribution system 1 includes three SVRs 23 connected in series to the distribution line 24 m between the substation 20 and the mega solar power conversion device 27 (or the storage battery power conversion device 41 a, town D 100 d) in order to control the distribution system voltage output from the substation 20 within a predetermined voltage range. Furthermore, a storage battery power conversion device 41 a is installed near the mega solar power conversion device 27. In the first embodiment, the storage battery power conversion device 41 a operates as a voltage source, and the mega solar power conversion device 27 operates as a current source. The mega solar power conversion device 27 also adjusts fluctuations in the power generated by the mega solar power plant 26 by operating a virtual synchronous generator control circuit 4093.

[0105] The loads include town A 100a, town B 100b, town C 100c, town D 100d, factory 101, building 102, and apartment building 103. These loads are supplied with power from substation 20, power generated by mega solar power plant 26, and power from storage batteries 40a to 40c. A synchronous generator 30a is provided in factory 101, and a synchronous generator 30b is provided in building 102 for emergency use.

[0106] The operation of the power distribution system for controlling the power supplied from the substation 20, the power generated by the mega solar 26, and the discharged power output from the storage batteries 40a to 40c will be described below.

[0107] Fig. 20 is a sequence diagram of the normal operation of the distributed power management system centered on the CEMS 31 shown in Fig. 1. As shown in the figure, the steady-state processing of the distributed power management system includes two processes: process P1 performed every 30 minutes and process P2 performed every 1 minute.

[0108] In the figure, when the 30-minute cycle process P1 starts, the DSO 21 requests the CEMS 31 to output the collected measurement data via the communication line 25 (F1). Upon receiving the request from the DSO 21, the CEMS 31 transmits measurement data output requests to the storage battery power converter 41, the voltmeter 22, and each consumer (including the mega solar power converter 27) (F2, F4) and collects the latest measurement information (F3, F5). The CEMS 31 then sums up the 30 sets of data collected at one-minute intervals to calculate the amount of power consumed by each consumer, the amount of power generated by the mega solar power plant 26, and the amount of power charged and discharged by the storage battery 40 over a 30-minute period, and transmits this information together with information such as the SOC (State of Charge) of the storage battery 40 to the DSO 21 (F6).

[0109] [Correction based on Rule 91 05.11.2024] Upon receiving the measurement results, DSO 21 creates a 24-hour, 30-minute demand plan (i.e., the total power supply to be supplied to the distribution system 24 via the substation 20 in 30 minutes) required to create an operation plan for the storage battery 40, and notifies the CEMS 31 of the created plan (F7). Upon receiving the information used to create the operation plan for the storage battery, CEMS 31 creates an operation plan for the storage battery 40 and control parameters (i.e., a power command value (Pref), a frequency command value (Fref), etc.) based on the SOC information, SOH (State of Health) information for the storage battery 40, forecast information on the power generation of the mega solar power plant 26 (details will be described later), and forecast information on consumer demand (details will be described later) collected earlier (F8). The method for creating the operation plan and control parameters will be described later. When the creation of the operation plan and control parameters for the storage battery 40 is completed, the CEMS 31 transmits the operation plan and control parameters to each storage battery power conversion device 41 (F9), and ends the 30-minute cycle process P1.

[0110] In addition, in process P2, which is performed every minute, the CEMS 31 requests each storage battery power converter 41 and the voltmeter 22 to output measurement data (F10, F12), thereby collecting measurement data from these devices (F11, F13). Based on the collected data, the CEMS 31 checks the difference between the power command value (Pref) and the actual charging / discharging power, and the difference between the frequency command value Fref and the measured frequency of the distribution system voltage (Fmeasure), and determines whether the operation plan and / or control parameters (Pref, Fref, etc.) need to be modified (F14). In the first embodiment, if the difference is equal to or greater than a predetermined value, the CEMS 31 recalculates the operation plan and / or control parameters (Pref, Fref, etc.) (F15) and notifies each storage battery power converter 41 of the recalculation results (F16). A specific recalculation processing method will be described later.

[0111] Next, detailed operation of the CEMS 31 will be described with reference to FIG. 21 . FIG. 21 is a flowchart illustrating the control process of the CEMS 31 shown in FIG. 1 . In this figure, when the process starts, the CEMS 31 checks in step S101 whether it has received a measurement data transmission request from the DSO 21. If the CEMS 31 has received an output request (YES in step S101), it transmits a measurement data output request to the storage battery power conversion device 41, the voltmeter 22, and each consumer (including the mega solar power conversion device 27) in the next step S102, thereby collecting the latest measurement information from these devices. Then, using 30 sets of measurement data collected at one-minute intervals, the CEMS 31 calculates the amount of power consumed by each consumer, the amount of power generated by the mega solar power plant 26, and the amount of power charged and discharged by the storage battery 40 over a 30-minute period, and stores the calculated amounts of power in the memory circuit 312. These data stored in the memory circuit 312 correspond to the measurement data requested to be transmitted by the DSO 21 in step S101. In the next step S103 , the CEMS 31 transmits the measurement data stored in the memory circuit 312 together with information such as the SOC of the storage battery 40 to the DSO 21 via the communication circuit 311 .

[0112] After transmitting the measurement data to the DSO 21 in step S103, or if the CEMS 31 has not received a measurement data transmission request from the DSO 21 in step S101 (No in step S101), the CEMS 31 proceeds to step S104. In step S104, the CEMS 31 checks whether or not it has received a demand plan notification from the DSO 21. If the CEMS 31 has received a demand plan, the CEMS 31 creates an operation plan in the next step S105. In the first embodiment, the DSO 21 notifies the CEMS 31 of a 24-hour supply and demand plan for power supplied from the main system to the distribution system 1 at 30-minute intervals. The operation plan creation process will be described in detail below with reference to FIG. 22 .

[0113] FIG. 22 is a flowchart showing detailed operations of the operation plan creation process in step S105 of the flowchart shown in FIG. 21. In FIG. 22, when creation of an operation plan starts, the CEMS 31 first predicts the amount of power generated by the mega solar power plant 26 in step S1051. Specifically, referring again to FIGS. 2 and 3, when the control circuit 318 in the CEMS receives a notification of a demand plan (storage battery operation plan) from the DSO 21, it instructs the management circuit 3146 in the operation plan creation circuit 314 to create an operation plan. Upon receiving this instruction, the management circuit 3146 instructs the power generation amount prediction circuit 3142 via the storage battery operation plan generation circuit 3141 to predict the power generation power of the mega solar power plant 26. Upon receiving this instruction, the power generation amount prediction circuit 3142 obtains a 24-hour weather forecast from a weather forecast server located on the Internet (not shown). The power generation amount prediction circuit 3142 predicts the amount of power generation for 24 hours using the weather forecast and data in a power generation amount prediction database (not shown) managed by the power generation amount prediction circuit 3142. The power generation amount prediction database (not shown) is constructed based on, for example, the actual power generation amount of the mega solar power plant 26, actual weather information, and time information (year, month, date, time information) collected every 30 minutes. The details of how the database is constructed are not relevant to the main point of this application, so their explanation will be omitted.

[0114] After the prediction of the power generation amount of the mega solar power plant 26 in step S1051 described above is completed, the CEMS 31 predicts the power consumption of the consumer in step S1052 of FIG. 22 . Specifically, referring back to FIG. 3 , the management circuit 3146 in the operation plan creation circuit 314 receives the power generation amount prediction result of the mega solar power plant 26 from the power generation amount prediction circuit 3142 and instructs the power consumption prediction circuit 3143 to predict the power consumption of the consumer via the battery operation plan generation circuit 3141. Upon receiving this instruction, the power consumption prediction circuit 3143 predicts the power consumption of the consumer for 24 hours using data in a power consumption prediction database (not shown) managed by the power consumption prediction circuit 3143. Note that the power consumption prediction database (not shown) is constructed based on, for example, the power consumption of the consumer collected at 30-minute intervals, date, time information, and weather information. Details of the database construction method are not relevant to the present invention and will not be described here. Note that steps S1051 and S1052 may be executed first, or may be executed in parallel.

[0115] When the prediction of the power consumption of the consumers in step S1052 described above is completed, the CEMS 31 starts creating a demand plan in step S1053 of FIG. 22. Specifically, referring again to FIG. 3, when the storage battery operation plan generation circuit 3141 in the operation plan creation circuit 314 receives the prediction result of the power consumption of the consumers from the power consumption prediction circuit 3143, the storage battery operation plan generation circuit 3141 calculates the total value of the charging and discharging power of the storage batteries 40a to 40c every 30 minutes based on the power generation amount prediction result of the mega solar power plant 26 from the power generation amount prediction circuit 3142, the prediction result of the power consumption of the consumers from the power consumption prediction circuit 3143, and the demand plan notified by the DSO 21. Note that, as described above, in the case of the first embodiment, the demand plan notified by the DSO 21 is a 24-hour power supply plan (i.e., a power supply plan every 30 minutes) planned for the distribution system 1 on the load side of the substation 20.

[0116] 22, the CEMS 31 determines the charge / discharge power of the storage batteries 40a to 40c in the next step S1054. Specifically, referring again to FIG. 2 and FIG. 3, the operation plan creation circuit 314 determines (pro rata) the charge / discharge power from each storage battery 40a to 40c every 30 minutes based on the SOC information of the storage batteries 40a to 40c and the storage battery capacities of the storage batteries 40a to 40c collected in the memory circuit 312 via the communication circuit 311.

[0117] In the first embodiment, when planning the operation of the storage batteries for 24 hours, the operation plan creation circuit 314 creates an operation plan so that the SOCs of the storage batteries 40a to 40c reach zero at approximately the same time, or so that they are simultaneously capable of being charged and discharged 24 hours later. This is for the following reason. For example, assume that clouds pass over the mega solar power plant 26 (e.g., 10 MW) and the power generation drops (from 10 MW to 4 MW) for, e.g., about 5 minutes. Furthermore, assume that the static inverter capacities of the storage battery power conversion devices 41a to 41c are 8 MW, 4 MW, and 2 MW, respectively. Here, assume that the SOC of the storage battery 40a has reached zero and is in a stopped state, and that the storage battery operation plan is notified to discharge 1 MW and 0.5 MW from the storage batteries 40b and 40c, respectively. In this case, due to the sudden change in solar radiation, the discharge power from batteries 40b and 40c can only be output by an additional 3 MW and 1.5 MW, respectively, under virtual synchronous generator control, and the shortfall of 6 MW cannot be covered. On the other hand, if batteries 40a to 40c are operating, they can discharge up to 14 MW, which widens the power range that can be covered by virtual synchronous generator control compared to the 6 MW case in the previous example. Therefore, when creating an operation plan for battery 40 in CEMS 31, it is necessary to create an operation plan so that the SOC of batteries 40a to 40c reaches zero or becomes fully charged at approximately the same time.

[0118] 22, when the charge / discharge power of the storage batteries 40a to 40c is determined, in the next step S1055, the AC frequency collection circuit 313 in the CEMS 31 acquires the frequency of the power distribution system voltage and calculates an average value (Fmeasure) as a representative value. As described above, in the first embodiment, the voltmeters 22a to 22x calculate the frequency at each point from the measured AC system voltage, and the AC frequency collection circuit 313 calculates and outputs the average value of the frequency.

[0119] 22, when collection of the frequency of the power distribution system voltage and calculation of the representative value (Fmeasure) are completed, the control circuit 318 in the CEMS checks in the next step S1056 whether or not control parameters (i.e., power command values ​​and frequency command values) for all of the storage battery power conversion devices 41 have been generated. If the answer is NO in step S1056, in the next step S1057, the control circuit 318 in the CEMS generates a frequency command value (Fref). Below, with reference to FIG. 23, the flow of generating the frequency command value (Fref) in step S1057 will be described.

[0120] 23 is a flowchart showing the procedure for generating a frequency command value (Fref). In Fig. 23, when the flow for generating the frequency command value (Fref) is started, in the first step S10571, the frequency command value generation circuit 315 shown in Fig. 2 issues an instruction to the CEMS control circuit 318 to acquire the control parameters (i.e., drooping characteristics) of the storage battery power conversion device 41 for which the current frequency command value (Fref) is to be generated.

[0121] Upon receiving the instruction from the frequency command value generating circuit 315, the CEMS control circuit 318 acquires the drooping characteristic from the distributed power supply drooping characteristic management circuit 316. In the first embodiment, the CEMS control circuit 318 acquires, as control parameters, the speed adjustment ratio (Kgd) of the virtual synchronous generator control, the governor time constant (Tg), the inertia constant (M), the damping coefficient (Dg), and the capacity (inverter capacity) of the first DC / AC conversion circuit 408. It goes without saying that the drooping characteristic information is not limited to the above and may be table data indicating the relationship between ΔP (i.e., power command value (Pref) - Pmeasure (actual measured value of active power)) output from the first DC / AC conversion circuit 408 and ΔF (i.e., frequency command value (Fref) - actual measured value of AC system voltage (Fmeasure)) output from the first DC / AC conversion circuit 408, or data such as the slope of the drooping characteristic. In other words, the drooping characteristic information may be the shape of the drooping characteristic or a parameter that determines the shape of the drooping characteristic.

[0122] After completing step S10571, the frequency command value generation circuit 315 instructs the CEMS control circuit 318 to generate upper and lower limit values ​​for the frequency of the AC system voltage, determined by the drooping characteristic, in step S10572. In this first embodiment, a case will be described in which virtual synchronous generator control is used as the drooping characteristic. In virtual synchronous generator control, ΔF can be calculated using the above-described equation (5). Therefore, in this first embodiment, the upper limit value Fmax of the frequency and the lower limit value Fmin of the frequency can be calculated by substituting the speed adjustment rate Kgd, the damping coefficient Dg, and the minimum and maximum values ​​of ΔP into equation (5). In this first embodiment, the minimum value of ΔP is calculated by subtracting the maximum discharge power from the power command value (Pref). Meanwhile, the maximum value of ΔP is calculated by subtracting the power command value (Pref) from 0, assuming that the first DC / AC conversion circuit 408 is not charging.

[0123] When the generation of the upper and lower limit values ​​of the frequency of the AC system voltage in the drooping characteristic in step S10572 is completed, the frequency command value generation circuit 315 checks in the next step S10573 whether the actually measured frequency of the AC system voltage is within the frequency reference range (see FIG. 24 ) determined by the upper and lower limit frequencies of the drooping characteristic. The operation of step S10573 will be described below with reference to FIG. 24 .

[0124] FIG. 24 is a diagram showing an example of the drooping characteristic of the storage battery power converter 41 in the distributed power management system of the first embodiment. In the diagram, the horizontal axis represents the frequency of the distribution system voltage, and the vertical axis represents the discharge power output from the storage battery power converter 41. For simplicity of explanation, in the first embodiment, it is assumed that the storage battery power converter 41 does not perform charging. In the diagram, Fmax and Fmin represent the upper and lower limit frequencies of the drooping characteristic. In the first embodiment, the frequency reference range determined by the upper and lower limit frequencies Fmax and Fmin is the range that is inward from the upper limit frequency Fmax and the lower limit frequency Fmin by the frequency offset F_offset. It goes without saying that the frequency offset F_offset may have different values ​​on the upper and lower limit sides, or may be changed depending on the value of the power command value (Pref).

[0125] In FIG. 24, the frequency command value generation circuit 315 selects NO in step S10573 when the representative value of the actual measured frequency (Fmeasure) output from the AC frequency collection circuit 313 deviates from the frequency reference range determined by the upper and lower limit frequencies (*1 in the figure), and selects YES when the representative value of the actual measured frequency (Fmeasure) is within the frequency reference range determined by the upper and lower limit frequencies (*2 in the figure).

[0126] If the answer is YES in step S10573, then in the next step S10575, the frequency command value generation circuit 315 sets the frequency command value (Fref) to the rated frequency of the power grid (for example, 60 Hz), and the frequency command value (Fref) generation process ends. On the other hand, if the answer is NO in S10573, then in the next step S10574, the frequency command value generation circuit 315 generates the frequency command value (Fref). The operation of step S10574 will be described below with reference to FIG. 25.

[0127] FIG. 25 is a flowchart showing the procedure for generating a frequency command value (Fref) in step S10574 of FIG. 23 . In the first step S105741 of FIG. 25 , the frequency command value generation circuit 315 generates a drooping characteristic by setting Fref = Fmeasure, and calculates upper and lower limit frequencies of the AC system voltage frequency based on the generated drooping characteristic. Specifically, the upper and lower limit frequencies can be calculated in the same manner as in step S10572 of FIG. 23 . That is, the frequency command value generation circuit 315 calculates the upper limit value Fmax of the frequency and the lower limit value Fmin of the frequency by substituting the speed adjustment rate Kgd, the damping coefficient Dg, the minimum value of ΔP, and the maximum value of ΔP into equation (5) (corresponding to part B of FIG. 26 ). Here, as described above, in the first embodiment, the minimum value of ΔP is calculated by subtracting the power command value (Pref) from the maximum discharge power. In the first embodiment, the maximum value of ΔP is equal to the power command value (Pref) on the assumption that the first DC / AC conversion circuit 408 does not perform charging.

[0128] After step S105741 is completed, the frequency command value generation circuit 315 checks in the next step S105742 whether the upper and lower limit frequencies of the drooping characteristic are within the upper and lower limit values ​​of the frequency of the AC system voltage (i.e., whether they are within a predetermined rated frequency range). In the first embodiment, the upper and lower limit values ​​of the frequency of the AC system voltage are set to 60.1 Hz to 59.9 Hz. If the answer is YES in step S105742, the frequency command value generation circuit 315 sets the frequency command value (Fref) to Fmeasure and ends the calculation procedure for the frequency command value (Fref). On the other hand, if the answer is NO in step S105742, the frequency command value generation circuit 315 corrects the frequency command value (Fref) in the next step S105743. The operation of step S105743 will be described below with reference to FIG. 26.

[0129] FIG. 26 is a diagram illustrating a procedure for correcting a frequency command value. As shown in part A of FIG. 26 , assume that when the frequency command value (Fref) is 60 Hz, the representative value (Fmeasure) of the frequency of the measured AC system voltage is 59.915 Hz. In this case, if the representative value (Fmeasure) of the measured frequency is set as the frequency command value (Fref) to generate a drooping characteristic, the lower limit frequency of the drooping characteristic falls below the lower limit value (59.9 Hz) of the frequency of the AC system voltage, as shown in part B of FIG. 26 . Therefore, the frequency command value generation circuit 315 corrects the frequency command value (Fref) so that the lower limit frequency of the drooping characteristic coincides with 59.9 Hz, which is the lower limit value of the frequency of the AC system voltage, as shown in part C of FIG. 26 . Specifically, in the drooping characteristic corrected so that the lower limit frequency of the drooping characteristic coincides with the lower limit value of the frequency of the AC system voltage, the frequency at which the output power becomes the power command value (Pref) is set as the frequency command value (Fref).

[0130] The same applies when the upper limit frequency of the drooping characteristic exceeds the upper limit of the frequency of the AC system voltage. In this case, the frequency command value generation circuit 315 corrects the frequency command value (Fref) so that the upper limit frequency of the drooping characteristic matches the upper limit of the frequency of the AC system voltage. Specifically, in the drooping characteristic corrected so that the upper limit frequency of the drooping characteristic matches the upper limit of the frequency of the AC system voltage, the frequency at which the output power becomes the power command value (Pref) is set as the frequency command value (Fref). When step S105743 in FIG. 25 is completed, the CEMS control circuit 318 ends the calculation of the frequency command value (Fref) (step S10574 in FIG. 23).

[0131] Returning to FIG. 22, after completing step S1057, the control circuit 318 in the CEMS returns the processing to step S1056, and thereafter repeats step S1057 until step S1056 becomes YES, that is, until calculation of the frequency command value Fref for all the battery power conversion devices 41 is completed.

[0132] 21 , when the CEMS internal control circuit 318 finishes generating the operation plan in step S105, in the next step S110, it notifies each storage battery power conversion device 41 of the generated operation plan (i.e., the power command value Pref and the frequency command value Fref). In the next step S111, the CEMS internal control circuit 318 determines whether or not to stop operation of the CEMS 31. If step S111 is YES, the CEMS internal control circuit 318 stops operation of the CEMS 31. On the other hand, if step S111 is NO, the CEMS internal control circuit 318 returns to step S101 and repeats the above-described flow.

[0133] Next, a case where step S104 in Fig. 21 is NO will be described. In this case, the CEMS control circuit 318 checks in step S106 whether it is the start time of the one-minute periodic processing. If the result in step S106 is NO, the CEMS control circuit 318 returns the process to step S101 and repeats the above-described flow. On the other hand, if the result in step S106 is YES, the CEMS control circuit 318 proceeds to the next step S107.

[0134] In step S107, the CEMS control circuit 318 collects measurement data from the voltmeter 22, the storage battery power conversion device 41, the mega solar power conversion device 27, and consumer measurement data. After completing collection of the measurement data in step S107, the CEMS control circuit 318 determines whether or not the operation plan needs to be revised in the next step S108. As an example, in the first embodiment, if the SoC notified from the storage battery power conversion device 41 is outside a predetermined range, the CEMS control circuit 318 determines that the operation plan needs to be revised. For example, in the first embodiment, if the SoC exceeds 0.9 during charging or if the SoC is below 0.05 during discharging, the CEMS control circuit 318 determines that the operation plan needs to be revised. Note that an SoC of 1.0 is considered to be fully charged. As another example, the CEMS control circuit 318 determines that the operation plan needs to be modified when the representative value (Fmeasure) of the frequency of the measured grid voltage output from the AC frequency collection circuit 313 deviates from a predetermined range. Step S108 in Fig. 21 will be described in more detail below with reference to Fig. 27.

[0135] 27 is a flowchart showing the procedure for determining whether an operation plan needs to be modified. When the process for determining whether an operation plan needs to be modified is started, the control circuit 318 in the CEMS clears the operation plan modification flag in step S1081. If the operation plan modification flag is set, the control circuit 318 in the CEMS determines in step S108 in FIG. 21 that the operation plan needs to be modified, and if the operation plan modification flag is cleared, the control circuit 318 determines that the operation plan does not need to be modified. In the first embodiment, an operation plan modification flag is prepared for each storage battery power conversion device 41.

[0136] When step S1081 is completed, the CEMS control circuit 318 acquires the representative value Fmeasure of the frequency of the measured system voltage output from the AC frequency collection circuit 313 in the next step S1082.

[0137] In the next step S1083, the charge / discharge power and the SoC are acquired from each storage battery power conversion device 41. Furthermore, in step S1084, the CEMS control circuit 318 acquires the virtual synchronous generator control parameters (drooping characteristics) of each storage battery power conversion device 41 from the distributed power source drooping characteristics management circuit 316.

[0138] In the next step S1085, the CEMS control circuit 318 calculates the upper and lower limit frequencies of the drooping characteristics from the drooping characteristics collected in step S1084 in the manner described in step S10572 of FIG. 23 and step S105741 of FIG.

[0139] After step S1085 is completed, the CEMS control circuit 318 checks whether the SoC is within a predetermined range in the next step S1086. If the SoC is outside the predetermined range, the CEMS control circuit 318 proceeds to step S1088, where it sets a correction flag for the operation plan.

[0140] If the SoC is within the predetermined range (YES in S1086), the CEMS control circuit 318 checks in the next step S1087 whether the representative value of the measured frequency of the power distribution system voltage (Fmeasure) is within the frequency reference range determined by the upper and lower limit frequencies of the drooping characteristics. Here, the frequency reference range is the same as that described in step S10573 of FIG. 23 and in FIG. 24. If the representative value of the measured power system frequency (Fmeasure) is outside the frequency reference range determined by the drooping characteristics (NO in step S1087), the CEMS control circuit 318 proceeds to step S1088, where it sets a correction flag for the operation plan.

[0141] If the operation plan correction flag is set in step S1088, or if it is confirmed in step S1087 that the measured system frequency (Fmeasure) is within the frequency range determined by the drooping characteristics (YES in step S1087), the process proceeds to step S1089. In step S1089, the CEMS control circuit 318 checks whether it has determined whether or not it is necessary to set a correction flag for all of the storage battery power conversion devices 41, and if it has completed determining whether or not it is necessary to set a correction flag for all of the storage battery power conversion devices 41 (YES in step S1089), it ends the process for determining whether or not it is necessary to correct the operation plan. On the other hand, if the result is NO in step S1089, the CEMS control circuit 318 returns the process to step S1083 and repeats the above procedure.

[0142] 21 , if the CEMS control circuit 318 determines in step S108 that the operation plan does not need to be modified (i.e., the operation plan modification flags of all the storage battery power conversion devices 41 are "0") (NO in step S108), the CEMS control circuit 318 returns the process to the initial step S101 and repeats the above-described process. On the other hand, if the CEMS control circuit 318 determines in step S108 that the operation plan needs to be modified (i.e., at least one operation plan modification flag is "1") (YES in step S108), the CEMS control circuit 318 modifies the operation plan in the next step S109. Details of step S109 will be described below with reference to FIG. 28.

[0143] 28 is a flowchart showing the procedure for correcting an operation plan. When the operation plan correction flow starts, the CEMS control circuit 318 checks in step S1091 whether the operation plan correction flag has been set. As described above, in the first embodiment, an operation plan correction flag is provided for each battery power conversion device 41, and a new frequency command value (Fref) and / or a new power command value (Pref) is generated for an operation plan that requires correction.

[0144] If the operation plan correction flag has not been set (NO in step S1091), the process proceeds to step S1098. The process in step S1098 will be described later. On the other hand, if the operation plan correction flag has been set (YES in step S1091), the process proceeds to steps S1092 to S1094. The CEMS control circuit 318 acquires data (charge / discharge power, SoC) measured by the storage battery power conversion device 41 in step S1092, acquires a frequency command value (Fref) and a power command value (Pref) in step S1093, and further acquires a representative value (Fmeasure) of the frequency of the actually measured AC voltage output from the AC frequency collection circuit 313 in step S1094.

[0145] After steps S1092 to S1094 are completed, the CEMS control circuit 318 checks in step S1095 whether the SoC is within a predetermined range. As described above, in the first embodiment, a case where the SoC is outside the predetermined range refers to a case where the SoC exceeds 0.9 during charging or a case where the SoC is below 0.05 during discharging. Here, an SoC of 1.0 corresponds to a full charge. However, cases where the SoC is outside the predetermined range are not limited to this case. For example, when using a lead-acid battery, the lower limit of the SoC during discharging is set to, for example, 0.3 because overdischarging rapidly deteriorates the battery. Furthermore, since lead-acid batteries do not rapidly deteriorate even when overcharged, it goes without saying that the upper limit of the SoC during charging may be set to 1.0 or higher. In this way, the upper and lower limits of the SoC may be determined according to the characteristics of the battery.

[0146] If the SoC of the storage battery is not within the predetermined range (NO in step S1095), the control circuit 318 in the CEMS changes the power command value (Pref) in the next step S1096. In the first embodiment, a data table (not shown) that determines the power command value depending on the SoC value is stored in the CEMS 31, and the control circuit 318 determines the power command value (Pref) based on that information. Note that the method for determining the power command value is not limited to the method based on the data table. For example, the power command value may be changed to a value that will not cause over-discharge or over-charge when the next demand plan is notified from the DSO 21, based on the time until the next demand plan notified from the DSO 21 is received, the SoC value, and the current power command value.

[0147] If the SoC of the storage battery is within the predetermined range (YES in step S1095), or if generation of the power command value (Pref) is completed in step S1096, the process proceeds to step S1097. In step S1097, the CEMS control circuit 318 checks whether the representative value of the measured frequency of the power distribution system voltage (Fmeasure) is within the frequency reference range determined by the upper and lower frequency limits of the drooping characteristic. The frequency reference range is the same as that described in step S10573 of FIG. 23 and FIG. 24.

[0148] If the representative value of the actually measured frequency of the power distribution system voltage (Fmeasure) is not within the frequency reference range (NO in step S1097), the control circuit 318 in the CEMS calculates a frequency command value (Fref) in the next step S10910. Step S10910 in Fig. 28 is the same as step S10574 in Fig. 23, and more specifically, is the same as the flowchart in Fig. 25, so description thereof will not be repeated.

[0149] If the operation plan correction flag is not set (NO in step S1091), or if calculation of the frequency command value (Fref) is completed in step S10910, or if the representative value of the actually measured frequency of the distribution system voltage (Fmeasure) is within the frequency reference range (YES in step S1097), the process proceeds to step S1098. In step S1098, the CEMS control circuit 318 checks whether or not control parameters (Pref, Fref) for all storage battery power conversion devices 41 that require correction have been generated. If generation of all control parameters has been completed (YES in step S1098), the CEMS control circuit 318 ends the operation plan correction flow. On the other hand, if the generation of control parameters for all battery power conversion devices 41 that require modification has not been completed (NO in step S1098), the control circuit 318 in the CEMS changes the processing target to the next battery power conversion device 41 in step S1099, and then returns to the initial step S1091 to execute the above-mentioned processing again.

[0150] Returning to FIG. 21 , when the correction of the operation plan in step S109 described above is completed, or when the creation of the operation plan in step S105 described above is completed, in the next step S110, the CEMS internal control circuit 318 notifies each storage battery power conversion device 41 of the created operation plan (power command value (Pref) and frequency command value (Fref)). Then, in the next step S111, the CEMS internal control circuit 318 determines whether or not to terminate the operation of the CEMS 31. If the operation of the CEMS 31 is to be terminated (YES in step S111), the CEMS 31 stops. On the other hand, if the operation of the CEMS 31 is not to be terminated (NO in step S111), the process returns to the initial step S101, and the above-described process is executed again.

[0151] As described above, in the first embodiment, when an operation plan (i.e., a power command value (Pref) and a frequency command value (Fref)) is created for the storage battery power conversion device 41, the frequency command value (Fref) is generated based on the drooping characteristics of the static inverter in the storage battery power conversion device 41, the created power command value, and the actually measured frequency of the AC grid voltage (Fmeasure). As a result, even if the frequency of the AC grid voltage changes due to a fluctuation (sudden change) in the power generated by an energy generating device such as a renewable energy source and supplied to the power distribution system due to a fluctuation (sudden change) in the power consumption of the load and / or a sudden change in solar radiation, the frequency does not deviate from the frequency range managed by the static inverter that has implemented the virtual generator control characteristics (drooping characteristics), and the like, and the distributed power source can continue to operate without being stopped.

[0152] [Detailed Operation of the Battery Power Converter] Next, the operation of the battery power converter 41 will be described in detail with reference to Figures 5 to 13, 29, and 30. In the first embodiment, the battery power converter 41 implements virtual synchronous generator control, so the first DC / AC conversion circuit 408 operates as a voltage source (i.e., voltage control). Therefore, the first control circuit 404 controls the voltage of the DC bus 405 to be a constant value. The operation of the first control circuit 404 will be described below with reference to Figure 6. The voltage of the DC bus 405 is measured by a voltmeter 406 and input to a charge control circuit 4041, a discharge control circuit 4042, and a third control circuit 4044.

[0153] When the voltage of the DC bus 405 is higher than the target voltage output from the third control circuit 4044, the charge control circuit 4041 controls the charging power to the storage battery 40 so that the voltage becomes the target voltage. On the other hand, when the voltage of the DC bus 405 is lower than the target voltage output from the third control circuit 4044, the discharge control circuit 4042 controls the discharging power so as to increase the discharging power of the storage battery 40. Note that switching between the output of the charge control circuit 4041 and the output of the discharge control circuit 4042 is performed by the first switching circuit 4043. The third control circuit 4044 outputs a switching control signal to the first switching circuit 4043 based on the voltage value of the DC bus 405 measured by the voltmeter 406.

[0154] Next, the operation of the second control circuit 409 will be described with reference to Figures 7 to 13, Figure 29, and Figure 30. Figure 29 is a flowchart mainly showing the operation of the second control circuit 409. In Figure 29, when the operation of the storage battery power conversion device 41 starts, in step S201 the second control circuit 409 initializes various control parameters to predetermined initial values.

[0155] After the initialization of the various control parameters is completed, in the next step S202, the fourth control circuit 4097 collects the voltages measured by the voltmeters 401, 406, and 410, the currents measured by the ammeters 402, 407, and 411, and status information (e.g., SOC) of the storage battery 40. Note that since the measurement result of the voltmeter 410 is an AC voltage, the fourth control circuit 4097 calculates its effective voltage and sets it as the measured voltage. Similarly, since the measurement result of the ammeter 411 is an AC current, the fourth control circuit 4097 calculates its effective current and sets it as the measured current. Furthermore, in the first embodiment, a charge / discharge power calculation circuit (not shown) in the third control circuit 4044 of FIG. 6 calculates the charge / discharge power and the charge / discharge power amount of the storage battery 40 based on the collected data.

[0156] In step S203 of FIG. 29 , the AC voltage waveform of the power distribution system 24 measured by the voltmeter 410 is input to the AC frequency detection circuit 4091 shown in FIGS. 7 and 8 , which detects the zero-crossing points of the AC voltage. Specifically, with reference to the block diagram of the AC frequency detection circuit 4091 in FIG. 8 , the measurement result of the voltmeter 410 is input to the phase detection circuit 40910, which detects the zero-crossing points. In the first embodiment, the phase detection circuit 40910 detects the points and times at which the AC voltage waveform measured by the voltmeter 410 switches from negative to positive as zero-crossing point information. The zero-crossing point information detected by the phase detection circuit 40910 is also input to the frequency detection circuit 40911. The frequency detection circuit 40911 calculates the period of the AC voltage from the time information of the zero-crossing points detected last time and the time information of the zero-crossing points detected this time by the phase detection circuit 40910, and calculates the AC system frequency based on the calculation result. The first sine wave generating circuit 40912 outputs, as sine wave information, zero crossing point information detected by the phase detection circuit 40910 and frequency information of the AC voltage detected by the frequency detection circuit 40911. The zero crossing point detection information and frequency detection information are output to the inverter current control circuit 4094, the inverter voltage control circuit 4095, the virtual synchronous generator control circuit 4093, and the fourth control circuit 4097.

[0157] 29 , if the fourth control circuit 4097 detects a zero-crossing point in step S203, it sets a zero-crossing point detection flag in the next step S204. If the setting of the detection flag in step S204 is completed or if a zero-crossing point is not detected (NO in step S203), the third control circuit 4044 controls the first DC / DC conversion circuit 403 in the next step S205. In the first embodiment, as described above, the third control circuit 4044 controls the charging and discharging of the storage battery 40 so that the voltage of the DC bus 405 becomes a predetermined value. After step S205 is completed, the fourth control circuit 4097 controls the first DC / AC conversion circuit 408 in the next step S206.

[0158] FIG. 30 is a flowchart showing the control procedure for the first DC / AC conversion circuit 408. Referring to FIGS. 7 and 30 , when control of the first DC / AC conversion circuit 408 is started, in step S2061 of FIG. 30 , the effective power calculation circuit 4092 calculates a power value based on measurement information from the voltmeter 410 and the ammeter 411. In the next step S2062, the effective power calculation circuit 4092 integrates the measured power value using an integrator. Then, if the zero-crossing point detection flag is set (YES in step S2063), the effective power calculation circuit 4092 calculates an effective power value for one cycle of the AC voltage. The effective power calculation circuit 4092 stores the calculated effective power value in a memory circuit (not shown) in the fourth control circuit 4097 (step S2064) and initializes the integrator to zero (step S2065). After the initialization of the integrator in step S2065 above is completed, or if the zero-cross point detection flag has not been set (NO in step S2063), the inverter voltage control circuit 4095 generates a command value for the first DC / AC conversion circuit 408 in the next step S2066.

[0159] 7, 10, and 30, the control of the first DC / AC conversion circuit 408 will be described. As described above, the battery power conversion device 41 implements virtual synchronous generator control, and therefore the first DC / AC conversion circuit 408 is controlled as a voltage source (i.e., voltage control). Therefore, when the power supplied to the power distribution system 24 is insufficient, the output power is increased, and when the supplied power is excessive, the output power is decreased.

[0160] The operation of the inverter voltage control circuit 4095 will be described below with reference to Fig. 10. The inverter voltage control circuit 4095 outputs a control command value for controlling the first DC / AC conversion circuit 408, based on the frequency and phase information output from the virtual synchronous generator control circuit 4093 and the amplitude information of the AC system voltage output from the fourth control circuit 4097 (input via the first sine wave generation circuit 40912 in the first embodiment). The sine wave information (i.e., frequency, phase, and amplitude information) from the AC frequency detection circuit 4091 and the frequency and phase information calculated by the virtual synchronous generator control circuit 4093 are input to the second sine wave generation circuit 40951.

[0161] The second sine wave generating circuit 40951 generates a target value of the AC system voltage to be output from the first DC / AC conversion circuit 408 based on the input information, i.e., the frequency and phase information calculated by the virtual synchronous generator control circuit 4093 and the amplitude information output from the fourth control circuit 407. The subtractor 40952 subtracts the voltage measured by the voltmeter 410 from the AC voltage target value output from the second sine wave generating circuit 40951, and inputs the subtraction result to the third PI control circuit 40953. The third PI control circuit 40953 generates a voltage command by PI control so that the input subtraction result becomes zero, and outputs the generated voltage command to the first current limiting circuit 40955.

[0162] The first current limiting circuit 40955 limits the command value output from the third PI control circuit 40953 based on the measurement result of the ammeter 411 input via the fourth control circuit 4097. Specifically, in the first embodiment, when a current exceeding the current capacity of the first DC / AC conversion circuit 408 flows, the first current limiting circuit 40955 applies current limiting and controls the current flowing through the first DC / AC conversion circuit 408 to a predetermined current value (i.e., the current capacity of the first DC / AC conversion circuit 408). The first current limiting circuit 40955 monitors the current flowing through the first DC / AC conversion circuit 408 and controls (specifically, limits) the current value so that the current does not exceed the current capacity of the first DC / AC conversion circuit 408. The output of the first current limiting circuit 40955 is input to the second PWM conversion circuit 40954. The control parameters (i.e., control gain and integral time) of the third PI control circuit 40953 and the first current limiting circuit 40955 are output from the fourth control circuit 4097.

[0163] The second PWM conversion circuit 40954 performs PWM modulation on the voltage command value output from the first current limiting circuit 40955, and outputs the PWM-modulated voltage command value to the second switching circuit 4096. The second switching circuit 4096 in FIG. 7 selects one of the control command value of the inverter current control circuit 4094 and the control command value of the inverter voltage control circuit 4095 based on the control signal (i.e., the switching signal) output from the fourth control circuit, and outputs the selected control command value to the first DC / AC conversion circuit 408.

[0164] Although not used in the first embodiment, the operation of the inverter current control circuit 4094 will also be described with reference to FIG. 9 . The inverter current control circuit 4094 generates a control command value for controlling the first DC / AC conversion circuit 408 based on the DC voltage of the DC bus 205 output from the voltmeter 406. Specifically, a subtractor 40941 subtracts the DC voltage of the DC bus 405 output from the voltmeter 406 from the target value of the DC bus voltage output from the fourth control circuit 4097, and inputs the subtraction result to a first PI control circuit 40942. The first PI control circuit 40942 generates a command value by PI control so that the subtraction result becomes zero, and outputs the generated command value to the multiplier 4094. The control parameters (proportional gain and integral time) of the first PI control circuit 40942 are output from the fourth control circuit 4097.

[0165] Next, the multiplier 40943 multiplies the command value output from the first PI control circuit 40942 by a sine wave synchronized with the AC voltage waveform output from the first sine wave generation circuit 40912 in the AC frequency detection circuit 4091. This generates a current command value. The subtractor 40944 subtracts the current value of the AC system measured by the ammeter 411 from the current command value output from the multiplier 40943 and inputs the subtraction result to the second PI control circuit 40945. The second PI control circuit 40945 generates a control command value so that the subtraction result input from the subtractor 40944 becomes zero, and outputs the generated control command value to the first PWM conversion circuit 40946. The control parameters (proportional gain and integral time) of the second PI control circuit are input from the fourth control circuit 4097. The first PWM conversion circuit 40946 performs PWM modulation on the control command value input from the second PI control circuit 40945 and outputs the PWM-modulated control command value to the first DC / AC conversion circuit 408 .

[0166] 29 , when the control of the first DC / AC conversion circuit 408 in step S206 (more specifically, the generation of a command value for the first DC / AC conversion circuit 408 in step S2066 in FIG. 30 ) is completed, the fourth control circuit 4097 checks in the next step S207 whether or not a transmission request for measurement information has been received from the CEMS 31. If a transmission request for measurement information has been received from the CEMS 31 (YES in step S207), in the next step S208 the fourth control circuit 4097 notifies the CEMS 31 of various measurement results stored in a memory (not shown) via the communication interface circuit 412.

[0167] If a measurement information transmission request has not been received from the CEMS 31 (NO in step S207) or if notification of various measurement results has been completed in step S208, the fourth control circuit 4097 checks in the next step S209 whether control information has been received from the CEMS 31. If the fourth control circuit 4097 has received control information from the CEMS 31 (YES in step S209), the fourth control circuit 4097 sets a reception flag in the next step S210. If the fourth control circuit 4097 has not received control information from the CEMS 31 (NO in step S209) or has completed setting the reception flag in step S210, the fourth control circuit 4097 checks in the next step S211 whether a zero-cross point detection flag has been set. If the zero-cross point detection flag has not been set (NO in step S211), the fourth control circuit 4097 returns the process to step S202 and performs step S202 and subsequent steps again.

[0168] On the other hand, if the zero-crossing point detection flag is set (YES in step S211), the fourth control circuit 4097 acquires the representative value of the frequency of the AC system voltage and the detection results of the phase output from the AC frequency detection circuit 4091 in the next step S212. After acquiring the detection results of the AC frequency and phase in step S212, the fourth control circuit 4097 controls the virtual synchronous generator in the next step S213. In the first embodiment, one period of the AC system voltage is set as the control period. It goes without saying that the control period may be an integer multiple of the period of the AC system voltage or a predetermined period such as a one-second period.

[0169] The control of the virtual synchronous generator in step S213 of FIG. 29 will be described below with reference to the block diagram of the second control circuit 409 shown in FIG. 7 , the block diagram of the virtual synchronous generator control circuit 4093 shown in FIG. 11 , the block diagram of the governor control circuit 40933 shown in FIG. 12 , and the block diagram of the mass system calculation circuit 40937 shown in FIG. 13 . First, when the fourth control circuit 4097 shown in FIG. 7 determines that the control period has elapsed and it is time to execute control of the virtual synchronous generator, it instructs the virtual synchronous generator control circuit 4093 to generate frequency and phase information to be used in voltage control. In this first embodiment, the second sine wave generation circuit 40951 in the inverter voltage control circuit 4095 updates the target values ​​of the frequency and phase of the AC voltage at each zero-crossing point. Therefore, in this first embodiment, the control period is the period of the zero-crossing points detected by the AC frequency detection circuit 4091.

[0170] [Correction based on Rule 91 13.03.2025] Referring to Figure 11, a subtractor 40932 subtracts the frequency (Fref): for example 60 Hz) of the reference AC voltage output from the fourth control circuit 4097 from the representative value of the frequency of the actually measured AC system voltage output from the frequency detection circuit 40911, and inputs the subtraction result to a governor control circuit 40933.

[0171] 12, a multiplier 409331 in a governor control circuit 40933 multiplies the output of the subtractor 40932 in FIG. 11 by a control parameter (-1 / Kgd) notified from a fourth control circuit 4097, and inputs the multiplication result to a first-order lag model 409332. The speed adjustment rate Kgd and governor time constant Tg used in the governor control circuit 40933 are notified from the CEMS 31 and set in a register (not shown) via the fourth control circuit 4097, and then used.

[0172] The first-order lag model 409332 performs a calculation to simulate a first-order lag system (1 / (1+s×Tg)) using the time constant Tg notified by the fourth control circuit 4097 as described above, and inputs the calculation result to the limiter circuit 409333. The limiter circuit 409333 imposes a limit on the data input from the first-order lag model 409332. Specifically, the limiter circuit 409333 imposes a limit on the output of the governor control circuit 40933 so as not to exceed the power capacity of the first DC / AC conversion circuit 408.

[0173] 11 , the adder 40935 adds the output of the governor control circuit 40933 and the power command value (Pref) output from the fourth control circuit 4097, and outputs the addition result to the subtractor 40936. As described above, the power command value is notified from the CEMS 31 and output from the fourth control circuit 4097. The subtractor 40936 subtracts the measured effective power output from the effective power calculation circuit 4092 from the output of the adder 40935, and inputs the subtraction result to the mass system calculation circuit 40937.

[0174] [Correction based on Rule 91, 13.03.2025] The operation of the mass system calculation circuit 40937 will now be described with reference to Figure 13. The subtractor 409371 of the mass system calculation circuit 40937 subtracts the output of the multiplier 409373 from the output of the subtractor 40936 in Figure 11 and inputs the subtraction result to the integrator 409372. The integrator 409372 divides the subtraction result output from the subtractor 409371 by the inertia constant M output from the fourth control circuit 4097 and integrates the division result. The integration result of the integrator 409372 represents the difference value Δω from the angular velocity of the AC system frequency (2 × π × 60 Hz). The integrator 409372 inputs the integration result to the multiplier 409373 and the divider 409374. The multiplier 409373 multiplies the output Δω of the integrator 409372 by the damping coefficient Dg output from the fourth control circuit 4097 and outputs the multiplication result to the subtractor 409371. The divider 409374 divides the output Δω of the integrator 409372 by 2×π to convert Δω into a difference value Δf from the AC system frequency (60 Hz). The adder 409375 adds the output Δf of the divider 409374 to Fref, which is a frequency command value for the AC system voltage. This generates a frequency for voltage control by the inverter voltage control circuit 4095. The inertia constant M and damping coefficient Dg used in the mass system calculation circuit 40937 are generated and notified by the CEMS 31 as described above, and are then set in a register (not shown) via the fourth control circuit 4097.

[0175] Furthermore, the frequency information output from the adder 409375 is input to the phase calculation circuit 409376. The operation of the phase calculation circuit 409376 will be described below. In the first embodiment, the frequency information output from the adder 409375 is integrated by the phase calculation circuit 409376 and output as phase information of the frequency of the distribution system voltage when the inverter voltage control circuit 4095 performs voltage control. The phase information and frequency information output from the mass system calculation circuit 40937 are input to the second sine wave generation circuit 40951 in the inverter voltage control circuit 4095 in FIG. 10 via the first sine wave generation circuit 40912 in the AC frequency detection circuit 4091 in FIG. 8. The second sine wave generation circuit 40951 generates a target value of the AC system voltage to be output from the battery power conversion device 41 based on the input sine wave information.

[0176] Returning to FIG. 29 , when the control process for the virtual synchronous generator is completed in step S213, the fourth control circuit 4097 resets the zero-crossing point detection flag in the next step S214, and then checks whether the reception flag is set in the next step S215. If the reception flag is not set (NO in step S215), the fourth control circuit 4097 returns to step S202 and executes step S202 and subsequent steps again. On the other hand, if the reception flag is set (YES in step S215), the fourth control circuit 4097 sets the frequency command value (Fref) and power command value (Pref) notified from the CEMS 31 in a register (not shown) within the fourth control circuit 4097 in the next step S216, and then resets the reception flag in the next step S217. Thereafter, the fourth control circuit 4097 returns to step S202 and executes the subsequent steps again.

[0177] [Effects of First Embodiment] As described above, the distributed power management device and distributed power management system of the first embodiment are configured to generate the frequency command value (Fref) based on the drooping characteristics of the static inverter in the storage battery power conversion device 41, the created power command value, and the actually measured frequency of the AC grid voltage (Fmeasure) when creating an operation plan (i.e., the power command value (Pref) and the frequency command value (Fref)) for the storage battery power conversion device 41. Therefore, even if the frequency of the AC grid voltage changes due to a sudden change in the power consumption of the load or a sudden change in the power generated by an energy generating device such as a renewable energy source supplied to the grid due to a sudden change in solar radiation, the frequency of the AC grid voltage does not deviate from the frequency range managed by the static inverter that implements the virtual generator control characteristic (drooping characteristics), etc. As a result, there is an effect that the static inverter can continue to operate without shutting down the distributed power source.

[0178] In the first embodiment, a case has been described in which a power conversion device having a static inverter that implements a droop characteristic represented by virtual synchronous generator control is connected to an AC system, but the present disclosure is not limited to this case. Since the frequency command value (Fref) is generated based on the actual measurement result (Fmaesure) of the frequency of the AC system voltage, the power command value (Pref), and the droop characteristic (i.e., droop characteristic) of the static inverter, even if the frequency of the utility grid deviates from the rated frequency (e.g., 60 Hz), it is possible to control the power conversion device having a static inverter that implements the droop characteristic without deviating from its frequency management range.

[0179] In the first embodiment, a case where a power conversion device having a droop characteristic is connected to an interconnected system (i.e., a case where power is supplied from a utility grid) has been described, but the present disclosure is not limited to this case. Even in an isolated system, if a configuration is made to generate a frequency command value (Fref) based on the droop characteristic of a static inverter, the created power command value, and the actual frequency (Fmeasure) of the measured AC system voltage, it is possible to achieve the effect of controlling the frequency without deviating from the frequency management range of a power conversion device having a static inverter equipped with a droop characteristic, even if the frequency of the isolated system deviates from the rated frequency (e.g., 60 Hz), as in the case of an interconnected system.

[0180] In the first embodiment, a case has been described in which the load power consumption increases and the frequency of the distribution grid voltage decreases when the storage battery power conversion device 41 is in a discharging operation as shown in Figures 18, 24, and 26. However, the present disclosure is not limited to this case. For example, when the load power consumption decreases during a discharging operation and the frequency of the distribution grid voltage increases, or when a load fluctuation occurs during a charging operation and the frequency of the distribution grid voltage increases or decreases, the same effect can be achieved by controlling the frequency command value (Fref) based on the actual measurement result (Fmeasure) of the frequency of the distribution grid voltage.

[0181] Second Embodiment In the first embodiment, a case where the frequency command value (Fref) is controlled based on the actual measurement result (Fmeasure) of the frequency of the AC system voltage is described, but in the second embodiment, a case where the power command value (Pref) is controlled (corrected) based on the actual measurement result (Fmeasure) of the frequency of the AC system voltage is described. Hereinafter, the second embodiment will be described, focusing on the operation of the parts that differ from the first embodiment.

[0182] [Configuration of CEMS of Second Embodiment] Figure 31 is a block diagram of a CEMS 31 according to the second embodiment. As shown in Figure 31, the CEMS 31 according to the second embodiment includes a communication circuit 311, a memory circuit 312, an AC frequency collection circuit 313, an operation plan creation circuit 314, a power command value correction circuit 320, a distributed power source drooping characteristic management circuit 316, a transmission data generation circuit 317, and a second CEMS control circuit 321. That is, the CEMS 31 according to the second embodiment differs from the CEMS 31 according to the first embodiment shown in Figure 2 in that the power command value correction circuit 320 is provided instead of the frequency command value generation circuit 315, and the second CEMS control circuit 321 is provided instead of the CEMS control circuit 318. The following mainly describes the above configuration that differs from the first embodiment.

[0183] [Overview of Operation of Distributed Power Management Apparatus] Figures 32A and 32B are diagrams for explaining a method of generating a power command value in CEMS 31 according to Embodiment 2. Figure 32A shows the drooping characteristic of the power command value (Pref) before correction, and Figure 32B shows the drooping characteristic of the power command value (Pref) after correction. Below, the operating principle of CEMS 31 according to Embodiment 2 will be explained with reference to Figures 32A and 32B.

[0184] In the second embodiment, the CEMS 31 generates the power command value (Pref) for each storage battery power conversion device 41 in two stages. Specifically, when the CEMS 31 starts generating the power command value (Pref), the operation plan creation circuit 314 shown in Fig. 31 creates a demand plan based on the predicted power generation results of the mega solar power plant 26 and the predicted power consumption results of consumers, as in the first embodiment. Then, the CEMS 31 creates the power command value (Pref) before correction for each storage battery power conversion device 41, i.e., operation plan power command value information, based on the created demand plan.

[0185] After completing the creation of the pre-correction power command value (Pref), the CEMS 31 creates a drooping characteristic by assuming that the frequency command value Fref is equal to the rated frequency (e.g., 60 Hz) of the utility grid (see FIG. 32A ). The CEMS 31 then compares the frequency command value Fref with the actual measurement result (Fmeasure) of the AC grid voltage collected by the AC frequency collection circuit 313. If the actual measurement result (Fmeasure) of the frequency of the AC grid voltage is below Fmin, for example, as in the first embodiment, the current drooping characteristic may cause the battery power conversion device 41 to stop in the event of a load fluctuation or a sudden change in power generation, as described above. In such a case, the CEMS 31 of the second embodiment generates a power command value (Pref′) to be output to the battery power conversion device 41 so that the power of the pre-correction power command value (Pref) described above is output based on the actual measurement value (Fmeasure) of the AC grid voltage frequency, as shown in FIG. 32B (details will be described later). In the example of FIG. 32B , the drooping characteristic before the correction of the power command value (solid line in the figure) is changed to a drooping characteristic that is shifted in parallel to the left (dashed line in the figure). In the first embodiment, a similar change in the drooping characteristic is implemented by outputting the measured system frequency (Fmeasure) as the frequency command value (Fref) to the battery power conversion device 41. In the second embodiment, the drooping characteristic is changed by correcting the power command value (Pref). Specifically, in the example shown in FIG. 32B , the power command value (Pref) created by the operation plan creation circuit 314 is reduced, thereby shifting the drooping characteristic in parallel to the left. As a result, as shown in Figure 32B, even if the actual measured value (Fmeasure) of the frequency of the distribution system voltage is outside the frequency range covered by the original drooping characteristic of the storage battery power conversion device 41, CEMS 31 sends a corrected power command value (Pref') to each storage battery power conversion device 41, and the drooping characteristic shifts to the left as shown in Figure 32B, allowing the storage battery power conversion device 41 to continue operating.

[0186] Next, the effect of the above-described method for generating a power command value will be described with reference to FIGS. 33A and 33B . FIG. 33A is a diagram illustrating the frequency range of the inverter when the drooping characteristic of the comparative example is used. In FIG. 33A , the horizontal axis represents time, and the vertical axis represents the frequency of the AC system voltage. This diagram illustrates a case in which the load decreases over time, causing the frequency of the AC system voltage to increase in a ramp-like manner. As shown in the diagram, when the frequency command value (Fref) is constant at the rated frequency (60 Hz) and the power command value (Pref) uses a constant value generated by the operation plan generation circuit 314, the area inside the thick dashed line is the frequency range (also referred to as the frequency management range) of the battery power conversion device 41 (inverter). As shown in the diagram, as the frequency of the system voltage gradually increases, the frequency of the system voltage deviates from the inverter frequency range that the battery power conversion device 41 (inverter) can control (the NG region in the diagram), causing virtual synchronous generator control (VSG control) to fail, and causing the battery power conversion device 41 to stop.

[0187] On the other hand, FIG. 33B is a diagram showing the power command value and the inverter frequency when the drooping characteristic of the second embodiment is used. As shown in the figure, a power command value (Pref') obtained by correcting the power command value (Pref) based on the actual measurement result of the frequency of the AC system voltage is output to the power conversion device for the storage battery 41. Specifically, in the second embodiment, the frequency of the AC system voltage is measured at one-minute intervals, as in the first embodiment. Then, the power command value (Pref') is controlled based on the measurement result of the frequency of the AC system voltage. In FIG. 33B, the horizontal axis represents time, and the vertical axis represents the power command value (Pref') and the frequency of the distribution system voltage notified to the power conversion device for the storage battery 41. As shown in the figure, because the power command value (Pref') is appropriately controlled based on the frequency of the AC system voltage, the frequency range (also referred to as the frequency management range) that can be controlled by the power conversion device for the storage battery 41 (inverter) based on the virtual synchronous generator control (drooping characteristic) can be appropriately controlled even when the frequency of the system voltage gradually increases. As a result, the frequency of the distribution system voltage does not deviate from the frequency management range of the power conversion device 41 (inverter) for the storage battery, and the interconnected operation can be continued.

[0188] As described above, when a power conversion device having a static inverter implementing a droop characteristic represented by virtual synchronous generator control is connected to an AC system, the distributed power management device is configured to generate a power command value (Pref) based on the actual measurement results of the frequency of the AC system voltage, the power command value (Pref) created by the operation plan creation circuit 314, and the droop characteristic. This has the effect of enabling the power conversion device to be controlled without deviating from the frequency management range of the power conversion device having a static inverter implementing a droop characteristic, even if the frequency of the main system deviates from the rated frequency (for example, 60 Hz).

[0189] [Details of Operation of Distributed Energy Management System (CEMS)] Next, the operation of the distributed energy management system (CEMS 31) of the second embodiment will be described in detail with reference to FIGS. 31 to 38. In the following explanation, only the operation of parts that differ from the first embodiment will be described. The power distribution system to which the CEMS 31 is connected is the same as that in the first embodiment, and therefore the explanation will not be repeated. In addition, the configuration and operation of the storage battery power conversion device 41 managed by the CEMS 31 are also the same as those in the first embodiment, and therefore the explanation will not be repeated. Note that in the second embodiment, the CEMS 31 notifies the storage battery power conversion device 41 of the corrected power command value (Pref′) and frequency command value (specifically, the reference value of the frequency of the distribution system voltage (i.e., the rated frequency), for example, 60 Hz).

[0190] As in the first embodiment, the power supplied from the substation 20, the power generated by the mega solar 26 (where the mega solar power conversion device 27 operates as a current source), and the discharge power output from the storage batteries 40a to 40c are supplied to the loads of the power distribution system 1. Here, the sequence during normal operation of the distributed power management system centered on the CEMS 31 is made up of processing at 30-minute intervals and processing at 1-minute intervals as shown in Fig. 20, as in the first embodiment. The processing content of the distributed power management device is also basically the same, with only the method of generating the power command value and the frequency command value being different.

[0191] The detailed operation of CEMS 31 will be described below with reference to the block diagram of CEMS 31 in Fig. 31 and Fig. 21 and Fig. 34 to Fig. 39. When processing in CEMS 31 is started, second CEMS control circuit 321 executes processing basically in accordance with the flow shown in Fig. 21. Note that the flowchart shown in Fig. 21 is basically the same as that of embodiment 1, so steps common to embodiment 1 will only be briefly described and detailed description will not be repeated.

[0192] 21 , when processing starts, the CEMS 31 checks in step S101 whether or not a transmission request for measurement data has been received from the DSO 21. If the CEMS 31 receives a transmission request (YES in step S101), the CEMS 31 collects the latest measurement information from the storage battery power conversion device 41, the voltmeter 22, and each consumer (including the mega solar power conversion device 27) in the next step S102. Then, using 30 sets of measurement data collected at one-minute intervals, the CEMS 31 calculates the amount of power consumed by each consumer, the amount of power generated by the mega solar power plant 26, and the amount of power charged and discharged by the storage battery 40 over a 30-minute period. The CEMS 31 transmits the calculated amounts of power, along with information such as the SOC of the storage battery 40, to the DSO 21 via the communication circuit 311 (S103). When the data transmission in step S103 above is completed or when there is no request to transmit measurement data from the DSO 21 (NO in S101), the CEMS 31 checks in the next step S104 whether or not it has received a demand plan notification from the DSO 21. If the CEMS 31 has received a demand plan notification (YES in step S104), it creates an operation plan in the next step S105. Note that in the second embodiment, as in the first embodiment, the DSO 21 notifies the CEMS 31 of a 24-hour supply and demand plan for power supplied from the main grid to the distribution grid 24 at 30-minute intervals.

[0193] FIG. 34 is a flowchart showing detailed operations of the operation plan creation process in step S105 of FIG. 21 in the second embodiment. In FIG. 34 , when creation of an operation plan is started, the CEMS 31 first predicts the amount of power generated by the mega solar power plant 26 in step S1051. Specifically, referring again to FIGS. 31 and 3 , when the second CEMS control circuit 321 receives a notification of a demand plan (specifically, a storage battery operation plan) from the DSO 21, it instructs the management circuit 3146 in the operation plan creation circuit 314 to create an operation plan. Upon receiving this instruction, the management circuit 3146 instructs the power generation amount prediction circuit 3142 via the storage battery operation plan generation circuit 3141 to predict the power generation power of the mega solar power plant 26. Upon receiving this instruction, the power generation amount prediction circuit 3142 obtains a 24-hour weather forecast from a weather forecast server located on the Internet (not shown). The power generation amount prediction circuit 3142 predicts the amount of power generation for 24 hours using the weather forecast and data in a power generation amount prediction database (not shown) managed by the power generation amount prediction circuit 3142. Note that an example of the database has been described in relation to the flowchart of Fig. 22, and therefore the description will not be repeated here.

[0194] After the power generation prediction in step S1051 in Fig. 34 described above is completed, the CEMS 31 predicts the power consumption of the consumer in the next step S1052. Specifically, referring back to Fig. 3, when the management circuit 3146 in the operation plan creation circuit 314 receives the power generation prediction result of the mega solar power plant 26 from the power generation prediction circuit 3142, it instructs the power consumption prediction circuit 3143 to predict the power consumption of the consumer via the battery operation plan generation circuit 3141. Upon receiving the instruction, the power consumption prediction circuit 3143 predicts the power consumption of the consumer for 24 hours using data in a power consumption prediction database (not shown) managed by the power consumption prediction circuit 3143. Note that an example of the database has been described in relation to the flowchart of Fig. 22, and therefore the description will not be repeated here.

[0195] When the prediction of the power consumption of the consumers in step S1052 of Fig. 34 is completed, the CEMS 31 starts creating a demand plan in step S1053 of Fig. 34. Specifically, referring again to Fig. 3, when the storage battery operation plan generation circuit 3141 in the operation plan creation circuit 314 receives the prediction result of the power consumption of the consumers from the power consumption prediction circuit 3143, the storage battery operation plan generation circuit 3141 calculates the total value of the charging and discharging power of the storage batteries 40a to 40c every 30 minutes based on the power generation amount prediction result of the mega solar power plant 26 from the power generation amount prediction circuit 3142, the prediction result of the power consumption of the consumers from the power consumption prediction circuit 3143, and the demand plan notified by the DSO 21. Note that, as described above, in the case of the second embodiment, the demand plan notified by the DSO 21 is a 24-hour power supply plan (i.e., a power supply plan every 30 minutes) planned for the distribution system 1 on the load side of the substation 20.

[0196] 34 is completed, the CEMS 31 formulates the charge / discharge power of the storage batteries 40a to 40c in the next step S1054. Specifically, referring again to FIGS. 31 and 3, the operation plan creation circuit 314 determines (pro-rata) the charge / discharge power from each storage battery 40a to 40c every 30 minutes based on the SOC information of the storage batteries 40a to 40c collected in the memory circuit 312 via the communication circuit 311 and the storage battery capacities of the storage batteries 40a to 40c. In the second embodiment, as in the first embodiment, when planning the operation of the storage batteries for 24 hours, the operation plan is created so that the SOC of the storage batteries 40a to 40c is zero at almost the same time or so that the batteries are ready to be charged or discharged 24 hours later.

[0197] 34, when the charge / discharge power of the storage batteries 40a to 40c is determined, in the next step S1055, the AC frequency collection circuit 313 in the CEMS 31 acquires the frequency of the distribution system voltage. As described above, in the second embodiment, similar to the first embodiment, the voltmeters 22a to 22x measure the frequency at each point from the measured AC system voltage, and the AC frequency collection circuit 313 calculates and outputs the average value of the frequency as a representative value (Fmeasure).

[0198] When collection of the distribution system voltage frequency and calculation of the representative value (Fmeasure) are completed in step S1055 of FIG. 34 , the second CEMS control circuit 321 checks in the next step S1056 whether or not control parameters (i.e., power command values ​​and frequency command values ​​(Pref')) for all of the storage battery power conversion devices 41 have been generated. If the answer is NO in step S1056, the second CEMS control circuit 321 generates a power command value (Pref') in the next step S1060. Hereinafter, with reference to FIG. 35 , the flow of generating the power command value (Pref') in step S1060 will be described.

[0199] 35 is a flowchart showing the procedure for generating a power command value (Pref'). In Fig. 35, when generation of the power command value (Pref') is started, in a first step S10571, the power command value correction circuit 320 shown in Fig. 31 issues an instruction to the second control circuit 321 in the CEMS to acquire control parameters (i.e., drooping characteristics) of the virtual synchronous generator control circuit 4093 of the power conversion device 41 for the storage battery that generates the current power command value (Pref') (i.e., the power command value (Pref) is to be corrected).

[0200] Upon receiving the instruction from the power command value correction circuit 320, the second CEMS control circuit 321 acquires the drooping characteristic from the distributed power supply drooping characteristic management circuit 316. In the second embodiment, the second CEMS control circuit 321 acquires, as control parameters, the speed adjustment rate (Kgd) of the virtual synchronous generator control, the governor time constant (Tg), the inertia constant (M), the damping coefficient (Dg), and the capacity (inverter capacity) of the first DC / AC conversion circuit 408, as in the case of the first embodiment. It goes without saying that the drooping characteristic information is not limited to the above, and may be a data table indicating the relationship between ΔP (i.e., power command value (Pref)−actual measured value of active power (Pmeasure)) output from the first DC / AC conversion circuit 408 and ΔF (i.e., frequency command value (Fref)−actual measured value of the frequency of the AC system voltage (Fmeasure)) output from the first DC / AC conversion circuit 408, or data such as the slope of the drooping characteristic.

[0201] After completing step S10571, the power command value correction circuit 320 instructs the second CEMS control circuit 321 to generate upper and lower limit values ​​for the frequency of the AC system voltage, determined by the drooping characteristic, in step S10572. In this second embodiment, as in the first embodiment, a case will be described in which virtual synchronous generator control is used as the drooping characteristic. In virtual synchronous generator control, ΔF can be calculated using the above-described equation (5). Specifically, in this second embodiment, the upper limit value Fmax of the frequency and the lower limit value Fmin of the frequency can be calculated by substituting the speed adjustment rate Kgd, the damping coefficient Dg, and the minimum and maximum values ​​of ΔP into equation (5). In this second embodiment, the minimum value of ΔP is calculated by subtracting the maximum discharge power from the power command value (Pref). Meanwhile, the maximum value of ΔP is calculated by subtracting the power command value (Pref) from 0, assuming that the first DC / AC conversion circuit 408 is not charging.

[0202] When the generation of the upper and lower limit values ​​of the frequency of the AC system voltage in the drooping characteristic in step S10572 is completed, the power command value correction circuit 320 checks in the next step S10573 whether the actually measured frequency of the AC system voltage is within the frequency reference range (see FIG. 36 ) determined by the upper and lower limit frequencies of the drooping characteristic. The operation of S10573 will be described below with reference to FIG. 36 .

[0203] FIG. 36 is a diagram showing an example of the drooping characteristic of the storage battery power converter 41 in the distributed power management system of the second embodiment. In the diagram, the horizontal axis represents the frequency of the distribution system voltage, and the vertical axis represents the discharge power output from the storage battery power converter 41. Note that, in the second embodiment, as in the first embodiment, for simplicity of explanation, it is assumed that the storage battery power converter 41 does not perform charging. In the diagram, Fmax and Fmin represent the upper and lower limit frequencies of the drooping characteristic. Also, in the second embodiment, as in the first embodiment, the frequency reference range determined by the upper and lower limit frequencies is the range inside the upper limit frequency Fmax and the lower limit frequency Fmin by the frequency offset F_offset. It goes without saying that the frequency offset F_offset may have different values ​​on the upper and lower limit sides, or may be changed depending on the value of the power command value (Pref) generated by the operation plan creation circuit 314.

[0204] In FIG. 36 , if the representative value of the measured frequency (Fmeasure) output from the AC frequency collection circuit 313 deviates from the frequency reference range determined by the upper and lower limit frequencies (*1 in the figure), the power command value correction circuit 320 selects NO in step S10573, and if the measured frequency (Fmeasure) is within the frequency reference range determined by the upper and lower limit frequencies (*2 in the figure), the power command value correction circuit 320 selects YES in step S10573.

[0205] If the result of step S10573 is YES, then in the next step S10581, the power command value correction circuit 320 sets the power command value (Pref) notified as an operation plan from the operation plan creation circuit 314 as the power command value (Pref') to be output to the battery power conversion device 41 (step S10581), and ends the power command value (Pref') generation process. On the other hand, if the result of step S10573 is NO, then in the next step S10580, the power command value correction circuit 320 calculates the power command value (Pref'). The operation of step S10580 will be described below with reference to FIG. 37 .

[0206] FIG. 37 is a flowchart showing the procedure for generating a power command value (Pref') in step S10580 of FIG. 35. In the first step S105750 of FIG. 37, the power command value correction circuit 320 generates a drooping characteristic by assuming that Fref = Fmeasure, as in the first embodiment, and calculates upper and lower limit frequencies of the frequency of the AC system voltage based on the generated drooping characteristic. Specifically, the upper and lower limit frequencies can be calculated in the same manner as in step S10572 of FIG. 35. That is, the power command value correction circuit 320 calculates the upper limit value Fmax of the frequency and the lower limit value Fmin of the frequency by substituting the speed adjustment rate Kgd, the damping coefficient Dg, the minimum value of ΔP, and the maximum value of ΔP into equation (5) (see part B of FIG. 38).

[0207] Furthermore, in step S105750, power command value correction circuit 320 sets the power value at the current frequency command value Fref (for example, 60 Hz in FIG. 38) to a provisional power command value Pref'' based on the generated drooping characteristic.

[0208] After step S105750 is completed, in the next step S105751, the power command value correction circuit 320 checks whether the upper and lower limit frequencies of the drooping characteristic are within the upper and lower limit values ​​of the frequency of the AC system voltage. In the second embodiment, as in the first embodiment, the upper and lower limit values ​​of the frequency of the AC system voltage are set to 60.1 Hz to 59.9 Hz. Furthermore, the power command value correction circuit 320 checks whether the provisional power command value Pref" is within the range of the power capacity of the storage battery power conversion device 41, that is, whether the absolute value of the provisional power command value Pref" is equal to or less than the maximum discharge power and equal to or less than the maximum charge power.

[0209] If the answer is YES in step S105751, the power command value correction circuit 320 sets the provisional power command value (Pref") as the finally determined power command value (Pref') and ends the process. On the other hand, if the answer is NO in step S105751, the power command value correction circuit 320 corrects the provisional power command value (Pref") in the next step S105752 to finally determine the power command value (Pref'). The operation of step S105752 will now be described with reference to FIG. 38.

[0210] FIG. 38 is a diagram illustrating a procedure for correcting a power command value. As shown in part A of FIG. 38 , when the frequency command value (Fref) is 60 Hz, it is assumed that the representative value (Fmeasure) of the frequency of the measured AC system voltage is 59.915 Hz. In this case, as shown in part B of FIG. 38 , the power command value correction circuit 320 calculates a provisional power command value (Pref") for the frequency command value (Fref = 60 Hz) so that the output power of the storage battery power conversion device 41 when the frequency of the distribution system voltage is Fmeasure becomes the power command value (Pref) created by the operation plan creation circuit 314. However, in this example, as shown in part B of FIG. 38 , the lower limit frequency of the drooping characteristic (i.e., the frequency at the maximum discharge power) is lower than the lower limit value (59.9 Hz) of the frequency of the AC system voltage. In the case of FIG. 38 , the provisional power command value (Pref") is within the range of the power capacity of the storage battery power conversion device 41. Therefore, the power command value correction circuit 320 finally determines the power command value (Pref′) by correcting the provisional power command value (Pref″) at the frequency command value (Fref=60 Hz) so that the lower limit frequency of the drooping characteristic coincides with the lower limit value of the frequency of the AC system voltage, as shown in part C of FIG. 38 .

[0211] On the other hand, when the power command value (Pref") at the frequency command value (Fref = 60 Hz) is calculated so that the output power of the storage battery power conversion device 41 when the frequency of the distribution system voltage is Fmeasure becomes the power command value (Pref) created by the operation plan creation circuit 314, if the lower limit frequency Fmin and upper limit frequency Fmax of the drooping characteristic are within the rated frequency range of the AC system (59.9 Hz to 60.1 Hz), the power command value correction circuit 320 outputs the provisional power command value (Pref") to the storage battery power conversion device 41 as the final power command value (Pref').

[0212] The same applies to a case where the upper limit frequency of the drooping characteristic exceeds the upper limit frequency of the AC system voltage. In this case, the power command value correction circuit 320 generates a power command value (Pref′) at the frequency command value (Fref=60 Hz) so that the upper limit frequency of the drooping characteristic coincides with the upper limit frequency of the AC system voltage.

[0213] If the provisional power command value (Pref") for the frequency command value (Fref = 60 Hz) is outside the range of the power capacity of the battery power conversion device 41, a power command value (Pref') is generated so that it is within the range of the power capacity. A specific example of this case will be described later with reference to Figure 41A. When step S105752 in Figure 37 is completed, the second CEMS control circuit 321 terminates the calculation of the power command value (Pref') (S10580 in Figure 35).

[0214] Returning to FIG. 34, when step S1060 is completed, the second CEMS control circuit 321 returns the processing to step S1056, and thereafter repeats step S1060 until step S1056 is YES, that is, until calculation of the power command value (Pref') for all storage battery power conversion devices 41 is completed.

[0215] Returning to FIG. 21 , when the second CEMS internal control circuit 321 finishes generating the operation plan in step S105, in the next step S110, it notifies each storage battery power conversion device 41 of the generated operation plan (power command value Pref′ and frequency command value Fref (60 Hz)). In the next step S111, the second CEMS internal control circuit 321 determines whether to stop the CEMS 31. If step S111 is YES, the second CEMS internal control circuit 321 stops the CEMS 31. On the other hand, if step S111 is NO, the second CEMS internal control circuit 321 returns to step S101 and repeats the above-described flow.

[0216] Next, a case where step S104 in Fig. 21 is NO will be described. In this case, the second CEMS internal control circuit 321 checks in step S106 whether it is the start time of the one-minute periodic processing. If the answer is NO in step S106, the second CEMS internal control circuit 321 returns the process to step S101 and repeats the above-described flow. On the other hand, if the answer is YES in step S106, the second CEMS internal control circuit 321 proceeds to the next step S107.

[0217] In step S107, the second CEMS control circuit 321 collects measurement data from the voltmeter 22, the storage battery power conversion device 41, the mega solar power conversion device 27, and consumer measurement data. After completing collection of the measurement data in step S107, the second CEMS control circuit 321 determines whether or not the operation plan needs to be revised in the next step S108. In the second embodiment, as in the first embodiment, the control circuit 321 determines that a revision is necessary when the SoC notified from the storage battery power conversion device 41 is outside a predetermined range or when the output (Fmeasure) of the AC frequency collection circuit 313 is outside a predetermined range. Note that the operation for determining whether or not the operation plan needs to be revised in step S108 is the same as the flowchart shown in FIG. 27 in the first embodiment, and therefore detailed description thereof will not be repeated.

[0218] [Correction based on Rule 91 13.03.2025] If the second CEMS control circuit 321 determines in step S108 that the operation plan does not need to be modified (i.e., if the operation plan modification flags of all the battery power conversion devices 41 are "0") (NO in step S108), the second CEMS control circuit 321 returns the process to the initial step S101 and repeats the above-mentioned process. On the other hand, if the second CEMS control circuit 321 determines in step S108 that the operation plan needs to be modified (i.e., if at least one operation plan modification flag is "1") (YES in step S108), the second CEMS control circuit 321 modifies the operation plan in the next step S109. Details of step S109 will be described below with reference to FIG. 39 .

[0219] 39 is a flowchart showing the procedure for correcting an operation plan in the distributed power management device of embodiment 2. When the operation plan correction flow starts, the second CEMS control circuit 321 checks in step S1091 whether or not the operation plan correction flag has been set. As described above, in embodiment 2, as in embodiment 1, an operation plan correction flag is provided for each battery power conversion device 41, and a new power command value (Pref or Pref') is generated for an operation plan that requires correction.

[0220] If the operation plan correction flag has not been set (NO in step S1091), the process proceeds to step S1098. The process in step S1098 will be described later. On the other hand, if the operation plan correction flag has been set (YES in step S1091), the process proceeds to steps S1092 to S1094. The second CEMS control circuit 321 acquires data (charge / discharge power, SoC) measured by the storage battery power conversion device 41 in step S1092, acquires a frequency command value (Fref) and a power command value (Pref) in step S1093, and further acquires a representative value (Fmeasure) of the frequency of the actually measured AC voltage output from the AC frequency collection circuit 313 in step S1094.

[0221] After steps S1092 to S1094 are completed, the second CEMS control circuit 321 checks in the next step S1095 whether the SoC is within a predetermined range. In the second embodiment, as in the first embodiment, the case where the SoC is outside the predetermined range refers to a case where the SoC exceeds 0.9 during charging and a case where the SoC is below 0.05 during discharging. Here, the SoC is 1.0, which is a full charge. Needless to say, the case where the SoC is outside the predetermined range is not limited to this case, as in the first embodiment.

[0222] If the SoC of the storage battery is not within the predetermined range (NO in step S1095), the second CEMS control circuit 321 changes the power command value (Pref) in the next step S1096. In the second embodiment, a data table (not shown) that determines the power command value depending on the SoC value is stored in the CEMS 31, and the second CEMS control circuit 321 determines the power command value (Pref) based on that information. It goes without saying that, as explained in the first embodiment with reference to FIG. 28 , the method of determining the power command value is not limited to the method based on the data table.

[0223] If the SoC of the storage battery is within the predetermined range (YES in step S1095), or if generation of the power command value (Pref) is completed in step S1096, the process proceeds to step S1097. In step S1097, the second CEMS control circuit 321 checks whether the representative value of the measured frequency of the power distribution system voltage (Fmeasure) is within the frequency reference range. The frequency reference range is the same as that described in step S10573 of FIG. 35 and FIG. 36.

[0224] If the representative value of the measured frequency of the power distribution system voltage (Fmeasure) is not within the frequency reference range (NO in step S1097), the second control circuit 321 in the CEMS calculates a power command value (Pref') in the next step S10911. Step S10911 in Fig. 39 is the same as step S10580 in Fig. 35, and more specifically, is the same as the flowchart in Fig. 37, so description thereof will not be repeated.

[0225] [Correction Based on Rule 91 05.11.2024] If the operation plan correction flag is not set (NO in step S1091), or if the calculation of the power command value (Pref') is completed in step S10911, or if the measured representative value of the distribution system voltage frequency (Fmeasure) is within the frequency reference range (YES in step S1097), processing proceeds to step S1098. In step S1098, the second CEMS control circuit 321 checks whether it has generated the control parameters (Pref, Pref') for all battery power conversion devices 41 that require correction. If it has generated all the control parameters (YES in step S1098), the second CEMS control circuit 321 ends the operation plan correction flow. On the other hand, if the generation of control parameters for all battery power conversion devices 41 that require modification has not been completed (NO in step S1098), the second CEMS control circuit 321 changes the processing target to the next battery power conversion device 41 in step S1099, and then returns to the first step S1091 to execute the above-mentioned processing again.

[0226] Returning to FIG. 21 , when the correction of the operation plan in step S109 described above is completed, or when the creation of the operation plan in step S105 described above is completed, in the next step S110, the second CEMS internal control circuit 321 notifies each storage battery power conversion device 41 of the created operation plan (power command value (Pref or Pref′) and frequency command value (Fref: 60 Hz)). Then, in the next step S111, the second CEMS internal control circuit 321 determines whether or not to terminate the operation of the CEMS 31. If the operation of the CEMS 31 is to be terminated (YES in step S111), the CEMS 31 is stopped. On the other hand, if the operation of the CEMS 31 is not to be terminated (NO in step S111), the process returns to the initial step S101, and the above-mentioned process is executed again. Note that the operation of the storage battery power conversion device 41 is the same as in the case of embodiment 1, and therefore description thereof will not be repeated.

[0227] Effect of Second Embodiment As described above, the distributed power management device (CEMS31) of the second embodiment is configured to calculate the power command value (Pref') by modifying the power command value (Pref) created by the operation plan creation circuit 314 based on the drooping characteristics of the static inverter in the storage battery power conversion device 41, the power command value (Pref) created by the operation plan creation circuit 314, and the actually measured frequency (Fmeasure) of the AC grid voltage when creating an operation plan for the storage battery power conversion device 41. Therefore, even if the frequency of the AC grid voltage changes due to fluctuations or sudden changes in the power consumption of the load and fluctuations or sudden changes in the power generated by energy generating devices such as renewable energy that are supplied to the grid due to sudden changes in solar radiation, the effect is that the frequency does not deviate from the frequency range managed by the static inverter that implements the virtual generator control characteristics (i.e., drooping characteristics), and the like, and operation can be continued without stopping the distributed power source.

[0228] [Other Examples of Drooping Characteristics] In the first and second embodiments, the drooping characteristics of the virtual synchronous generators shown in FIGS. 15 and 17 are used as examples of drooping characteristics implemented in the storage battery power conversion device 41. However, the drooping characteristics are not limited to those of the virtual synchronous generators. Furthermore, in the first and second embodiments, for simplicity, the storage battery power conversion device 41 is described as performing only a discharging operation. However, the operation of the storage battery power conversion device 41 is not limited to discharging only, and may be charging only or both charging and discharging. Below, other examples of drooping characteristics applicable to the distributed power management device of the first embodiment will be described with reference to FIGS. 40A to 40G, and other examples of drooping characteristics applicable to the distributed power management device of the second embodiment will be described with reference to FIGS. 41A to 41D.

[0229] 40A is a diagram showing an example of a linear drooping characteristic when charging and discharging are performed by the storage battery power conversion device 41. As shown in FIG. 40A , in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to a representative value Fmeasure (for example, an average value) of the frequency of the measured grid voltage.

[0230] 40B is a diagram showing an example of a linear drooping characteristic having a dead zone when charging and discharging the storage battery power conversion device 41. As shown in FIG. 40B , in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to the representative value Fmeasure of the frequency of the measured grid voltage.

[0231] 40C is a diagram showing an example of a curved drooping characteristic when charging / discharging is performed by the storage battery power conversion device 41. As shown in FIG. 40C, in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to the representative value Fmeasure of the frequency of the measured grid voltage.

[0232] 40D is a diagram showing an example of a linear drooping characteristic having a dead zone when only discharging is performed by the storage battery power conversion device 41. As shown in FIG. 40D, in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to the representative value Fmeasure of the frequency of the measured grid voltage.

[0233] 40E is a diagram showing an example of a curved drooping characteristic when only discharging is performed by the storage battery power conversion device 41. As shown in FIG. 40E, in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to the representative value Fmeasure of the frequency of the measured grid voltage.

[0234] 40F is a diagram showing an example of a linear drooping characteristic having a dead zone when the storage battery power conversion device 41 only performs charging. As shown in FIG. 40F , in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to the representative value Fmeasure of the frequency of the measured grid voltage.

[0235] 40G is a diagram showing an example of a curved drooping characteristic when only charging is performed by the storage battery power conversion device 41. As shown in FIG. 40G, in the case of the first embodiment, the frequency command value Fref is changed from the initial value (60 Hz) to the representative value Fmeasure of the frequency of the measured grid voltage.

[0236] Fig. 41A is a diagram showing an example of a linear drooping characteristic when the storage battery power conversion device 41 performs charging and discharging. In the case of embodiment 2, as shown in Fig. 41A, a tentative power command value Pref" at the frequency command value Fref (60 Hz) is provisionally set so that the power command value Pref according to the operation plan can be obtained at the measured grid frequency Fmeasure. However, in this case, since the tentative power command value Pref" exceeds the DC / AC converter capacity, a power command value Pref' is finally set so as to coincide with the maximum charging power of the DC / AC converter.

[0237] FIG. 41B is a diagram showing an example of a linear drooping characteristic when storage battery power conversion device 41 performs only charging. In the case of embodiment 2, as shown in FIG. 41B , a tentative power command value Pref" at frequency command value Fref (60 Hz) is provisionally set so that a power command value Pref according to the operation plan can be obtained at the measured system frequency Fmeasure. However, in this case, the lower limit frequency of the drooping characteristic (i.e., the frequency at maximum discharge power) falls below the lower limit frequency of the AC system voltage (59.9 Hz). Therefore, a power command value Pref' at frequency command value Fref (60 Hz) is finally set so that the lower limit frequency of the drooping characteristic matches the lower limit frequency of the AC system voltage.

[0238] 41C is a diagram showing an example of a linear drooping characteristic having a dead zone when the storage battery power conversion device 41 only discharges. In the case of the second embodiment, as shown in FIG. 41C , the power command value Pref′ at the frequency command value Fref (60 Hz) is determined so that the power command value Pref according to the operation plan is obtained at the measured grid frequency Fmeasure.

[0239] 41D is a diagram showing an example of a linear drooping characteristic having a dead zone when the storage battery power conversion device 41 only performs charging. In the case of the second embodiment, as shown in FIG. 41D , the power command value Pref′ at the frequency command value Fref (60 Hz) is determined so that the power command value Pref according to the operation plan is obtained at the measured grid frequency Fmeasure.

[0240] [Modifications] Modifications of the first and second embodiments are described below. When multiple static inverters, each having a drooping characteristic, are controlled by a distributed power management device (i.e., CEMS 31 (host EMS)), the drooping characteristics (specifically, frequency command value Fref) may be generated so that the maximum and minimum frequencies of the drooping characteristics of the multiple static inverters are approximately equal. This control allows the frequency range to be controlled so that all static inverters equipped with drooping characteristics can operate in accordance with the frequency of the power distribution system voltage, even in the event of a load fluctuation or a sudden change in the power generation amount of an energy generating device. This prevents the frequency of the AC system voltage from deviating from the frequency range managed by the drooping characteristic, allowing the distributed power source to continue operating without shutting down. Note that, taking into account errors in voltage sensors and the like, the maximum and minimum frequencies of the drooping characteristics of multiple static inverters may be considered to be substantially equal if the deviation is within 5 to 10% of the frequency deviation (i.e., the difference between the maximum frequency and the frequency command value Fref, or the difference between the minimum frequency and the frequency command value Fref).

[0241] In the first and second embodiments, the virtual synchronous generator control is implemented in the battery power conversion device 41. However, the implementation of the virtual synchronous generator control is not limited to this. For example, the virtual synchronous generator control and the above-described drooping characteristic may be implemented in energy generating devices such as wind power generators, energy generating devices such as fuel cells, and power conversion devices that charge and discharge power in batteries installed in electric vehicles and fuel cell vehicles. Even in such cases, if the distributed power source management device (CEMS 31) controls the drooping characteristic of each distributed power source based on the actual measurement result (Fmeasure) of the frequency of the distribution system voltage, the frequency range of a static inverter that implements a drooping characteristic such as the virtual generator control characteristic can be controlled so that it can operate in accordance with the frequency of the distribution system voltage even if the frequency of the distribution system voltage deviates from the rated frequency (e.g., 60 Hz). Therefore, the frequency of the AC system voltage does not deviate from the frequency range managed by the drooping characteristic, and the distributed power source can continue to operate without being shut down.

[0242] It goes without saying that wind turbines have a similar effect because they use a propeller to turn a motor, which creates inertia on the generator side.

[0243] In the first and second embodiments, a case has been described in which a distribution system in which a static inverter (battery power conversion device 41) having a drooping characteristic is installed is connected to a utility grid. However, the present invention is not limited to this case, and it goes without saying that the same effect can be achieved in an isolated system. In this case, the isolated system may be equipped with an emergency generator (synchronous generator) in addition to a storage battery equipped with a static inverter, a wind power generator, a solar power generation system, a fuel cell, or other distributed power sources. In such an isolated system, if the drooping characteristic of the static inverter having a drooping characteristic is controlled based on the frequency (F measure) of the AC system voltage as shown in the first and second embodiments, the frequency range of the static inverter is controlled so that it can operate in accordance with the frequency of the distribution system voltage. Therefore, the frequency of the AC system voltage does not deviate from the frequency range managed by the drooping characteristic, and the distributed power source can continue to operate without shutting down.

[0244] In the first and second embodiments, the rated frequency range of the AC system is the rated frequency range of the bulk power system (e.g., 59.9 Hz to 60.1 Hz, see FIG. 17 ), but it is not limited to this frequency range. When connected to a bulk power system, the rated frequency range may be set to a range determined by the bulk power system transmission and distribution company (e.g., ±0.2 Hz). In the case of an isolated power system, the rated frequency range may be set to a frequency range determined by the operator of the isolated power system (e.g., ±0.15 Hz), a frequency range determined by the drooping characteristics of a synchronous generator whose drooping characteristics cannot be changed by the CEMS 31, or a frequency range that can be achieved by the drooping characteristics of the largest static inverter in the isolated power system. By setting such a frequency range, even in an isolated power system, a static inverter equipped with a drooping characteristic such as a virtual generator control characteristic can operate in accordance with the frequency of the distribution system voltage. Therefore, the frequency of the AC system voltage does not deviate from the frequency range controlled by the drooping characteristics, allowing the distributed power source to continue operating without shutting down. In particular, if a synchronous generator whose drooping characteristics cannot be changed from CEMS 31 is installed, it goes without saying that the frequency of the independent system can be effectively stabilized by controlling the drooping characteristics of other distributed power sources within the frequency range that the synchronous generator can achieve.

[0245] In the first and second embodiments, the target power distribution system has been described as a three-phase AC system, but this is not limiting. For example, the power distribution system may be a single-phase system (including a single-phase three-wire system), or may be a three- or more-phase power distribution system. Furthermore, even in a case where a power conversion device for a storage battery (three-phase AC) and a home storage battery system (single-phase AC) are mixed, it goes without saying that the same effect can be obtained by generating a power command value (Pref') or a frequency command value (Fref) for a static inverter having a drooping characteristic as in the first and second embodiments.

[0246] In the first and second embodiments, when determining the actual measurement results of the frequency of the power distribution system voltage, the frequency at each point is measured from the AC system voltage measured by the voltmeters 22a to 22x, and the AC frequency collection circuit 313 calculates the average value as a representative value to average the measurement error of the voltmeter 22. However, as mentioned above, this is not limited to this. It goes without saying that the measurement results at one representative point or the average value of the measurement results at each storage battery power conversion device 41 may also be used. Furthermore, while the noise components contained in the output of the averaging circuit 3131 are removed using a first-order IIR filter, it is not necessary to provide a special filter. It also goes without saying that the filter is not limited to a first-order IIR filter, but may be a higher-order IIR filter or an FIR filter.

[0247] In the first and second embodiments, the drooping characteristics used in the virtual synchronous generator control shown in FIGS. 15 and 17 or the drooping characteristics shown in FIGS. 40 and 41 are exemplified as examples of the drooping characteristics implemented in the battery power conversion device 41, but the present invention is not limited to these. Furthermore, the drooping characteristics are not limited to the characteristics of the virtual synchronous generator control. Furthermore, the method of defining the drooping characteristics is not particularly limited. For example, the drooping characteristics may be a data table showing the relationship between ΔP (i.e., power command value (Pref) - Pmeasure (actual measured value of active power)) output from the first DC / AC conversion circuit 408 and ΔF (i.e., frequency command value (Fref) - actual measured value of AC system voltage (Fmeasure)) output from the first DC / AC conversion circuit 408, or data such as the slope of the drooping characteristics. Needless to say, the drooping characteristics may be defined using coordinate information for the start point of the polygonal line, the end point of the polygonal line, and each vertex of the polygonal line in the case of a polygonal line characteristic such as that shown in FIG. 40B. Furthermore, in the first and second embodiments, the case where the CEMS 31 manages the drooping characteristics of each storage battery power conversion device 41 has been described, but the present invention is not limited to this, and it goes without saying that the same effect can be achieved by configuring the CEMS 31 to acquire the drooping characteristics that each storage battery power conversion device 41 has in advance and manage them within the distributed power source drooping characteristic management circuit 316. It goes without saying that the distributed power source drooping characteristic management circuit 316 may be configured to acquire and manage control parameters (i.e., drooping characteristics) from the virtual synchronous generator control circuit 4093 of the storage battery power conversion device 41.

[0248] In the first and second embodiments, as described with reference to FIGS. 24 and 36 , the frequency reference range used when determining whether to generate the frequency command value (Fref) or the power command value (Pref′) is set to a range that is inside the upper limit frequency Fmax and the lower limit frequency Fmin determined by the drooping characteristics by the frequency offset F_offset. However, as described above, this is not limited to this. For example, the upper limit frequency offset F_offset_up and the lower limit frequency offset F_offset_down may be different values, and these values ​​may be changed based on the value of the power command value (Pref) created by the operation plan creation circuit 314 or the value of the actual measurement result (Fmeasure) of the frequency of the power distribution system voltage. For example, the value of the frequency offset F_offset may be decreased as the power command value approaches the inverter capacity.

[0249] In the first and second embodiments, the governor control circuit 40933 for virtual synchronous generator control implemented in the battery power conversion device 41 uses a model based on a first-order lag system shown in FIG. 12 , but this is not limited thereto. For example, a second-order lag system model or other models recommended by the Institute of Electrical Engineers of Japan (IEEE) may be used. Furthermore, while the mass system calculation circuit 40937 uses a model based on the oscillation equation shown in FIG. 13 , this is not limited thereto. For example, it is also possible to model it using a first-order lag system, a second-order lag system, an LPF, or the like. Furthermore, in the first and second embodiments, for the sake of simplicity, no reference is made to VQ control, which is often performed in virtual synchronous generator control. However, it is also true that similar effects can be obtained when the method of the present disclosure is applied to a power conversion device in which VQ control is implemented as virtual synchronous generator control.

[0250] In the first and second embodiments, the communication cycle between the DSO 21 and the CEMS 31 is 30 minutes, but as mentioned above, this is not limited to this. It goes without saying that the communication cycle may be, for example, 15 minutes or 1 hour. Furthermore, the communication cycle with the voltmeter 22 and the battery power converter 41, etc., is not limited to 1 minute, as mentioned above. It goes without saying that the communication cycle may be, for example, 1 second, 10 seconds, 30 seconds, 2 minutes, etc.

[0251] In the first and second embodiments, when detecting the phase from the AC voltage waveform measured by voltmeter 410, zero-crossing points are detected from the AC voltage waveform, and the frequency is detected from the time interval between the detected zero-crossing points. However, it goes without saying that the method for detecting the AC voltage frequency is not limited to the method using the detection results of the zero-crossing points. For example, in the case of three-phase AC, it goes without saying that the frequency of the distribution system voltage may be calculated using a dq transformation or the like.

[0252] In the first and second embodiments, when the SoC is outside a predetermined range and the power command value needs to be changed, a data table (not shown) that determines the power command value according to the SoC value is stored in CEMS 31, and the power command value (Pref) is determined based on that information. However, as mentioned above, the method for determining the power command value is not limited to table data. For example, the power command value may be changed to a value that does not cause over-discharge or over-charge during the time until the next demand plan notification from DSO 21 is received, based on the SoC value and the current power command value.

[0253] In the first and second embodiments, the case where several power conversion devices used for large-capacity storage batteries such as the storage battery 40 for the power distribution system are connected to the power distribution system has been described, but it goes without saying that virtual synchronous generator control may be implemented in power conversion devices for home storage batteries and power conversion devices for electric vehicles, and control similar to that of the CEMS 31 may be performed. In this case, the number of power conversion devices connected to the power distribution system 24 may be on the order of several hundred. Furthermore, it goes without saying that the same effect can be achieved even if a large-capacity device (e.g., several hundred kW to several MW) such as the storage battery 40 for the power distribution system and a small-capacity device (several kW) such as a home storage battery are connected to the same power distribution system.

[0254] Although the first and second embodiments have been described with reference to the storage battery power conversion device 41, the present invention is not limited to this. Even when virtual synchronous generator control is implemented in a system that controls a static inverter as a voltage source, for example, a system that supplies power generated from a solar cell (not limited to a mega solar cell, but also a home solar cell), a wind power generator, or a fuel cell to a grid, the same effect can be obtained by configuring the control parameters of the virtual synchronous generator control unit to be generated in the same manner as in the first and second embodiments. Furthermore, it is also possible to use an on-board storage battery of an electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV), a fuel cell vehicle (FCV), or the like.

[0255] In the first and second embodiments, for ease of understanding, the control circuit of the battery power conversion device 41 is configured as shown in Figures 5 to 13, and the configuration of the CEMS 31 is configured as shown in Figures 2 to 4, with each functional block configured as hardware (H / W). However, this is not limiting. The same control functions can also be achieved by implementing the functions of at least some of the functional blocks as software (S / W) implemented on a CPU (Central Processing Unit). Alternatively, the same control functions can also be achieved by dividing the functions of at least some of the functional blocks into software and hardware.

[0256] [Summary of Effects of First and Second Embodiments] As described above, the distributed power management device of the present disclosure is configured to generate a frequency command value (Fref) or a power command value (Pref') of the drooping characteristic (i.e., drooping characteristic) based on an actual measurement result (Fmeasure) of the frequency of the AC system voltage when a power conversion device having a static inverter implementing a drooping characteristic (i.e., drooping characteristic) represented by virtual synchronous generator control is connected to an AC system. Therefore, even if the frequency of the main system deviates from the rated frequency (e.g., 60 Hz), it is possible to control the frequency without deviating from the frequency management range of the power conversion device having a static inverter implementing the drooping characteristic (drooping characteristic).

[0257] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0258] 20 Substation, 21 Distribution Automation System (DSO), 22 Voltmeter, 23 Automatic Voltage Regulator (SVR), 24 Distribution System, 25 Communication Line, 26 Mega Solar, 27 Power Converter for Mega Solar, 28 Switchgear, 30 Synchronous Generator, 31 CEMS, 40 Storage Battery, 41 Power Converter for Storage Battery, 100 Town, 101 Factory, 102 Building, 103 Apartment Building, 401, 406, 410 Voltmeter, 402, 407,411 ammeter, 311 communication circuit, 312 memory circuit, 313 AC frequency collection circuit, 314 operation plan creation circuit, 315 frequency command value generation circuit, 316 distributed power source drooping characteristic management circuit, 317 transmission data generation circuit, 318 control circuit within CEMS, 320 power command value correction circuit, 321 second control circuit within CEMS, 403 first DC / DC conversion circuit, 404 first control circuit, 405 DC bus, 408 first DC / AC conversion circuit, 409 second control circuit, 412 communication interface, 3131 averaging circuit, 3132 multiplier, 3133 adder, 3134 multiplier, 3135 register, 3141 battery operation plan creation circuit, 3142 power generation amount prediction circuit, 3143 power consumption prediction circuit, 3144 battery operation plan correction circuit, 3145 Power command value storage and transmission circuit, 3146 management circuit, 4041 charge control circuit, 4042 discharge control circuit, 4043 first switching circuit, 4044 third control circuit, 4091 AC frequency detection circuit, 4092 effective power calculation circuit, 4093 virtual synchronous generator control circuit, 4094 inverter current control circuit, 4095 inverter voltage control circuit, 4096 second switching circuit, 4097 fourth control circuit, 40910 phase detection circuit, 40911 frequency detection circuit, 40912 first sine wave generation circuit, 40932 subtractor, 40933 governor control circuit, 40935 adder, 40936 subtractor, 40937 mass system calculation circuit, 40941 subtractor, 40942 first PI control circuit, 40943 multiplier, 40944 Subtractor, 40945 Second PI control circuit, 40946 First PWM converter, 40951 Second sine wave generating circuit, 40952 Subtractor, 40953 Third PI control circuit, 40954 Second PWM conversion circuit, 40955 First current limiting circuit, 409331 Multiplier, 409332 First-order lag system model, 409333 Limiter circuit, 409371 Subtractor, 409372 Integrator, 409373 Multiplier, 409374 Divider, 409375 Adder, 409376 Phase calculation circuit.

Claims

1. A distributed power source management device that manages one or more distributed power sources, wherein each of the one or more distributed power sources is connected to a power grid and operates as a voltage source, and the relationship between the frequency and power of each of the one or more distributed power sources has a droop characteristic and is adjusted such that a frequency command value and a power command value correspond to each other. The distributed power source management device includes an AC frequency collection unit that collects information on the AC frequency of the power grid and determines a representative value of the AC frequency based on the collected AC frequency information, and a frequency command value generation unit that generates the frequency command value for each of the one or more distributed power sources based on the representative value of the AC frequency.

2. The distributed power source management device further includes a droop characteristic management unit that manages, as droop characteristic information, the shape of the droop characteristic or a parameter that determines the shape of the droop characteristic corresponding to each of the one or more distributed power sources. The frequency command value generation unit generates the frequency command value for each of the one or more distributed power sources based on the corresponding droop characteristic information managed by the droop characteristic management unit in addition to the representative value of the AC frequency. The distributed power source management device according to claim 1.

3. The distributed power source management device further includes an operation plan creation unit that creates an operation plan corresponding to each of the one or more distributed power sources and generates the power command value corresponding to each of the one or more distributed power sources based on the corresponding operation plan. The frequency command value generation unit generates the frequency command value for each of the one or more distributed power sources based on the corresponding power command value generated by the operation plan creation unit in addition to the representative value of the AC frequency and the corresponding droop characteristic information stored in the droop characteristic management unit. The distributed power source management device according to claim 2.

4. The frequency command value generation unit determines the maximum frequency and the minimum frequency that each of the one or more distributed power sources can obtain based on the power capacity corresponding to each of the one or more distributed power sources. When the representative value of the AC frequency at the current time is not included in the frequency reference range based on the maximum frequency and the minimum frequency, the frequency command value generation unit changes the frequency command value to a value based on the representative value of the AC frequency at the current time. The distributed power source management device according to claim 3.

5. When the frequency command value generation unit changes the frequency command value of the first distributed power source among the one or more distributed power sources, (i) under the assumption that the frequency command value of the first distributed power source is set equal to the representative value of the current AC frequency, the maximum frequency and the minimum frequency that the first distributed power source can obtain are calculated, and when a first condition that the calculated maximum frequency and minimum frequency are within a predetermined rated frequency range based on the rated frequency of the power system is satisfied, the frequency command value is actually set equal to the representative value of the current AC frequency, and (ii) when the first condition is not satisfied, the frequency command value is set to a value shifted from the representative value of the current AC frequency so that the first condition is satisfied. The distributed power source management device according to claim 4.

6. A plurality of distributed power sources are connected to the power system as the one or more distributed power sources, and the frequency command value generation unit generates the frequency command value of each of the plurality of distributed power sources so that the maximum frequency and the minimum frequency that each of the plurality of distributed power sources can obtain substantially coincide with each other. The distributed power source management device according to any one of claims 3 to 5.

7. A distributed power source management device for managing one or more distributed power sources, each of the one or more distributed power sources being connected to a power system and operating as a voltage source, the relationship between the frequency and the power of each of the one or more distributed power sources having a droop characteristic, and the frequency command value and the power command value being adjusted to correspond to each other. The distributed power source management device includes an AC frequency collection unit that collects information on the AC frequency of the power system and determines a representative value of the AC frequency based on the collected AC frequency information, and a power command value correction unit that corrects the power command value of each of the one or more distributed power sources based on the representative value of the AC frequency.

8. The distributed power source management device further includes a droop characteristic management unit that manages, as droop characteristic information, the shape of the droop characteristic or a parameter that determines the shape of the droop characteristic corresponding to each of the one or more distributed power sources. The power command value correction unit corrects the power command value of each of the one or more distributed power sources based on the corresponding droop characteristic information managed by the droop characteristic management unit in addition to the representative value of the AC frequency. The distributed power source management device according to claim 7.

9. The distributed power source management device further includes an operation plan creation unit that creates an operation plan corresponding to each of the one or more distributed power sources and generates a power command value for each of the one or more distributed power sources based on the corresponding operation plan. The power command value correction unit corrects the power command value generated by the operation plan creation unit based on the representative value of the AC frequency and the corresponding droop characteristic information stored in the droop characteristic management unit. The distributed power source management device according to claim 8.

10. The power command value correction unit determines the maximum frequency and the minimum frequency that each of the one or more distributed power sources can obtain based on the power capacity corresponding to each of the one or more distributed power sources. When the representative value of the AC frequency at the current time is not included in the frequency reference range based on the maximum frequency and the minimum frequency, the power command value correction unit corrects the power command value to a value based on the representative value of the AC frequency at the current time. The distributed power source management device according to claim 9.

11. When the power command value correction unit corrects the power command value of the first distributed power source among the one or more distributed power sources: (i) Assuming that the power command value corresponding to the frequency command value is corrected to a first value so that the power value at the representative value of the AC frequency at the current time is equal to the power command value generated by the operation plan creation unit, the maximum frequency and the minimum frequency that the first distributed power source can obtain are calculated. When the calculated maximum frequency and minimum frequency are within a predetermined rated frequency range based on the rated frequency of the power system and the first value is within the power supply capacity of the first distributed power source, the power command value corresponding to the frequency command value is actually corrected to the first value. (ii) When the first condition is not satisfied, the power command value corresponding to the frequency command value is corrected to a value shifted from the first value so that the first condition is satisfied. The distributed power source management device according to claim 10.

12. A plurality of distributed power sources are connected to the power system as the one or more distributed power sources. The power command value correction unit corrects the power command value of each of the plurality of distributed power sources so that the maximum frequency and the minimum frequency that each of the plurality of distributed power sources can obtain substantially coincide with each other. The distributed power source management device according to any one of claims 9 to 11.

13. Each of the one or more distributed power sources executes virtual synchronous generator control that simulates the operation of a synchronous generator, and the droop characteristic management unit stores, as the droop characteristic information, a governor time constant, a speed regulation rate, an inertia constant, and a braking coefficient, which are control parameters when executing the virtual synchronous generator control. The distributed power source management device according to any one of claims 2 to 6 and 8 to 12.

14. A plurality of distributed power sources are connected to the power system as the one or more distributed power sources, each of the plurality of distributed power sources calculates an AC frequency based on the voltage of the power system, and the AC frequency collection unit collects a calculated value of the AC frequency from at least one of the plurality of distributed power sources as information on the AC frequency. The distributed power source management device according to any one of claims 3 to 6 and 9 to 12.

15. The power system is an autonomous system, and the representative value of the AC frequency is a calculated value of the AC frequency collected from the distributed power source having the largest power capacity among the plurality of distributed power sources or the distributed power source corresponding to the largest power command value among the power command values generated by the operation plan creation unit. The distributed power source management device according to claim 14.

16. [Correction based on Rule 91, 13.03.2025] A distribution system including one or more distributed power sources each operating as a voltage source, wherein the relationship between the frequency and power of each of the one or more distributed power sources has a droop characteristic, and the frequency command value and the power command value are adjusted to correspond to each other, and further including the distributed power source management device according to any one of claims 1 to 15 for managing the one or more distributed power sources.

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