Power converter management device and DC power distribution system

Abstract

A power conversion device (CEMS) (3) is a power converter management device that is installed in a DC power distribution system and manages a plurality of power converters having drooping characteristics for exchanging DC power with the DC power distribution system, said power conversion device (CEMS) (3) comprising a control parameter generation circuit (33) that is configured to estimate a voltage fluctuation width at an interconnection point of each power converter with the DC power distribution system when tidal power or a tidal current flowing through the DC power distribution system changes, and to generate the drooping characteristics of the power converters on the basis of the voltage fluctuation width at the interconnection point of each power converter with the DC power distribution system.

Description

Power Converter Management Device and DC Power Distribution System

[0001] The present disclosure relates to a power converter management device and a DC power distribution system.

[0002] Conventionally, a power conversion device using a droop control method has been known. For example, the power conversion device described in Patent Document 1 generates an output current correction value for correcting an output current value based on an output current target value, which is a target value of an output current output from the power conversion device, and the output current value. And a droop control unit that droops an output voltage target value, which is a target value of an output voltage output from the power conversion device, based on a corrected output current value that is the output current value corrected by the output current correction value. The output voltage is controlled based on the drooped output voltage target value and the output voltage value.

[0003] WO2023 / 063073

[0004] In Patent Document 1, appropriate control cannot be executed when the consumer load fluctuates or the generated power of the energy generation device fluctuates.

[0005] Therefore, an object of the present disclosure is to provide a power converter management device and a DC power distribution system capable of appropriate control even when the consumer load fluctuates or the generated power of the energy generation device fluctuates.

[0006] The power conversion device of the present disclosure is a power converter management device that is installed in a DC power distribution system and manages a plurality of power converters having a droop characteristic for exchanging DC power with the DC power distribution system. When the power flow power or power flow current flowing through the DC power distribution system changes, the voltage fluctuation range of the connection point of each power converter with the DC power distribution system is estimated, and based on the voltage fluctuation range of the connection point of each power converter with the DC power distribution system, a control parameter generation circuit configured to generate the droop characteristic of each power converter.

[0007] According to the present disclosure, appropriate control is possible even when the consumer load fluctuates or the generated power of the energy generation device fluctuates.

[0008] [Correction based on Rule 91 25.12.2025] This is a block diagram showing the configuration of the DC power distribution system 500 according to Embodiment 1. This is a block diagram of the CEMS 3 shown in Figure 1 according to Embodiment 1. This is a block diagram of the operation plan creation circuit 34 in the CEMS 3 shown in Figure 2 according to Embodiment 1. This is a block diagram of the control parameter generation circuit 33 in the CEMS 3 shown in Figure 2 according to Embodiment 1. This is a block configuration diagram of the AC / DC converter 6 shown in Figure 1. This is a block configuration diagram of the power conversion device 9 for the power distribution system battery shown in Figure 1. This is a block configuration diagram of the power conversion device 13 for the consumer PV shown in Figure 1. This is a block diagram illustrating the configuration of the first control circuit 64 that controls the first AC / DC conversion circuit 63 of the AC / DC converter 6. This is a block diagram illustrating the configuration of the second control circuit 94 that controls the first DC / DC conversion circuit 93 of the power conversion device 9 for the power distribution system battery. This is a block diagram illustrating the configuration of the third control circuit 134 that controls the second DC / DC conversion circuit 133 of the power conversion device 13 for the consumer PV. This is a block diagram illustrating an example configuration of the first voltage target generation circuit 682 (second voltage target generation circuit 942) shown in Figure 8 (Figure 9). This is a block diagram illustrating the configuration of the first governor control circuit 6822 (9422) shown in Figure 11. This is a block diagram illustrating the configuration of the first mass-point system calculation circuit 6825 (9425) shown in Figure 11. This is a block diagram illustrating an example configuration of the power target generation circuit 943 shown in Figure 9. This is a block diagram illustrating the configuration of the second governor control circuit 9432 shown in Figure 14. This is a block diagram illustrating the configuration of the second mass-point system calculation circuit 9435 shown in Figure 14. This is a diagram for illustrating the transfer functions of the first voltage target generation circuit 682, the second voltage target generation circuit 942, and the power target generation circuit 943 shown in Figures 11 and 14 according to Embodiment 1. This is a block diagram illustrating an example configuration of the second voltage target value control circuit 945 shown in Figure 9. This is a block diagram illustrating an example configuration of the power target value control circuit 946 shown in Figure 9. This figure shows an example of the drooping characteristics (power-voltage characteristics) implemented in the AC / DC converter 6 or the power conversion device 9 for a power distribution system battery according to Embodiment 1. This figure shows an example of the drooping characteristics (voltage-power characteristics) implemented in the power conversion device 9 for a power distribution system battery according to Embodiment 1.This figure illustrates the generation image of the drooping characteristics of each power converter 9 for distribution system batteries, taking into account the changes in the power flow current flowing through the DC distribution system 21 according to Embodiment 1. This figure illustrates the operation of the AC / DC converter 6 operating in voltage control mode and the power converter 9 for distribution system batteries according to Embodiment 1. This figure illustrates the operation of the AC / DC converter 6 operating in voltage control mode and the power converter 9 for distribution system batteries operating in power control mode according to Embodiment 1. This is a sequence diagram of the normal operation of the power converter management device centered on the CEMS 3 shown in Figure 1 according to Embodiment 1. This is a flowchart illustrating the control operation of the CEMS 3 shown in Figure 1 according to Embodiment 1. This is a flowchart illustrating the detailed operation of the estimation of system impedance in S100 shown in Figure 26 according to Embodiment 1. This is a flowchart illustrating the detailed operation of the creation of the operation plan 1 in S105 shown in Figure 26 according to Embodiment 1. This is a flowchart illustrating the detailed operation of the formulation of the power distribution system battery charge / discharge power (power command value) 1 in S1054 shown in Figure 28 according to Embodiment 1. This is a flowchart explaining the detailed operation of the voltage prediction 1 at each power receiving point, S1057, shown in Figure 28 according to Embodiment 1. This is a flowchart explaining the detailed operation of the power distribution system battery charge / discharge power review 1, S1060, shown in Figure 28 according to Embodiment 1. This is a flowchart explaining the detailed operation of the drooping characteristic generation 1, S1061, shown in Figure 28 according to Embodiment 1. This is a flowchart explaining the detailed operation of the operation plan correction decision, S108, shown in Figure 26 according to Embodiment 1. This is a flowchart explaining the detailed operation of the operation plan correction 1, S109, shown in Figure 26 according to Embodiment 1. This is a flowchart explaining the detailed operation of the power command value correction 1 for the power distribution system battery 8, S10905, shown in Figure 34 according to Embodiment 1. This is a flowchart explaining the detailed operation of the power command value correction based on SOC, S10909, shown in Figure 34 according to Embodiment 1. This is a flowchart explaining the detailed operation of the drooping characteristic generation 2, S10916, shown in Figure 34 according to Embodiment 1. This is a flowchart illustrating the operation of the first control circuit 64 shown in Figure 5 according to Embodiment 1.This is a flowchart explaining the operation of the first AC / DC conversion circuit control S204 shown in Figure 38 according to Embodiment 1. This is a flowchart explaining the operation of the second control circuit 94 shown in Figure 6 according to Embodiment 1. This is a flowchart explaining the operation of the first DC / DC conversion circuit control S304 shown in Figure 40 according to Embodiment 1. This is a diagram showing an example of the drooping characteristics (power-voltage characteristics) to be implemented in the AC / DC converter 6 or the power conversion device 9 for the power distribution system battery according to Embodiment 2. This is a diagram showing an example of the drooping characteristics (voltage-power characteristics) to be implemented in the power conversion device 9 for the power distribution system battery according to Embodiment 2. This is a flowchart explaining the control operation of the CEMS 3 shown in Figure 1 according to Embodiment 2. This is a flowchart explaining the detailed operation of the operation of the creation of the operation plan 2 S120 shown in Figure 44 according to Embodiment 2. This is a flowchart for explaining the detailed operation of the voltage prediction 2 for each power receiving point S1070 shown in Figure 45 according to Embodiment 2. This is a flowchart explaining the detailed operation of the voltage / power command value review 1 for the power distribution system battery 8 S1071 shown in Figure 45 according to Embodiment 2. This is a flowchart explaining the detailed operation of the voltage command value revision of the power distribution system battery 8 shown in S1075 in Figure 47 according to Embodiment 2. This is a flowchart explaining the detailed operation of the voltage command value revision of the power distribution system battery 8 shown in S1075 in Figure 47 according to Embodiment 2. This is a diagram to explain an example of a voltage command value creation method. This is a flowchart explaining the detailed operation of the droop characteristic generation 3 shown in S1072 in Figure 45 according to Embodiment 1. This is a flowchart for explaining the detailed operation of the operation plan modification 2 shown in S145 in Figure 44 according to Embodiment 2. This is a flowchart explaining the detailed operation of the voltage / power command value revision 2 of the power distribution system battery 8 shown in S14502 in Figure 50 according to Embodiment 2. This is a flowchart explaining the detailed operation of the power distribution system battery voltage command value revision 2 shown in S10925 in Figure 51 according to Embodiment 2. This is a flowchart explaining the detailed operation of the power distribution system battery voltage command value revision 2 shown in S10925 in Figure 51 according to Embodiment 2. This is a flowchart illustrating the detailed operation of the drooping characteristic generation 4 in S14503 shown in Figure 50, which relates to Embodiment 2.This figure shows an example of a dead-zone-free drooping characteristic (power-voltage characteristic) to be implemented in the AC / DC converter 6 or the power conversion device 9 for the distribution system battery. This figure shows an example of a dead-zone-free drooping characteristic (voltage-power characteristic) to be implemented in the AC / DC converter 6 or the power conversion device 9 for the distribution system battery. This figure shows an example of a dead-zone-included drooping characteristic (power-voltage characteristic) to be implemented in the AC / DC converter 6 or the power conversion device 9 for the distribution system battery. This figure shows an example of a dead-zone-included drooping characteristic (voltage-power characteristic) to be implemented in the AC / DC converter 6 or the power conversion device 9 for the distribution system battery. This figure shows an example of a curve-based drooping characteristic (power-voltage characteristic) or drooping characteristic (voltage-power characteristic) to be implemented in the AC / DC converter 6 or the power conversion device 9 for the distribution system battery.

[0009] The embodiments will be described in detail below with reference to the drawings. In the following, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their descriptions will not be repeated in principle. Components Xa, Xb, and Xc may be collectively referred to as X (where X is a number).

[0010] Background to this disclosure. In recent years, the introduction of renewable energy sources such as solar and wind power (hereinafter referred to as "renewable energy") has been progressing due to the need to reduce environmental burden, such as CO2 emissions, and the problem of energy resource depletion. Renewable energy sources such as solar cells (hereinafter referred to as "PV") output DC power, so they are highly compatible with DC transmission and distribution, and DC conversion is already progressing in data centers. In unelectrified areas of India and African countries, the development of AC trunk grids is progressing to promote electrification, and in areas where the development of trunk grids is lagging, DC microgrids using renewable energy such as PV as the main power source are being constructed to promote electrification. In the future, it is expected that connections between neighboring DC microgrids and connections with AC trunk grids (Hybrid DC Microgrids) will progress. Furthermore, with the introduction of a "border carbon tax" in Europe scheduled for 2026, it is expected that the introduction of renewable energy sources such as solar cells will accelerate in factories and other facilities. As mentioned above, DC power transmission and distribution, which is highly compatible with DC power, is expected to become widespread in various settings, including factories, office buildings, local government disaster prevention centers, and the aforementioned DC microgrids, provided that economic rationality can be ensured.

[0011] Generally, DC power transmission and distribution does not require frequency management compared to AC power transmission and distribution, so converter control can be simplified, but it lacks the inertia force that AC power transmission and distribution systems possess. In AC power transmission and distribution systems, when the load power consumption changes suddenly, or when the power generated by renewable energy sources changes suddenly, the inertia force (the inertia force of the rotating body) of a synchronous generator installed in a thermal power plant is used to adjust for power surplus or deficit. Specifically, if there is surplus power in the transmission and distribution system, the surplus power is converted into kinetic energy and stored in the rotating body (the AC system frequency rises as the rotational speed of the rotating body increases), and if there is a power deficit, the kinetic energy of the rotating body is converted into electrical energy and output (the AC system frequency falls as the rotational speed of the rotating body decreases).

[0012] On the other hand, DC power transmission and distribution systems lack power supply equipment that possesses the inertial force of synchronous generators. For example, consider a DC power distribution system as shown in Figure 1, where the switch 5 is open and a DC microgrid is constructed using n distribution system batteries 8. Each distribution system battery power converter 9 controls the connection point voltage with the DC power distribution system 21 to 1500V. Now, let's assume that the consumer load 11n of the consumer load group 10n changes suddenly, resulting in a power shortage. When a power shortage occurs, the DC voltage of the DC power distribution system 21n drops. As a result, the distribution system battery power converter 9n detects the power shortage and increases the discharge power. Similarly, surplus and deficit power are supplied from other distribution system batteries 8 connected via the distribution system impedance 7n until a steady state is reached (the DC voltage of the DC power distribution system 21n converges to 1500V). However, in the steady state, the distribution system batteries 8n share the surplus and deficit power.

[0013] As described above, in conventional DC power transmission and distribution systems, load fluctuations or power generation fluctuations occurring within a customer load group 10n are, in a steady state, compensated for by the supply of excess or insufficient power from the distribution system battery 8n installed within the customer load group 10n, and it is not possible to coordinate operation with other distribution system batteries 8.

[0014] To address these challenges, various companies are developing technologies to give DC / DC converters, which connect DC power output from distributed power sources such as storage batteries to DC power transmission and distribution systems, a pseudo-inertial force (drooping characteristic). Patent Document 1 discloses a method for controlling the connection point voltage with a DC system by giving a drooping characteristic to a DC / DC converter that boosts, bucks, or steps down the DC power input from a DC power source and outputs it. More specifically, the power conversion device described in Patent Document 1 measures the output current and output voltage output from the DC / DC converter and controls the output voltage output from the DC / DC converter. This power conversion device generates an output current correction value that corrects the output current value based on the output current target value, which is the target value of the output current output from the DC / DC converter, and the output current value. Based on the corrected output current value corrected by the output current correction value, this power conversion device droops the output voltage target value, which is the target value of the output voltage output from the DC / DC converter, and controls the output voltage output from the DC / DC converter based on the drooped output voltage target value.

[0015] Problems this disclosure aims to solve. When a factory or microgrid is configured with a DC distribution system, maintaining and managing the voltage of the DC distribution system, and controlling power flow between connected distributed power sources such as batteries and renewable energy equipment and loads are important. In particular, in a DC distribution system 21 as shown in Figure 1, the power flow of power (current) flowing through the DC distribution system 21 can be managed by the distributed power sources (power converters) managing the interconnection point voltage with the DC distribution system 21. In power flow management, in addition to the direction of the power flow current, it is necessary to consider the voltage drop due to the impedance of the DC distribution system 21 (resistive components are dominant in the DC distribution system 21) and generate a drooping characteristic for each distributed power source. Specifically, at the end of the power flow, for example, if the load power consumption increases and the power flow current of the DC distribution system 21 increases in the forward direction, the fluctuation range of the interconnection point voltage of each distributed power source with the DC distribution system 21 becomes larger towards the end of the power flow. Therefore, the drooping characteristic needs to be determined such that, at the end of the power flow, the amount of output voltage fluctuation in response to power fluctuations is large in the case of the voltage control mode described later, or the amount of output power in response to the voltage fluctuation range is small in the case of the power control mode described later. On the other hand, the power converter and DC power supply system described in Patent Document 1 have the current-voltage drooping characteristic described above. In this case, multiple power converters can operate as masters (voltage sources) within the DC distribution system 21, but the influence of power flow and other factors on the DC distribution system 21 is not taken into consideration. As a result, in the DC distribution system 21 shown in Figure 1, there was a problem in that the interconnection point voltage and charge / discharge power (especially the SOC of the distribution system battery 8) of each power converter 9 for the distribution system battery could not be adequately managed.

[0016] This disclosure relates to a power converter management device that manages a DC / DC converter connected to a DC distributed power supply connected to a DC system having a drooping characteristic, and an AC / DC converter connecting the DC system and the AC system. This disclosure was made to solve the problems described above. The power converter management device of this disclosure (a higher-level EMS (Energy Management System)) generates control commands (specifically, drooping characteristic, voltage command value, and power command value (or current command value)) for the DC / DC converter and AC / DC converter having a drooping characteristic, generating voltage command values ​​and power command values ​​so that the interconnection point voltage with the DC system falls within a predetermined voltage range. The power converter management device of this disclosure estimates the range of fluctuations in the interconnection point voltage of each power converter 9 for distribution system batteries with the DC distribution system 21 due to demand fluctuations, based on the generated voltage command value and power command value, the control mode of each power converter 9 for distribution system batteries, the demand power of the customer load group 10, the power supply information from the substation 1, the power flow current (power) of the DC distribution system 21, and the impedance information of the distribution system. The power converter management device of this disclosure generates the drooping characteristics of each power converter 9 for distribution system batteries based on the estimation results and control mode.

[0017] According to this disclosure, the power converter management device is configured to generate the drooping characteristics of each power converter connected to the DC system by predicting (estimating) the range of fluctuation at the interconnection point between each power converter and the DC distribution system 21 when the power current (power flow) changes. As a result, even when the power flow changes due to fluctuations in the load of the consumer load or fluctuations in the power generated by the energy creation equipment (fluctuations in demand power), it is possible to control the distribution of output power of each power converter, as well as control the interconnection point voltage of the power converters with the DC distribution system and the power flow (power flow current) flowing through the DC distribution system.

[0018] Overview of Embodiments. First, an overview of the embodiments of this disclosure will be described.

[0019] (1) A power converter management device (CEMS3) in one aspect of the present disclosure is a power converter management device (CEMS3) installed in a DC distribution system (21) that manages a plurality of power converters (AC / DC converters 6, power converter management devices 9a to 9n for distribution system batteries) having a drooping characteristic that exchanges DC power with the DC distribution system (21), and which manages each power converter (AC / DC converters 6, distribution system battery power converter management devices 9a to 9n) when the power flow or power flow current flowing through the DC distribution system (21) changes The system includes a control parameter generation circuit (33) configured to estimate the voltage fluctuation range at the connection point between the power conversion management devices 9a to 9n for power system battery storage and the DC distribution system (21), and to generate the drooping characteristics of each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for power distribution system battery storage) based on the voltage fluctuation range at the connection point between each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for power distribution system battery storage and the DC distribution system (21).

[0020] (2) The power converter management device (CEMS3) described in (1) above further includes an operation plan creation circuit (34) configured to estimate power flow or power flow based on the voltage measurement results at the interconnection points of the DC distribution system (21) managed by each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries), at least one of the current measurement results and power measurement results output by each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries), and the demand power consumed by each consumer.

[0021] (3) In the power converter management device (CEMS3) described in (2) above, the operation plan creation circuit (34) is configured to predict the power generated by the energy generation equipment (12a to 12n) connected to the DC distribution system (21) based on weather forecast information, and to predict the power demand of the customer loads (11a to 11n) connected to the DC distribution system (21), and to generate power command values ​​or current command values ​​for each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) based on the surplus or deficit power, which is the difference between the predicted power generated and the predicted power demand.

[0022] (4) In the power converter management device (CEMS3) described in (3) above, the multiple power converters (AC / DC converters 6, power conversion management devices 9a to 9n for distribution system batteries) include power converters (power conversion management devices 9a to 9n for distribution system batteries) to which batteries (8a to 8n) are connected, and the operation plan creation circuit (34) is configured to generate power command values ​​or current command values ​​for the power converters (power conversion management devices 9a to 9n for distribution system batteries) to which batteries (8a to 8n) are connected, based on the excess or deficit power and the amount of energy charged to the batteries (8a to 8n).

[0023] (5) In the power converter management device (CEMS3) described in (4) above, a group of customer loads (10a to 10n) is formed by a plurality of energy generation devices (12a to 12n) and a plurality of customer loads (11a to 11n) managed by power converters (AC / DC converters 6, power conversion management devices 9a to 9n) having a drooping characteristic, and the operation plan creation circuit (34) is configured to predict the power generated by the energy generation devices (12a to 12n) and the power demanded by the customer loads (11a to 11n) on a unit basis of the group of customer loads (10a to 10n).

[0024] (6) In the power converter management device (CEMS3) described in (3) to (5) above, the operation plan creation circuit (34) is configured to estimate power flow or power flow current based on the voltage command value of each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries), one or both of the power command value and current command value of each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries), the predicted power generation result of the energy generation equipment (12a to 12n), and the predicted power demand result of the customer load (11a to 11n).

[0025] (7) In the power converter management device (CEMS3) described in (2) to (6) above, the operation plan creation circuit (34) is configured to estimate the impedance of the DC distribution system (21) between each power converter (AC / DC converter 6, power conversion management device 9a to 9n for distribution system batteries) based on the estimation result of the power flow or power flow current and the voltage measurement result of the interconnection point between each power converter (AC / DC converter 6, power conversion management device 9a to 9n for distribution system batteries) and the DC distribution system (21).

[0026] (8) In the power converter management device (CEMS3) described in (2) to (6) above, the operation plan creation circuit (34) is configured to estimate the impedance of the DC distribution system (21) between each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) based on the system information of the DC distribution system (21) and the impedance information of the transmission and distribution lines.

[0027] (9) In the power converter management device (CEMS3) described in (7) or (8) above, the control parameter generation circuit (33) is configured to estimate the range of voltage fluctuation at the connection point between the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) and the DC distribution system (21) when the power current changes, based on the estimation result of the impedance of the DC distribution system (21).

[0028] (10) In the power converter management device (CEMS3) described in (2) to (9) above, the operation plan creation circuit (34) is configured to use a first drooping characteristic having power-voltage characteristics when the control mode of the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) is a voltage command value control mode that controls the DC voltage of the DC distribution system (21), and to use a second drooping characteristic having voltage-power characteristics when the control mode of the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) is a power command value control mode that controls the value of power or current output by the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries).

[0029] (11) In the power converter management device (CEMS3) described in (10) above, the control parameter generation circuit (33) generates the control mode of the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries), the converter capacity of the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries), the estimated impedance of the DC distribution system (21), and the voltage fluctuation range at the connection point with the DC distribution system (21). The drooping characteristics of the power converter (AC / DC converter 6, power conversion management devices 9a-9n for distribution system batteries) are generated using at least one of the following: the estimation results, the predicted power generation results of the energy creation equipment (12a-12n), the predicted power demand results of the customer load (11a-11n), and the amount of charge of the batteries (8a-8n) when the power converter (power conversion management devices 9a-9n for distribution system batteries) is connected to the batteries (8a-8n).

[0030] (12) In the power converter management device (CEMS3) described in (3) above, the control parameter generation circuit (33) controls the power converters (power converter management devices 9a to 9n) to which the batteries (8a to 8n) are connected, so that when a change in supply and demand power occurs, the allocation of differential power to each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) is approximately equal to the ratio of the power command values, based on the voltage fluctuation range at the connection point of each power converter with the DC distribution system (21).

[0031] (13) In the power converter management device (CEMS3) described in (2) to (12) above, the control parameter generation circuit (33) is configured to generate a drooping characteristic applied to each power converter, including the dead zone of each power converter (power converter management device 9a to 9n for distribution system batteries) to which the batteries (8a to 8n) are connected, based on the voltage fluctuation range at the connection point of each power converter (AC / DC converter 6, power conversion management device 9a to 9n for distribution system batteries) with the DC distribution system (21).

[0032] (14) In the power converter management devices described in (2) to (13) above, the control parameter generation circuit (33) determines the slope of the drooping characteristic of each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) based on the estimation result of the voltage fluctuation range at the connection point of each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) with the DC distribution system (21).

[0033] (15) In the power converter management device (CEMS3) described in (14) above, the control parameter generation circuit (33) determines the slope of the drooping characteristic of each power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) based on the control mode of each power converter.

[0034] (16) In the power converter management device (CEMS3) described in (2) to (15) above, the control parameter generation circuit (33) is configured to select a drooping characteristic defined for each power converter (AC / DC converter 6, power conversion management device 9a to 9n) if the estimated power flow or power flow current is within a predetermined range defined for each power converter (AC / DC converter 6, power conversion management device 9a to 9n for distribution system batteries).

[0035] (17) In the power converter management device (CEMS3) described in (2) to (16) above, the operation plan creation circuit (34) generates a voltage command value based on the estimated voltage at the connection point between the power converter (AC / DC converter 6, power conversion management devices 9a to 9n for distribution system batteries) having a drooping characteristic and the DC distribution system (21).

[0036] (18) A DC power distribution system according to one aspect of the present disclosure comprises a power converter management device (CEMS3) as described in any one of (1) to 17) above, a DC power distribution system (21), and a plurality of power converters (AC / DC converters6, power conversion management devices 9a to 9n for power distribution system batteries).

[0037] Embodiment 1. Figure 1 is a diagram showing a DC power distribution system 500 according to Embodiment 1. The DC power distribution system 500 comprises at least a DC power distribution system 21, an AC / DC converter 6, power conversion devices 9a to 9n for the power distribution system battery, and power distribution system batteries 8a to 8n. In Embodiment 1, the standard DC voltage of the DC power distribution system 21 is set to 1500V, and the appropriate voltage range is set to 1350V to 1650V (±10% of the standard DC voltage). The standard DC voltage is not limited to 1500V, but may be 600V, 380V, or 6000V, etc. The appropriate voltage range is set to ±10% of the standard appropriate voltage, but is not limited to this, and may be, for example, ±5% of the standard appropriate voltage, -10% to 2%, etc. Embodiment 1 describes the case of three-phase AC, but is not limited to three-phase AC, and may be single-phase AC or single-phase three-wire AC, etc.

[0038] Three-phase AC power from substation 1 is input to switch 5 via AC distribution system 20a. The output of switch 5 is connected to AC / DC converter 6 via AC distribution system 20b. In Embodiment 1, DC distribution system 21 is normally connected to AC distribution system via AC / DC converter 6. In the event of a power outage, switch 5 disconnects DC distribution system 21 from the higher-level transmission (main) system, and DC distribution system 21 forms a DC self-sustaining system (DC microgrid).

[0039] The Distribution System Operator (DSO) 2 collects, for example, power consumption for each customer load group 10 and power generation and status information of the PV (Photovoltaics) panel 12, as well as charge / discharge power, SOC (State of Charge) information, and SOH (State of Health) information of the distribution system battery 8, via the Cluster / Community Energy Management System (CEMS) 3, which is a power converter management device. Based on the collected results, the DSO 2 generates, for example, power supply information from the upstream (main) system for 30 minutes and outputs it to the CEMS 3. The CEMS 3 manages the collection of charge / discharge power, SOC information, and SOH information of the distribution system battery 8, generates power command values ​​and voltage command values ​​for the AC / DC converter 6 and each distribution system battery power converter 9 (creation of battery operation plan), and generates and manages droop characteristics, etc. In Embodiment 1, the weather forecast server 4 outputs weather forecast information for 24 hours at 30-minute intervals. The information from the weather forecast server 4 is not limited to 30-minute intervals; although the accuracy of the prediction of the amount of power generated by the PV panel 12 will differ, it may be at finer intervals (e.g., every minute) or longer intervals (e.g., every 6 hours). The CEMS 3 and the weather forecast server 4 are connected to the communication line 22.

[0040] The AC / DC converter 6 converts the AC power supplied from the AC distribution system 20b into DC power and outputs it to the DC distribution system 21 (forward power). If there is surplus power in the DC distribution system 21, the AC / DC converter 6 converts the surplus DC power from the DC distribution system 21 into AC power and outputs it to the AC distribution system 20b (reverse power). The DC distribution system 21 is connected to the power conversion device 9 for the distribution system battery and the customer load group 10, etc., via the distribution system impedance 7.

[0041] The power converter 9 for the power distribution system battery outputs DC power from the power distribution system battery 8 to the DC power distribution system 21. If there is surplus power in the DC power distribution system 21, the power converter 9 charges the power distribution system battery 8 with that surplus power.

[0042] The customer load group 10 includes customer loads 11, PV panels 12, and a customer PV power conversion device 13. In Embodiment 1, for easier understanding, the loads of a plurality of adjacent customers, the customer PV power conversion device 13 attached to the customer's house, etc. are grouped together as a customer load group. The customer PV power conversion device 13 outputs the DC power generated by the PV panel 12 to the DC distribution system 21. The power generation amount prediction database 351 and the power consumption prediction database 352, which will be described later, construct databases for each customer load group 10.

[0043] FIG. 2 is a block configuration diagram of the CEMS 3 shown in FIG. 1. Referring to FIG. 2, the CEMS 3 includes a communication circuit 31, a memory circuit 32, a control parameter generation circuit 33, an operation plan creation circuit 34, a transmission data generation circuit 35, and a distributed power management unit control circuit 36.

[0044] The communication circuit 31 transmits measurement information to the DSO 2 via the communication line 22, receives control commands (supply and demand (demand) plans for 24 hours) from the DSO 2, collects measurement data from communication terminals (such as smart meters not shown installed at each customer) within the customer load groups 10a to 10n, collects measurement data from the distribution system battery power conversion devices 9a to 9n and the AC / DC converter 6, and transmits command values (voltage command values and power command values) and droop characteristics to each converter (power conversion device).

[0045] The memory circuit 32 stores various information obtained via the communication circuit 31 (such as measurement data and status information of each distributed power source), various transmission data including command value information notified to each converter (power conversion device), and droop characteristics of each converter (power conversion device).

[0046] The control parameter generation circuit 33 determines the control modes of the AC / DC converter 6 and the distribution system battery power conversion devices 9a to 9n (the definition of the control mode will be described later), and generates an index representing the droop characteristic (in Embodiment 1, although details will be described later, the inertia constant M, the braking coefficient Dg, the speed regulation rate Kgd, and the governor time constant Tg), or the droop characteristic itself (for example, the droop characteristic with a dead zone described in Embodiment 2).

[0047] The operation plan creation circuit 34 creates operation plans for the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system batteries based on the control command (demand plan for 24 hours) from the DSO2. For example, in Embodiment 1, the operation plan can be a plan for 24 hours at 30-minute intervals.

[0048] The operation plan creation circuit 34 determines whether it is necessary to correct the operation plan based on the measurement information of the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system batteries (hereinafter also referred to as "each converter" in the following description) collected at a 5-minute cycle, and the SOC information and SOH information of the distribution system batteries 8a to 8n. When the operation plan creation circuit 34 determines that it is necessary to correct the operation plan, it corrects the operation plan for the period until the next control command is notified from the DSO2.

[0049] The transmission data generation circuit 35 generates transmission data (transmission packets) including the droop characteristic information (inertia constant M, braking coefficient Dg, speed adjustment rate Kgd, and governor time constant Tg in Embodiment 1) of each converter output from the control parameter generation circuit 33 and the voltage command value and power (current) command value of each converter output from the operation plan creation circuit 34 according to the control output output from the distributed power management unit control circuit 36. The transmission data generated by the transmission data generation circuit 35 is transmitted via the communication circuit 31 based on the transmission command from the distributed power management unit control circuit 36. The distributed power management unit control circuit manages the operations of the communication circuit 31, the storage circuit 32, the control parameter generation circuit 33, the operation plan creation circuit 34, and the transmission data generation circuit 35 within the CEMS3.

[0050] Figure 3 is a block diagram of the operation plan creation circuit 34 within the CEMS 3 shown in Figure 2. The operation plan creation circuit 34 includes a battery operation plan generation circuit 341, a power generation prediction circuit 342, a power consumption prediction circuit 343, a battery operation plan correction circuit 344, an operation plan creation unit management circuit 346, a power flow current estimation circuit 347, a grid voltage estimation circuit 348, a converter command value generation circuit 349, a grid impedance estimation circuit 350, a power generation prediction database 351, and a power consumption prediction database 352.

[0051] The battery operation plan generation circuit 341 generates an operation plan (30-minute intervals, 24-hour intervals) for the power converters 9a to 9n for the distribution system battery based on control command information (planned values ​​of power to be supplied to the DC distribution system 21 below substation 1 (supplied power) (planned every 30 minutes, for 24 hours)) notified from DSO2, the sum of the predicted power generation results of the PV panels 12 within each customer load group 10 predicted by the power generation prediction circuit 342, and the sum of the predicted power consumption information within each customer load group 10 predicted by the power consumption prediction circuit 343.

[0052] The power generation prediction circuit 342 obtains 24 hours' worth of weather forecast information from the weather forecast server 4 via the communication circuit 31. Based on the obtained weather forecast information, internal clock information (year, month, day, time) from the CEMS 3 (not shown), and information from the power generation prediction database 351, the power generation prediction circuit 342 predicts the total power generated by the PV panels 12 within each customer load group 10.

[0053] The power consumption prediction circuit 343 predicts the total power consumption of consumers within each consumer load group 10 connected to the DC distribution system 21, based on internal clock information (year, month, day, day of the week, time) from the CEMS 3 (not shown) and information from the power consumption prediction database 352.

[0054] The battery operation plan correction circuit 344 determines whether or not the operation plan needs to be modified based on the grid connection point voltage information of the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery, output power information, droop characteristic information, voltage and power command value information, and status information of the distribution system battery 8 (SOC information and SOH information) collected via the communication circuit 31. If the battery operation plan correction circuit 344 determines that the operation plan needs to be modified, it modifies the operation plan.

[0055] The operation plan creation management circuit 346 instructs the power flow estimation circuit 347 and the grid voltage estimation circuit 348 to verify the validity of the operation plan based on the output of the battery operation plan generation circuit 341, the output of the battery operation plan correction circuit 344, and the voltage command value and power command value of each converter generated by the converter command value generation circuit 349. If the estimated voltage of the DC distribution system 21 is outside a predetermined range, the operation plan creation management circuit 346 outputs an instruction to the battery operation plan generation circuit 341 (during operation plan creation) or the battery operation plan correction circuit 344 to regenerate or re-correct the operation plan in order to generate command values ​​(voltage command value and power (current) command value) again.

[0056] The power flow current estimation circuit 347 estimates the power flow current between each customer load group 10 based on the control commands and power command values ​​notified from the DSO2, the predicted power generation results of the PV panels 12 installed in each customer load group 10 predicted by the power generation prediction circuit 342, and the predicted power consumption results of the customer loads in each customer load group 10 predicted by the power consumption prediction circuit 343.

[0057] The grid voltage estimation circuit 348 estimates the voltage at the connection point of each converter with the DC distribution system 21 based on the power flow current estimation result output from the power flow current estimation circuit 347 and the distribution system impedance 7 between each customer load group 10 output from the grid impedance estimation circuit 350.

[0058] The converter command value generation circuit 349 checks whether the interconnection point voltage of each converter with the DC distribution system 21, output from the system voltage estimation circuit 348, falls within a predetermined voltage range. If even one of the interconnection point voltages of the converters with the DC distribution system 21 deviates from the predetermined voltage range, the converter command value generation circuit 349 revises all command values. If all of the interconnection point voltages of each converter with the DC distribution system 21 fall within the predetermined voltage range, the converter command value generation circuit 349 notifies the operation plan creation unit management circuit 346 of this fact.

[0059] The system impedance estimation circuit 350 estimates the distribution system impedance 7 based on the measurement results of the interconnection point voltage of each converter with the DC distribution system 21, the current (DC) flowing through the DC distribution system 21, and the drooping characteristics of each converter, which are stored in the memory circuit 32.

[0060] The operation plan creation unit management circuit 346 manages the operation of the power flow current estimation circuit 347, the grid voltage estimation circuit 348, the converter command value generation circuit 349, the grid impedance estimation circuit 350, the power generation forecast database 351, and the power consumption forecast database 352.

[0061] Figure 4 is a block diagram of the control parameter generation circuit 33 within the CEMS 3 shown in Figure 2. The control parameter generation circuit 33 includes a power flow current fluctuation range estimation circuit 331, a demand power fluctuation prediction circuit 332, a droop characteristic slope determination circuit 333, and a droop characteristic generation circuit 334.

[0062] In Embodiment 1, the AC / DC converter 6 operates in voltage control mode to manage the voltage of the DC power distribution system 21, and the power converters 9a to 9n for the power distribution system battery implement a power control mode in addition to the voltage control mode, and the control mode is determined by the configuration of the power distribution system. A detailed explanation of the configuration and operation of each control mode will be given later.

[0063] The power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current flowing through the DC power distribution system 21 based on the demand fluctuation prediction results output from the demand power fluctuation prediction circuit 332.

[0064] The power demand fluctuation prediction circuit 332 predicts fluctuations in power demand for each customer load group 10. Specifically, a smart meter installed in a customer's home (not shown) stores the maximum and minimum differences between the measurement results and the demand forecast over a 30-minute period, and sends these (maximum and minimum differences) along with the measurement results when a measurement data output request is received from the CEMS 3. In Embodiment 1, the maximum and minimum differences between the 30-minute demand forecast and the actual power demand are stored in the power consumption prediction database 352 (or power generation prediction database 351) along with weather, date, day of the week, and time information.

[0065] The power demand fluctuation prediction circuit 332 reads the maximum and minimum differences between the measurement results and the demand forecast from the power consumption prediction database 352, creates a demand fluctuation range for each customer load group 10 from the read demand power fluctuation range, and outputs it to the power flow current fluctuation range estimation circuit 331. Based on the demand fluctuation range for each customer load group 10 output from the power demand fluctuation prediction circuit 332, the power flow current fluctuation range estimation circuit 331 calculates the power to be allocated to each distribution system battery 8 when the maximum demand fluctuation occurs, and estimates the power flow current fluctuation range from the calculation result.

[0066] The droop characteristic slope determination circuit 333 determines the slope of the droop characteristic of each converter. In Embodiment 1, the power and voltage are converted to PU (Per Unit) values ​​to determine the slope of the droop characteristic. PU conversion means expressing the values ​​using the PU (Per Unit) method. Conventionally, in the case of voltage command value control, if the PU values ​​of the differential power output from each converter are the same, the slope of the droop characteristic was determined so that the differential values ​​of the output DC system voltages were approximately the same. In Embodiment 1, the droop characteristic slope determination circuit 333 estimates the fluctuation range of the interconnection point voltage of each converter with the DC distribution system from the system impedance estimation result information and the power flow current fluctuation range of each customer load group 10 output from the power flow current fluctuation range estimation circuit 331, and determines the slope of the droop characteristic based on the estimation result. The drooping characteristic generation circuit 334 determines control parameters (inertia constant M, damping coefficient Dg, speed adjustment ratio Kgd, and governor time constant Tg) based on the drooping characteristic slope information output from the drooping characteristic slope determination circuit 333.

[0067] Figure 5 is a block diagram of the AC / DC converter 6 shown in Figure 1. The AC / DC converter 6 includes voltmeters 61a and 61b, ammeters 62a and 62b, a first AC / DC conversion circuit 63, a first control circuit 64, a first communication interface circuit 65, a voltmeter 66, and an ammeter 67.

[0068] Voltmeters 61a and 61b, and ammeters 62a and 62b are connected to the switch 5. Voltmeters 61a and 61b measure AC voltage. Ammeters 62a and 62b measure AC current. The first AC / DC conversion circuit 63 converts AC voltage to a first DC voltage. The first control circuit 64 controls the first AC / DC conversion circuit 63. The first communication interface circuit 65 communicates with CEMS 3 and the like via the communication line 22. Voltmeter 66 and ammeter 67 are connected to the output of the first AC / DC conversion circuit 63. Voltmeter 66 measures DC voltage. Ammeter 67 measures DC current.

[0069] Figure 6 is a block diagram of the power converter 9 for distribution system batteries shown in Figure 1. The power converter 9 for distribution system batteries includes a voltmeter 91, an ammeter 92, a first DC / DC conversion circuit 93, a second control circuit 94, a second communication interface circuit 95, a voltmeter 96, and an ammeter 97.

[0070] The voltmeter 91 and ammeter 92 are connected to the power distribution system battery 8. The voltmeter 91 measures the DC voltage (second DC voltage). The ammeter 92 measures the DC current. The first DC / DC conversion circuit 93 converts the second DC voltage to a third DC voltage. The second control circuit 94 controls the first DC / DC conversion circuit 93, and the second communication interface circuit 95 communicates with the CEMS 3, etc., via the communication line 22. The voltmeter 96 and ammeter 97 are connected to the output of the first DC / DC conversion circuit 93. The voltmeter 96 measures the DC voltage. The ammeter 97 measures the DC current.

[0071] Figure 7 is a block diagram of the power converter 13 for customer PV installed within the customer load group 10 shown in Figure 1. The power converter 13 for customer PV includes a voltmeter 131, an ammeter 132, a second DC / DC conversion circuit 133, a third control circuit 134, a third communication interface circuit 135, a voltmeter 136, and an ammeter 137.

[0072] The voltmeter 131 and ammeter 132 are connected to the PV panel 12. The voltmeter 131 measures the DC voltage (fourth DC voltage). The ammeter 132 measures the DC current. The second DC / DC conversion circuit 133 converts the fourth DC voltage to the fifth DC voltage. The third control circuit 134 controls the second DC / DC conversion circuit 133. The third communication interface circuit 135 communicates with the CEMS 3, etc., via the communication line 22. The voltmeter 136 measures the DC voltage. The ammeter 137 measures the DC current. The voltmeter 136 and ammeter 137 are connected to the second DC / DC conversion circuit 133.

[0073] Figure 8 is a block diagram illustrating the configuration of the first control circuit 64 that controls the first AC / DC conversion circuit 63 of the AC / DC converter 6 shown in Figure 5. The first control circuit 64 comprises a current control circuit 640, a phase detection circuit 641, a first sine wave generation circuit 642, a fourth control circuit 647, a first power calculation circuit 681, and a first voltage target generation circuit 682.

[0074] The phase detection circuit 641 uses the measured value of the AC system voltage measured by the voltmeter 61 to detect the frequency and phase of the voltage of the AC distribution system 20. The first sine wave generation circuit 642 generates a sine wave synchronized with the voltage of the AC distribution system 20 used for current control, based on the frequency and phase detection results output from the phase detection circuit 641 and the voltage amplitude information of the voltage of the AC distribution system 20 output from the fourth control circuit 647.

[0075] The current control circuit 640 includes a subtractor 643, a first PI (Proportional Integral) control circuit 644, a multiplier 645, a subtractor 646, a second PI control circuit 648, and a first PWM (Pulse Width Modulation) conversion circuit 649.

[0076] The subtractor 643 subtracts the voltage of the DC power distribution system 21 measured by the voltmeter 66 from the voltage target value of the DC power distribution system 21 output from the fourth control circuit 647 (the voltage target value generated by the first voltage target generation circuit 682 is output via the fourth control circuit 647), and outputs the result to the first PI control circuit 644. The first PI control circuit 644 performs PI control so that the output of the subtractor 643 becomes zero. The multiplier 645 multiplies the output of the first sine wave generation circuit 642 and the output of the first PI control circuit 644. The subtractor 646 subtracts the output of the ammeter 62 from the output of the multiplier 645 and outputs the result to the second PI control circuit 648. The second PI control circuit 648 performs PI control so that the output of the subtractor 646 becomes zero, and outputs a current command value. The first PWM conversion circuit 649 applies PWM modulation to the current command value output from the second PI control circuit 648.

[0077] The first power calculation circuit 681 calculates the output power of the AC / DC converter 6 based on the output of the voltmeter 66 and the output of the ammeter 67. The first voltage target generation circuit 682 generates a voltage target value based on the output of the first power calculation circuit 681 and the output of the voltmeter 66, and outputs it to the fourth control circuit 647. The first voltage target generation circuit 682 has a drooping characteristic, which will be described later. The fourth control circuit 647 collects the measurement results related to the DC power distribution system 21 output from the voltmeter 66 and the ammeter 67, the measurement results related to the AC power distribution system 20 output from the voltmeters 61a, 61b and the ammeters 62a, 62b, and the voltage target value output from the first voltage target generation circuit 682, and notifies the CEMS 3 and the like of the information via the first communication interface circuit 65. The fourth control circuit 647 stores various information (control parameters related to drooping characteristics, power command values, voltage command values, control parameters of the first PI control circuit 644 and the second PI control circuit 648, etc.) notified from the CEMS 3 via the first communication interface circuit 65 in registers (not shown) and outputs them to each circuit.

[0078] Figure 9 is a block diagram illustrating the configuration of a second control circuit 94 that controls the first DC / DC conversion circuit 93 of the power conversion device 9 for a power distribution system battery shown in Figure 6. The second control circuit 94 includes a second power calculation circuit 941, a second voltage target generation circuit 942, a power target generation circuit 943, a second voltage target value control circuit 945, a power target value control circuit 946, a first switching circuit 947, a current limiting circuit 948, and a fifth control circuit 949.

[0079] The second power calculation circuit 941 calculates the charge and discharge power using the measured voltage of the DC distribution system 21 measured by the voltmeter 96 and the measured current of the DC distribution system 21 measured by the ammeter 97. The second voltage target generation circuit 942 generates a voltage target value based on the output of the second power calculation circuit 941 and the output of the voltmeter 96. The second voltage target generation circuit 942 has a drooping characteristic when the power converter 9 for the distribution system battery operates in voltage control mode. The power target generation circuit 943 generates a power target value based on the output of the second power calculation circuit 941 and the output of the voltmeter 96. The power target generation circuit 943 has a drooping characteristic when the power converter 9 for the distribution system battery operates in power control mode. The second voltage target value control circuit 945 generates a current command value to output to the first DC / DC converter 93 based on the voltage target value output from the second voltage target generation circuit 942. The power target value control circuit 946 generates a current command value to output to the first DC / DC conversion circuit 93 based on the power target value output from the power target generation circuit 943. The first switching circuit 947 switches the output of the second voltage target value control circuit 945 and the output of the power target value control circuit 946 using a control signal output from the fifth control circuit 949. The current limiting circuit 948 limits the current command value output from the first switching circuit 947 and applies PWM modulation before outputting it to the first DC / DC conversion circuit 93. The fifth control circuit 949 collects the output of the power distribution system battery 8 output from voltmeters 91, 96 and ammeters 92, 97, measurement results related to the DC power distribution system 21, the voltage target value output from the second voltage target generation circuit 942, and the power target value output from the power target generation circuit 943. The fifth control circuit 949 notifies the CEMS 3 and the like of the collected information via the second communication interface circuit 95. The fifth control circuit 949 stores various information (control parameters related to drooping characteristics, power command value, voltage command value, control parameters of the second voltage target value control circuit 945 and the power target value control circuit 946, etc.) notified from the CEMS 3 via the second communication interface circuit 95 in registers not shown and outputs them to each circuit.

[0080] Figure 10 is a block diagram illustrating the configuration of a third control circuit 134 that controls the second DC / DC conversion circuit 133 of the consumer PV power converter 13 shown in Figure 7.

[0081] The third control circuit 134 includes an MPPT (Maximum Power Point Tracking) control circuit 1341, a PV voltage control circuit 1342, a second switching circuit 1343, and a sixth control circuit 1344.

[0082] The MPPT control circuit 1341 searches for the maximum power point of the PV panel 12 in order to extract the maximum amount of power generated from the PV panel 12, based on the measured values ​​of the voltmeter 131 and the ammeter 132, for so-called maximum power point tracking control. Specifically, the MPPT control circuit 1341 generates a control command value for the second DC / DC conversion circuit 133 to control the DC voltage measured by the voltmeter 131 to the voltage corresponding to the maximum power point. The PV voltage control circuit 1342 generates a control command value for the second DC / DC conversion circuit 133 in order to maintain the DC voltage of the DC distribution system 21 (the fifth DC voltage) at a predetermined target voltage, based on the measured value of the voltmeter 136. The sixth control circuit 1344 outputs control parameters and control target values ​​to the MPPT control circuit 1341 and the PV voltage control circuit 1342, and also manages the power generation status of the PV panel 12. The sixth control circuit 1344 further outputs a control signal from the second switching circuit 1343. The second switching circuit 1343 selectively outputs one of the outputs of the MPPT control circuit 1341 and the PV voltage control circuit 1342 as a control command value for the third DC / DC conversion circuit 133, according to the control signal from the sixth control circuit 1344. The second DC / DC conversion circuit 133 is controlled in either MPPT mode or PV voltage control mode. In MPPT mode, the second switching circuit 1343 outputs a control command value generated by the MPPT control circuit 1341, and in PV voltage control mode, it outputs a control command value generated by the PV voltage control circuit 1342.

[0083] Next, the drooping characteristics adopted in Embodiment 1 will be described. In Embodiment 1, the DC / DC converter or AC / DC converter installed in the DC distribution system 21 is equipped with a virtual synchronous generator control (VSG (Virtual Synchronous Generator) control) mechanism that simulates the inertial force, synchronizing force, and braking force of a synchronous generator to the inverter equipment installed in the AC system. Below, the virtual synchronous generator control technology used in inverter equipment will be briefly described. Synchronous generators, such as those found in thermal power plants, have functions such as adjusting the output power according to the frequency (governor function), maintaining angular velocity (inertial force), synchronizing with the AC system voltage (synchronizing force), adjusting the voltage of the main system (AVR function: Automatic Voltage Regulator function), and continuing operation even when there is an instantaneous drop in the AC system voltage that occurs during a system fault. The 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: the governor function, a function that simulates a mass system model based on motion equations (dynamic characteristics of a rotating machine), and the AVR function.

[0084] Embodiment 1 describes a case in which a governor function and a function simulating a mass system model based on motion equations are implemented to provide inertial force and braking force to the DC power distribution system 21. The AVR function is not implemented in Embodiment 1. The governor function and the function simulating a mass system model based on motion equations will be described in detail below.

[0085] First, let's explain the governor function. In power plants, the governor controls the output of gas turbines and steam turbines in thermal or nuclear power plants, or the guide vanes of water turbines in hydroelectric power plants, thereby controlling the output power of the generator. In an AC power system, when demand exceeds supply, the frequency of the AC system voltage decreases. Thermal or hydroelectric generators capable of output control have their governors equipped with droop characteristics to increase the generated power when the frequency decreases. On the other hand, when supply exceeds demand, the frequency of the AC system voltage increases. Similarly, in this case, thermal or hydroelectric generators capable of output control have their governors equipped with droop characteristics to decrease the generated power when the frequency increases. The Institute of Electrical Engineers of Japan provides standard models of governors that perform this operation, such as models configured as first-order lag types.

[0086] In Embodiment 1, see equation (1) to describe the operation when the governor is approximated by a model configured with the above-described first-order lag system. 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).

[0087] -1 / (Kgd×(1+s×Tg))…(1) Next, we will explain the function that simulates a mass system model based on the motion equation. A synchronous generator has a generator rotor with a unit inertia constant M. For example, if the power generated by several hundred PV panels 12 decreases rapidly due to a sudden change in solar radiation, governor control cannot instantly compensate for the power shortage. A synchronous generator converts the rotational energy stored in the generator rotor into electricity and outputs it to the grid. At that time, the angular velocity (rotational speed) of the generator rotor decreases. When the angular velocity of the generator rotor decreases, the energy supplied by governor control increases, thereby supporting supply and demand. Equation (2) shows the motion determination equation that simulates a mass system model (generator rotor) (energy P is divided by angular velocity ω to convert it to torque T). In equation (2), Dg is the braking coefficient and M is the inertia constant mentioned above.

[0088] Tin - Tout = M × dω / dt + Dg × ω ... (2) Embodiment 1 describes a case in which the concepts of equations (1) and (2) (drooping characteristics) are used to control a DC / DC converter or AC / DC converter installed in the DC power distribution system 21, thereby simulating inertial force and braking force in the DC power distribution system 21.

[0089] This section describes a case where the static inverter (first AC / DC conversion circuit 63) is incorporated into the control of the synchronous generator to simulate the inertial force and braking force of the DC power distribution system 21. Embodiment 1 describes two types of control modes: a voltage control mode that gives the converter a power-voltage drooping characteristic (details will be described later, but refer to Figure 20) and a power control mode that gives it a voltage-power drooping characteristic (details will be described later, but refer to Figure 21).

[0090] The following describes a first voltage target generation circuit 682 or a second voltage target generation circuit 942 that operates in a voltage control mode that provides power-voltage drooping characteristics, using Figures 11 to 13. Figure 11 is a block diagram of the first voltage target generation circuit 682 (or the second voltage target generation circuit 942). In Figure 11, the first voltage target generation circuit 682 comprises a subtractor 6821 (9421), a first governor control circuit 6822 (9422), an adder 6823 (9423), a subtractor 6824 (9424), and a first point mass arithmetic circuit 6825 (9425).

[0091] The subtractor 6821 (9421) subtracts the voltage command value (Vref1) output by the fourth control circuit 647 (fifth control circuit 949) from the measured result of the voltmeter 66 (96). The output of the subtractor 6821 (9421) is input to the first governor control circuit 6822 (9422). The first governor control circuit 6822 (9422) outputs an offset value to be added to the power target value. The detailed operation of the first governor control circuit 6822 (9422) will be described later. The adder 6823 (9423) generates the control power target value of the first mass-point system calculation circuit 6825 (9425) by adding an offset value to be added to the power target value output by the first governor control circuit 6822 (9422) and the power command value (Pref1) output by the fourth control circuit 647 (fifth control circuit 949).

[0092] The subtractor 6824 (9424) subtracts the measured effective power output by the first power calculation circuit 681 (second power calculation circuit 941) from the control power target value output by the adder 6823 (9423). The output of the subtractor 6824 (9424) is input to the first mass system calculation circuit 6825 (9425). In Embodiment 1, the control parameters (speed adjustment rate Kgd, governor time constant Tg, inertia constant M, and braking coefficient Dg) of the first governor control circuit 6822 (9422) and the first mass system calculation circuit 6825 (9425) are output from the CEMS 3 and notified via the fourth control circuit 647 (fifth control circuit 949).

[0093] Figure 12 is a block diagram illustrating the configuration of the first governor control circuit 6822 (9422) shown in Figure 11. Since the configuration and operation of the first governor control circuit 9422 are the same as those of the first governor control circuit 6822, only the first governor control circuit 6822 will be described in the following explanation.

[0094] The first governor control circuit 6822 comprises a multiplier 68221, a first-order lag system model (denoted as 1 / (1+s×Tg1) in the figure) 68222, and a first limiter circuit 68223.

[0095] The multiplier 68221 multiplies the output of the subtractor 6821 by the proportional gain output by the fourth control circuit 647 (denoted as -1 / Kgd1 in the figure). The output of the multiplier 68221 is output to the first-order lag system model 68222. Embodiment 1 describes the case in which the governor control is performed using the first-order lag standard model presented by the Institute of Electrical Engineers of Japan. Therefore, the first-order lag system model 68222 implements the first-order lag system model (1 / (1+s×Tg1)) as shown in Figure 12. The first limiter circuit 68223 limits the output of the first-order lag system model 68222.

[0096] Figure 13 is a block diagram illustrating the configuration of the first mass-point system calculation circuit 6825 (9425) shown in Figure 11. Since the configuration and operation of the first mass-point system calculation circuit 9425 are the same as those of the first mass-point system calculation circuit 6825, only the first mass-point system calculation circuit 6825 will be described in the following explanation.

[0097] The first point mass arithmetic circuit 6825 includes a subtractor 68251, an integrator (indicated as 1 / (M1×s) in the figure) 68252, a multiplier 68253, and an adder 68254.

[0098] [Correction based on Rule 91 25.12.2025] Subtractor 68251 subtracts the output of multiplier 68253 from the output of subtractor 6824 (the result of subtracting the control power target value from the measured effective power). The subtraction result is input to integrator 68252. Integrator 68252 calculates the difference voltage between the voltage target value and the voltage command value (Vref1) by multiplying the output of subtractor 68251 by 1 / M1 and then integrating it. Adder 68254 generates the voltage target value by adding the output of integrator 68252 and the voltage command value (Vref1).

[0099] The transfer function of the motion equation portion of the first point mass system calculation circuit 6825 (9425) will be explained. The transfer function of the motion equation portion can be expressed as a first-order lag system (proportional gain: 1 / Dg_v, time constant: M_v / Dg_v) as shown in equation (3).

[0100] (1 / M_v × s) / (1 + Dg_v / M_v × (1 / s)) = (1 / Dg_v) × (1 / (1 + (M_v / Dg_v) × s) ... (3) In the virtual synchronous generator control unit, the governor time constant (Tg_v) and the point mass calculation unit time constant (M_v / Dg_v) are determined based on the response speed required for the system. In addition, in the first voltage target generation circuit 682 or the second voltage target generation circuit 942 shown in Figures 11 to 13, each coefficient corresponds to Tg1 = Tg_v, Kgd1 = Kgd_V, M1 = M_V, and Dg1 = Dg_V.

[0101] Similarly, a power target generation circuit 943 that operates in a power control mode that provides voltage-power droop characteristics will be described using Figures 14 to 16. Figure 14 is a block diagram of the power target generation circuit 943. The power target generation circuit 943 comprises a subtractor 9431, a second governor control circuit 9432, an adder 9433, a subtractor 9434, and a second point mass calculation circuit 9435.

[0102] [Correction based on Rule 91 25.12.2025] The subtractor 9431 subtracts the power command value (Pref2) output by the fifth control circuit 949 from the measured effective power output by the second power calculation circuit 941. The output of the subtractor 9431 is input to the second governor control circuit 9432. The second governor control circuit 9432 outputs an offset value to be added to the voltage target value. The detailed operation of the second governor control circuit 9432 will be described later. The adder 9433 generates the control voltage target value for the second mass system calculation circuit 9435 by adding the offset value to be added to the voltage target value output by the second governor control circuit 9432 and the voltage command value (Vref2) output by the fifth control circuit 949.

[0103] The subtractor 9434 subtracts the measured voltage output by the voltmeter 96 from the control voltage target value output by the adder 9433. The output of the subtractor 9434 is input to the second mass-point system calculation circuit 9435. In Embodiment 1, the control parameters (speed adjustment ratio Kgd, governor time constant Tg, inertia constant M, and braking coefficient Dg) of the second governor control circuit 9432 and the second mass-point system calculation circuit 9435 are output from the CEMS 3 and notified via the fifth control circuit 949.

[0104] Figure 15 is a block diagram illustrating the configuration of the second governor control circuit 9432 shown in Figure 14. The second governor control circuit 9432 comprises a multiplier 94321, a first-order lag system model (denoted as 1 / (1+s×Tg1) in the figure) 94322, and a second limiter circuit 94323.

[0105] The multiplier 94321 multiplies the output of the subtractor 9431 by the proportional gain output by the fifth control circuit 949 (denoted as -1 / Kgd2 in the figure). The output of the multiplier 94321 is output to the first-order lag system model 94322. Embodiment 1 describes the case in which the governor control is performed using the first-order lag standard model presented by the Institute of Electrical Engineers of Japan. Therefore, the first-order lag system model 94322 implements the first-order lag system model (1 / (1+s×Tg2)) as shown in Figure 15. The second limiter circuit 94323 limits the output of the first-order lag system model 94322.

[0106] Figure 16 is a block diagram illustrating the configuration of the second point mass arithmetic circuit 9435 shown in Figure 14. The second point mass arithmetic circuit 9435 includes a subtractor 94351, an integrator (indicated as 1 / (M2×s) in the figure) 94352, a multiplier 95353, and an adder 94354.

[0107] The subtractor 95351 subtracts the output of the multiplier 94353 from the output of the subtractor 9434 (the result of subtracting the target control voltage value from the measured voltage). The subtraction result is input to the integrator 94352. The integrator 94352 calculates the difference in power between the target power value and the power command value (Pref2) by multiplying the output of the subtractor 94351 by 1 / M2 and then integrating it. The adder 94354 generates the target power value by adding the output of the integrator 94352 and the power command value (Pref2). The multiplier 94353 multiplies the output of the integrator 94352 by the damping coefficient Dg2.

[0108] The transfer function of the motion equation portion of the second mass system calculation circuit 9435 can be expressed as shown in equation (3), as explained in the power control mode. Similarly to the above, in equation (3), the transfer function of the motion equation portion can be expressed as a first-order lag system (proportional gain: 1 / Dg_v, time constant: M_v / Dg_v). In the virtual synchronous generator control unit, the governor time constant (Tg_v) and the mass system calculation unit time constant (M_v / Dg_v) are determined based on the response speed required for the system. In addition, in the power target generation circuit 943 shown in Figures 14 to 16, each coefficient corresponds to Tg2 = Tg_v, Kgd2 = Kgd_V, M2 = M_V, and Dg2 = Dg_V.

[0109] Figure 17(a) is a block diagram shown for calculating the transfer function F(s) of the first voltage target generation circuit 682 or the second voltage target generation circuit 942 shown in Figure 11. The transfer function F(s) (ΔV / ΔP) of the block diagram shown in Figure 17(a) can be expressed by equation (4).

[0110]

[0111] Therefore, by the final value theorem, equation (5) holds in the steady state.

[0112]

[0113] Equation (5) corresponds to the slope of the drooping characteristic of the virtual synchronous generator control unit (1 / (Dg_v + 1 / Kgd_v)). The transfer function F(s) of the power target generation circuit 943 shown in Figure 14 (see Figure 17(b)) is not explained in detail, but the slope of the drooping characteristic calculated from the transfer function F(s) is (1 / (Dg_p + 1 / Kgd_p)) from equation (6).

[0114]

[0115] Figure 18 is a block diagram illustrating the configuration of the second voltage target control circuit 945 shown in Figure 9. The second voltage target control circuit 945 comprises a subtractor 9451 and a third PI control circuit 9452.

[0116] The subtractor 9451 subtracts the measured voltage value measured by the voltmeter 96 from the voltage target value output by the second voltage target generation circuit 942 and outputs the result to the third PI control circuit 9452. The third PI control circuit 9452 performs PI control so that the output of the subtractor 9451 becomes zero. The output of the third PI control circuit 9452 is output to the first switching circuit 947 as a control command for the first DC / DC conversion circuit 93.

[0117] Figure 19 is a block diagram illustrating the configuration of the power target value control circuit 946 shown in Figure 9. The power target value control circuit 946 comprises a subtractor 9461 and a fourth PI control circuit 9462. The subtractor 9461 subtracts the measured power calculation result calculated by the second power calculation circuit 941 from the power target value output by the power target generation circuit 943 and outputs it to the fourth PI control circuit 9462. The fourth PI control circuit 9462 performs PI control so that the output of the subtractor 9461 becomes zero. The output of the fourth PI control circuit 9462 is output to the first switching circuit 947 as a control command for the first DC / DC conversion circuit 93.

[0118] Next, an overview of the operation of Embodiment 1 will be described using Figures 20 to 24. Figure 20 is a diagram showing an example of the drooping characteristics of the first voltage target generation circuit 682 or the second voltage target generation circuit 942 in Embodiment 1. Figure 21 is a diagram showing an example of the drooping characteristics of the power target generation circuit 943 in Embodiment 1. In Embodiment 1, the drooping characteristics implemented in the AC / DC converter 6 and the power conversion devices 9a to 9n for the power distribution system battery are defined by the slope of the characteristics when the power output by each converter is divided by the capacity of each converter to obtain a PU, and the DC voltage output by each converter is divided by the reference voltage of the DC power distribution system 21 (1500V in Embodiment 1) to obtain a PU. In the figures, Pmax is the maximum discharge power with the converter capacity, and -Pmax(Pmin) is similarly the maximum charge power with the converter capacity. Vmax is the maximum value within a predetermined range of the DC power distribution system 21, and Vmin is the minimum value within a predetermined range of the DC power distribution system 21. In Embodiment 1, the predetermined voltage range of the DC power distribution system 21 is ±10% of the reference voltage of the DC power distribution system 21 (1350V to 1650V). In the figure, Vrang_max is the upper limit of the predetermined voltage range, and Vrang_min is the lower limit of the predetermined voltage range.

[0119] Figure 22 is a diagram illustrating the operating principle of Embodiment 1. As shown in Figure 22, four customer load groups 10a to 10d are connected to the DC distribution system 21. Similarly, power converters 9a to 9d for distribution system batteries are connected to the DC distribution system 21. Consider the case where the demand power (current) of customer load group 10 increases by ΔIdem_x (where x is a to d), and the AC / DC converter 6 supplies Δiacdc (=ΔI_a + ΔI_b + ΔI_c + ΔI_d) for the proportion of the increased demand power (current), and each power converter 9x for distribution system batteries supplies ΔIbat_x (where x is a to d). In such a case, when the power converters 9a to 9d for distribution system batteries are converted to PU, they are given the same slope (identical) drooping characteristics (see the dashed line of the drooping characteristics in the lower part of Figure 22). In conventional control, as shown in Figure 22, the fluctuation range of the interconnection point voltage between each power converter 9 for distribution system batteries and the DC distribution system 21 increases as you move towards the end of the power flow (power converter 9d for distribution system batteries). Therefore, in conventional control (when the drooping characteristics are the same), the amount of differential power allocated to the power converter 9 for distribution system batteries becomes larger as you move towards the end of the power flow.

[0120] The reason for this is that when the power demand of customer load groups 10a to 10d changes and the differential power is distributed among the outputs of the AC / DC converter 6 and the power converters 9 for each distribution system battery, the conventional control does not take into account the fluctuation range of the interconnection point voltage of each converter in the DC distribution system 21 due to the change in power demand. Specifically, it does not take into account changes in power flow current and voltage drops in the DC distribution system 21 due to distribution system impedances 7a to 7d. Therefore, if each converter (AC / DC converter 6 and each power converter 9 for distribution system batteries) has the same drooping characteristics, as shown in Figure 22, the more downstream the converter (power converter 9d for distribution system batteries in this figure) is located in the power flow, the larger the voltage fluctuation range will be, and more power will be distributed compared to other converters (in Figure 22, when the change in power demand is positive (insufficient supply), the power (current) output from each power converter 9 for distribution system batteries will be ΔIbat_d > ΔIbat_c > ΔIbat_b > ΔIbat_a). Note that in the figure, "A⇒B" indicates that A is the current value before the change in power demand, and B is the current value after the change in power demand.

[0121] On the other hand, in Embodiment 1, as shown in the lower part of Figure 22 (see the drooping characteristic of the solid line), the voltage fluctuation range at the connection point of each power converter 9 for distribution system batteries with the DC distribution system 21 in response to demand fluctuations is estimated in advance based on the estimation result of the voltage fluctuation range at the connection point of each power converter 9 for distribution system batteries with the DC distribution system 21, and the slope of the drooping characteristic of each power converter 9 for distribution system batteries is determined considering the estimated fluctuation range. This makes it possible to control the power converter 9 so that the apportionment amount of differential power output by each power converter 9 is approximately the same. Specifically, even if the voltage curve of the DC distribution system 21 shown in the middle of Figure 22 falls to the voltage below the dashed line due to insufficient power demand, if the drooping characteristic of each converter is the solid line drooping characteristic shown in the lower part of Figure 22 according to Embodiment 1, then even if the DC voltage fluctuation at the interconnection point of each power converter 9 for the DC distribution system 21 is that of a converter on the power flow end side (power converter 9d for the distribution system battery), the drooping characteristic is provided such that the output power in response to the DC voltage change is smaller compared to a converter located upstream (so that the allocated power of each power converter 9 for the distribution system battery is approximately equal), thus suppressing the allocated power of the converter on the power flow end side.

[0122] The following describes the method for generating drooping characteristics, including the voltage command value (Vref) and power command value (Pref), in Embodiment 1. In Embodiment 1, the CEMS 3 first creates the power command value (Pref) for the power converters 9a to 9n for the distribution system battery. As will be described in detail later, the operation plan creation circuit 34 shown in Figure 2 generates the power command value (Pref) based on the supply and demand plan notified by the DSO 2, the supply and demand forecast results for the customer load groups 10a to 10n (predicted from the power generation forecast of the PV panel 12 and the power consumption forecast results of the customer load 11), and the battery capacity of the distribution system batteries 8a to 8n, SOC information, etc. Specifically, the operation plan creation circuit 34 allocates the charge and discharge power so that the difference power between the supply and demand plan and the demand power consumption of each customer load group 10 (the difference between the power consumption of the customer load 11 and the power generated by the PV panel 12) is supplied from the power converters 9a to 9n for the distribution system battery. In Embodiment 1, when allocating charge and discharge power, the power is allocated based on the battery capacity and SOC information so that the distribution system batteries 8a to 8n reach zero charge or full charge almost simultaneously. The AC / DC converter 6 allocates power based on the supply and demand plan notified by the DSO2.

[0123] CEMS3 predicts the power flow current through the DC distribution system 21 based on the power allocation amount of the AC / DC converter 6, the power allocation amount of the distribution system batteries 8a to 8n (power converters 9a to 9n for distribution system batteries), and the above supply and demand forecast. CEMS3 pre-estimates the impedance 7a to 7n of the DC distribution system 21 based on the measurement results of voltage and current notified from the AC / DC converter 6, the customer load groups 10a to 10n, and the power converters 9a to 9n for distribution system batteries. Based on the estimated distribution system impedance information and the current flow forecast results, CEMS3 estimates the interconnection point voltage of each power converter 9 for distribution system batteries with the DC distribution system 21 and checks whether the interconnection point voltage falls within a predetermined range.

[0124] If even one interconnection point voltage for a power converter 9 for a power distribution system battery is not entered, CEMS3 will regenerate the power allocation for all power converters 9 for power distribution systems batteries. If all of the estimated interconnection point voltages for each power converter 9 for power distribution systems batteries are within a predetermined range, CEMS3 will generate the power allocation assigned to each power converter 9 as a power command value (Pref) and the estimated interconnection point voltage as a voltage command value (Vref).

[0125] Once the power command value (Pref) and voltage command value (Vref) for each power converter 9 for distribution system batteries have been generated, the CEMS 3 estimates the voltage fluctuation range of the interconnection point voltage between each power converter 9 for distribution system batteries and the DC distribution system 21 when a demand fluctuation occurs. At that time, the CEMS 3 calculates the allocated (proportionalized) power of the excess or deficit power generated by the demand fluctuation to each converter (AC / DC converter 6 and each power converter 9 for distribution system batteries). Based on the estimated voltage fluctuation range of the interconnection point voltage between each power converter 9 for distribution system batteries and the DC distribution system 21, and the amount of power proportionalized at that time, the CEMS 3 generates the slope of the drooping characteristic applied to the AC / DC converter 6 and each power converter 9 for distribution system batteries. As described above, by generating the drooping characteristics of each converter, power distribution does not concentrate on the converters located at the end of the power flow even when the power demand fluctuates, and the SOC information of each distribution system battery 8 can be properly managed and operated.

[0126] Next, the operation of the power converter management device of Embodiment 1 will be explained using Figures 1 to 35. Referring again to Figure 1, the distribution system to which the power converter management device according to Embodiment 1 is connected will be explained. In Embodiment 1, the AC distribution system 20a, which is connected to the main power system (not shown) via the substation 1, is connected to the AC / DC converter 6 via the switch 5. The AC / DC converter 6 converts the three-phase AC voltage input from the AC distribution system 20b into a DC voltage and outputs it to the DC distribution system 21. The DC voltage output from the AC / DC converter 6 is input to the power converter 9a for the distribution system battery, the customer load group 10a, and the distribution system impedance 7b via the distribution system impedance 7a (DC distribution system 21a). The customer load group 10 includes a customer load 11 and a power converter 13 for customer PV. In Embodiment 1, the consumer load 11 is assumed to be connected to multiple consumers (for example, approximately 50 to 150 general consumers (single-family homes)). The consumer PV power converter 13 is assumed to be installed by multiple consumers within the consumer load group 10 and connected to the DC distribution system 21.

[0127] In Embodiment 1, the DC power distribution system 21 comprises a set of n power distribution system impedances 7 connected in series, a power converter 9 for the power distribution system battery, and a group of customer loads 10.

[0128] The distribution automation system (DSO2), CEMS3, weather forecast server4, power converters 9a to 9n for distribution system batteries, customer loads 11a to 11n within the customer load group 10 (each customer load consists of multiple customers, and all customers are connected to the communication line 22 via smart meters, etc., which are not shown), and power converters 13a to 13n for customer PVs are connected via the communication line 22. In Embodiment 1, at least one of the second voltage target generation circuit 942 and the power target generation circuit 943 is implemented in the power converters 9a to 9n for distribution system batteries, providing a pseudo-inertial force to the DC distribution system 21.

[0129] This section describes the operation of a system that supports the DC distribution system 21 with power supplied from substation 1, power generated by PV panels 12a to 12n, and charge / discharge power output from distribution system batteries 8a to 8n. Figure 25 is a diagram showing the sequence of normal operation of the power converter management device (CEMS3) centered on the CEMS3 shown in Figure 1. As shown in Figure 25, steady-state processing consists of two processes: processing performed in 30-minute cycles and processing performed in 5-minute cycles. The respective processing cycles are not limited to 30 minutes and 5 minutes; the 30-minute cycle may be 1 hour or 15 minutes. The 5-minute cycle may be 1 minute or 30 seconds. When the 30-minute cycle processing starts in Figure 25, DSO2 outputs a request to CEMS3 for output of collected measurement data via the communication line 22. When CEMS3 receives a request from DSO2, it sends an output request for measurement data, etc., to each connected device to collect measurement data and status information (such as the SOC (State of Charge) and SOH (State of Health) of the distribution system battery 8) from the AC / DC converter 6, the power conversion devices 9a to 9n for the distribution system battery, and the customer load groups 10a to 10n, and then collects the measurement data, etc. CEMS3 calculates the power consumption of each customer load group 10, the power generated by the PV panels 12, and the charge / discharge power of the distribution system battery 8 over a 30-minute period by combining the 25-minute data collected at 5-minute intervals, and transmits these to DSO2 along with the SOC information and SOH information of the distribution system battery 8. In Embodiment 1, consumers within the demand load group 10 measure the maximum (actual) and minimum (actual) values ​​of their demand power (PV power generation power minus load power consumption) over a 5-minute period until they receive a request for output of measurement data, and output the measurement results. CEMS 3 calculates the maximum supply-demand power difference value by subtracting the predicted supply-demand power within the consumer load group 10 (PV power generation power prediction result minus load power consumption prediction result) predicted during operation planning from the maximum supply-demand amount within each consumer load group 10, and the minimum supply-demand power difference value by subtracting the predicted supply-demand power within the consumer load group 10 (PV power generation power prediction result minus load power consumption prediction result) predicted during operation planning from the predicted supply-demand power within the consumer load group 10.CEMS3 builds a database based on the date, time, day of the week, and actual weather conditions (in Embodiment 1, the database is built within the power consumption prediction database 352 shown in Figure 3, which will be described later). At the same time, CEMS3 also stores the maximum (actual) and minimum (actual) values ​​of power demand measured by each customer load group 10 over a 30-minute period.

[0130] Upon receiving the measurement results, DSO2 creates a 24-hour, 30-minute cycle demand plan (total power supplied to the AC distribution system 20 (DC distribution system 21) via substation 1 in 30 minutes) necessary for creating an operation plan for the distribution system batteries 8a to 8n, and notifies CEMS3 of the results. Upon receiving the above information used to create the battery operation plan, CEMS31 generates an operation plan for the distribution system battery 8, control parameters (power command value (Pref) and voltage command value (Vref), etc.), and droop characteristics for the AC / DC conversion circuit 6 and each distribution system battery power converter 9, based on the previously collected SOC information, SOH information, power generation forecast information for PV panels 12a to 12n (details described later), and consumer demand forecast information (details described later). The method for creating the operation plan and control parameters, and the method for generating the droop characteristics will be described later. Once the operation plan, control parameters, and droop characteristics for the distribution system battery 8 have been created, the CEMS 3 transmits the operation plan, control parameters, and droop characteristics to the AC / DC converter 6 and the power converters 9a to 9n for the distribution system battery, and then terminates the 30-minute cycle processing.

[0131] CEMS3 collects measurement data from the AC / DC converter 6, the power conversion devices 9a to 9n for the distribution system battery, and the customer load groups 10a to 10n at 5-minute intervals. At the same time, CEMS3 also collects the measurement results of the maximum and minimum values ​​of the demand power (power obtained by subtracting the load power consumption from the PV generation power). Smart meters installed in each customer (not shown) clear the measured maximum and minimum values ​​and start measuring again. Based on the collected results, CEMS3 checks the difference between the power command value (Pref) and the actual charging and discharging power, or the measured voltage of the DC distribution system 21. In Embodiment 1, the CEMS 3 recalculates the operation plan (power target value (command value)) if the difference between the power command value (Pref) and the measured power value deviates from a predetermined range, if the measured voltage of the DC distribution system 21 deviates from a predetermined range, if the SOC of the distribution system battery 8 exceeds a predetermined value during charging, or if the SOC of the distribution system battery 8 is discharged below a predetermined value. The CEMS 3 notifies the AC / DC converter 6 and each power converter 9 for the distribution system batteries of the recalculation result. The specific recalculation process will be described later.

[0132] Next, the detailed operation of CEMS3 will be explained using Figure 26. Figure 26 is a control processing flowchart of CEMS3 shown in Figure 1. In Figure 26, once processing begins, at S100, CEMS3 starts estimating the system impedance. Figure 27 is a flowchart of the system impedance estimation at S100.

[0133] When the estimation of system impedance begins, in S1001, the operation plan creation unit management circuit 346 shown in Figure 3 within the operation plan creation circuit 34 shown in Figure 2 checks with the distributed power management unit control circuit 36 ​​shown in Figure 2 whether measurement data has been received from each customer load group 10, each power converter 9 for distribution system batteries, and AC / DC converter 6 after starting up the CEMS 3. If data has not been received, the process proceeds to S1002.

[0134] [Correction based on Rule 91 25.12.2025] In S1002, the operation plan creation unit management circuit 346 sets the initial value of the pre-set system impedance (notifies the system impedance estimation circuit 350 in Figure 3), and terminates the system impedance estimation flowchart of S100. If the answer in S1001 is YES, the process proceeds to S1003.

[0135] In S1003, the operation plan creation unit management circuit 346 checks whether the collection of new measurement data from each device (each customer load group 10, each power converter 9 for distribution system batteries, and AC / DC converter 6) has been completed. If the data has not been collected (if the answer is NO in S1003), the system impedance estimation flowchart in S100 is terminated.

[0136] On the other hand, if data has been collected (if S1003 is YES), the process proceeds to S1004. In S1004, the operation plan creation unit management circuit 346 selects a distribution system section between the AC / DC converter 6 and the converter one downstream (power converter for distribution system battery 9). In S1005, the operation plan creation unit management circuit 346 collects voltage and current information for each converter in the selected distribution system section, as well as demand power information for each customer load group. In S1006, the operation plan creation unit management circuit 346 calculates the power flow current flowing through the selected section based on the measured voltage, current, and power values ​​collected by the power flow current estimation circuit 347. In S1007, the operation plan creation unit management circuit 346 instructs the system impedance estimation circuit 350 to estimate the impedance. Upon receiving the instruction, the system impedance estimation circuit 350 estimates the impedance based on the voltage difference (measured result) and power flow current between the two selected converters. In S1008, the operation plan creation unit management circuit 346 reads the impedance estimation result for the selected distribution system section from the impedance database (not shown), corrects the impedance estimation result using the current estimation result and the impedance estimation result stored in the database, and stores the corrected result in the database (reconstructs the database). In S1009, the operation plan creation unit management circuit 346 checks whether the impedance estimation for all target distribution system sections has been completed. If it has been completed (YES), the impedance estimation process in S100 is completed. If it has not been completed (NO in S1009), the process proceeds to S1010. In S1010, the next distribution system section is selected. After that, the process returns to S1005.

[0137] When S100 is completed, in S101, the operation plan creation unit management circuit 346 checks whether or not there has been a request for output of measurement data from DSO2. If there is a request for output, the process proceeds to S102. In S102, the operation plan creation unit management circuit 346 collects the latest measurement information by transmitting a request for output of measurement data to the AC / DC converter 6, the power conversion devices 9a to 9n for the distribution system battery, and the customer load groups 10a to 10n via the communication line 22. The operation plan creation unit management circuit 346 temporarily stores the collected measurement information in the storage circuit 32 via the communication circuit 31. At the same time, the operation plan creation unit management circuit 346 updates the power generation prediction database 351 for PV panels 12a to 12n and the power consumption prediction database 352 for customer loads 11a to 11n within the operation plan creation circuit 34 using the collected measurement data. At that time, the operation plan creation unit management circuit 346 calculates the maximum supply-demand power difference value by subtracting the supply-demand power forecast (PV power forecast result minus load power consumption forecast result) within the customer load group 10 from the maximum value (actual measurement) of the demand power (PV power generation power minus load power consumption) within the customer load group 10 over a 5-minute period, and the minimum supply-demand power difference value by subtracting the supply-demand power forecast (PV power generation power forecast result minus load power consumption forecast result) within the customer load group 10 from the minimum value (actual measurement) of the supply-demand power (PV power generation power forecast result minus load power consumption forecast result) within the customer load group 10 over a 5-minute period. The operation plan creation unit management circuit 346 stores the largest maximum supply-demand power difference value measured over the previous 25 minutes and the smallest minimum supply-demand power difference value measured over the previous 25 minutes in a database constructed according to the date, time, day of the week, actual weather, etc. In Embodiment 1, the maximum and minimum power supply / demand difference values ​​for each customer load group 10 are stored in the power consumption prediction database 352. At the same time, the maximum (measured) and minimum (measured) power demand values ​​for each customer load group 10 are also stored in the power consumption prediction database 352 along with the maximum and minimum power supply / demand difference values. Since the details of how to construct the database for the maximum and minimum power supply / demand difference values ​​are not the main subject of this application, a detailed explanation is omitted.

[0138] In S103, the operation plan creation unit management circuit 346 calculates the amount of power generated by each customer load group (the amount of power consumed by each customer) 10a to 10n, the PV panels 12a to 12n, and the amount of power charged and discharged by the distribution system batteries 8a to 8n over a 30-minute period, based on the collected measurement data and the 25-minute data collected at 5-minute intervals stored in the memory circuit 32. The operation plan creation unit management circuit 346 transmits the calculated amount of power generated and the amount of power charged and discharged, along with the SOC information and SOH information of the distribution system batteries 8a to 8n, to the DSO2 via the communication circuit 31.

[0139] In Embodiment 1, once the transmission of measurement data is complete, the storage circuit 32 erases the measurement data collected over the 30-minute period. If the transmission of measurement data in S103 is completed, or if the answer in S101 is NO, the process proceeds to S104. In S104, the operation plan creation unit management circuit 346 checks whether or not it has received a demand plan notification from DSO2. If it has been received, the process proceeds to S105, and the operation plan creation unit management circuit 346 performs operation plan creation 1. In Embodiment 1, DSO2 notifies the CEMS 3 of the power supply and demand plan for the power supplied from the main grid to the DC distribution system 21 in 30-minute cycles for 24 hours.

[0140] Figure 28 is a detailed operation flowchart of operation plan creation 1 in S105 shown in Figure 26. In Figure 28, when operation plan creation 1 is started, in S1051, power generation prediction for PV panels 12a to 12n is performed. When the distributed power management control circuit 36 ​​shown in Figures 2 and 3 receives a demand plan (battery operation plan) notification from DSO2, it instructs the operation plan creation control circuit 346 in the operation plan creation circuit 34 to create an operation plan. Upon receiving the instruction, the operation plan creation control circuit 346 instructs the power generation prediction circuit 342 via the battery operation plan generation circuit 341 to predict the power generated by PV panels 12a to 12n. Upon receiving the instruction, the power generation prediction circuit 342 obtains a 24-hour weather forecast from the weather forecast server 4 via the communication line 22. The power generation prediction circuit 342 uses the obtained results and data from the power generation prediction database 351 managed by the power generation prediction circuit 342 to predict the power generation for 24 hours. Specifically, the power generation prediction circuit 342 predicts the amount of power generated by each of the PV panels 12a to 12n based on time information (not shown) and weather forecast information obtained from the weather forecast server 4. In Embodiment 1, since the supply and demand plan for the DC distribution system 21 notified by the DSO2 is notified in 30-minute cycles for 24 hours, the power generation prediction database 351 is constructed based on the actual power generation data, weather data, and time information (year, month, day, and time information) of the PV panels 12a to 12n collected over a 30-minute period. The details of how the power generation prediction database 351 is constructed are not the main subject of this application, so a detailed explanation is omitted.

[0141] In Figure 28, once the power generation forecast for PV panels 12a to 12n is completed in S1051, the power consumption of customer loads 11a to 11n is predicted in S1052. In Figure 3, the operation plan creation management circuit 346 receives the power generation forecast results for PV panels 12a to 12n from the power generation forecast circuit 342 and instructs the power consumption forecast circuit 343 via the battery operation plan generation circuit 341 to predict the power consumption of customer loads 11a to 11n. Upon receiving the instruction, the power consumption forecast circuit 343 uses data from the power consumption forecast database 352 managed by the power consumption forecast circuit 343 to predict the power consumption of customer loads 11a to 11n for 24 hours. Similar to the power generation forecast database 351, the power consumption forecast database is constructed based on the power consumption of customer loads 11a to 11n collected over 30 minutes, using date, day of the week, time information, and weather information. Since the method of constructing the database is not the main subject of this application, a detailed explanation will be omitted.

[0142] In S1052 of Figure 28, once the power consumption prediction for the customer load group 10a to 10n is complete, the creation of the demand plan begins in S1053. Upon receiving the power consumption prediction results for customer loads 11a to 11n from the power consumption prediction circuit 343 in Figure 3, the battery operation plan generation circuit 341 in the operation plan creation circuit 34 calculates the total charge and discharge power of the distribution system batteries 8a to 8n every 30 minutes based on the power generation prediction results for PV panels 12a to 12n from the power generation prediction circuit 342, the power consumption prediction results for customer loads 11a to 11n from the power consumption prediction circuit 343, and the demand plan notified from DSO2 (as mentioned above, in Embodiment 1, the 24-hour power supply plan (30-minute power supply plan) planned for the DC distribution system 21 below substation 1).

[0143] Once the demand plan is created in S1053 in Figure 28, the calculation of the charge and discharge power of the distribution system batteries 8a to 8n is performed in S1054. Specifically, the battery operation plan generation circuit 341 in Figures 2 and 3 determines (allocates) the charge and discharge power from each battery every 30 minutes based on the SOC information of the distribution system batteries 8a to 8n and the battery capacity of the distribution system batteries 8a to 8n, which are collected in the memory circuit 32 via the communication circuit 31. In Embodiment 1, when creating a 24-hour battery operation plan, the battery operation plan generation circuit 341 formulates an operation plan such that the SOC of the distribution system batteries 8a to 8n is almost simultaneously zero, almost simultaneously fully charged, or all distribution system batteries 8 are still in a charge and discharge state after 24 hours. This is done for the following reasons. For example, if the charging power of the distribution system batteries 8a and 8b becomes zero, the power generated by the PV panels 12a and 12b, and the power supplied from the DC distribution system 21 will be supplied to the customer loads 11a and 11b. In this case, the other distribution system batteries 8c to 8n will supply the insufficient power within the customer load group 10c to 10n, so power from the AC / DC converter 6 will be supplied to the customer load group 10a and 10b. As a result, the power supplied from the DC distribution system 21 to the customer load group 10a and 10b (Idc_a and Idc_b) will increase, causing a larger voltage drop at the distribution system impedances 7a and 7b, which can cause the voltage at the grid connection point between the distribution system batteries 8a to 8n and the DC distribution system 21 to drop, potentially exceeding the predetermined voltage range. On the other hand, if the distribution system batteries 8a to 8n are operating, each distribution system battery 8 covers the decrease in power generated by the PV panels 12 within each customer load group 10, thus preventing the voltage at the grid connection point between the distribution system battery power converters 9a to 9n and the DC distribution system 21 from dropping unnecessarily and deviating from the predetermined voltage range. Therefore, when the CEMS 3 creates an operation plan for the distribution system batteries 8a to 8n, it is desirable to create an operation plan such that the distribution system batteries 8a to 8n reach zero SOC or full charge almost simultaneously.

[0144] The detailed operation of the power distribution system battery charge / discharge power (power command value) formulation 1 in S1054 will be explained below using Figure 29. When the flowchart for power distribution system battery charge / discharge power (power command value) formulation 1 is started, in S10541, the operation plan creation unit management circuit 346 within the operation plan creation circuit 34 instructs the battery operation plan generation circuit 341 to generate power command values ​​for each power conversion device 9a to 9n for the power distribution system battery. When the battery operation plan generation circuit 341 receives the operation plan creation instruction from the operation plan creation unit management circuit 346, it instructs the power generation prediction circuit 342 and the power consumption prediction circuit 343 to predict the amount of power generated by the PV panels 12a to 12n and the amount of power consumed by the loads in the customer load group 10a to 10n.

[0145] When the power generation prediction circuit 342 receives an instruction from the battery operation plan generation circuit 341 to perform power generation prediction for PV panels 12a to 12n, it uses the storage circuit 32 to receive weather forecast information from the weather forecast server 4 and the date and time information and day of the week information output from the time information generation unit in the operation plan creation circuit 34 (not shown) to predict the amount of power generated by each PV panel 12 using the power generation prediction database 351. While details are omitted, the power generation prediction database 351 calculates the power generated by each PV panel 12 over a 30-minute period, collected through 5-minute and 30-minute cycle processing, and updates the data in the power generation prediction database 351 based on the calculated power generation results, date and time information, day of the week information, and weather performance information. Similarly, when the power consumption prediction circuit 343 receives an instruction from the battery operation plan generation circuit 341 to perform power consumption prediction for the consumer loads 11a to 11n within the consumer load group 10a to 10n, the memory circuit 32 predicts the power consumption of each consumer load 11 using the power consumption prediction database 352 based on weather forecast information (including temperature information) received from the weather forecast server 4, date and time information and day of the week information output from the time information generation unit in the operation plan creation circuit 34 (not shown). Although details are omitted, the power consumption prediction database 352 calculates the 30-minute power consumption of each consumer load 11 collected in 5-minute cycle processing and 30-minute cycle processing, and updates the data in the power consumption prediction database 352 based on the power consumption calculation results, date and time, day of the week information and weather performance information.

[0146] In S10542, the battery operation plan generation circuit 341 collects status information (SOC information in Embodiment 1) of the distribution system batteries 8a to 8n. In S10543, the battery operation plan generation circuit 341 calculates the demand (difference) power of each consumer load group 10 based on the power generation prediction results of each PV panel 12 and the power consumption prediction results of the consumer load 11 collected in S10541.

[0147] In S10544, the battery operation plan generation circuit 341 allocates the demand power from the AC / DC converter 6 (demand plan notified by DSO2) to each customer load group 10 based on the SOC and battery capacity information of the distribution system battery 8 and the converter capacity information of the power converter device 9 for the distribution system battery. Specifically, in Embodiment 1, the battery operation plan generation circuit 341 allocates the demand power from the AC / DC converter 6 so that the SOC of each distribution system battery 8 after 30 minutes is approximately the same, based on the difference (surplus / deficit) power calculated in S10543 and the SOC information of the distribution system battery 8. Specifically, the battery operation plan generation circuit 341 calculates the surplus / deficit power within each customer load group 10 by (predicted power consumption of customer load 11 - predicted power generation result of PV panel 12). At that time, the battery operation plan generation circuit 341 allocates the power supply planned in the supply and demand plan notified by the DSO2 according to the size of the SOC of the distribution system battery 8. Simultaneously, the battery operation plan generation circuit 341 also generates a power command value (Pref) for the AC / DC converter 6. Specifically, the battery operation plan generation circuit 341 uses the power supply planned in the supply and demand plan notified by the DSO2 as the power command value (Pref).

[0148] In S10545, the battery operation plan generation circuit 341 creates a power command value to be notified to each power conversion device 9 for the distribution system batteries. Specifically, the battery operation plan generation circuit 341 calculates the power command value by subtracting the demand power allocated in S10544 from the difference (surplus / deficit) power calculated in S10543.

[0149] In S10546, the battery operation plan generation circuit 341 checks whether the charge / discharge power (power command value) calculated in S10545 exceeds the capacity of the first DC / DC converter 93 in the power converter 9 for distribution system batteries. If it exceeds the capacity (NO), the process returns to S10544, and the demand power from the AC / DC converter 6 is reallocated. If it does not exceed the capacity (YES), the process proceeds to S10547. In S10547, the battery operation plan generation circuit 341 checks whether it has generated power command values ​​(Pref) for all power converters 9 for distribution system batteries.

[0150] If not all power commands have been generated (NO), the process returns to S10545, and the power command value (Pref) for the next power converter 9 for the distribution system battery is generated. If the generation of power command values ​​(Pref) for all power converter 9 for the distribution system battery has been completed (YES), the battery operation plan generation circuit 341 notifies the operation plan creation unit management circuit 346 of this fact.

[0151] In S1055, the operation plan creation management circuit 346 within the operation plan creation circuit 34 instructs the power flow current estimation circuit 347 to output the impedance estimation result of the DC distribution system 21 estimated in S100. Upon receiving the instruction, the system impedance estimation circuit 350 outputs the distribution system impedance estimation result to the power flow current estimation circuit 347. As described above, the impedance estimation method of the system impedance estimation circuit 350 will be briefly explained. The system impedance estimation circuit 350 calculates the power flow current flowing through the distribution system impedances 7a to 7n based on the voltage measurement information of the interconnection points of the DC distribution system 21 of the AC / DC converter 6 and each distribution system battery power converter 9a to 9n received in 30-minute cycle processing and 5-minute cycle processing, the output power measurement results of the AC / DC converter 6 and each distribution system battery power converter 9a to 9n, the power consumption of the consumer load 11 in the consumer load group 10, and the measurement results of the power generated by the PV panel 12. The system impedance estimation circuit 350 estimates the values ​​of the distribution system impedances 7a to 7n based on the output power measurement results of the AC / DC converter 6 and each power conversion device 9a to 9n for the distribution system battery, and the calculation results of the power flow. The estimation results are merged with the distribution system impedance estimation results stored in a database (not shown) and stored in the database as new data.

[0152] More specifically, this will be briefly explained using Figure 22. The system impedance estimation circuit 350 calculates the distribution system impedance 7a (= (Vdc_0 - Vdc_a) / Iacdc) from the measured values ​​of the output voltage (Vdc_0) and current (Iacdc) of the AC / DC conversion circuit 6 and the measured value of the interconnection point voltage (Vbat_a) of the power conversion device 9a for the distribution system battery with the DC distribution system 21. The system impedance estimation circuit 350 reads the distribution system impedance 7a from a distribution system impedance estimation database (not shown) and modifies the distribution system impedance 7a read from the distribution system impedance estimation database by combining it with the calculation result above. In Embodiment 1, the modified distribution system impedance 7 is calculated as "Modified distribution system impedance 7 = 0.999 × Distribution system impedance 7 read from the distribution system impedance estimation database + 0.001 × Calculated distribution system impedance 7". However, the calculation method is not limited to the above. Next, the method for calculating the distribution system impedance 7b one level downstream will be explained. Specifically, the system impedance estimation circuit 350 calculates the excess or deficit power within the customer load group 10a (measured result of customer load 11 - measured result of power generation of PV panel 12), and subtracts the measured output power of the power converter 9a for distribution system batteries from the calculation result. The system impedance estimation circuit 350 calculates I_a in Figure 22 by dividing the subtraction result by the measured value of the interconnection point voltage (Vbat_a) of the power converter 9a for distribution system batteries with the DC distribution system 21. The system impedance estimation circuit 350 uses the above calculation result to find the current (Iacdc - I_a) flowing through the distribution system impedance 7b, and calculates the distribution system impedance 7b using the same procedure as for finding the distribution system impedance 7a described above. Note that the method for constructing the database for distribution system impedance estimation is not a major topic of this application, so further explanation will be omitted.

[0153] In S1055, once the reading of the estimated distribution system impedances 7a to 7n is complete, the process proceeds to S1056. In S1056, the power flow current estimation circuit 347 calculates the power flow current within the DC distribution system 21. Specifically, the power flow current estimation circuit 347 calculates the power flowing through each distribution system impedance 7a to 7n based on the estimated surplus and deficit power for each customer load group 10 calculated in S1054, the charge and discharge power (Pref) from each distribution system battery power converter 9, and the demand power (Pref) supplied from the AC / DC converter 6. The power flow current estimation circuit 347 calculates the current value I using the power calculation result W and the impedance estimate value R read out in S1055 by the formula (W = V × I = R × I × I).

[0154] In S1057, the power flow current estimation circuit 347 predicts the voltage value at the interconnection point of each power converter 9 for distribution system batteries in the DC distribution system 21. The following describes how to perform the voltage value prediction 1 at each receiving point in S1057 using Figure 30. Figure 30 is a flowchart for estimating the voltage value at the interconnection point of each power converter 9 for distribution system batteries in the DC distribution system 21.

[0155] In Figure 30, when S1057 is started, in S10571, the power flow current estimation circuit 347 reads the droop characteristic information of the AC / DC converter 6 from the memory circuit 32 via the operation plan creation unit management circuit 346. In S10572, the power flow current estimation circuit 347 reads the power command value information (Pref) of the AC / DC converter 6 from the operation plan creation unit management circuit 346. In S10573, the power flow current estimation circuit 347 reads the output DC voltage value (voltage command value) of the AC / DC converter 6. In Embodiment 1, the output voltage (voltage command value) of the AC / DC converter 6 is set to the reference voltage (1500V). In S10574, the power flow current estimation circuit 347 selects the power converter 9a for the distribution system battery one downstream of the AC / DC converter 6. In S10575, the power flow current estimation circuit 347 collects droop characteristic information of the first DC / DC conversion circuit 93 in the selected power conversion device 9 for the power distribution system battery.

[0156] Before describing the flowchart in Figure 30, the two types of droop characteristics of the first DC / DC conversion circuit 93 in the power conversion device 9 for distribution system batteries described above in Embodiment 1 will be explained. Figure 20 shows an example of the droop characteristics of the first DC / DC conversion circuit 93 operating in voltage control mode. Figure 21 shows an example of the droop characteristics of the first DC / DC conversion circuit 93 operating in power control mode. Figures 11 to 13 are block diagrams of the second voltage target generation circuit 942 operating in voltage control mode, which is implemented in the second control circuit 94 in the power conversion device 9 for distribution system batteries. The first voltage target generation circuit 682 in the AC / DC converter 6 has a similar circuit configuration in voltage control mode. Similarly, Figures 14 to 16 are block diagrams of the power target generation circuit 943 operating in power control mode, which is implemented in the second control circuit 94 in the power conversion device 9 for distribution system batteries.

[0157] The characteristics of the voltage control mode and power control mode will be explained below using Figures 20, 21, 23, and 24. First, the voltage control mode will be explained. In the voltage control mode, the first DC / DC conversion circuit 93 (the second voltage target generation circuit 942 in the second control circuit 94) in the power converter 9 for the power distribution system battery controls the target value of the DC voltage of the DC power distribution system 21. Specifically, the first DC / DC conversion circuit 93 compares the DC voltage of the DC power distribution system 21 with the voltage command value (Vref), and if the DC voltage of the DC power distribution system 21 is low, it determines that the amount of power supplied is low and increases the discharge power of the power distribution system battery 8 (or decreases the charging power during charging). At that time, the first DC / DC conversion circuit 93 lowers the DC voltage of the DC power distribution system 21 output by the first DC / DC conversion circuit 93 according to the drooping characteristic shown in Figure 20. On the other hand, the first DC / DC conversion circuit 93 compares the DC voltage of the DC power distribution system 21 with the voltage command value (Vref). If the DC voltage of the DC power distribution system 21 is high, it determines that power is being supplied in excess and reduces the discharge power of the power distribution system battery 8 (or increases the charging power during charging). At that time, the first DC / DC conversion circuit 93 increases the DC voltage of the DC power distribution system 21 output by the first DC / DC conversion circuit 93 according to the drooping characteristic shown in Figure 20.

[0158] As described above, in voltage control mode, the first DC / DC converter 93 controls the voltage at the interconnection point of the DC power distribution system 21 based on the drooping characteristic shown in Figure 20, based on the power being charged and discharged. Therefore, when the load fluctuates or the amount of power generated by the PV panel 12 fluctuates, the first DC / DC converter 93, which operates in voltage control mode, first supplies the excess or insufficient power to the DC power distribution system 21. At that time, the first DC / DC converter 93 controls the voltage of the DC power distribution system 21 based on the implemented drooping characteristic.

[0159] The characteristics of the voltage control mode are described below. In voltage control mode, the power converter 9 for distribution system batteries manages the interconnection point voltage of the DC distribution system 21, and as described above, it can detect load fluctuations or fluctuations in the amount of power generated by the PV panels 12. In voltage control mode, if multiple power converters 9 for distribution system batteries are connected to the DC distribution system 21, the (transient) response changes depending on the magnitude of the distribution system impedance 7 from the point where the load fluctuation or the amount of power generated by the PV panels 12 occurs to the power converter 9 for distribution system batteries operating in voltage control mode. Specifically, differential power is preferentially supplied from the power converter 9 for distribution system batteries with the smallest distribution system impedance 7 up to the point where the load fluctuation or the amount of power generated occurs. Figure 23 is a diagram showing the response waveform when the consumer load 11 in the consumer load group 10a changes in a step-like manner in the DC distribution system 21 shown in Figure 22. For the sake of simplicity, we will assume that the customer load groups 10b to 10d and the power converters 9b to 9d for the distribution system battery are stopped. In this case, the power converter 9a for the distribution system battery is connected to the customer load group 10a with an impedance of "zero", and the AC / DC converter 6 (operating in voltage control mode) is connected to the customer load group 10a via the distribution system impedance 7a. As a result, as shown in Figure 23, all of the differential power is supplied from the first DC / DC converter circuit 93 in the power converter 9a for the distribution system battery (see dashed line in the figure). Subsequently, the AC / DC converter 6, operating in voltage control mode, supplies power based on its implemented drooping characteristics. Finally, in the example shown in Figure 23 (where the first DC / DC converter circuit 93 in the power converter 9a for the distribution system battery and the AC / DC converter 6 have the same drooping characteristics), the power increased due to load fluctuations is distributed between the first DC / DC converter circuit 93 and the AC / DC converter 6 in the power converter 9a for the distribution system battery.

[0160] Next, the power control mode will be explained. As described above, in the power control mode, the first DC / DC conversion circuit 93 controls the charging and discharging power of the distribution system battery 8 according to the DC voltage at the interconnection point of the DC distribution system 21. Therefore, unlike the voltage control mode, it is not possible to detect load fluctuations or fluctuations in the amount of power generated by the PV panel 12. Therefore, when load fluctuations occur, the power converter 9 or AC / DC converter 6 for the distribution system battery, which operates in voltage control mode, first supplies the differential power to the load and controls the DC voltage of the DC distribution system 21 that is managed (output) according to the supplied differential power (determining the management voltage based on the drooping characteristic). As a result, the DC voltage of the DC distribution system 21 changes, and the first DC / DC conversion circuit 93 in the power converter 9 for the distribution system battery in power control mode controls the charging and discharging power based on the drooping characteristic shown in Figure 21.

[0161] The characteristics of the power control mode are described below. In power control mode, the charging and discharging power is controlled according to the interconnection point voltage of the DC distribution system 21. Therefore, the DC distribution system 21 cannot be constructed using only distributed power sources that operate in power control mode. At least one distributed power source that operates in voltage control mode to manage the DC voltage of the DC distribution system 21 is required. If the power converter for the distribution system battery or AC / DC converter 6 operating in voltage control mode is managing the DC voltage of the DC distribution system 21, when load fluctuations or fluctuations in the power generated by the PV panels 12 occur, the power converter for the distribution system battery or AC / DC converter 6 operating in voltage control mode will supply excess power (differential power) as described above, and will manage (output) the DC voltage of the DC distribution system 21 based on the drooping characteristic. The power converter for the distribution system battery operating in power control mode controls the charging and discharging power of the distribution system battery 8 based on the interconnection point voltage of the DC distribution system 21. Figure 24 shows the response waveform when the customer load 11 within the customer load group 10a changes in a step-like manner in the DC distribution system 21 shown in Figure 22. For simplicity of explanation, it is assumed that the customer load groups 10b to 10d and the power converters 9b to 9d for the distribution system battery are stopped. The AC / DC converter 6 operates in voltage control mode, and the power converter 9a for the distribution system battery operates in power control mode. As shown in Figure 24, when a load fluctuation occurs, the AC / DC converter 6 (operating in voltage control mode) first supplies excess power (differential power) and controls the DC voltage of the DC distribution system 21 based on the drooping characteristic (see solid line in the figure). As a result, the interconnection point voltage of the DC distribution system 21 for the power converter 9a for the distribution system battery decreases, and the power converter 9a for the distribution system battery increases the discharge amount based on the drooping characteristic.

[0162] In voltage control mode, in addition to the features described above, if the DC voltage of the DC distribution system 21 falls outside the voltage range covered by the drooping characteristic, overcurrents may occur, potentially causing the power converter to shut down. On the other hand, in power control mode, even if the DC voltage of the DC distribution system 21 falls outside the voltage range covered by the drooping characteristic, the charging and discharging power is fixed at the maximum charging and discharging power (converter capacity), allowing operation to continue. The method of constructing the DC distribution system 21 using voltage control mode and power control mode is not a major topic of this application, so further explanation is omitted.

[0163] In S10575 of Figure 30, once the collection of droop characteristic information for the first DC / DC conversion circuit 93 in the selected power conversion device 9 for the distribution system battery is complete, the process proceeds to S10576. In S10576, the power flow current estimation circuit 347 acquires power command value (Pref) information to be notified to the first DC / DC conversion circuit 93 in the selected power conversion device 9 for the distribution system battery. In S10577, the power flow current estimation circuit 347 estimates the power flow current and outputs the estimation result to the system voltage estimation circuit 348. In S10577, the system voltage estimation circuit 348 calculates the voltage drop value based on the power flow current estimation result. In S10578, the system voltage estimation circuit 348 calculates the interconnection point voltage between the selected DC / DC converter 93 in the power converter 9 for the power distribution system battery and the DC distribution system 21, and outputs the calculation result to the operation plan creation unit management circuit 346. In S10579, the operation plan creation unit management circuit 346 uses the interconnection point voltage with the DC distribution system 21 and the drooping characteristics calculated in S10578 to calculate the charge / discharge power output from the first DC / DC converter 93 in the power converter 9 for the power distribution system battery. Based on the calculated charge / discharge power, the operation plan creation unit management circuit 346 applies a correction to the power flow current calculation result of the DC distribution system 21. In Embodiment 1, when creating an operation plan, the voltage command value is generated so that the interconnection point voltage of each converter with the DC distribution system 21 becomes the voltage command value, so no correction is necessary.

[0164] In S10580, the operation plan creation unit management circuit 346 checks whether the estimation of the output voltage of the first DC / DC conversion circuit 93 in all power conversion devices 9 for distribution system batteries has been completed. If all checks are not completed (NO), the process proceeds to S10581. In S10581, the operation plan creation unit management circuit 346 selects the first DC / DC conversion circuit 93 in the power conversion device 9 for distribution system batteries that is connected downstream of the selected power conversion device 9 for distribution system batteries. After that, the process returns to S10575. If all checks are completed (YES), the operation plan creation unit management circuit 346 terminates S1057.

[0165] When S1057 in Figure 28 is completed, the process proceeds to S1058. In S1058, the operation plan creation unit management circuit 346 generates the grid connection point voltage of each power converter 9 for distribution system batteries estimated in S1057 as a voltage command value (Vref). In S1059, the operation plan creation unit management circuit 346 checks whether the estimated values ​​of the connection point voltages (receiving point voltages) of all power converters 9 for distribution system batteries with the DC distribution system 21 estimated in S1057 fall within a predetermined range. Embodiment 1 describes a case where the voltage range of the DC distribution system 21 is, for example, a reference voltage (1500V) ± 0.1 × reference voltage, and the predetermined range is, for example, a reference voltage ± 0.075 × reference voltage (2.5% is a margin in case of load fluctuations, etc.). Note that the predetermined voltage range is set to be narrower than the voltage range of the DC distribution system 21. This is a measure to give the DC power distribution system 21 inertia force by the drooping characteristic shown in Figure 20 or Figure 21 when a fluctuation in demand power occurs. (As shown in Figure 20 or Figure 21, the upper limit voltage is Vrange_max and the lower limit voltage is Vrange_min). If NO is given in S1059, then in S1060, the charging and discharging power 1 of the power distribution system battery 8 is reviewed.

[0166] Figure 31 is a flowchart of the review of the charging and discharging power of the distribution system battery 8 in S1060. When S1060 is started, in S10601 the operation plan creation unit management circuit 346 extracts the distribution system battery power converters 9 whose estimated interconnection point voltage (receiving point voltage) with the DC distribution system 21, estimated in S1057, falls outside a predetermined range. In S10602 the operation plan creation unit management circuit 346 determines whether the interconnection point voltage (receiving point voltage) of the distribution system battery power converters 9 that deviated from the predetermined range is on the lower voltage side (less than Vrange_min). If it deviated to the lower voltage side (less than Vrange_min) (if YES in S10602), the process proceeds to S10603. In S10603, the operation plan creation unit management circuit 346 selects the power converter 9 for the distribution system battery (power converter 9a for the distribution system battery) connected downstream of the AC / DC converter 6. In S10604, the operation plan creation unit management circuit 346 collects the power command value (Pref) of the selected power converter 9 for the distribution system battery.

[0167] Embodiment 1 describes a case where the power command value is changed to respond when the interconnection point voltage (receiving point voltage) deviates from a predetermined range. Therefore, if the interconnection point voltage (receiving point voltage) falls to the lower limit of the predetermined voltage range, the operation plan creation unit management circuit 346 determines that there is a large current (power) flowing forward through the DC distribution system 21 and increases the value of the power command to each distribution system battery power converter 9 (increases the discharge power or decreases the charging power). On the other hand, if the interconnection point voltage (receiving point voltage) falls to the upper limit, the operation plan creation unit management circuit 346 determines that there is a small current (power) flowing forward through the DC distribution system 21 (or a large reverse current) and decreases the value of the power command to each distribution system battery power converter 9 (decreases the discharge power or increases the charging power).

[0168] Once the collection of power command values ​​(Pref) for the selected power distribution system battery power converter 9 is complete, in S10605, the operation plan creation unit management circuit 346 checks whether the power supply connection point (receiving point) voltage of the selected power distribution system battery power converter 9 has deviated from a predetermined voltage range. If the power supply connection point (receiving point) voltage has deviated from a predetermined voltage range (YES in S10605), the process proceeds to S10606. In S10606, the operation plan creation unit management circuit 346 adds a constant α to the power command value (Pref) collected in S10604 (Pref = Pref + α). If the power supply connection point (receiving point) voltage has not deviated from a predetermined voltage range (NO in S10605), the process proceeds to S10607. In S10607, the operation plan creation unit management circuit 346 adds a constant β to the power command value (Pref) collected in S10604 (Pref = Pref + β). In Embodiment 1, α > β. The amount of correction to the power command value of the power converter 9 for the distribution system battery when the grid connection point (receiving point) voltage deviates from the lower limit voltage of a predetermined voltage range is increased to suppress the incoming power flow.

[0169] [Correction based on Rule 91 25.12.2025] When processing S10606 or S10607 is completed, the process proceeds to S10608. In S10608, the operation plan creation unit management circuit 346 checks whether the corrected power command value exceeds the converter capacity (maximum output power: Pmax) of the first DC / DC conversion circuit 93 in the power conversion device 9 for the distribution system battery. If it exceeds the limit (NO), the process proceeds to S10609. In S10609, the operation plan creation unit management circuit 346 changes the power command value (Pref) to Pmax. On the other hand, if it does not exceed the limit (YES), the process proceeds. If the answer in S10608 is YES, or if processing in S10609 is completed, the process proceeds to S10610. In S10610, the operation plan creation unit management circuit 346 checks whether all power command values ​​have been modified for the first DC / DC conversion circuit 93 in the power conversion device 9 for the distribution system battery. If all power command values ​​have not been modified (NO in S10610), the process proceeds to S10611. In S10611, the operation plan creation unit management circuit 346 selects the power conversion device 9 downstream of the selected power conversion device 9 for the distribution system battery. After that, the process returns to S10604.

[0170] On the other hand, if the answer in S10602 is NO (i.e., the reverse power is large), the process proceeds to S10613. In S10613, the operation plan creation unit management circuit 346 selects the power converter 9 for the distribution system battery (power converter 9a for the distribution system battery) connected downstream of the AC / DC converter 6. In S10614, the operation plan creation unit management circuit 346 collects the power command value (Pref) of the selected power converter 9 for the distribution system battery.

[0171] Once the collection of the power command value (Pref) for the selected power distribution system battery power converter 9 is complete, the process proceeds to S10615. In S10615, the operation plan creation unit management circuit 346 checks whether the power supply connection point (receiving point) voltage of the selected power distribution system battery power converter 9 has deviated from a predetermined voltage range. If the answer in S10615 is YES, the process proceeds to S10616. In S10616, the operation plan creation unit management circuit 346 subtracts a constant γ from the power command value (Pref) collected in S10614 (Pref = Pref - γ). If the answer in S10615 is NO, the process proceeds to S10617. In S10617, the operation plan creation unit management circuit 346 subtracts a constant ε from the power command value (Pref) collected in S10614 (Pref = Pref - ε). In Embodiment 1, γ > ε. The amount of correction to the power command value of the power converter 9 for the distribution system battery when the grid connection point (receiving point) voltage deviates from a predetermined upper limit voltage range is increased to suppress the incoming power flow.

[0172] When processing in S10616 or S10617 is completed, the process proceeds to S10618. In S10618, the operation plan creation unit management circuit 346 checks whether the corrected power command value exceeds the converter capacity (maximum charging power that can be charged: Pmin) of the first DC / DC conversion circuit 93 in the power conversion device 9 for the distribution system battery. If it exceeds the limit (NO), the process proceeds to S10619. In S10619, the operation plan creation unit management circuit 346 changes the power command value (Pref) to Pmin. On the other hand, if it does not exceed the limit (YES), the process proceeds. If the answer in S10618 is YES, or if processing in S10619 is completed, the process proceeds to S10620. In S10620, the operation plan creation unit management circuit 346 checks whether all power command values ​​have been modified for the first DC / DC conversion circuit 93 in the power conversion device 9 for the distribution system battery. If the answer in S10620 is NO, the process proceeds to S10621. In S10621, the operation plan creation unit management circuit 346 selects the power conversion device 9 downstream of the selected power conversion device 9 for the distribution system battery. After that, the process returns to S10614.

[0173] If, in S10610 or S10620, the power command values ​​have been corrected for all first DC / DC conversion circuits 93 (YES), the process proceeds to S10612. In S10612, the operation plan creation unit management circuit 346 generates a power command value (Pref) for the AC / DC converter 6 based on the corrected power command values ​​of each power converter 9 for distribution system batteries, the predicted power consumption results of each customer load 11 in each customer load group 10, and the predicted power generation results of the PV panels 12. Specifically, the operation plan creation unit management circuit 346 calculates the power command value (Pref) for the AC / DC converter 6 by subtracting the total predicted power generation results of the PV panels 12 from the total predicted power consumption values ​​of each customer load 11, and then subtracting the total corrected power command values ​​of each power converter 9 for distribution system batteries. In Embodiment 1, the power converter 9 for the distribution system battery was controlled to apply a larger offset to devices whose grid connection point (receiving point) voltage deviated compared to those that did not deviate, but this is not the only method. For example, the amount of offset to be applied may be determined based on the magnitude of the SOC of the distribution system battery 8 (a larger offset value may be applied to devices with a large SOC. Alternatively, a larger offset value may be applied to power converter 9 for the distribution system battery that is closer to the input side of the power current. Alternatively, the distance between the power converter 9 for the distribution system battery and the AC / DC converter 6 (magnitude of the distribution system impedance 7) may be used). Alternatively, the amount of offset to be applied may be determined by the connection position of the power converter 9 for the distribution system battery or the direction of the power current flow. Similar effects can be achieved in these cases as well.

[0174] When step S1060 in Figure 28 is completed, the process returns to S1056. The operation plan creation unit management circuit 346 continues processing. On the other hand, if the answer to S1059 is YES, the operation plan creation unit management circuit 346 considers that the creation of the voltage command value (Pref) is complete and proceeds to S1061.

[0175] Figure 32 is a flowchart of the drooping characteristic generation 1 in S1061. When the drooping characteristic generation 1 flowchart is started, in S106101, the distributed power management control circuit 36 ​​(see Figure 2) in the CEMS 3 instructs the control parameter generation circuit 33 to generate the drooping characteristics for each converter. Upon receiving the instruction, the power flow current fluctuation range estimation circuit 331 (see Figure 4) in the control parameter generation circuit 33 collects the calculation results of the power flow currents flowing through each distribution system impedance 7 calculated in S1056.

[0176] In S106102, the demand power fluctuation prediction circuit 332 collects the power generation and power consumption prediction results for each consumer PV. In S106103, the demand power fluctuation prediction circuit 332 predicts the demand fluctuation for each consumer load group 10. Specifically, the demand power fluctuation prediction circuit 332 instructs the operation plan creation unit management circuit 346 in the operation plan creation circuit 34 to read the demand fluctuation range prediction information stored in the power consumption prediction database 352. When the operation plan creation unit management circuit 346 receives the instruction to read the demand fluctuation range prediction information, it reads the demand power fluctuation range information (maximum value (measured) or maximum supply-demand power difference value, and minimum value (measured) or minimum supply-demand power difference value) for each consumer load group 10 stored in the power consumption prediction database 352 based on the date, day of the week, time, and weather forecast information for the target time period, and outputs it to the demand power fluctuation prediction circuit 332.

[0177] When the demand power fluctuation prediction circuit 332 receives demand power fluctuation range information (maximum supply-demand power difference value and minimum supply-demand power difference value) (ends S106103), the process proceeds to S106104. In S106104, when a demand power fluctuation occurs in each customer load group 10, the demand power fluctuation prediction circuit 332 allocates the difference power generated by the demand power fluctuation to each converter. Specifically, in Embodiment 1, the demand power fluctuation prediction circuit 332 distributes the power based on the ratio of the power command values ​​(Pref) notified to each converter. Regarding the allocation of the difference power to each converter, the demand power fluctuation prediction circuit 332 may allocate the power based on the SOC information of the distribution system battery 8 (in the case of discharge, batteries with larger SOCs are allocated more discharge power), or it may allocate a larger amount to the distribution system battery 8 that has not deteriorated as much based on the SOH information, or it may distribute the power based on the ratio of the converter capacities of each converter.

[0178] When the control parameter generation circuit 33 completes the allocation of differential power by the demand power fluctuation prediction circuit 332, the process proceeds to S106105. In S106105, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current flowing through each distribution system impedance 7 (the fluctuation range of the system connection point voltage with the DC distribution system 21 for each converter, and the fluctuation range of the output power). Specifically, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current based on the voltage and current (power) command values ​​notified to each converter, the power flow current flowing through each distribution system impedance 7 collected in S106101, the estimated result of the connection point voltage with the DC distribution system 21 for each converter, and the estimated system impedance result estimated in S100. Specifically, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current flowing through each distribution system impedance 7 based on the calculation results of the power flow current flowing through each distribution system impedance 7 calculated in S1056, the power demand forecast results for each customer load group 10 calculated from the power generation forecast results and power consumption forecast results for each customer collected in S106102, the power demand fluctuation forecast results for each customer load group 10 predicted in S106103, the differential power allocation results for each converter allocated in S106104, and the power command value (Pref) of each converter. More specifically, the differential value of the power flow current flowing through the distribution system impedance 7a is calculated by dividing the differential power allocated to the AC / DC converter 6 by the voltage command value (Vref). Similarly, the distribution system impedance 7x (where x is a to n) is calculated by subtracting the currents flowing to the customer load group 10x-1 and the power converter for the distribution system battery 9x-1 from the power current flowing through the preceding distribution system impedance 7x-1 (for example, distribution system impedance 7a when calculating the difference in power current of the distribution system impedance 7b). More specifically, the power current fluctuation range estimation circuit 331 subtracts the difference in power allocated to the power converter for the distribution system battery 9x-1 from the fluctuation in the demand power of the customer load group 10x-1, and divides the subtraction result by the voltage command value (Vref) of the power converter for the distribution system battery 9x-1. This estimates (calculates) the difference in power current flowing through the distribution system impedance 7x.Once the estimation of the differential current is complete, the power flow current fluctuation range estimation circuit 331 calculates the power flow current flowing through each distribution system impedance 7 based on the estimation results. That is, the power flow current fluctuation range estimation circuit 331 adds the difference value of the power flow current estimated in S106105 to the power flow current flowing through each distribution system impedance 7 collected in S106101. In Embodiment 1, the power flow current fluctuation range estimation circuit 331 estimates the power flow current fluctuation range based on the demand fluctuation range prediction result predicted in S106103 and the differential power information of each converter assigned in S106104. Specifically, when maximum demand (or minimum demand) occurs, the power flow current is calculated by subtracting the differential current supplied from each converter (the differential current is calculated as differential power / converter interconnection point voltage) from the demand fluctuation range prediction result (power flow current prediction result flowing through the distribution system) as described above. Then, the range of tidal current fluctuations is estimated from the calculated tidal current and the predicted tidal current surplus results when creating or revising the operation plan.

[0179] When S106105 is completed, in S106106, the droop characteristic slope determination circuit 333 calculates the slope of the droop characteristic of each converter. In Embodiment 1, the droop characteristic of the AC / DC converter 6 is the same as that of conventional control as shown in Figure 22. Specifically, in Embodiment 1, the droop characteristic slope determination circuit 333 sets the voltage command value (Vref) to 1500V, and determines the droop characteristic so that Vrang_max is the minimum demand power value notified from DSO2 and Vrang_min is the minimum demand power value notified from DSO2. The droop characteristic slope determination circuit 333 determines the slope of the droop characteristic by selecting the one with the gentler slope from the following two lines: the straight line connecting the minimum demand power value notified by DSO2, Vrang_max, and the straight line connecting the minimum demand power value notified by DSO2, Vrang_min, and the straight line connecting the maximum demand power value notified by DSO2, Vrang_min, and the straight line connecting the maximum demand power value notified by DSO2, Vrang_min, and the straight line connecting the maximum demand power value notified by DSO2, Vrang_min, and the straight line connecting the maximum demand power value notified by DSO2, Vrang_min, and the straight line with the gentler slope.

[0180] Once the drooping characteristics of the AC / DC converter 6 are determined, the drooping characteristic slope determination circuit 333 calculates the slope of the drooping characteristics of the power converter 9a for the distribution system battery, which is located one downstream of the AC / DC converter 6. In the following description, it is assumed that the power converters 9a and 9b for the distribution system battery operate in voltage control mode. Specifically, the drooping characteristic slope determination circuit 333 calculates the voltage (upper and lower limits) of the AC / DC converter 6 when it outputs the differential power (maximum and minimum values) allocated to the AC / DC converter 6, based on the drooping characteristics of the AC / DC converter 6. Next, the drooping characteristic slope determination circuit 333 estimates the voltage (upper and lower limits) of the power converter 9a for the distribution system battery based on the power current flowing through the distribution system impedance 7a, the impedance value of the distribution system impedance 7a, and the output voltage of the AC / DC converter 6. The droop characteristic slope determination circuit 333 determines the slope of the droop characteristic of the power converter 9a for the power distribution system battery by determining the slope of the straight line connecting (the difference power (maximum value) allocated to the power converter 9a for the power distribution system battery in S106104, and the voltage estimation result of the power converter 9a for the power distribution system battery (lower voltage limit)) and (the difference power (minimum value) allocated to the power converter 9a for the power distribution system battery in S106104, and the voltage estimation result of the power converter 9a for the power distribution system battery (upper voltage limit)). If this straight line does not pass through (power command value (Pref), voltage command value (Vref)) of the power converter 9a for the power distribution system battery, the droop characteristic slope determination circuit 333 determines the slope of the straight line passing through (the differential power (maximum value) allocated to the power converter 9a for the power distribution system battery in S106104, the estimated voltage result of the power converter 9a for the power distribution system battery (lower voltage limit)) and (power command value (Pref), voltage command value (Vref)), and the slope of the straight line passing through (the differential power (minimum value) allocated to the power converter 9a for the power distribution system battery in S106104, the estimated voltage result of the power converter 9a for the power distribution system battery (upper voltage limit)) and (power command value (Pref), voltage command value (Vref)), and the one with the gentler slope is taken as the slope of the droop characteristic of the power converter 9a for the power distribution system battery.Similarly, the droop characteristic slope determination circuit 333 estimates the voltage (upper and lower limit voltage) of the power converter 9b for the power distribution system battery based on the power current flowing through the power distribution system impedance 7b, the impedance value of the power distribution system impedance 7b, and the output voltage of the power converter 9a for the power distribution system battery. The droop characteristic slope determination circuit 333 then determines the slope of the droop characteristic of the power converter 9b by determining the slope of the straight line connecting (the difference power allocated to the power converter 9b for the power distribution system battery in S106104 (maximum value) and the estimated voltage result of the power converter 9b for the power distribution system battery (lower limit voltage)) and (the difference power allocated to the power converter 9b for the power distribution system battery in S106104 (minimum value) and the estimated voltage result of the power converter 9a for the power distribution system battery (upper limit voltage)). If this straight line does not pass through (power command value (Pref), voltage command value (Vref)) of the power converter 9b for the power distribution system battery, the droop characteristic slope determination circuit 333 determines the slope of the straight line passing through (the differential power (maximum value) allocated to the power converter 9b for the power distribution system battery in S106104, the estimated voltage result of the power converter 9b for the power distribution system battery (lower voltage limit)) and (power command value (Pref), voltage command value (Vref)), and the slope of the straight line passing through (the differential power (minimum value) allocated to the power converter 9b for the power distribution system battery in S106104, the estimated voltage result of the power converter 9b for the power distribution system battery (upper voltage limit)) and (power command value (Pref), voltage command value (Vref)), and the one with the gentler slope is taken as the slope of the droop characteristic of the power converter 9b for the power distribution system battery. The above operations are carried out until the slope of the power converter 9n for the distribution system battery is calculated. Note that when the power converter 9x for the distribution system battery is operating in power control mode, the X-axis (horizontal axis) and Y-axis (vertical axis) are reversed compared to the voltage control mode, as shown in Figure 21, so the slope can be calculated by reversing the X and Y coordinates as described above.

[0181] When S106106 is completed, in S106107, the droop characteristic generation circuit 334 generates the droop characteristics for each converter. In Embodiment 1, the droop characteristic generation circuit 334 uses the control mode of each converter and the slope of the droop characteristics calculated in S106106 to calculate the damping coefficient Dg using the above-described equation (5) (voltage control mode) or equation (6) (power control mode). In Embodiment 1, the speed adjustment ratio Kgd, governor time constant Tg, and inertia constant M are not changed. In Embodiment 1, only the damping coefficient Dg is changed, but it is not limited to this. For example, the droop characteristic generation circuit 334 may change the speed adjustment ratio Kgd based on equation (5) (voltage control mode) or equation (6) (power control mode), or change the damping coefficient Dg and the speed adjustment ratio Kgd, and further control the circuit to change the inertia constant M (such as so that M / Dg remains constant) in accordance with the change in the damping coefficient Dg.

[0182] When S106107 (S1061) is completed, the control parameter generation circuit 33 notifies the distributed power management unit control circuit 36 ​​of this fact. Upon receiving the notification, the distributed power management unit control circuit 36 ​​notifies the operation plan creation circuit 34. The operation plan creation circuit 34 completes operation plan creation 1 in S105.

[0183] Once the operation plan creation in S105 of Figure 26 is completed, the operation plan creation unit management circuit 346 sends the drooping characteristics (parameters), voltage command value (Vref), and power command value (Pref) created in S110 to the AC / DC converter 6 and the power conversion devices 9a to 9n for the power distribution system battery.

[0184] On the other hand, if a request for operation plan creation (24-hour supply and demand plan) has not been received from DSO2 in S104 (NO), the process proceeds to S106. In S106, the operation plan creation circuit 34 checks whether the current time is the time for collecting various measurement results (whether to start the 5-minute cycle processing). If it is not the collection time (NO), the process returns to S100. On the other hand, if it is the collection time (YES), the process proceeds to S107. In S107, the operation plan creation circuit 34 instructs the transmission data generation circuit 35 to generate a measurement data output request packet to transmit measurement data to the equipment connected to the DC distribution system 21 (AC / DC converter 6, power converters for distribution system batteries 9a to 9n, customer loads 11a to 11n, and power converters for customer PV 13a to 13n). When the transmission data generation circuit 35 receives a request to generate a measurement data output request packet, it generates a measurement data output request packet to be sent to each connected device and outputs the generated measurement data output request packet to the communication circuit 31. At the same time, the transmission data generation circuit 35 notifies the operation plan creation circuit 34 and the distributed power management unit control circuit 36 ​​that it has output the measurement data output request packet to the communication circuit 31. When the distributed power management unit control circuit 36 ​​receives the output notification of the measurement data output request packet from the transmission data generation circuit 35, it instructs the communication circuit 31 to transmit the input measurement data output request packet to the communication line 22. When the communication circuit 31 receives this instruction, it transmits the measurement data output request packet from the transmission data generation circuit 35 and waits until the measurement data is received. When the communication circuit 31 receives the measurement data, it stores the measurement data in the storage circuit 32 and notifies the distributed power management unit control circuit 36 ​​that the measurement data has been received. Upon receiving this notification, the distributed power management control circuit 36 ​​instructs the transmission data generation circuit 35 to generate the next measurement data output request packet in order to request the measurement results of the next connected device. At the same time, the distributed power management control circuit 36 ​​also notifies the operation plan creation circuit 34 that it has received the measurement data. This operation is performed for all devices that measure the interconnection point voltage and power flow of the DC distribution system 21, which are connected to the DC distribution system 21.

[0185] Once all measurement data has been collected, the operation plan creation management circuit 346 within the operation plan creation circuit 34 instructs the power generation prediction circuit 342 and the power consumption prediction circuit 343 via the battery operation plan generation circuit 341 to update the power generation prediction database 351 and the power consumption prediction database 352 based on the collected measurement data. Upon receiving the instruction, the power generation prediction circuit 342 and the power consumption prediction circuit 343 calculate the amount of power generated by each PV panel 12 over a 5-minute period and the amount of power consumed by each customer load 11 from the received data in order to update the power generation prediction database 351 and the power consumption prediction database 352. The power generation prediction circuit 342 and the power consumption prediction circuit 343 add the calculated power consumption to the amount of power generated and power consumed up to date stored in registers (not shown) and check whether it is time to update the database. In Embodiment 1, as described above, the power generation forecast database 351 and the power consumption forecast database 352 construct the power generation amount of PV panels 12a to 12n and the power consumption of consumer loads 11a to 11n every 30 minutes. Therefore, once the measurement data for power generation and power consumption over a 30-minute period is available, the database is updated based on the date, time, day of the week, and weather information. At that time, the 30-minute sum data stored in a register (not shown) is cleared and used for adding measurement data for subsequent 30-minute periods. Also, as described above, the power consumption forecast database 352 creates and updates demand fluctuation range forecast information for each consumer load group 10 based on the received measurement results.

[0186] When the construction (update) of the power generation forecast database 351 and the power consumption forecast database 352 in S107 of Figure 26 is completed, the process proceeds to S108. In S108, the operation plan creation unit management circuit 346 checks the collected measurement data to determine whether or not the operation plan needs to be revised. Specifically, in Embodiment 1, the operation plan creation unit management circuit 346 checks whether the interconnection point (receiving point) voltage of the DC distribution system 21 of the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery is outside a predetermined range, whether the SOC of the distribution system battery 8 is outside a predetermined range, and whether the power output from the AC / DC converter 6 is within a predetermined range centered on the demand power notified by the DSO2.

[0187] Figure 33 is a flowchart showing an example of the procedure for determining whether to modify the operation plan in S108. When the operation plan modification flowchart is started, in S10801, the operation plan creation unit management circuit 346 clears (sets to zero) the operation plan modification flag register (not shown). In S10802 and S10803, the operation plan creation unit management circuit 346 collects the measured voltage and power of the AC / DC converter 6 and the power receiving terminal (grid connection point) power converters 9a to 9n for the power distribution system battery from the memory circuit 32. In S10804, the operation plan creation unit management circuit 346 collects SOC information of the power distribution system battery power converters 9a to 9n from the memory circuit 32. In S10805, the operation plan creation unit management circuit 346 calculates the measured value of power flow current based on the measured values ​​of the demand power of the customer load groups 10a to 10n and the measured voltage and output power of the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery collected in S10802 and S10803.

[0188] In S10806, the operation plan creation unit management circuit 346 selects the AC / DC converter 6. In S10807, the operation plan creation unit management circuit 346 checks whether the voltage at the power receiving point (grid connection point) of the selected AC / DC converter 6 is within a predetermined range (within the range of the upper limit voltage (Vrange_max) and lower limit voltage (Vrange_min) shown in Figure 20 or Figure 21). If it is not within the predetermined range (NO), the process proceeds to S10809.

[0189] In S10809, the operation plan creation unit management circuit 346 sets a register for an operation plan modification flag (not shown) to 1. If the answer in S10807 is YES, the process proceeds to S10808. In S10808, the operation plan creation unit management circuit 346 checks whether the output power is within the planned range. Specifically, the operation plan creation unit management circuit 346 checks whether the demand power notified from the DSO2 is within a predetermined range centered on it. If it is outside the predetermined range in S10808, the process proceeds to S10809. In S10809, the operation plan creation unit management circuit 346 sets a register for an operation plan modification flag (not shown) to 1.

[0190] If the answer to S10808 is YES, or if the operation plan modification flag is set in S10809, the process proceeds to S10810. In S10810, the operation plan creation unit management circuit 346 selects the power converter 9a for the distribution system battery downstream of the AC / DC converter 6. In S10811, the operation plan creation unit management circuit 346 checks whether the measured power receiving point voltage is within a predetermined range. If it is outside the predetermined range in S10811 (NO), the process proceeds to S10815. In S10815, the operation plan creation unit management circuit 346 sets the register for the operation plan modification flag (not shown) (sets it to 1). If the answer to S10811 is YES, the process proceeds to S10812. In S10812, the operation plan creation unit management circuit 346 checks whether the measured output power of the selected power converter 9 for the power distribution system battery is within the planned range (greater than Pmax or less than Pmin as shown in Figure 20 or Figure 21). If it is outside the planned range (NO), the process proceeds to S10815. In S10815, the operation plan creation unit management circuit 346 sets the register of the operation plan correction flag (not shown) to 1.

[0191] If the answer to S10812 is YES, the process proceeds to S10813. In S10813, the operation plan creation unit management circuit 346 checks whether the State of Charge (SOC) of the power distribution system battery 8 controlled by the selected power conversion device 9 for power distribution system batteries is within a predetermined range. In Embodiment 1, the operation plan creation unit management circuit 346 determines that charging when the SOC exceeds 90% or discharging when the SOC is 5% or less requires modification of the operation plan (determining that the SOC is outside the predetermined range), and the process proceeds to S10815. In S10815, the operation plan creation unit management circuit 346 sets a register for an operation plan modification flag (not shown) (sets it to 1). If the answer to S10813 is YES, the process proceeds to S10814. In S10814, the operation plan creation unit management circuit 346 compares the measured power current value with the power distribution system power current calculation result calculated in S1056 during operation planning to confirm whether the measured power current is within a predetermined range. If the measured power current is outside the predetermined range, the process proceeds to S10815. In S10815, the operation plan creation unit management circuit 346 sets a register for an operation plan correction flag (not shown) (sets it to 1). If the measured power current value is within the predetermined range in S10814, or if the operation plan correction flag has been set in S10815, the process proceeds to S10816. In S10816, the operation plan creation unit management circuit 346 confirms whether the output voltage, etc., has been checked for all first DC / DC conversion circuits 93 in the power conversion devices 9 for power distribution system batteries. If all checks have not been completed (if NO), the process proceeds to S10817. In S10817, the operation plan creation unit management circuit 346 selects the first DC / DC conversion circuit 93 within the power converter for power storage batteries 9, which is connected downstream of the power converter for power storage batteries 9 in the power converter for power storage batteries 9. After that, the process returns to S10811. On the other hand, if the answer in S10816 is YES, the operation plan modification decision is terminated. Then, in S108 in Figure 26, the operation plan creation unit management circuit 346 checks the operation plan modification flag. If the operation plan modification flag is not set for any of the converters, the process returns to S100. If the operation plan modification flag is set for at least one converter, the process proceeds to S109, and operation plan modification 1 is performed.

[0192] The following flowchart for Operation Plan Modification 1 will be explained using Figure 34. When operation plan modification is initiated, in S10901, the operation plan creation unit management circuit 346 collects measured values ​​of the supply and demand (difference between the power generated by the customer load 11 and the PV panel 12) for each customer load group 10a to 10n. In S10902, the operation plan creation unit management circuit 346 reads out the estimated impedance (the result estimated in S100 of Figure 26). In S10903, the operation plan creation unit management circuit 346 extracts the power converter 9 for the distribution system battery for which the operation plan modification flag is set. In S10904, the operation plan creation unit management circuit 346 checks whether the output power of the AC / DC converter 6 is within a predetermined range centered on the demand power notified by the DSO2 (the range of the maximum and minimum demand power values ​​notified by the DSO2). If none are present, the process proceeds to S10905, and the power command values ​​for the distribution system batteries 8a to 8n are corrected.

[0193] Figure 35 is a flowchart of the power command value correction 1 for the distribution system battery 8 in S10905. When the correction of the power command value for the distribution system battery 8 is started, in S109051 the operation plan creation unit management circuit 346 reads the supply and demand plan collected from DSO2 from the memory circuit 32.

[0194] In S109052, the operation plan creation unit management circuit 346 reads the measured power value of the AC / DC converter 6 from the memory circuit 32. In S109053, the operation plan creation unit management circuit 346 generates a power command value (Pref) for the AC / DC converter 6. In Embodiment 1, the power command value (Pref) for the AC / DC converter 6 is set to the measured output power value of the AC / DC converter 6. However, if the measured power value deviates from a predetermined range centered on the demand power notified by the DSO2 (for example, a range of ±5% of the power command value (Pref). In Embodiment 1, 5% is notified by the DSO2), it is clipped (restricted) to the upper limit of the predetermined range (if it is above the upper limit) or the lower limit of the predetermined range (if it is below the lower limit).

[0195] In S109054, the operation plan creation unit management circuit 346 calculates the difference in power between the measured power value of the AC / DC converter 6 and the power command value (Pref) calculated in S109053, and allocates the calculated difference in power to each power converter 9 for the distribution system battery. The difference in power between the measured power value of the AC / DC converter 6 and the newly calculated power command value represents the surplus or deficit power of the DC distribution system 21. In Embodiment 1, this surplus or deficit power is to be covered by the power converters 9a to 9n for the distribution system battery installed in the DC distribution system 21. Therefore, in Embodiment 1, the difference in power is to be allocated according to the ratio of the power command values ​​of each power converter 9 for the distribution system battery generated during operation plan creation.

[0196] Once the allocation of differential power is completed in S109054, in S109055, the operation plan creation unit management circuit 346 generates a power command value based on the measured power of the power converters 9a to 9n for the distribution system battery. Specifically, the operation plan creation unit management circuit 346 generates a power command value by adding the power allocated in S109054 to the measured power output by each power converter 9 for the distribution system battery.

[0197] In S109056, the operation plan creation unit management circuit 346 checks whether the power command value of each power converter 9 for distribution system batteries exceeds the capacity of the first DC / DC converter circuit 93. If it exceeds the converter capacity (NO), the process returns to S109054. In S109054, the operation plan creation unit management circuit 346 changes the power allocated to each power converter 9 for distribution system batteries. In Embodiment 1, in S109056, the operation plan creation unit management circuit 346 sets the power command value of each power converter 9 for distribution system batteries that exceeds the converter capacity to the converter capacity (Pmax during discharge, Pmin during charging), and controls the system to allocate the difference power to the power converter 9 for distribution system batteries that does not exceed the converter capacity. If it does not exceed the converter capacity (YES), the process proceeds to S10957. In S10957, the operation plan creation unit management circuit 346 checks whether the power command values ​​for all power converters 9a to 9n for the distribution system battery have been calculated. If they have not been calculated (NO), the process returns to S109055. On the other hand, if the calculation of power command values ​​for all power converters 9a to 9n for the distribution system battery has been completed (YES), the operation plan creation unit management circuit 346 completes the correction 1 of the power command value for the distribution system battery 8.

[0198] Returning to Figure 34, once the correction 1 of the power command value for the distribution system battery 8 in S10905 is completed, the process proceeds to S10906. In S10906, the operation plan creation unit management circuit 346 calculates the power flow current of the DC distribution system 21 based on the measured data. Specifically, the operation plan creation unit management circuit 346 uses the newly generated power command value to calculate the power flow current based on the output power of the AC / DC converter 6, the charge and discharge power of the distribution system battery power converters 9a to 9n, the measured power consumption of the customer loads 11a to 11n, and the measured power generation power of the PV panels 12a to 12n. If the calculation of the power flow current is completed in S10906, or if the answer is YES in S10904, the process proceeds to S10907. In S10907, the operation plan creation unit management circuit 346 selects the power converter 9a for the distribution system battery installed downstream of the AC / DC converter 6. In S10908, the operation plan creation unit management circuit 346 checks whether the SOC of the distribution system battery 8 is within a predetermined range (as described above, if the SOC is 90% or more during charging operation, and if the SOC is 5% or less during discharging operation, it is judged to be in deviation). If it is outside the predetermined range, the process proceeds to S10909. In S10909, the operation plan creation unit management circuit 346 corrects the power command value based on the SOC.

[0199] In general, with lithium-ion batteries, overcharging or over-discharging can rapidly degrade the battery, and in the worst case, it may even break. To prevent this, for example, electric vehicle chargers charge with constant current control when the SOC is below 90%, and switch to constant voltage control when it exceeds 90%. Also, to prevent over-discharge during discharge, they are often configured to reduce the discharge power when the SOC falls below 5%. In the case of general lead-acid batteries, overcharging does not degrade them as rapidly as lithium-ion batteries, but they will break if over-discharged. Thus, although the characteristics differ depending on the type of battery, charging in the high SOC range and discharging in the low SOC range have the disadvantage of accelerating battery degradation. Therefore, in Embodiment 1, a lithium-ion battery is used as the battery 8 for the power distribution system, and the power command value is reduced when charging above SOC 90% or discharging below SOC 5%.

[0200] Figure 36 is a detailed operation flowchart of S10909. When S10909 starts, in S109091, the operation plan creation unit management circuit 346 checks whether the SOC exceeds a predetermined value (90% in Embodiment 1). If the SOC exceeds 90% (YES), the process proceeds to S109092. In S109092, the operation plan creation unit management circuit 346 checks whether it is discharge control or not, and if it is discharge control (YES), there is no particular problem and the process ends. On the other hand, if it is charge control (NO), the process proceeds to S109093. In S109093, the operation plan creation unit management circuit 346 checks whether the power command value (charge) is above a predetermined value. In actual control, it is better to switch the control of the power distribution system battery 8 to constant voltage control as described above, but in Embodiment 1, for the sake of simplicity, it is assumed that it checks whether it is above 10% of the converter capacity of the first DC / DC conversion circuit 93. In S109093, if the value is below the predetermined value (NO), there is no particular problem and the flowchart is terminated. On the other hand, if the value is above the predetermined value (YES), the process proceeds to S109094. In S109094, the operation plan creation unit management circuit 346 changes the power command value. In Embodiment 1, the power command value is set to 10% (charge) of the converter capacity of the first DC / DC conversion circuit 93.

[0201] On the other hand, if the answer to S109091 is NO, the process proceeds to S109095. In S109095, the operation plan creation unit management circuit 346 checks whether the SOC is less than a predetermined value (5% in Embodiment 1). If it is greater than or equal to the predetermined value (NO), there is no particular problem and the flowchart is terminated. If the answer to S109095 is YES, the process proceeds to S109096. In S109096, the operation plan creation unit management circuit 346 checks whether it is discharge control or not. If it is charge control (NO), there is no particular problem and the flowchart is terminated. If it is discharge control, the process proceeds to S109097. In S109097, the operation plan creation unit management circuit 346 checks whether the discharge power command value is less than or equal to a predetermined value. In Embodiment 1, the operation plan creation unit management circuit 346, for the sake of simplicity, checks whether it is 10% or more of the converter capacity of the first DC / DC conversion circuit 93, similar to the charge operation. In S109097, if the value is below a predetermined value (YES), there is no particular problem, and the process is terminated. If the value in S109097 is NO, the process proceeds to S109098. In S109098, the operation plan creation unit management circuit 346 changes the charging power command value. In Embodiment 1, the operation plan creation unit management circuit 346 sets the charging power command value to 10% of the converter capacity of the first DC / DC conversion circuit 93 (discharge). Specifically, the power command value is set to 10% of the converter capacity.

[0202] Returning to Figure 34, S10909 is terminated, or if S10908 is YES, the process proceeds to S10910. In S10910, the operation plan creation unit management circuit 346 checks whether the SOC of all distribution system batteries 8 has been confirmed. If the SOC of all distribution system batteries 8 has not been confirmed (NO), the process proceeds to S10911. In S10911, the operation plan creation unit management circuit 346 selects the power converter 9 downstream of the power converter 9 for distribution system batteries selected in S10907 or S10911 (the power converter 9 for distribution system batteries currently selected). After that, the process returns to S10908. On the other hand, if S10910 is YES, the process proceeds to S10912. In S10912, the operation plan creation unit management circuit 346 calculates (estimates) the power flow current of the DC distribution system 21 based on the modified power command values ​​of the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery. Subsequently, in S1057, the operation plan creation unit management circuit 346 performs voltage prediction 1 at each power receiving point. In this embodiment 1, the voltage prediction 1 at each power receiving point in S1057 is the same as the flowchart shown in Figure 30, so the explanation of its operation will not be repeated.

[0203] In S10913, the operation plan creation unit management circuit 346 checks whether the voltages at all grid connection points (power receiving points) are within a predetermined range. If the voltages at all grid connection points (power receiving points) are within the predetermined voltage range (YES), the process proceeds to S10916. In S10916, the operation plan creation unit management circuit 346 regenerates the drooping characteristics. Details will be described later. On the other hand, if the answer in S10913 is NO, the process proceeds to S1060. In S1060, the operation plan creation unit management circuit 346 performs a review 1 of the charge / discharge power (power command value) of the distribution system battery 8. Note that the flowchart for the review 1 of the charge / discharge power (power command value) of the distribution system battery 8 in S1060 is the same as that shown in Figure 31, so the explanation of the operation will not be repeated. When S1060 is completed, the process proceeds to S10914. In S10914, the operation plan creation unit management circuit 346 calculates the power flow current of the DC distribution system 21 using the corrected power command values ​​(Pref) of the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery. In S1057, the operation plan creation unit management circuit 346 performs voltage prediction 1 at each power receiving point (explanation omitted as it is the same as the flowchart shown in Figure 30) based on the calculation results. Then, in S10915, the operation plan creation unit management circuit 346 checks whether the voltages at all system connection points (power receiving points) are within a predetermined range. If they are not (NO), the process returns to S1060. On the other hand, if the answer is YES in S10915, or YES in S10913, the process proceeds to S10916. In S10916, the operation plan creation unit management circuit 346 performs droop characteristic generation 2. In Embodiment 1, the power receiving point voltage of each converter estimated in the manner described above is used as the voltage command value.

[0204] [Correction based on Rule 91 25.12.2025] Figure 37 is a flowchart of the drooping characteristic generation 2. In Figure 37, when the drooping characteristic generation 2 flowchart is started, in S10916, the distributed power management control circuit 36 ​​(see Figure 2) in the CEMS 3 outputs an instruction to the control parameter generation circuit 33 to generate the drooping characteristics of each converter. In S109160, the power flow current fluctuation range estimation circuit 331 (see Figure 4) in the control parameter generation circuit 33 receives the instruction and obtains the power command values ​​of each converter generated in the operation plan correction 1 flowchart. In S109161, the power flow current fluctuation range estimation circuit 331 collects the impedance value of the distribution system impedance 7 and the calculation results of the power flow current flowing through each distribution system impedance 7 calculated in S10912 or S10914 (see Figure 34). In S109162, the demand power fluctuation prediction circuit 332 collects the measured and predicted results of the power generation and power consumption of the consumer PV. In S109163, the demand power fluctuation prediction circuit 332 predicts the demand fluctuation for each of the consumer load groups 10.

[0205] Specifically, the demand power fluctuation prediction circuit 332 reads the maximum (measured) and minimum (measured) demand power values ​​of each customer load group 10 from the power consumption prediction database 352 to the operation plan creation unit management circuit 346 within the operation plan creation circuit 34, and predicts the range of demand fluctuations based on the power command values ​​of each converter collected in S109160. The difference between the maximum (measured) demand power value of each customer load group 10 and the power command value of the power converter 9 for distribution system batteries installed nearby is the upper limit of the fluctuation range, and the difference between the power command value of the power converter 9 for distribution system batteries and the minimum (measured) demand power value of the nearby customer load group 10 is the lower limit of the fluctuation range. The demand power fluctuation prediction circuit 332 sets the upper limit of the fluctuation range to zero if the power command value of the power converter 9 for the distribution system battery exceeds the maximum value of the demand power (measured), and sets the lower limit of the fluctuation range to zero if the power command value of the power converter 9 for the distribution system battery is lower than the minimum value of the demand power (measured).

[0206] In S109164, the demand power fluctuation prediction circuit 332 allocates the differential power generated by the demand power fluctuation to each converter when a demand power fluctuation occurs in each consumer load group 10. Specifically, the demand power fluctuation prediction circuit 332 allocates the differential power between the total demand power of the DC distribution system 21 when the demand power of each consumer load group 10 reaches the maximum (measured) and minimum (measured) values ​​read from the power consumption prediction database 352, and the sum of the power command values ​​(Pref) of each converter, to each converter. In Embodiment 1, since the slope of the drooping characteristic of the AC / DC converter 6 is not changed, the differential power is allocated to each power converter 9 for the distribution system battery.

[0207] Specifically, in Embodiment 1, the power is distributed according to the ratio of the power command values ​​(Pref) notified to each converter, similar to the operation plan creation process. The power distribution system's demand power fluctuation prediction circuit 332 can achieve similar effects by allocating differential power to each converter based on the SOC information of the distribution system battery 8 (in the case of discharge, the larger the SOC, the more power is allocated to the discharged power), or by allocating a larger amount to the distribution system battery 8 that has not deteriorated as much based on the SOH information, or by distributing the power according to the ratio of the converter capacities of each converter.

[0208] Once the demand power fluctuation prediction circuit 332 has completed the allocation of differential power, the process proceeds to S106105. In S106105, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current flowing through each distribution system impedance 7 (the fluctuation range of the system connection point voltage with the DC distribution system 21 for each converter, and the fluctuation range of the output power). Specifically, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current based on the power command value (Pref) notified to each converter, the impedance value of each distribution system impedance 7 collected in S109161, the power flow current flowing through the distribution system impedance 7, and the estimated result of the connection point voltage with the DC distribution system 21 for each converter. Specifically, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current flowing through each distribution system impedance 7 based on the calculation results of the power flow current flowing through each distribution system impedance 7 calculated in S1056, the power generation amount of each consumer collected in S106102, the power demand forecast results of each consumer load group 10 calculated from the power consumption forecast results, the power demand fluctuation forecast results of each consumer load group 10 predicted in S106103, the differential power allocation results of each converter assigned in S109164, and the power command value (Pref) of each converter. The fluctuation range is estimated from the power flow current when the power demand of each consumer load group 10, stored in the power consumption forecast database 352, reaches its maximum value (measured) and minimum value (measured). In Embodiment 1, the power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the voltage at the grid connection point with the DC power distribution system 21 and the fluctuation range of the output power of each converter based on the allocation result of the differential power of each converter allocated in S109164.

[0209] The power flow current fluctuation range estimation circuit 331 estimates the fluctuation range of the power flow current flowing through each distribution system impedance 7 based on the calculation results of the power flow current flowing through each distribution system impedance 7 calculated in S1056, the power generation amount of each consumer collected in S106102, the power demand forecast results of each consumer load group 10 calculated from the power consumption forecast results, the power demand fluctuation forecast results of each consumer load group 10 predicted in S106103, the differential power allocation results of each converter assigned in S109164, and the power command value (Pref) of each converter. Specifically, the power flow current fluctuation range estimation circuit 331 calculates the differential value of the power flow current flowing through the distribution system impedance 7a by dividing the differential power allocated to the AC / DC converter 6 by the voltage command value (Vref). Similarly, when the power flow current fluctuation range estimation circuit 331 calculates the power flow current flowing through the distribution system impedance 7x (where x is a to n), it calculates it by dividing (the fluctuation in the demand power of the customer load group 10x-1 - the differential power allocated to the power converter for the distribution system battery 9x-1) by the voltage command value (Vref) of the power converter for the distribution system battery 9x-1. This allows the differential value of the power flow current flowing through the distribution system impedance 7x to be estimated (calculated). Once the estimation of the differential current is complete, the power flow current fluctuation range estimation circuit 331 calculates the power flow current flowing through each distribution system impedance 7 based on the estimation results. Specifically, the power flow current fluctuation range estimation circuit 331 calculates the power flow current flowing through each distribution system impedance 7 by adding the differential value of the power flow current estimated in S106105 to the power flow current flowing through each distribution system impedance 7 collected in S109161.

[0210] In S106106, the droop characteristic slope determination circuit 333 calculates the slope of the droop characteristic of each converter. In Embodiment 1, as described above, the droop characteristic of the AC / DC converter 6 is the same as that of conventional control as shown in Figure 22. Specifically, in Embodiment 1, the droop characteristic slope determination circuit 333 sets the voltage command value (Vref) to 1500V in Figure 20, and determines the droop characteristic so that Vrang_max becomes the minimum demand power value notified from DSO2, and Vrang_min becomes the minimum demand power value notified from DSO2. The droop characteristic slope determination circuit 333 determines the slope of the droop characteristic by determining the gentler slope of the straight line connecting (the minimum demand power value notified from DSO2, Vrang_max) and (the power command value (Pref) and voltage command value (Vref)) and the straight line connecting (the maximum demand power value notified from DSO2, Vrang_min) and (the power command value (Pref) and voltage command value (Vref)).

[0211] The droop characteristic slope determination circuit 333 calculates the slope of the droop characteristic of the power converter for distribution system batteries 9a, which is located one downstream of the AC / DC converter 6. In the following description, it is assumed that the power converters for distribution system batteries 9a and 9b operate in voltage control mode. Specifically, the droop characteristic slope determination circuit 333 calculates the voltage (upper limit voltage and lower limit voltage) of the AC / DC converter 6 when it outputs the differential power (maximum value and minimum value) allocated to the AC / DC converter 6, based on the droop characteristic of the AC / DC converter 6. Next, the droop characteristic slope determination circuit 333 estimates the voltage (upper limit voltage and lower limit voltage) of the power converter for distribution system batteries 9a from the power current flowing through the distribution system impedance 7a, the impedance value of the distribution system impedance 7a, and the output voltage of the AC / DC converter 6. The droop characteristic slope determination circuit 333 determines the slope of the droop characteristic of the power converter 9a for the power distribution system battery by determining the slope of the straight line connecting (the difference power (maximum value) allocated to the power converter 9a for the power distribution system battery in S109164, and the voltage estimation result of the power converter 9a for the power distribution system battery (lower voltage limit)) and (the difference power (minimum value) allocated to the power converter 9a for the power distribution system battery in S109164, and the voltage estimation result of the power converter 9a for the power distribution system battery (upper voltage limit)). If this straight line does not pass through (power command value (Pref), voltage command value (Vref)) of the power converter 9a for the power distribution system battery, the droop characteristic slope determination circuit 333 determines the slope of the straight line passing through (the differential power (maximum value) allocated to the power converter 9a for the power distribution system battery in S109164, the estimated voltage result of the power converter 9a for the power distribution system battery (lower limit voltage)) and (power command value (Pref), voltage command value (Vref)), and the slope of the straight line passing through (the differential power (minimum value) allocated to the power converter 9a for the power distribution system battery in S109164, the estimated voltage result of the power converter 9a for the power distribution system battery (upper limit voltage)) and (power command value (Pref), voltage command value (Vref)), and the one with the gentler slope is taken as the slope of the droop characteristic of the power converter 9a for the power distribution system battery. Similarly, the droop characteristic slope determination circuit 333 estimates the voltage (upper limit voltage and lower limit voltage) of the power converter 9a for the power distribution system battery from the power current flowing through the power distribution system impedance 7b, the impedance value of the power distribution system impedance 7b, and the output voltage of the power converter 9a for the power distribution system battery.The droop characteristic slope determination circuit 333 determines the slope of the droop characteristic of the power converter 9b for the power distribution system battery by determining the slope of the straight line connecting (the difference power allocated to the power converter 9b for the power distribution system battery in S109164 (maximum value) and the voltage estimation result of the power converter 9b for the power distribution system battery (lower limit voltage)) and (the difference power allocated to the power converter 9b for the power distribution system battery in S109164 (minimum value) and the voltage estimation result of the power converter 9a for the power distribution system battery (upper limit voltage)). The droop characteristic slope determination circuit 333 determines the slope of the line passing through (the power command value (Pref), voltage command value (Vref)) of the power converter 9b for the power distribution system battery if the straight line does not pass through (the differential power (maximum value) allocated to the power converter 9b for the power distribution system battery in S109164, the estimated voltage result (lower limit voltage) of the power converter 9b for the power distribution system battery) and (the power command value (Pref), voltage command value (Vref)), and the slope of the line passing through (the differential power (minimum value) allocated to the power converter 9b for the power distribution system battery in S109164, the estimated voltage result (upper limit voltage) of the power converter 9b for the power distribution system battery) and (the power command value (Pref), voltage command value (Vref)), and sets the gentler slope of the line as the slope of the droop characteristic of the power converter 9b for the power distribution system battery. The above operations are carried out until the slope of the power converter 9n for the distribution system battery is calculated. Note that when the power converter 9x for the distribution system battery is operating in power control mode, the X-axis (horizontal axis) and Y-axis (vertical axis) are reversed compared to the voltage control mode, as shown in Figure 21, so the slope can be calculated by reversing the X and Y coordinates as described above.

[0212] In S106107, the droop characteristic generation circuit 334 generates the droop characteristics of each converter. In Embodiment 1, similar to when creating the operation plan, the braking coefficient Dg is calculated using the control mode of each converter and the slope of the droop characteristics calculated in S106106, using the above-described equation (5) (voltage control mode) or equation (6) (power control mode). Therefore, the speed adjustment rate Kgd, governor time constant Tg, and inertia constant M are not changed. In Embodiment 1, only the braking coefficient Dg was changed, but this is not the only change. For example, the droop characteristic generation circuit 334 may be controlled to change the speed adjustment rate Kgd, or to change the braking coefficient Dg and the speed adjustment rate Kgd based on equation (5) (voltage control mode) or equation (6) (power control mode), and further to change the inertia constant M (such as so that M / Dg remains constant) in accordance with the change in the braking coefficient Dg.

[0213] When S106107 (S10916) is completed, the control parameter generation circuit 33 notifies the distributed power management unit control circuit 36 ​​of this fact. Upon receiving this notification, the distributed power management unit control circuit 36 ​​notifies the operation plan creation circuit 34. The operation plan creation circuit 34 completes operation plan modification 1 in S109 (see Figure 34).

[0214] When the operation plan modification 1 in S109 of Figure 26 is completed, the operation plan creation unit management circuit 346 sends the drooping characteristics (parameters), voltage command value (Vref), and power command value (Pref) created in S110 to the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery. When the transmission of the operation plan is completed in S110, the operation plan creation unit management circuit 346 determines in S111 whether to terminate the operation of CEMS3, and if it is to terminate (if YES), it stops the operation of CEMS3. On the other hand, if it is NO, it returns to S100 and continues the flowchart thereafter.

[0215] As described above, the CEMS 3 of Embodiment 1 manages the voltage of the DC distribution system 21 by allocating the surplus and deficit power calculated based on information such as the supply and demand power command value of the AC / DC converter 6 notified by the DSO2, the predicted power generation results of the customer loads 11 and PV panels 12 within the customer load groups 10a to 10n, and the SOC of each distribution system battery 8a to 8n to the power converters 9a to 9n for distribution system batteries (power command value (Pref)). Furthermore, the CEMS 3 of Embodiment 1 estimates the grid connection point (receiving point) voltage based on the estimated distribution system impedance of the DC distribution system 21 estimated based on actual measurement data, and generates a voltage command value (Vref) based on the estimated result. Then, the CEMS 3 of Embodiment 1 determines the drooping characteristics of each converter based on the estimated fluctuation range of the supply and demand power of each customer load group 10. This allows for proper management of the grid connection point (receiving point) voltage of the DC distribution system 21 to which the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery are connected, and also allows for proper distribution of the differential power output from each converter using the drooping characteristic even when fluctuations in supply and demand power occur (allowing for proper management of the SOC of the distribution system battery 8).

[0216] In Embodiment 1, the CEMS 3 controls the power command value (Pref), voltage command value (Vref), and droop characteristics based on the measured results, even if the voltage at the grid connection point (receiving point) of the DC distribution system 21 falls outside the appropriate range due to load fluctuations or power generation fluctuations. This allows for appropriate management of the voltage at the grid connection point (receiving point) of the DC distribution system 21 and the SOC of the distribution system battery 8. In Embodiment 1, measurement data is collected at a 5-minute cycle from the AC / DC converter 6, the power converters 9a to 9n for the distribution system battery, and each customer load group 10, but this is not the only configuration. To appropriately manage the voltage at the grid connection point (receiving point), the measurement cycle may be shortened to a 1-minute cycle or a 30-second cycle, if the processing of the CEMS 3 can keep up.

[0217] Next, the operation of the AC / DC converter 6 and the power conversion device 9 for the power distribution system battery will be described using Figures 5 to 16 and Figures 38 to 41. In Embodiment 1, the AC / DC converter 6 is assumed to operate in voltage control mode, and the power conversion devices 9a to 9n for the power distribution system battery are assumed to be capable of two types of operation: voltage control mode and power control mode. The operation of the AC / DC converter 6 will be described below with reference to Figure 5.

[0218] In Embodiment 1, the AC / DC converter 6 operates in current control mode for the AC power distribution system 20. At the same time, the AC / DC converter 6 is controlled to operate in voltage control mode for the DC power distribution system 21. In Figure 5, voltmeters 61a and 61b measure the voltage of the three-phase AC system. Ammeters 62a and 62b measure the current of the three-phase AC system. Note that the phase voltage and phase current of the phases not connected to the voltmeters and ammeters are calculated using the results measured by each voltmeter 61 and each ammeter 62. Voltmeter 66 measures the voltage of the DC power distribution system 21. Ammeter 67 measures the current of the DC power distribution system 21. The measurement results of voltmeters 61a, 61b, ammeters 62a, 62b, voltmeter 66, and ammeter 67 are input to the first control circuit 64.

[0219] The detailed operation of the first control circuit 64 will now be explained with reference to Figure 8. In Figure 8, the phase detection circuit 641 detects the zero-crossing point of the AC system voltage waveform of the AC distribution system 20b measured by the voltmeter 61. The first sine wave generation circuit 642 generates a reference sine wave synchronized with the AC system voltage waveform of the AC distribution system 20b used for current control, based on the zero-crossing point information detected by the phase detection circuit 641 and the AC system voltage waveform output from the voltmeter 61, and outputs it to the multiplier 645. The measurement result of the voltage of the DC distribution system 21 by the voltmeter 66 is input to the subtractor 643 in the current control circuit 640 and the fourth control circuit 647. The control method of the current control circuit 640 is a control method that outputs power synchronized with the AC system voltage (current control), which is the control method of a typical solar power generation power converter installed in a home. The fourth control circuit 647 stores the target voltage of the DC power distribution system 21 and outputs the target voltage to the subtractor 643. As will be described in detail later, the target voltage of the DC power distribution system 21 is generated by the first voltage target generation circuit 682 and output to the subtractor 643 in the current control circuit 640 via the fourth control circuit 647. The current control circuit 640 controls the AC current output from the first AC / DC conversion circuit 63 so that the voltage of the DC power distribution system 21 output from the voltmeter 66 becomes the target voltage.

[0220] The output of the subtractor 643 is input to the first PI control circuit 644. The first PI control circuit 644 performs PI control so that the output of the subtractor 643 becomes zero. The output of the first PI control circuit 644 is input to the multiplier 645 and multiplied with the output of the first sine wave generation circuit 642 to convert it into a current command value. The subtractor 646 subtracts the output of the multiplier 645 from the AC current value of the AC distribution system 20b measured by the ammeter 62 and inputs the subtraction result to the second PI control circuit 648. The second PI control circuit 648 performs PI control so that the output of the subtractor 646 becomes zero. The first PWM conversion circuit 649 PWM modulates the output of the second PI control circuit 648 and outputs it to the first AC / DC conversion circuit 63. The first AC / DC conversion circuit 63 outputs an alternating current based on the command value output from the first PWM conversion circuit 649.

[0221] The fourth control circuit 647 collects measurement results related to the DC power distribution system 21 output from the voltmeter 66 and ammeter 67, and measurement results related to the AC power distribution system 20 output from the voltmeter 61 and ammeter 62, and notifies the CEMS 3 and other systems of this information via the first communication interface circuit 65. The fourth control circuit 647 also measures the effective voltage of the AC power distribution system 20b using an effective voltage measurement unit (not shown) and notifies the CEMS 3 of this measurement. The fourth control circuit 647 also notifies the CEMS 3 of the active power and reactive power information measured by the active and reactive power measurement units of the AC system (not shown) via the first communication interface circuit 65.

[0222] Next, the detailed operation of the first AC / DC conversion circuit 63 will be explained using the flowchart shown in Figure 38. When control of the first DC / AC conversion circuit 63 is started, in S201, the fourth control circuit 647 initializes various parameters in the first control circuit 64. In S202, the fourth control circuit 647 sets the power command value to "zero" and the voltage command value to "1500V". In S203, the fourth control circuit 647 collects information from various voltage and current sensors. In S204, the fourth control circuit 647 starts controlling the first AC / DC conversion circuit 63.

[0223] Figure 39 is a detailed flowchart of the control of the first AC / DC conversion circuit 63. When control of the first AC / DC conversion circuit 63 is started, in S2041, the fourth control circuit 647 acquires the measurement results of the AC-side voltmeters 61a and 61b. In S2042 and S2043, the fourth control circuit 647 instructs the phase detection circuit 641 to detect the AC frequency and phase of the AC power distribution system 20b. In Embodiment 1, the phase detection circuit 641 detects the zero-crossing point from the AC voltage waveform output from the AC-side voltmeters 61a and 61b, and also detects the frequency of the AC system voltage from the zero-crossing point detection result. The phase detection circuit 641 outputs the frequency of the AC system voltage and the zero-crossing point information to the first sine wave generation circuit 642. More specifically, in S2042, the phase detection circuit 641 detects the zero-crossing point (more precisely, the time at which the zero-crossing point was measured) from the AC voltage waveform measured by the AC voltmeters 61a and 61b. In S2043, the phase detection circuit 641 detects the frequency from the time interval of the detected zero-crossing point (the difference between the time of the previously detected zero-crossing point and the time of the currently detected zero-crossing point). The method for detecting the frequency of the AC system voltage is not limited to the method using the detection result of the zero-crossing point. In Embodiment 1, the phase of the AC distribution system 20b is determined using the detection time of the zero-crossing point.

[0224] In S2045, the first power calculation circuit 681 measures the voltage and current of the DC power distribution system 21 using the voltmeter 66 and the ammeter 67. In S2046, the first power calculation circuit 681 calculates the power to be output from the AC / DC converter 6 to the DC power distribution system 21 based on the measured voltage and current information of the DC power distribution system 21. In S2047, the first voltage target generation circuit 682 generates a target voltage for the DC power distribution system 21 using the drooping characteristics notified by the CEMS 3, based on the measured power calculated by the first power calculation circuit 681.

[0225] The operation of the first voltage target generation circuit 682 will be explained below using Figures 11 to 13. The second voltage target generation circuit 942, which is implemented in the power converter 9 for the power distribution system battery shown in Figure 9, has the same configuration. The voltage command value (Vref1) output from the fourth control circuit 647 (fifth control circuit 949) is input to the subtractor 6821 (9421) and the first point mass calculation circuit 6825 (9425). The subtractor 6821 (9421) subtracts the voltage command value (Vref1) from the measurement result of the voltage of the DC power distribution system 21 measured by the voltmeter 66 (96) and outputs it to the first governor control circuit 6822 (9422). In Embodiment 1, the first governor control circuit 6822 (9422) uses a first-order lag system model as shown in equation (1).

[0226] [Correction based on Rule 91 25.12.2025] Figure 12 shows the detailed configuration of the first governor control circuit 6822 (9422). The multiplier 68221 multiplies the output of the subtractor 6821 (9421) by -1 / Kgd1 output from the fourth control circuit 647 (fifth control circuit 949), and outputs the multiplication result to the first-order lag circuit (1 / (1+s×Tg1)) 68222. The first limiter circuit 68223 limits the output of the first-order lag circuit 68222 to a predetermined range and outputs it to the adder 6823 (9423). The adder 6823 (9423) in Figure 11 adds the output of the first governor control circuit 6822 (9422) and the power command value (Pref1) output from the fourth control circuit 647 (fifth control circuit 949), and outputs the addition result to the subtractor 6824 (9424). The subtractor 6824 (9424) subtracts the output of the first power calculation circuit 681 (second power calculation circuit 941) from the output of the adder 6823 (9423), and outputs the subtraction result to the first mass system calculation circuit 6825 (9425). In Embodiment 1, the first mass system calculation circuit 6825 (9425) uses a motion equation model as shown in equation (2).

[0227] Figure 13 shows the detailed configuration of the first point mass arithmetic circuit 6825 (9425). The subtractor 68251 subtracts the output of the multiplier 68253 from the output of the subtractor 6824 (9424) and outputs the subtraction result to the integrator 68252. The integrator 68252 multiplies the subtraction result output from the subtractor 68251 by 1 / M1 (M1 is input from the fourth control circuit 647 (fifth control circuit 949)) and then integrates it. The output of the integrator 68252 is input to the multiplier 68253 and the adder 68254. The multiplier 68252 multiplies the output of the integrator 68252 by the damping coefficient (Dg1) output from the fourth control circuit 647 (fifth control circuit 949) and outputs the multiplication result to the subtractor 68251. The adder 68254 adds the output of the integrator 68252 and the voltage command value (Vref1), and outputs the sum as voltage target value information from the first mass system calculation circuit 6825 (9425).

[0228] In S2047, the output of the first voltage target generation circuit 682 (second voltage target generation circuit 942) is input to the fourth control circuit 647 (second voltage target value control circuit 945 and fifth control circuit 949). In Embodiment 1, the first voltage target generation circuit 682 (second voltage target generation circuit 942) generates a voltage target value in the manner described above.

[0229] In S2048, the fourth control circuit 647 generates the current command value for the first AC / DC conversion circuit 63. Specifically, as described above, the current control circuit 640 in Figure 8 generates the current command value. The measurement result of the voltmeter 66, which measures the voltage of the DC power distribution system 21, is input to the subtractor 643 in the current control circuit 640 and to the fourth control circuit 647. As described above, the fourth control circuit 647 in Figure 8 stores the target voltage of the DC power distribution system 21 output from the first voltage target generation circuit 682, and outputs that target voltage to the subtractor 643.

[0230] The output of the subtractor 643 is input to the first PI control circuit 644. The first PI control circuit 644 performs PI control so that the output of the subtractor 643 becomes zero. The output of the first PI control circuit 644 is input to the multiplier 645. The multiplier 645 multiplies the output of the first PI control circuit 644 and the output of the first sine wave generation circuit 642 and outputs the multiplication result as a current command value. The output of the multiplier 645 is input to the subtractor 646. The subtractor 646 subtracts the output of the multiplier 645 and the AC current value of the AC power distribution system 20b measured by the ammeter 62 and outputs the subtraction result to the second PI control circuit 648. The second PI control circuit 648 performs PI control so that the output of the subtractor 646 becomes zero. The first PWM conversion circuit 649 PWM modulates the output of the second PI control circuit 648 and outputs it to the first AC / DC conversion circuit 63. The first AC / DC conversion circuit 63 outputs an alternating current based on the command value output from the first PWM conversion circuit 649. In S2048 of Figure 39, when the generation of the current command value for the AC / DC conversion circuit 63 is completed, the fourth control circuit 647 terminates the control of the first AC / DC conversion circuit in S204.

[0231] When step S204 in Figure 38 is completed, in step S205, the fourth control circuit 647 checks whether it has received a request to transmit measurement information from the CEMS 3. If it has received a transmission request from the CEMS 3 (YES), the process proceeds to step S206. In step S206, the fourth control circuit 647 outputs the measurement information stored in a memory (not shown) to the first communication interface circuit 65. The first communication interface circuit 65 converts the measurement data received from the fourth control circuit 647 into a predetermined format and sends it to the CEMS 3 via the communication line 22. When step S206 is completed, or if the answer in step S205 is NO, the process proceeds to step S207.

[0232] In S207, the fourth control circuit 647 checks whether it has received control information (voltage command value, power command value, information on droop characteristics, etc.) from the CEMS3. If it has not received the information, the process returns to S203. If it has received the information (YES in S207), the process proceeds to S208. In S208, the fourth control circuit 647 sets the power command value (Pref1), the voltage command value (Vref1), and the droop characteristics (Kgd1, Tg1, M1, DG1) in registers not shown within the fourth control circuit 647. After that, the process returns to S203.

[0233] Next, the operation of the power converter 9 for distribution system batteries will be explained using Figures 6, 9, 11 to 16, 34, and 35. Figure 6 is a block diagram of the power converter 9 for distribution system batteries. Embodiment 1 describes a case in which the power converter 9 for distribution system batteries has two modes: voltage control mode and power control mode. In Embodiment 1, when the power converter 9 for distribution system batteries is operated in voltage control mode, the second voltage target generation circuit 942 shown in Figure 9 generates a power target value. The second voltage target value control circuit 945 generates a current command value to control the first DC / DC conversion circuit 93 based on the voltage target value generated by the second voltage target generation circuit 942. The configuration and operation of the second voltage target generation circuit 942 are the same as those of the first voltage target generation circuit 682, so the explanation of the configuration and operation will not be repeated. On the other hand, when the power converter 9 for the power distribution system battery is operated in power control mode, the power target generation circuit 943 generates a power target value. The power target value control circuit 946 generates a current command value to control the first DC / DC converter circuit 93 based on the power target value generated by the power target generation circuit 943. In Figure 6, the voltmeter 91 measures the output voltage of the power distribution system battery 8. The ammeter 92 measures the output current of the power distribution system battery 8. The voltmeter 96 measures the voltage of the DC power distribution system 21. The ammeter 97 measures the current of the DC power distribution system 21. The measurement results of the voltmeter 91, ammeter 92, voltmeter 96, and ammeter 97 are input to the second control circuit 94.

[0234] The detailed operation of the second control circuit 94 will be explained below using Figure 9. The second power calculation circuit 941 uses the DC voltage of the power converter 9 for the power distribution system battery measured by the voltmeter 96 and the DC current of the power converter 9 for the power distribution system battery measured by the ammeter 97 to calculate the measured charge / discharge power of the power converter 9 for the power distribution system battery (calculated as current × voltage for DC). It goes without saying that the measured charge / discharge current may also be measured using the voltage and current measurement results of the power distribution system battery 8 measured using the voltmeter 91 and ammeter 92. The measured charge / discharge power calculated by the second power calculation circuit 941 is input to the second voltage target generation circuit 942, the power target generation circuit 943, the power target value control circuit 946, and the fifth control circuit 949. In Embodiment 1, the fifth control circuit 949 calculates and manages the SOC and SOH of the power distribution system battery 8, based on the measurement information measured by the voltmeters 91 and 96 and the ammeters 92 and 97, the charge / discharge power information calculated by the second power calculation circuit 941, and the charge / discharge power information. These measurement data, charge / discharge power, and SOC / SOH calculation results are stored in a memory (not shown) and output to the CEMS 3 via the second communication interface circuit 95 when a request to transmit measurement data is received from the CEMS 3. In Embodiment 1, the SOH is estimated based on the temperature information of the power distribution system battery 8 measured by a thermometer (not shown), the voltage transition information of the power distribution system battery 8, the charge / discharge power, and the time when the SOC is 90% or higher. The method for estimating the SOH is not a major feature of this application, so a detailed explanation is omitted.

[0235] The second voltage target generation circuit 942 starts generating a voltage target value when it receives the power calculation result from the second power calculation circuit 941. The configuration (see Figures 11 to 13) and operation of the second voltage target generation circuit 942 are the same as those of the first voltage target generation circuit 682, so no further explanation is needed. The voltage target value output from the second voltage target generation circuit 942 is input to the second voltage target value control circuit 945.

[0236] Figure 18 shows the configuration of the second voltage target value control circuit 945. The subtractor 9451 subtracts the voltage target value input from the second voltage target generation circuit 942 by the measured voltage measured by the voltmeter 96, and outputs the subtraction result to the third PI control circuit 9452. The third PI control circuit 9452 performs PI control so that the output of the subtractor 9451 becomes zero. The result of the PI control is input to the first switching circuit 947 as a control command for the first DC / DC conversion circuit 93.

[0237] Similarly, the power target generation circuit 943 starts generating a power target value when it receives the power calculation result from the second power calculation circuit 941. The operation of the power target generation circuit 943 will be explained below using Figures 14 to 16. The power command value (Pref2) output from the fifth control circuit 949 is input to the subtractor 9431 and the second point mass calculation circuit 9435. The subtractor 9431 subtracts the power command value (Pref2) from the measured power calculation result output from the second power calculation circuit 941 and outputs the subtraction result to the second governor control circuit 9432. In Embodiment 1, the second governor control circuit 9432 also uses a first-order lag system model as shown in equation (1).

[0238] Figure 15 shows the detailed configuration of the second governor control circuit 9432. The multiplier 94321 multiplies the output of the subtractor 9431 by -1 / Kgd2 output from the fifth control circuit 949 and outputs the multiplication result to the first-order lag circuit (1 / (1+s×Tg2)) 94322. The second limiter circuit 94323 limits the output of the first-order lag circuit 94322 to a predetermined range and outputs it from the second governor control circuit 9432. The adder 9433 in Figure 14 adds the output of the second governor control circuit 9432 and the voltage command value (Vref2) output from the fifth control circuit 949 and outputs the addition result to the subtractor 9434. The subtractor 9434 subtracts the output of the voltmeter 96 from the output of the adder 9433 and outputs the subtraction result to the second point mass arithmetic circuit 9435. In Embodiment 1, the second mass system calculation circuit 9435 uses a motion equation model as shown in equation (2).

[0239] Figure 16 shows the detailed configuration of the second point mass arithmetic circuit 9435. The subtractor 94351 subtracts the output of the multiplier 94353 from the output of the subtractor 9434 and outputs the subtraction result to the integrator 94352. The integrator 94352 multiplies the subtraction result output from the subtractor 94351 by 1 / M2 (M2 is input from the fifth control circuit 949) and then integrates it. The output of the integrator 94352 is input to the multiplier 94353 and the adder 94354. The multiplier 94353 multiplies the output of the integrator 94352 by the damping coefficient (Dg2) output from the fifth control circuit 949 and outputs the multiplication result to the subtractor 94351. The adder 94354 adds the output of the integrator 94352 and the power command value (Pref2), and outputs the sum as power target value information from the second mass system calculation circuit 9435.

[0240] The output of the power target generation circuit 943 is input to the power target value control circuit 946 and the fifth control circuit 949. Figure 19 shows the configuration of the power target value control circuit 946. The subtractor 9461 subtracts the measured power calculated by the second power calculation circuit 941 from the power target value output from the power target generation circuit 943, and outputs the subtraction result to the fourth PI control circuit 9462. The fourth PI control circuit 9462 performs PI control so that the output of the subtractor 9461 becomes zero, and outputs the execution result to the first switching circuit 947 as a control command value for the first DC / DC conversion circuit 93.

[0241] Returning to Figure 9, the first switching circuit 947 switches between the output of the second voltage target value control circuit 945 and the output of the power target value control circuit 946 based on a control signal output from the fifth control circuit 949. The fifth control circuit 949 outputs a control signal to select the output of the second voltage target value control circuit 945 when controlling the power converter for the power distribution system battery 9 in voltage control mode, and to select the output of the power target value control circuit 946 when controlling in power control mode. The output of the first switching circuit 947 is input to the current limiting circuit 948, and current limiting is performed when the output power of the first DC / DC converter 93 exceeds a predetermined value. In Embodiment 1, a PWM modulation circuit (not shown) in the current limiting circuit 948 performs PWM modulation on the current command value to which current limiting has been applied, and outputs the result to the first DC / DC converter 93.

[0242] Next, the detailed operation of the power conversion device 9 for the power distribution system battery will be explained using the flowchart shown in Figure 40. When control of the first DC / DC conversion circuit 93 is started, in S301, the fifth control circuit 949 initializes various parameters in the second control circuit 94. In S302, the fifth control circuit 949 sets the power command value to "zero" and the voltage command value to "1500V". In S303, the fifth control circuit 949 collects information from various voltage and current sensors. In S304, the fifth control circuit 949 starts controlling the first DC / DC conversion circuit 93.

[0243] Figure 41 is a detailed flowchart of the control of the first DC / DC conversion circuit 93. When control of the first DC / DC conversion circuit 93 is started, in S3041, the second power calculation circuit 941 reads the voltage (measurement result of voltmeter 96) and current (measurement result of ammeter 97) of the DC distribution system 21. In S3042, the second power calculation circuit 941 calculates the charge and discharge power of the DC distribution system 21. In S3043, the second power calculation circuit 941 checks whether or not to operate the power converter 9 for the distribution system battery in voltage control mode. In Embodiment 1, the control mode of the power converter 9 for the distribution system battery is notified from CEMS 3. In the case of voltage control mode (YES), in S3044, the second voltage target generation circuit 942 generates a DC voltage target value based on the drooping characteristic. As described above, the operation of the second voltage target generation circuit 942 (see Figures 11 to 13) is the same as that of the first voltage target generation circuit 682, so its operation will not be explained again.

[0244] The voltage target value based on the drooping characteristic generated by the second voltage target generation circuit 942 is input to the second voltage target value control circuit 945 and the fifth control circuit 949. When the voltage target value is input to the second voltage target value control circuit 945, it outputs a command value for the first DC / DC conversion circuit 93 to the first switching circuit 947 so that the voltage of the DC power distribution system 21 becomes the voltage target value. Based on the control signal output from the fifth control circuit 949, the first switching circuit 947 selects either the output of the second voltage target value control circuit 945 or the output of the power target value control circuit 946 and outputs it to the current limiting circuit 948. Therefore, when S3045 ends (voltage control mode), the first switching circuit 947 selects the output of the second voltage target value control circuit 945 and outputs it to the current limiting circuit 948. In S3048, if the current limiting circuit 948 determines that the measurement result of the ammeter 97 exceeds a predetermined current value, it limits the command value output to the first DC / DC conversion circuit 93. As described above, the current limiting circuit 948 applies PWM modulation to the limited command value and outputs a control signal to the first DC / DC conversion circuit 93.

[0245] In S3043, if the control mode of the power converter 9 for the power distribution system battery is power control mode (NO), the process proceeds to S3046. In S3046, the fifth control circuit 949 instructs the power target generation circuit 943 to generate a DC power target value based on the drooping characteristic.

[0246] The operation of the power target generation circuit 943 will be explained below using Figures 14 to 16. The power command value (Pref2) output from the fifth control circuit 949 is input to the subtractor 9431 and the second mass-point calculation circuit 9435. The subtractor 9431 subtracts the power command value (Pref2) from the calculation result of the charge / discharge power of the distribution system battery 8 calculated by the second power calculation circuit 941, and outputs the subtraction result to the second governor control circuit 9432. In Embodiment 1, the second governor control circuit 9432 uses a first-order lag system model as shown in equation (1).

[0247] Figure 15 shows the detailed configuration of the second governor control circuit 9432. The multiplier 94321 multiplies the output of the subtractor 9431 by -1 / Kgd2 output from the fifth control circuit 949 and outputs the multiplication result to the first-order lag circuit (1 / (1+s×Tg2)) 94322. The second limiter circuit 94323 limits the output of the first-order lag circuit 94322 to a predetermined range and outputs it from the second governor control circuit 9432. The adder 9433 in Figure 14 adds the output of the second governor control circuit 9432 and the voltage command value (Vref2) output from the fifth control circuit 949 and outputs the addition result to the subtractor 9434. The subtractor 9434 subtracts the output of the voltmeter 96 from the output of the adder 9433 and outputs the subtraction result to the second point mass arithmetic circuit 9435. In Embodiment 1, the second mass system calculation circuit 9435 uses a motion equation model as shown in equation (2).

[0248] Figure 16 shows the detailed configuration of the second point mass arithmetic circuit 9435. The subtractor 94351 subtracts the output of the subtractor 9434 from the output of the multiplier 94353 and outputs the subtraction result to the integrator 94352. The integrator 94352 multiplies the subtraction result output from the subtractor 94351 by 1 / M2 (M2 is input from the fifth control circuit 949) and then integrates it. The output of the integrator 94352 is input to the multiplier 94353 and the adder 94354. The multiplier 94352 multiplies the output of the integrator 94352 by the damping coefficient (Dg2) output from the fifth control circuit 949 and outputs the multiplication result to the subtractor 94351. The adder 94354 adds the output of the integrator 94352 and the power command value (Pref2), and outputs the sum as power target value information from the second mass system calculation circuit 9435.

[0249] The output of the power target generation circuit 943 is input to the power target value control circuit 946 and the fifth control circuit 949. In Embodiment 1, in S3046, the power target generation circuit 943 generates a power target value in the manner described above.

[0250] In S3047, the fifth control circuit 949 generates a current command value for the first DC / DC conversion circuit 93. Specifically, as described above, the power target value control circuit 946 in Figure 9 generates the current command value. Figure 19 shows the configuration of the power target value control circuit 946. The subtractor 9461 subtracts the measured power calculated by the second power calculation circuit 941 from the power target value output from the power target generation circuit 943, and outputs the subtraction result to the fourth PI control circuit 9462. The fourth PI control circuit 9462 performs PI control so that the output of the subtractor 9461 becomes zero, and outputs the execution result to the first switching circuit 947 as a control command value for the first DC / DC conversion circuit 93.

[0251] [Correction based on Rule 91 25.12.2025] As described above, the first switching circuit 947 in Figure 9 switches between the output of the second voltage target value control circuit 945 and the output of the power target value control circuit 946 based on the control signal output from the fifth control circuit 949. The fifth control circuit 949 outputs a control signal to select the output of the second voltage target value control circuit 945 when controlling the power converter 9 for the power distribution system battery in voltage control mode, and to select the output of the power target value control circuit 946 when controlling in power control mode. When S3047 in Figure 41 is completed (power control mode), the first switching circuit 947 selects the output of the power target value control circuit 946 and outputs it to the current limiting circuit 948. In S3048, the current limiting circuit 948 limits the command value of the input first DC / DC converter 93. Specifically, the current limiting circuit 948 limits the command value output to the first DC / DC conversion circuit 93 when the output current exceeds a predetermined value. As described above, the current limiting circuit 948 applies PWM modulation to the limited command value and outputs a control signal to the first DC / DC conversion circuit 93.

[0252] When S304 in Figure 40 is completed, in S305, the fifth control circuit 949 checks whether it has received a request to transmit measurement information from CEMS3. If it has received a transmission request from CEMS3 (YES), the process proceeds to S306. In S306, the fifth control circuit 949 outputs the measurement information stored in a memory (not shown) to the second communication interface circuit 95. When the second communication interface circuit 95 receives the measurement data from the fifth control circuit 949, it converts the measurement data into a predetermined format and sends it to CEMS3 via the communication line 22. When S306 is completed, or if the answer in S305 is NO, the process proceeds to S307. In S307, the fifth control circuit 949 checks whether it has received control information (voltage command value, power command value, information on drooping characteristics, etc.) from CEMS3. If it has not received the information (NO in S307), the process returns to S303. On the other hand, if a signal is received (YES in S307), the process proceeds to S308. In S308, the fifth control circuit 949 sets the power command value (Pref2), the voltage command value (Vref2), the control mode, and the droop characteristics (Kgd1, Tg1, M1, Dg1, Kgd2, Tg2, M2, Dg2) in registers within the fifth control circuit 949 (not shown). After that, the process returns to S303.

[0253] Next, the operation of the consumer PV power converter 13 will be explained using Figures 7 and 10. The consumer PV power converter 13 outputs the DC power output from the PV panel 12 installed at the consumer's home to the DC distribution system 21. The consumer PV power converter 13 outputs the power generated by the PV panel 12 to the DC distribution system 21. The consumer PV power converter 13 will be described in the case where two types of control are implemented: MPPT control, which extracts the maximum amount of power generated by the PV panel 12, and PV voltage control, which controls the output voltage of the PV panel 12 to control the amount of power generated.

[0254] Figure 7 is a block diagram of the power conversion device 13 for consumer PV. The voltmeter 131 measures the output voltage of the PV panel 12. The ammeter 132 measures the output current from the PV panel 12. The voltmeter 136 measures the voltage of the DC distribution system 21. The ammeter 137 measures the output current to the DC distribution system 21. The DC power generated by the PV panel 12 is input to the second DC / DC conversion circuit 133. The second DC / DC conversion circuit 133 outputs DC power to the DC distribution system 21 based on the command value output from the third control circuit 134. The third control circuit 134 stores the measurement data from the voltmeters 131 and 136, the measurement data from the ammeters 132 and 137, and information such as the control method of the PV panel 12 in a memory not shown in the figure. The third control circuit 134 transmits the measurement data to the communication line 22 via the third communication interface circuit 135, based on the measurement data output request from the CEMS 3.

[0255] The operation of the third control circuit 134 will be explained below using Figure 10. Figure 10 is a block diagram illustrating the configuration of the third control circuit 134 that controls the second DC / DC conversion circuit 133 in the consumer PV power converter 13 shown in Figure 7. Referring to Figure 10, the third control circuit 134 comprises an MPPT (Maximum Power Point Tracking) control circuit 1341, a PV voltage control circuit 1342, a second switching circuit 1343, and a sixth control circuit 1344. The MPPT control circuit 1341 performs so-called maximum power point tracking control based on the measured values ​​of the voltmeter 131 and the ammeter 132. That is, the MPPT control circuit 1341 searches for the maximum power point of the PV panel 12 in order to extract the maximum amount of power generated from the PV panel 12. Specifically, the MPPT control circuit 1341 generates a control command value for a second DC / DC conversion circuit 133, which controls the DC voltage measured by the voltmeter 131 to the voltage corresponding to the maximum power point.

[0256] The PV voltage control circuit 1342 generates a control command value for the second DC / DC conversion circuit 133 in order to maintain the DC voltage of the DC distribution system 21 at a predetermined target voltage, based on the measurement value of the voltmeter 136. The sixth control circuit 1344 outputs control parameters and control target values ​​to the MPPT control circuit 1341 and the PV voltage control circuit 1342, and also manages the power generation status of the PV panel 12. The sixth control circuit 1344 further outputs a control signal for the second switching circuit 1343. The second switching circuit 1343 selectively outputs one of the outputs of the MPPT control circuit 1341 and the PV voltage control circuit 1342 as the control command value for the second DC / DC conversion circuit 133, according to the control signal from the sixth control circuit 1344.

[0257] The second DC / DC conversion circuit 133 is controlled in either MPPT mode or PV voltage control mode. In MPPT mode, the second switching circuit 1343 outputs a control command value generated by the MPPT control circuit 1341. In PV voltage control mode, the second switching circuit 1343 is controlled to output a control command value generated by the PV voltage control circuit 1342. The sixth control circuit 1344, for example, switches the control of the PV panel 12 from MPPT control to PV voltage control when the voltage of the DC distribution system 21 exceeds a predetermined value, thereby suppressing the rise in the voltage at the grid connection point (receiving point) of the DC distribution system 21. Furthermore, if a control mode is received from CEMS3, or if the voltage control is able to suppress the rise in the grid connection point (receiving point) voltage of the DC power distribution system 21 to a predetermined voltage and maintain it for a predetermined time, in Embodiment 1, the second switching circuit 1343 switches the control of the PV panel 12 from PV voltage control to MPPT control. MPPT control, or PV voltage control, is a control method for power conversion devices used in solar power generation installed in ordinary homes.

[0258] Finally, the concept of the control mode for the power converter 9 for the distribution system battery will be explained. When configuring the DC distribution system 21, at least one converter operating in voltage control mode is required to manage the system voltage of the DC distribution system 21. Therefore, when selecting a converter operating in voltage control mode, it is necessary to consider that when load fluctuations or fluctuations in the amount of power generated by renewable energy equipment such as PV occur, the converter operating in voltage control mode will be the first to supply excess or insufficient power, and to ensure that the converter capacity is sufficient to cover the expected magnitude of load fluctuations or power generation fluctuations. Therefore, when selecting a converter operating in voltage control mode, it is necessary to select a converter with a large capacity, or multiple converters whose total converter capacity is large enough to cover load fluctuations or power generation fluctuations. When selecting the power converter 9 for the distribution system battery, it is desirable to prioritize the selection of a power converter 8 with a large battery capacity for the distribution system. It is important to note that the transient response during load fluctuations or power generation fluctuations differs mainly between voltage control mode and power control mode, and it is necessary to select the control mode by estimating the convergence value in the steady state.

[0259] Once the selection of converters operating in voltage control mode is complete according to the above procedure, the operating mode of the remaining converters is determined. Converters connected to power sources whose output power cannot be controlled (e.g., PV or wind power generators) are not given a drooping characteristic. Therefore, Embodiment 1 focuses on the power converter 9 for distribution system batteries. The other converters (power converter 9 for distribution system batteries) may all be controlled in voltage control mode, or all may be controlled in power control mode.

[0260] The following describes the approach to selecting between voltage control mode and power control mode. As mentioned above, a characteristic of voltage control mode is that it manages the voltage at the grid connection point itself. If the voltage of the DC distribution system 21 deviates from the voltage management range (Vmax to Vmin) shown in Figure 20, the converter cannot output the deviated DC voltage, which may cause overcurrent and other problems, leading to a shutdown. On the other hand, in power control mode, the output power is limited by the upper limit Pmax and the lower limit Pmin (converter capacity) shown in Figure 21, but operation continues even if the voltage of the DC distribution system 21 deviates from the range of Vmax or Vmin. However, power control mode cannot handle instantaneous surplus or deficit power supply when sharp load fluctuations or power generation fluctuations occur. Therefore, in Embodiment 1, the CEMS 3 compares the load fluctuation amount of the customer load 11 within the customer load group 10, the power generation fluctuation amount of the PV panel 12, and the converter capacity of the corresponding power converter for the distribution system battery 9. CEMS3 selects voltage control mode if the converter capacity of the power converter 9 for distribution system batteries is sufficiently large for the fluctuations within the customer load group 10, and selects power control mode if it is difficult to do so. Note that the selection between voltage control mode and power control mode is not limited to the above. When creating an operation plan, CEMS3 estimates the voltage fluctuation range at the grid connection point of each power converter 9 for distribution system batteries when load fluctuations or power generation fluctuations occur, based on the direction and magnitude of the power flow current. If the estimated voltage fluctuation range deviates from a predetermined range (for example, about ±5% of the reference voltage), CEMS3 may select power control mode, and if it does not exceed this range, CEMS3 may select voltage control mode.

[0261] Since Embodiment 1 is configured as described above, when the CEMS 3 creates an operation plan (power command value (Pref) and voltage command value (Vref)) for the power converter 9 for the distribution system battery, it estimates the power flow current based on the predicted power consumption of the customer loads 11 in the customer load group 10 and the predicted power generation amount of the PV panel 12. Based on the estimated impedance of the DC distribution system 21 and the drooping characteristics of each power converter 9 for the distribution system battery, the CEMS 3 estimates the grid connection point voltage of the DC distribution system 21 for the power converter 9 for the distribution system battery and generates a power command value so that the grid connection point voltage falls within a predetermined range. This allows the connection point voltage of each power converter 9 for the distribution system battery to the DC distribution system 21 to be controlled to fall within a predetermined voltage range, and also allows for smooth power flow control even when load fluctuations occur. Furthermore, CEMS3 estimates the voltage fluctuation range at the grid connection point of each converter to the DC distribution system 21 based on the power flow estimation results of the DC distribution system 21 and the estimation results of the power supply and demand fluctuation range of each customer load group 10, and determines the drooping characteristics of each converter based on the estimation results. This makes it possible to control the differential power so that it is approximately the same as the allocation ratio assumed when creating the operation plan, even when demand fluctuations occur. For example, it is possible to control it so that the SOC of the distribution system battery 8 is approximately the same.

[0262] In Embodiment 1, the case where the system is connected to the AC distribution system 20b via the AC / DC converter 6 was described, but the system is not limited to this. Even if the AC main power grid experiences a power outage and the DC distribution system 21 is disconnected from the AC main power grid using the switch 5, the same effect can be achieved in an independent system by configuring at least one of the power converters 9 for distribution system batteries, other than the AC / DC converter 6, to operate in voltage control mode to manage the DC voltage of the DC distribution system 21. If at least one of the power converters 9 for distribution system batteries installed in the DC distribution system 21 is configured to operate in voltage control mode, then even if the main power grid experiences a power outage due to an accident, if the DC distribution system 21 is disconnected from the main power grid using the switch 5 immediately after the accident is detected, the voltage of the DC distribution system 21 can be maintained by the power converters 9 for distribution system batteries operating in voltage control mode, allowing for a seamless transition to an independent system. Furthermore, when transitioning to an independent power system, the AC / DC converter 6 can be controlled to be disconnected from the DC power distribution system 21 by a gate block or a DC switch (not shown).

[0263] Furthermore, in Embodiment 1, by providing the AC / DC converter 6 and the power converter 9 for the distribution system battery with a power-voltage droop characteristic (voltage control mode) or a voltage-power droop characteristic (power control mode), a virtual inertial force can be applied to the DC distribution system 21. As a result, even when load fluctuations or fluctuations in the amount of power generated by renewable energy equipment occur, the converters with droop characteristics supply excess or insufficient power autonomously and cooperatively (without communication, etc.), thereby maintaining the voltage of the DC distribution system 21 within an appropriate range. In addition, by appropriately arranging distributed power sources whose output power can be controlled, such as the power converter 9 for the distribution system battery controlled by a power-voltage droop characteristic (voltage control mode) or a voltage-power droop characteristic (power control mode), excess or insufficient power immediately after load fluctuations or power generation fluctuations can be supplied to the DC distribution system 21 without concentrating it on a single distributed power source.

[0264] Embodiment 2. In Embodiment 1, when the CEMS 3 creates an operation plan (power command value (Pref) and voltage command value (Vref)) for the AC / DC converter 6 and each power conversion device 9 for distribution system batteries, it is configured to estimate the power flow current based on the predicted power consumption results of the customer loads 11 in the customer load group 10 and the predicted power generation results of the PV panels 12, and to generate the plan based on the estimated voltage at the grid connection point of each converter to the DC distribution system 21 using the estimated impedance of the DC distribution system 21. Furthermore, in Embodiment 1, the CEMS 3 estimates the demand fluctuation range of the customer load group 10 and estimates the voltage fluctuation range at the grid connection point of each converter to the DC distribution system 21 based on the estimated demand fluctuation range. The CEMS 3 is configured to create the droop characteristics of each converter based on the estimated voltage fluctuation range.

[0265] Embodiment 2 describes a case in which the voltage command value (Vref) is controlled in addition to the power command value (Pref) (modification of the operation plan 1: see Figure 26), and a dead zone is introduced in the drooping characteristics applied to each converter. Below, Embodiment 2 will be described focusing on the operation of the parts that differ from Embodiment 1 (only the operation of CEMS3). Note that Embodiment 2 differs from Embodiment 1 only in the operation of CEMS3 to create (including modification) the operation plan (power command value (Pref), voltage command value (Vref), and drooping characteristics), so the operation of CEMS3 will be described focusing on the operation plan creation operation. The circuit configurations of CEMS3, AC / DC converter 6, power converter for distribution system battery 9, and power converter for consumer PV 13 are the same as in Embodiment 1 (Figures 2 to 10, 17 to 19), so a detailed explanation will not be repeated.

[0266] The detailed operation of CEMS3 will be explained below using Figures 2 to 4 and Figures 42 to 54. Figure 42 is a diagram showing an example of the drooping characteristics of a converter operating in voltage control mode according to Embodiment 2. As shown in Figure 42, Embodiment 2 describes the case in which a dead zone is provided in the drooping characteristics. In the example of voltage control mode shown in Figure 42, the power command value (Pref) was set to zero for the sake of simplicity. As shown in Figure 42, by operating the converter without changing the output voltage within the dead zone width range of the output power from the converter, minute demand fluctuations in the consumer load group 10 are dealt with by the output from nearby converters. This makes it possible to configure the system so as not to impose unnecessary disturbances on the DC distribution system 21. Similarly, Figure 43 is a diagram showing an example of the drooping characteristics of a converter operating in power control mode. As shown in Figure 43, by operating the converter without changing the output power within the dead zone width range of the output power from the converter, minute demand fluctuations in the consumer load group 10 are dealt with by the output from the converter operating in voltage control mode. This makes it possible to configure the system so as not to impose unnecessary disturbances on the DC distribution system 21.

[0267] The operation of the power converter management device (CEMS3) that manages the converter having the drooping characteristics shown in Figure 42 or Figure 43 will be described below. Figure 44 is a control processing flowchart of the CEMS3 shown in Figure 1. In Figure 44, when processing starts, in S100, the operation plan creation circuit 34 in the CEMS3 starts estimating the system impedance, similar to Embodiment 1. The system impedance estimation flowchart in S100 is the same as in Embodiment 1, so a detailed explanation will not be repeated. In S101, the operation plan creation unit management circuit 346 shown in Figure 3 within the operation plan creation circuit 34 shown in Figure 2 checks whether there has been a request for output of measurement data from DSO2. If there is a request for output, processing proceeds to S102. In S102, the operation plan creation unit management circuit 346 collects the latest measurement information by transmitting a request for output of measurement data to the AC / DC converter 6, the power conversion devices 9a to 9n for the distribution system battery, and the customer load groups 10a to 10n via the communication line 22. The collected measurement information is temporarily stored in the memory circuit 32 via the communication circuit 31. At the same time, the operation plan creation unit management circuit 346 generates 30 minutes of data by combining the collected measurement data with the 25 minutes of data collected at 5-minute intervals stored in the memory circuit 32, and updates the database 351 for predicting power generation for PV panels 12a to 12n and the database 352 for predicting power consumption for customer loads 11a to 11n within the operation plan creation circuit 346. Then, in S103, the operation plan creation unit management circuit 346 transmits the generated 30 minutes of measurement data (power consumption of each customer load 11a to 11n, power generation amount of PV panels 12a to 12n, charge / discharge power of distribution system batteries 8a to 8n) and information such as SOC and SOH of distribution system batteries 8a to 8n to DSO2 via the communication circuit 31. Then, as in Embodiment 1, once the transmission of measurement data is complete, the memory circuit 32 erases the measurement data collected during the 30-minute period. If the transmission of measurement data is completed in S103, or if the answer in S101 is NO, the process proceeds to S104. In S104, the operation plan creation unit management circuit 346 checks whether or not it has received a demand plan notification from DSO2. If it has been received, the process proceeds to S140. In S140 (creation of operation plan 2), the operation plan is created.In Embodiment 2, similar to Embodiment 1, the DSO2 will notify the CEMS3 of the power supply and demand plan for the power supplied from the main grid to the DC distribution system 21 in 30-minute cycles for a 24-hour period.

[0268] Figure 45 is a detailed operation flowchart of the operation plan creation process (operation plan creation 2) in S140 shown in Figure 44. In Figure 45, when operation plan creation is started, in S1051 the operation plan creation unit management circuit 346 performs power generation prediction for PV panels 12a to 12n. In S1052 the operation plan creation unit management circuit 346 predicts the power consumption of customer loads 11a to 11n. In S1053 the operation plan creation unit management circuit 346 starts creating a demand plan. In S1054 the operation plan creation unit management circuit 346 determines the charge and discharge power of distribution system batteries 8a to 8n. The operations for predicting the amount of power generated by the PV panel 12 in S1051, predicting power consumption in S1052, creating a demand plan in S1053, and determining the charge and discharge power of the distribution system batteries 8a to 8n in S1054 are the same as in Embodiment 1, so no further explanation will be given.

[0269] In S1055, the operation plan creation unit management circuit 346 within the operation plan creation circuit 34 reads out the estimated impedances of the DC distribution system impedances 7a to 7n of the DC distribution system 21. In S1056, the power flow current estimation circuit 347 calculates the power flow current in the DC distribution system 21. Specifically, the power flow current estimation circuit 347 calculates the power flowing through each distribution system impedance 7a to 7n based on the estimated surplus and deficit power for each customer load group 10 calculated in S1054, the charge and discharge power (Pref) from each distribution system battery power converter 9, and the demand power (Pref) supplied from the AC / DC converter 6. The power flow current estimation circuit 347 calculates the current value from the power calculation result.

[0270] Once the calculation of the power flow current through the DC distribution system 21 is completed in S1056, the process proceeds to S1070. In S1070, the operation plan creation unit management circuit 346 predicts the voltage values ​​at the interconnection points of each power conversion device 9 for the distribution system battery in the DC distribution system 21 (voltage prediction at each receiving point 2). The voltage prediction at each receiving point 2 in S1070 is performed below using Figure 46. Figure 46 is a flowchart of the voltage prediction at each receiving point 2. In Figure 46, when S1070 starts, in S10701, the operation plan creation unit management circuit 346 in the operation plan creation circuit 34 collects power command value (Pref) and voltage command value (Vref) information for the power conversion devices 9a to 9n for the distribution system battery. In S10571, the operation plan creation unit management circuit 346 instructs the power flow current estimation circuit 347 to read the droop characteristic information of the AC / DC converter 6 (via the operation plan creation unit management circuit 346) from the memory circuit 32. In Embodiment 2, the droop characteristic is not configured as the governor control circuit and the mass-point system residual power circuit shown in Figures 11-13 (voltage control mode) and 14-16 (power control mode), but rather the dead zone-related information is the coordinates of the black dots shown in Figure 42 or Figure 43 (labeled A, B, C, D, E, F, G, H in the figures). In Embodiment 2, the first voltage target generation circuit 682, the second voltage target generation circuit 942, and the power target generation circuit 943 in each converter are configured as rewritable memory tables.

[0271] In S10702, the power current estimation circuit 347 instructs the operation plan creation unit management circuit 346 to read the power command value information (Pref) and voltage command value information (Vref) of the AC / DC converter 6.

[0272] In S10573, the power flow current estimation circuit 347 calculates the output voltage (Vref) of the AC / DC converter 6 based on the drooping characteristics of the AC / DC converter 6 collected in S10571 and the power command value and voltage command value of the AC / DC converter 6 collected in S10702. In Embodiment 1, the output voltage (Vref) of the AC / DC converter 6 is set to the reference voltage (1500V). In S10574, the power flow current estimation circuit 347 selects the power converter 9a for the distribution system battery located one downstream of the AC / DC converter 6.

[0273] When S10574, or S10581 (described later), is completed, in S10575, the power flow current estimation circuit 347 collects the control mode and droop characteristic information of the first DC / DC conversion circuit 93 in the selected power distribution system battery power converter 9. Specifically, the power flow current estimation circuit 347 reads the control mode and droop characteristic information of the first DC / DC conversion circuit 93 from the memory circuit 32 via the operation plan creation unit management circuit 346. The two types of control modes of the first DC / DC conversion circuit 93 in the power distribution system battery power converter 9 have different droop characteristics, but they are the same as in Embodiment 1, so no explanation is given. In S10703, the power flow current estimation circuit 347 acquires power command value (Pref) and voltage command value (Vref) information to be notified to the first DC / DC conversion circuit 93 in the selected power distribution system battery power converter 9. Then, in S10577, the power flow current estimation circuit 347 estimates the power flow current and outputs the estimation result to the grid voltage estimation circuit 348. Based on the power flow current estimation result and the impedance estimation results of the distribution system impedances 7a to 7n read out in S1055 (see Figure 45), the grid voltage estimation circuit 348 calculates the voltage drop value at the grid connection point (receiving point) of the DC distribution system 21 of the selected power conversion device 9 for distribution system batteries. In S10578, the power flow current estimation circuit 347 calculates the connection point voltage of the first DC / DC conversion circuit 93 in the selected power conversion device 9 for distribution system batteries with the DC distribution system 21 and outputs the calculation result to the operation plan creation unit management circuit 346. In S10579, the power flow current estimation circuit 347 uses the interconnection point voltage of the DC distribution system 21 calculated in S10578 and the drooping characteristics collected in S10575 to calculate the charge / discharge power output from the first DC / DC conversion circuit 93 in the selected power conversion device 9 for the distribution system battery. Based on the calculated charge / discharge power, the power flow current estimation circuit 347 corrects the calculation result of the power flow current 1 of the DC distribution system 21.

[0274] In S10580, the operation plan creation unit management circuit 346 checks whether the estimation of the output voltage of the first DC / DC conversion circuit 93 in all of the power conversion devices 9 for distribution system batteries has been completed. If not all have been completed (NO), the process proceeds to S10581. In S10581, the operation plan creation unit management circuit 346 selects the first DC / DC conversion circuit 93 in the power conversion device 9 for distribution system batteries that is connected downstream of the power conversion device 9 for distribution system batteries. After that, the process returns to S10575. If the answer in S10580 is YES, the operation plan creation unit management circuit 346 terminates S1057.

[0275] When S1070 is completed, in S1058, the operation plan creation unit management circuit 346 checks whether the estimated values ​​of the interconnection point voltages (receiving point voltages) of all power converters 9 for distribution system batteries estimated in S1070 with the DC distribution system 21 fall within a predetermined range. Embodiment 2 describes a case where, similar to Embodiment 1, the voltage range of the DC distribution system 21 is set to, for example, the reference voltage (1500V) ± 0.1 × reference voltage (allowable voltage range), and the predetermined range is set to, for example, the reference voltage ± 0.075 × reference voltage (2.5% is a margin when load fluctuations occur). This is set narrower than the allowable voltage range, taking into account that the voltage of the DC distribution system 21 changes due to the drooping characteristic from the voltage range of the DC distribution system 21. As shown in Figure 42 or Figure 43, the upper limit voltage is Vrange_max and the lower limit voltage is Vrange_min. If the answer in S1058 is NO, then in S1071, a review of the voltage and power command value 1 of the power distribution system battery 8 is performed.

[0276] Figure 47 is a flowchart of the review of the voltage and power command values ​​of the distribution system battery 8 in S1071. When S1071 is started in Figure 47, in S1075, the operation plan creation unit management circuit 346 reviews the voltage command value of the distribution system battery 8. Figures 48A and 48B are flowcharts of the review of the voltage command value of the distribution system battery 8 in S1075. Figure 48C is a diagram showing an example of voltage command value creation. When S1075 is started in Figures 48A and 48B, in S10751, the operation plan creation unit management circuit 346 detects the maximum value (Vp_max) from the predicted voltage values ​​of the connection points between the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery and the DC distribution system 21, which were predicted in S1070. Similarly, in S10752, the operation plan creation unit management circuit 346 detects the minimum value (Vp_min) from the predicted voltage values ​​of the connection points between the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery, which were predicted in S1070, and the DC distribution system 21. In S10753, the operation plan creation unit management circuit 346 uses the detected Vp_max and Vp_min to determine whether the lower limit voltage of the converters (AC / DC converter 6 and power conversion devices 9a to 9n for the distribution system battery) has deviated. In Embodiment 2, if there are converters whose interconnection point voltage with the DC distribution system 21 exceeds the upper limit voltage and converters whose interconnection point voltage falls below the lower limit voltage, the voltage of the converter that detected Vp_max is set as the upper limit voltage (Vrange_max), and the interconnection point voltage of the other converters with the DC distribution system 21 is set as "estimated value - (Vp_max - Vrange_max)" and the processing from S10754 onwards is performed. In Embodiment 2, for the sake of simplicity, we assume that the power flow in the DC distribution system 21 is either smooth (current flows from the AC / DC converter 6 to the power converter 9n for the distribution system battery) or reverse (current flows from the power converter 9n for the distribution system battery to the AC / DC converter 6). Note that even if the forward and reverse power flow switches in the middle of the DC distribution system 21, this approach can be followed.

[0277] If the answer in S10753 is YES, or if the above-described process is performed, the process proceeds to S10754. In S10754, the operation plan creation unit management circuit 346 checks whether the power flow in the DC distribution system 21 is forward or not. If it is forward, the process proceeds to S10755. In S10755, the operation plan creation unit management circuit 346 selects the terminal DC / DC converter (power converter for distribution system battery 9n). In S10756, the operation plan creation unit management circuit 346 sets the voltage command value of the selected power converter for distribution system battery 9n to "lower limit voltage of system voltage (Vrange_min) + ζ". In Embodiment 2, ζ is calculated as "ζ = {(Vrange_max - Vrange_min) - (Vp_max - Vp_min)} / 2" (see Figure 48C). In S10757, the operation plan creation unit management circuit 346 selects the DC / DC converter one upstream from the terminal DC / DC converter (power converter for distribution system battery 9m). In S10758, the operation plan creation unit management circuit 346 calculates the voltage drop (ΔV_diff) based on the power flow current prediction result.

[0278] Specifically, the operation plan creation unit management circuit 346 calculates "ΔV_diff = Vp(k) - Vp(k-1)" where Vp(k) is the grid connection point voltage of the currently selected DC / DC converter and Vp(k-1) is the grid connection point voltage of the previously selected DC / DC converter. In S10759, the operation plan creation unit management circuit 346 calculates "voltage command value (Vref(k)) = voltage command value of the DC / DC converter one step downstream (the previously selected one step) (Vref(k-1)) + ΔV_diff". In S10760, the operation plan creation unit management circuit 346 determines whether the voltage command value exceeds a predetermined upper limit voltage (Vrange_max). If the voltage command value exceeds the predetermined upper limit voltage (YES), the process proceeds to S10761. In S10761, the operation plan creation unit management circuit 346 sets the voltage command value to a predetermined upper limit voltage (Vrange_max). In Embodiment 2, as described above in S10760 and S10761, if the voltage command value exceeds the predetermined upper limit voltage, it is limited to the upper limit voltage, but this is not the only option; it may also be output as is without limiting it to the upper limit voltage. If S10760 is NO, or when S10761 is completed, the process proceeds to S10762. In S10762, the operation plan creation unit management circuit 346 checks whether the correction of the voltage command values ​​of all converters has been completed. If it has been completed (YES), the distribution system battery voltage command value review flowchart (S1075) is terminated. On the other hand, if it has not been completed (NO), in S10763, the operation plan creation unit management circuit 346 selects the converter one upstream from the currently selected converter. After that, the process returns to S10758.

[0279] Returning to S10754, if the power flow is reverse (NO), in S10775, the operation plan creation unit management circuit 346 selects the AC / DC converter 6. In S10776, the operation plan creation unit management circuit 346 sets the voltage command value of the selected AC / DC converter 6 to "lower limit voltage of the system voltage (Vrange_min) + η". In Embodiment 2, the operation plan creation unit management circuit 346 calculates this as "η = {(Vrange_max - Vrange_min) - (Vp_max - Vp_min)} / 2". In S10777, the operation plan creation unit management circuit 346 selects the DC / DC converter one downstream of the AC / DC converter 6 (power conversion device 9a for distribution system battery). In S10778, the operation plan creation unit management circuit 346 calculates the voltage drop (ΔV_diff) based on the power flow current prediction result.

[0280] Specifically, the operation plan creation unit management circuit 346 calculates "ΔV_diff = Vp(k) - Vp(k-1)" where Vp(k) is the grid connection point voltage of the currently selected DC / DC converter and Vp(k-1) is the grid connection point voltage of the previously selected DC / DC converter. In S10779, the operation plan creation unit management circuit 346 calculates "voltage command value (Vref(k)) = voltage command value of the upstream (previously selected) DC / DC converter (Vref(k-1)) + ΔV_diff". In S10780, the operation plan creation unit management circuit 346 determines whether the voltage command value exceeds a predetermined upper limit voltage (Vrange_max). If the voltage command value exceeds the predetermined upper limit voltage (YES), the process proceeds to S10781. In S10781, the operation plan creation unit management circuit 346 sets the voltage command value to a predetermined upper limit voltage (Vrange_max). In Embodiment 2, as described above in S10780 and S10781, if the voltage command value exceeds the predetermined upper limit voltage, it is limited to the upper limit voltage, but this is not the only option; it may also be output as is without limiting it to the upper limit voltage. If S10780 is NO, or when S10781 is completed, the process proceeds to S10782. In S10782, the operation plan creation unit management circuit 346 checks whether the correction of the voltage command values ​​of all converters has been completed. If it has been completed (YES), the distribution system battery voltage command value review flowchart (S1075) is terminated. On the other hand, if it has not been completed (NO), the process proceeds to S10783. In S10783, the operation plan creation unit management circuit 346 selects the converter one downstream of the currently selected converter. After that, the process returns to S10778.

[0281] In S10753, if the voltage command value does not deviate from the lower limit voltage, the process proceeds to S10793. In S10793, the operation plan creation unit management circuit 346 checks whether the voltage command value deviates from (exceeds) the upper limit voltage (Vrange_max). If it does not deviate from the upper limit voltage (NO), the process proceeds to S1075 in Figure 47. In S1075, the operation plan creation unit management circuit 346 determines that no correction of the voltage command value is necessary and terminates the distribution system battery voltage command value review flowchart (S1075).

[0282] On the other hand, if the voltage deviates from the upper limit in S10793 (YES), the process proceeds to S10794. In S10794, the operation plan creation unit management circuit 346 checks whether the tidal current is favorable. If the tidal current is favorable (YES), the process proceeds to S10795. In S10795, the operation plan creation unit management circuit 346 selects the AC / DC converter 6. In S10796, the operation plan creation unit management circuit 346 sets the voltage command value of the selected AC / DC converter 6 to "upper limit voltage of the system voltage (Vrange_max) - η". In Embodiment 2, this is calculated as "η = {(Vrange_max - Vrange_min) - (Vp_max - Vp_min)} / 2". In S10797, the operation plan creation unit management circuit 346 selects the DC / DC converter (power conversion device 9a for distribution system battery) one downstream of the AC / DC converter 6. In S10798, the operation plan creation unit management circuit 346 calculates the voltage drop (ΔV_diff) based on the power flow current prediction result.

[0283] Specifically, the operation plan creation unit management circuit 346 calculates "ΔV_diff = Vp(k) - Vp(k-1)" where Vp(k) is the grid connection point voltage of the currently selected DC / DC converter and Vp(k-1) is the grid connection point voltage of the selected DC / DC converter. In S10799, the operation plan creation unit management circuit 346 calculates "voltage command value (Vref(k)) = voltage command value (Vref(k-1)) of the DC / DC converter one step upstream (the one selected previously) + ΔV_diff". In S10800, the operation plan creation unit management circuit 346 determines whether the voltage command value is less than a predetermined lower limit voltage (Vrange_min). If the voltage command value is less than the predetermined lower limit voltage (YES), the process proceeds to S10801. In S10801, the operation plan creation unit management circuit 346 sets the voltage command value to a predetermined lower limit voltage (Vrange_min). In Embodiment 2, as described above in S10820 and S10821, if the voltage command value is less than the predetermined lower limit voltage, it is limited to the lower limit voltage, but it is not limited to this, and it may be output as is without limiting it to the lower limit voltage. If S10800 is NO, or when S10801 is completed, the process proceeds to S10802. In S10802, the operation plan creation unit management circuit 346 checks whether the correction of the voltage command values ​​of all converters has been completed. If it has been completed (YES), the distribution system battery voltage command value review flowchart (S1075) is completed. On the other hand, if it has not been completed (NO), the process proceeds to S10803. In S10803, the operation plan creation unit management circuit 346 selects the converter one downstream of the currently selected converter. After that, the process returns to S10798.

[0284] In S10794, the operation plan creation unit management circuit 346 checks whether the power flow in the DC distribution system 21 is forward or reverse. If it is reverse (NO), the process proceeds to S10815. In S10815, the operation plan creation unit management circuit 346 selects the terminal DC / DC converter (power converter for distribution system battery 9n). In S10816, the operation plan creation unit management circuit 346 sets the voltage command value of the selected power converter for distribution system battery 9n to "upper limit voltage of system voltage (Vrange_max) - ζ". In Embodiment 2, it is calculated as "ζ = {(Vrange_max - Vrange_min) - (Vp_max - Vp_min)} / 2". In S10817, the operation plan creation unit management circuit 346 selects the DC / DC converter one upstream from the terminal DC / DC converter (power converter for distribution system battery 9m). In S10818, the operation plan creation unit management circuit 346 calculates the voltage drop (ΔV_diff) based on the power flow current prediction result.

[0285] Specifically, the operation plan creation unit management circuit 346 calculates "ΔV_diff = Vp(k) - Vp(k-1)" using Vp(k) as the grid connection point voltage of the currently selected DC / DC converter and Vp(k-1) as the grid connection point voltage of the previously selected DC / DC converter. In S10819, the operation plan creation unit management circuit 346 calculates "voltage command value (Vref(k)) = voltage command value (Vref(k-1)) of the DC / DC converter one step downstream (the previously selected one step) + ΔV_diff". In S10820, the operation plan creation unit management circuit 346 determines whether the voltage command value is less than a predetermined lower limit voltage (Vrange_min). If the voltage command value is less than the predetermined lower limit voltage (YES), the process proceeds to S10821. In S10821, the operation plan creation unit management circuit 346 sets the voltage command value to a predetermined lower limit voltage (Vrange_min). In Embodiment 2, as described above, in S10820 and S10821, if the voltage command value is less than the predetermined lower limit voltage, it is limited to the lower limit voltage, but it is not limited to this, and it may be output as...

Claims

A power converter management device installed in a DC power distribution system and managing a plurality of power converters having a drooping characteristic that exchange DC power with the DC power distribution system, A power converter management device comprising: a control parameter generation circuit configured to estimate the voltage fluctuation range at the connection point between each power converter and the DC distribution system when the power flow or current flowing through the DC distribution system changes, and to generate the drooping characteristics of each power converter based on the voltage fluctuation range at the connection point between each power converter and the DC distribution system. 　 The power converter management device according to claim 1, further comprising: an operation plan creation circuit configured to estimate the power flow or power flow current based on the voltage measurement results at the interconnection points of the DC distribution system managed by each power converter, at least one of the current measurement results and power measurement results output by each power converter, and the demand power consumed by each consumer. 　 The power converter management device according to claim 2, wherein the operation plan creation circuit is configured to predict the power generated by energy-generating equipment connected to the DC power distribution system based on weather forecast information, and to predict the power demand of customer loads connected to the DC power distribution system, and to generate power command values ​​or current command values ​​for each power converter based on the surplus or deficit power, which is the difference between the predicted power generated and the predicted power demand. 　 The aforementioned multiple power converters include power converters to which storage batteries are connected. The power converter management device according to claim 3, wherein the operation plan creation circuit is configured to generate the power command value or the current command value of the power converter to which the battery is connected, based on the excess or insufficient power and the amount of power charged to the battery. 　 The power converter management device according to claim 4, wherein a group of consumer loads is composed of a plurality of energy-generating devices and a plurality of consumer loads managed by the power converter having the drooping characteristic, and the operation plan creation circuit is configured to predict the power generated by the energy-generating devices and the power demanded by the consumer loads on a unit basis of the group of consumer loads. 　 The power converter management device according to any one of claims 3 to 5, wherein the operation plan creation circuit is configured to estimate the power flow or power flow current based on the voltage command value of each power converter, either one or both of the power command value and current command value of each power converter, the predicted power generation result of the energy creation equipment, and the predicted power demand result of the customer load. 　 The power converter management device according to any one of claims 2 to 6, wherein the operation plan creation circuit is configured to estimate the impedance of the DC distribution system between each power converter based on the estimation result of the power flow or power flow current and the voltage measurement result of the interconnection point of each power converter with the DC distribution system. 　 The power converter management device according to any one of claims 2 to 6, wherein the operation plan creation circuit is configured to estimate the impedance of the DC distribution system between each power converter based on the system information of the DC distribution system and the impedance information of the transmission and distribution lines. 　 The control parameter generation circuit is configured to estimate the voltage fluctuation range at the connection point between the power converter and the DC distribution system when the power current changes, based on the estimation result of the impedance of the DC distribution system. The power converter management device according to claim 7 or 8. 　 The power converter management device according to any one of claims 2 to 9, wherein the operation plan creation circuit is configured to use a first drooping characteristic having power-voltage characteristics when the control mode of the power converter is a voltage command value control mode for controlling the DC voltage of the DC distribution system, and to use a second drooping characteristic having voltage-power characteristics when the control mode of the power converter is a power command value control mode for controlling the value of power or current output by the power converter. 　 The power converter management device according to claim 10, wherein the control parameter generation circuit generates the drooping characteristics of the power converter using at least one of the control mode of the power converter, the converter capacity of the power converter, the estimated impedance of the DC distribution system, the estimated voltage fluctuation range at the connection point with the DC distribution system, the predicted power generation of the energy creation equipment, the predicted power demand of the customer load, and the amount of charge of the battery when the power converter is connected to a battery. 　 The power converter management device according to claim 3, wherein the control parameter generation circuit controls the power converters connected to a battery to generate droop characteristics such that, when a fluctuation in power supply and demand occurs, the allocation of the differential power to each power converter is approximately equal to the ratio of the power command values, based on the voltage fluctuation range at the connection point of each power converter with the DC power distribution system. 　 The power converter management device according to any one of claims 2 to 12, wherein the control parameter generation circuit is configured to generate a drooping characteristic applied to each power converter, including the dead zone of each power converter to which a battery is connected, based on the voltage fluctuation range at the connection point of each power converter with the DC power distribution system. 　 The power converter management device according to any one of claims 2 to 13, wherein the control parameter generation circuit determines the slope of the drooping characteristic of each power converter based on the estimation result of the voltage fluctuation range at the connection point of each power converter with the DC distribution system. 　 The power converter management device according to claim 14, wherein the control parameter generation circuit determines the slope of the drooping characteristic of each power converter based on the control mode of each power converter. 　 The power converter management device according to any one of claims 2 to 15, wherein the control parameter generation circuit is configured to select a drooping characteristic defined for each power converter if the estimated power flow or power flow current is within a predetermined range defined for each power converter. 　 The power converter management device according to any one of claims 2 to 16, wherein the operation plan creation circuit generates the voltage command value based on the estimated voltage at the connection point of the power converter having a drooping characteristic with the DC distribution system. 　 A power converter management device according to any one of claims 1 to 17, The aforementioned DC power distribution system, A DC power distribution system comprising the aforementioned multiple power converters.

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