Power conversion device and power converter management device

Abstract

A power conversion device (6) is provided with: an AC / DC conversion circuit (63) that converts AC power of an AC system to DC power of a DC system, or converts DC power of the DC system to AC power of the AC system; a voltmeter (66) that measures the DC voltage of the DC system; and a control circuit (64) that detects the frequency of the AC system, calculates the power exchanged between the AC system and the DC system, and uses the measured DC voltage to calculate the surplus and deficit power of the DC system on the basis of a first droop characteristic representing the DC-side characteristics, and uses the detected frequency or the calculated power to calculate the inertial force requested by the AC system on the basis of a second droop characteristic representing the AC-side characteristics, thereby correcting an input frequency command value or power command value and controlling the AC / DC conversion circuit on the basis of the corrected frequency command value or the corrected power command value.

Description

Power conversion apparatus and power converter management apparatus

[0001] The present disclosure relates to a power conversion apparatus and a power converter management apparatus.

[0002] Conventionally, power conversion apparatuses using a droop control method are known. For example, the power conversion apparatus described in Patent Document 1 includes a correction value generation unit that 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 apparatus 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 apparatus based on a corrected output current value which is the output current value corrected by the output current correction value, and controls the output voltage based on the drooped output voltage target value and the output voltage value.

[0003] WO2023 / 063073

[0004] In Patent Document 1, inertia cannot be provided to both an alternating current (AC) system and a direct current (DC) system.

[0005] Therefore, an object of the present disclosure is to provide a power conversion apparatus and a power converter management apparatus that can provide inertia to both an AC system and a DC system.

[0006] The power conversion apparatus of the present disclosure includes: an AC / DC conversion circuit that converts AC power of an AC system into DC power of a DC system, or converts DC power of a DC system into AC power of an AC system; a voltmeter that measures a DC voltage of the DC system; and a control circuit that detects a frequency of the AC system, calculates power transferred between the AC system and the DC system, calculates surplus / deficit power of the DC system based on a first droop characteristic representing a DC-side characteristic using the measured DC voltage, calculates an inertia required by the AC system based on a second droop characteristic representing an AC-side characteristic using the detected frequency or the calculated power, corrects an input frequency command value or power command value, and controls the AC / DC conversion circuit based on the corrected frequency command value or the corrected power command value.

[0007] According to the present disclosure, inertia can be provided to both an AC system and a DC system.

[0008] This is a block diagram showing the configuration of a one-feeder DC microgrid 100 and an AC / DC mixed microgrid, which are composed of a DC distribution system 21 to which a CEMS 3 and distributed power sources according to the embodiment are connected. This is a block diagram of the CEMS 3 shown in Figure 1. This is a block diagram of the operation plan creation circuit 34 in the CEMS 3 shown in Figure 2. This is a block diagram of the control parameter generation circuit 33 in the CEMS 3 shown in Figure 2. This is a block diagram of the AC / DC converter 6 shown in Figure 1. This is a block diagram of the power conversion device 9 for distribution system batteries shown in Figure 1. This is a block diagram of the power conversion device 13 for consumer PV shown in Figure 1. This is a block diagram showing the configuration of the first control circuit 64 that controls the AC / DC conversion circuit 63 of the AC / DC converter 6 shown in Figure 5 in Embodiment 1. This is a block diagram showing the configuration of the second control circuit 94 that controls the first DC / DC conversion circuit 93 of the power conversion device 9 for distribution system batteries shown in Figure 6. This is a block diagram showing the configuration of the third control circuit 134 that controls the second DC / DC conversion circuit 133 of the consumer PV power converter 13 shown in Figure 7. This is a block diagram of the GFL control signal generation circuit 645 shown in Figure 8 in Embodiment 1. This is a block diagram of the GFM control signal generation circuit 646 shown in Figure 8 in Embodiment 1. This is a diagram showing the drooping characteristics (GFL drooping characteristics) on the AC power distribution system 20 side when in GFL control mode in Embodiment 1. This is a diagram showing the drooping characteristics on the DC power distribution system 21 side when in GFL control mode in Embodiment 1. This is a diagram showing the drooping characteristics (GFM drooping characteristics) on the AC power distribution system 20 side when in GFM control mode in Embodiment 1. This is a diagram showing the drooping characteristics on the DC power distribution system 21 side when in GFM control mode in Embodiment 1. This is a block diagram of the inverter current control circuit 648 shown in Figure 8. This is a block diagram of the inverter voltage control circuit 649 shown in Figure 8. This is a block diagram of the voltage target generation circuit 942 shown in Figure 9. This is a block diagram of the first governor control circuit 9422 shown in Figure 19. Figure 19 is a block diagram of the first mass-point system calculation circuit 9425. Figure 9 is a block diagram of the power target generation circuit 943. Figure 22 is a block diagram of the second governor control circuit 9432. Figure 22 is a block diagram of the second mass-point system calculation circuit 9435.Figure 9 is a block diagram of the voltage target value control circuit 945. Figure 9 is a block diagram of the power target value control circuit 946. Figure 12 is a block diagram for calculating the transfer function F(s) of the GFM droop characteristic circuit 6470 in the GFM control signal generation circuit 646. Figure 19 is a block diagram for calculating the transfer function F(s) of the voltage target generation circuit 942. Figure 22 is a block diagram for calculating the transfer function F(s) of the power target generation circuit 943. Figure 23 is a diagram showing an example of a droop characteristic (power-voltage characteristic) to be implemented in the power converter 9 for a power distribution system battery. Figure 23 is a diagram showing an example of a droop characteristic (voltage-power characteristic) to be implemented in the power converter 9 for a power distribution system battery. Figure 3 is a diagram for explaining the fluctuation range of the interconnection point voltage of each power converter 9 for a power distribution system battery, taking into account the change in the power current flowing through the DC power distribution system 21. Figure 4 is a diagram for explaining the operation of the AC / DC converter 6 operating in GFL control mode in Embodiment 1. Figure 5 is a diagram for explaining the operation of the AC / DC converter 6 operating in GFL control mode in Embodiment 1. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode in Embodiment 1. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode in Embodiment 1. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode in Embodiment 1. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode in Embodiment 1. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode in Embodiment 1. This is a diagram illustrating the response waveform when the customer load 11 in the customer load group 10a changes in a step-like manner in the configuration of Figure 31. This is a diagram illustrating the response waveform when the customer load 11 in the customer load group 10a changes in a step-like manner in the configuration of Figure 31. This is a diagram illustrating the communication processing in CEMS 3. This is a flowchart diagram showing the control procedure of CEMS 3. This is a flowchart diagram showing the system impedance estimation procedure of S100 in Figure 36. This is a flowchart diagram showing the detailed procedure of the operation plan creation process (creation of operation plan 1) of S105 in Figure 36. Figure 38 is a flowchart illustrating the detailed procedure for determining the power distribution system battery charging and discharging power (power command value) in S1054.This is a flowchart showing the detailed procedure for each power receiving point voltage prediction 1 in S1057 of Figure 38. This is a flowchart showing the detailed procedure for the power distribution system battery charge / discharge power review 1 in S1060 of Figure 38. This is a flowchart showing the detailed procedure for the drooping characteristic generation 1 in S1061 of Figure 38. This is a diagram to explain the operation when generating the DC side drooping characteristic to be implemented in the AC / DC converter 6 or the power conversion device 9 for power distribution system batteries shown in Figure 1. This is a diagram to explain the operation when generating the DC side drooping characteristic to be implemented in the AC / DC converter 6 or the power conversion device 9 for power distribution system batteries shown in Figure 1. This is a diagram to explain the operation when generating the DC side drooping characteristic to be implemented in the AC / DC converter 6 shown in Figure 1. This is a diagram to explain the operation when generating the AC side drooping characteristic to be implemented in the AC / DC converter 6 shown in Figure 1. This is a diagram to explain the operation when generating the AC side drooping characteristic to be implemented in the AC / DC converter 6 shown in Figure 1. This is a flowchart showing the control procedure of the first control circuit 64. This is a flowchart showing the control procedure of the first AC / DC conversion circuit at S204 in Figure 45. This is a flowchart showing the GFL control procedure at S2048 in Figure 46. This is a flowchart showing the GFM control procedure at S2049 in Figure 46. This is a flowchart showing the control procedure of the second control circuit 94. This is a flowchart showing the control procedure of the first DC / DC conversion circuit at S304 in Figure 49. This is a block diagram of the GFL control signal generation circuit 645 shown in Figure 8 in Embodiment 2. This is a block diagram of the GFM control signal generation circuit 646 shown in Figure 8 in Embodiment 2. This is a diagram showing the drooping characteristics (GFL drooping characteristics) on the AC power distribution system 20 side in GFL control mode in Embodiment 2. This is a diagram showing the drooping characteristics on the DC power distribution system 21 side in GFL control mode in Embodiment 2. This is a diagram showing the drooping characteristics (GFM drooping characteristics) on the AC power distribution system 20 side in GFM control mode in Embodiment 2. This figure shows the drooping characteristics on the DC power distribution system 21 side when the GFM control mode is in Embodiment 2. This figure is for explaining the operation of the AC / DC converter 6 operating in the GFL control mode according to Embodiment 2. This figure is for explaining the operation of the AC / DC converter 6 operating in the GFL control mode according to Embodiment 2.This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode according to Embodiment 2. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode according to Embodiment 2. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode according to Embodiment 2. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode according to Embodiment 2. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFM control mode according to Embodiment 2. This is a block diagram of the GFL control signal generation circuit 645 shown in Figure 8 in Embodiment 3. This is a block diagram of the GFM control signal generation circuit 646 shown in Figure 8 in Embodiment 3. This is a diagram showing the drooping characteristics (GFL drooping characteristics) on the AC power distribution system 20 side when in GFL control mode in Embodiment 3. This is a diagram showing the drooping characteristics on the DC power distribution system 21 side when in GFL control mode in Embodiment 3. This is a diagram showing the drooping characteristics (GFM drooping characteristics) on the AC power distribution system 20 side when in GFM control mode in Embodiment 3. This is a diagram showing the drooping characteristics on the DC power distribution system 21 side when in GFM control mode in Embodiment 3. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode and GFM control mode according to Embodiment 3. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode and GFM control mode according to Embodiment 3. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode and GFM control mode according to Embodiment 3. This is a diagram illustrating the operation of the AC / DC converter 6 operating in GFL control mode and GFM control mode according to Embodiment 3. This is a block diagram showing the configuration of the first control circuit 64 that controls the AC / DC conversion circuit 63 of the AC / DC converter 6 shown in Figure 5 in Embodiment 4. This is a block diagram of the second GFL control signal generation circuit 656 shown in Figure 66 in Embodiment 4. This is a block diagram of the second GFM control signal generation circuit 657 shown in Figure 66 in Embodiment 4. This is a diagram illustrating an example of the shape of the GFL drooping characteristic. This is a diagram illustrating an example of the shape of the GFL drooping characteristic. This is a diagram illustrating an example of the shape of the GFL drooping characteristic. This is a diagram illustrating an example of the shape of the GFL drooping characteristic. This is a diagram illustrating an example of the shape of the GFL drooping characteristic.This figure shows an example of the shape of the GFM droop characteristic. This figure shows an example of the shape of the GFM droop characteristic. This figure shows an example of the shape of the GFM droop characteristic. This figure shows an example of the shape of the GFM droop characteristic. This figure shows an example of the shape of the DC side droop characteristic. This figure shows an example of the shape of the DC side droop characteristic. This figure shows an example of the shape of the DC side droop characteristic. This figure shows an example of the shape of the DC side droop characteristic. This figure shows an example of the shape of the DC side droop characteristic. This figure illustrates an example of how to notify the AC / DC converter 6 of various droop characteristics.

[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 impact, such as CO2 emissions, and the problem of energy resource depletion. Since renewable energy sources such as solar cells (hereinafter referred to as "PV") output DC power, they have high compatibility 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. In areas where the development of trunk grids is lagging, DC microgrids using renewable energy such as PV (photovoltaics) 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" planned in Europe from 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, if economic rationality can be guaranteed, DC microgrids will become widespread in various settings, including factories, office buildings, and disaster prevention bases of local governments. Microgrids in which AC and DC power transmission and distribution systems are interconnected and linked, i.e., microgrids in which AC and DC systems coexist (hereinafter referred to as AC / DC mixed microgrids), are also expected to become widespread in the future.

[0011] In particular, unlike AC power transmission and distribution, DC power transmission and distribution does not require frequency management, so converter control can be simplified. However, DC power transmission and distribution does not possess the inertial force that AC power transmission and distribution systems have. 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 excess or deficit power is adjusted using the inertial force (the inertial force of the rotating body) of, for example, a synchronous generator installed in a thermal power plant. Specifically, if there is a surplus power in the transmission and distribution system, the surplus power is converted into kinetic energy and stored in the rotating body. At this time, the rotational speed of the rotating body increases, so the AC system frequency rises. If there is a power deficit in the transmission and distribution system, the kinetic energy of the rotating body is converted into electrical energy and output. At this time, the rotational speed of the rotating body decreases, so the AC system frequency falls.

[0012] In contrast, DC power transmission and distribution systems lack power supply equipment that possesses the inertial force of synchronous generators. For example, consider a DC microgrid constructed using n distribution system batteries 8 by opening the switch 5 in a DC distribution system as shown in Figure 1. Each distribution system battery power converter 9 controls the interconnection point voltage with the DC distribution system to 1500V. Now, let's assume that a sudden change in the customer load 11n of the customer load group 10n causes a power shortage. When a power shortage occurs, the DC voltage of the DC distribution system 21n drops. As a result, the distribution system battery power converter 9n detects the power shortage and increases its discharge power. Similarly, surplus and deficit power are supplied from other distribution system batteries 8 connected via the distribution system impedance 7n until the steady state is reached, i.e., until the DC voltage of the DC distribution system 21n converges to 1500V. However, in the steady state, the distribution system batteries 8n share the surplus and deficit power.

[0013] Thus, 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 cannot be interconnected and coordinated with other distribution system batteries 8.

[0014] To solve the problems of the DC microgrids described above, development is underway to give a pseudo-inertial force (drooping characteristic) to DC / DC converters used to connect DC power output from distributed power sources such as storage batteries to a DC power transmission and distribution system. 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, Patent Document 1 describes a power conversion device and DC power supply system comprising a measurement unit that measures the output current and output voltage output from a DC / DC converter, and a control unit that controls the output voltage output from the DC / DC converter. The control unit includes a correction value generation unit that generates an output current correction value to correct the output current value based on an output current target value, which is a 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, the output voltage target value, which is a target value of the output voltage output from the DC / DC converter, is drooped, and the output voltage output from the DC / DC converter is controlled based on the drooped output voltage target value.

[0015] Meanwhile, in the AC power transmission and distribution system, with the spread of renewable energy sources such as PV and wind power, it is predicted that the number of thermal power plants will decrease in the future. Consequently, the number of synchronous generators installed in thermal power plants will decrease, and the inertia of the AC power transmission and distribution system is also expected to decline. To address the decline in the inertia of the AC power transmission and distribution system due to the closure of thermal power plants, development is currently underway on GFM (Grid-Forming) / GFL (Grid-Following) inverters that simulate the inertia of synchronous generators to AC / DC converters. In the supply and demand adjustment market, a primary adjustment force market was established in 2024 as an adjustment force for frequency control against the "extremely short-period components" of frequency fluctuations. Primary adjustment force is designed as a product equivalent to the governor-free (GF) frequency control function of current generators, and is required to detect and respond to the frequency detected at the end of various power sources.

[0016] In this context, in microgrids where AC and DC power distribution systems are interconnected, AC / DC converters will need to have not only the function of interconnecting AC and DC power distribution systems, but also the function of supplying inertial force to both AC and DC power distribution systems, which will become an important function in the future. Specifically, when a GFM inverter function is implemented for an AC power distribution system, the AC / DC converter generates the AC system voltage as the main power source (master) and outputs it to the AC power distribution system. Therefore, if the frequency of the AC power distribution system changes or if there is an excess or deficiency of power, a portion of the excess or deficiency power will be supplied from the AC / DC converter with the GFM implemented. Similarly, when a GFL inverter function is implemented for an AC power distribution system, the AC / DC converter operates as a current source (slave) and controls the power output to the AC power distribution system based on the frequency detection result of the AC system voltage at its end.

[0017] 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 the power flow between connected distributed power sources such as batteries and renewable energy equipment and loads are important. As mentioned above, as thermal power plants are closed down, the number of synchronous generators installed in AC transmission and distribution systems decreases. This also reduces the inertial force of the AC distribution system. For example, in the AC / DC mixed microgrid shown in Figure 1, in the DC distribution system 21 within the DC microgrid 100 of one feeder, the power flow (current) flowing through the DC distribution system can be managed by distributed power sources (power converters) managing the interconnection point voltage of the DC distribution system. When an excess or deficiency of power occurs within the DC microgrid 100, the AC / DC converter 6 and the power converter 9 for the distribution system battery are controlled to manage the power flow current through the DC distribution system 21 and the terminal voltage of each converter (the voltage at the connection point with the DC distribution system 21) (AC / DC converter 6 and power converter 9 for the distribution system battery).

[0018] On the other hand, the power converter and DC power supply system described in Patent Document 1 have a current-voltage drop characteristic. In this case, multiple power converters can operate as masters (voltage sources) within a DC distribution system, but the influence of power flow and other factors on the DC distribution system is not taken into consideration. As a result, in a DC distribution system like the one shown in Figure 1, it is not possible to adequately manage the interconnection point voltage and charge / discharge power of each power converter 9 for the distribution system's battery, and especially the State of Charge (SOC) of the distribution system's battery 8.

[0019] Furthermore, as mentioned above, with regard to AC power transmission and distribution systems, the inertial force of the AC power transmission and distribution system decreases as the number of synchronous generators decreases. Therefore, it is desirable that the AC / DC converter 6 be equipped with a function that provides inertial force to the AC power transmission and distribution system, such as a GFM / GFL inverter that artificially provides the AC power transmission and distribution system with the inertial force of a synchronous generator.

[0020] This disclosure was made to solve the problems described above, and its purpose is to provide an AC / DC converter (power converter) for AC / DC mixed microgrids that provides inertial force to both AC and DC power transmission and distribution systems.

[0021] In one aspect of this disclosure, a power converter having a drooping characteristic for exchanging AC power and DC power includes: a frequency measurement unit for measuring the frequency of an AC system; a power measurement unit for measuring the power exchanged between the AC system and the DC system; a DC system voltage measurement unit for measuring the DC voltage of the DC system; an AC / DC conversion unit for converting AC power to DC power or DC power to AC power; a first drooping characteristic management unit for generating a power target correction value for exchange between the AC system and the DC system based on the DC voltage measurement result; a second drooping characteristic management unit for generating a command value for controlling the AC / DC conversion unit based on the frequency measurement result or the power measurement result; and a control unit for controlling the AC / DC conversion unit, wherein the control unit is configured to generate a command value for controlling the AC / DC conversion unit using the power target correction value generated by the first drooping characteristic management unit and the command value generated by the second drooping characteristic management unit.

[0022] According to this disclosure, the system is configured such that the excess or insufficient power of the DC system is determined by the first drooping characteristic management unit based on the DC system voltage measurement results, and the inertial force required by the AC distribution system is determined by the second drooping characteristic management unit, and the AC / DC conversion unit is controlled based on the determination results output from the first and second drooping characteristic management units. This makes it possible to provide inertial force to both the AC system and the DC system. More specifically, by changing the shape of the first and second drooping characteristics implemented in the DC system and the AC system, the ratio of inertial force applied to the AC system and the DC system, that is, the amount of power output to each system, can be controlled.

[0023] Overview of Embodiments. First, an overview of the embodiments of this disclosure will be described.

[0024] (1) A power converter (AC / DC converter 6) according to one aspect of the present disclosure includes: an AC / DC converter circuit (AC / DC converter circuit 63) that converts AC power from an AC system to DC power from a DC system, or DC power from a DC system to AC power from an AC system; a voltmeter (voltmeter 66) that measures the DC voltage of a DC system; and a control circuit (first control circuit 64) that detects the frequency of an AC system, calculates the power exchanged between the AC system and the DC system, calculates the excess or deficit power of the DC system based on a first drooping characteristic representing the characteristics of the DC side using the measured DC voltage, and calculates the inertial force required by the AC system based on a second drooping characteristic representing the characteristics of the AC side using the detected frequency or calculated power, thereby correcting the input frequency command value or power command value, and controlling the AC / DC converter circuit based on the corrected frequency command value or corrected power command value.

[0025] (2) The power converter (AC / DC converter 6) described in (1) above further comprises a communication interface circuit (first communication interface circuit 65) that communicates with the management device (CEMS 3). The control circuit (first control circuit 64) receives frequency command values ​​and power command values ​​from the management device (CEMS 3) via the communication interface circuit (first communication interface circuit 65).

[0026] (3) In the power converter (AC / DC converter 6) described in (1) or (2) above, the first drooping characteristic represents a relationship in which the difference between the DC voltage of the DC system measured by the voltmeter and the DC voltage command value of the DC system is taken as input and the first differential power representing the excess or deficit power is output, and the second drooping characteristic represents a relationship in which the difference between the detected AC system frequency and the AC system frequency command value is taken as input and the second differential power representing the inertial force is output. The control circuit (first control circuit 64) includes a first drooping characteristic circuit (DC-side drooping characteristic circuit 6453) that calculates a first differential power from the difference between the DC voltage of the DC system measured by a voltmeter and the DC voltage command value of the DC system according to a first drooping characteristic; a second drooping characteristic circuit (GFL drooping characteristic circuit 6458) that calculates a second differential power from the difference between the detected AC system frequency and the AC system frequency command value according to a second drooping characteristic; and a current control circuit (inverter current control circuit 648) that controls the AC / DC conversion circuit as a current source based on a corrected power command value which is the sum of the power command value, the first differential power, and the second differential power.

[0027] (4) In the power converter (AC / DC converter 6) described in (3) above, the first drooping characteristic has no dead zone (Figure 14), and the second drooping characteristic has a dead zone (Figure 13).

[0028] (5) In the power conversion device (AC / DC converter 6) described in (3) above, the first drooping characteristic has a dead zone (Figure 54), and the second drooping characteristic does not have a dead zone (Figure 53).

[0029] (6) In the power conversion device described in (3) above, the first drooping characteristic has no dead zone (Figure 62), and the second drooping characteristic has no dead zone (Figure 61).

[0030] (7) In the power converter (AC / DC converter 6) described in (1) or (2) above, the first drooping characteristic represents a relationship in which the difference between the DC voltage of the DC system measured by the voltmeter and the DC voltage command value of the DC system is taken as input and the first differential power representing the excess or deficit power is output, and the second drooping characteristic represents a relationship in which the value obtained by subtracting the power calculated from the sum of the first differential power and the power command value is taken as input and the difference between the frequency of the AC system representing the inertial force and the frequency command value of the AC system is output. The control circuit (first control circuit 64) includes a first drooping characteristic circuit (DC-side drooping characteristic circuit 6453) that calculates a first differential power from the difference between the DC voltage of the DC system measured by a voltmeter and the DC voltage command value of the DC system according to a first drooping characteristic; a second drooping characteristic circuit (GFM drooping characteristic circuit 6470) that calculates a difference between the frequency of the AC system and the frequency command value of the AC system from a value obtained by subtracting the power calculated from the sum of the first differential power and the power command value according to a second drooping characteristic; and a voltage control circuit (inverter voltage control circuit 649) that controls the AC / DC conversion circuit as a voltage source based on a corrected frequency command value which is the sum of the frequency command value and the difference value between the frequency command values.

[0031] (8) In the power converter (AC / DC converter 6) described in (7) above, the first drooping characteristic has a dead zone (Figure 16), and the second drooping characteristic does not have a dead zone (Figure 15).

[0032] (9) In the power converter (AC / DC converter 6) described in (7) above, the first drooping characteristic has no dead zone (Figures 56 and 64), and the second drooping characteristic has no dead zone (Figures 55 and 63).

[0033] (10) In the power converter (AC / DC converter 6) described in (3) or (7) above, the second drooping characteristic is less sensitive in a predetermined range including the origin than outside the predetermined range (Figures 69A, 69C, 70A, and 70B).

[0034] (11) In the power converter (AC / DC converter 6) described in (3) or (7) above, the second drooping characteristic is asymmetric with respect to the origin (Figures 69B, 69C, 69E, 70B, and 70D).

[0035] (12) In the power converter (AC / DC converter 6) described in (3) or (7) above, the second drooping characteristic is represented by a monotonically decreasing straight line (Figures 15, 53, 55, 61, and 63).

[0036] (13) In the power converter (AC / DC converter 6) described in (3) or (7) above, the second drooping characteristic is represented by a monotonically decreasing curve (Figures 69D and 70C).

[0037] (14) In the power converter (AC / DC converter 6) described in (3) or (7) above, the first drooping characteristic has lower sensitivity in a predetermined range including the origin than outside the predetermined range (Figures 71A and 71C).

[0038] (15) In the power converter (AC / DC converter 6) described in (3) or (7) above, the first drooping characteristic is asymmetric with respect to the origin (Figures 71B, 71C, and 71E).

[0039] (16) In the power converter (AC / DC converter 6) described in (3) or (7) above, the first drooping characteristic is represented by a monotonically decreasing straight line (Figures 14, 56, 62, and 64).

[0040] (17) In the power conversion device (AC / DC converter 6) described in (3) or (7) above, the first drooping characteristic is represented by a monotonically decreasing curve (Figure 71D).

[0041] (18) In any one of the power converters (AC / DC converter 6) described in (3) to (17) above, the first drooping characteristic circuit (DC side drooping characteristic circuit 6453) outputs a first-order lag signal of the first differential power to the second drooping characteristic circuit.

[0042] (19) In any one of the power converters (AC / DC converter 6) described in (3) to (18) above, the second drooping characteristic circuit (GFL drooping characteristic circuit 6458, GFM drooping characteristic circuit 6470) outputs a first-order lag signal of the difference value.

[0043] (20) In the power converter (AC / DC converter 6) according to any one of the above (3) to (19), comprising switches (switch 64501 and switch 65710) configured to set the output of the first droop characteristic circuit (DC-side droop characteristic circuit 6453) to 0 when the detected frequency of the AC power system is less than a predetermined frequency.

[0044] (21) A power converter management apparatus (CEMS 3) of the present disclosure that manages at least one first power converter (power converter for distribution system storage battery 9) that manages a voltage of a DC system (DC distribution system 21), and a second power converter (AC / DC converter 6) mounted with an AC / DC conversion circuit (63) having a droop characteristic that provides inertial force to the DC system (DC distribution system 21) and the AC system (AC distribution system 20), the power converter management apparatus (CEMS 3) comprising: a first droop characteristic generation circuit (storage battery droop characteristic generation circuit 334 and DC droop characteristic generation circuit 336) that generates a first droop characteristic provided to the DC system (DC distribution system 21) side; a second droop characteristic generation circuit (AC droop characteristic generation circuit 338) that generates a second droop characteristic provided to the AC system (AC distribution system 20) side; and an operation plan creation circuit (34) that generates an operation plan to be provided to the first power converter (power converter for distribution system storage battery 9) and the second power converter (AC / DC converter 6). The second droop characteristic generation circuit (AC droop characteristic generation circuit 338) generates the second droop characteristic based on a control mode of the droop characteristic provided to the AC system (AC distribution system 20) side and the inertial force, and the first droop characteristic generation circuit (storage battery droop characteristic generation circuit 334 and DC droop characteristic generation circuit 336) generates the first droop characteristic of the first power converter (power converter for distribution system storage battery 9) and the second power converter (AC / DC converter 6) based on the operation plan output from the operation plan creation circuit (34).

[0045] (22) In the power converter management apparatus (CEMS 3) of the above (21), the control mode of the droop characteristic provided to the AC system (AC distribution system 20) side is a GFL (Grid-Following) control mode or a GFM (Grid-Forming) control mode.

[0046] (23) In the power converter management device (CEMS3) of (22) above, when the second droop characteristic generation circuit (AC droop characteristic generation circuit 338) operates the second power converter (AC / DC converter 6) in the GFL control mode, the second droop characteristic is provided with a dead band.

[0047] (24) In the power converter management device (CEMS3) of (22) above, when the first droop characteristic generation circuit (storage battery droop characteristic generation circuit 334 and DC droop characteristic generation circuit 336) operates the second power converter (AC / DC converter 6) in the GFM control mode, the first droop characteristic of the second power converter (AC / DC converter 6) is provided with a dead band.

[0048] (25) The power converter management device (CEMS3) according to any one of (21) to (24) above includes a communication circuit (communication circuit 31) that communicates with a higher-level management device (distribution automation system 2), the communication circuit (31) receives contracted contents in the supply-demand adjustment market, and the second droop characteristic generation circuit (AC droop characteristic generation circuit 338) generates the second droop characteristic based on the received result.

[0049] (26) In the power converter management device (CEMS3) according to any one of (21) to (25) above, the control mode on the DC system (DC distribution system 21) side of the second power converter (AC / DC converter 6) is a power control mode.

[0050] (27) In the power converter management device (CEMS3) according to any one of (21) to (26) above, an operation plan creation circuit (34) generates at least a power command value for the first power converter (power converter 9 for distribution system storage battery) based on a supply and demand plan notified from the distribution automation system (2), the power consumption of each consumer (consumer load 11) connected to the DC system (DC distribution system 21), and a predicted power generation result of energy creation equipment (PV panel 12) owned by each consumer.

[0051] (28) In any one of the power converter management devices (CEMS3) described in (21) to (27) above, the first drooping characteristic generation circuit (battery drooping characteristic generation circuit 334 and DC drooping characteristic generation circuit 336) generates the first drooping characteristic of the second power converter (AC / DC converter 6) such that, when the supply and demand plan notified from the power distribution automation system (2) includes an upper limit and a lower limit for supply and demand, the upper limit and lower limit become the lower limit and upper limit of the DC voltage at the interconnection point between the DC system (DC distribution system 21) and the second power converter (AC / DC converter 6), respectively.

[0052] (29) In any one of the power converter management devices (CEMS3) described in (21) to (28) above, the operation plan creation circuit (34) estimates the distribution line impedance of the DC system (DC distribution system 21), and based on the estimation result of the distribution line impedance, predicts the voltage at the connection point between the second power converter (AC / DC converter 6) and the first power converter (power converter for distribution system battery 9) and the DC system (DC distribution system 21).

[0053] (30) In the power converter management device (CEMS3) described in (29) above, the operation plan creation circuit (34) predicts the power flow current of the DC system (DC distribution system 21) based on the power consumption (customer load 11) of each customer connected to the DC system (DC distribution system 21) and the predicted power generation results of the energy creation equipment (PV panel 12) owned by each customer. Based on the predicted power flow current and the estimated distribution line impedance, the circuit predicts the voltage at the connection point between the second power converter (AC / DC converter 6) and the first power converter (power converter for distribution system battery 9) and the DC system (DC distribution system 21), and generates a DC voltage command value based on the prediction results.

[0054] (31) In the power converter management device (CEMS3) described in (30) above, the operation plan creation circuit (34) predicts the upper and lower limits of the power demand when predicting the power consumption (customer load 11) of each customer connected to the DC system (DC distribution system 21) and the power generation of the energy generation equipment (PV panel 12) owned by each customer. The first drooping characteristic generation circuit (storage battery drooping characteristic generation circuit 334 and DC drooping characteristic generation circuit 336) generates the first drooping characteristics of the first power converter (power converter for distribution system storage battery 9) and the second power converter (AC / DC converter 6) so that the predicted upper and lower limits of the power demand fall within the upper and lower voltage range of the voltage of the DC system (DC distribution system 21).

[0055] (32) In the power converter management device (CEMS3) described in (31) above, the operation plan creation circuit (34) predicts the fluctuation range of the power flow current of the DC system (DC distribution system 21) based on the predicted upper and lower limits of the power demand, and predicts the voltage fluctuations at the connection points between the second power converter (AC / DC converter 6) and the first power converter (power converter for distribution system battery 9) and the DC system (DC distribution system 21) based on the predicted fluctuation range of the power flow current, and generates first droop characteristics for the first power converter (power converter for distribution system battery 9) and the second power converter (AC / DC converter 6) so that the voltage fluctuations of the DC system (DC distribution system 21) fall within the upper and lower voltage limits of the DC system (DC distribution system 21).

[0056] (33) In the power converter management device (CEMS3) described in (23) above, the operation plan creation circuit (34) predicts the frequency fluctuation range of the AC system (AC distribution system 20) and determines the frequency range in which a dead zone will be introduced based on the predicted frequency fluctuation range of the AC system (AC distribution system 20) when operating the second power converter (AC / DC converter 6) in GFL control mode and when introducing a dead zone to the second droop characteristic generated by the second droop characteristic generation circuit (AC droop characteristic generation circuit 338).

[0057] Embodiment 1. Figure 1 is a block diagram showing the configuration of a single-feeder DC microgrid 100 and an AC / DC mixed microgrid, which are configured with a DC distribution system 21 to which a CEMS 3 and distributed power sources according to this embodiment are connected. In Embodiment 1, the standard DC voltage of the DC distribution system 21 is 1500V, and the appropriate voltage range is 1350V to 1650V (the appropriate voltage range is ±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 will describe the case in which DC microgrids 100a to 100m are connected to a substation 1 and below to configure an AC / DC mixed microgrid. Embodiment 1 describes the case of three-phase AC, but it is not limited to three-phase AC; single-phase AC, single-phase three-wire AC, etc., may also be used.

[0058] Three-phase AC power from substation 1 is input to switch 5 via AC distribution system 20a. The output of switch 5 is input to AC / DC converter 6 via AC distribution system 20b. In Embodiment 1, under normal circumstances, DC distribution system 21 is connected to AC distribution system via AC / DC converter 6. In the event of a power outage, switch 5 disconnects AC distribution system 20b and below from the higher-level transmission (main) system, and the DC independent systems (DC microgrids) 100 operate independently or in conjunction with each other.

[0059] The distribution automation system (hereinafter referred to as DSO) 2 collects, for example, the power consumption of each customer load group 10, the power generation and status information of the PV panels 12, and the charge / discharge power, SOC and SOH (State of Health) information of the distribution system battery 8 via the CEMS 3. Based on the collected results, the DSO 2 generates, for example, power supply information from the upstream (main) grid for a 30-minute period and outputs it to the CEMS 3.

[0060] CEMS3 collects and manages 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 the droop characteristics of the AC / DC converter 6 and each distribution system battery power converter 9.

[0061] In Embodiment 1, the weather forecast server 4 outputs weather forecast information every 24 hours and 30 minutes. Although the accuracy of the prediction of the power generation amount of the PV panel 12 differs, the information from the weather forecast server 4 is not limited to every 30 minutes; it may be at more frequent intervals (e.g., every minute) or even longer intervals (e.g., every 6 hours).

[0062] The communication line 22 transmits information between the CEMS 3 and the equipment of the DC self-contained system (DC microgrid) 100.

[0063] The AC / DC converter 6 converts the AC power supplied from the AC power distribution system 20b into DC power and outputs it to the DC power distribution system 21 (forward power). If there is surplus power in the DC power distribution system 21, the AC / DC converter 6 converts the surplus DC power from the DC power distribution system 21 into AC power and outputs it to the AC power distribution system 20b (reverse power).

[0064] The DC power distribution system 21 is connected to a power conversion device 9 for the power distribution system battery and a group of customer loads 10, etc., via a power distribution system impedance 7.

[0065] The power converter 9 for the power distribution system battery outputs the DC power output 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, the power converter 9 charges the power distribution system battery 8 with that surplus power.

[0066] The customer load group 10 comprises a customer load 11, a PV panel 12, and a customer PV power converter 13. In Embodiment 1, for the sake of clarity, the customer load group 10 includes customer loads 11 from multiple neighboring customers, and a customer PV power converter 13 installed in the customer's residence, etc.

[0067] The consumer PV power converter 13 outputs the DC power generated by the PV panels 12 to the DC distribution system.

[0068] The following explanation continues, assuming that the power generation forecasting database 351 and the power consumption forecasting database 352 are constructed for each customer load group 10.

[0069] In the following explanation, the "AC / DC converter 6 and power conversion devices 9a to 9n for distribution system batteries" will also be referred to as "each converter" (power conversion device).

[0070] Figure 2 is a block diagram of the CEMS3 shown in Figure 1. The CEMS3 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.

[0071] The communication circuit 31 transmits measurement information to the DSO2 via the communication line 22, receives control commands (24-hour supply and demand (demand) plan) from the DSO2, collects measurement data from communication terminals within the customer load groups 10a to 10n (such as smart meters installed at each customer, not shown), collects measurement data from the power conversion devices 9a to 9n and AC / DC converters 6 for the distribution system battery, and transmits command values ​​(voltage command values ​​and power command values) and droop characteristics to each converter (power conversion device).

[0072] The memory circuit 32 stores various information obtained via the communication circuit 31 (such as measurement data and status information of each distributed power supply), various transmission data including command value information notified to each converter (power converter), and the drooping characteristics of each converter (power converter).

[0073] The control parameter generation circuit 33 determines the control modes (the definition of control modes will be described later) for the AC / DC converter 6 and the power conversion devices 9a to 9n for the power distribution system battery, and generates droop characteristics (details will be described later) to be notified to each converter.

[0074] The operation plan creation circuit 34 creates an operation plan for the AC / DC converter 6 and the power converters 9a to 9n for the distribution system battery based on the control command (demand plan for 24 hours) from the DSO2. In Embodiment 1, an operation plan for 24 hours is created at 30-minute intervals. The operation plan includes the voltage command value and power (current) command value for each converter.

[0075] The operation plan creation circuit 34 collects measurement information from each converter, which is collected at 5-minute intervals, as well as SOC and SOH information from the power distribution system batteries 8a to 8n.

[0076] The transmission data generation circuit 35 generates transmission data (transmission packets) based on the control output output from the distributed power management control circuit 36, using the droop characteristic information 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. In Embodiment 1, for the power converters 9a to 9n for the distribution system battery, the droop characteristic information is the inertia constant M, the braking coefficient Dg, the speed adjustment rate Kgd, and the governor time constant Tg. For the AC / DC converter 6, the droop characteristic information is the AC side droop characteristic (FGL or GFM droop characteristic depending on the control mode) and the DC side droop characteristic. The generated transmission data is transmitted via the communication circuit 31 based on the transmission command from the distributed power management control circuit 36.

[0077] The distributed power management control circuit 36 ​​manages the operation of the communication circuit 31, memory circuit 32, control parameter generation circuit 33, operation plan creation circuit 34, and transmission data generation circuit 35 within the CEMS 3.

[0078] 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 demand load prediction circuit 341, a power generation prediction circuit 342, a power consumption prediction circuit 343, a battery operation plan creation circuit 344, an AC / DC operation plan creation circuit 345, a frequency fluctuation prediction circuit 346, a grid impedance estimation circuit 347, a power flow current estimation circuit 348, a grid voltage estimation circuit 349, an operation plan creation unit management circuit 350, a power generation prediction database 351, a power consumption prediction database 352, and a frequency fluctuation prediction database 353.

[0079] The power generation prediction circuit 342 obtains 24 hours of weather forecast information from the weather forecast server 4 via the communication circuit 31, and predicts the total power generated by the PV panels 12 in each customer load group 10 based on the obtained weather forecast information, internal clock information (year, month, day, time) of the CEMS 3 (not shown), and information from the power generation prediction database 351.

[0080] 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, based on internal clock information (year, month, day, day of the week, time) from the CEMS3 (not shown) and information from the power consumption prediction database 352.

[0081] The demand load forecasting circuit 341 calculates the demand power for each customer load group 10 every 30 minutes for 24 hours, based on the sum of the predicted power generation results of the PV panels 12 within each customer load group 10 predicted by the power generation forecasting circuit 342, and the sum of the predicted power consumption information within each customer load group 10 predicted by the power consumption forecasting circuit 343. This demand power is calculated by subtracting the predicted power generation results of the PV panels 12 within each customer load group 10 predicted by the power generation forecasting circuit 342 from the predicted power consumption results of the customers predicted by the power consumption forecasting circuit 343.

[0082] The battery operation plan creation circuit 344 creates an operation plan for the distribution system batteries 8a to 8n based on the grid connection point voltage information, output power information, droop characteristic information, voltage command value information, power command value information, and status information (SOC and SOH information) of the AC / DC converter 6 and the power converters 9a to 9n for the distribution system batteries, which are collected via the communication circuit 31. At that time, the battery operation plan creation circuit 344 calculates the surplus and deficit power in the DC microgrid 100 by using control commands notified from DSO2. These control commands are, for example, planned values ​​(for example, planned values ​​every 30 minutes for 24 hours) of the power to be supplied to the DC distribution system 21 below substation 1 (supplied power).

[0083] The battery operation plan creation circuit 344 distributes power to each distribution system battery 8 based on the calculation results. In other words, the battery operation plan creation circuit 344 creates an operation plan (30-minute intervals, 24-hour plan) for the distribution system battery power converters 9a to 9n. The detailed operation of the battery operation plan creation circuit 344 will be described later.

[0084] The AC / DC operation plan creation circuit 345 creates an operation plan for the AC / DC converter 6 by using control commands notified from the DSO2 via the communication circuit 31. These control commands, as described above, are, for example, planned values ​​(for example, planned values ​​every 30 minutes for 24 hours) of the power to be supplied to the DC distribution system 21 below substation 1 (supplied power).

[0085] Specifically, in Embodiment 1, the AC / DC operation plan creation circuit 345 generates power command values ​​for the AC / DC converter 6 based on the operation plan notified by the DSO2. At that time, the AC / DC operation plan creation circuit 345 instructs the frequency fluctuation prediction circuit 346 to predict the fluctuation range of the AC distribution system frequency for 30 minutes. Upon receiving the instruction, the frequency fluctuation prediction circuit 346 reads data for frequency fluctuation prediction from the frequency fluctuation prediction database 353 based on the date, time, day of the week, and weather forecast information, and uses this data to predict the frequency fluctuation range for 30 minutes. In Embodiment 1, the frequency fluctuation range prediction information is used when generating the AC side droop characteristics of the AC / DC converter 6. The detailed operation of the AC / DC operation plan creation circuit 345, including the frequency fluctuation prediction circuit 346, will be described later.

[0086] The system impedance estimation circuit 347 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.

[0087] The power flow current estimation circuit 348 estimates the power flow current between each customer load group 10 based on the power command values ​​of the AC / DC converter 6 created by the AC / DC operation plan creation circuit 345, the power command values ​​of each distribution system battery power converter 9 generated by the battery operation plan creation circuit 344, 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.

[0088] The grid voltage estimation circuit 349 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 348 and the distribution system impedance 7 between each customer load group 10 output from the grid impedance estimation circuit 347.

[0089] The operation plan creation unit management circuit 350 manages the operation of the demand load forecasting circuit 341, the battery operation plan creation circuit 344, and the AC / DC operation plan creation circuit 345.

[0090] 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 battery droop characteristic slope determination circuit 333, a battery droop characteristic generation circuit 334, an AC / DC converter DC droop characteristic determination circuit 335, a DC droop characteristic generation circuit 336, an AC / DC converter AC droop characteristic determination circuit 337, and an AC droop characteristic generation circuit 338.

[0091] In Embodiment 1, since the AC / DC converter 6 provides inertial force to both the DC and AC power distribution systems, the AC / DC converter 6 operates in power control mode and does not manage the voltage of the DC power distribution system. Therefore, in Embodiment 1, at least one of the power conversion devices 9a to 9n for the power distribution system battery operates in voltage control mode, and the voltage of the DC power distribution system is managed. The control mode of the power conversion devices 9a to 9n for the power distribution system battery is determined by the configuration of the power distribution system, etc. A detailed explanation of the configuration and operation of the control modes of the AC / DC converter 6 and each control mode of the power conversion device 9 for the power distribution system battery will be given later.

[0092] 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 values ​​of the difference from the 30-minute demand forecast, and sends these along with the measurement results when it receives a measurement data output request from the CEMS 3. In Embodiment 1, the maximum and minimum values ​​of the difference from the 30-minute demand forecast sent are stored in the power consumption forecast database 352 (or power generation forecast database 351) along with weather, date, day of the week, and time information. When predicting the power demand fluctuation range, the power demand fluctuation prediction circuit 332 reads the maximum and minimum values ​​of the difference from the demand forecast from the power consumption forecast database 352. Based on the read power demand fluctuation range, the power demand fluctuation prediction circuit 332 creates the demand fluctuation range for each customer load group 10 and outputs it to the power flow current fluctuation range estimation circuit 331. At that time, the demand power fluctuation prediction circuit 332, based on the prediction result of the frequency fluctuation range of the AC distribution system voltage, also creates the fluctuation range of the power required from the AC distribution system and outputs it to the power flow current fluctuation range estimation circuit 331.

[0093] The power flow current fluctuation range estimation circuit 331 calculates the power to be allocated to each distribution system battery 8 when the predicted maximum demand fluctuation occurs, based on the output fluctuation of the AC / DC converter 6 predicted from the demand fluctuation range of each customer load group 10 output from the demand power fluctuation prediction circuit 332 and the frequency fluctuation range, and estimates the power flow current fluctuation range from the calculation result.

[0094] The battery droop characteristic slope determination circuit 333 determines the slope of the droop characteristic of each power converter 9 for distribution system batteries. In Embodiment 1, the battery droop characteristic slope determination circuit 333 determines the slope of the droop characteristic by converting power and voltage into PU (Per Unit). Specifically, the battery droop characteristic slope determination circuit 333 determines the slope of the droop characteristic by estimating the interconnection point voltage of each power converter 9 for distribution system batteries in the DC distribution system 21 based on the power flow current fluctuation range of each customer load group 10 output from the power flow current fluctuation range estimation circuit 331 and the system impedance estimation result information, so that the PU values ​​of the differential power output from each power converter 9 for distribution system batteries are approximately the same.

[0095] The control parameter generation circuit 33 (battery droop characteristic generation circuit 334) determines the control parameters (inertia constant M, braking coefficient Dg, speed adjustment ratio Kgd, and governor time constant Tg) based on the droop characteristic slope information output from the battery droop characteristic slope determination circuit 333.

[0096] The AC / DC converter DC droop characteristic determination circuit 335 determines the slope of the droop characteristic (power control mode) applied to the DC system-side control of the AC / DC converter 6. In Embodiment 1, the AC / DC converter DC droop characteristic determination circuit 335 determines the slope of the droop characteristic by PU-converting power and voltage. Specifically, the AC / DC converter DC droop characteristic determination circuit 335 estimates the fluctuation range of the interconnection point voltage of the AC / DC converter 6 based on the output of the power flow current fluctuation range estimation circuit 331, the impedance estimation result output from the system impedance estimation circuit 347, and the prediction result of the interconnection point voltage of each power converter 9 for distribution system batteries. The AC / DC converter DC droop characteristic determination circuit 335 determines the slope of the droop characteristic based on the estimated interconnection point voltage fluctuation range information and the maximum demand and minimum demand information included in the operation plan notified by the DSO2.

[0097] The DC droop characteristic generation circuit 336 determines the presence or absence of a dead zone based on the slope information notified from the AC / DC converter DC droop characteristic determination circuit 335 and the control mode of the AC / DC converter 6. Furthermore, if a dead zone is present, it determines the lower and upper voltage limits of the dead zone, thereby determining the shape of the DC droop characteristic. Figures 14 and 16 show examples of DC droop characteristics. Details will be described later.

[0098] The AC / DC converter AC droop characteristic determination circuit 337 determines the characteristics of the droop characteristic (GFL / GFM control mode) applied to the AC system side control of the AC / DC converter 6. In Embodiment 1, the AC / DC converter AC droop characteristic determination circuit 337 determines the droop characteristic based on the adjustment force agreed upon in the supply and demand adjustment market. More specifically, in Embodiment 1, the case in which two types of control modes are implemented, namely the GFL control mode in which the AC / DC converter circuit 63 implements a GFL function to apply inertial force to the AC distribution system, and the GFM control mode in which the AC / DC converter circuit 63 implements a GFM function to apply inertial force to the AC distribution system, will be described later.

[0099] The GFL function is a function in which the AC / DC conversion circuit 63 operates as a current source and has a drooping characteristic (frequency-power drooping characteristic) that corrects the output power based on the frequency of the AC system. The GFM function is a function in which the AC / DC conversion circuit 63 operates as a voltage source (master) and has a drooping characteristic (power-frequency drooping characteristic) that corrects the frequency of the output AC voltage based on excess or insufficient power.

[0100] In Embodiment 1, in GFL control mode, the inertial force applied to the DC power distribution system 21 is prioritized. Specifically, although the details will be described later, as shown in Figure 13, when the difference frequency (ΔF) between the measured frequency of the AC system voltage and the frequency command value (for example, 60 Hz in Embodiment 1) is between -ΔFdead and ΔFdead, a dead zone is set so that the correction value of the power command value due to the frequency of the AC system voltage becomes "zero". If the difference frequency (ΔF) is not within the above range, the system is controlled to apply a correction to the power command value according to the difference frequency value (ΔF), as shown in Figure 13. Therefore, for example, if the ΔF value is set to about 0.04 to 0.05 Hz, in the measured results of the AC system voltage over a day, the frequency of the AC system voltage is in the dead zone for about half the time, so the DC power distribution system can supply inertial force to the DC power distribution system without being affected by the AC system frequency. On the other hand, in the event of a grid fault in the AC power transmission and distribution system, such as the disconnection of synchronous generators at a thermal power plant, the AC / DC converter 6 is controlled to prioritize power supply to the AC grid side, thereby suppressing the magnitude of the Nadir (maximum frequency deviation) of the AC power transmission and distribution system's frequency.

[0101] In GFM control mode, the inertial force applied to the AC distribution system 20 is prioritized. Specifically, although the details will be described later, as shown in Figure 16, if the difference voltage (ΔV) between the measured value of the DC system voltage and the voltage command value (for example, 1500V in Embodiment 1) is between -ΔVdead and ΔVdead, a dead zone is set so that the correction value of the power command value caused by the DC system voltage becomes "zero". If the difference voltage (ΔV) is not within the above range, the system is controlled to correct the power command value according to the difference voltage (ΔV), as shown in Figure 16. As a result, the AC / DC converter 6 can provide inertial force in priority to the AC distribution system even for small amplitude fluctuations in the AC system frequency. Furthermore, when a system fault occurs in the AC transmission and distribution system, such as the disconnection of synchronous generators at a thermal power plant, the AC / DC converter 6 is controlled to supply power to the AC system side in priority, thus suppressing the RoCoF (Rate of Change of Frequency), which is the rate at which the AC system frequency decreases. Furthermore, in the event of a system fault as described above, or a power outage in the higher-level AC power transmission and distribution system, the switch 5 shown in Figure 1 will operate, disconnecting the system from the higher-level AC power transmission and distribution system. In this case, since the AC / DC converter 6 operates as a voltage source in GFM control mode, each DC microgrid 100 can work together to transition to independent operation without interruption (without power outage).

[0102] The AC droop characteristic determination circuit 337 determines the control mode of the AC / DC converter 6 and generates the droop characteristic on the AC grid side. The control mode of the AC / DC converter 6, the slope of the droop characteristic, and the method for determining the dead zone width are determined based on the details of the agreement in the supply and demand adjustment market. The AC droop characteristic generation circuit 338 generates the AC droop characteristic based on the droop characteristic information output from the AC / DC converter AC droop characteristic determination circuit 337 (details will be described later).

[0103] 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, an AC / DC conversion circuit 63, a first control circuit 64, a first communication interface circuit 65, a voltmeter 66, and an ammeter 67. Voltmeters 61a and 61b measure AC voltage. Ammeters 62a and 62b measure AC current. The AC / DC conversion circuit 63 converts AC voltage to a first DC voltage, or DC voltage to AC voltage. The first control circuit 64 controls the AC / DC conversion circuit 63, and the first communication interface circuit 65 communicates with CEMS 3 and the like via a communication line 22. Voltmeter 66 measures DC voltage. Ammeter 67 measures DC current.

[0104] Figure 6 is a block diagram of the power converter 9 for a power distribution system battery shown in Figure 1. The power converter 9 for a power distribution system battery includes a voltmeter 91, an ammeter 92, a first DC / DC conversion circuit 93, a second control circuit 94, a second communication interface circuit 95, a voltmeter 96, and an ammeter 97. The voltmeter 91 measures DC voltage. The ammeter 92 measures 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. The second communication interface circuit 95 communicates with CEMS 3 and the like via a communication line 22. The voltmeter 96 measures DC voltage. The ammeter 97 measures DC current.

[0105] Figure 7 is a block diagram of the power converter 13 for consumer PV shown in Figure 1. The power converter 13 for consumer PV includes a voltmeter 131, an ammeter 132, a second DC / DC conversion circuit 133, a third control circuit 134, a third communication interface circuit 135, a voltmeter 136, and an ammeter 137. The voltmeter 131 measures DC voltage. The ammeter 132 measures DC current. The second DC / DC conversion circuit 133 converts the fourth DC voltage to a fifth DC voltage. The third control circuit 134 controls the second DC / DC conversion circuit 133. The third communication interface circuit 135 communicates with CEMS 3 and the like via a communication line 22. The voltmeter 136 measures DC voltage. The ammeter 137 measures DC current.

[0106] Figure 8 is a block diagram showing the configuration of a first control circuit 64 that controls the AC / DC conversion circuit 63 of the AC / DC converter 6 shown in Figure 5 in Embodiment 1. The first control circuit 64 includes a phase detection circuit 641, a first frequency detection circuit 642, a first power calculation circuit 643, a first sine wave generation circuit 644, a GFL control signal generation circuit 645, a GFM control signal generation circuit 646, a fourth control circuit 647, an inverter current control circuit 648, an inverter voltage control circuit 649, a first switching circuit 650, and a first PWM conversion circuit 651.

[0107] The phase detection circuit 641 uses the measured value of the AC system voltage measured by the voltmeter 61 to detect the phase of the AC system voltage and outputs phase detection information. In Embodiment 1, the zero-crossing time information of the AC distribution system voltage is used as the phase detection information.

[0108] The first frequency detection circuit 642 detects the frequency of the AC power distribution system voltage based on the phase detection information output from the phase detection circuit 641.

[0109] The first power calculation circuit 643 calculates the power output by the AC / DC converter 6 based on the outputs of the voltmeter 66 and the ammeter 67.

[0110] The first sine wave generation circuit 644 outputs a sine wave synchronized with the AC power distribution system 20 based on the phase detection information detected by the phase detection circuit 641 and the measured frequency results of the AC power system voltage detected by the first frequency detection circuit 642.

[0111] When in GFL control mode, the GFL control signal generation circuit 645 generates and outputs a power target value (corrected power command value) to be output to the inverter current control circuit 648 based on the measured frequency result of the AC power distribution system voltage output from the first frequency detection circuit 642, the frequency command value (60 Hz), the measured voltage at the interconnection point of the DC power distribution system 21 output from the voltmeter 66, the voltage command value (1500 V), and the power command value information notified from the CEMS 3.

[0112] When in GFM control mode, the GFM control signal generation circuit 646 generates and outputs a frequency target value (corrected frequency command value) to be output to the inverter voltage control circuit 649 based on the measured interconnection point voltage of the DC power distribution system 21 output from the voltmeter 66, the voltage command value (1500V), the phase detection result of the AC voltage of the AC power distribution system 20 detected by the phase detection circuit 641, the frequency detection result detected by the first frequency detection circuit 642, the measured power value output from the first power calculation circuit 643, the frequency command value notified from the CEMS 3, and the power command value information.

[0113] The fourth control circuit 647 collects measurement results related to the DC power distribution system 21 output from the voltmeter 66 and ammeter 67, measurement results related to the AC power distribution system 20 output from the voltmeters 61a and 61b and ammeters 62a and 62b, power target values ​​(corrected power command values) output from the GFL control signal generation circuit 645, frequency target values ​​(corrected frequency command values) output from the GFM control signal generation circuit 646, and notifies the CEMS 3 and other systems of the collected information via the first communication interface circuit 65. The fourth control circuit 647 stores various information notified from the CEMS 3 via the first communication interface circuit 65 (control parameters related to drooping characteristics, power command values, voltage command values, control parameters for controlling the inverter current control circuit 648, and control parameters for controlling the inverter voltage control circuit 649, etc.) in registers not shown and outputs them to each circuit.

[0114] The inverter current control circuit 648 generates a current command value to output to the AC / DC conversion circuit 63 based on the power command value output from the GFL control signal generation circuit 645 and the sine wave information synchronized with the AC power distribution system frequency output from the first sine wave generation circuit 644. As a result, the AC / DC conversion circuit 63 is controlled as a current source.

[0115] The inverter voltage control circuit 649 generates a target value for the AC system voltage and a command value (voltage command value) to output to the AC / DC conversion circuit 63, based on the frequency command value output from the GFM control signal generation circuit 646, the phase detection information output from the phase detection circuit 641, and the voltage amplitude command value information of the AC system voltage. As a result, the AC / DC conversion circuit 63 is controlled as a voltage source.

[0116] The first switching circuit 650 selects and outputs either the output of the inverter current control circuit 648 or the output of the inverter voltage control circuit 649 based on the selection signal output from the fourth control circuit 647.

[0117] The first PWM conversion circuit 651 applies PWM modulation to the current command value output from the first switching circuit 650 and outputs it to the DC / AC conversion circuit 63.

[0118] Figure 9 is a block diagram showing 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 voltage target generation circuit 942, a power target generation circuit 943, a voltage target value control circuit 945, a power target value control circuit 946, a second switching circuit 947, a current limiting circuit 948, and a fifth control circuit 949.

[0119] The second power calculation circuit 941 calculates the charge and discharge power based on the measured value of the DC system voltage measured by the voltmeter 96 and the measured value of the DC system current measured by the ammeter 97.

[0120] The voltage target generation circuit 942 generates a voltage target value for the DC power distribution system 21 based on the output of the second power calculation circuit 941 and the output of the voltmeter 96. The voltage target generation circuit 942 has a drooping characteristic (details will be described later) when the power converter 9 for the power distribution system battery operates in voltage control mode.

[0121] 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 (details will be described later) when the power converter 9 for the power distribution system battery operates in power control mode.

[0122] The voltage target value control circuit 945 generates a current command value to output to the first DC / DC conversion circuit 93 based on the voltage target value of the DC power distribution system 21 output from the voltage target generation circuit 942.

[0123] 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.

[0124] The second switching circuit 947 switches between the output of the 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.

[0125] The current limiting circuit 948 limits the current command value output from the second switching circuit 947 and outputs it to the first DC / DC conversion circuit 93 after applying PWM modulation.

[0126] The fifth control circuit 949 collects the output of the power distribution system battery 8 output from the voltmeters 91, 96 and ammeters 92, 97, measurement results related to the DC power distribution system 21, and the voltage target value output from the voltage target generation circuit 942 or the power target value output from the power target generation circuit 943, and notifies the CEMS 3 and the like of the collected information via the second communication interface circuit 95. The fifth control circuit 949 stores the various information notified from the CEMS 3 via the second communication interface circuit 95 (control parameters related to drooping characteristics, power command value, voltage command value, control parameters of the voltage target value control circuit 945 and the power target value control circuit 946, etc.) in registers (not shown) and outputs them to each circuit.

[0127] Figure 10 is a block diagram showing 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.

[0128] The third control circuit 134 includes an MPPT (Maximum Power Point Tracking) control circuit 1341, a PV voltage control circuit 1342, a third switching circuit 1343, and a sixth control circuit 1344.

[0129] 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 a second DC / DC converter circuit 133 to control the DC voltage measured by the voltmeter 131 to the voltage corresponding to the maximum power point.

[0130] The PV voltage control circuit 1342 generates a control command value for the second DC / DC conversion circuit 133 when maintaining the DC voltage (fifth DC voltage) of the DC power distribution system 21 at a predetermined target voltage, based on the measurement value of the voltmeter 136.

[0131] 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 control signals for the third switching circuit 1343.

[0132] The third switching circuit 1343 selectively outputs one of the outputs of the MPPT control circuit 1341 and the PV voltage control circuit 1342 as a control command value for the second DC / DC conversion circuit 133, in accordance with a control signal from the sixth control circuit 1344. As a result, the second DC / DC conversion circuit 133 is controlled in either MPPT mode or PV voltage control mode. The third switching circuit 1343 is controlled to output the control command value generated by the MPPT control circuit 1341 in MPPT mode, and to output the control command value generated by the PV voltage control circuit 1342 in PV voltage control mode.

[0133] Figure 11 is a block diagram of the GFL control signal generation circuit 645 shown in Figure 8 in Embodiment 1. The GFL control signal generation circuit 645 includes a subtractor 6450, a DC-side drooping characteristic circuit 6453, an adder 6454, a subtractor 6455, a GFL drooping characteristic circuit 6458, and an adder 6459.

[0134] The subtractor 6450 subtracts the DC voltage command value output from the fourth control circuit 647 from the output of the voltmeter 66 (voltage of the DC power distribution system 21) and outputs the difference voltage ΔV.

[0135] The DC side droop characteristic circuit 6453 consists of a DC droop characteristic table 6451 and a first-order lag circuit (indicated as 1 / (1+s×Tdrop_dc1) in the figure) 6452.

[0136] The DC droop characteristic table 6451 outputs the inertial force (differential power ΔPx) applied to the DC distribution system 21 according to the droop characteristic (DC droop characteristic) of the DC distribution system 21. Figure 14 shows the droop characteristic of the DC distribution system 21 in GFL control mode in Embodiment 1. The droop characteristic (DC droop characteristic) of the DC distribution system 21 represents a relationship in which the subtraction result (differential voltage ΔV) output from the subtractor 6450 is input and the inertial force applied to the DC distribution system 21 (i.e., excess or insufficient power of the DC distribution system 21) (differential power ΔPx) is output. The droop characteristic of the DC distribution system 21 applied in GFL control mode is not limited to Figure 14, and may have a dead zone as shown in Figure 54, or be defined by a monotonically decreasing curve as shown in Figures 71A to E, or have a monotonically decreasing shape approximated by multiple straight lines.

[0137] The first-order lag circuit 6452 delays the excess / deficit power (ΔPx) output from the DC droop characteristic table 6451. Hereafter, the filtering process that removes high-frequency components and smooths the change using the first-order lag circuit will be referred to as delay. This is introduced in Embodiment 1 to ensure stable operation of the DC side droop characteristic control operation.

[0138] The adder 6454 adds the power command value output from the fourth control circuit 647 and the excess / deficit power (differential power ΔPx) output from the DC-side droop characteristic circuit 6453 (first-order lag circuit 6452).

[0139] The subtractor 6455 subtracts the measured frequency output from the first frequency detection circuit 642 from the frequency command value (Fref) output from the fourth control circuit 647, and outputs the difference frequency ΔF.

[0140] The GFL droop characteristic circuit 6458 consists of a GFL droop characteristic table 6456 and a first-order lag circuit (indicated as 1 / (1+s×Tdrop_gfl1) in the figure) 6457.

[0141] The GFL drooping characteristic table 6456 generates the inertial force (ΔPy) applied to the AC distribution system 20 according to the drooping characteristic (GFL drooping characteristic) of the AC distribution system 20 during GFL control mode. Figure 13 shows the drooping characteristic (GFL drooping characteristic) of the AC distribution system 20 during GFL control mode in Embodiment 1. The GFL drooping characteristic represents a relationship in which the subtraction result (difference frequency ΔF) output from the subtractor 6455 is input and the inertial force (difference power ΔPy) applied to the AC distribution system 20 is output. In Embodiment 1, as described above, the inertial force applied to the DC distribution system 21 is prioritized in GFL control mode. Therefore, as shown in Figure 13, the GFL drooping characteristic is described as having a dead zone. That is, ΔPy is 0 in a predetermined range of the difference frequency ΔF that includes the origin. The GFL drooping characteristics are not limited to those shown in Figure 13, but may also include those without a dead zone as shown in Figures 53 and 61, monotonically decreasing curves as shown in Figures 69A to E, or monotonically decreasing shapes approximated by multiple straight lines, or shapes that are not symmetrical with respect to the origin, etc.

[0142] The first-order lag circuit 6457 delays the inertial force (differential power ΔPy) output from the GFL droop characteristic table 6456. This was introduced in Embodiment 1 to ensure stable operation of the GFL droop characteristic control operation.

[0143] The adder 6459 corrects the power command value by adding the output of the first-order lag circuit 6457 and the output of the adder 6454. The summation result is output to the inverter current control circuit 648 as the corrected power command value.

[0144] Figure 12 is a block diagram of the GFM control signal generation circuit 646 shown in Figure 8 in Embodiment 1. The GFM control signal generation circuit 646 comprises a subtractor 6460, a DC-side droop characteristic circuit 6463, an adder 6464, a subtractor 6465, a GFM droop characteristic circuit 6470, and an adder 6469.

[0145] The subtractor 6460 takes the output of the voltmeter 66 (voltage of the DC power distribution system 21) as a DC voltage command value output from the fourth control circuit 647 and outputs a differential voltage ΔV.

[0146] The DC side droop characteristic circuit 6463 consists of a DC droop characteristic table 6461 and a first-order lag circuit (denoted as 1 / (1+s×Tdrop_dc2) in the figure) 6462.

[0147] The DC droop characteristic table 6461 outputs the inertial force (i.e., excess or insufficient power of the DC distribution system 21) (differential power ΔPx) applied to the DC distribution system 21 according to the droop characteristic of the DC distribution system 21 in GFM control mode. Figure 16 is a diagram showing the droop characteristic of the DC distribution system 21 in GFM control mode in Embodiment 1. The droop characteristic of the DC distribution system 21 (DC droop characteristic) represents a relationship in which the subtraction result (differential voltage ΔV) output from the subtractor 6450 is input and the inertial force (differential power ΔPx) applied to the DC distribution system 21 is output.

[0148] In Embodiment 1, as described above, the GFM control mode prioritizes the inertial force applied to the AC power distribution system 20. Therefore, the DC droop characteristic is described as having a dead zone, as shown in Figure 16. The droop characteristic on the DC power distribution system 21 side applied in GFM control mode is not limited to Figure 16, and may be one without a dead zone as shown in Figures 56 and 64, or one defined by a monotonically decreasing curve as shown in Figures 71A to E, or a monotonically decreasing shape approximated by multiple straight lines.

[0149] The first-order lag circuit 6462 delays the inertial force (ΔPx) output from the DC droop characteristic table 6461. This was introduced in Embodiment 1 to ensure stable operation of the DC side droop characteristic control operation.

[0150] The adder 6464 adds the power command value output from the fourth control circuit 647 and the inertial force (difference power ΔPx) output from the DC-side drooping characteristic circuit 6463 (first-order lag circuit 6462).

[0151] The subtractor 6465 outputs the differential power ΔPy by subtracting the output of the first power calculation circuit 643 (power output from the AC / DC converter 6) from the output of the adder 6464.

[0152] The GFM droop characteristic circuit 6470 consists of a subtractor 6466, a multiplier 6467, and an integrator 6468.

[0153] The subtractor 6466 subtracts the output of the multiplier 6467 from the output of the subtractor 6465. The multiplier 6467 multiplies the output of the integrator 6468 by the damping coefficient (Dg_coefficiency_ac1) output from the fourth control circuit 647, and outputs the multiplication result to the subtractor 6466.

[0154] The integrating circuit 6468 integrates the result of dividing the output of the subtractor 6466 by Moment_ac1.

[0155] The GFM droop characteristic circuit 6470 generates the difference frequency (ΔF) according to the GFM droop characteristic. Figure 15 shows the droop characteristic (GFM droop characteristic) on the AC power distribution system 20 side in GFM control mode in Embodiment 1. The GFM droop characteristic represents a relationship in which the subtraction result (difference power ΔPy) output from the subtractor 6465 is input and the difference frequency ΔF is output.

[0156] The adder 6469 corrects the frequency command value by adding the output of the integrating circuit 6468 (difference frequency ΔF) to the frequency command value output from the fourth control circuit 647. The output of the adder 6469 is output to the inverter voltage control circuit 649 as the corrected frequency command value.

[0157] In Embodiment 1, the GFM droop characteristic circuit 6470 was configured with a subtractor 6466, a multiplier 6467, an integrator 6468, and an adder 6469, but it is not limited to this configuration. For example, similar effects can be obtained by storing the droop characteristic of the GFM control as table data and performing delay processing on the output of the droop characteristic using a first-order lag system model.

[0158] Figure 17 is a block diagram of the inverter current control circuit 648 shown in Figure 8. The inverter current control circuit 648 comprises a current command value generation circuit 6481, a subtractor 6482, a first PI control circuit 6483, and a first current limiting circuit 6484.

[0159] The current command value generation circuit 6481 generates a current command value based on sine wave information synchronized with the AC power distribution system voltage output from the first sine wave generation circuit 644 and the power command value output from the GFL control signal generation circuit 645.

[0160] The subtractor 6482 subtracts the measured AC current output from the ammeter 62 from the current command value output from the current command value generation circuit 6481.

[0161] The first PI control circuit 6483 performs PI control so that the output of the subtractor 6482 becomes "zero".

[0162] The first current limiting circuit 6484 limits the current command value output from the first PI control circuit 6483, that is, it limits the current command value so as not to exceed the current rating of the AC / DC conversion circuit 63. The output (control command value) of the first current limiting circuit 6484 is output to the first switching circuit 650.

[0163] Figure 18 is a block diagram of the inverter voltage control circuit 649 shown in Figure 8. The inverter voltage control circuit 649 comprises a second sine wave generation circuit 6491, a subtractor 6492, a second PI control circuit 6493, and a second current limiting circuit 6494.

[0164] The second sine wave generation circuit 6491 generates a voltage command value based on the phase information output from the phase detection circuit 641 (in Embodiment 1, although the details will be described later, the phase information is the zero-crossing point detection time information of the AC system voltage), the AC voltage command value information output from the fourth control circuit 647, and the frequency command value information output from the GFM control signal generation circuit 646.

[0165] The subtractor 6492 subtracts the measured AC voltage output from the voltmeter 61 from the voltage command value output from the second sine wave generation circuit 6491.

[0166] The second PI control circuit 6493 generates a current command value by performing PI control so that the output from the subtractor 6492 becomes "zero".

[0167] The second current limiting circuit 6494 limits the current command value output from the second PI control circuit 6493. That is, the second current limiting circuit 6494 limits the current command value so as not to exceed the current rating of the AC / DC conversion circuit 63. The output (control command value) of the first current limiting circuit 6484 is output to the first switching circuit 650.

[0168] Next, the drooping characteristics adopted in the power conversion device 9 for the distribution system battery in Embodiment 1 will be described. In Embodiment 1, a DC / DC converter installed in a DC distribution system is provided with a virtual synchronous generator control (VSG control) mechanism that simulates the inertial force, synchronizing force, and braking force of a synchronous generator to inverter equipment installed in an AC system. Below, the virtual synchronous generator control technology used in inverter equipment will be briefly described. The functions of a synchronous generator, such as that found in thermal power plants, include the function of adjusting the output power according to the frequency (governor function), the function of maintaining angular velocity (inertial force), the function of synchronizing with the AC system voltage (synchronizing force), the function of adjusting the voltage of the main system (AVR (Automatic Voltage Regulator) function), and the function of continuing operation even when there is an instantaneous drop in the AC system voltage that occurs during a system fault. In virtual synchronous generator control technology, the functions of a synchronous generator are simulated by controlling the transient response of a static inverter. Specifically, three functions are simulated: 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.

[0169] 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 a DC power distribution system. Embodiment 1 does not implement an AVR function. The governor function and the function simulating a mass system model based on motion equations will be described in detail below.

[0170] This section explains the function of a governor. In power plants, a governor controls the output of gas turbines and steam turbines in thermal or nuclear power plants, and 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 and hydroelectric power generators capable of output control have governors with droop characteristics, which control the power generation to increase 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 and hydroelectric power generators capable of output control have governors with droop characteristics, which control the power generation to decrease when the frequency increases. The Institute of Electrical Engineers of Japan provides standard models of governors that operate in this manner, such as models configured as first-order lag types.

[0171] Embodiment 1 describes the operation when the governor is approximated by a model configured with the above-described first-order lag system (see Equation 1). In Equation (1), -1 / Kgd represents the proportional gain of the governor (Kgd: speed adjustment rate), and Tg represents the time constant of the first-order lag system (Tg: governor time constant).

[0172] -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, supporting both demand and supply. Equation (2) shows the motion definition 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.

[0173] Tin - Tout = M × dω / dt + Dg × ω…(2) In Embodiment 1, the concept of equations (1) and (2) (drooping characteristics) is used to control the first DC / DC conversion circuit 93 in the power converter 9 for the distribution system battery installed in the DC distribution system, and the case in which inertial force and braking force are simulated in the DC distribution system 21 is described. For the AC / DC converter 6, the case in which only the mass system model shown in equation (2) is implemented as shown in Figure 12 is described. The same effect can be obtained by implementing virtual motor generator control using the governor model and the mass system model in the AC / DC converter 6. Similarly, in Embodiment 1, the case in which virtual motor generator control using the governor model and the mass system model is implemented to control the first DC / DC conversion circuit 93 in the power converter 9 for the distribution system battery is described, but it is not limited to this, and the same effect can be obtained by implementing the drooping characteristic table method or the mass system model, as in the case of the AC / DC converter 6.

[0174] The following describes the control modes implemented in the power conversion device 9 for the power distribution system battery in Embodiment 1. Specifically, two types of control modes will be described: a voltage control mode that gives the first DC / DC converter 93 a power-voltage droop characteristic (details will be described later, but refer to Figure 29) and a power control mode that gives it a voltage-power droop characteristic (details will be described later, but refer to Figure 30).

[0175] The following describes the voltage target generation circuit 942, which operates in a voltage control mode that provides power-voltage drooping characteristics, using Figures 19 to 21. Figure 19 is a block diagram of the voltage target generation circuit 942 shown in Figure 9. The voltage target generation circuit 942 comprises a subtractor 9421, a first governor control circuit 9422, an adder 9423, a subtractor 9424, and a first point mass calculation circuit 9425.

[0176] The subtractor 9421 calculates the differential voltage (ΔV) by subtracting the voltage command value (Vref1) output from the fifth control circuit 949 from the measured voltage of the voltmeter 96.

[0177] The first governor control circuit 9422 calculates a correction value (ΔPref1) for the power command value based on the differential voltage (ΔV) output from the subtractor 9421.

[0178] The adder 9423 generates a target control power value by adding a correction value (ΔPref1) of the power command value output from the first governor control circuit 9422 and the power command value (Perf1) output from the fifth control circuit 949.

[0179] The subtractor 9424 subtracts the measured effective power output from the second power calculation circuit 941 from the control power target value output from the adder 9423.

[0180] The first mass system calculation circuit 9425 corrects the voltage command value (Vref1) output from the fifth control circuit 949 based on the output from the subtractor 9424 and outputs it to the voltage target value control circuit 945. The output of the first mass system calculation circuit 9425 is also output to the fifth control circuit 949, and its value is stored in a memory (not shown). In Embodiment 1, the control parameters (speed adjustment rate Kgd1, governor time constant Tg1, inertia constant M1, and braking coefficient Dg1) of the first governor control circuit 9422 and the first mass system calculation circuit 9425 are notified from the CEMS 3 via the fifth control circuit 949.

[0181] Figure 20 is a block diagram of the first governor control circuit 9422 shown in Figure 19. The first governor control circuit 9422 includes a multiplier 94221, a first-order lag circuit (denoted as 1 / (1+s×Tg1) in the figure) 94222, and a first limiter circuit 94223.

[0182] The multiplier 94221 multiplies the output of the subtractor 9421 by the proportional gain output from the fifth control circuit 949 (denoted as -1 / Kgd1 in the figure).

[0183] The first-order lag circuit 94222 delays the output of the multiplier 94221 before outputting it. In Embodiment 1, the governor control will be described in which the standard model of the first-order lag system presented by the Institute of Electrical Engineers of Japan is used. Therefore, the first-order lag circuit 94222 implements the first-order lag system model (1 / (1+s×Tg1)).

[0184] The first limiter circuit 94223 applies limiter processing to the output of the first-order lag circuit 94222 and outputs it.

[0185] Figure 21 is a block diagram of the first point mass arithmetic circuit 9425 shown in Figure 19. The first point mass arithmetic circuit 9425 comprises a subtractor 94251, an integral circuit (denoted as 1 / (M1×s) in the figure) 94252, a multiplier 94253, and an adder 94254.

[0186] The subtractor 94251 subtracts the output of the multiplier 94253 from the output of the subtractor 9424 (the result of subtracting the target control power value from the measured effective power).

[0187] The integrating circuit 94252 calculates the difference voltage between the voltage target value and the voltage command value (Vref1) by multiplying the output of the subtractor 94251 by 1 / M1 and integrating it.

[0188] The multiplier 94253 multiplies the output of the integrating circuit 94252 by the damping coefficient (Dg1) output from the fifth control circuit 949.

[0189] The adder 94254 generates a target voltage value by adding the output of the integrating circuit 94252 and the voltage command value (Vref1) output from the fifth control circuit 949.

[0190] Here, we will explain the transfer function of the motion equation portion of the first point mass system calculation circuit 9425. The transfer function of the motion equation portion is expressed by equation (3).

[0191] (1 / M_v × s) / (1 + Dg_v / M_v × (1 / s)) = (1 / Dg_v) × (1 / (1 + (M_v / Dg_v) × s) ... (3) The transfer function of the motion equation part can be expressed as a first-order lag system (proportional gain: 1 / Dg_v, time constant: M_v / Dg_v), and the governor time constant (Tg_v) and the mass point calculation unit time constant (M_v / Dg_v) in the virtual synchronous generator control unit are determined based on the response speed required for the system. In the voltage target generation circuit 942 shown in Figures 19 to 21, Tg1 = Tg_v, Kgd1 = Kgd_V, M1 = M_V, and Dg1 = Dg_V correspond to these.

[0192] 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 22 to 24. Figure 22 is a block diagram of the power target generation circuit 943 shown in Figure 9. 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.

[0193] The subtractor 9431 calculates the differential power (ΔP) by subtracting the power command value (Pref2) output from the fifth control circuit 949 from the measured effective power output from the second power calculation circuit 941. The output of the subtractor 9431 is input to the second governor control circuit 9432.

[0194] The second governor control circuit 9432 calculates a correction value (ΔVref2) for the voltage command value based on the differential power (ΔP) output from the subtractor 9431.

[0195] The adder 9433 generates a target control voltage value by adding a correction value (ΔVref2) of the voltage command value output from the second governor control circuit 9432 and the voltage command value (Verf2) output from the fifth control circuit 949.

[0196] The subtractor 9434 subtracts the measured voltage from the voltmeter 96 from the control voltage target value output from the adder 9433.

[0197] The second mass system calculation circuit 9435 corrects the power command value (Pref2) output from the fifth control circuit 949 based on the output from the subtractor 9434 and outputs it to the power target value control circuit 946. The output of the second mass system calculation circuit 9435 is also output to the fifth control circuit 949, and its value is stored in a memory (not shown). In Embodiment 1, the control parameters (speed adjustment rate Kgd2, governor time constant Tg2, inertia constant M2, and braking coefficient Dg2) of the second governor control circuit 9432 and the second mass system calculation circuit 9435 are notified from the CEMS 3 via the fifth control circuit 949.

[0198] Figure 23 is a block diagram of the second governor control circuit 9432 shown in Figure 22. The second governor control circuit 9432 includes a multiplier 94321, a first-order lag circuit (denoted as 1 / (1+s×Tg2) in the figure) 94322, and a second limiter circuit 94323.

[0199] The multiplier 94321 multiplies the output of the subtractor 9431 by the proportional gain (denoted as -1 / Kgd2 in the figure) output from the fifth control circuit 949.

[0200] The first-order lag circuit 94322 delays the output of the multiplier 94321 before outputting it. In Embodiment 1, the governor control will be described in the same way as in Figure 20, using the standard first-order lag model presented by the Institute of Electrical Engineers of Japan. Therefore, the first-order lag circuit 94322 implements the first-order lag model (1 / (1+s×Tg2)).

[0201] The second limiter circuit 94323 applies limiter processing to the output of the first-order lag circuit 94322 and outputs it.

[0202] Figure 24 is a block diagram of the second point mass arithmetic circuit 9435 shown in Figure 22. The second point mass arithmetic circuit 9435 comprises a subtractor 94351, an integral circuit (indicated as 1 / (M2×s) in the figure) 94352, a multiplier 94353, and an adder 94354.

[0203] The subtractor 94351 subtracts the output of the multiplier 94253 from the output of the subtractor 9434 (the result of subtracting the target control voltage value from the measured voltage).

[0204] The integrating circuit 94352 calculates the difference in power between the power target value and the power command value (Pref2) by multiplying the output of the subtractor 94351 by 1 / M2 and integrating it.

[0205] The multiplier 94253 multiplies the output of the integrating circuit 94352 by the damping coefficient (Dg2) output from the fifth control circuit 949.

[0206] The adder 94354 generates a power target value by adding the output of the integrating circuit 94352 and the power command value (Pref2) output from the fifth control circuit 949.

[0207] Here, 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 voltage control mode. Similarly, 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 by the system. In the power target generation circuit 943 shown in Figures 22 to 24, Tg2 = Tg_v, Kgd2 = Kgd_V, M2 = M_V, and Dg2 = Dg_V correspond to these values.

[0208] Figure 28A is a block diagram for calculating the transfer function F(s) of the voltage target generation circuit 942 shown in Figure 19. The transfer function F(s)(ΔV / ΔP) of the block diagram shown in Figure 28A can be expressed by equation (4).

[0209]

[0210] Therefore, by the final value theorem, equation (5) holds in the steady state.

[0211]

[0212] Equation (5) corresponds to the slope of the drooping characteristic of the virtual synchronous generator control unit (1 / (Dg_v + 1 / Kgd_v)).

[0213] Figure 28B is a block diagram for calculating the transfer function F(s) of the power target generation circuit 943 shown in Figure 22. The slope of the drooping characteristic calculated from the transfer function F(s) is (1 / (Dg_p + 1 / Kgd_p)) from equation (6). Dg_p represents the damping coefficient in power control mode, and Kgd_p represents the speed adjustment rate in power control mode. In Figure 28B, M_p represents the inertia constant in power control mode, and Tg_p represents the governor time constant in power control mode.

[0214]

[0215] Figure 27 is a block diagram for calculating the transfer function F(s) of the GFM droop characteristic circuit 6470 within the GFM control signal generation circuit 646 shown in Figure 12. The transfer function F(s) (ΔV / ΔP) of the block diagram shown in Figure 27 is expressed by equation (7).

[0216]

[0217] From equation (7), the slope of the drooping characteristic is expressed by equation (8): 1 / (Dg_coefficience_ac)...(8) Figure 25 is a block diagram of the voltage target value control circuit 945 shown in Figure 9. The voltage target value control circuit 945 includes a subtractor 9451 and a third PI control circuit 9452.

[0218] The subtractor 9451 subtracts the measured voltage measured by the voltmeter 96 from the voltage target value output from the voltage target generation circuit 942.

[0219] The third PI control circuit 9452 PI controls the output of the subtractor 9451 so that the output of the subtractor 9451 becomes zero. The output of the third PI control circuit 9452 is output to the second switching circuit 947 as a control command for the first DC / DC conversion circuit 93.

[0220] Figure 26 is a block diagram of the power target value control circuit 946 shown in Figure 9. The power target value control circuit 946 includes a subtractor 9461 and a fourth PI control circuit 9462.

[0221] The subtractor 9461 subtracts the measured power calculation result calculated by the second power calculation circuit 941 from the power target value output from the power target generation circuit 943.

[0222] The fourth PI control circuit 9462 PI-controls the output of the subtractor 9461 so that the output of the subtractor 9461 becomes zero. The output of the fourth PI control circuit 9462 is output to the second switching circuit 947 as a control command for the first DC / DC conversion circuit 93.

[0223] Next, the operation overview of Embodiment 1 will be explained using the various drooping characteristics in Figures 13 to 16, 29, and 30, and Figures 31 to 34A and 34B. In Embodiment 1, the drooping characteristic implemented on the AC side of the AC / DC converter 6 is defined by the slope of the characteristic when the power output by the AC / DC converter 6 is divided by the converter's capacity and converted to a power unit (PU), and the frequency of the AC distribution system voltage is divided by the reference frequency of the AC distribution system (60 Hz in Embodiment 1) and converted to a PU. The drooping characteristics implemented on the DC side of the AC / DC converter 6 and the power conversion devices 9a to 9n for distribution system batteries are defined by the slope of the characteristic when the power output by each converter is divided by the capacity of each converter and converted to a PU, and the DC voltage output by each converter is divided by the reference voltage of the DC distribution system (1500 V in Embodiment 1) and converted to a PU.

[0224] Figures 13 to 16 show examples of droop characteristics implemented in the AC / DC converter 6 in Embodiment 1, as described above. Specifically, Figures 13 and 14 show examples of GFL (AC grid side) droop characteristics with a dead zone (shape of GFL droop characteristics table 6456) and DC droop characteristics (shape of DC droop characteristics table 6451) when the AC / DC converter 6 operates in GFL control mode. Figures 15 and 16 show examples of GFM (AC grid side) droop characteristics (shape of GFM droop characteristics) and DC droop characteristics with a dead zone (shape of DC droop characteristics table 6461) when the AC / DC converter 6 operates in GFM control mode. In these figures, ΔFmin and ΔFmax, which are listed in the AC side droop characteristics, represent the maximum and minimum difference values ​​from the frequency command value of the AC distribution system as defined in grid connection regulations, etc. Furthermore, -ΔFdead and ΔFdead represent the dead zone section of the GFL drooping characteristics in Embodiment 1, and ΔPmax and ΔPmin represent the difference power from the maximum power that can be supplied from the AC / DC converter 6. ΔVmin and Vmax, described in the DC drooping characteristics, represent the difference between the minimum and maximum voltages predetermined in the DC distribution system and the reference voltage, -ΔVdead and ΔVdead represent the dead zone section of the DC drooping characteristics in Embodiment 1, and ΔPmax and ΔPmin represent the difference power from the maximum power that can be supplied from the AC / DC converter 6.

[0225] Figure 29 shows an example of the drooping characteristics (power-voltage characteristics) implemented in the power converter 9 for distribution system batteries. Figure 30 shows an example of the drooping characteristics (voltage-power characteristics) implemented in the power converter 9 for distribution system batteries. In these figures, Pmax represents the maximum discharge power with respect to the converter's capacity, and -Pmax(Pmin) similarly represents the maximum charge power with respect to the converter's capacity. Vmax represents the maximum value within a predetermined range of the DC distribution system, and Vmin represents the minimum value within a predetermined range of the DC distribution system. In Embodiment 1, the predetermined voltage range of the DC distribution system is ±10% (1350V to 1650V) of the reference voltage of the DC distribution system. Vrang_max represents the upper limit of the predetermined voltage range, and Vrang_min represents the lower limit of the predetermined voltage range.

[0226] Figure 31 is a diagram illustrating the fluctuation range of the interconnection point voltage of each power converter 9 for distribution system batteries, taking into account changes in the power flow current through the DC distribution system 21. 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. Here, we 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) and each power converter 9x for distribution system batteries supplies ΔIbat_x (where x is a to d) for the increased demand power (current). For the sake of simplicity in this explanation, we will assume that the current (power flow) flowing through the DC distribution system 21 flows from the AC / DC converter 6 to the power converter 9d for the distribution system battery (forward current). In this case, when the power converters 9a to 9d for the distribution system battery are converted to power units (PU), if the same slope (identical) drooping characteristics are applied, the fluctuation range of the interconnection point voltage between each power converter 9 for the distribution system battery and the DC distribution system 21 will increase as you move towards the end of the power flow (power converter 9d for the distribution system battery). Therefore, in conventional control (when the drooping characteristics are the same), the amount of differential power allocated to the power converter 9 at the end of the power flow becomes larger.

[0227] Therefore, when the demand power of customer load groups 10a to 10d changes and the differential power is distributed by the output from the AC / DC converter 6 and each power converter 9 for distribution system batteries, it is necessary to consider the fluctuation range of the interconnection point voltage of the DC distribution system 21 for each converter due to the change in demand power. Specifically, it is necessary to consider the change in power flow current and the voltage drop of the DC distribution system 21 due to the distribution system impedance 7a to 7d. As a result, 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 31, the voltage fluctuation range will be larger for converters located downstream of the power flow (power converter 9d for distribution system batteries in this figure), and more power will be distributed compared to other converters. When the change in demand power 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. In Figure 31, with respect to “A⇒B”, A represents the current value before the change in power demand, and B represents the current value after the change in power demand.

[0228] In Embodiment 1, although a detailed explanation will be omitted, the slope of the drooping characteristic of each power converter 9 for distribution system batteries is determined based on the estimation result of the fluctuation range of the interconnection point voltage between each power converter 9 for distribution system batteries and the DC distribution system 21, thereby controlling the amount of differential power output by each power converter 9 to be approximately the same.

[0229] The following describes the various drooping characteristics implemented in the AC / DC converter 6 in Embodiment 1. Figures 32A, B, and C are diagrams illustrating the operation of the AC / DC converter 6 operating in GFL control mode in Embodiment 1.

[0230] In this explanation, the power converter 9a for the distribution system battery shown in Figure 31 manages the system voltage in voltage control mode (managing the DC system voltage using the drooping characteristic shown in Figure 29), and only the consumer load group 10a operates, while the power converters 9b to 9d for the distribution system battery and the consumer load groups 10b to d do not operate.

[0231] As shown in Figure 32A, the frequency of the AC distribution system voltage changes in a ramp-like manner from time t0 to t2. The operation of the AC / DC converter 6 and the power converter 9 for the distribution system battery will be explained when the customer load group 10a changes in a step-like manner at time t0, as shown in Figure 32B. Figure 32C shows the power output from the AC / DC converter 6 and the power converter 9 for the distribution system battery (indicated as "DC / DC converter" in the figure). In the interval from time t0 to t1, the GFL drooping characteristic is in the dead zone section shown in Figure 13, so the output of the GFL drooping characteristic table 6456 is "zero". On the other hand, the power shortage caused by the step-like change in the customer load group 10a is entirely borne by the power converter 9a for the distribution system battery, which initially operates in voltage control mode. When the power converter 9a for the distribution system battery starts supplying the power shortage, it lowers the voltage of the DC distribution system 21 based on the drooping characteristic shown in Figure 29. Consequently, the interconnection point voltage of the AC / DC converter 6 with the DC power distribution system 21 decreases. As a result, the DC-side drooping characteristic circuit 6453 in the GFL control signal generation circuit 645 increases the power output to the DC power distribution system 21 according to the drooping characteristic shown in Figure 14.

[0232] At time t1, the frequency of the AC distribution system 20 moves out of the dead zone of the GFL drooping characteristic shown in Figure 13. As a result, the AC / DC converter 6 increases the power supplied from the AC distribution system 20 in accordance with the GFL drooping characteristic. This is because the frequency of the AC distribution system 20 is rising, absorbing the excess power within the AC distribution system 20. Consequently, the amount of insufficient power supplied from the power converter 9a for the distribution system battery decreases, and the voltage of the DC distribution system 21 rises. As a result, the amount of correction of the power command value by the DC side drooping characteristic circuit 6453 decreases, and the power supplied to the customer load group 10a becomes dominant due to the GFL drooping characteristic. As described above, when the frequency fluctuation amplitude of the AC distribution system is small (within the dead zone), the AC / DC converter 6 can provide inertial force (excess or insufficient power) to the DC distribution system without being affected by the AC distribution system. The AC / DC converter 6, operating in GFL control mode, can suppress the influence of the AC distribution system (the inertial force it provides) by outputting a correction amount when there is an excess or deficiency of power on the DC distribution system 21 side, even when the frequency fluctuation amplitude of the AC distribution system is large (when it is outside the dead zone), thanks to the DC side droop characteristic circuit 6453. This minimizes the impact on the DC distribution system 21 as much as possible.

[0233] Figures 33A to 33D are diagrams illustrating the operation of the AC / DC converter 6 operating in GFM control mode in Embodiment 1. In this explanation, as in the case of GFL control mode, the power converter 9a for the distribution system battery shown in Figure 31 manages the system voltage in voltage control mode (managing the DC system voltage using the drooping characteristic shown in Figure 29), and only the customer load group 10a operates, while the power converters 9b to 9d for the distribution system battery and the customer load groups 10b to 10d do not operate.

[0234] As shown in Figure 33A, the frequency of the AC distribution system voltage changes in a ramp-like manner from time t4 to t2. The operation of the AC / DC converter 6 and the power converter 9 for the distribution system battery will be explained when the consumer load group 10a changes in a ramp-like manner from time t0 to t1 as shown in Figure 33B. Figure 33C shows the power output from the AC / DC converter 6 and the power converter 9 for the distribution system battery (indicated as "DC / DC converter" in the figure), and Figure 33D shows the interconnection point voltage of the AC / DC converter 6 with the DC distribution system. In the interval from time t0 to t3, the output of the DC side droop characteristic circuit 6463 of the AC / DC converter 6 is in the dead zone section shown in Figure 16, so the output of the DC droop characteristic table 6461 is "zero". On the other hand, the power shortage caused by the ramp-like change in the consumer load group 10a is entirely borne by the power converter 9a for the distribution system battery, which operates in voltage control mode. When the power converter 9a for the distribution system battery starts supplying insufficient power, it lowers the voltage of the DC distribution system 21 based on the drooping characteristics shown in Figure 29. Then, at time t3, the interconnection point voltage of the AC / DC converter 6 with the DC distribution system 21 moves out of the dead zone section of the DC drooping characteristic table 6461 shown in Figure 16. As a result, the AC / DC converter 6 increases the power it outputs to the DC distribution system 21 according to the drooping characteristics shown in Figure 16.

[0235] At time t4, the frequency of the AC power distribution system 20 increases in a ramp-like manner, as shown in Figure 33A. As a result, the AC / DC converter 6 increases the power supplied from the AC power distribution system 20 according to the GFM drooping characteristic. This is because the increasing frequency of the AC power distribution system 20 absorbs the excess power within the AC power distribution system 20. Consequently, the amount of insufficient power supplied from the power conversion device 9a for the power distribution system battery decreases, and the interconnection point voltage of the AC / DC converter 6 with the DC power distribution system 21 increases, as shown in Figure 33D.

[0236] At time t5, the output of the DC-side droop characteristic circuit 6463 of the AC / DC converter 6 enters the dead zone again, and the output of the DC droop characteristic table 6461 becomes "zero". As a result, similar to the GFL control mode, the output of the AC / DC converter 6 becomes dominant in supplying differential power to the consumer load group 10a.

[0237] As explained above, when the voltage fluctuation amplitude of the DC distribution system is small (within the dead zone), the AC / DC converter 6 operating in GFM control mode can provide inertial force (excess or deficit power) to the AC distribution system without being affected by the DC distribution system. When the voltage fluctuation amplitude of the DC distribution system is large (outside the dead zone), the AC / DC converter 6 operating in GFM control mode can supply excess or deficit power to the DC distribution system 21 by outputting a correction amount based on the output of the DC side droop characteristic circuit 6463. In GFM control mode, the AC / DC converter 6 operates as a voltage source (master), so when it is disconnected from the AC system by the switch 5 shown in Figure 1, if even one of the AC / DC converters 6 operating in GFM control mode is present, the AC and DC mixed microgrid below the switch 5 can transition to self-sustaining operation without momentary power interruption.

[0238] Next, a brief explanation will be given of the method for generating the drooping characteristics, including the voltage command value (Vref) and power command value (Pref) to be given to the power converter 9 for the distribution system battery in Embodiment 1. In Embodiment 1, the CEMS 3 creates the power command value (Pref) for the power converters 9a to 9n for the distribution system battery. Specifically, the operation plan creation circuit 34 shown in Figure 2 generates the power command value 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), the forecast results of supply power fluctuations due to the adjustment force (inertia force) output from the AC / DC converter 6, and the battery capacity SOC information of the distribution system batteries 8a to 8n.

[0239] The power for charging and discharging is allocated so that the difference between the supply and demand plan and the power consumption demanded by 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 batteries. In Embodiment 1, when allocating the power for charging and discharging, the power is allocated based on the battery capacity and SOC information so that the power for charging and discharging of the distribution system batteries 8a to 8n becomes zero or fully charged almost simultaneously. For the AC / DC converter 6, the power is allocated based on the supply and demand plan notified by the DSO2.

[0240] CEMS3 predicts the power flow current flowing through the DC distribution system based on the power allocation amounts for the AC / DC converter 6 and the distribution system batteries 8a to 8n (power converters 9a to 9n for distribution system batteries) and the prediction results of the above supply and demand forecast. CEMS3 estimates the distribution system impedance 7a to 7n in advance based on the voltage and current measurement results 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, and estimates the interconnection point voltage of each power converter 9 for distribution system batteries with the DC distribution system 21 based on the estimated distribution system impedance information and the current flow prediction results. CEMS3 generates the power allocation amount allocated to each power converter 9 for distribution system batteries as a power command value (Pref) and generates the estimated interconnection point voltage as a voltage command value (Vref).

[0241] Once the generation of power command values ​​(Pref) and voltage command values ​​(Vref) for each power converter 9 for distribution system batteries is complete, 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 demand fluctuations occur. At that time, CEMS 3 calculates the allocated (proportionalized) power to each converter (AC / DC converter 6 and each power converter 9 for distribution system batteries) of the excess or deficit power generated by the demand fluctuations and the supply power fluctuations due to the adjustment force (inertia force) output from the AC / DC converter 6. 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, CEMS 3 generates the DC side droop characteristic circuit 6453 (6463) of the AC / DC converter 6 and the shape of the droop characteristic, including the slope of the droop characteristic applied to 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 State of Control (SOC) of each distribution system battery 8 can be properly managed and operated.

[0242] Next, the operation of the power converter management device of Embodiment 1 will be explained with reference to Figures 1 to 50. Referring again to Figure 1, the power distribution system to which the power converter (AC / DC converter 6) according to Embodiment 1 is connected will be explained. In Embodiment 1, the AC power 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. In Embodiment 1, multiple DC microgrids 100, each including an AC / DC converter 6, are assembled to form a mixed AC and DC microgrid.

[0243] The AC / DC converter 6 converts the three-phase AC power input from the AC distribution system 20b into DC power (current) and outputs it to the DC distribution system 21. The DC power (current) 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 consists of a customer load 11 and a power converter 13 for customer PV. In Embodiment 1, the customer load 11 is assumed to consist of multiple customers (for example, approximately 50 to 150 general customers (single-family homes) are connected, and the power converter 13 for customer PV is assumed to be installed by multiple customers within the customer load group 10 and connected to the DC distribution system 21.

[0244] In Embodiment 1, as shown in Figure 1, the DC power distribution system 21 is configured by connecting n units in series, each unit consisting of a power distribution system impedance 7, a power conversion device 9 for the power distribution system battery, and a group of customer loads 10.

[0245] 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 voltage target generation circuit 942 and power target generation circuit 943 is implemented in the power converters 9a to 9n for distribution system batteries, thereby providing a pseudo-inertial force to the DC distribution system 21.

[0246] Here, we will explain the operation of the system that supports the DC power distribution system 21, which is 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 35 is a diagram illustrating the communication processing in CEMS 3.

[0247] The steady-state processing consists of two processes: one performed every 30 minutes and another every 5 minutes. Note that the processing cycles are not limited to 30 minutes and 5 minutes; the 30-minute cycle could be 1 hour or 15 minutes, and the 5-minute cycle could be 1 minute or 30 seconds.

[0248] In Figure 35, when the 30-minute cycle processing begins, DSO2 sends a request to CEMS3 via the communication line 22 to output the collected measurement data.

[0249] 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 and SOH of the distribution system battery 8) for 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 generation amount of the PV panel 12, and the charge / discharge power amount of the distribution system battery 8 over a 30-minute period by combining the 25-minute data collected in 5-minute cycles, and transmits these, along with information such as the SOC and SOH of the distribution system battery 8, to DSO2.

[0250] In Embodiment 1, each consumer in the demand load group 10 measures the maximum (actual) and minimum (actual) values ​​of their demand power (PV power generation power minus load power consumption) for a 5-minute period until they receive an output request for measurement data, and outputs the measurement results. Then, by combining this with 25 minutes of data collected in 5-minute cycles, the maximum and minimum supply and demand (maximum and minimum demand power supplied to the consumer load group 10) for each consumer load group 10 over a 30-minute period are determined. CEMS 3 calculates the maximum supply and demand difference value by subtracting the predicted supply and demand power within each consumer load group 10 (PV power generation power prediction result minus load power consumption prediction result) predicted during operation plan creation from the maximum supply and demand within each consumer load group 10. Similarly, CEMS 3 calculates the minimum supply and demand difference value by subtracting the predicted supply and demand power within each consumer load group 10 (PV power generation power prediction result minus load power consumption prediction result) predicted during operation plan creation from the minimum supply and demand within each consumer load group 10. CEMS3 constructs a database based on the date, time, day of the week, and actual weather conditions. In Embodiment 1, the database is constructed within the power consumption prediction database 352 shown in Figure 3, which will be described later. At that time, CEMS3 also stores the maximum (actual) and minimum (actual) values ​​of the power demand measured by each customer load group 10 over a 30-minute period. CEMS3 collects the maximum, minimum, average, and frequency distribution of the frequency fluctuation range of the AC distribution system measured by the first frequency detection circuit 642 from the AC / DC converter 6, and stores the collected results in the frequency fluctuation prediction database 353 connected to the frequency fluctuation prediction circuit 346 shown in Figure 3, which will be described later. The maximum, minimum, average, and frequency distribution of the frequency fluctuation range of the AC distribution system are performed by a frequency analysis circuit (not shown) in the fourth control circuit 647.

[0251] 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, CEMS3 generates an operation plan for the distribution system battery 8, control parameters (such as power command value (Pref) and voltage command value (Vref)), and droop characteristics for the AC / DC conversion circuit 63 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 methods for creating the operation plan, control parameters, and droop characteristics will be described later. Once the operation plan for the AC / DC converter 6 and the power distribution system battery 8, the creation of control parameters, and the generation of droop characteristics are complete, the CEMS 3 transmits the operation plan, control parameters, and droop characteristics to the AC / DC converter 6 and the power distribution system battery power converters 9a to 9n, and then terminates the 30-minute cycle processing.

[0252] 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 power 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. 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, or if the SOC of the distribution system battery 8 is charging above a predetermined value or discharging below a predetermined value, CEMS3 recalculates the operation plan (power target value (command value)). CEMS3 notifies the AC / DC converter 6 and the power converter 9 for each distribution system battery of the recalculation result. This embodiment relates to the control method of the AC / DC converter 6 that supplies inertial force to both AC and DC distribution systems, so a detailed explanation of the above recalculation operation is omitted.

[0253] Next, we will explain the detailed operation of CEMS3 using Figure 36. Figure 36 is a flowchart showing the control procedure of CEMS3.

[0254] In S100, CEMS3 starts estimating the system impedance. Figure 37 is a flowchart showing the system impedance estimation procedure in S100 of Figure 36.

[0255] In S1001, the operation plan creation unit management circuit 350 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 conversion device 9 for distribution system batteries, and the AC / DC converter 6 after the CEMS 3 is started. If measurement data has not been received (NO), the process proceeds to S1002. If measurement data has been received (YES), the process proceeds to S1003.

[0256] In S1002, the operation plan creation unit management circuit 350 notifies the system impedance estimation circuit 347 in Figure 3 of the initial value of the system impedance that has been set in advance, and ends the system impedance estimation in S100.

[0257] In S1003, the operation plan creation unit management circuit 350 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 new measurement data has not been collected (NO), the estimation of the system impedance in S100 is terminated.

[0258] On the other hand, if new measurement data has been collected (YES), the process proceeds to S1004.

[0259] In S1004, the operation plan creation unit management circuit 350 selects the distribution system section between the AC / DC converter 6 and the converter one step downstream (power conversion device 9 for distribution system battery).

[0260] In S1005, the operation plan creation unit management circuit 350 collects voltage and current information for each converter in the selected distribution system section and demand power information for each customer load group, and instructs the battery operation plan creation circuit 344 to estimate the power flow current. Upon receiving the power flow current estimation instruction, the battery operation plan creation circuit 344 instructs the power flow current estimation circuit 348 to estimate the power flow current.

[0261] In S1006, the power flow current estimation circuit 348 calculates the power flow current flowing through the selected section based on the collected measured values ​​of voltage, current, and power (see the current flowing through each distribution system impedance in Figure 31). Once the calculation of the power flow current is complete, the operation plan creation unit management circuit 350 instructs the system impedance estimation circuit 347 to estimate the impedance.

[0262] In S1007, upon receiving an instruction, the system impedance estimation circuit 347 estimates the impedance based on the voltage difference between the two selected converters (measured result) and the current flow.

[0263] In S1008, the operation plan creation unit management circuit 350 reads the impedance estimation result for the section from an impedance database (not shown), corrects the impedance estimation result using the current estimation result and the read impedance estimation result, and stores the corrected result in the database (reconstructs the database).

[0264] In S1009, the operation plan creation unit management circuit 350 checks whether the estimation of the impedance of all target distribution system sections has been completed. If it has been completed (YES), the impedance estimation in S100 is terminated. On the other hand, if it has not been completed (NO), the process proceeds to S1010.

[0265] In S1010, the following power distribution system section is selected. After that, the process returns to S1005.

[0266] When S100 is completed, the process proceeds to S101. In S101, the operation plan creation unit management circuit 350 checks whether or not there has been a request for output of measurement data from DSO2. If there has been a request for output (YES), the process proceeds to S102. If there has been no request for output (NO), the process proceeds to S104.

[0267] In S102, the operation plan creation unit management circuit 350 transmits 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, and collects the latest measurement information. The operation plan creation unit management circuit 350 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 350 updates the power generation prediction database 351 for the PV panels 12a to 12n and the power consumption prediction database 352 for the customer loads 11a to 11n within the operation plan creation circuit 34 using the collected measurement data.

[0268] At that time, the operation plan creation unit management circuit 350 calculates the following based on the measurement results of the maximum (actual measurement) and minimum (actual measurement) values ​​of the demand power (power obtained by subtracting the load power consumption from the PV power generation power) within the demand load group 10 described above over a 5-minute period.

[0269] The operation plan creation unit management circuit 350 calculates the maximum supply-demand power difference value by subtracting the supply-demand power forecast within the customer load group 10 (power obtained by subtracting the load power consumption forecast result from the PV power generation power forecast result) from the maximum supply-demand value. The operation plan creation unit management circuit 350 calculates the minimum supply-demand power difference value by subtracting the supply-demand power forecast within the customer load group 10 (power obtained by subtracting the load power consumption forecast result from the PV power generation power forecast result) from the minimum supply-demand value.

[0270] The operation plan creation unit management circuit 350 stores the maximum value of the maximum supply-demand power difference measured in the previous 25 minutes and the minimum value of the minimum supply-demand power difference measured in the previous 25 minutes in a database constructed based on the date, time, day of the week, actual weather conditions, etc.

[0271] As described above, in Embodiment 1, the maximum supply-demand power difference value and the minimum supply-demand power difference value for each consumer load group 10 are stored in the power consumption prediction database 352. At the same time, the maximum supply and minimum supply and demand power for each consumer load group 10 are also stored in the power consumption prediction database 352 along with the maximum supply-demand power difference value and the minimum supply-demand power difference value. Details of how to construct the database for the maximum supply-demand power difference value and the minimum supply-demand power difference value are omitted as they are not relevant to the points of this application.

[0272] In Embodiment 1, the maximum, minimum, average, and frequency distribution of the frequency fluctuation range of the AC power distribution system measured by the first frequency detection circuit 642 in the AC / DC converter 6 are stored in a frequency fluctuation prediction database 353 connected to the frequency fluctuation prediction circuit 346 shown in Figure 3. The maximum, minimum, average, and frequency distribution of the frequency fluctuation range of the AC power distribution system are performed by a frequency analysis circuit (not shown) in the fourth control circuit 647. Details of the method for constructing the frequency fluctuation prediction database 353 are omitted as they are not relevant to the points of this application.

[0273] In S103, the operation plan creation unit management circuit 350 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 for a 30-minute period. The calculated data is then transmitted to the DSO2 via the communication circuit 31, along with information such as the SOC and SOH of the distribution system batteries 8a to 8n and 25 minutes of data collected at 5-minute intervals stored in the memory circuit 32.

[0274] In Embodiment 1, once the transmission of measurement data is complete, the storage circuit 32 erases the measurement data collected during the 30-minute period. The process then proceeds to S104.

[0275] In S104, the operation plan creation unit management circuit 350 checks whether it has received a demand plan notification from DSO2. If it has been received (YES), the process proceeds to S105. If it has not been received (NO), the process proceeds to S106.

[0276] In S105, the operation plan creation unit management circuit 350 creates an operation plan. In Embodiment 1, the supply and demand plan for the power supplied from the main grid to the DC distribution system 21 is notified to the CEMS 3 in 30-minute cycles for 24 hours from the DSO 2.

[0277] Figure 38 is a flowchart showing the detailed procedure for the operation plan creation process (operation plan creation 1) in S105 of Figure 36.

[0278] In S1051, the operation plan creation unit management circuit 350 performs power generation forecasting for PV panels 12a to 12n. When the operation plan creation unit management circuit 350 receives a demand plan (battery operation plan) notification from DSO2, the distributed power management unit control circuit 36 ​​instructs the operation plan creation unit management circuit 350 in the operation plan creation circuit 34 to create an operation plan. Upon receiving the instruction, the operation plan creation unit management circuit 350 instructs the power generation forecast circuit 342 via the demand load forecast circuit 341 to forecast the power generated by PV panels 12a to 12n. Upon receiving the instruction, the power generation forecast circuit 342 obtains a 24-hour weather forecast from the weather forecast server 4 via the communication line 22. The power generation forecast circuit 342 uses the obtained results and data from the power generation forecast database 351 managed by the power generation forecast circuit 342 to forecast 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, the supply and demand plan for the DC distribution system 21 notified by the DSO2 is notified in 30-minute cycles for 24 hours. Therefore, a power generation prediction database 351 is constructed based on the actual power generation data, weather data, and time information (year, month, day, and time) of the PV panels 12a to 12n collected over a 30-minute period. Details of the method for constructing the power generation prediction database 351 are omitted as they are not relevant to the points of this invention.

[0279] In S1052, the operation plan creation management circuit 350 predicts the power consumption of the customer loads 11a to 11n. When the operation plan creation management circuit 350 receives the power generation prediction results for PV panels 12a to 12n from the power generation prediction circuit 342 via the demand load prediction circuit 341, it instructs the power consumption prediction circuit 343 via the demand load prediction circuit 341 to predict the power consumption of the customer loads 11a to 11n. Upon receiving the instruction, the power consumption prediction circuit 343 uses the data from the power consumption prediction database 352 managed by the power consumption prediction circuit 343 to predict the power consumption of the customer loads 11a to 11n for 24 hours. Similar to the power generation prediction database 351, the power consumption prediction database 352 is constructed based on the power consumption of the customer loads 11a to 11n collected over 30 minutes, along with date, time information, and weather information. The method of constructing the database is not relevant to the points of this invention and is therefore omitted.

[0280] In S1053, the operation plan creation unit management circuit 350 starts creating a demand plan. When the operation plan creation unit management circuit 350 receives the predicted power consumption results of the customer loads 11a to 11n from the power consumption prediction circuit 343 via the demand load prediction circuit 341, it calculates the total value of the charge and discharge power of the distribution system batteries 8a to 8n every 30 minutes (the difference in power between the demand prediction result and the power supply plan) based on the power generation prediction result of the PV panels 12a to 12n from the power generation prediction circuit 342, the power consumption prediction result of the customer loads 11a to 11n from the power consumption prediction circuit 343, and the demand plan notified from DSO2 (as described above, in Embodiment 1, the power supply plan for 24 hours planned for the DC distribution system 21 below substation 1 (power supply plan every 30 minutes)). Here, as described above, the power supply plan is a 24-hour power supply plan (for example, a power supply plan every 30 minutes) planned for the DC distribution system 21 below substation 1 in Embodiment 1.

[0281] In S1054, the operation plan creation management circuit 350 determines the charge and discharge power of the distribution system batteries 8a to 8n. Based on the SOC information of the distribution system batteries 8a to 8n collected in the memory circuit 32 via the communication circuit 31, and the battery capacity of the distribution system batteries 8a to 8n, the operation plan creation management circuit 350 determines (allocates) the charge and discharge power from each battery every 30 minutes. In Embodiment 1, when creating an operation plan for the batteries for 24 hours, the operation plan creation management circuit 350 determines an operation plan such that the SOC of the distribution system batteries 8a to 8n is almost simultaneously zero, almost simultaneously fully charged, or that all distribution system batteries 8 are still in a charge and discharge state after 24 hours.

[0282] The reason for formulating the operation plan in this manner is as follows. For example, if the charging power of the batteries 8a and 8b for the distribution system becomes zero, the customer loads 11a and 11b within customer load groups 10a and 10b will be supplied with power generated by PV panels 12a and 12b and power supplied from the DC distribution system 21. In this case, the other batteries 8c to 8n for the distribution system will supply the insufficient power within customer load groups 10c to 10n, so customer load groups 10a and 10b will be supplied with power from the AC / DC converter 6. As a result, the power supplied from the DC distribution system 21 to customer load groups 10a and 10b (Idc_a and Idc_b) will increase, causing a larger voltage drop at the distribution system impedances 7a and 7b. Consequently, the voltage at the grid connection point between the batteries 8a to 8n for the distribution system and the DC distribution system 21 will drop, and there may be cases where it deviates from 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.

[0283] Next, using Figure 39, we will explain the detailed operation of the power distribution system battery charging / discharging power (power command value) setting 1 in S1054. Figure 38 is a flowchart showing the detailed procedure of the power distribution system battery charging / discharging power (power command value) setting 1 in S1054.

[0284] In S10541, the operation plan creation unit management circuit 350 instructs the battery operation plan creation circuit 344 to generate power command values ​​for each power conversion device 9a to 9n for the distribution system battery. Upon receiving the instruction, the battery operation plan creation circuit 344 collects the predicted power generation amount of the PV panels 12a to 12n and the power consumption amount of the loads for the customer load groups 10a to 10n created in S1051 and S1052.

[0285] In S10542, the battery operation plan creation circuit 344 collects status information (SOC information in Embodiment 1) of the power distribution system batteries 8a to 8n.

[0286] In S10543, the battery operation plan creation circuit 344 calculates the demand (difference) power for each consumer load group 10 based on the power generation prediction results for each PV panel 12 and the power consumption prediction results for the consumer load 11 collected in S10541.

[0287] In S10544, the battery operation plan creation circuit 344 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. In Embodiment 1, the battery operation plan creation circuit 344 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 differential (surplus / deficit) power calculated in S10543 and the SOC information of the distribution system battery 8. Specifically, the battery operation plan creation circuit 344 calculates the surplus / deficit power within the customer load group 10 by subtracting the predicted power generation result of the PV panel 12 from the predicted power consumption of the customer load 11. At that time, the battery operation plan creation circuit 344 allocates the power supply planned in the supply and demand plan notified by DSO2 according to the size of the SOC of the distribution system battery 8. Simultaneously, the battery operation plan creation circuit 344 also generates a power command value (Pref) for the AC / DC converter 6. Specifically, the battery operation plan creation circuit 344 uses the power supply planned in the supply and demand plan notified by DSO2 as the power command value (Pref) for the AC / DC converter 6.

[0288] In S10545, the battery operation plan creation circuit 344 creates a power command value to be notified to each power distribution system battery power converter 9. Specifically, the battery operation plan creation circuit 344 calculates the power command value to be notified to each power distribution system battery power converter 9 by subtracting the demand power allocated in S10544 from the difference (surplus / deficit) power calculated in S10543.

[0289] In S10546, the battery operation plan creation circuit 344 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 conversion device 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. On the other hand, if it does not exceed the capacity (YES), the process proceeds to S10547.

[0290] In S10547, the battery operation plan creation circuit 344 checks whether it has generated power command values ​​(Pref) for all power converters 9 for the distribution system batteries. If the generation of power command values ​​(Pref) for all power converters 9 for the distribution system batteries has not been completed (NO), the process returns to S10545 and the power command value (Pref) for the next power converter 9 for the distribution system batteries is generated. On the other hand, if the generation of power command values ​​(Pref) for all power converters 9 for the distribution system batteries has been completed (YES), the battery operation plan creation circuit 344 notifies the operation plan creation unit management circuit 350 that it has been completed, and the process ends.

[0291] When S1054 in Figure 38 is completed, the process proceeds to S1055. In S1055, the operation plan creation unit management circuit 350 within the operation plan creation circuit 34 instructs the power flow current estimation circuit 348 to calculate the power flow current of the DC distribution system 21. Upon receiving the instruction to calculate the power flow current, the power flow current estimation circuit 348 instructs the system impedance estimation circuit 347 to output the impedance estimation results for the distribution system impedances 7a to 7n. Upon receiving the instruction, the system impedance estimation circuit 347 outputs the estimated distribution system impedance results to the power flow current estimation circuit 348.

[0292] The impedance estimation method of the system impedance estimation circuit 347 will be briefly explained. The system impedance estimation circuit 347 calculates the power flow through the distribution system impedances 7a to 7n based on the voltage measurement information at the interconnection points of the AC / DC converter 6 and each power conversion device 9a to 9n for distribution system batteries in the DC distribution system 21, received in 30-minute and 5-minute cycle processing, the output power measurement results of the AC / DC converter 6 and each power conversion device 9a to 9n for distribution system batteries, the power consumption of the consumer load 11 in the consumer load group 10, and the power generation measurement results of the PV panel 12. The system impedance estimation circuit 347 estimates the values ​​of the distribution system impedances 7a to 7n based on the interconnection point voltage measurement results of the AC / DC converter 6 and each power conversion device 9a to 9n for distribution system batteries in the DC distribution system 21 and the power flow calculation results. 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.

[0293] More specifically, a brief explanation will be given with reference to Figure 31. The system impedance estimation circuit 347 calculates the distribution system impedance 7a (= (Vdc_0 - Vdc_a) / Iacdc) based on the measured values ​​of the output voltage (Vdc_0) and current (Iacdc) of the AC / DC conversion circuit 63, and the measured value of the interconnection point voltage (Vbat_a (indicated as Vdc_a in Figure 31)) of the power converter 9a for the distribution system battery with the DC distribution system 21. The system impedance estimation circuit 347 reads the distribution system impedance 7a from a distribution system impedance estimation database (the calculation results are not shown) and modifies the distribution system impedance 7a read from the distribution system impedance estimation database by combining it with the previously calculated result. In Embodiment 1, the system impedance estimation circuit 347 calculates the corrected distribution system impedance 7a according to the formula: "corrected 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.

[0294] Next, the method for calculating the distribution system impedance 7b one level downstream will be explained. Specifically, the system impedance estimation circuit 347 calculates the excess or deficit power within the customer load group 10a (measured result of customer load 11 - measured result of power generation from PV panel 12), and subtracts the measured output power of the power converter 9a for distribution system batteries from the calculation result. Then, the system impedance estimation circuit 347 calculates I_a in Figure 31 by dividing this 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 347 uses this calculation result to determine the current (Iacdc - I_a) flowing through the distribution system impedance 7b. After that, the system impedance estimation circuit 347 calculates the distribution system impedance 7b using the same procedure as the distribution system impedance 7a described above.

[0295] In S1056, the power flow current estimation circuit 348 calculates the power flow current within the DC distribution system 21. Specifically, the power flow current estimation circuit 348 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. Then, the power flow current estimation circuit 348 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".

[0296] In S1057, a voltage prediction 1 is performed at the interconnection point of each power conversion device 9 for the power distribution system battery of the DC distribution system 21. Figure 40 is a flowchart showing the detailed procedure of the voltage prediction 1 at each receiving point in S1057 of Figure 38.

[0297] In S10571, the power current estimation circuit 348 reads the droop characteristic information of the AC / DC converter 6 from the memory circuit 32 via the operation plan creation unit management circuit 350.

[0298] In S10572, the power current estimation circuit 348 reads the power command value information (Pref) of the AC / DC converter 6 from the operation plan creation unit management circuit 350.

[0299] In S10573, the power current estimation circuit 348 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 described as the reference voltage (1500V).

[0300] In S10574, the power flow current estimation circuit 348 selects the power conversion device 9a for the power distribution system battery, which is one downstream of the AC / DC converter 6.

[0301] In S10575, the power flow current estimation circuit 348 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.

[0302] Two types of drooping 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 29 is a diagram showing an example of the drooping characteristics of the first DC / DC conversion circuit 93 operating in voltage control mode. Figure 30 is a diagram showing an example of the drooping characteristics of the first DC / DC conversion circuit 93 operating in power control mode. Figures 19 to 21 are block diagrams of the 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. Figures 22 to 24 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.

[0303] The characteristics of the voltage control mode and the power control mode will be described with reference to Figures 29, 30, and 34A and 34B.

[0304] The voltage control mode will now be explained. In the voltage control mode, the first DC / DC conversion circuit 93 (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 distribution system 21. Specifically, the first DC / DC conversion circuit 93 compares the DC voltage of the DC distribution system 21 with the voltage command value (Vref). If the DC voltage of the DC distribution system 21 is low, the first DC / DC conversion circuit 93 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 if charging). At that time, the first DC / DC conversion circuit 93 lowers the DC voltage of the DC distribution system 21 output by the first DC / DC conversion circuit 93 according to the drooping characteristic shown in Figure 29. On the other hand, the first DC / DC conversion circuit 93 determines that an excess of power is being supplied if the DC voltage of the DC power distribution system 21 is high, and reduces the discharge power of the power distribution system battery 8 (or increases the charging power during charging). In this case, 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 29.

[0305] As described above, in voltage control mode, the first DC / DC converter 93 controls the voltage at the interconnection point of the DC distribution system 21 based on the drooping characteristic shown in Figure 29, according to the power being charged and discharged. As a result, when the load fluctuates or the amount of power generated by the PV panel 12 fluctuates, the first DC / DC converter 93, operating in voltage control mode, first supplies the excess or insufficient power to the DC distribution system 21. At that time, the first DC / DC converter 93 controls the voltage of the DC distribution system based on the implemented drooping characteristic.

[0306] The characteristics of the voltage control mode will now be explained. In voltage control mode, the power converter 9 for distribution system batteries manages the interconnection point voltage of the DC distribution system 21, so 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 34A shows the response waveform when the customer load 11 in the customer load group 10a changes in a step-like manner in the configuration of Figure 31. For simplicity of explanation, the customer load groups 10b to 10d and the power converters 9b to 9d for distribution system batteries are assumed to be stopped.

[0307] 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 shown in Figure 34A, all of the differential power is supplied from the first DC / DC conversion 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 power control mode, supplies power based on the implemented drooping characteristics. Finally, in the example shown in Figure 34A, the power increased due to load fluctuations is distributed between the first DC / DC conversion circuit 93 and the AC / DC converter 6 in the power converter 9a for the distribution system battery.

[0308] 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 in accordance with 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 for the distribution system battery operating in voltage control mode first supplies 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, that is, it determines the management voltage based on the drooping characteristic. As a result the DC voltage of the DC distribution system 21 changes, 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 30.

[0309] The characteristics of the power control mode will now be explained. 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 operating in power control mode. At least one distributed power source operating in voltage control mode to manage the DC voltage of the DC distribution system 21 is required. When the power converter 9 and AC / DC converter 6 for the distribution system battery, operating in voltage control mode, are 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 9 and AC / DC converter 6, operating in voltage control mode as described above, supply excess power (differential power) and manage (output) the DC voltage of the DC distribution system 21 based on the drooping characteristic. The power converter 9 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. Similar to the voltage control mode, the customer load groups 10b to 10d and the power converters 9b and 9d for the distribution system battery are assumed to be stopped. In the AC / DC converter 6 operating in power control mode, as shown in Figure 34B, when there is a load fluctuation, the power converter 9a for the distribution system battery (operating in voltage control mode) supplies excess power (differential power) and controls the DC voltage of the DC distribution system 21 based on the drooping characteristic. Note that in this case, compared to the case where the two converters operate in voltage control mode (Figure 34A), the time it takes for the output of each converter to converge is longer. As a result, the interconnection point voltage of the AC / DC converter 6 to the DC distribution system 21 decreases, so the power converter 9b for the distribution system battery increases the discharge amount based on the drooping characteristic.

[0310] In voltage control mode, 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. 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) (see the drooping characteristic of power control mode shown in Figure 30), allowing operation to continue.

[0311] Let's continue the explanation by referring to Figure 40 again. In S10576, the power flow current estimation circuit 348 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 power distribution system battery.

[0312] In S10577, the power current estimation circuit 348 estimates the power current and outputs the estimation result to the grid voltage estimation circuit 349. The grid voltage estimation circuit 349 calculates the voltage drop value based on the power current estimation result.

[0313] In S10578, the power flow current estimation circuit 348 calculates the interconnection point voltage between the first DC / DC conversion circuit 93 in the selected power conversion device 9 for the power distribution system battery and the DC power distribution system 21, and outputs the calculation result to the operation plan creation unit management circuit 350.

[0314] In S10579, the power flow estimation circuit 348 uses the calculated interconnection point voltage with the DC distribution system 21 and the drooping characteristics 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. The power flow estimation circuit 348 corrects the power flow current calculation result of the DC distribution system 21 based on the calculated charge / discharge power. In Embodiment 1, when creating the 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 performed.

[0315] In S10580, the operation plan creation unit management circuit 350 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 have not been completed (NO), the process proceeds to S10581. If all checks have been completed (YES), the process ends.

[0316] In S10581, the operation plan creation unit management circuit 350 selects the first DC / DC conversion circuit 93 within the power converter 9 for the power converter 9 for the power converter 9 connected downstream of the selected power converter 9 for the

[0317] When step S1057 in Figure 38 is completed, the process proceeds to step S1058. In step S1058, the operation plan creation unit management circuit 350 generates the estimated grid connection point voltage of each power converter 9 for the DC distribution system 21 as a voltage command value (Vref).

[0318] In S1059, the operation plan creation unit management circuit 350 checks whether the estimated values ​​of the interconnection point voltages (receiving point voltages) of all power converters 9 for distribution system batteries estimated in S1057 with the DC distribution system 21 fall within a predetermined range. Embodiment 1 describes a case where the voltage range of the DC distribution system 21 is, for example, the reference voltage (1500V) ± 0.1 × reference voltage, and the predetermined range is, for example, the reference voltage ± 0.075 × reference voltage (2.5% is a margin in case of load fluctuations, etc.). The predetermined voltage range is set narrower than the voltage range of the DC distribution system 21. This is a measure to give the DC distribution system 21 inertia force due to the drooping characteristic shown in Figure 29 or Figure 30 when demand power fluctuations occur. (As shown in Figure 29 or Figure 30, the upper limit voltage is Vrange_max and the lower limit voltage is vrange_min). If the answer in S1059 is NO, the process proceeds to S1060.

[0319] In S1060, a review of the charging and discharging power of the power distribution system battery 8 is performed. Figure 41 is a flowchart showing the detailed procedure of the power distribution system battery charging and discharging power review 1 in S1060 of Figure 38.

[0320] In S10601, the operation plan creation unit management circuit 350 extracts power converters 9 for distribution system batteries whose estimated interconnection point voltage (receiving point voltage) with the DC distribution system 21, estimated in S1057, falls outside a predetermined range.

[0321] In S10602, the operation plan creation unit management circuit 350 determines whether the interconnection point voltage (receiving point voltage) of the power converter 9 for the distribution system battery, which has deviated from a predetermined range, is on the lower voltage side (less than Vrange_min). If it has deviated to the lower voltage side (less than Vrange_min) (if the answer in S10602 is YES), the process proceeds to S10603. If it has not deviated to the lower voltage side (less than Vrange_min) (if the answer in S10602 is NO), the process proceeds to S10613.

[0322] In S10603, the operation plan creation unit management circuit 350 selects the power converter 9 for the power distribution system battery (power converter 9a for the power distribution system battery) connected downstream of the AC / DC converter 6.

[0323] In S10604, the operation plan creation unit management circuit 350 collects the power command value (Pref) of the selected power converter 9 for the power distribution system battery.

[0324] 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 operating plan creation unit management circuit 350 deviates to the lower limit of the predetermined voltage range, it 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 power converter 9 for the distribution system batteries (increases the discharge power or decreases the charging power). If the operating plan creation unit management circuit 350 deviates to the upper limit of the voltage range, it 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 power converter 9 for the distribution system batteries (decreases the discharge power or increases the charging power).

[0325] In S10605, the operation plan creation unit management circuit 350 checks whether the power at the grid connection point (receiving point) of the selected power converter 9 for the distribution system battery has deviated from a predetermined voltage range. If the answer in S10605 is YES, the process proceeds to S10606. If the answer in S10605 is NO, the process proceeds to S10607.

[0326] In S10606, the operation plan creation unit management circuit 350 adds a constant α to the power command value (Pref) collected in S10604 (Pref = Pref + α).

[0327] In S10607, the operation plan creation unit management circuit 350 adds a constant β to the power command value (Pref) collected in S10604 (Pref = Pref + β). In Embodiment 1, α > β. This is to suppress incoming power flow by increasing the amount of correction for 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.

[0328] When processing S10606 or S10607 is completed, the process proceeds to S10608.

[0329] In S10608, the operation plan creation unit management circuit 350 checks whether the modified 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. If it does not exceed the limit (YES), the process proceeds to S10610.

[0330] In S10609, the operation plan creation unit management circuit 350 changes the power command value (Pref) to Pmax. Then the process proceeds to S10610.

[0331] In S10610, the operation plan creation unit management circuit 350 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 S10610 is NO, the process proceeds to S10611. If the answer in S10610 is YES, the process proceeds to S10612.

[0332] In S10611, the operation plan creation unit management circuit 350 selects the power converter 9 downstream of the selected power converter 9 for the power distribution system battery. After that, the process returns to S10604 and the process continues.

[0333] In S10613, the operation plan creation unit management circuit 350 selects the power converter 9 for the power distribution system battery (power converter 9a for the power distribution system battery) connected downstream of the AC / DC converter 6.

[0334] In S10614, the operation plan creation unit management circuit 350 collects the power command value (Pref) of the selected power converter 9 for the power distribution system battery.

[0335] In S10615, the operation plan creation unit management circuit 350 checks whether the power at the grid connection point (receiving point) of the selected power converter 9 for the distribution system battery has deviated from a predetermined voltage range. If the answer in S10615 is YES, the process proceeds to S10616. If the answer in S10615 is NO, the process proceeds to S10617.

[0336] In S10616, the operation plan creation unit management circuit 350 subtracts the constant γ from the power command value (Pref) collected in S10614 (Pref = Pref - γ).

[0337] In S10617, the operation plan creation unit management circuit 350 subtracts a constant ε from the power command value (Pref) collected in 10614 (Pref = Pref - ε). In Embodiment 1, γ > ε. This is to suppress the outflowing power flow (reduce discharge power or increase charging power) by increasing the amount of correction to the power command value of the power converter 9 for distribution system batteries when the grid connection point (receiving point) voltage deviates from a predetermined upper limit voltage range.

[0338] When processing in S10616 or S10617 is completed, the process proceeds to S10618. In S10618, the operation plan creation unit management circuit 350 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. If it does not exceed the limit (YES), the process proceeds to S10620.

[0339] In S10619, the operation plan creation unit management circuit 350 changes the power command value (Pref) to Pmin. Then the process proceeds to S10620.

[0340] In S10620, the operation plan creation unit management circuit 350 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. If the answer in S10620 is YES, the process proceeds to S10612.

[0341] In S10621, the operation plan creation unit management circuit 350 selects the power converter 9 downstream of the selected power converter 9 for the power distribution system battery. After that, the process returns to S10614 and the process continues.

[0342] In S10612, the operation plan creation unit management circuit 350 generates a power command value (Pref) for the AC / DC converter 6 based on the corrected power command values ​​of each distribution system battery power converter 9, 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 panel 12. Specifically, the operation plan creation unit management circuit 350 calculates the power command value (Pref) for the AC / DC converter 6 by subtracting the sum of the predicted power generation results of the PV panel 12 and the sum of the corrected power command values ​​of each distribution system battery power converter 9 from the sum of the predicted power consumption values ​​of each customer load 11.

[0343] In Embodiment 1, the operation plan creation management circuit 350 controls the power converter 9 for the distribution system battery to apply a larger offset to those whose grid connection point (receiving point) voltage deviates compared to those that do not deviate, but it is not limited to this. The operation plan creation management circuit 350 may determine the amount of offset to apply based on the magnitude of the SOC of the distribution system battery 8. For example, the operation plan creation management circuit 350 may apply a larger offset value to those with a large SOC, or apply a larger offset value to the power converter 9 for the distribution system battery that is closer to the input side of the power current. The operation plan creation management circuit 350 may also determine the amount of offset based on 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), or it may determine the amount of offset to apply based on the connection position of the power converter 9 for the distribution system battery or the direction in which the power current flows.

[0344] Once step S1060 in Figure 38 is completed, the process returns to S1056, and the operation plan creation unit management circuit 350 continues processing. If the answer to S1059 is YES, the operation plan creation unit management circuit 350 completes the creation of the voltage command value (Pref), and the process proceeds to S1061.

[0345] Figure 42 is a flowchart showing the detailed procedure for generating the drooping characteristic 1 in S1061 of Figure 38.

[0346] In S106101, the distributed power management control circuit 36 ​​in the CEMS3 shown in Figure 2 instructs the control parameter generation circuit 33 to generate the droop characteristics of each converter. Upon receiving the instruction, the power flow current fluctuation range estimation circuit 331 in the control parameter generation circuit 33 shown in Figure 4 collects the calculation results of the power flow currents flowing through each distribution system impedance 7 calculated in S1056.

[0347] In S106102, the demand power fluctuation prediction circuit 332 collects prediction results for the amount of power generated, power consumed, and AC distribution system frequency of the consumer PV.

[0348] In S106103, the demand power fluctuation prediction circuit 332 predicts the demand fluctuations (including the adjustment power fluctuations of the AC / DC converter 6) for each of the customer load groups 10.

[0349] Specifically, the demand power fluctuation prediction circuit 332 instructs the operation plan creation unit management circuit 350 within the operation plan creation circuit 34 to read the demand fluctuation range prediction information stored in the power consumption prediction database 352. Upon receiving the instruction to read the demand fluctuation range prediction information, the operation plan creation unit management circuit 350 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 customer 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. Similarly, the demand power fluctuation prediction circuit 332 notifies the operation plan creation unit management circuit 350 within the operation plan creation circuit 34 of the date, day of the week, time, and weather forecast information for the target time period, and reads the frequency fluctuation range prediction information stored in the frequency fluctuation prediction database 353.

[0350] 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, including adjustment force fluctuations based on frequency fluctuations), and the above demand power fluctuation range information (ends S106103).

[0351] In S106104, 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, in Embodiment 1, the demand power fluctuation prediction circuit 332 distributes the differential power in proportion to the power command values ​​(Pref) notified to each converter. The demand power fluctuation prediction circuit 332 may also allocate the 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 discharge power is allocated). Alternatively, the demand power fluctuation prediction circuit 332 may allocate the differential power to each converter based on the SOH information of the distribution system battery 8 (allocating a larger amount to the distribution system battery 8 that has not deteriorated as much). Alternatively, the demand power fluctuation prediction circuit 332 may distribute the differential power to each converter based on the ratio of the converter capacities of each converter. In Embodiment 1, the power difference (ΔP_diff_upper (upper limit) and (ΔP_diff_lower (lower limit)) between the power command value (Pref) assigned to each converter in S106104 is used to set the slope of the DC side drooping characteristic (see Figures 43A, B, and C).

[0352] 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 voltage at the system connection point 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 command value notified to each converter, the current (power) command value, the power flow current flowing through each distribution system impedance 7 collected in S106101, the estimated voltage at the connection point with the DC distribution system 21 for each converter, and the estimated system impedance result estimated in S100.

[0353] 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 prediction results, power consumption predictions, and frequency fluctuation prediction results of each consumer collected in S106102, the power demand fluctuation prediction results for the AC / DC converter 6 and each consumer 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.

[0354] For example, the power flow current fluctuation range estimation circuit 331 calculates the difference in power flow current flowing through the distribution system impedance 7a by dividing the allocated difference power by the voltage command value (Vref) for the AC / DC converter 6. Similarly, 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) 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 flow current flowing through the distribution system impedance 7x-1 (for example, distribution system impedance 7a when calculating the difference in power flow current of the distribution system impedance 7b).

[0355] More specifically, the power flow current fluctuation estimation circuit 331 calculates the difference in power flow current flowing through the distribution system impedance 7x by subtracting the differential power allocated to the power converter 9x-1 for distribution system batteries from the fluctuation in the demand power of the customer load group 10x-1, and then dividing the subtraction result by the voltage command value (Vref) of the power converter 9x-1 for distribution system batteries.

[0356] Once the estimation of the difference value 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 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 fluctuation range of the output power of each converter based on the allocation of the difference power of each converter allocated in S106104.

[0357] In S106106, the battery droop characteristic slope determination circuit 333 calculates the slope of the droop characteristic of the power converter 9 for distribution system batteries located in the DC distribution system 21. In the following description, it is assumed that the power converter 9a for distribution system batteries operates in voltage control mode (managing the DC voltage of the DC distribution system 21). Therefore, the battery droop characteristic slope determination circuit 333 calculates the voltage fluctuation range of the DC voltage at each converter terminal when the interconnection point voltage of the power converter 9a with the DC distribution system 21 is Vref (for example, 1500V), i.e., the voltage fluctuation range when the power current is at its maximum and the voltage fluctuation range when the power current is at its minimum, based on the power current fluctuation range estimation result output from the power current fluctuation range estimation circuit 331 and the distribution system impedance 7 estimated by the system impedance estimation circuit 347. In Embodiment 1, the battery droop characteristic slope determination circuit 333 determines the voltage fluctuation range of the power converter 9a for the power distribution system battery (V_diff_max and V_diff_min in Figure 43A) so that the voltage fluctuation range of the converter with the largest DC voltage fluctuation range (power converter 9d for power distribution system batteries in Figure 31 when the power flow is smooth) falls between Vrang_max and Vrang_min.

[0358] Specifically, the battery droop characteristic slope determination circuit 333 calculates ΔV_diff_max_d = Vrang_max - V_diff_max_d and ΔV_diff_min_d = Vrang_min - V_diff_min_d, where V_diff_max_d is the upper voltage and V_diff_min_d is the lower voltage of the converter with the largest fluctuation range (for example, the power converter 9d for distribution system batteries when the power flow is smooth in Figure 31), when the interconnection point voltage of the power converter 9a for distribution system batteries with the DC distribution system 21 is Pref (for example, 1500V). ΔV_diff_max_d and ΔV_diff_min_d are the upper and lower voltages of the voltage fluctuation range of the power converter 9a for distribution system batteries, respectively. Therefore, the upper voltage (V_diff_max_a) of the interconnection point voltage between the power conversion device 9a for the power distribution system battery and the DC power distribution system 21 is set to Vref + ΔV_diff_max_a, and the lower voltage (V_diff_min_a) is set to Vref + ΔV_diff_min_a. From this point onward, the upper voltage at the connection point between each converter and the DC distribution system 21 is set to Vref + ΔV_diff_max_a at the connection point of the power converter 9a for the distribution system battery, which operates in voltage control mode, and the battery droop characteristic slope determination circuit 333 calculates ΔV_diff_max_x (where x is b to d in the example of Figure 31; the AC / DC converter 6 also calculates the connection point voltage with the DC distribution system 21 under the same conditions and calculates ΔV_diff_max_acdc) based on the estimated result of the distribution system impedance 7 and the estimated result of the power flow (forward current is the minimum). Similarly, the battery droop characteristic slope determination circuit 333 sets the interconnection point voltage of the power converter 9a for the distribution system battery to the DC distribution system 21 as Vref + ΔV_diff_min_a, and based on the estimated distribution system impedance 7 and the estimated power flow (forward current is maximum), sets ΔV_diff_min_x (where x is b to d in the example of Figure 31), and determines the upper and lower limit voltages of the droop characteristics of each converter, including the AC / DC converter 6. Note that the interconnection point voltage with the DC distribution system 21 is also calculated for the AC / DC converter 6 based on the conditions, and ΔV_diff_min_acdc is calculated.

[0359] The battery droop characteristic slope determination circuit 333 determines the slope of the droop characteristic using the upper and lower voltage limits of the droop characteristic of each power converter 9 for distribution system batteries, and the maximum value (ΔP_diff_upper) and minimum value (ΔP_diff_upper) of the differential power allocated in S106104. Specifically, for converters operating in voltage control mode, the battery droop characteristic slope determination circuit 333 determines point A (ΔP_diff_upper, V_diff_max) and point B (ΔP_diff_lower, V_diff_min) shown in Figure 43A, and determines the slope of the straight line connecting point A and point B. The battery droop characteristic slope determination circuit 333 determines the slope of the droop characteristic by using the slope of the line connecting point A and point C, and the slope of the line connecting point C and point B, if the determined line does not pass through point C(0, Vref).

[0360] Similarly, for a converter operating in power control mode, the battery droop characteristic slope determination circuit 333 determines point A (V_diff_max, ΔP_diff_lower) and point B (V_diff_min, ΔP_diff_upper) shown in Figure 43B, and determines the slope of the line connecting point A and point B. If the determined line does not pass through point C (Vref, 0), the battery droop characteristic slope determination circuit 333 uses the slope of the line connecting point A and point C, and the slope of the line connecting point C and point B, as the droop characteristic slope.

[0361] When S106106 in Figure 42 is completed, the process proceeds to S10607. In S106107, the operation plan creation circuit 34 instructs the battery droop characteristic generation circuit 334 in the control parameter generation circuit 33 to generate the droop characteristics of each power converter 9 for distribution system batteries. Upon receiving the instruction, the battery droop characteristic generation circuit 334, in Embodiment 1, uses the control mode and the converter capacity of the power converter 9 for distribution system batteries to start generating control parameters in the voltage target generation circuit 942 or power target generation circuit 943 shown in Figure 19 or Figure 22. Specifically, the battery droop characteristic generation circuit 334 can calculate the slope of the droop characteristic from equation (6) as described above. The influence of the speed adjustment rate (Kgd1,2) on the droop characteristic is small. Therefore, in Embodiment 1, the battery droop characteristic generation circuit 334 generates the droop characteristic by keeping each control parameter (speed adjustment rate: Kgd1,2, and governor time constant Tg1,2) in the first governor control circuit 9422 constant and calculating the control parameters (speed adjustment rate: Dg1,2) in the first mass system calculation circuit 9425 based on equation (6). In Embodiment 1, the battery droop characteristic generation circuit 334 calculates the inertia constants (M1,2) using Dg1 (Dg2) calculated based on equation (6) so that M1 / Dg1 (M2 / Dg2) is constant (for example, 8 seconds).

[0362] When S106107 in Figure 42 is completed, the process proceeds to S106108. In S106108, the operation plan creation circuit 34 starts generating the DC and AC droop characteristics of the AC / DC converter 6. The AC / DC converter DC droop characteristic determination circuit 335 of the control parameter generation circuit 33 in Figure 4 determines the slope of the DC side droop characteristic. Specifically, similar to the case of the power converter for the distribution system battery 9, the AC / DC converter DC droop characteristic determination circuit 335 sets the interconnection point voltage of the power converter for the distribution system battery 9a with the DC distribution system 21, obtained in S106106, as Vref + ΔV_diff_max_a, and sets the interconnection point voltage of the AC / DC converter 6 with the DC distribution system 21 when the power current is at its minimum as ΔV_diff_max_acdc for each converter. Similarly, the AC / DC converter DC droop characteristic determination circuit 335 determines the upper and lower limit voltages of the DC droop characteristic of the AC / DC converter 6 by setting the interconnection point voltage of the power converter 9a for the distribution system battery to the DC distribution system 21 as Vref + ΔV_diff_min_a, and the interconnection point voltage of the AC / DC converter 6 to the DC distribution system 21 when the power current is at its maximum as ΔV_diff_min_acdc.

[0363] The AC / DC converter DC droop characteristic determination circuit 335 determines the slope of the droop characteristic using the upper and lower voltage limits, and the maximum (ΔP_diff_upper) and minimum (ΔP_diff_upper) differential power values ​​allocated in S106104, similar to the case of the droop characteristic of the power converter 9 for the power distribution system battery. Specifically, since the DC side droop characteristic of the AC / DC converter 6 operates in power control mode, when the AC / DC converter 6 operates in GFL control mode, in Embodiment 1, similar to the case of the power converter 9 for the power distribution system battery, points A (V_diff_max, ΔP_diff_lower) and B (V_diff_min, ΔP_diff_upper) shown in Figure 43B are determined, and the slope of the straight line connecting points A and B is determined. The AC / DC converter DC droop characteristic determination circuit 335, if the determined straight line does not pass through point C (Vref, 0), uses the slope of the straight line connecting point A and point C, and the slope of the straight line connecting point C and point B, as the slope of the droop characteristic.

[0364] When operating in GFM control mode, the AC / DC converter DC droop characteristic determination circuit 335 determines the slope of the line passing through point B and the dead zone start point F (Vref - ΔVdead, 0), and the slope of the line passing through point A and the dead zone end point E (Vref + ΔVdead, 0), as shown in Figure 43C, and uses these as the slope of the droop characteristic. Note that ±ΔVdead is shown in Figure 16.

[0365] The DC droop characteristic generation circuit 336 of the control parameter generation circuit 33 generates the droop characteristic of the AC / DC converter 6. In Embodiment 1, the AC / DC converter 6 is notified via the communication circuit 31 of the start and end coordinates of the droop characteristic, as well as the coordinates of two points in the droop characteristic, as shown in Figure 43B (without dead zone) or Figure 43C (with dead zone) (see Figure 72). Therefore, the DC droop characteristic generation circuit 336 calculates the coordinates of point C where the straight line (and its slope) calculated by the AC / DC converter DC droop characteristic determination circuit 335 intersects ΔPmin, and the coordinates of point D where it intersects ΔPmax.

[0366] The DC droop characteristic generation circuit 336 calculates the coordinates of points D, B, A, and C in GFL control mode, and the coordinates of points D, F, E, and C in GFM control mode, and outputs them to the transmission data generation circuit 35.

[0367] The AC / DC converter AC droop characteristic determination circuit 337 of the control parameter generation circuit 33 starts generating the AC side droop characteristic of the AC / DC converter 6. The method for generating the AC side droop characteristic (GFL droop characteristic) in GFL control mode will be described below. As shown in Figure 13, the GFL droop characteristic has a dead zone. In Embodiment 1, the control parameter generation circuit 33 instructs the frequency fluctuation prediction circuit 346 shown in Figure 3 to output the frequency distribution of frequency fluctuations from the frequency fluctuation prediction database 353 based on weather, date, day of the week, and time information. When the AC droop characteristic generation circuit 338 in the control parameter generation circuit 33 receives the frequency distribution of frequency fluctuations from the frequency fluctuation prediction circuit 346, in Embodiment 1 it determines the upper and lower limits of the dead zone frequency so that approximately 50% of the frequency fluctuations fall within the dead zone. The width of the dead zone does not need to be set so that frequency fluctuations account for 50% of the total frequency. It may be set to have no dead zone, or to account for other percentages such as 20%. Furthermore, if the transmission and distribution company or other relevant parties have regulations regarding interconnection, the dead zone should be set to a value based on those regulations.

[0368] The AC / DC converter AC droop characteristic determination circuit 337 determines the slope of the GFL droop characteristic. In Embodiment 1, the AC / DC converter AC droop characteristic determination circuit 337 determines the droop characteristic based on the adjustment force agreed upon in the supply and demand adjustment market. For example, if the frequency fluctuation range is agreed upon as ±0.1 Hz and 10% of the converter capacity, and the dead zone is ±Fdead (for example, ±0.04 Hz), the AC / DC converter AC droop characteristic determination circuit 337 determines points A and B as shown in Figure 44A. The AC / DC converter AC droop characteristic determination circuit 337 connects the dead zone start point F and point B with a straight line and calculates point D where the output from the AC / DC converter 6 is ΔPmax. Similarly, the AC / DC converter AC droop characteristic determination circuit 337 connects the dead zone end point E and point A with a straight line and calculates point D where the output from the AC / DC converter 6 is ΔPmin.

[0369] In the case of GFM control mode, the AC / DC converter AC droop characteristic determination circuit 337 determines the droop characteristic based on the adjustment force agreed upon in the supply and demand adjustment market. For example, if the frequency fluctuation range is agreed upon as ±0.1 Hz and 10% of the converter capacity, the AC / DC converter AC droop characteristic determination circuit 337 calculates the slope of the straight line connecting point A and point B, as shown in Figure 44B.

[0370] The AC droop characteristic generation circuit 338 generates a droop characteristic. In Embodiment 1, when in GFL control mode, the AC droop characteristic generation circuit 338 outputs the coordinates of points D, B, A, and C as a droop characteristic to the transmission data generation circuit 35. When in GFM control mode, the AC droop characteristic generation circuit 338 calculates the damping coefficient Dg from the slope of the straight line of the GFM droop characteristic based on equation (8), similar to the case of the power converter 9 for the power distribution system battery, and further generates an inertia constant M (such as M / Dg being constant (for example, 8 seconds)) using the damping coefficient Dg.

[0371] When the AC droop characteristic generation circuit 338 completes the generation of the AC side droop characteristic of the AC / DC converter 6, the distributed power management control circuit 36 ​​determines that the droop characteristic generation 1 in S1061 of Figure 38 is complete and terminates the operation plan creation 1 in S105 of Figure 36.

[0372] When the operation plan creation 1 in S105 of Figure 36 is completed, the process proceeds to S108. In S108, the operation plan creation unit management circuit 350 sends the created drooping characteristics (parameters), voltage command value (Vref), and power command value (Pref) to the AC / DC converter 6 and the power conversion devices 9a to 9n for the distribution system battery.

[0373] In S106, the operation plan creation circuit 34 checks whether it is the time to collect various measurement results (i.e., whether to start the 5-minute cycle processing). If it is not the time to collect the results (NO), the process returns to S100 and continues. If it is the time to collect the results (YES), the process proceeds to S107.

[0374] In S107, the operation plan creation circuit 34 instructs the transmission data generation circuit 35 to generate measurement data output request packets to transmit measurement data to the equipment connected to the DC distribution system 21 (AC / DC converter 6, power converters 9a to 9n for distribution system batteries, customer loads 11a to 11n, and power converters 13a to 13n for customer PV). When the transmission data generation circuit 35 receives the request to generate measurement data output request packets, it generates measurement data output request packets to be transmitted to each connected device and outputs the generated measurement data output request packets to the communication circuit 31. At that time, the transmission data generation circuit 35 notifies the operation plan creation circuit 34 and the distributed power management unit control circuit 36 ​​that it has output measurement data output request packets to the communication circuit 31.

[0375] When the distributed power management control circuit 36 ​​receives an output notification of a 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. Upon receiving the instruction, the communication circuit 31 transmits the measurement data output request packet from the transmission data generation circuit 35 and waits until the measurement data is received. Upon receiving the measurement data, the communication circuit 31 stores the measurement data in the storage circuit 32 and notifies the distributed power management control circuit 36 ​​that the measurement data has been received. Upon receiving the notification, the distributed power management control circuit 36 ​​instructs the transmission data generation circuit 35 to generate the next measurement data output request packet to request the measurement results of the next connected device. At the same time, the distributed power management control circuit 36 ​​also notifies the operation plan creation circuit 34 that the measurement data has been received. 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.

[0376] Once all measurement data has been collected, the operation plan creation management circuit 350 within the operation plan creation circuit 34 instructs the power generation prediction circuit 342 and the power consumption prediction circuit 343 via the demand load prediction circuit 341 to update the power generation prediction database 351 and the power consumption prediction database 352 based on the collected measurement data. At the same time, the operation plan creation management circuit 350 instructs the frequency fluctuation prediction circuit 346 via the AC / DC operation plan creation circuit 345 to update the frequency fluctuation prediction database 353 based on the collected frequency measurement results (specifically, updating the maximum, minimum, average, and frequency distribution of the frequency fluctuation range of the AC distribution system).

[0377] When the power generation prediction circuit 342 and the power consumption prediction circuit 343 receive an instruction, they calculate the amount of power generated by each PV panel 12 and the amount of power consumed by each customer load 11 over a 5-minute period from the received data in order to update the power generation prediction database 351 and the power consumption prediction database 352. They add these values ​​to the power generation and power consumption amounts stored in registers (not shown) and confirm whether it is the database update time. In Embodiment 1, as described above, the power generation prediction database 351 and the power consumption prediction database 352 construct the power generation amounts of PV panels 12a to 12n and the power consumption amounts of customer 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 addition data stored in registers (not shown) is cleared and used for adding the measurement data for subsequent 30-minute periods. Furthermore, as described above, the power consumption forecasting database 352 is updated with demand fluctuation range forecast information for each customer load group 10 based on the received measurement results.

[0378] When the frequency fluctuation prediction circuit 346 receives an instruction, it compares the maximum, minimum, and average values ​​of the frequency fluctuation range of the collected AC distribution system with the maximum and minimum values ​​of the frequency fluctuation range of the AC distribution system stored in a register (not shown) to date, generates the maximum and minimum values ​​of the frequency fluctuation range for 30 minutes, and adds the two average values ​​together. The frequency fluctuation prediction circuit 346 updates the frequency distribution result by adding the number of occurrences of each frequency stored in the register. The frequency fluctuation prediction circuit 346 checks whether the current time is the database update time. If it is the update time, the frequency fluctuation prediction circuit 346 calculates the maximum, minimum, average, and frequency distribution of the frequency fluctuation range of the AC distribution system for 30 minutes, and updates the database based on the date, time, day of the week, and weather information. At that time, the 30-minute addition data stored in the register (not shown) is cleared and used for adding measurement data for the following 30 minutes. A detailed explanation of the data stored in the database is omitted as it is not relevant to this application, but similar to the power consumption forecasting database 352 and the power generation forecasting database 351, the data stored in the frequency fluctuation forecasting database 353 is read, averaged, and then written back (updated) to the storage area from which the data was read.

[0379] In Figure 36, once the construction (updating) of the power generation forecast database 351, the power consumption forecast database 352, and the frequency fluctuation forecast database 353 in S107 is complete, the process proceeds to S109.

[0380] In S109, the operation plan creation unit management circuit 350 determines whether or not to terminate the operation of CEMS3. If it is to terminate (YES), the operation plan creation unit management circuit 350 stops the operation of CEMS3. If it is not to terminate (NO), the process returns to S100 and the process continues.

[0381] As described above, in Embodiment 1, AC-side drooping characteristics and DC-side drooping characteristics are implemented in the AC / DC converter 6 in order to impart inertial force to the AC distribution system 20 and the DC distribution system 21. DC-side drooping characteristics are implemented in the power converters 9a to 9n for distribution system batteries in order to ensure the system quality of the DC distribution system 21. The power converter management device (CEMS 3) uses the DC-side drooping characteristics, voltage command value (Vref), and power command value (Pref) provided to each converter to allocate the surplus or deficit power calculated based on information such as the supply and demand power command value of the AC / DC converter 6 notified from DSO2, the predicted power generation results of the consumer loads 11 in the consumer load groups 10a to 10n, the PV panels 12, and the SOC of each distribution system battery 8a to 8n to the power converters 9a to 9n (power command value (Pref)). The power converter management device (CEMS3) estimates the grid connection point (receiving point) voltage based on the estimated distribution system impedance of the DC distribution system 21, which is estimated based on actual measurement data, and generates a voltage command value (Vref) based on the estimated result.

[0382] At that time, the power converter management device (CEMS3) also estimates the fluctuation range of power output from the AC / DC converter 6 based on the frequency fluctuation range of the AC distribution system and the frequency distribution of the frequency fluctuation range. The power converter management device (CEMS3) determines the drooping characteristics of each converter based on the estimation results of the output power fluctuation range based on the frequency fluctuation of the AC system voltage of the AC / DC converter 6, and the estimation results of the fluctuation range of the supply and demand power of each customer load group 10. As a result, the voltage at the grid connection point (receiving point) of the DC distribution system 21 to which the AC / DC converter 6 and the power converters 9a to 9n for the distribution system battery are connected can be appropriately managed, and even when supply and demand power fluctuations occur, the differential power output from each converter can be appropriately allocated by the drooping characteristics, and the SOC of the distribution system battery 8 can be appropriately managed.

[0383] Next, the operation of the AC / DC converter 6 and the power conversion device 9 for the distribution system battery will be explained using Figures 5 to 34A, B and Figures 45 to 50. In Embodiment 1, the AC / DC converter 6 is controlled in power control mode on the DC distribution system 21 side, the power conversion device 9a for the distribution system battery is controlled in voltage control mode, and the power conversion devices 9b to 9n for the distribution system battery operate in either voltage control mode or power control mode. The operation of the AC / DC converter 6 will be explained below using Figure 5.

[0384] The AC / DC converter 6 operates in two control modes for the AC power distribution system 20: GFL control mode and GFM control mode. The AC / DC converter 6 is controlled to operate in power control mode for the DC power distribution system 21.

[0385] In Figure 5, voltmeters 61a and 61b measure the voltage of the three-phase AC system, and ammeters 62a and 62b measure the current of the three-phase AC system. The phase voltage and phase current of the unconnected voltmeters and ammeters are calculated using the results measured by each voltmeter 61 and each ammeter 62. The AC / DC conversion circuit 63 converts AC power to DC power, or DC power to AC power. The first control circuit 64 controls the AC / DC conversion circuit 63. The first communication interface circuit 65 communicates with CEMS 3, etc. Voltmeter 66 measures the voltage of the DC distribution system 21. Ammeter 67 measures the current of the DC distribution system 21. The measurement results of voltmeters 61a,b, ammeters 62a,b, voltmeter 66, and ammeter 67 are input to the first control circuit 64.

[0386] The detailed operation of the first control circuit 64 will be explained below using 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.

[0387] The first frequency detection circuit 642 calculates the frequency of the AC power distribution system voltage based on the zero-crossing point information (zero-crossing point detection time information in Embodiment 1) output from the phase detection circuit 641. Specifically, the first frequency detection circuit 642 calculates the frequency by measuring the time for one cycle of the AC power distribution system voltage by subtracting the previously detected zero-crossing point time information from the currently detected zero-crossing point time. At that time, the first frequency detection circuit 642 also stores the maximum, minimum, average, and frequency distribution of the measured frequencies detected within the 5-minute cycle (the measurement data collection cycle requested by CEMS 3) in a register (not shown). The values ​​in the register (not shown) are cleared to their initial values ​​each time a communication request is received from CEMS 3, and the maximum, minimum, average, and frequency distribution of the measured frequencies for the next cycle are collected.

[0388] The first power calculation circuit 643 measures the power output from the AC / DC converter 6 based on the DC system voltage output from the voltmeter 66 and the DC system current output from the ammeter 67.

[0389] The first sine wave generation circuit 644 generates a reference sine wave synchronized with the AC system voltage waveform of the AC distribution system 20b used for current control (used in GFL control mode) based on the frequency detection result output from the first frequency detection circuit 642, the zero-cross point information detected by the phase detection circuit 641 (input via the first frequency detection circuit 642), and the AC system voltage waveform output from the voltmeter 61.

[0390] The GFL control signal generation circuit 645 corrects the power command value notified from the CEMS 3 (input via the fourth control circuit 647) based on the frequency detection result output from the first frequency detection circuit 642, the power calculation result output from the first power calculation circuit 643, and the connection point voltage measurement result with the DC power distribution system 21 output from the voltmeter 66. The operation of the GFL control signal generation circuit 645 will be explained with reference to Figure 11.

[0391] The subtractor 6450 subtracts the DC voltage command value (notified from CEMS 3) output from the fourth control circuit 647 from the measured voltage at the connection point with the DC power distribution system 21 output from the voltmeter 66, and outputs the subtraction result to the DC droop characteristic table 6451 in the DC droop characteristic circuit 6453.

[0392] Figure 14 shows the DC droop characteristics in GFL control mode of Embodiment 1. Since the DC power distribution system 21 side of the AC / DC converter 6 operates in power control mode, the horizontal axis of the DC side droop characteristics shows the difference voltage obtained by subtracting the voltage command value output from the fourth control circuit 647 from the measured voltage output from the voltmeter 66. The vertical axis of the DC side droop characteristics shows the difference power correction value added to the power command value output from the fourth control circuit 647. In Embodiment 1, the DC side droop characteristics in GFL control mode will continue to be described assuming that there is no dead zone (prioritizing the inertial force (power) supplied to the DC power distribution system 21).

[0393] Returning to Figure 11, let's continue the explanation. The output of the DC droop characteristic table 6451 is input to the first-order lag circuit 6452. This is because if the correction value output from the DC droop characteristic table 6451 were output as is, it could cause disturbances in the DC power distribution system 21, or cause instability due to an excessively fast response speed. Therefore, in Embodiment 1, the first-order lag circuit 6452 eliminates the above-mentioned problems by delaying (suppressing high-frequency components) the output of the DC droop characteristic table 6451 before outputting it. The adder 6454 adds the output of the first-order lag circuit 6452 and the power command value (Pref) output from the fourth control circuit 647. The summation result is input to the adder 6459 and added to the output from the GFL droop characteristic circuit 6458.

[0394] The subtractor 6455 subtracts the frequency command value (Fref) output from the fourth control circuit 647 from the frequency detection result detected by the first frequency detection circuit 642 (ΔF), and inputs the result into the GFL droop characteristic table 6456 in the GFL droop characteristic circuit 6458.

[0395] Figure 13 shows the GFL drooping characteristics of Embodiment 1. The horizontal axis of the GFL drooping characteristics shows the difference frequency (ΔF) obtained by subtracting the frequency command value (Fref) output from the fourth control circuit 647 from the frequency detection result output from the first frequency detection circuit 642. The vertical axis of the GFL drooping characteristics shows the difference power (ΔW = ΔPy) added to the sum of the power command value output from the fourth control circuit 647 and the difference power ΔPx output from the DC side drooping characteristic circuit 6453 (output of adder 6454). In Embodiment 1, the GFL drooping characteristics are assumed to have a dead zone (±ΔFdead) (in order to prioritize the inertial force (power) supplied to the DC power distribution system 21).

[0396] Returning to Figure 11, the explanation continues. The output of the GFL droop characteristic table 6456 is input to the first-order lag circuit 6457. This is because, as with the DC droop characteristic table 6451, if the correction value given to the power command value output from the GFL droop characteristic table 6456 is output as is, it may cause problems such as disturbances in the AC power distribution system 20. Therefore, in Embodiment 1, the first-order lag circuit 6457 eliminates the above problems by delaying (suppressing high-frequency components) the output of the GFL droop characteristic table 6456 before outputting it. The adder 6459 adds the output of the first-order lag circuit 6457 and the output of the adder 6454. The summation result is input to the inverter current control circuit 648 as a corrected power command value.

[0397] Returning to Figure 8, the explanation continues. The GFM control signal generation circuit 646 corrects the frequency command value (input via the fourth control circuit 647) notified from the CEMS 3 based on the frequency detection result output from the first frequency detection circuit 642, the power calculation result output from the first power calculation circuit 643, and the connection point voltage measurement result with the DC power distribution system 21 output from the voltmeter 66. The operation of the GFM control signal generation circuit 646 will be explained with reference to Figure 12.

[0398] The subtractor 6460 subtracts the DC voltage command value (notified by CEMS 3) output from the fourth control circuit 647 from the measurement result of the interconnection point voltage with the DC power distribution system 21, which is input from the voltmeter 66. The subtraction result is input into the DC droop characteristic table 6461 in the DC droop characteristic circuit 6463.

[0399] Figure 16 shows the DC droop characteristics of Embodiment 1. Since the DC power distribution system 21 side of the AC / DC converter 6 operates in power control mode, the horizontal axis of the DC side droop characteristics shows the difference voltage obtained by subtracting the voltage command value output from the fourth control circuit 647 from the measured voltage output from the voltmeter 66. The vertical axis of the DC side droop characteristics shows the difference power correction value added to the power command value output from the fourth control circuit 647. In Embodiment 1, the DC side droop characteristics in GFM control mode are described as having a dead zone (±ΔVdead) (prioritizing the inertial force (power) supplied to the AC power distribution system 20).

[0400] Returning to Figure 12, the explanation continues. The output of the DC droop characteristic table 6461 is input to the first-order lag circuit 6462. This is because, as with the GFL control mode, if the correction value given to the power command value output from the DC droop characteristic table 6461 is output as is, it would cause disturbances in the DC power distribution system 21, or the response speed would be too fast, leading to instability. Therefore, in Embodiment 1, the first-order lag circuit 6462 eliminates the above-mentioned problems by delaying (suppressing high-frequency components) the output of the DC droop characteristic table 6461 before outputting it. The adder 6464 adds the output of the first-order lag circuit 6462 and the power command value (Pref) output from the fourth control circuit 647. The addition result is input to the subtractor 6465.

[0401] The subtractor 6465 calculates ΔPy by subtracting the output of the adder 6464 from the output of the first power calculation circuit 643.

[0402] The subtractor 6466 in the GFM droop characteristic circuit 6470 subtracts the output of the multiplier 6467 from the output of the subtractor 6465 (ΔPy). The result of the subtraction is input to the integrator 6468.

[0403] The integrating circuit 6468 divides the output of the subtractor 6466 by Moment_ac1 and integrates the result. The output (ΔF) of the integrating circuit 6468 is input to the multiplier 6467 and the adder 6469.

[0404] The multiplier 6467 multiplies the output of the integrating circuit 6468 by the damping coefficient (Dg_coefficiency_ac1) output from the fourth control circuit 647. The result of the multiplication is sent to the subtractor 6466.

[0405] The adder 6469 adds the output of the integrator 6468 and the frequency command value (Fref) output from the fourth control circuit 647. The summation result is input to the inverter voltage control circuit 649 as the frequency command value.

[0406] Let's return to Figure 8 and continue the explanation. The inverter current control circuit 648 controls the AC / DC conversion circuit 63 using a control method (current control) that outputs power in synchronization with the AC grid voltage. The operation of the inverter current control circuit 648 will be explained with reference to Figure 17.

[0407] The current command value generation circuit 6481 generates a current command value based on a sine wave synchronized with the voltage of the AC power distribution system 20b output from the first sine wave generation circuit 644, a power command value output from the GFL control signal generation circuit 645, and a voltage command value of the AC system voltage output from the fourth control circuit 647. Specifically, the current command value generation circuit 6481 divides the power command value output from the GFL control signal generation circuit 645 by the voltage command value of the AC system voltage output from the fourth control circuit 647, and generates a current command value by multiplying the division result by the sine wave synchronized with the voltage of the AC power distribution system 20b output from the first sine wave generation circuit 644.

[0408] The subtractor 6482 subtracts the AC system current output from the ammeter 62 from the current command value output from the current command value generation circuit 6481.

[0409] The output of the subtractor 6482 is input to the first PI control circuit 6483. The first PI control circuit 6483 performs PI control so that the output of the subtractor 6482 becomes zero. The control parameters for PI control are output from the fourth control circuit 647. The output of the first PI control circuit 6483 is input to the first current limiting circuit 6484, which limits the control command value and outputs it to the first switching circuit 650.

[0410] Returning to Figure 8, let's continue the explanation. The inverter voltage control circuit 649 controls the AC / DC conversion circuit 63 using a control method (voltage control) that controls it as a voltage source (master). The operation of the inverter voltage control circuit 649 will be explained with reference to Figure 18.

[0411] The second sine wave generation circuit 6491 generates a voltage command value for the AC system voltage to be output from the AC / DC conversion circuit 63, based on the zero-crossing point detection time information (phase information) output from the phase detection circuit 641, the frequency command value output from the GFM control signal generation circuit 646, and the voltage command value for the AC system voltage output from the fourth control circuit 647. Specifically, the second sine wave generation circuit 6491 uses the frequency command value output from the GFM control signal generation circuit 646 and the zero-crossing point detection time information output from the phase detection circuit 641 to calculate the phase when the frequency command value output from the GFM control signal generation circuit 646 is changed. The second sine wave generation circuit 6491 calculates the phase so that the value of the sine wave that has been output as the voltage command value up to the present time matches the value of the sine wave at the present time after the frequency command value has been changed. The second sine wave generation circuit 6491 generates a voltage command value using the calculated phase information, the frequency command value output from the GFM control signal generation circuit 646, and the AC voltage command value output from the fourth control circuit 647. The subtractor 6492 subtracts the AC system voltage output from the voltmeter 61 from the voltage command value output from the second sine wave generation circuit 6491.

[0412] The output of the subtractor 6492 is input to the second PI control circuit 6493. The second PI control circuit 6493 performs PI control so that the output of the subtractor 6492 becomes zero. The control parameters for PI control are output from the fourth control circuit 647. The output of the second PI control circuit 6493 is input to the second current limiting circuit 6494, where a limit is placed on the control command value, and then it is output to the first switching circuit 650.

[0413] Returning to Figure 8, the explanation continues. The first switching circuit 650 switches between the control command value output from the inverter current control circuit 648 and the control command value output from the inverter voltage control circuit 649 based on the control signal output from the fourth control circuit 647. Specifically, the first switching circuit 650 selects the output of the inverter current control circuit 648 when operating in GFL control mode, and selects the output of the inverter voltage control circuit 649 when operating in GFM control mode. The first PWM conversion circuit 651 applies PWM modulation to the output of the first switching circuit 650. The output of the first PWM conversion circuit 651 is output to the AC / DC conversion circuit 63 as a control command value. When the control command value is input to the AC / DC conversion circuit 63, it converts AC power to DC power, or DC power to AC power, and outputs it.

[0414] The fourth control circuit 647 manages the entirety of the first control circuit 64. The fourth control circuit 647 collects measurement results related to the DC power distribution system 21 output from the voltmeter 66 and ammeter 67, measurement results related to the AC power distribution system 20 output from the voltmeter 61 and ammeter 62, power measurement results calculated by the first power calculation circuit 643, frequency detection results detected by the first frequency detection circuit 642, power command values ​​generated by the GFL control signal generation circuit 645, and frequency command values ​​generated by the GFM control signal generation circuit 646. The fourth control circuit 647 notifies the CEMS 3 and other systems of the collected information via the first communication interface circuit 65. The effective voltage of the AC power distribution system 20b is also measured by an effective voltage measurement unit (not shown) and notified to the CEMS 3. Active power and reactive power information measured by active and reactive power measurement units of the AC system (not shown) is also notified to the CEMS 3 via the first communication interface circuit 65. The fourth control circuit 647 also collects the frequency analysis results (maximum value, minimum value, average value, frequency distribution, etc.) output from the first frequency detection circuit 642, and notifies the CEMS 3 of the collected information via the first communication interface circuit 65.

[0415] Figure 45 is a flowchart showing the control procedure of the first control circuit 64. In S201, the fourth control circuit 647 initializes various parameters within the first control circuit 64.

[0416] In S202, the fourth control circuit 647 sets the power command value to "zero" and the voltage command value to "1500V".

[0417] In S203, the fourth control circuit 647 collects information from various voltage and current sensors.

[0418] In S204, the fourth control circuit 647 controls the first AC / DC conversion circuit 63.

[0419] Figure 46 is a flowchart showing the procedure for controlling the first AC / DC conversion circuit in S204 of Figure 45.

[0420] In S2041, the fourth control circuit 647 acquires the measurement results from the AC voltmeters 61a and 61b.

[0421] In S2042, the fourth control circuit 647 instructs the phase detection circuit 641 to detect the phase of the AC distribution system voltage of the AC distribution system 20b. In Embodiment 1, as described above, the phase detection circuit 641 obtains the zero-crossing point detection time by detecting the zero-crossing point from the AC voltage waveform output from the AC side voltmeters 61a and 61b.

[0422] In S2043, the fourth control circuit 647 instructs the first frequency detection circuit 642 to detect the frequency. In Embodiment 1, as described above, the first frequency detection circuit 642 calculates the zero-crossing point detection period by subtracting the previously detected zero-crossing point time from the currently detected zero-crossing point detection time, and calculates the frequency by taking the reciprocal of the calculation result. The method for detecting the frequency of the AC power system voltage is not limited to the method using the zero-crossing point detection result. In Embodiment 1, the phase of the AC power distribution system 20b is determined using the zero-crossing point detection time.

[0423] In S2044, the fourth control circuit 647 collects the measurement results of the voltage and current on the DC system side (measurement results from the voltmeter 66 and the ammeter 67).

[0424] In S2046, the fourth control circuit 647 collects the calculation result of the effective power to be output from the AC / DC converter 6 to the DC power distribution system 21, which has been calculated by the first power calculation circuit 643.

[0425] In S2047, the fourth control circuit 647 checks whether it is in GFL control mode. If it is in GFL control mode (YES), the process proceeds to S2048; otherwise, it proceeds to S2049.

[0426] In S2048, the fourth control circuit 647 instructs the GFL control signal generation circuit 645 to generate a power command value, and instructs the inverter current control circuit 648 to generate a control command value to control the AC / DC conversion circuit 63 based on the power command value. At the same time, the fourth control circuit 647 instructs the first switching circuit 650 to select the output of the inverter current control circuit 648.

[0427] Figure 47 is a flowchart showing the GFL control procedure in S2048 of Figure 46. In S20481, the GFL control signal generation circuit 645 acquires the sine wave information output from the first sine wave generation circuit 644.

[0428] In S20482, the GFL control signal generation circuit 645 generates differential power ΔPx based on the DC-side drooping characteristic, as described above.

[0429] In S20483, the GFL control signal generation circuit 645 generates the differential power ΔPy based on the GFL drooping characteristics, as described above.

[0430] In S20484, the GFL control signal generation circuit 645 corrects the input power command value using the differential power ΔPx and the differential power ΔPy, as described above.

[0431] In S20485, the current command value generation circuit 6481 shown in Figure 17 generates a current command value. Specifically, the current command value generation circuit 6481 divides the power command value generated in S20484, which is output from the GFL control signal generation circuit 645, by the AC voltage command value output from the fourth control circuit 647 (the command value used here is the command value converted to the effective value of the AC voltage). The current command value generation circuit 6481 calculates the current command value by multiplying the division result by a sine wave synchronized with the AC voltage of the AC power distribution system 20, which is output from the first sine wave generation circuit 644.

[0432] Returning to Figure 47, let's continue the explanation. In S20486, the subtractor 6482 subtracts the output of the ammeter 62 from the current target value calculated in S20485. The first PI control circuit 6483 performs PI control on the output of the subtractor 6482.

[0433] In S20487, the first current limiting circuit 6484 limits the current command value which is the output of the first PI control circuit 6483.

[0434] Returning to Figure 46, let's continue the explanation. In S2049, the fourth control circuit 647 instructs the GFM control signal generation circuit 646 to generate a frequency command value, and instructs the inverter voltage control circuit 649 to generate a control command value to control the AC / DC conversion circuit 63 based on the frequency command value. At that time, the fourth control circuit 647 instructs the first switching circuit 650 to select the output of the inverter voltage control circuit 649.

[0435] Figure 48 is a flowchart showing the GFM control procedure in S2049 of Figure 46. In S20491, the GFM control signal generation circuit 646 generates differential power ΔPx based on the DC side drooping characteristic, as described above.

[0436] In S20492, the GFM control signal generation circuit 646 generates the difference frequency ΔF based on the GFM drooping characteristic, as described above.

[0437] In S20493, the GFM control signal generation circuit 646 corrects the input frequency command value by the difference frequency ΔF, as described above.

[0438] In S20494, the second sine wave generation circuit 6491 generates a voltage control target value. Specifically, the second sine wave generation circuit 6491 calculates the phase of the sine wave that will be the voltage control target based on the frequency command value generated in S20493, which is output from the GFM control signal generation circuit 646, and the zero-crossing point detection time (phase information) output from the phase detection circuit 641. The second sine wave generation circuit 6491 generates a voltage control target value using the phase calculation result, the frequency command value information, and the AC voltage command value (the amplitude of the AC distribution system voltage used here) output from the fourth control circuit 647. The subtractor 6492 subtracts the measured voltage measured by the voltmeter 61 from the voltage control target value (output of the second sine wave generation circuit 6491) generated in S20494, and inputs the subtraction result to the second PI control circuit 6493.

[0439] In S20495, the second PI control circuit 6493 applies PI control to the output of the subtractor 6492. The second current limiting circuit 6494 limits the current command value, which is the output of the second PI control circuit 6493. This terminates the GFM control.

[0440] When S2048 or S2049 is completed, the process proceeds to S2050. In S2050, the first PWM modulation circuit 651 applies PWM modulation to the control command value output from the first switching circuit 650 and outputs it to the AC / DC conversion circuit 63. This completes the control of the first AC / DC conversion circuit.

[0441] Returning to Figure 45, let's continue the explanation. In S205, the fourth control circuit 647 checks whether or not it has received a request to transmit measurement information from CEMS 3. If it has received a transmission request from CEMS 3 (YES), the process proceeds to S206; if it has not received a transmission request from CEMS 3 (NO), the process proceeds to S207.

[0442] In S206, the fourth control circuit 647 outputs the measurement information stored in a memory (not shown) to the first communication interface circuit 65. Upon receiving the measurement data from the fourth control circuit 647, the first communication interface circuit 65 converts it to a predetermined format and sends it to the CEMS 3 via the communication line 22. The process then proceeds to S207.

[0443] In S207, the fourth control circuit 647 checks whether it has received control information (voltage command value, power command value, information regarding drooping characteristics, etc.) from the CEMS 3. If it has not received the information (NO), the process returns to S203 and continues. If it has received the information (YES), the process proceeds to S208.

[0444] In S208, the fourth control circuit 647 sets the control mode (GFL / GFM control mode), power command value (Pref), voltage command value (Vref), frequency command value (Fref), DC side droop characteristic, AC side droop characteristic, and PI control parameters of the AC converter 6 in a register within the fourth control circuit 647 (not shown). After that, the process returns to S203 and the process continues.

[0445] Next, the operation of the power converter 9 for the power distribution system battery will be explained with reference to Figures 6, 9, 19-26, 29, 30, 49, and 50.

[0446] Figure 6 is a block diagram of the power converter 9 for a power distribution system battery. Embodiment 1 describes a case in which the power converter 9 for a power distribution system battery has two modes: voltage control mode and power control mode. In Embodiment 1, when the power converter 9 for a power distribution system battery is operated in voltage control mode, the voltage target generation circuit 942 shown in Figure 9 generates a power target value. Then, the 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 voltage target generation circuit 942. When the power converter 9 for a power distribution system battery is operated in power control mode, the power target generation circuit 943 generates a power target value. Then, the power target value control circuit 946 generates a current command value to control the first DC / DC conversion circuit 93 based on the power target value generated by the power target generation circuit 943.

[0447] Hereinafter, the detailed operation of the second control circuit 94 will be described with reference to FIG. 9. The second power calculation circuit 941 multiplies the DC voltage of the power converter 9 for a distribution system storage battery measured by the voltmeter 96 by the DC current of the power converter 9 for a distribution system storage battery measured by the ammeter 97, thereby calculating the actually measured charge / discharge power of the power converter 9 for a distribution system storage battery. The actually measured charge / discharge power may also be calculated using the voltage measurement result and current measurement result of the distribution system storage battery 8 measured by the voltmeter 91 and the ammeter 92. The actually measured charge / discharge power calculated by the second power calculation circuit 941 is input to a voltage target generation circuit 942, a power target generation circuit 943, a power target value control circuit 946, and a fifth control circuit 949. In Embodiment 1, the fifth control circuit 949 manages the measurement information measured by the voltmeters 91 and 96 and the ammeters 92 and 97, the charge / discharge power information calculated by the second power calculation circuit 941, and the SOC and SOH of the distribution system storage battery 8 calculated from the charge / discharge power information. The measurement information, charge / discharge power, SOC, and SOH are stored in a memory (not shown), and when a transmission request for measurement data is received from CEMS 3, they are output to CEMS 3 via the second communication interface circuit 95. SOH is estimated based on temperature information of the distribution system storage battery 8 measured by a thermometer (not shown), voltage transition information of the distribution system storage battery 8, charge / discharge power, duration when SOC is 90% or higher, and the like.

[0448] When the power calculation result is input from the second power calculation circuit 941, the voltage target generation circuit 942 starts generating a voltage target value. Hereinafter, the operation of the voltage target generation circuit 942 will be described with reference to FIGS. 19 to 21.

[0449] In FIG. 19, the voltage command value (Vref1) output from the fifth control circuit 949 is input to a subtracter 9421 and a first mass-point system arithmetic circuit 9425.

[0450] The subtracter 9421 subtracts the voltage command value (Vref1) from the measurement result of the voltage of the DC distribution system 21 measured by the voltmeter 96, and outputs the result to the first governor control circuit 9422. In Embodiment 1, the first governor control circuit 9422 uses a first-order lag system model as shown in Formula (1).

[0451] FIG. 20 is a diagram showing the detailed configuration of a first governor control circuit 9422. A multiplier 94221 multiplies the output of a subtractor 9421 by -1 / Kgd1 output from a fifth control circuit 949, and outputs the multiplication result to a first-order lag circuit (1 / (1+s×Tg1)) 94222. A first limiter circuit 94223 limits the output of the first-order lag circuit 94222 to a predetermined range, and outputs the limited output from the first governor control circuit 9422.

[0452] Returning to FIG. 19, the description will be continued. An adder 9423 adds the output of the first governor control circuit 9422 and a power command value (Pref1) output from the fifth control circuit 949.

[0453] A subtractor 9424 subtracts the output of a second power calculation circuit 941 from the output of the adder 9423, and outputs the subtraction result to a first mass-point system arithmetic circuit 9425. In the first embodiment, the first mass-point system arithmetic circuit 9425 uses a swing equation model as shown in Equation (2).

[0454] FIG. 21 is a diagram showing the detailed configuration of the first mass-point system arithmetic circuit 9425. A subtractor 94251 subtracts the output of a multiplier 94253 from the output of the subtractor 9424.

[0455] An integration circuit 94252 multiplies the subtraction result output from the subtractor 94251 by 1 / M1 (M1 is input from the fifth control circuit 949) and performs integration. The output of the integration circuit 94252 is input to the multiplier 94253 and an adder 94254. The multiplier 94253 multiplies the output of the integration circuit 94252 by a damping coefficient (Dg1) output from the fifth control circuit 949, and outputs the multiplication result to the subtractor 94251. The adder 94254 adds the output of the integration circuit 94252 and a voltage command value (Vref1), and outputs the addition result from the first mass-point system arithmetic circuit 9425 as voltage target value information.

[0456] The output of a voltage target generation circuit 942 is input to a voltage target value control circuit 945 and the fifth control circuit 949. In the first embodiment, the voltage target generation circuit 942 generates the voltage target value in the manner described above.

[0457] Figure 25 shows the configuration of the voltage target value control circuit 945. The subtractor 9451 subtracts the measured voltage measured by the voltmeter 96 from the voltage target value input from the voltage target generation circuit 942. The subtraction result is input to the third PI control circuit 9452. The third PI control circuit 9452 applies PI control to the output of the subtractor 9451 so that the output of the subtractor 9451 becomes zero. The output of the third PI control circuit 9452 is input to the second switching circuit 947 as a control command for the first DC / DC conversion circuit 93.

[0458] 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 with reference to Figures 22 to 24.

[0459] 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 it 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).

[0460] Figure 23 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.

[0461] Returning to Figure 22, let's continue the explanation. The adder 9433 adds the output of the second governor control circuit 9432 and the voltage command value (Vref2) output from the fifth control circuit 949. 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 mass system calculation circuit 9435. In Embodiment 1, the second mass system calculation circuit 9435 uses a motion equation model as shown in equation (2).

[0462] Figure 24 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.

[0463] The integrating circuit 94352 multiplies the subtraction result output from the subtractor 94351 by 1 / M2 (M2 is input from the fifth control circuit 949) and integrates it. The output of the integrating circuit 94352 is input to the multiplier 94353 and the adder 94354.

[0464] The multiplier 94353 multiplies the output of the integrating circuit 94352 by the damping coefficient (Dg2) output from the fifth control circuit 949 and outputs the result to the subtractor 94351. The adder 94354 adds the output of the integrating circuit 94352 to the power command value (Pref2) and outputs the sum as power target value information from the second mass system calculation circuit 9435.

[0465] 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.

[0466] Figure 26 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 input from the power target generation circuit 943. The fourth PI control circuit 9462 applies PI control to the output of the subtractor 9461 so that the output of the subtractor 9461 becomes zero. The output of the fourth PI control circuit 9462 is input to the second switching circuit 947 as a control command value for the first DC / DC conversion circuit 93.

[0467] Returning to Figure 9, let's continue the explanation. The second switching circuit 947 switches between the output of the 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 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 the power converter 9 for the power distribution system battery in power control mode. The output of the second switching circuit 947 is input to the current limiting circuit 948.

[0468] The current limiting circuit 948 applies current limiting to the output of the first DC / DC conversion circuit 93 when the output power of the first DC / DC conversion circuit 93 exceeds a predetermined value. In Embodiment 1, a PWM modulation circuit (not shown) in the current limiting circuit 948 applies PWM modulation to the current command value to which the current limiting has been applied, and outputs it to the first DC / DC conversion circuit 93.

[0469] Figure 49 is a flowchart showing the control procedure of the second control circuit 94. The detailed operation of the power conversion device 9 for the power distribution system battery will be explained with reference to the flowchart shown in Figure 49.

[0470] In S301, the fifth control circuit 949 initializes various parameters within the second control circuit 94.

[0471] In S302, the fifth control circuit 949 sets the power command value to "zero" and the voltage command value to "1500V".

[0472] In S303, the fifth control circuit 949 collects information from various voltage sensors and current sensors.

[0473] In S304, the fifth control circuit 949 controls the first DC / DC conversion circuit 93.

[0474] Figure 50 is a flowchart showing the control procedure of the first DC / DC conversion circuit 93 in S304 of Figure 49.

[0475] 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 power distribution system 21.

[0476] In S3042, the second power calculation circuit 941 calculates the charging and discharging power of the DC power distribution system 21.

[0477] In S3043, the second power calculation circuit 941 checks whether or not to operate the power converter 9 for the power distribution system battery in voltage control mode. In Embodiment 1, the control mode of the power converter 9 for the power distribution system battery is notified by the CEMS 3. If the power converter 9 for the power distribution system battery is to be operated in voltage control mode (YES), the process proceeds to S3044. If the power converter 9 for the power distribution system battery is to be operated in power control mode (NO), the process proceeds to S3046.

[0478] In S3044, the second power calculation circuit 941 generates a DC voltage target value based on the drooping characteristic. The operation of the voltage target generation circuit 942 has been explained in Figures 19 to 21, so further explanation is omitted.

[0479] The voltage target value based on the drooping characteristic generated by the voltage target generation circuit 942 is input to the voltage target value control circuit 945 and the fifth control circuit 949.

[0480] In step S3045, the voltage target value control circuit 945 generates a command value to control the first DC / DC conversion circuit 93 when a voltage target value is input. Figure 25 shows the configuration of the voltage target value control circuit 945.

[0481] The subtractor 9451 subtracts the voltage measured by the voltmeter 96 from the voltage target value input from the voltage target generation circuit 942, and outputs the subtraction result to the third PI control circuit 9452. The third PI control circuit 9452 applies PI control to the output of the subtractor 9451 so that the output of the subtractor 9451 becomes zero. The output of the third PI control circuit 9452 is input to the second switching circuit 947 as a control command value for the first DC / DC conversion circuit 93. Based on the control signal output from the fifth control circuit 949, the second switching circuit 947 selects the outputs of the voltage target value control circuit 945 and the power target value control circuit 946 and outputs them to the current limiting circuit 948. Therefore, when the voltage control mode ends, the second switching circuit 947 selects the output of the voltage target value control circuit 945 and outputs it to the current limiting circuit 948.

[0482] In S3048, the current limiting circuit 948 limits the command value output to the first DC / DC conversion circuit 93 if the current exceeds a predetermined current value based on the measurement result of the ammeter 97. As described above, the limited command value is subjected to PWM modulation, and a control signal is output to the first DC / DC conversion circuit 93.

[0483] In S3046, the fifth control circuit 949 instructs the power target generation circuit 943 to generate a DC power target value based on the droop characteristic. Since the operation of the power target generation circuit 943 has been described with reference to FIGS. 22 to 24, further description is omitted. When the generation of the DC power target value based on the droop characteristic is completed, the power target generation circuit 943 outputs the generated DC power target value to the power target value control circuit 946 and the fifth control circuit 949.

[0484] In S3047, the fifth control circuit 949 generates a current command value for the first DC / DC conversion circuit 93. Specifically, the power target value control circuit 946 in FIG. 9 generates the command value. FIG. 26 is a diagram showing the configuration of the power target value control circuit 946.

[0485] A subtractor 9461 subtracts the actually measured power calculated by the second power calculation circuit 941 from the power target value input from the power target generation circuit 943. The subtraction result is input to a fourth PI control circuit 9462. The fourth PI control circuit 9462 performs PI control on the output of the subtractor 9461 so that the output of the subtractor 9461 becomes zero. The output of the fourth PI control circuit 9462 is input to a second switching circuit 947 as a control command value for the first DC / DC conversion circuit 93.

[0486] Returning to FIG. 9, the description will be continued. As described above, the second switching circuit 947 switches between the output of the 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.

[0487] The fifth control circuit 949 outputs a control signal to select the output of the 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 the power converter 9 for the power distribution system battery in power control mode.

[0488] Returning to Figure 50, let's continue the explanation. When S3047 is completed (power control mode), the second switching circuit 947 selects the output of the power target value control circuit 946 and outputs it to the current limiting circuit 948.

[0489] In S3048, the current limiting circuit 948 limits the command value of the first DC / DC converter 93 that it receives. Specifically, if the output current exceeds a predetermined value, the current limiting circuit 948 limits the command value output to the first DC / DC converter 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 converter 93.

[0490] Returning to Figure 49, let's continue the explanation. In S305, the fifth control circuit 949 checks whether or not 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; if it has not received a transmission request from CEMS3 (NO), the process proceeds to S307.

[0491] In S306, the fifth control circuit 949 outputs the measurement information stored in a memory (not shown) to the second communication interface circuit 95. The second communication interface circuit 95 converts the measurement data from the fifth control circuit 949 into a predetermined format and sends it to the CEMS 3 via the communication line 22. The process then proceeds to S307.

[0492] In S307, the fifth control circuit 949 checks whether it has received control information (voltage command value, power command value, and information regarding drooping characteristics, etc.) from the CEMS3. If it has not received the information (NO), the process returns to S303 and continues. If it has received the information (YES), the process proceeds to S308.

[0493] 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). Then, the process returns to S303 and continues.

[0494] Next, the operation of the consumer PV power converter 13 will be explained with reference to 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. Two types of control are implemented in the consumer PV power converter 13: MPPT control, which extracts the maximum amount of power generated by the PV panel 12, and voltage control, which controls the output voltage of the PV panel 12 to control the amount of power generated.

[0495] Figure 7 is a block diagram of the power converter 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 second DC / DC converter circuit 133 converts the PV panel voltage output from the PV panel 12 into a DC distribution system voltage. The third control circuit 134 controls the second DC / DC converter circuit 133. The third communication interface circuit 135 communicates with CEMS 3, etc. 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.

[0496] Next, the operation of the consumer PV power converter 13 will be explained with reference to Figures 7 and 10. The second DC / DC conversion circuit 133 converts the DC power generated by the PV panel 12 into DC power for the DC distribution system 21 based on the command value output from the third control circuit 134, and outputs it to the DC distribution system 21.

[0497] The third control circuit 134 stores measurement data from voltmeters 131 and 136, measurement data from ammeters 132 and 137, and information such as the control method of the PV panel 12 in a memory not shown in the diagram. Based on a measurement data output request from the CEMS 3, the third control circuit 134 transmits the measurement data to the communication line 22 via the third communication interface circuit 135.

[0498] Next, the operation of the third control circuit 134 will be explained with reference to Figure 10. Figure 10 is a block diagram 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. The third control circuit 134 comprises an MPPT (Maximum Power Point Tracking) control circuit 1341, a PV voltage control circuit 1342, a third switching circuit 1343, and a sixth control circuit 1344.

[0499] 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 by the PV panel 12. 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.

[0500] The PV voltage control circuit 1342 generates control command values ​​for the second DC / DC conversion circuit 133 in order to maintain the DC voltage of the DC power distribution system 21 at a predetermined target voltage, based on the measurement value of the voltmeter 136.

[0501] The sixth control circuit 1344 outputs control parameters and 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 outputs a control signal for the third switching circuit 1343.

[0502] The third 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, in accordance with the control signal from the sixth control circuit 1344.

[0503] The second DC / DC conversion circuit 133 is controlled in MPPT mode or voltage control mode.

[0504] The third switching circuit 1343 is controlled to output the control command value generated by the MPPT control circuit 1341 in MPPT mode, and to output the control command value generated by the PV voltage control circuit 1342 in voltage control mode.

[0505] 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. In Embodiment 1, if the sixth control circuit 1344 receives a control mode from the CEMS 3, or if it is able to suppress the rise in the voltage at the grid connection point (receiving point) of the DC distribution system 21 to a predetermined voltage using voltage control and maintain it for a predetermined time, it 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.

[0506] Finally, the concept of the control mode of the power converter 9 for distribution system batteries will be explained. In Embodiment 1, since the AC / DC converter 6 provides inertial force to both the AC distribution system and the DC distribution system, it is not possible to manage the voltage of the DC distribution system 21. Therefore, when configuring the DC distribution system 21, at least one power converter 9 for distribution system batteries that operates in voltage control mode is required to manage the system voltage of the DC distribution system 21. Therefore, when selecting a converter that operates 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 that operates in voltage control mode will be the first to supply excess or insufficient power, and to secure a converter capacity that can cover the magnitude of the expected load fluctuations or power generation fluctuations.

[0507] In order to ensure the inertial force that the AC / DC converter 6 exerts on the AC power distribution system 20, it is desirable to keep fluctuations in the interconnection point voltage of the AC / DC converter 6 to the DC power distribution system 21 as low as possible. Therefore, in Embodiment 1, the power converter 9a for the power distribution system battery, which is closest to the AC / DC converter 6, was operated in voltage control mode. For the other power converters for the power distribution system battery 9b to n, two control modes are selected as follows. Since the power converters for the power distribution system battery operating in voltage control mode begin supplying excess or insufficient power, it is necessary to select the power converters for the power distribution system battery operating in voltage control mode (number of power converters for the power distribution system battery 9) so that the total converter capacity of the power converters for the power distribution system battery operating in voltage control mode is sufficient to cover the expected load fluctuations or power generation fluctuations. When selecting the power converters for the power distribution system battery 9, it is desirable to prioritize selecting those with a large battery capacity for the power distribution system battery 8. It should be noted that the transient response during load fluctuations or power generation fluctuations differs mainly between voltage control mode and power control mode, and it is also necessary to select the control mode by estimating the converged value in the steady state.

[0508] Once the selection of the power converter 9 for distribution system batteries that operates in voltage control mode is completed as described above, the operating modes of the remaining converters are then determined. Converters connected to power sources whose output power cannot be controlled (for example, PV and wind power generators) are not given a drooping characteristic. Therefore, Embodiment 1 focuses on the power converter 9 for distribution system batteries. For the other converters (power converter 9 for distribution system batteries), if the converter capacity of the power converter 9 operating in voltage mode can cover the expected demand fluctuations, they may all be controlled in voltage control mode or all in power control mode.

[0509] The following explains the considerations for selecting the voltage control mode and the power control mode. As mentioned above, a converter in voltage control mode manages the voltage at the grid connection point itself, and in the event of demand fluctuations, it supplies excess or insufficient power and manages the voltage to which it is connected to the DC distribution system 21. If a demand fluctuation exceeds the converter capacity, a converter in voltage control mode may shut down due to overcurrent or other issues.

[0510] As shown in Figure 30, the output power of the converter in power control mode is limited by Pmax on the upper limit and Pmin (converter capacity) on the lower limit. Even if the voltage of the DC distribution system 21 deviates from the range of Vmax or Vmin, the converter in power control mode will continue to operate. However, the converter in power control mode cannot supply instantaneous surplus or deficit power when a sharp load fluctuation or power generation fluctuation occurs.

[0511] Therefore, in Embodiment 1, if the converter capacity of the corresponding power converter 9 for distribution system batteries is sufficiently large for the load fluctuation amount of the consumer load 11 within the consumer load group 10 and the power generation amount fluctuation amount of the PV panel 12, the voltage control mode is selected; otherwise, the power control mode is selected. The selection between the voltage control mode and the power control mode is not limited to the above. For example, when the CEMS 3 creates an operation plan, it estimates the voltage fluctuation range at the grid connection point of each power converter 9 for distribution system batteries when a load fluctuation or power generation fluctuation occurs, 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), the power control mode is selected; otherwise, the voltage control mode is selected.

[0512] The power converter of Embodiment 1 is configured as described above, and by providing the AC / DC converter 6 with AC-side drooping characteristics and DC-side drooping characteristics, it can supply inertial force to both the AC distribution system and the DC distribution system. When creating an operation plan (power command value (Pref) and voltage command value (Vref)) for the AC / DC converter 6 and the power converter 9 for the distribution system battery, the power converter of Embodiment 1 estimates the power flow current based on the predicted power consumption of the consumer load 11 in the consumer 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 power converter of Embodiment 1 estimates the grid connection point voltage of the DC distribution system 21 for the power converter 9 and generates a power command value so that the grid connection point voltage falls within a predetermined range. This allows the interconnection point voltage of each power converter 9 for distribution system batteries to the DC system to be controlled to stay within a predetermined voltage range, and also enables smooth power flow control even when load fluctuations occur. The power converter of Embodiment 1 estimates the fluctuation range of the interconnection point voltage 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 supply and demand power 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 the SOC of the distribution system batteries 8 to be approximately the same.

[0513] In Embodiment 1, the case where the system is connected to the AC distribution system 20b via the AC / DC converter 6 was described. However, 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 DC distribution system 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. 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).

[0514] 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 the droop characteristic supply excess or deficit power autonomously and cooperatively without communication, thereby maintaining the voltage of the DC distribution system 21 within an appropriate range. By appropriately allocating 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 deficit 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.

[0515] As shown in Figure 1, in a power distribution system consisting of multiple feeder DC microgrids 100 connected via a switch 5 below a substation 1, if at least one AC / DC converter 6 is operated in GFM control mode, even if the main power grid experiences a power outage due to an accident, the AC / DC converter 6 operating in GFM control mode can support the AC side system voltage of the AC / DC converters 6 operating in modes other than GFM control mode. As a result, if a power outage in the main power grid is detected and the switch 5 is opened to disconnect from the main power grid, all of the multiple feeder DC microgrids 100 can work together to transition to independent operation without a power outage. When the main power grid is restored, if the voltage phase of the AC distribution system voltages at both ends of the switch 5 is within a predetermined range (for example, ±5 degrees), it can be connected to the restored main power grid without a power outage.

[0516] Embodiment 2. In Embodiment 1, when controlling the AC / DC converter 6, the system quality of the DC power distribution system 21 is prioritized by providing a dead-band drooping characteristic during GFL control, and the system quality of the AC power distribution system 20 is prioritized by providing a dead-band in the DC side drooping characteristic during GFM control.

[0517] In Embodiment 2, when controlling the AC / DC conver...

Claims

1. A power conversion device comprising: an AC / DC conversion circuit that converts AC power from an AC system to DC power from a DC system, or DC power from a DC system to AC power from an AC system; a voltmeter that measures the DC voltage of the DC system; and a control circuit that detects the frequency of the AC system, calculates the power exchanged between the AC system and the DC system, calculates the excess or deficit power of the DC system based on a first drooping characteristic representing the DC side characteristics using the measured DC voltage, and calculates the inertial force required by the AC system based on a second drooping characteristic representing the AC side characteristics using the detected frequency or the calculated power, thereby correcting the input frequency command value or power command value, and controlling the AC / DC conversion circuit based on the corrected frequency command value or the corrected power command value.

2. The power converter according to claim 1, further comprising a communication interface circuit for communicating with a management device, wherein the control circuit receives the frequency command value and the power command value from the management device via the communication interface circuit.

3. The first drooping characteristic represents a relationship in which the difference between the DC voltage of the DC system measured by the voltmeter and the DC voltage command value of the DC system is taken as input, and a first differential power representing the excess or deficit power is output. The second drooping characteristic represents a relationship in which the difference between the detected frequency of the AC system and the frequency command value of the AC system is taken as input, and a second differential power representing the inertial force is output. The control circuit comprises: a first drooping characteristic circuit that calculates the first differential power from the difference between the DC voltage of the DC system measured by the voltmeter and the DC voltage command value of the DC system according to the first drooping characteristic; and a second drooping characteristic circuit that calculates the second differential power from the difference between the detected frequency of the AC system and the frequency command value of the AC system according to the second drooping characteristic. A power conversion device according to claim 1 or 2, comprising: a current control circuit that controls the AC / DC conversion circuit as a current source based on a corrected power command value which is the sum of the power command value and the first differential power and the second differential power.

4. The power conversion device according to claim 3, wherein the first drooping characteristic has no dead zone, and the second drooping characteristic has a dead zone.

5. The power conversion device according to claim 3, wherein the first drooping characteristic has a dead zone, and the second drooping characteristic does not have a dead zone.

6. The power conversion device according to claim 3, wherein the first drooping characteristic has no dead zone, and the second drooping characteristic has no dead zone.

7. The first drooping characteristic represents a relationship in which the difference between the DC voltage of the DC system measured by the voltmeter and the DC voltage command value of the DC system is taken as input, and a first differential power representing the excess or deficit power is output; the second drooping characteristic represents a relationship in which the value obtained by subtracting the calculated power from the sum of the first differential power and the power command value is taken as input, and the difference between the frequency of the AC system representing the inertial force and the frequency command value of the AC system is output; the control circuit includes a first drooping characteristic circuit that calculates the first differential power from the difference between the DC voltage of the DC system measured by the voltmeter and the DC voltage command value of the DC system according to the first drooping characteristic; A power conversion device according to claim 1 or 2, comprising: a second drooping characteristic circuit that calculates a difference between the frequency of the AC system and the frequency command value of the AC system from a value obtained by subtracting the calculated power from the sum of the first differential power and the power command value according to the second drooping characteristic; and a voltage control circuit that controls the AC / DC conversion circuit as a voltage source based on a corrected frequency command value which is the sum of the frequency command value and the difference value between the frequency command value.

8. The power conversion device according to claim 7, wherein the first drooping characteristic has a dead zone, and the second drooping characteristic does not have a dead zone.

9. The power conversion device according to claim 7, wherein the first drooping characteristic has no dead zone, and the second drooping characteristic has no dead zone.

10. The power conversion device according to claim 3 or 7, wherein the second drooping characteristic has lower sensitivity in a predetermined range including the origin than outside the predetermined range.

11. The power conversion device according to claim 3 or 7, wherein the second drooping characteristic is asymmetric with respect to the origin.

12. The power conversion device according to claim 3 or 7, wherein the second drooping characteristic is represented by a monotonically decreasing straight line.

13. The power conversion device according to claim 3 or 7, wherein the second drooping characteristic is represented by a monotonically decreasing curve.

14. The power conversion device according to claim 3 or 7, wherein the first drooping characteristic has lower sensitivity in a predetermined range including the origin than outside the predetermined range.

15. The power conversion device according to claim 3 or 7, wherein the first drooping characteristic is asymmetric with respect to the origin.

16. The power conversion device according to claim 3 or 7, wherein the first drooping characteristic is represented by a monotonically decreasing straight line.

17. The power conversion device according to claim 3 or 7, wherein the first drooping characteristic is represented by a monotonically decreasing curve.

18. The power conversion device according to any one of claims 3 to 17, wherein the first drooping characteristic circuit outputs a first-order lag signal of the first differential power to the second drooping characteristic circuit.

19. The power conversion device according to any one of claims 3 to 18, wherein the second drooping characteristic circuit outputs a first-order lag signal of the difference value.

20. The power conversion device according to any one of claims 3 to 19, further comprising a switch that sets the output of the first drooping characteristic circuit to zero when the detected frequency of the AC system is less than a predetermined frequency.

21. A power converter management device for managing at least one first power converter that manages the voltage of a DC system and a second power converter that implements an AC / DC conversion circuit having a drooping characteristic that applies inertial force to the DC system and the AC system, comprising: a first drooping characteristic generation circuit that generates a first drooping characteristic to be applied to the DC system side; a second drooping characteristic generation circuit that generates a second drooping characteristic to be applied to the AC system side; and an operation plan creation circuit that generates an operation plan to be applied to the first power converter and the second power converter, wherein the second drooping characteristic generation circuit generates the second drooping characteristic based on the control mode and inertial force of the drooping characteristic applied to the AC system side, and the first drooping characteristic generation circuit generates the first drooping characteristics of the first power converter and the second power converter based on the operation plan output from the operation plan creation circuit.

22. The power converter management device according to claim 21, wherein the control mode for the drooping characteristic applied to the AC system is a GFL (Grid-Following) control mode or a GFM (Grid-Forming) control mode.

23. The power converter management device according to claim 22, wherein the second drooping characteristic generation circuit provides a dead zone in the second drooping characteristic when the second power converter is operated in the GFL control mode.

24. The power converter management device according to claim 22, wherein the first drooping characteristic generation circuit provides a dead zone in the first drooping characteristic of the second power converter when the second power converter is operated in the GFM control mode.

25. The power converter management device according to any one of claims 21 to 24, wherein the power converter management device has a communication circuit that communicates with a higher-level management device, the communication circuit receives the details of a contract in the supply and demand adjustment market, and the second drooping characteristic generation circuit generates the second drooping characteristic based on the results of the reception.

26. The power converter management device according to any one of claims 21 to 25, wherein the control mode on the DC system side of the second power converter is a power control mode.

27. The power converter management device according to any one of claims 21 to 26, wherein the operation plan creation circuit generates at least a power command value for the first power converter based on a supply and demand plan notified from the power distribution automation system, the power consumption of each consumer connected to the DC system, and the predicted power generation results of energy creation equipment owned by each consumer.

28. The power converter management device according to any one of claims 21 to 27, wherein the first drooping characteristic generation circuit generates the first drooping characteristic of the second power converter such that, when the supply and demand plan notified from the power distribution automation system includes an upper limit and a lower limit for supply and demand, the upper limit and lower limit are the lower limit and upper limit for the DC voltage at the interconnection point between the DC system and the second power converter, respectively.

29. The power converter management device according to any one of claims 21 to 28, wherein the operation plan creation circuit estimates the distribution line impedance of the DC system and predicts the voltage at the connection point between the second power converter and the first power converter and the DC system based on the estimation result of the distribution line impedance.

30. The power converter management device according to claim 29, wherein the operation plan creation circuit predicts the power flow current of the DC system based on the power consumption of each consumer connected to the DC system and the predicted power generation results of the energy generation equipment owned by each consumer, predicts the voltage at the connection point between the second power converter and the first power converter and the DC system based on the predicted power flow current and the estimated distribution line impedance, and generates a DC voltage command value based on the predicted result.

31. The power converter management device according to claim 30, wherein the operation plan creation circuit predicts the upper and lower limits of the power demand when predicting the power consumption of each consumer connected to the DC system and the power generation of energy creation equipment owned by each consumer, and the first drooping characteristic generation circuit generates the first drooping characteristics of the first power converter and the second power converter so that the predicted upper and lower limits of the power demand fall within the upper and lower voltage range of the DC system voltage.

32. The power converter management device according to claim 31, wherein the operation plan creation circuit predicts the fluctuation range of the power current of the DC system based on the predicted upper and lower limits of the power demand, predicts the voltage fluctuation at the connection point of the second power converter and the first power converter with the DC system based on the predicted fluctuation range of the power current, and generates the first drooping characteristics of the first power converter and the second power converter so that the voltage fluctuation of the DC system falls within the upper and lower voltage limits of the DC system voltage.

33. The power converter management device according to claim 23, wherein the operation plan creation circuit predicts the frequency fluctuation range of the AC system, and when operating the second power converter in the GFL control mode and when introducing a dead zone to the second droop characteristic generated by the second droop characteristic generation circuit, the frequency range in which the dead zone is introduced is determined based on the prediction result of the frequency fluctuation range of the AC system.

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