Power conversion device

Abstract

A power conversion device equipped with a virtual synchronous generator control includes a converter that converts a first direct-current voltage output from a distributed power source into a second direct-current voltage, an inverter that converts the second direct-current voltage output from the converter into an alternating-current voltage and outputs to an alternating-current system, a converter control circuit, a virtual synchronous generator control circuit that causes the inverter to have transient characteristics of a synchronous generator, and an inverter control circuit that controls the inverter as a voltage source based on alternating-current system voltage information input from the virtual synchronous generator control circuit. The virtual synchronous generator control circuit calculates a switching frequency at which charging and discharging of the distributed power source is switched, based on information required for virtual synchronous generator control including a power target value of the power conversion device. The converter control circuit creates a frequency range of the alternating-current system voltage for imparting a dead zone that makes the charging and discharging power of the distributed power source zero or imparting hysteresis to the switching of the charging and discharging of the distributed power source in a droop characteristic of the power conversion device using the switching frequency. The converter control circuit controls in a manner that makes the charging and discharging power of the distributed power source zero in the frequency range.

Description

Technical Field

[0001] This disclosure relates to power conversion devices. Background Technology

[0002] In recent years, to reduce environmental impact, the introduction of energy creation equipment utilizing renewable energy sources, such as solar cells (hereinafter referred to as "energy creation equipment"), has been accelerated. Furthermore, to address power shortages following the Great East Japan Earthquake, the commercialization of systems equipped with energy storage devices such as batteries (hereinafter referred to as "energy storage equipment"), or systems combining energy creation and storage equipment, is underway. In these systems, static inverters are used to interconnect the energy creation and storage equipment with the AC system.

[0003] On the other hand, in the power system, thermal power plants, which act as regulators of power generation in response to demand fluctuations, are projected to be shut down in the future, from the perspective of reducing generation costs, including management costs, as renewable energy generation increases. However, synchronous generators in thermal power plants potentially play a role in suppressing system frequency fluctuations (inertial forces, synchronization forces, etc.). Therefore, if the shutdown of thermal power plants proceeds, the increased number of synchronous generators may make it difficult to ensure the stability of the power system.

[0004] To address the aforementioned technical challenges, control technology for virtual synchronous generators that enable static inverters to function as synchronous generators is being developed. For example, Japanese Patent Application Publication No. 2019-176584 (Patent Document 1) discloses a method for setting control parameters of a distributed power source (static inverter) equipped with virtual synchronous generator control. Specifically, Patent Document 1 discloses a method for generating control parameters for setting the virtual inertia in the distributed power source based on either a required inertia value requested by the system user or a virtual inertia value calculated based on the specifications and operating state of the distributed power source.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-176584 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] According to the method for generating control parameters described in Patent Document 1, the system inertia force desired by the system administrator is guaranteed. However, in self-sufficient microgrids and similar systems, in structures where multiple batteries, each equipped with a static inverter controlled by a virtual synchronous generator, operate as the main power source, the power consumed by the load and the power generated by the energy-generating equipment may sometimes reach equilibrium due to load fluctuations or fluctuations in the power generated by the energy-generating equipment. In such cases, it is desirable for the charging and discharging power of each battery to be zero.

[0010] However, due to measurement errors in the voltmeters and ammeters installed on each battery, the charging and discharging power of each battery may not be controlled to zero. In this case, unnecessary charging and discharging may occur, such as using the discharging power of the first battery to charge the second battery. Such unnecessary charging and discharging or repeated charging and discharging has the following problems: it causes power loss due to charging and discharging and causes unnecessary damage to the batteries. In Patent Document 1, the control parameters are generated only based on the system inertia force required by the system operator, and the above-mentioned problems are not considered.

[0011] This disclosure is made to solve problems as described above, and its purpose is to suppress unnecessary charging and discharging between multiple distributed power sources in an AC system having a static inverter equipped with virtual synchronous generator control, when the power consumption of the load and the power generation of the energy-generating equipment are balanced.

[0012] Technical solutions for solving technical problems

[0013] According to one aspect of this disclosure, a power conversion device is connected to an AC system and equipped with virtual synchronous generator control. The power conversion device includes: a converter that converts a first DC voltage output from a distributed power source to a second DC voltage; an inverter that converts the second DC voltage output from the converter to an AC voltage and outputs it to the AC system; a communication circuit that receives information required for virtual synchronous generator control from a management device managing the distributed power source; a first voltmeter that measures the second DC voltage; a second voltmeter that measures the AC system voltage of the AC system; a converter control circuit that controls the converter; a virtual synchronous generator control circuit that enables the inverter to have the transient characteristics of a synchronous generator; and an inverter control circuit that controls the inverter as a voltage source based on the AC system voltage information input from the virtual synchronous generator control circuit. The information required for virtual synchronous generator control includes a power target value for the power conversion device. Based on the information required for virtual synchronous generator control, the virtual synchronous generator control circuit calculates the switching frequency at which the charging and discharging of the distributed power source is switched. The converter control circuit uses a switching frequency to create a frequency range for the AC system voltage. This frequency range is used to introduce a dead zone in the drooping characteristics of the power conversion device that reduces the charging and discharging power of the distributed generation to zero, or to introduce hysteresis to the switching of charging and discharging of the distributed generation. The converter control circuit controls the distributed generation to have zero charging and discharging power within this frequency range.

[0014] Invention Effects

[0015] According to this disclosure, in a power system with multiple distributed power sources interconnected by a static inverter equipped with virtual synchronous generator control, unnecessary charging and discharging between the multiple distributed power sources can be suppressed when the power consumed by the load and the power generated by the energy-generating equipment are balanced. Attached Figure Description

[0016] Figure 1 A block diagram illustrating an example of the structure of a power distribution system.

[0017] Figure 2 For further explanation Figure 1 The diagram shows the structure of the power distribution system.

[0018] Figure 3 To show Figure 1 The diagram shows the structure of CEMS.

[0019] Figure 4 To show Figure 3 The diagram shown is a block diagram of the circuit structure created by the operational plan.

[0020] Figure 5 To show Figure 3 The diagram shows the block diagram of the control parameter generation circuit.

[0021] Figure 6 To show Figure 1 The diagram shows a block diagram of the structure of a power conversion device for a large-scale solar power plant.

[0022] Figure 7 To explain Figure 1 The diagram shown is a block diagram of the structure of a power conversion device for storage batteries.

[0023] Figure 8 To explain Figure 6 The block diagram of the structure of the first control circuit is shown.

[0024] Figure 9 To explain Figure 6 The block diagram of the structure of the second control circuit is shown.

[0025] Figure 10 To explain Figure 7 The block diagram of the structure of the third control circuit is shown.

[0026] Figure 11 To explain Figure 7 The block diagram of the structure of the fourth control circuit is shown.

[0027] Figure 12 To explain Figure 11 The diagram shows the structure of the AC frequency detection circuit.

[0028] Figure 13 To explain Figure 11 The diagram shows the structure of the inverter voltage control circuit.

[0029] Figure 14 To explain Figure 11 The diagram shows the structure of the virtual synchronous generator control circuit.

[0030] Figure 15 To explain Figure 14 The diagram shows the structure of the governor control circuit.

[0031] Figure 16 To explain Figure 14 The diagram shows the block diagram of the operational circuit structure of the particle system.

[0032] Figure 17 A diagram illustrating the area covered by the virtual synchronous generator control system equipped with a power conversion device.

[0033] Figure 18 This diagram illustrates the control of a virtual synchronous generator equipped with a power conversion device in Embodiment 1.

[0034] Figure 19 This diagram illustrates the control of a virtual synchronous generator equipped with a power conversion device in Embodiment 1.

[0035] Figure 20 A diagram illustrating an example of the ΔP / ΔF characteristics.

[0036] Figure 21 This is a diagram showing the frequency response waveform of the AC voltage output from the static inverter when the load changes abruptly in the virtual synchronous generator control of the power conversion device equipped in Embodiment 1.

[0037] Figure 22 This is a diagram showing the response waveform of the effective value of the AC power output from two power conversion devices equipped with conventional virtual synchronous generator control.

[0038] Figure 23 A diagram illustrating the response waveform of the effective value of the AC power output from two power conversion devices equipped with virtual synchronous generator control in Embodiment 1.

[0039] Figure 24A The figure shows a first example of the ΔP / ΔF characteristics of the power conversion device 41 equipped with virtual synchronous generator control in Embodiment 1.

[0040] Figure 24B The figure shows a second example of the ΔP / ΔF characteristics of the power conversion device 41 equipped with virtual synchronous generator control in Embodiment 1.

[0041] Figure 24C The figure shows a third example of the ΔP / ΔF characteristics of the power conversion device 41 equipped with virtual synchronous generator control in Embodiment 1.

[0042] Figure 25 For the purpose of illustration Figure 1 The diagram shown illustrates the normal operation of a distributed power system centered on CEMS.

[0043] Figure 26 To show Figure 1 The flowchart shown is for the control process of CEMS.

[0044] Figure 27 To illustrate the process of creating an operating plan for the battery ( Figure 26 The flowchart of S05).

[0045] Figure 28 This illustrates the processing of information required to generate the control parameters for virtual synchronous generator control. Figure 27 The flowchart of S056).

[0046] Figure 29To illustrate the process for generating the baseline ΔP / ΔF characteristics ( Figure 28 The flowchart of S0562).

[0047] Figure 30 To illustrate the process for generating the ΔP / ΔF characteristics ( Figure 28 The flowchart of S0563).

[0048] Figure 31 To illustrate the process of generating the dead zone width ( Figure 28 The flowchart of S0564).

[0049] Figure 32 To illustrate the process of modifying the battery's operating plan ( Figure 26 The flowchart of S09).

[0050] Figure 33 This is a flowchart used to illustrate the operation of a power conversion device.

[0051] Figure 34 This is a flowchart illustrating the control processing details of the second DC / DC converter.

[0052] Figure 35 This is a flowchart illustrating the control processing details of the second DC / AC converter.

[0053] Figure 36 To illustrate the process of generating control parameters ( Figure 33 The flowchart of S216).

[0054] Figure 37 To illustrate the process of calculating the dead-time frequency ( Figure 36 The flowchart of S2170).

[0055] Figure 38A The figure shows a first example of the ΔP / ΔF characteristics imparted to the power conversion device of Embodiment 2.

[0056] Figure 38B The figure shows a second example of the ΔP / ΔF characteristics imparted to the power conversion device of Embodiment 2.

[0057] Figure 38C The figure shows a third example of the ΔP / ΔF characteristics imparted to the power conversion device of Embodiment 2.

[0058] Figure 39 This is a flowchart illustrating the control processing details of the second DC / DC converter.

[0059] Figure 40 This is a flowchart illustrating the control processing details of the second DC / AC converter.

[0060] Figure 41 This is a flowchart illustrating the details of the detection and processing during the hysteresis period.

[0061] Figure 42 This diagram illustrates the concept of virtual synchronous generator control technology. Detailed Implementation

[0062] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. Furthermore, the same or equivalent parts in the drawings will be referred to by the same reference numerals, and their descriptions will generally not be repeated.

[0063] Implementation method 1.

[0064] (Example of a power distribution system structure)

[0065] First, a structural example of the power distribution system connected to the power conversion device in Embodiment 1 will be described. Furthermore, although a three-phase system is illustrated in Embodiment 1, the power distribution system can be a single-phase system.

[0066] Figure 1 A block diagram illustrating an example of the structure of the power distribution system 24. (For example...) Figure 1 As shown, the power distribution system 24 receives power from the substation 20. The power distribution system 24 is equipped with multiple automatic voltage regulators (SVRs: Step Voltage Regulators) 23a to 23c. The multiple SVRs 23a to 23c are connected in series with respect to the power flow. Connected to the multiple SVRs 23a to 23c are buildings 112, apartments 113, towns A 100a to D 100d, factories 110, power conversion devices 27 for large solar power plants, power conversion devices 41a to 41c for system batteries, and synchronous generators 30a and 30b. In the following description, SVRs 23a to 23c will be collectively referred to as "SVR 23". Additionally, power conversion devices 41a to 41c will be collectively referred to as "power conversion devices 41".

[0067] The power distribution system 24 is equipped with multiple voltmeters 22a, 22e, 22f, 22i, 22j, and 22x. Voltmeters 22a, 22e, 22f, 22i, 22j, and 22x are collectively referred to as "voltmeter 22" below. The measured values ​​of each voltmeter 22 are sent to the power distribution automation system 21 (hereinafter also referred to as "DSO 21") at predetermined intervals. DSO 21 corresponds to one embodiment of a "system management device" that manages the power distribution system 24.

[0068] The tap position information, primary side voltage, and secondary side voltage information of SVR 23 are sent to DSO 21. In Embodiment 1, SVR 23 notifies the tap position information, primary side voltage, and secondary side voltage information at predetermined intervals, and notifies the tap position information, primary side voltage, and secondary side voltage information intermittently during tap switching.

[0069] The CEMS (Community Energy Management System) 31 collects various measurement values ​​and other information from each user (township 100a-100d, factory 110, building 112, apartment 113), power conversion device 27, synchronous generators 30a and 30b, and power conversion devices 41a-41c at predetermined intervals. In response to a request from DSO 21, the CEMS 31 notifies DSO 21 of the collected data. Additionally, the electricity consumption of users within townships 100a-100d and the electricity generated by energy-generating equipment are measured by smart meters (not shown) installed at each user's location. The CEMS 31 collects the smart meter measurements at predetermined intervals (e.g., 30-minute intervals). The CEMS 31 corresponds to one embodiment of a "management device".

[0070] A large solar power plant 26 is connected to the power conversion device 27. System batteries 40a to 40c are connected to the power conversion devices 41a to 41c respectively. Batteries 40a to 40c are large-capacity batteries that can be connected to the power distribution system 24. In the following description, batteries 40a to 40c are also referred to as "battery 40".

[0071] Figure 2 For further explanation Figure 1 The diagram shows the structure of the power distribution system 24. Figure 2 As shown, the power distribution system 24 is connected to a load 600, a power conversion device 41, and a battery 40. Furthermore, for the sake of simplicity, in... Figure 2 In this paper, the impedance 29 of the power distribution system 24 is represented as a lumped system. It is assumed that the impedance 29 of the power distribution system 24 consists of a reactance component and a resistance component.

[0072] (1) CEMS 31

[0073] Figure 3 To show Figure 1 The diagram shows the structure of CEMS 31.

[0074] like Figure 3 As shown, CEMS 31 includes a communication circuit 11, a storage circuit 12, a control parameter generation circuit 13, an operation plan creation circuit 14, a data transmission generation circuit 15, and a control circuit 16.

[0075] The communication circuit 11 communicates with DSO 21, various users (towns 100a-100d, factories 110, buildings 112, apartments 113), power conversion device 27, synchronous generators 30a and 30b, and power conversion devices 41a-41c via communication line 25.

[0076] The storage circuit 12 stores various information acquired via the communication circuit 11. This information includes measurement results and status information of each distributed power source.

[0077] The control parameter generation circuit 13 generates control parameters for the virtual synchronous generators equipped in each power conversion device 41a to 41c.

[0078] The operation plan creation circuit 14 creates operation plans for the power conversion devices 41a to 41c based on control commands from the DSO 21. The operation plans for the power conversion devices 41a to 41c include the corresponding charge / discharge plans (target power values) for the batteries 40a to 40c. In Embodiment 1, the operation plan creation circuit 14 creates 24-hour operation plans at 30-minute intervals.

[0079] Furthermore, the operation plan creation circuit 14 determines whether the operation plan needs to be revised based on the measurement results of the power conversion devices 41a to 41c collected in 5-minute increments and the SOC (State of Charge) information of the batteries 40a to 40c. When it is determined that the operation plan needs to be revised, the operation plan creation circuit 14 revises the operation plan for the period up to the next time it receives a control command from DSO 21.

[0080] The data generation circuit 15 stores the control parameters generated by the control parameter generation circuit 13 for controlling the virtual synchronous generator and the operation plan output from the operation plan creation circuit 14. In response to a transmission command from the control circuit 16, the data generation circuit 15 outputs the stored data to the communication circuit 11. The communication circuit 11, according to the control signal output from the control circuit 16, transmits the data output from the data generation circuit 15 to the communication line 25.

[0081] Control circuit 16 is a control circuit used to manage the distributed power sources connected to the power distribution system 24. Control circuit 16 manages the operation of communication circuit 11, storage circuit 12, control parameter generation circuit 13, operation plan creation circuit 14, and data transmission generation circuit 15.

[0082] (1-1) Operation plan creation circuit 14

[0083] Figure 4 To show Figure 3The diagram shown is a block diagram of the structure of the operation plan creation circuit 14.

[0084] like Figure 4 As shown, the operation plan creation circuit 14 includes a battery operation plan creation circuit 141, a power generation prediction circuit 142, a power consumption prediction circuit 143, a battery operation plan correction circuit 144, a first management circuit 145, and a second management circuit 146.

[0085] The battery operation plan creation circuit 141 creates operation plans (power target values) for power conversion devices 41a, 41b, and 41c based on information related to control commands notified from DSO 21, the power generation forecast results of the large solar power plant 26 predicted by the power generation forecast circuit 142, and the power consumption forecast results of users predicted by the power consumption forecast circuit 143. Furthermore, the control commands notified from DSO 21 to the battery operation plan creation circuit 141 include planned values ​​for the power consumed downstream of substation 20 (power supplied to distribution system 24). The planned power supply values ​​consist of planned values ​​for amounts every 30 minutes and 24 hours.

[0086] The power generation prediction circuit 142 obtains 24-hour weather forecast information via communication circuit 11 from a weather forecast server (not shown). Based on the obtained weather forecast information and information from a database (not shown) prepared for predicting power generation, the power generation prediction circuit 142 predicts the power generation of the large solar power plant 26.

[0087] The power consumption prediction circuit 143 predicts the total power consumption of each user based on the clock information (year, month, day, week, time) inside the CEMS 31 and information from a database (not shown) prepared for predicting power consumption.

[0088] The battery operation plan correction circuit 144, via the communication circuit 11, determines whether the operation plan needs to be corrected based on the charging and discharging capacity and power target value information of the power conversion devices 41a-41c. When it is determined that correction is needed, the battery operation plan correction circuit 144 generates a correction value for the operation plan.

[0089] The first management circuit 145 stores the power target values ​​(charging power target value and discharging power target value) of each battery 40 generated by the battery operation plan creation circuit 141 and the battery operation plan correction circuit 144. Based on the control signal output from the second management circuit 146, the first management circuit 145 outputs the power target values ​​to the control parameter generation circuit 13 and the data transmission generation circuit 15.

[0090] The second management circuit 146 manages the operation of the battery operation plan creation circuit 141, the power generation prediction circuit 142, the power consumption prediction circuit 143, the battery operation plan correction circuit 144, and the first management circuit 145.

[0091] (1-2) Control parameter generation circuit 13

[0092] Figure 5 To show Figure 3 The block diagram shown is of the structure of the control parameter generation circuit 13.

[0093] like Figure 5 As shown, the control parameter generation circuit 13 includes a reference ΔP / ΔF characteristic calculation circuit 131, a ΔP / ΔF characteristic calculation circuit 132, a third management circuit 135, and a control circuit 136.

[0094] The reference ΔP / ΔF characteristic calculation circuit 131 calculates the reference ΔP / ΔF characteristic based on the capacity information of the static inverters (second DC / AC converter 408) of the power conversion devices 41a to 41c.

[0095] The ΔP / ΔF characteristic calculation circuit 132 is based on the above-mentioned baseline ΔP / ΔF characteristics and the operation plan creation circuit 14. Figure 4 The power target value information created is used to calculate the ΔP / ΔF characteristic.

[0096] The third management circuit 135 manages the control parameters for the synchronous generator control. The third management circuit 135 saves information such as the ΔP / ΔF characteristic calculated by the ΔP / ΔF characteristic calculation circuit 132 and the power target value Pref to a memory (not shown) and manages it.

[0097] The control circuit 136 manages the operation of the reference ΔP / ΔF characteristic calculation circuit 131, the ΔP / ΔF characteristic calculation circuit 132, and the third management circuit 135.

[0098] (2) Power conversion device 27

[0099] Figure 6 To show Figure 1 A block diagram of the structure of the power conversion device 27 shown.

[0100] like Figure 6 As shown, the power conversion device 27 includes voltmeters 201, 206, and 210, ammeters 202, 207, and 211, a first DC / DC converter 203, a first control circuit 204, a DC bus 205, a first DC / AC converter 208, a second control circuit 209, and a communication interface (I / F) 212.

[0101] Voltmeter 201 measures the DC voltage output from the large solar power plant 26. Ammeter 202 measures the DC current output from the large solar power plant 26.

[0102] The first DC / DC converter 203 converts the first DC voltage output from the large solar power plant 26 into a second DC voltage. The first control circuit 204 controls the first DC / DC converter 203.

[0103] DC bus 205 supplies the second DC voltage output from the first DC / DC converter 203 to the first DC / AC converter 208. Voltmeter 206 measures the voltage of DC bus 205. Ammeter 207 measures the DC current output from the first DC / DC converter 203.

[0104] The first DC / AC converter 208 converts the DC power output from the first DC / DC converter 203 into AC power. The second control circuit 209 controls the first DC / AC converter 208.

[0105] Voltmeter 210 measures the AC voltage output from the first DC / AC converter 208. Ammeter 211 measures the AC current output from the first DC / AC converter 208. Communication I / F 212 enables communication between the power conversion unit 27 and CEMS 31.

[0106] (3) Power conversion device 41

[0107] Figure 7 To explain Figure 1 The diagram shows the structure of the power conversion device 41.

[0108] like Figure 7 As shown, the power conversion device 41 includes voltmeters 401, 406, and 410, ammeters 402, 407, and 411, a second DC / DC converter 403, a third control circuit 404, a DC bus 405, a second DC / AC converter 408, a fourth control circuit 409, and a communication I / F 412.

[0109] Voltmeter 401 measures the DC voltage output from battery 40. Ammeter 402 measures the DC current output from battery 40.

[0110] The second DC / DC converter 403 converts the third DC voltage output from the battery 40 into a fourth DC voltage. The third control circuit 404 controls the second DC / DC converter 403. The second DC / DC converter 403 corresponds to one embodiment of a "converter".

[0111] DC bus 405 supplies the DC voltage output from the second DC / DC converter 403 to the second DC / AC converter 408. Voltmeter 406 measures the voltage of DC bus 405. Voltmeter 406 corresponds to an embodiment of the "first voltmeter". Ammeter 407 measures the DC current output from the second DC / DC converter 403.

[0112] The second DC / AC converter 408 converts the DC power output from the second DC / DC converter 403 into AC power. The fourth control circuit 409 controls the second DC / AC converter 408. The second DC / AC converter 408 corresponds to one embodiment of an "inverter".

[0113] Voltmeter 410 measures the AC voltage output from the second DC / AC converter 408. Voltmeter 410 corresponds to one embodiment of the "second voltmeter". Ammeter 411 measures the AC current output from the second DC / AC converter 408. Communication I / F 412 enables communication between the power conversion device 41 and the CEMS 31.

[0114] Furthermore, as the first DC / DC converter 203 ( Figure 6 ) and the second DC / DC converter 403 ( Figure 7 ), and can use known DC / DC converters as appropriate. First DC / AC converter 208 ( Figure 6 ) and the second DC / AC converter 408 ( Figure 7 This corresponds to an embodiment of a "static inverter". Known inverters can be used as the first DC / AC converter 208 and the second DC / AC converter 408.

[0115] (2-1) First control circuit 204

[0116] Figure 8 To explain Figure 6 The block diagram of the structure of the first control circuit 204 shown is shown.

[0117] like Figure 8 As shown, the first control circuit 204 includes an MPPT (Maximum Power Point Tracking) control circuit 51, a voltage control circuit 52, a first switching circuit 53, and a fifth control circuit 54.

[0118] The MPPT control circuit 51 performs so-called Maximum Power Point Tracking (MPPT) control based on the measurements from voltmeter 201 and ammeter 202. The MPPT control circuit 51 searches for the maximum power point of the large solar power plant 26 to maximize the extraction of generated power. Specifically, the MPPT control circuit 51 generates control command values ​​for the first DC / DC converter 203 to control the DC voltage measured by voltmeter 201 to the voltage corresponding to the maximum power point.

[0119] Based on the measurement value of voltmeter 206, voltage control circuit 52 generates control command value for first DC / DC converter 203 to maintain the DC voltage (second DC voltage) of DC bus 205 at a predetermined target voltage.

[0120] The fifth control circuit 54 outputs control parameters and target values ​​for the MPPT control circuit 51 and the voltage control circuit 52, and manages the power generation status of the large solar power plant 26. The fifth control circuit 54 also outputs control signals for the first switching circuit 53.

[0121] The first switching circuit 53, according to the control signal from the fifth control circuit 54, selectively outputs either the output of the MPPT control circuit 51 or the voltage control circuit 52 as the control command value of the first DC / DC converter 203.

[0122] The first DC / DC converter 203 is controlled in either MPPT mode or voltage control mode. In MPPT mode, the first switching circuit 53 outputs the control command value generated by the MPPT control circuit 51. In voltage control mode, the first switching circuit 53 outputs the control command value generated by the voltage control circuit 52.

[0123] (2-2) Second control circuit 209

[0124] Figure 9 To explain Figure 6 The block diagram of the structure of the second control circuit 209 shown is shown.

[0125] like Figure 9 As shown, the second control circuit 209 includes a phase detection circuit 61, a first sine wave generation circuit 62, a current control circuit 60, and a sixth control circuit 67.

[0126] The current control circuit 60 includes a subtractor 63, a first PI control circuit 64, a multiplier 65, a subtractor 66, a second PI control circuit 68, and a first PWM converter 69. The current control circuit 60 executes a control mode that outputs power synchronously with the system voltage. This control mode is the control method used in ordinary photovoltaic power converters installed in homes.

[0127] Phase detection circuit 61 uses voltmeter 210 ( Figure 6 The phase of the AC voltage is detected by measuring the waveform of the AC voltage.

[0128] The first sine wave generation circuit 62 generates a sine wave synchronized with the waveform of the AC voltage based on the amplitude of the AC voltage measured by the voltmeter 210 and the phase information measured by the phase detection circuit 61. Furthermore, in Embodiment 1, the phase detection circuit 61 detects the zero-crossing point of the AC voltage waveform and detects the frequency of the AC voltage based on the zero-crossing point detection result. The phase detection circuit 61 outputs the measured frequency of the AC voltage along with the zero-crossing point information to the first sine wave generation circuit 62.

[0129] The current control circuit 60 is based on the voltmeter 206 ( Figure 6 The DC voltage of the measured DC bus 205 is used to generate a control command value for controlling the first DC / AC converter 208. Subtractor 63 subtracts the DC voltage of the DC bus 205 measured by voltmeter 206 from the target value of the DC bus voltage output by the sixth control circuit 67. The subtraction value obtained by subtractor 63 is input to the first PI control circuit 64.

[0130] Multiplier 65 multiplies the control command value output from the first PI control circuit 64 with the sine wave output from the first sine wave generation circuit 62 to generate a current command value.

[0131] Subtractor 66 calculates the current command value output from multiplier 65 and the current value from ammeter 211. Figure 6 The deviation of the measured current value of the AC system is output to the second PI control circuit 68.

[0132] The second PI control circuit 68 generates a control command value based on the control parameters (proportional gain and integral time) provided by the sixth control circuit 67, in a manner that ensures the deviation output from the subtractor 66 is zero. The second PI control circuit 68 outputs the generated control command value to the first PWM converter 69.

[0133] The first PWM converter 69 performs PWM control on the control command value input from the second PI control circuit 68, thereby generating a control command value, and outputs the generated control command value to the first DC / AC converter 208.

[0134] The sixth control circuit 67 collects measurement results of the DC bus 205 output from voltmeter 206 and ammeter 207, measurement results of the AC system output from voltmeter 210 and ammeter 211, and status information of the first DC / DC converter 203 output from the first control circuit 204, and notifies the CEMS 31 and the like of the collected information via communication I / F 212.

[0135] Additionally, the sixth control circuit 67 notifies the first PI control circuit 64 and the second PI control circuit 68 of control parameters. The sixth control circuit 67 also notifies the CEMS 31 of the active power and reactive power measured by the AC system's effective voltage measurement unit (not shown) via communication I / F 212. The sixth control circuit 67 then notifies the fifth control circuit 54 of the measured values ​​of the AC system's effective voltage and active power. For example, if the effective value of the system voltage exceeds a predetermined value, the fifth control circuit 54 switches the control of the large solar power plant 26 from MPPT control to voltage control, thereby suppressing the rise in system voltage.

[0136] (3-1) Third control circuit 404

[0137] Figure 10 To explain Figure 7 The block diagram of the structure of the third control circuit 404 shown is shown.

[0138] like Figure 10 As shown, the third control circuit 404 includes a charging control circuit 71, a discharging control circuit 72, a second switching circuit 73, and a seventh control circuit 74.

[0139] When the charging control circuit 71 performs charging control of the battery 40, it generates control command values ​​for the second DC / DC converter 403.

[0140] When the discharge control circuit 72 performs discharge control of the battery 40, it generates control command values ​​for the second DC / DC converter 403.

[0141] The 7th control circuit 74 outputs control parameters and target values ​​to the charging control circuit 71 and the discharging control circuit 72. The 7th control circuit 74 manages the state of charge (SOC), charging current, and discharging current of the battery 40. The 7th control circuit 74 outputs control signals to the 2nd switching circuit 73.

[0142] The second switching circuit 73, based on the control signal from the seventh control circuit 74, selectively outputs either the output of the charging control circuit 71 or the discharging control circuit 72 as the control command value for the second DC / DC converter 403. Specifically, when instructed to charge the battery 40, the second switching circuit 73 outputs the control command value generated by the charging control circuit 71. On the other hand, when instructed to discharge the battery 40, the second switching circuit 73 outputs the control command value generated by the discharging control circuit 72.

[0143] (3-2) Fourth control circuit 409

[0144] Figure 11 To explain Figure 7 The block diagram of the structure of the fourth control circuit 409 shown is shown.

[0145] like Figure 11 As shown, the fourth control circuit 409 includes an AC frequency detection circuit 81, an effective power calculation circuit 82, a virtual synchronous generator control circuit 83, an inverter current control circuit 84, an inverter voltage control circuit 85, a third switching circuit 86, a dead time detection circuit 90, a switching frequency calculation circuit 89, an eighth control circuit 87, and a control parameter generation circuit 88.

[0146] AC frequency detection circuit 81 uses voltmeter 410 ( Figure 7 The phase of the AC voltage is detected from the waveform of the measured AC voltage. In Embodiment 1, zero-crossing points are detected from the AC voltage waveform, and the frequency is detected based on the time interval between the detected zero-crossing points. However, the method for detecting the frequency of the AC voltage is not limited to methods using the detection results of zero-crossing points.

[0147] The effective power calculation circuit 82 uses a voltmeter 410 and an ammeter 411 ( Figure 7 The effective power is calculated using the measured AC voltage and AC current information. In Implementation 1, the effective power is calculated by accumulating the power of one cycle of the AC voltage waveform based on the zero-crossing detection information and AC frequency information output from the AC frequency detection circuit 81. However, the method for calculating effective power is not limited to the above method; for example, when the AC system is three-phase AC, the effective power can also be calculated using DQ conversion or similar methods.

[0148] The virtual synchronous generator control circuit 83, based on the frequency information of the AC voltage output from the AC frequency detection circuit 81 and the AC effective power information output from the effective power calculation circuit 82, enables the second DC / AC converter 408 (static inverter) to possess the inertial force, synchronization force, and braking force of a synchronous generator.

[0149] Virtual Synchronous Generator Control Technology

[0150] The following is a brief explanation of virtual synchronous generator control technology.

[0151] Synchronous generators typically used in thermal power generation have functions such as regulating output power in accordance with frequency (speed governor function), maintaining angular velocity (inertial force), achieving synchronization with system voltage (synchronization force), regulating the voltage of the backbone system (AVR function: Automatic Voltage Regulation function), and continuing to operate even when the AC system voltage drops instantaneously during system failures.

[0152] Based on virtual synchronous generator control technology, the transient response of a static inverter is controlled to enable the static inverter to simulate the functions of a synchronous generator. Specifically, three functions are simulated: the speed governor function, the function of simulating a mass system model based on the oscillation equation (dynamic characteristics of a rotating machine), and the AVR function.

[0153] In Embodiment 1, the case in which the second DC / AC converter 408 is equipped with a speed regulator function and a function that simulates a particle system model based on the oscillation equation will be described in particular. Figure 42 The diagram shown illustrates a concept diagram for explaining virtual synchronous generator control technology. Furthermore, regarding the AVR function of the synchronous generator, since it is primarily a function controlled based on output voltage commands or reactive power commands notified from the upper-level system (CEMS 31 in Embodiment 1), it is not included in Embodiment 1. Hereinafter, the governor function and the function simulating a mass system model based on the oscillation equation will be specifically explained.

[0154] First, let me explain the function of the speed controller.

[0155] The speed governor in a power plant controls the output power of the generator by controlling the output of the gas turbine or steam turbine in thermal and nuclear power generation, and / or the guide vanes of the turbine in hydroelectric power generation. In an AC power system, when the demand for power exceeds the supply, the frequency of the system voltage decreases. In thermal or hydroelectric generators capable of output control, by drooping the speed governor, the generator is controlled to increase power generation when the system voltage frequency decreases. Conversely, when the system voltage frequency rises due to the supply exceeding the demand, the generator is controlled to decrease power generation.

[0156] Figure 42 A diagram illustrating the function of a speed governor. (e.g.) Figure 42As shown, when the angular velocity ω of the synchronous generator increases, the valve regulating the energy inflow moves to the right, thereby reducing the energy supplied to the synchronous generator. Conversely, when the angular velocity ω of the synchronous generator decreases, the valve moves to the left, thereby increasing the energy supplied to the synchronous generator. Thus, the energy output from the synchronous generator can be individually controlled based on the frequency of its own system voltage (i.e., the angular velocity ω of the synchronous generator). Even when the synchronous generators perform the above operations individually, the operation is managed based on the frequency of the system voltage, allowing the load to be shared among multiple synchronous generators. Regarding the speed governor, the Japan Institute of Electrical Engineering provides a standard model based on a first-order lag system.

[0157] In Implementation 1, the operation of approximating the speed controller using a model composed of the first-order hysteresis system described above will be explained as shown in Equation (1).

[0158] -1 / {Kgd×(l+s×Tg)}…(1)

[0159] In equation (1), -1 / Kgd is the proportional gain of the speed governor (Kgd: speed regulation rate), and Tg is the time constant of the first-order lag system (Tg: speed governor time constant).

[0160] Next, we will explain the functionality of the simulation model of a point mass system based on the oscillation equation.

[0161] like Figure 42 As shown, the synchronous generator system has a rotor with a unit inertia constant M. For example, when the power generation of the large solar power plant 26 decreases suddenly due to a sudden change in solar irradiance, the insufficient power cannot be supplied instantaneously according to the speed governor control mentioned above. The synchronous generator converts the rotational energy accumulated in the rotor into electricity and outputs it to the AC system. At this time, when the angular velocity (rotation speed) of the rotor decreases, the energy supplied by the speed governor control increases, thereby balancing the demand for electricity with the supply of electricity. The following equation (2) shows the oscillation equation of the simulated mass system model (generator rotor). The oscillation equation is the equation that transforms the energy P by dividing the angular velocity ω into torque T.

[0162] Tin-Tout=M×dω / dt+Dg×ω…(2)

[0163] Where Dg is the braking coefficient and M is the inertial constant.

[0164] In Implementation 1, the case of simulating the inertial force, synchronization force and braking force of a synchronous generator by incorporating Equations (1) and (2) into the control of a static inverter (second DC / AC converter 408) will be explained.

[0165] Back Figure 11The inverter current control circuit 84 generates control command values ​​for current control of the second DC / AC converter 408. Additionally, the inverter current control circuit 84 and... Figure 9 The current control circuit 60 shown is identical in circuit structure and operation, only differing in control parameters; therefore, detailed descriptions are omitted.

[0166] The inverter voltage control circuit 85 generates control command values ​​for voltage control of the second DC / AC converter 408.

[0167] The third switching circuit 86 switches between control command values ​​from the inverter current control circuit 84 and control command values ​​from the inverter voltage control circuit 85 based on the output of the eighth control circuit 87.

[0168] The 8th control circuit 87 collects the measurement results of the DC bus 405 obtained from the voltmeter 406 and the ammeter 407, as well as the status information of the 2nd DC / DC converter 403 output from the 3rd control circuit 404, and notifies the CEMS 31 and the like of the collected information via the communication I / F 412.

[0169] In addition, the 8th control circuit 87 notifies the virtual synchronous generator control circuit 83, the inverter current control circuit 84, and the inverter voltage control circuit 85 of their respective control parameters.

[0170] Furthermore, the 8th control circuit 87 notifies the CEMS 31 of the effective voltage of the AC system (not shown) measured by the effective voltage measuring unit of the AC system, or the active and reactive power (not shown) measured by the active / reactive power measuring unit of the AC system. The 8th control circuit 87 also notifies the 7th control circuit 74 of the measurement results of the effective voltage and active power of the AC system.

[0171] The control parameter generation circuit 88 generates various parameters for virtual synchronous generator control (speed regulation rate Kgd, governor time constant Tg, inertia constant M, and braking coefficient Dg) based on the information required for generating control parameters for virtual synchronous generator control received from CEMS 31 via communication I / F 412. At this time, the control parameter generation circuit 88 also generates the ΔP / ΔF characteristic and outputs it to the switching frequency calculation circuit 89, which calculates the frequency at which the charging and discharging of battery 40 is switched (hereinafter also referred to as the "switching frequency"). Furthermore, the generated parameters for virtual synchronous generator control are notified to the virtual synchronous generator control circuit 83 via the eighth control circuit 87.

[0172] The switching frequency calculation circuit 89 uses the ΔP / ΔF characteristic output by the control parameter generation circuit 88 and the power target value notified from CEMS 31 by the 8th control circuit 87 to calculate the frequency at which the charging and discharging of the battery 40 is switched (switching frequency). The calculation method for the switching frequency will be explained later.

[0173] The dead-time detection circuit 90 calculates the dead-time based on the switching frequency calculated by the switching frequency calculation circuit 89 and the dead-time width information notified from the CEMS 31. In Embodiment 1, the dead-time detection circuit 90 detects the dead-time based on the charge / discharge switching detection information notified from the 7th control circuit 74 and the detection result of the AC frequency output from the AC frequency detection circuit 81, and notifies the 7th control circuit 74 of the dead-time information (dead-time detection flag) via the 8th control circuit 87.

[0174] (3-2-1) AC Frequency Detection Circuit 81

[0175] Figure 12 To explain Figure 11 The block diagram shown is of the structure of the AC frequency detection circuit 81.

[0176] like Figure 12 As shown, the AC frequency detection circuit 81 includes a phase detection circuit 810, a frequency detection circuit 811, and a second sine wave generation circuit 812.

[0177] The phase detection circuit 810 detects zero-crossing points from the waveform of the system voltage output from the voltmeter 410. The phase detection method of the phase detection circuit 810 is not limited to zero-crossing point detection. In actual equipment, zero-crossing point detection is affected by errors such as the zero-crossing point detection error of the voltmeter 410 (mainly offset error), the amplitude detection error of the voltmeter 410 (mainly linearity error), and the sampling period error when sampling the system voltage waveform. Furthermore, when sampling using a microcomputer, the sampling period error may occur due to variations in the time from carrier interruption to actual sampling.

[0178] The frequency detection circuit 811 detects the system frequency based on the period of the zero-crossing point output from the phase detection circuit 810. However, the method for detecting the system frequency is not limited to detecting based on the period of the zero-crossing point.

[0179] The second sine wave generation circuit 812 generates a sine wave synchronized with the system voltage based on the zero-crossing detection results of the phase detection circuit 810, the system frequency detection results of the frequency detection circuit 811, and the amplitude of the system voltage output from the CEMS 31. The AC frequency detection circuit 81 outputs the zero-crossing detection results (the detection time of the zero-crossing), the frequency detection results, and the sine wave information.

[0180] (3-2-2) Inverter voltage control circuit 85

[0181] Figure 13 To explain Figure 11 The block diagram shown is of the structure of the inverter voltage control circuit 85.

[0182] like Figure 13 As shown, the inverter voltage control circuit 85 includes a third sine wave generation circuit 851, a subtractor 852, a third PI control circuit 853, a first current limiting circuit 855, and a second PWM converter 854.

[0183] Inverter voltage control circuit 85 is based on virtual synchronous generator control circuit 83. Figure 11 The frequency and phase information output from the 8th control circuit 87 ( Figure 11 The amplitude information of the output system voltage is used to generate control command values ​​for controlling the second DC / AC converter 408. In addition, the amplitude information of the system voltage from the eighth control circuit 87 is input to the inverter voltage control circuit 85 via the second sine wave generation circuit 812.

[0184] From AC frequency detection circuit 81 ( Figure 11 The sinusoidal information (frequency, phase, and amplitude information) is input to the third sine wave generation circuit 851. However, in Embodiment 1, since QV control is not performed in the virtual synchronous generator control circuit 83, the amplitude information is not controlled.

[0185] The third sine wave generation circuit 851 generates a target value (target AC voltage) of the AC voltage output from the second DC / AC converter 408 based on the input sine wave information.

[0186] Subtractor 852 calculates the deviation between the target value of the AC voltage from the third sine wave generation circuit 851 and the voltage measured by voltmeter 410, and outputs the calculated deviation to the third PI control circuit 853.

[0187] The third PI control circuit 853 performs PI (proportional-integral) calculations to ensure the input deviation is zero, thereby generating a voltage command value. The third PI control circuit 853 outputs the generated voltage command value to the first current limiting circuit 855.

[0188] The first current limiting circuit 855 limits the voltage command value output from the third PI control circuit 853 based on the measurement result of the ammeter 411 input via the eighth control circuit 87. Specifically, when a current exceeding the current capacity of the second DC / AC converter 408 flows, the first current limiting circuit 855 controls the current flowing through the second DC / AC converter 408 to be below a predetermined current value (e.g., the current capacity of the second DC / AC converter 408) by limiting the voltage command value. The output of the first current limiting circuit 855 is input to the second PWM converter 854. Furthermore, the control parameters (control gain and integral time) in the third PI control circuit 853 and the first current limiting circuit 855 are provided from the eighth control circuit 87.

[0189] The second PWM converter 854 uses the voltage command value output from the first current limiting circuit 855 to perform PWM (Pulse Width Modulation) control, thereby generating a control signal. The second PWM converter 854 outputs the generated control signal to the second DC / AC converter 408.

[0190] (3-2-3) Virtual Synchronous Generator Control Circuit 83

[0191] Figure 14 To explain Figure 11 The diagram shows the structure of the virtual synchronous generator control circuit 83.

[0192] like Figure 14 As shown, the virtual synchronous generator control circuit 83 includes a subtractor 832, a speed governor control circuit 833, an adder 835, a subtractor 836, and a mass system operation circuit 837.

[0193] The subtractor 832 calculates the deviation between the measured frequency and the reference frequency Fref output from the 8th control circuit 87. The output of the subtractor 832 is input to the speed controller control circuit 833. Based on the output of the subtractor 832, the speed controller control circuit 833 generates an offset value to be added to the target power value. The detailed operation of the speed controller control circuit 833 will be described later.

[0194] Adder 835 adds the offset value output from speed controller control circuit 833 to the power target value Pref input from 8th control circuit 87, thereby generating the control power target value of mass system operation circuit 837.

[0195] Subtractor 836 calculates the deviation between the effective power input from effective power calculation circuit 82 and the target value of control power input from adder 835. The output of subtractor 836 is input to mass system operation circuit 837.

[0196] The mass system calculation circuit 837 calculates the frequency and phase of the system voltage output from the power conversion device 41 in such a way that the deviation output from the subtractor 836 is zero. Furthermore, in Embodiment 1, the control parameters (speed regulation rate Kgd, governor time constant Tg, inertia constant M, and braking coefficient Dg) of the speed governor control circuit 833 and the mass system calculation circuit 837 are received from the control parameter generation circuit 88 via the eighth control circuit 87.

[0197] (3-2-3-1) Speed ​​Regulator Control Circuit 833

[0198] Figure 15 To explain Figure 14 The block diagram shown is of the structure of the speed controller control circuit 833.

[0199] like Figure 15 As shown, the speed controller control circuit 833 has a multiplier 91, a first-order lag system model 92, and a limiter circuit 93.

[0200] Multiplier 91 multiplies the output of subtractor 832 with the proportional gain (-1 / Kgd) output from the 8th control circuit 87. The output of multiplier 91 is input to the first-order lag system model 92. In Embodiment 1, the first-order lag system model 92 is implemented as the standard model of a first-order lag system proposed by the Institute of Electrical Engineers of Japan (1 / (1+s×Tg)). Limiter circuit 93 performs limiter processing on the output of the first-order lag system model 92.

[0201] (3-2-3-2) Operational Circuit of Particle System 837

[0202] Figure 16 To explain Figure 14 The block diagram shown is of the structure of the particle system operational circuit 837.

[0203] like Figure 16 As shown, the particle system operation circuit 837 includes a subtractor 101, an integrator 102, a multiplier 103, a divider 104, an adder 105, and a phase calculation circuit 106.

[0204] Subtractor 101 calculates the deviation between the output of subtractor 836 and the output of multiplier 103. The output of subtractor 101 is input to integrator 102.

[0205] Integrator 102 makes the output of subtractor 101 a multiple of 1 / M and then integrates it, thereby generating Figure 42 The target angular velocity of the generator rotor (2 × π × target frequency (e.g., 60 Hz)) is shown as the difference Δω between the target angular velocity and the generator rotor's angular velocity. The output of integrator 102 is input to multiplier 103.

[0206] Multiplier 103 multiplies the output of integrator 102 with the braking coefficient Dg input from the 8th control circuit 87.

[0207] The particle system operation circuit 837 is configured to control the second DC / AC converter 408 based on the deviation between the output of the subtractor 836 and the output of the multiplier 103, thereby simulating the braking force of a synchronous generator.

[0208] Divider 104 divides the output Δω of integrator 102 by 2×π, thereby transforming it into the frequency difference Δf. Adder 105 adds the target frequency (60Hz) to the frequency difference information Δf, thereby transforming the frequency difference information Δf into the frequency (rotation frequency) of the generator rotor. The output of adder 105 is input to phase calculation circuit 106. Phase calculation circuit 106 calculates the phase of the generator rotor.

[0209] Next, the transfer function of the oscillation equation of the particle system operation circuit 837 will be explained. The transfer function of the oscillation equation is shown in equation (3) below, and can be expressed using the proportional gain (1 / Dg) and time constant (M / Dg) of the first-order lag system.

[0210] (1 / M×s) / {l+Dg / M×(1 / s)}

[0211] =(1 / Dg)×[1 / {1+(M / Dg)×s}…(3)

[0212] In addition, the governor time constant Tg and the mass system computation unit time constant M / Dg in the virtual synchronous generator control are determined based on the required response speed of the system.

[0213] (Operating overview of power conversion equipment)

[0214] Next, a summary of the operation of the power conversion device of Embodiment 1 will be described.

[0215] Figure 17 A diagram illustrating the area covered by the virtual synchronous generator controlled by the power conversion device 41. Figure 17 The horizontal axis represents response time, and the vertical axis represents the magnitude of demand fluctuations.

[0216] like Figure 17 As shown, the virtual synchronous generator control equipped in the static inverter covers minute fluctuations and short-cycle fluctuations ranging from tens of milliseconds to several minutes. For fluctuations longer than several minutes, load frequency control (LFC) or economic load sharing control (EDC) can be used to address them. Therefore, in Embodiment 1, the response performance of the virtual synchronous generator control is described as less than 1 second.

[0217] In the following description, the term "connected to" is used. Figure 2 The model shown is composed of the battery 40, power conversion device 41, power distribution system impedance 29, and load 600 of the power distribution system 24. For simplicity, the inverter capacity of the power conversion device 41 is assumed to be 4kW, and the capacity of the load 600 is assumed to be a maximum of 4kW.

[0218] Figure 18 This diagram illustrates the control of the virtual synchronous generator equipped with the power conversion device 41 in Embodiment 1. Figure 18 This is an example illustrating the relationship between the speed regulation rate Kgd and the system frequency when the power consumption of load 600 changes while the target power value remains constant. Figure 18 To show Figure 2 The system frequency of each speed regulation rate Kgd under steady state was obtained from CEMS 31 when the load 600 changes from 2kW to 4kW under a power target value of 2kW. In addition, the governor time constant Tg, inertia constant M, and braking coefficient Dg are fixed at constant values.

[0219] exist Figure 18 In the example, the system frequency decreases as the value of Kgd increases until Kgd reaches 0.343. On the other hand, it was confirmed that the system frequency converges when Kgd exceeds 0.343.

[0220] Figure 19 This diagram illustrates the control of the virtual synchronous generator equipped with the power conversion device 41 in Embodiment 1. Figure 19 This is an example illustrating the relationship between the braking coefficient Dg and the system frequency when the load changes abruptly. Figure 19 To show Figure 2 The system frequency of each braking coefficient Dg when the load changes from 2kW to 4kW under a power target value of 2kW, as notified from CEMS 31. In addition, the governor time constant Tg, inertia constant M, and speed regulation rate Kgd (=0.343) are fixed at constant values. Figure 19 In the example, it was confirmed that the decrease in system frequency increases as the braking coefficient Dg decreases.

[0221] Generally, the system frequency limits (upper and lower limits) are approximately ±1 to 2% of the reference frequency (hereinafter also referred to as Fref). Therefore, when the reference frequency Fref is 60Hz, the upper limit of the system frequency is approximately 61.2 to 60.6Hz, and the lower limit is approximately 59.4 to 58.8Hz. Therefore, the speed regulation rate Kgd and braking coefficient Dg controlled by the speed controller need to be set in a way that ensures the system frequency falls within the frequency range determined by the above limits.

[0222] Next, we will explain the descent characteristics (ΔP / ΔF characteristics).

[0223] Figure 20 A diagram illustrating an example of the ΔP / ΔF characteristics. Figure 20 The horizontal axis represents the deviation between the actual output power of the power conversion device 41 and the target power value Pref, i.e., the differential power ΔP. When the output power of the power conversion device 41 is greater than the target power value Pref, the differential power ΔP is positive.

[0224] Figure 20 The vertical axis represents the deviation between the frequency of the AC voltage output by the power conversion device 41 and the reference frequency Fref (e.g., 60Hz) of the AC system, i.e., the differential frequency ΔF. When the frequency of the AC voltage output by the power conversion device 41 is greater than the reference frequency Fref, the differential frequency ΔF is positive. ΔFmax is the maximum value of the differential frequency ΔF.

[0225] In the virtual synchronous generator control circuit 83 of implementation method 1 ( Figure 11 )middle, Figure 20 The ΔP / ΔF characteristic shown is determined by the capacity, speed regulation rate Kgd, and braking coefficient Dg of the static inverter (second DC / AC converter 408). Furthermore, in Figure 20 Without considering the charging of battery 40, the power target value is set to half the capacity of the static inverter (second DC / AC converter 408). Figure 20 Showing will Figure 2 The ΔP / ΔF characteristic is defined as follows: when the power consumption of the medium load 600 is the same as the capacity of the static inverter (second DC / AC converter 408), the upper limit is the system frequency (Fref+ΔFmax), and the lower limit is the system frequency when the power consumption of the load 600 is zero (Fref-ΔFmax).

[0226] In implementation method 1, Figure 20 The ΔP / ΔF characteristic shown is called the "reference ΔP / ΔF characteristic". As mentioned above, the reference ΔP / ΔF characteristic is the ΔP / ΔF characteristic under the following conditions: In the discharge mode of battery 40, half the capacity of the static inverter is used as the power target value. When the output of the static inverter matches the capacity, the system frequency is the upper limit (Fref + ΔFmax), and when the output of the static inverter is zero, the system frequency is the lower limit (Fref - ΔFmax). Details of the discharge mode will be explained later.

[0227] Figure 21 This is a diagram showing the frequency response waveform of the AC voltage output from the static inverter when the load changes abruptly under the control of the virtual synchronous generator equipped with the power conversion device 41 in Embodiment 1.

[0228] like Figure 17As explained earlier, the virtual synchronous generator control equipped with a static inverter covers minute vibrations and short-cycle fluctuations ranging from tens of milliseconds to several minutes. Therefore, a response performance of less than one second is required for the virtual synchronous generator control. Generally, decreasing the time constant improves the response performance, but introduces vibrations into the response waveform. Furthermore, when multiple distributed power sources operate collaboratively, problems such as unnecessary cross currents may occur. Therefore, in implementation method 1, as... Figure 21 As shown, the speed controller control circuit 833 is determined by the method to make the system frequency converge in about 1 second. Figure 15 ) and the particle system operation circuit 837 ( Figure 16 The time constant of ).

[0229] (Problems with previous virtual synchronous generator control)

[0230] Next, we will explain the problems when configuring two power conversion devices 41 equipped with conventional virtual synchronous generator control in a power distribution system.

[0231] Figure 22 (A) shows the waveforms of the power consumption of the load and the power generated by the large solar power plant 26 in a self-sufficient system consisting of two power conversion devices 41 equipped with conventional virtual synchronous generator control. The power generated by the large solar power plant 26 increases sharply at time t1 and equals the power consumption of the load at time t2. That is, after time t2, the power generated by the large solar power plant 26 and the power consumption of the load are in a balanced state.

[0232] Figure 22 (B) shows the response waveform of the effective value of the AC power output from each power conversion device 41 (the second DC / AC converter 408). The solid line shows the response waveform of the output power of the power conversion device 41a connected to the battery 40a, and the dashed line shows the response waveform of the output power of the power conversion device 41b connected to the battery 40b.

[0233] The inverter capacities of the two power conversion devices 41 are set to be the same. Before time t1, each power conversion device 41 releases 60% of its inverter capacity. Figure 22 (B) shows the previous response waveform when the power generation of the large solar power plant 26 increases sharply at time t1, and the power consumption of the load becomes balanced with the power generation of the large solar power plant 26.

[0234] Such as AC frequency detection circuit 81 ( Figure 11As described in the description, the outputs of sensors such as voltmeters and ammeters have sensor errors (e.g., about 5%). Specifically, each sensor has offset error and linearity error. For example, when the voltmeter has a 1% offset error, for an AC voltage of 0V, the voltmeter outputs -5.76V (288V × 2 × 0.01 = 5.76V). Therefore, according to the conventional power conversion device 41, due to the aforementioned sensor errors, cases occur where power is output from the power conversion device 41 even when the power command value is zero.

[0235] This is because it controls the second DC / DC converter 403 ( Figure 7 The third control circuit 404 controls the charging and discharging power of the battery 40 to maintain a constant DC voltage on the DC bus 405. Therefore, due to the aforementioned sensor error, the following situation occurs: even if charging and discharging are not originally required, the battery 40's power is either discharged via the power conversion device 41 or charged via the power conversion device 41 due to the drooping characteristics (ΔP / ΔF characteristics) in the virtual synchronous generator control. Figure 22 In case (B) (previous control), battery 40a receives power from the distribution system and is charged at time t2 when the generated power of the large solar power plant 26 is balanced with the power consumed by the load. On the other hand, battery 40b releases power to the distribution system at time t2. Here, since the generated power of the large solar power plant 26 is balanced with the power consumed by the load, the discharged power of battery 40b is used to charge battery 40a. That is, the work of charging the discharged power of one battery (battery 40b) to another battery (battery 40a) is carried out, or in other words, a catch-ball operation of charging and discharging is performed. This unnecessary power exchange between battery 40a and battery 40b may cause power loss due to charging and discharging, and exacerbate the deterioration of battery 40a.

[0236] Next use Figure 23 This section describes the operation of power conversion devices 41a and 41b equipped with the virtual synchronous generator control according to Embodiment 1. In the following description, the voltmeter and ammeter built into the power conversion devices 41a and 41b have... Figure 22 The same error applies to the case.

[0237] In Embodiment 1, a dead zone is incorporated near the charging / discharging switching frequency of the battery 40 in the droop characteristics (ΔP / ΔF characteristics) of each power conversion device 41. Details regarding the dead zone in the droop characteristics will be explained later.

[0238] Figure 23 (A) and Figure 22Figure (A) also shows the waveforms of the power consumption of the load and the power generated by the large solar power plant 26 in a self-sufficient system consisting of two power conversion devices 41. The power generated by the large solar power plant 26 increases sharply at time t1 and becomes equal to the power consumption of the load at time t2. That is, after time t2, the power generated by the large solar power plant 26 and the power consumption of the load are in equilibrium.

[0239] Figure 23 (B) shows the response waveform of the effective value of the AC power output from each power conversion device 41 (second DC / AC converter 408). The solid line shows the response waveform of the output power of the power conversion device 41a connected to the battery 40a, and the dashed line shows the response waveform of the output power of the power conversion device 41b connected to the battery 40b.

[0240] Furthermore, it is assumed that the inverters of the two power conversion devices 41 have the same capacity. Before time t1, each power conversion device 41 releases 60% of its inverter capacity. Figure 23 (B) shows the response waveform when the power generation of the large solar power plant 26 increases sharply at time t1, and the power consumption of the load becomes balanced with the power generation of the large solar power plant 26.

[0241] In Implementation 1, based on information used when generating control parameters for virtual synchronous generator control, as notified from CEMS 31, the ΔP / ΔF characteristic is calculated. Using the calculated ΔP / ΔF characteristic and the target power value, the frequency at which the charging and discharging of the battery 40 is switched (switching frequency) is derived. Then, a dead zone is set in the ΔP / ΔF characteristic (decreasing characteristic) near the derived switching frequency. The second DC / DC converter 403 and the second DC / AC converter 408 are controlled based on the ΔP / ΔF characteristic with this dead zone, thereby controlling the charging and discharging power of the battery 40 to be "zero".

[0242] Furthermore, the information used for detecting the dead zone is set to the detection result of the system frequency output from the virtual synchronous generator control circuit 83 or the frequency of the system voltage output from the AC frequency detection circuit 81. Additionally, when there is a detection result for the frequency of the system frequency output from the virtual synchronous generator control circuit 83 or the frequency of the system voltage output from the AC frequency detection circuit 81 within the dead zone frequency range, the virtual synchronous generator control circuit 83 continues to operate normally.

[0243] Back Figure 23In (B), from time t1 onwards, as the amount of solar irradiance changes and the power generation of the large solar power plant 26 increases until time t2 when it reaches equilibrium with the power consumption of the load, in addition to the power generated by the large solar power plant 26, the power discharged by the batteries 40a and 40b is also used to support the power distribution system. At this time, although the target power value from the CEMS 31 is the same, due to the aforementioned sensor error, a power difference arises between the power outputs from each power conversion device 41 (the second DC / AC converter 408). Then, when time t2 arrives and the power consumption of the load is balanced with the power generation of the large solar power plant 26, the output power of the power conversion device 41a is controlled such that during the dead zone width (details will be explained later) when the battery 40a switches from discharging to charging, the charging and discharging power of the battery 40a is "zero". Therefore, after time t2, the output power of the power conversion device 41a remains "zero". On the other hand, as the power conversion device 41b approaches time t2, it reduces the discharge power, and eventually, like the power conversion device 41a, the output power remains at "zero".

[0244] According to Embodiment 1, since unnecessary power exchange between batteries 40a and 40b, which has been a technical problem in conventional control, can be suppressed, power loss caused by unnecessary charging and discharging can be suppressed, and the deterioration of batteries 40a and 40b can be suppressed.

[0245] (Method for creating control parameters for virtual synchronous generator control)

[0246] Next, the method for creating the control parameters (ΔP / ΔF characteristics) of the virtual synchronous generator control for each power conversion device 41 in CEMS 31 will be explained. The control parameters are generated by the control parameter generation circuit 13 within CEMS 31. Figure 3 The ΔP / ΔF characteristics of each power conversion device 41 are created using CEMS 31 in Implementation 1. As described above, a reference ΔP / ΔF characteristic (reference ΔP / ΔF characteristic) is created. For simplicity, the following explanation will only cover the discharge operation of the battery 40.

[0247] When the battery 40 operates only in discharging or charging mode, a baseline ΔP / ΔF characteristic is created where ΔP for ΔFmax is half the capacity of the static inverter. Conversely, when charging and discharging operations are included (especially when the power target value is near zero), a baseline ΔP / ΔF characteristic is created where ΔP for ΔFmax is the capacity of the static inverter. In this case, the same strategy needs to be applied to all power conversion devices 41 managed by the CEMS 31. Therefore, the ΔP / ΔF characteristic is not created where one of the multiple power conversion devices 41 considers charging and discharging operations while the others only consider charging or discharging operations.

[0248] Furthermore, as shown in Embodiment 1, when creating ΔP / ΔF characteristics for multiple power conversion devices 41, it is necessary to create ΔP / ΔF characteristics by switching the charging and discharging of each power conversion device 41 at the same ΔF value. This is based on the following reasons.

[0249] The following case occurs: When the ΔF value of the switching between charging and discharging is different among multiple power conversion devices 41, when the power target value is positive (discharging), as the power supplied to the power distribution system decreases, even if other power conversion devices 41 are discharging, the power conversion device 41 with the smallest absolute value of the ΔF value of the switching between charging and discharging will switch to charging mode and receive the discharge power from other power conversion devices 41 to charge the corresponding battery 40.

[0250] Similarly, the following case occurs: when the power target value is negative (charging), even if other power conversion devices 41 are charging, the power conversion device 41 with the smallest absolute value of the ΔF value of the charge / discharge switching is switched to discharge mode and supplies discharge power to other power conversion devices 41.

[0251] In each case, power loss occurs in each power conversion device 41 due to unnecessary charging and discharging between multiple batteries 40, and the degradation of the batteries 40 is exacerbated. Therefore, in Embodiment 1, a ΔP / ΔF characteristic is created by switching the charging and discharging of each power conversion device 41 with the same ΔF value.

[0252] The following details the method for creating the ΔP / ΔF characteristics of each power conversion device 41 in CEMS 31.

[0253] like Figure 4As shown, the operation plan creation circuit 14 and the power generation prediction circuit 142 within CEMS 31 use weather forecast information from an external server (not shown) and power generation prediction data accumulated in a database within CEMS 31 (not shown) to predict the power generation of the large solar power plant 26. The database stores actual power generation data measured daily, at various times, and under various weather conditions.

[0254] Similarly, the power consumption prediction circuit 143 uses power consumption prediction data of user load accumulated in a database within the CEMS 31 (not shown) to predict the power consumption of user load. The database stores actual power consumption data of the load measured daily, at various times, and under various weather conditions.

[0255] The battery operation planning creation circuit 141 calculates the total charge and discharge power of each battery 40 based on the predicted power generation of the large solar power plant 26 and the predicted power consumption of the demand load. Then, based on the battery capacity of each battery 40 notified from the first management circuit 145, information about the charge amount and the inverter capacity of the power conversion device 41, and the calculation result of the total charge and discharge power, the battery operation planning creation circuit 141 calculates the target power value output to each power conversion device.

[0256] In Embodiment 1, the power target value for each power conversion device 41 is generated basically based on the battery capacity and charging amount of each battery 40, in a manner that ensures the charging amount and battery capacity are equal after 30 minutes. Furthermore, if the power target value exceeds the inverter capacity of the power conversion device 41, the power target value is adjusted to be below the inverter capacity. In Embodiment 1, the multiple power conversion devices 41, which are the objects of generating the power target value, are treated as a single power conversion device to create a reference ΔP / ΔF characteristic.

[0257] Specifically, the control parameter generation circuit 13 ( Figure 3 The total inverter capacity Cinv (Σ(Cinv)) of the multiple power conversion devices 41, which are the objects of generating the power target value, is calculated, and a reference ΔP / ΔF characteristic is generated by making the ΔP value for the ΔFmax value half of the total capacity (Σ(Cinv)) of the static inverters. In addition, only the discharge or charging of the battery 40 is considered.

[0258] When the reference ΔP / ΔF characteristic is generated, the control parameter generation circuit 13 calculates the sum of the power target values ​​of the multiple power conversion devices 41 generated by the operation plan creation circuit 14. Then, the control parameter generation circuit 13 treats the multiple power conversion devices 41 as one power conversion device and calculates the frequency (switching frequency) at which the charging and discharging of the battery 40 is switched. Specifically, in Embodiment 1, when the power target value is positive (discharging), the differential frequency ΔF, where ΔP = -(the sum of the power target values), is calculated in the reference ΔP / ΔF characteristic as the switching frequency. In the following description, the calculated differential frequency ΔF is also referred to as "switching frequency ΔF0".

[0259] Next, the control parameter generation circuit 13 generates the ΔP / ΔF characteristic based on the power target value of each power conversion device 41 notified from the operation plan creation circuit 14, the switching frequency ΔF0, and the inverter capacity. In Embodiment 1, the control parameter generation circuit 13 notifies the power conversion device 41 of the data representing the slope of the ΔP / ΔF characteristic and the power target value. (Control parameter generation circuit 88) Figure 11 Based on the information from the notification, various control parameters are generated within the virtual synchronous generator control circuit 83.

[0260] Additionally, the control parameter generation circuit 13 calculates the dead zone width assigned to the ΔP / ΔF characteristic. Details of the dead zone width generation method will be described later. For example, in a simplified implementation, the dead zone width can be set to approximately 5% of ΔFmax. Alternatively, the dead zone width can be changed accordingly to the SOC of each battery 40 or the inverter capacity. As a method to change the dead zone width accordingly to the SOC of the battery 40, for example, in discharge mode, in order to reduce the discharge power of batteries 40 with an SOC less than 20%, the dead zone width of these batteries 40 is made narrower than that of the other batteries 40. This allows batteries 40 with low SOC to quickly transition to charging mode. On the other hand, in charging mode, in order to reduce the charging power of batteries 40 with an SOC greater than 80%, the dead zone width of these batteries 40 is made narrower than that of the other batteries 40. This allows batteries with high SOC to quickly transition to discharge mode.

[0261] Figures 24A-24C This diagram illustrates an example of the ΔP / ΔF characteristics of a power conversion device 41 equipped with the virtual synchronous generator control of Embodiment 1. Dead zones are provided in each ΔP / ΔF characteristic.

[0262] Figure 24A This refers to the ΔP / ΔF characteristic when the power target value Pref notified from CEMS 31 is positive (discharge). For example... Figure 24AAs shown, at the time point ΔP = -Pref, i.e., the time point ΔF = ΔF0, the value of ΔP is fixed. Since ΔF0 is the switching frequency, the output of the second DC / AC converter 408 is set to "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF exceeds the dead zone. Then, when ΔF exceeds the upper limit frequency of the dead zone, the system switches from discharge mode to charging mode, controlling the second DC / AC converter 408 to charge the corresponding battery 40. Furthermore, when the system voltage ΔF falls below the switching frequency ΔF0 before exceeding the upper limit frequency of the dead zone, the second DC / AC converter 408 is again controlled in discharge mode.

[0263] On the other hand, when returning from charging mode to discharging mode, when ΔF falls below the upper limit frequency of the dead zone, the output of the second DC / AC converter 408 is fixed at "zero". Then, when ΔF drops below the lower limit frequency of the dead zone (switching frequency ΔF0), the second DC / AC converter 408 is switched to discharging mode. Furthermore, when ΔF falls above the upper limit frequency of the dead zone before dropping below the lower limit frequency of the dead zone (switching frequency ΔF0), the second DC / AC converter 408 is controlled in charging mode again.

[0264] Figure 24B This refers to the ΔP / ΔF characteristic when the power target value Pref notified from CEMS 31 is negative (charging). Figure 24B In this process, at the time point ΔP = Pref, i.e., after ΔF = ΔF0, the value of ΔP is fixed. Since ΔF0 is the switching frequency, the output of the second DC / AC converter 408 is set to "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF exceeds the dead zone. Then, when ΔF exceeds the lower limit frequency of the dead zone, the process switches from charging mode to discharging mode, controlling the second DC / AC converter 408 to discharge the corresponding battery 40. Furthermore, when the system voltage ΔF exceeds the switching frequency ΔF0 before exceeding the lower limit frequency of the dead zone, the second DC / AC converter 408 is again controlled in charging mode.

[0265] On the other hand, when returning from discharge mode to charging mode, when ΔF becomes above the lower limit frequency of the dead zone, the output of the second DC / AC converter 408 is fixed at "zero". Then, when ΔF exceeds the upper limit frequency of the dead zone (switching frequency ΔF0), the second DC / AC converter 408 is switched to charging mode. Furthermore, when ΔF drops below the lower limit frequency of the dead zone before exceeding the upper limit frequency of the dead zone (switching frequency ΔF0), the second DC / AC converter 408 is controlled in discharge mode again.

[0266] Figure 24CThe ΔP / ΔF characteristic is given when the power target value Pref, as notified from CEMS 31, is zero. Figure 24C In the middle, there is a dead zone centered at ΔP=0.

[0267] As described above, when multiple power conversion units 41 equipped with static inverters featuring virtual synchronous generator control are connected to the system, the drooping characteristic (ΔP / ΔF characteristic) imparted to each power conversion unit 41 by the virtual synchronous generator control has a dead zone. This prevents situations where, due to sensor errors in the voltmeters and ammeters, although the generated power of the large solar power plant 26 is balanced with the power consumed by the load, [further issues arise]. Figure 22 As shown in (B), the battery 40a is charged by the discharge power of the battery 40b. This can suppress the generation of power loss caused by unnecessary power exchange between batteries 40a and 40b and the aggravation of battery deterioration.

[0268] Furthermore, in Embodiment 1, a method for generating the ΔP / ΔF characteristic according to the following procedure is described. First, a reference ΔP / ΔF characteristic is generated by treating the multiple power conversion devices 41, which are the objects of generating the power target value, as a single power conversion device. Next, the frequency at which charging and discharging is switched (switching frequency ΔF0) is calculated using the generated reference ΔP / ΔF characteristic and the sum of the power target values ​​of the multiple power conversion devices 41. Finally, the ΔP / ΔF characteristic of each power conversion device 41 is generated using the calculated switching frequency ΔF0 and the power target value of each power conversion device 41.

[0269] However, the method for generating the ΔP / ΔF characteristic is not limited to this. For example, when multiple power conversion devices 41 are operating in discharge mode, the ΔP / ΔF characteristic of the power conversion device 41 corresponding to the battery 40 with the lowest SOC is generated. Then, the switching frequency ΔF0 is calculated based on the generated ΔP / ΔF characteristic and used as the switching frequency ΔF0 when generating the ΔP / ΔF characteristic for the power conversion devices 41 corresponding to other batteries 40.

[0270] Alternatively, when multiple power conversion devices 41 are operated in charging mode, a ΔP / ΔF characteristic is generated for the power conversion device 41 corresponding to the battery 40 with the highest SOC. Then, a switching frequency ΔF0 is calculated based on the generated ΔP / ΔF characteristic and used as the switching frequency ΔF0 when generating P / ΔF characteristics for the power conversion devices 41 corresponding to other batteries 40.

[0271] By generating ΔP / ΔF characteristics in this way, it is possible to generate ΔP / ΔF characteristics that match the battery 40 with the minimum SOC in discharge mode, and to generate ΔP / ΔF characteristics that match the battery 40 with the maximum SOC in charging mode.

[0272] (Operation of the power conversion device)

[0273] Next use Figures 1-3 8. A detailed description of the operation of the power conversion device in Implementation Method 1.

[0274] First refer to Figure 1 The power distribution system 24, which uses the power conversion device of Embodiment 1, will be described.

[0275] In implementation 1, in order to control the system voltage supplied from the substation 20 within a predetermined voltage range, the power distribution system 24 connects multiple SVRs 23 in series between the substation 20 and the power conversion device 27 (or power conversion device 41a or town 100a).

[0276] A power conversion device 41a is provided near the power conversion device 27. In Embodiment 1, the power conversion device 41a operates as a voltage source. The power conversion device 41a enables the virtual synchronous generator control circuit 83 ( Figure 11 This operation can smooth the power generation of large solar power plants 26.

[0277] As loads, there are towns 100a-100d, factories 110, buildings 112, and apartments 113. Power supplied from substation 20, generated by large solar power plant 26, and discharged by batteries 40a-40c is supplied to the loads. Emergency synchronous generators are installed in the factories and buildings.

[0278] Here, the operation of the distributed power system in the power distribution system 24, which receives power supplied from substation 20, generated power from large solar power plant 26, and discharged power from batteries 40a to 40c, will be explained. Figure 25 For the purpose of illustration Figure 1 The diagram shown illustrates the normal operation of a distributed power system centered on CEMS 31.

[0279] like Figure 25 As shown, the stable processing includes a process implemented in 30-minute cycles (hereinafter also referred to as "Process 1") and a process implemented in 5-minute cycles (hereinafter also referred to as "Process 2").

[0280] When the first processing cycle (30-minute cycle) begins, DSO 21 requests CEMS 31 to output the collected measurement data via communication line 25. Upon receiving the request from DSO 21, CEMS 31 sends measurement data, including the power consumption of each user, the power generation of the large solar power plant 26, and the charge / discharge capacity and SOC of the battery 40, collected over the past 30 minutes, to DSO 21.

[0281] Upon receiving measurement data, DSO 21 creates an operation plan for distribution system 24 based on the measurement data and notifies CEMS 31 of the created operation plan. The operation plan for distribution system 24 includes the power supply plan from substation 20 to distribution system 24, which is necessary for creating the operation plan (charge and discharge plan) for battery 40. DSO 21 creates a 24-hour power supply plan with a 30-minute cycle. The 30-minute cycle power supply plan represents the total amount of electricity supplied from substation 20 to distribution system 24 within 30 minutes.

[0282] When the CEMS 31 receives the operation plan (power supply plan) from the DSO 21, it requests the power conversion unit 41 to send measurement data. The measurement data includes the charge / discharge capacity and SOC information of the battery 40 over the past 5 minutes. Upon receiving the request from the CEMS 31, the power conversion unit 41 notifies the CEMS 31 of the measurement data.

[0283] CEMS 31 receives measurement data from all power conversion devices 41a to 41c connected to the power distribution system 24. At this time, CEMS 31 also collects measurement data such as the power consumption of each user for 30 minutes and the power generation of the large solar power plant 26.

[0284] Once the measurement data collection is complete, CEMS 31 creates an operating plan for battery 40 and the information needed to generate control parameters. The operating plan for battery 40 is a charging and discharging plan for battery 40, including target values ​​for the charging and discharging power of battery 40 (target power values). The method for creating the operating plan for battery 40 and the information needed to generate control parameters will be described later.

[0285] Once the operation plan for the battery 40 and the information required for generating control parameters are completed, the CEMS 31 notifies each power conversion device 41 of the corresponding operation plan for the battery 40 and the information required for generating control parameters, thus ending the first process.

[0286] Next, CEMS 31 performs the second processing step (5-minute cycle processing). CEMS 31 collects measurement data from each power conversion device 41 at 5-minute cycles. Based on the collected measurement data, CEMS 31 detects the deviation between the target power value and the actual charging / discharging power. When the deviation exceeds a predetermined threshold, CEMS 31 recalculates the operating plan (target power value) of the battery 40 and notifies each power conversion device 41 of the recalculation result. The specific method for recalculation will be described later.

[0287] (The work of CEMS 31)

[0288] Next, use Figure 26 This will explain the detailed operation of CEMS 31.

[0289] Figure 26 To show Figure 1 The flowchart of the control process of CEMS 31 is shown. Figure 26 As shown, when processing begins, CEMS 31 checks in step (hereinafter referred to as S) 01 whether it has received an output request for measurement data from DSO 21. If an output request is received (yes in S01), CEMS 31 collects measurement data from multiple power conversion devices 41 via S02. In S03, CEMS 31 notifies DSO 21 of the measurement data stored in storage circuit 12 via communication circuit 11.

[0290] On the other hand, when no output request is received from DSO 21 (no in S01) or when measurement data is sent to DSO 21 in S03, CEMS 31 proceeds to S04 to check whether an operation plan (power supply plan) has been received from DSO 21. When an operation plan is received (yes in S04), CEMS 31 proceeds to S05 to create an operation plan (charge and discharge plan) for battery 40.

[0291] Figure 27 To illustrate the process of creating the operating plan for the storage battery 40 ( Figure 27 The flowchart of S05).

[0292] like Figure 27 As shown, when the process begins, CEMS 31 predicts the power generation of the large solar power plant 26 via S051. Specifically, returning to... Figure 3 and Figure 4 When the operation plan is received from DSO 21, control circuit 16 ( Figure 3 The second management circuit 146 within the instruction operation plan creation circuit 14 ( Figure 4The second management circuit 146, upon receiving an instruction from the control circuit 16, instructs the power generation prediction circuit 142 via the battery operation plan creation circuit 141 to predict the power generation of the large solar power plant 26.

[0293] Upon receiving an instruction from the second management circuit 146, the power generation prediction circuit 142 accesses a weather forecast server configured on the Internet (not shown) to obtain a 24-hour weather forecast for the period 24 hours from now. Using the obtained 24-hour weather forecast and data stored in a power generation prediction database (not shown) managed by the power generation prediction circuit 142, the power generation prediction circuit 142 predicts the power generation for the 24 hours from now. Furthermore, the power generation prediction database is constructed based on actual power generation data and weather information collected at 30-minute intervals from the large solar power plant 26. The method for constructing the database will be omitted.

[0294] When the power generation is predicted in S051, CEMS 31 predicts the user's power consumption via S052. Specifically, returning to... Figure 4 When the second management circuit 146 receives the power generation prediction result of the large solar power plant 26 from the power generation prediction circuit 142, it instructs the power consumption prediction circuit 143 to predict the power consumption of users via the battery operation plan creation circuit 141.

[0295] When the power consumption prediction circuit 143 receives an instruction from the second management circuit 146, it uses data stored in a power consumption prediction database (not shown) managed by the power consumption prediction circuit 143 to predict the user's power consumption for the next 24 hours. Furthermore, the power consumption prediction database is constructed by processing user power consumption data collected in 30-minute cycles based on date, time, and weather information. The method for constructing the database will be omitted.

[0296] When user power consumption is predicted in S052, CEMS 31 creates a demand plan via S053. Specifically, returning to... Figure 4 When the battery operation plan creation circuit 141 receives the predicted power consumption of the user from the power consumption prediction circuit 143, it calculates the total charge and discharge capacity of the batteries 40a to 40c every 30 minutes based on the predicted power generation of the large solar power plant 26 obtained from the power generation prediction circuit 142, the predicted power consumption of the user obtained from the power consumption prediction circuit 143, and the operation plan (power supply plan every 30 minutes) notified from DSO 21.

[0297] When a demand plan is created in S053, CEMS 31 specifies the charge and discharge power (target power value) for battery 40A to 40C via S054. Specifically, returning to... Figure 3 and Figure 4 The battery operation plan creation circuit 141 allocates the charging and discharging power of each battery 40 every 30 minutes proportionally based on the SOC information and battery capacity of the batteries 40a to 40c collected by the communication circuit 11 and stored in the storage circuit 12.

[0298] In Implementation 1, when creating a 24-hour operation plan for the storage batteries 40, the CEMS 31 determines the charging and discharging power of each storage battery 40 so that the SOC of the storage batteries 40a to 40c is simultaneously zero, or that the storage batteries 40a to 40c are almost simultaneously fully charged when in charging mode.

[0299] This is based on the following reasons. For example, suppose that because a cloud passes over the large solar power plant 26 for about 5 minutes, the power output of the large solar power plant 26 decreases from 10MW to 4MW. In addition, suppose that the capacities of the static inverters of the power conversion devices 41a to 41c are 8MW, 4MW, and 2MW, respectively.

[0300] Here, assuming that battery 40a stops discharging because its SOC reaches zero first, the power conversion devices 41b and 41c are notified of the battery's operating plan, causing the remaining batteries 40b and 40c to discharge 1MW and 0.5MW respectively. When the power generation of the large solar power plant 26 decreases by 6MW due to a sudden change in solar irradiance, the discharge power from batteries 40b and 40c can only be supplemented by 3MW and 1.5MW respectively through virtual synchronous generator control, thus failing to compensate for the shortfall of 6MW.

[0301] On the other hand, when batteries 40a to 40c are operating, the discharge can reach a maximum of 14MW (=8MW+4MW+2MW), thus expanding the range of power that can be compensated through virtual synchronous generator control. Therefore, when creating an operation plan (charge and discharge plan) for battery 40 in CEMS 31, it is necessary to create an operation plan in a way that makes batteries 40a to 40c almost simultaneously at zero SOC or fully charged.

[0302] When the charging and discharging power (target power value) of batteries 40a-40c is set in S054, CEMS 31 checks in S055 whether the information required for generating the control parameters for virtual generator control has been generated for all batteries 40a-40c. If the information generation for all batteries 40a-40c has not yet been completed (no in S055), CEMS 31 proceeds to S056 to generate the information required for generating the control parameters for virtual generator control.

[0303] Figure 28 This illustrates the processing of information required to generate the control parameters for generating the virtual synchronous generator control. Figure 27 The flowchart of S056). Figure 28 The processing shown is performed by the control parameter generation circuit 13 within the CEMS 31. Figure 5 ) to execute.

[0304] like Figure 28 As shown, when processing begins, control circuit 136 is activated via S0561. Figure 5 Collected in Figure 27 The S054 data includes the target power value of the battery 40 for the next 30 minutes generated by the battery operation plan creation circuit 141, the capacity of the second DC / AC converter 408 (static inverter) within the power conversion device 41, and information related to the power distribution system 24. Additionally, the information related to the power distribution system 24 includes the upper and lower limits of the system frequency and the virtual synchronous generator control circuit 83 (…). Figure 11 The upper limit of the system frequency is the reference frequency Fref (e.g., 60Hz) + ΔFmax, and the lower limit of the system frequency is Fref - ΔFmax.

[0305] When information collection is completed in S0561, the reference ΔP / ΔF characteristic calculation circuit 131 calculates the reference ΔP / ΔF characteristic for each power conversion device 41 via S0562. The reference ΔP / ΔF characteristic will be explained below.

[0306] When generating control parameters for a power conversion device 41 equipped with virtual synchronous generator control, the reference ΔP / ΔF characteristic of the static inverter is first calculated. Furthermore, although Embodiment 1 describes the structure for generating control parameters for the power conversion device 41, the same method can be used to generate control parameters for power conversion devices with adjustable output, such as wind power generation devices, equipped with virtual synchronous generator control.

[0307] Specifically, the reference ΔP / ΔF characteristic calculation circuit 131 ( Figure 5 )like Figures 24A-24CAs shown, when the battery 40 discharges, half the capacity of the static inverter is used as the power target value so that the system frequency when the static inverter releases maximum power is equal to the lower limit frequency (in Figure 24A The system frequency is equal to the upper limit frequency when the differential frequency ΔF = -ΔFmax and the discharge power of the static inverter is zero. Figure 24A The baseline ΔP / ΔF characteristic is determined by the method of ΔF = ΔFmax. In addition, the power target value is positive during discharge and negative during charging.

[0308] Similarly, when the battery is charging at 40%, half the capacity of the static inverter is used as the power target value, and the system frequency at which the static inverter is charged to its maximum power is the upper limit frequency (in...). Figure 24B The system frequency is equal to the lower limit frequency when ΔF = ΔFmax and the charging power of the static inverter is zero (in the context of ΔF = ΔFmax). Figure 24B The reference ΔP / ΔF characteristic is determined by the method of ΔF = -ΔFmax. Hereinafter, the case of processing discharge is referred to as the discharge mode, and the case of processing charge is referred to as the charge mode.

[0309] Additionally, during the charging and discharging of battery 40 (hereinafter referred to as charging and discharging mode), the power target value of the static inverter is set to zero so that the system frequency at which the static inverter releases maximum power is equal to the lower limit frequency (in Figure 24C The value is ΔF = -ΔFmax), and the system frequency when the static inverter is charged to its maximum power is equal to the upper limit frequency (in...). Figure 24C The baseline ΔP / ΔF characteristic is determined by the method of ΔF = ΔFmax.

[0310] Figure 29 To illustrate the process for generating the baseline ΔP / ΔF characteristics ( Figure 28 The flowchart of S0562).

[0311] like Figure 29 As shown, when processing begins, the reference ΔP / ΔF characteristic calculation circuit 131 is used via S05621. Figure 5 The system collects capacity information (Cinv) of multiple static inverters that are objects for generating power target values ​​from the control circuit 136, and calculates the sum of the collected capacities Cinv of the multiple static inverters (=Σ(Cinv)).

[0312] When the sum of the capacities of the static inverters (Σ(Cinv)) is calculated, the reference ΔP / ΔF characteristic calculation circuit 131 collects system information (ΔFmax) via S05622. Next, via S05623, the reference ΔP / ΔF characteristic calculation circuit 131 uses Σ(Cinv) and ΔFmax to calculate the slope of the reference ΔP / ΔF characteristic.

[0313] Specifically, when the battery 40 is in charging or discharging mode, the reference ΔP / ΔF characteristic calculation circuit 131 sets the slope of the reference ΔP / ΔF characteristic to -ΔFmax / (Σ(Cinv)×0.5). On the other hand, when the battery 40 is in charging or discharging mode, the slope of the reference ΔP / ΔF characteristic is set to -ΔFmax / Σ(Cinv).

[0314] Next, via S0564, the reference ΔP / ΔF characteristic calculation circuit 131 generates the dead zone width during charge / discharge switching. Specifically, the reference ΔP / ΔF calculation circuit 131 calculates the sum of the power target values ​​of the multiple power conversion devices 41 output from the operation plan creation circuit 14, and uses the calculated sum of the power target values ​​and the reference ΔP / ΔF characteristic to calculate the frequency (switching frequency) ΔF0 at which charge / discharge is switched.

[0315] Additionally, the reference ΔP / ΔF characteristic for which mode to use (discharge mode or charge mode) and charge / discharge mode is determined by the battery operation plan creation circuit 141. Figure 4 Based on Figure 27 The determination is based on the charging and discharging power of the battery 40 in the demand plan created in S053. Specifically, when the absolute value of the determined charging and discharging power is less than a predetermined value, the charging and discharging mode is used. On the other hand, when the charging and discharging power is greater than or equal to the predetermined value, the discharging mode is used, and when the charging and discharging power is negative and its absolute value is greater than or equal to the predetermined value, the charging mode is used. In addition, the mode used is applied to all power conversion devices 41 connected to the power distribution system 24.

[0316] Back Figure 28 When the reference ΔP / ΔF characteristic is calculated in S0562, the ΔP / ΔF characteristic calculation circuit 132 is used through S0563. Figure 5 The ΔP / ΔF characteristic is generated. Specifically, the reference ΔP / ΔF characteristic calculation circuit 131 outputs the slope of the generated reference ΔP / ΔF characteristic and the switching frequency ΔF0 to the control circuit 136 and the ΔP / ΔF characteristic calculation circuit 132. The ΔP / ΔF characteristic calculation circuit 132 calculates the ΔP / ΔF characteristic based on the power target value provided by the control circuit 136. Figure 30 To illustrate the process for generating the ΔP / ΔF characteristics ( Figure 28 The flowchart of S0563). Figure 30 As shown, when processing begins, the ΔP / ΔF characteristic calculation circuit 132 collects the power target value Pref from the control circuit 136 via S05631. The ΔP / ΔF characteristic calculation circuit 132 then determines whether the collected power target value Pref exceeds the static inverter capacity Cinv via S05632.

[0317] For power conversion device 41 where the power target value Pref exceeds the static inverter capacity Cinv (no in S05632), the ΔP / ΔF characteristic calculation circuit 132 uses a limiter in S05633 to limit the power target value Pref to the static inverter capacity Cinv.

[0318] Through S05634, the ΔP / ΔF characteristic calculation circuit 132 uses the power target value Pref to calculate the slope of the ΔP / ΔF characteristic. Specifically, when the battery 40 is in discharge or charging mode, the slope of the ΔP / ΔF characteristic is -Pref / ΔF0. On the other hand, when the battery 40 is in charge / discharge mode, assuming the absorption of fluctuations in the generated electricity from large-scale solar power plants 26 or renewable energy sources such as wind power (power target value is zero), the ΔP / ΔF characteristic, which depends only on the capacity of the static inverter, is directly used. Figure 28 The baseline ΔP / ΔF characteristic is obtained in S0562. In Implementation 1, the case where the slope of the ΔP / ΔF characteristic, the switching frequency ΔF0, system information (±ΔFmax, etc.), and the power target value Pref are used as the information required to generate the control parameters for virtual synchronous generator control is explained.

[0319] When the ΔP / ΔF characteristics are generated, through Figure 28 S0564, the control parameter generation circuit 13 generates the dead zone width during charge / discharge switching. Figure 31 To illustrate the process of generating the dead zone width ( Figure 28 The flowchart of S0564). Figure 31 As shown, when the control parameter generation circuit 13 obtains the SOC information of the battery 40 through S05641 and the slope of the ΔP / ΔF characteristic through S05642, it calculates the maximum value (ΔFmax) of the differential frequency ΔF through S05643. Furthermore, in discharge mode, ΔPmax corresponds to the ΔP value in the ΔP / ΔF characteristic corresponding to -ΔFmax, and in charging mode, ΔPmax corresponds to the ΔP value corresponding to ΔFmax.

[0320] When ΔFmax is obtained in S05643, the control parameter generation circuit 13 confirms in S05644 whether the collected SOC of the battery 40 exceeds a predetermined upper limit value S1. In Embodiment 1, a lithium-ion battery is used as the battery 40. Lithium-ion batteries deteriorate rapidly due to overcharging or over-discharging, leading to failure. Therefore, in Embodiment 1, an upper limit value S1 and a lower limit value S2 are set for the SOC of the battery 40. For example, S1 is set to 80% and S2 is set to 10%. In charging mode, when the SOC exceeds S1 (80%), in order to reduce charging power, the dead zone width is narrowed compared to other batteries 40, thereby enabling a rapid transition to discharging mode. On the other hand, in discharging mode, when the SOC is less than S2 (10%), in order to reduce discharging power, the dead zone width is narrowed compared to other batteries 40, thereby enabling a rapid transition to charging mode.

[0321] When SOC > S1 (yes in S05644), the control parameter generation circuit 13 proceeds to S05645 to confirm whether the power target value is greater than 0, i.e., whether it is in discharge mode. When the power target value is greater than 0, i.e., in discharge mode (yes in S05645), the control parameter generation circuit 13 sets the dead zone width to ΔFmax × 0.1 via S05646. On the other hand, when the power target value is less than 0, i.e., in charging mode (no in S05645), the control parameter generation circuit 13 sets the dead zone width to ΔFmax × 0.05 via S05647.

[0322] When SOC ≤ S1 (No in S05644), the control parameter generation circuit 13 checks whether SOC is less than the lower limit S2 (10%) via S05648. When SOC < S2 (Yes in S05648), the control parameter generation circuit 13 proceeds to S05649 to check whether the power target value is less than 0, i.e., whether it is in charging mode. When the power target value is less than 0, i.e., in charging mode (Yes in S05649), the control parameter generation circuit 13 sets the dead zone width to ΔFmax × 0.1 via S05650. On the other hand, when the power target value is 0 or above, i.e., in discharging mode (No in S05649), the control parameter generation circuit 13 sets the dead zone width to ΔFmax × 0.05 via S05651.

[0323] Alternatively, for simplified implementation, a structure can be adopted in which the dead zone width is set to approximately 5% of ΔFmax regardless of the SOC. Alternatively, the dead zone width can be varied according to the SOC of each battery 40 or the inverter capacity of the corresponding power conversion device 41.

[0324] Back Figure 27As the information required for generating control parameters for the virtual synchronous generator control, when the generation of the dead zone width during charge-discharge switching (S0564) ends, the control parameter generation circuit 13 returns to S055 and checks whether the calculation of the information required for generating control parameters has been completed for all power conversion devices 41 corresponding to all batteries 40 connected to the power distribution system 24. If the calculation of this information for all power conversion devices 41 has not been completed (No in S055), the information required for generating control parameters for the next power conversion device 41 is calculated. When the calculation of this information for all power conversion devices 41 is completed (Yes in S055), the control parameter generation circuit 13 ends the process of creating the operation plan for the batteries 40. Figure 26 (S05).

[0325] Additionally, regarding generation Figure 29 The processing of the slope of the reference ΔP / ΔF characteristic and the switching frequency ΔF0 shown can also be performed on the initial power conversion device 41 when the control parameters of each power conversion device 41 are changed, while the other power conversion devices 41 use the calculated results as is, until the generation of the slope, etc., for the final power conversion device 41 is completed.

[0326] When passing Figure 26 When the S05 operation plan creation process of battery 40 is completed, the battery operation plan creation circuit 141 ( Figure 4 The created operation plan (power target value) will be notified to the first management circuit 145 via the second management circuit 146. Figure 4 When the first management circuit 145 receives the operation plan, it stores the received operation plan in its memory and notifies the data transmission generation circuit 15. Figure 3 The control parameter generation circuit 13 notifies the data transmission generation circuit 15 of the information required to generate the control parameters for the virtual synchronous generator control.

[0327] When the data generation circuit 15 obtains the operation plan (power target value) and the information required to generate control parameters (including dead zone width information), it processes them into a transmission format and outputs them to the communication circuit 11. Figure 3 When the communication circuit 11 receives the transmission data from the transmission data generation circuit 15, it transmits the transmission data to the corresponding power conversion device 41 via the communication line 25.

[0328] exist Figure 26In step S10, after sending the operation plan and generating the control parameters to all power conversion devices 41, step S11 checks whether to stop CEMS 31. If CEMS 31 is stopped (yes in S11), the process ends. On the other hand, if CEMS 31 is not stopped (no in S11), the process returns to step S01.

[0329] In contrast, when Figure 26 If no operation plan (power supply plan) is received from DSO 21 in S04 (no in S04), CEMS 31 proceeds to S06 to check if the time for collecting various measurement data has arrived. In Embodiment 1, as described above, CEMS 31 collects measurement data in 5-minute cycles. If the time for collecting measurement data has not arrived (no in S06), processing returns to S01. On the other hand, if the time for collecting measurement data has arrived (yes in S06), CEMS 31 collects measurement data in S07. In Embodiment 1, CEMS 31 collects 5 minutes of charge / discharge capacity, current charge / discharge capacity, and SOC information of the battery 40 from each power conversion device 41a-41c as measurement data.

[0330] When measurement data is collected in S07, CEMS 31 confirms in S08 whether the operation plan of battery 40 needs to be revised. In S07, CEMS 31 compares the current charge / discharge power with the operation plan (power target value) for each of the plurality of batteries 40. Specifically, CEMS 31 confirms whether the power difference between the current charge / discharge power and the power target value exceeds a predetermined range, and whether the SOC of battery 40 exceeds a predetermined allowable range (e.g., 5% to 90%). When the power difference of any one of the plurality of batteries 40 exceeds the predetermined range, and / or the SOC exceeds the allowable range, CEMS 31 re-examines the operation plan of all batteries 40. Alternatively, the operation plan of batteries 40 whose power difference exceeds the predetermined range and / or whose SOC exceeds the allowable range may also be re-examined.

[0331] CEMS 31 determines whether the operation plan of battery 40 needs to be modified according to the above-mentioned criteria. If it is determined that the operation plan of battery 40 does not need to be modified (No in S08), it returns to S01 and continues processing. On the other hand, if it is determined that the operation plan of battery 40 needs to be modified (Yes in S08), CEMS 31 proceeds to S09 and modifies the operation plan of all batteries 40.

[0332] Figure 32 To illustrate the processing of the modified operation plan of the storage battery 40 ( Figure 26 The flowchart of S09). Figure 32The processing shown is created by the operation plan creation circuit 14 within CEMS 31. Figure 3 ) is executed.

[0333] like Figure 32 As shown, when processing begins, via S091, the second management circuit 146 ( Figure 4 ) Battery operation plan correction circuit 144 ( Figure 4 It instructs to revise the operation plan and forwards the charging and discharging power and SOC information collected from each power conversion device 41.

[0334] In S092, the second management circuit 146 also stores the output of the battery operation plan correction circuit 144 in the first management circuit 145. Figure 4 The operating plan (power target value) of the battery 40 and the capacity of the static inverter of the power conversion device 41 stored in the storage circuit 12.

[0335] The battery operation plan correction circuit 144 re-examines the operation plan of the battery 40 based on information provided from the second management circuit 146. For example, it assumes that the discharge power of the power conversion device 41 becomes twice the target power value because either the predicted power generation of the large solar power plant 26 or the predicted power consumption of each user deviates from the actual value.

[0336] In this scenario, it is assumed that the system frequency has dropped to near the lower limit (Fref - ΔFmax). When there is insufficient power, the system frequency may drop to the lower limit, making it impossible to supply power from the power conversion device 41.

[0337] In this embodiment 1, when the ratio of the target power value to the charge / discharge power is not within a predetermined range, the battery operation plan correction circuit 144 corrects the operation plan (target power value) of the battery 40 based on measurement data collected at 5-minute intervals. Specifically, the battery operation plan correction circuit 144 corrects the operation plan of the battery 40 based on the current charge / discharge power and SOC information.

[0338] The reason for using SOC in the modification of the battery 40's operation plan is that when using a lithium-ion battery as the battery 40, the battery 40 may sometimes fail or deteriorate rapidly due to overcharging or over-discharging. Therefore, under normal battery control, when the SOC exceeds, for example, 90%, the battery charging mode is switched from constant current charging mode to constant voltage charging mode. In constant voltage charging mode, because a large charging power cannot be obtained, the power target value needs to be set small in the virtual synchronous generator control. Similarly, since the degradation of the battery 40 is also aggravated during over-discharging, the discharge power needs to be reduced when the SOC drops below, for example, 5%. Therefore, SOC is used in the creation and modification of the battery 40's operation plan.

[0339] Furthermore, while lead-acid batteries are tolerant of overcharging when used as the storage battery 40, they tend to deteriorate more rapidly due to over-discharge. Therefore, when using lead-acid batteries, it is necessary to reduce the discharge power at, for example, when the State of Charge (SOC) drops below 20%. As described above, the SOC is used to adjust the power target value in order to suppress the accelerated deterioration of the battery in use.

[0340] In S093, with Figure 27 Similarly, in S054, based on the current charging / discharging power of each power conversion device 41 and the SOC information of the battery 40, the charging / discharging power of each battery 40 is allocated proportionally. Furthermore, although a power target value is used in the creation of the operation plan (S05), the measured charging / discharging power is used as the power target value to revise the operation plan in the revision of the operation plan (S09). Therefore, although the explanation is omitted, in the processing of S095 (generating the information required for generating control parameters) described later, although... Figure 27 The S056 process is the same, but the parameters used are different. Figure 27 In S056, circuit 14 (created by the operation plan) is used. Figure 3 The generated power target value, in contrast, Figure 32 In S095, the measured charge and discharge power values ​​are used instead of the target power values. In addition, based on the data collected in 5-minute cycles (measured values), the operation plan creation circuit 14 generates an operation plan (target power value) again. The same effect can be achieved by using the generated operation plan to revise the operation plan.

[0341] When the proportional distribution of charging and discharging power to each battery 40 is completed in S093, the parameter generation circuit 13 is controlled in S094. Figure 3The system confirms whether the calculation of the information required to generate control parameters for all batteries 40 has been completed. If the calculation of the information required to generate control parameters for all batteries 40 has been completed (yes in S094), the battery operation plan correction circuit 144 ends the correction process of the operation plan for the batteries 40. On the other hand, if the correction of the operation plan for all batteries 40 has not been completed (no in S094), the control parameter generation circuit 13 generates the information required to generate control parameters for the virtual synchronous generator control in S095. Furthermore, the method for generating the information required to generate control parameters for the virtual synchronous generator control differs from the method used in the battery operation plan creation process (except for the different parameters used above). Figure 27 The generation method used in S056 is the same, so the explanation is omitted.

[0342] When the information required for generating control parameters is generated in S095, the circuit returns to S094, where the control parameter generation circuit 13 confirms whether the calculation of the information required for generating control parameters for all power conversion devices 41 has been completed. If the calculation of the information required for generating control parameters for all power conversion devices 41 has not been completed (not in S094), the control parameter generation circuit 13 generates the information required for generating control parameters for the next power conversion device 41 in S095.

[0343] On the other hand, when the calculation of the information required to generate the control parameters of all power conversion devices 41 is completed (yes in S094), the battery operation plan correction circuit 144 ends the correction process of the operation plan of the battery 40 in S096.

[0344] Back Figure 26 When the operation plan of the battery 40 is modified in S09, the battery operation plan creation circuit 141 notifies the first management circuit 145 of the modified operation plan (power target value) via the second management circuit 146, just as when the operation plan is created.

[0345] When the battery operation plan creation circuit 141 obtains the operation plan of the battery 40, the first management circuit 145 stores the obtained operation plan in a memory (not shown) and notifies the data transmission generation circuit 15. Similarly, the control parameter generation circuit 13 notifies the data transmission generation circuit 15 of the information required for generating the battery 40's operation plan (power target value) and control parameters (including dead zone width information).

[0346] When the data generation circuit 15 receives the information required for generating the operation plan and control parameters of the storage battery 40, it processes the data into a format for transmission and outputs it to the communication circuit 11.

[0347] When communication circuit 11 receives transmission data from transmission data generation circuit 15, it transmits the transmission data to the corresponding power conversion device 41 via communication line 25. Figure 26 (S10).

[0348] When in Figure 26 In S10, when the operation plan for the battery 40 is sent to all power conversion devices 41, S11 confirms whether to stop CEMS 31. If CEMS 31 is stopped (yes in S11), the process ends. On the other hand, if CEMS 31 is not stopped, the process returns to S01 to continue.

[0349] As described above, in Embodiment 1, when creating an operation plan (power target value) for the battery 40 for multiple power conversion devices 41, information required for the control parameters of the virtual synchronous generator control equipped on the static inverter is generated based on the battery capacity and SOC of the battery 40, the capacity of the static inverter of each power conversion device 41, and the power target value. In the above structure, using information about the battery 40 and the power conversion device 41, the switching frequency ΔF0 at which the charging and discharging of each battery 40 is switched is calculated, and the slope of the ΔP / ΔF characteristic is generated based on the calculated switching frequency ΔF0. Then, based on the SOC and power target value of each battery 40, the dead zone width given to the ΔP / ΔF characteristic of each power conversion device 41 is calculated.

[0350] By employing this structure, when multiple power conversion devices 41 are connected to the power distribution system 24, the switching frequency ΔF0 in the drooping characteristic (ΔP / ΔF characteristic) assigned to each power conversion device 41 by the virtual synchronous generator control can have a dead zone. As a result, it prevents situations where, due to sensor errors in the voltmeters and ammeters, even if the generated power of the large solar power plant 26 is balanced with the power consumed by the load, [further issues may arise]. Figure 22 As shown in (B), the discharge power of battery 40b is used to charge battery 40a. This suppresses unnecessary power exchange between batteries 40a and 40b, thus preventing power loss caused by charging and discharging and accelerating the deterioration of battery 40.

[0351] Furthermore, although Embodiment 1 described a structure using the capacity and power target value of the static inverter when generating information for the control parameters used to control the virtual synchronous generator for the static inverter within the power conversion device 41, it is not limited to this. For example, when the battery capacity of battery 40a is twice the capacity of the static inverter of power conversion device 41a, and the battery capacity of battery 40b is three times the capacity of the static inverter of power conversion device 41b, and the ratio of static inverter capacity to battery capacity differs among multiple batteries 40, a structure that considers this capacity ratio to generate the operation plan (power target value) can also be adopted. Alternatively, a structure that considers the aforementioned capacity ratio when generating control parameters for virtual synchronous generator control can also achieve the same effect.

[0352] (Operation of power conversion device 27 and power conversion device 41)

[0353] Next use Figures 6 to 37 This explains the operation of the power conversion device 27 used in large solar power plants and the power conversion device 41 used in storage batteries.

[0354] [Operation of power conversion device 27]

[0355] use Figure 6 This explains the operation of the power conversion device 27 used in large solar power plants.

[0356] When the large solar power plant 26 starts generating electricity, the DC voltage input from the large solar power plant 26 to the first DC / DC converter 203 in the power conversion device 27 rises. The first control circuit 204 monitors the DC voltage measured by the voltmeter 201. When the DC voltage exceeds a predetermined value, the first control circuit 204 switches the power conversion device 27 from standby mode to normal operation. During normal operation, the second control circuit 209 within the power conversion device 27 controls the first DC / AC converter 208. The control of the power conversion device 27 during normal operation is described below.

[0357] like Figure 6 As shown, the first control circuit 204 confirms whether the large solar power plant 26 is generating electricity. Specifically, the first control circuit 204 confirms whether the output voltage of the large solar power plant 26, as measured by the voltmeter 201, exceeds a predetermined voltage. When the output voltage exceeds the predetermined voltage, the first control circuit 204 notifies the second control circuit 209 that the large solar power plant 26 is capable of generating electricity.

[0358] When the second control circuit 209 receives a notification from the first control circuit 204, it confirms whether power is being supplied from the substation 20 to the power distribution system 24 (whether the power distribution system 24 is not out of power) based on the AC voltage of the power distribution system 24 measured by the voltmeter 210.

[0359] When it is confirmed that the AC voltage measured by voltmeter 210 is above the predetermined voltage and the power distribution system 24 is not de-energized, the second control circuit 209 starts the first DC / AC converter 208 and instructs the first control circuit 204 to start generating electricity from the large solar power plant 26.

[0360] Furthermore, in Embodiment 1, the case where the DC bus voltage of the DC bus 205 is managed by the first DC / AC converter 208 during normal operation will be described. Additionally, in Embodiment 1, the power supplied from the power conversion device 27 to the power distribution system 24 is managed by current control performed by the first DC / AC converter 208, thereby enabling the distributed power management device to operate as a whole.

[0361] When the large solar power plant 26 is instructed to start generating electricity via the second control circuit 209, the fifth control circuit 54 of the first control circuit 204 ( Figure 8 ) Indicates MPPT control circuit 51 ( Figure 8 To begin maximum power point tracking control of the large solar power plant 26.

[0362] A brief explanation of maximum power point tracking (MPPT) control is provided. MPPT control manages whether the previous power command value is greater than or less than the power command value from the period before last. Then, the measured power output of the large solar power plant 26 is compared with the previously measured power output. If the power output increases, the command value is changed to the same direction as before (either increasing or decreasing).

[0363] Specifically, when the measured power output of the large solar power plant 26 is higher than the previously measured power output, the command value is increased if the previous command value was greater than the command value two years prior. Conversely, the command value is decreased if the previous command value was less than the command value two years prior. Conversely, when the measured power output of the large solar power plant 26 is lower than the previously measured power output, the command value is decreased if the previous command value was greater than the command value two years prior. Conversely, the command value is increased if the previous command value was less than the command value two years prior. By controlling the command value in this way, the large solar power plant 26 is controlled to maximize its power output.

[0364] The first DC / DC converter 203 operates its built-in boost circuit according to the command value output from the first control circuit 204, thereby converting the first DC voltage output from the large solar power plant 26 into a second DC voltage (the DC bus voltage of the DC bus 205) and outputting it.

[0365] When the power generated by the large solar power plant 26 is supplied from the first DC / DC converter 203, the second control circuit 209 controls the first DC / AC converter 208, thereby outputting (regenerating) the generated power from the large solar power plant 26 to the power distribution system 24. Specifically, the DC bus voltage of the DC bus 205 is monitored, and when the DC bus voltage exceeds the control target value, the generated power is output synchronously with the AC voltage supplied from the power distribution system 24.

[0366] Next use Figure 9 This explains the operation of the second control circuit 209.

[0367] In the second control circuit 209, the phase detection circuit 61 detects the phase of the phase measured by the voltmeter 210 ( Figure 1 The zero-crossing point of the AC voltage waveform of the power distribution system 24 is measured.

[0368] The first sine wave generation circuit 62 generates a reference sine wave that is synchronized with the waveform of the AC voltage of the power distribution system 24, based on information representing the zero-crossing point detected by the phase detection circuit 61 and the waveform of the AC voltage measured by the voltmeter 210. The first sine wave generation circuit 62 outputs the generated reference sine wave to the multiplier 65.

[0369] Voltmeter 206 measures the voltage of DC bus 205 and outputs the measured value to subtractor 63 and sixth control circuit 67 within current control circuit 60. Furthermore, current control circuit 60 uses a control method (current control) that outputs power synchronously with the AC system voltage. This control method is the same as that used in ordinary photovoltaic power conversion devices installed in homes.

[0370] The sixth control circuit 67 stores the target voltage of the DC bus 205 and outputs the target voltage to the subtractor 63.

[0371] The current control circuit 60 controls the output current of the first DC / AC converter 208 in a manner that makes the DC bus voltage measured by the voltmeter 206 the target voltage. The output of the subtractor 63 is input to the first PI control circuit 64. The first PI control circuit 64 performs PI control in a manner that makes the output of the subtractor 63 zero. The output of the first PI control circuit 64 is input to the multiplier 65, and is converted into a current command value by multiplying it with a reference sine wave from the first sine wave generation circuit 62.

[0372] The current command value output from multiplier 65 is input to subtractor 66. Subtractor 66 calculates the deviation between the current command value and the AC current value of the power distribution system 24 measured by ammeter 211, and inputs the calculated deviation to the second PI control circuit 68.

[0373] The second PI control circuit 68 performs PI control in a manner that makes the deviation output from the subtractor 66 zero. The first PWM converter 69 performs PWM control on the output of the second PI control circuit 68, thereby generating the command value for the first DC / AC converter 208. The first DC / AC converter 208 outputs AC current according to the command value provided by the first PWM converter 69.

[0374] Additionally, when the AC voltage (AC effective voltage) measured by voltmeter 210 exceeds a predetermined voltage value, or when a request to suppress the power generation of the large solar power plant 26 is notified from CEMS 31, the fifth control circuit 54 within the first control circuit 204 ( Figure 8 The control of the large solar power plant 26 is switched from MPPT control to voltage control. Specifically, the fifth control circuit 54 controls the DC voltage output from the large solar power plant 26 so that the AC voltage (AC effective voltage) measured by voltmeter 210 falls within a predetermined voltage range. Alternatively, the fifth control circuit 54 controls the output voltage of the large solar power plant 26 so that the generated power of the large solar power plant 26 falls within the power range notified by CEMS 31.

[0375] Additionally, the first switching circuit 53 ( Figure 8 The switching is performed between the output of the MPPT control circuit 51 and the output of the voltage control circuit 52 according to the switching control signal provided by the 5th control circuit 54.

[0376] The sixth control circuit 67 collects measurement results of the DC bus 205 measured by voltmeter 206 and ammeter 207, measurement results of the power distribution system 24 measured by voltmeter 210 and ammeter 211, status information of the first DC / DC converter 203 output from the first control circuit 204, and notifies the CEMS 31 of the collected information via communication I / F 212.

[0377] In addition, the sixth control circuit 67 also notifies the CEMS 31 of the effective voltage of the power distribution system 24 measured by the effective voltage measurement unit (not shown) or the active and reactive power of the AC system measured by the active / reactive power measurement unit (not shown), and also notifies the fifth control circuit 54 of the measurement results such as the effective voltage and active power of the AC system.

[0378] As described above, when the effective value of the AC system voltage exceeds a predetermined value, the fifth control circuit 54 switches the control of the large solar power plant 26 from MPPT control to voltage control, thereby suppressing the rise of the AC system voltage.

[0379] [Operation of power conversion device 41]

[0380] Next use Figures 7 to 37 This explains the operation of the power conversion device 41 used for the storage battery.

[0381] In Embodiment 1, since a virtual synchronous generator control is provided in the power conversion device 41, the second DC / AC converter 408 operates as a voltage source by performing voltage control. That is, the third control circuit 404 controls the second DC / DC converter 403 to maintain a constant voltage on the DC bus 405. (The following uses...) Figure 10 This explains the operation of the third control circuit 404.

[0382] The voltage of DC bus 405 is measured by voltmeter 406. The measured value of voltmeter 406 is input to charging control circuit 71, discharging control circuit 72 and the seventh control circuit 74.

[0383] When the voltage of the DC bus 405 is greater than the target voltage output from the 7th control circuit 74, the charging control circuit 71 controls the charging power of the battery 40 to make the voltage of the DC bus 405 the target voltage. On the other hand, when the voltage of the DC bus 405 is less than the target voltage, the discharging control circuit 72 increases the discharging power of the battery 40.

[0384] Furthermore, the second switching circuit 73 switches between the output of the charging control circuit 71 and the output of the discharging control circuit 72. The seventh control circuit 74 outputs a switching control signal to the second switching circuit 73 based on the voltage value of the DC bus 405 measured by the voltmeter 406.

[0385] Next, the fourth control circuit 409 will be described. Figure 11 ) work. Figure 33 This is a flowchart illustrating the operation of the power conversion device 41. (For example...) Figure 33 As shown, when processing begins, the fourth control circuit 409 initializes various control parameters via S200. Next, via S201, the fourth control circuit 409 collects voltage values ​​measured by voltmeters 401, 406, and 410, current values ​​measured by ammeters 402, 407, and 411, and battery status information (SOC, etc.) of the battery 40. Furthermore, since the measurement value of voltmeter 410 is AC voltage, the eighth control circuit 87 (… Figure 11The effective value of the AC voltage is calculated in the control circuit 87 and used as the voltage value. Since the ammeter 411 measures the AC current, the effective value of the AC current is calculated in the control circuit 87 and used as the current value. The charging and discharging power calculation circuit (not shown) in the control circuit 74 calculates the charging and discharging power and the charging and discharging capacity of the battery based on the collected data.

[0386] The AC voltage of the power distribution system 24, measured by voltmeter 410, is input to the AC frequency detection circuit 81. Figure 11 Through S202, the AC frequency detection circuit 81 detects the zero-crossing point of the AC voltage waveform.

[0387] Figure 12 To show Figure 11 The block diagram shown illustrates the structure of the AC frequency detection circuit 81. Figure 12 As shown, the measured value from voltmeter 410 is input to phase detection circuit 810. Through... Figure 33 In step S202, the phase detection circuit 810 detects the zero-crossing point of the AC voltage. Furthermore, in embodiment 1, the zero-crossing point represents the point and time at which the waveform of the AC voltage measured by the voltmeter 410 switches from negative to positive. The phase detection circuit 810 outputs information indicating the detected zero-crossing point to the frequency detection circuit 811.

[0388] The frequency detection circuit 811 calculates the period of the AC voltage based on the time of the zero-crossing point previously detected by the phase detection circuit 810 and the time of the current zero-crossing point. Based on the calculated period, the frequency detection circuit 811 calculates the frequency of the AC voltage.

[0389] The second sine wave generation circuit 812 outputs zero-crossing information detected by the phase detection circuit 810 and frequency information of the AC voltage detected by the frequency detection circuit 811 as sine wave information. The zero-crossing information and frequency information are output to the inverter current control circuit 84, the inverter voltage control circuit 85, the virtual synchronous generator control circuit 83, the eighth control circuit 87, and the dead-time detection circuit 90.

[0390] Back Figure 33 When a zero-crossing is detected in S202 (yes in S202), the phase detection circuit 810 sets the zero-crossing detection flag via S203. After the processing of S203 ends, or when no zero-crossing is detected in S202 (no in S202), the fourth control circuit 409 controls the second DC / DC converter 403 via S220.

[0391] The following uses Figure 10 and Figure 34 This explains the control of the second DC / DC converter 403.

[0392] As described above, since the power conversion device 41 is equipped with virtual synchronous generator control, the second DC / AC converter 408 is controlled as a voltage source. That is, the second DC / AC converter 408 is voltage controlled. Therefore, the voltage of the DC bus 405 is managed by the second DC / AC converter 403. Figure 34 This is a flowchart illustrating the control processing details of the second DC / DC converter 403.

[0393] In S2201, the third control circuit 404 calculates the charge / discharge power value based on the voltage of the DC bus 405 detected by the voltmeter 406 and the current detected by the ammeter 407. In S2202, the seventh control circuit 74 confirms whether to proceed from the eighth control circuit 87 ( Figure 11 The dead-zone flag (whether the dead-zone flag is set) is notified. When the dead-zone flag is not set (no in S2202), the third control circuit 404 confirms in S2203 whether the charge / discharge power value of the battery 40 obtained in S2201 is within a predetermined range. The predetermined range is set to a range where the charge / discharge power value is approximately zero. Furthermore, the charge / discharge power value can also be calculated by multiplying the outputs of the voltmeter 401 and the ammeter 402.

[0394] When the charging / discharging power value is outside the predetermined range, i.e., when the charging / discharging power value is not almost zero (no in S2203), the third control circuit 404 generates a normal charging / discharging command value. On the other hand, when the charging / discharging power value is within the predetermined range (yes in S2203), the third control circuit 404 determines in S2205 that a dead zone period (the start of the dead zone period) has been detected, and notifies the eighth control circuit 87 of this situation. Figure 11 ).

[0395] When the dead-time flag is set (yes in S2202), or when a dead-time period is detected in S2205, the 7th control circuit 74 fixes the current operating mode via S2206. Specifically, if the current operating mode is charging mode, the charging mode is maintained; if it is discharging mode, the discharging mode is maintained. Next, via S2207, the 7th control circuit 74 sets the charging / discharging power command value to zero and outputs it to the 2nd DC / DC converter 403, ending the control processing of the 2nd DC / DC converter 403.

[0396] Back Figure 33 Through S204, the fourth control circuit 409 controls the second DC / AC converter 408. The following uses... Figure 11 and Figure 35 This explains the control of the second DC / AC converter 408.

[0397] As described above, since the power conversion device 41 is equipped with virtual synchronous generator control, the second DC / AC converter 408 is controlled as a voltage source. That is, the second DC / AC converter 408 is voltage-controlled. Therefore, when the power supplied to the power distribution system 24 is insufficient, the second DC / AC converter 408 is controlled to increase the output power. On the other hand, when the power supplied to the power distribution system 24 is excessive, the second DC / AC converter 408 is controlled to reduce the output power.

[0398] Figure 35 This is a flowchart illustrating the control processing details of the second DC / AC converter 408.

[0399] like Figure 35 As shown, when the effective power calculation circuit 82 of S2021 is used... Figure 11 When calculating the power value based on the measurements of voltmeter 410 and ammeter 411, the calculated power value is integrated in step S2022. When the zero-crossing detection flag is set (yes in step S2023), the effective power calculation circuit 82 proceeds to step S2024, stores the integrated value of the effective power value for one cycle of AC voltage in the storage circuit (not shown) of the 8th control circuit 87, and initializes the integrated value to zero in step S2025.

[0400] When the processing in S2025 ends, or if the zero-crossing detection flag is not set (not in S2023), the dead-time detection circuit 90 detects the dead-time period in S2026. Specifically, the dead-time detection circuit 90 detects the dead-time period based on the dead-time detection information output from the 7th control circuit 74 and the system frequency information detected by the AC frequency detection circuit 81. Furthermore, the dead-time detection information includes information that the charging / discharging power of the battery 40 is almost zero.

[0401] Back Figure 35 When a dead zone is detected in S2026, the 8th control circuit 87 checks in S2027 whether the dead zone flag is set. If the dead zone flag is not set (not in S2027), the 8th control circuit 87 checks in S2028 whether dead zone detection information has been notified from the 7th control circuit 74. In Embodiment 1, the start of the dead zone is not based on the detection result of the system frequency, but on whether the absolute value of the charge / discharge power of the battery 40 is below a predetermined value. Although the start of the dead zone can be detected based on the detection result of the system frequency output by the AC frequency detection circuit 81, in Embodiment 1, in order to avoid the transfer of charge / discharge between multiple batteries 40, the start of the dead zone is detected based on the charge / discharge power of the battery 40. With this configuration, even if the voltmeter and ammeter have sensor errors, the switching of charge / discharge can be reliably detected.

[0402] When dead-time detection information is received from the 7th control circuit 74 in S2028 (yes in S2028), the dead-time detection circuit 90 sets the dead-time flag in S2029. Conversely, when the dead-time flag is set (yes in S2027), the 8th control circuit 87 checks whether the end of the dead-time period has been detected in S2031. When the end of the dead-time period is detected (yes in S2031), the 8th control circuit 87 resets the dead-time flag in S2032. When no dead-time detection information is received from the 7th control circuit 74 (no in S2028), no end of the dead-time period is detected (no in S2031), or the dead-time flag is set (S2029) or reset (S2032), the 4th control circuit 409 generates control command values ​​for controlling the 2nd DC / AC converter 408.

[0403] Next, refer to Figure 13 This explains the operation of the inverter voltage control circuit 85.

[0404] like Figure 13 As shown, the inverter voltage control circuit 85 generates control command values ​​for controlling the second DC / AC converter 408 based on the frequency and phase information output from the virtual synchronous generator control circuit 83 (input via the second sine wave generation circuit 812) and the amplitude information of the AC system voltage input from the eighth control circuit 87 via the second sine wave generation circuit 812.

[0405] Specifically, the sinusoidal information (frequency, phase, and amplitude information, as well as the frequency and phase information calculated by the virtual synchronous generator control circuit 83) from the AC frequency detection circuit 81 is input to the third sinusoidal generation circuit 851. Based on the input information, the third sinusoidal generation circuit 851 generates a target value for the AC system voltage output from the second DC / AC converter 408.

[0406] Subtractor 852 subtracts the voltage measured by voltmeter 410 from the output of the third sine wave generation circuit 851 and outputs the subtraction result to the third PI control circuit 853.

[0407] The third PI control circuit 853 performs PI control to make the input subtraction result zero, thereby generating a voltage command value, and outputs the generated voltage command value to the first current limiting circuit 855.

[0408] The first current limiting circuit 855 limits the voltage command value provided by the third PI control circuit 853 based on the measurement result of the ammeter 411 input via the eighth control circuit 87. For example, consider a case where the power target value notified from the CEMS 31 is 90% of the inverter capacity and the load power consumption increases. In this case, in the ΔP / ΔF characteristic described in Embodiment 1, power exceeding the inverter capacity within the power conversion device 41 is required before the system voltage frequency deviation (differential frequency ΔF) reaches -ΔFmax. Therefore, it is necessary to limit the output power (output current) of the power conversion device 41 to prevent it from exceeding the inverter capacity. Therefore, in Embodiment 1, when current flows exceeding the current capacity of the second DC / AC converter 408, control is performed to apply a current limit so that the current flowing through the second DC / AC converter 408 is a predetermined current value (e.g., the current capacity of the second DC / AC converter 408).

[0409] Specifically, the first current limiting circuit 855 monitors the current flowing through the second DC / AC converter 408 and controls (limits) the current value to prevent it from exceeding the current capacity of the second DC / AC converter 408. The output of the first current limiting circuit 855 is input to the second PWM converter 854. Furthermore, the control parameters (control gain and integral time) of the third PI control circuit 853 and the first current limiting circuit 855 are output from the eighth control circuit 87.

[0410] The second PWM converter 854 uses the voltage command value output from the first current limiting circuit 855 to perform PWM control, thereby generating a control command value. The second PWM converter 854 outputs the generated control command value to the second DC / AC converter 408.

[0411] Back Figure 33 When the control command value for the second DC / AC converter 408 is generated in S204, the virtual synchronous generator control circuit 83 executes virtual synchronous generator control in S205. In Embodiment 1, one cycle of the AC voltage is used as the control cycle. Furthermore, the control cycle can also be set to an integer multiple of one cycle of the AC voltage, or a predetermined cycle such as one second.

[0412] Figure 14 A block diagram illustrating the structure of the virtual synchronous generator control circuit 83 is provided. If the control timing is determined to be reached, then the 8th control circuit 87 (… Figure 11 The virtual synchronous generator control circuit 83 is instructed to generate information related to the frequency and phase used in voltage control. In Embodiment 1, the third sine wave generation circuit 851 within the inverter voltage control circuit 85 is updated at the zero-crossing point. Figure 13The frequency and phase of the generated sine wave. Therefore, in Embodiment 1, the control period is the period of the zero-crossing point detected by the AC frequency detection circuit 81.

[0413] like Figure 14 As shown, in the virtual synchronous generator control circuit 83, the subtractor 832 is derived from the AC frequency detection circuit 81 ( Figure 11 The reference frequency Fref (e.g., 60Hz) input from the 8th control circuit 87 is subtracted from the measured value of the frequency of the input system voltage, and the subtraction result is output to the speed controller control circuit 833. Figure 15 To show Figure 14 The block diagram showing the detailed structure of the speed controller control circuit 833 is shown.

[0414] like Figure 15 As shown, in the speed controller control circuit 833, the multiplier 91 converts the subtractor 832 ( Figure 14 The output of ) is multiplied by the control parameter (-1 / Kgd) notified from the 8th control circuit 87. The multiplier 91 inputs the multiplication result into the first-order lag system model 92.

[0415] In addition, the speed regulation rate Kgd and the speed governor time constant Tg used in the speed governor control circuit 833 are set to a register (not shown) via the 8th control circuit 87 from the information notified by CEMS 31 and the information generated by the control parameter generation circuit 88.

[0416] As described above, the first-order lag system model 92 uses the time constant Tg notified from the 8th control circuit 87 to perform the calculation of the first-order lag system (l / (l+s×Tg)) and outputs the calculation result to the limiter circuit 93.

[0417] Limiter circuit 93 imposes a limit on the input data. Specifically, limiter circuit 93 limits the output power of the second DC / AC converter 408 to prevent it from exceeding the power capacity of the second DC / AC converter 408.

[0418] Back Figure 14 Adder 835 adds the output of speed controller control circuit 833 to the power target value Pref output from control circuit 87. Furthermore, the power target value Pref is received from CEMS 31 and output from control circuit 87.

[0419] Subtractor 836 subtracts from the output of adder 835 the value obtained from effective power calculation circuit 82. Figure 11 The effective power output is subtracted and the result is output to the mass system operation circuit 837. Figure 16 To show Figure 14The block diagram showing the detailed structure of the particle system operational circuit 837 is shown. Figure 16 As shown, subtractor 101 is derived from subtractor 836 ( Figure 14 The output of multiplier 103 is subtracted from the output of ) and the subtracted value is output to integrator 102.

[0420] Integrator 102 divides the subtraction result of subtractor 101 by the inertia constant M output from control circuit 87, and integrates the division result. The output Δω of integrator 102 is equivalent to the difference between the angular velocity (2×π×60Hz) of the AC voltage frequency and the integrator 102. The output Δω of integrator 102 is input to multiplier 103 and divider 104.

[0421] Multiplier 103 multiplies the output Δω of integrator 102 with the braking coefficient Dg provided from the 8th control circuit 87, and outputs the multiplication result to subtractor 101.

[0422] Divider 104 divides the output Δω of integrator 102 by 2×π, thereby transforming Δω into the difference Δf between it and the reference frequency Fref (60Hz). Adder 105 adds the output Δf of divider 104 to the reference frequency Fref (60Hz), thereby generating the voltage in inverter voltage control circuit 85 (…). Figure 11 The frequency (Fref+Δf) used for voltage control in )

[0423] In addition, the inertial constant M and braking coefficient Dg used in the mass system operation circuit 837 will be set in a register (not shown) via the 8th control circuit 87 using the results generated by the control parameter generation circuit 88 using the information required to generate the virtual synchronous generator control parameters generated and notified by the CEMS 31. The results set in the register will be used.

[0424] The frequency information (Fref+Δf) output from adder 105 is input to phase calculation circuit 106. The operation of phase calculation circuit 106 is described below.

[0425] In implementation 1, from adder 105 ( Figure 16 The frequency information output is integrated by the phase calculation circuit 106 and output as the phase information when the inverter voltage control circuit 85 performs voltage control.

[0426] From the particle system operation circuit 837 ( Figure 16 The phase and frequency information output are processed by the second sine wave generation circuit 812 within the AC frequency detection circuit 81. Figure 12 The third sine wave generation circuit 851 (input into the inverter voltage control circuit 85) is input to the inverter voltage control circuit 85. Figure 13The third sine wave generation circuit 851 generates a target value of the AC voltage output from the power conversion device 41 based on the input information.

[0427] Furthermore, in Embodiment 1, the speed controller control circuit 833 and the mass system operation circuit 837 operate normally even when the dead zone flag is set.

[0428] Back Figure 33 When the virtual synchronous generator control process ends in S205, the fourth control circuit 409 checks in S206 whether a transmission request for measurement data has been received from CEMS 31. If a transmission request is received from CEMS 31 (yes in S206), the eighth control circuit 87 (…) checks in S207. Figure 11 The measurement data will be transmitted via communication I / F 412 ( Figure 7 Notification to CEMS 31.

[0429] On the other hand, when measurement data is notified in S207, or when there is no transmission request from CEMS 31 (no in S206), the 8th control circuit 87 proceeds to S208 to confirm whether control information has been received from CEMS 31.

[0430] When control information is received from CEMS 31 (yes in S208), the 8th control circuit 87 sets the control information reception flag in S209. When the process in S209 ends, or when no control information is received from CEMS 31 (no in S208), the 8th control circuit 87 checks whether the zero-crossing detection flag is set in S210. When the zero-crossing detection flag is not set (no in S210), the process returns to S201.

[0431] On the other hand, when the zero-crossing detection flag is set (yes in S210), the second sine wave generation circuit 812 (…) is activated via S211. Figure 12 The system acquires information on the frequency and phase of the system voltage and resets the zero-crossing detection flag in S212.

[0432] When the zero-crossing detection flag is reset in S212, the second sine wave generation circuit 812 updates the information of the frequency and phase of the system voltage (in Embodiment 1, the zero-crossing time information) to the information taken in S211 via S213.

[0433] When the processing in S213 is completed, the 8th control circuit 87 checks in S214 whether control information has been received from CEMS 31 (whether the control information receiving flag is set). If the receiving flag is not set (no in S214), the processing returns to S201.

[0434] On the other hand, when the receiving flag is set (yes in S214), the 8th control circuit 87 replaces the frequency target value (reference frequency Fref) and the power target value Pref with the received data via S215.

[0435] Through S216, the control parameter generation circuit 88 generates the control parameters (speed regulation rate Kgd, braking coefficient Dg, and inertia constant M) for the virtual synchronous generator control. Figure 36 To illustrate the process of generating control parameters ( Figure 33 The flowchart of S216 is shown. In Embodiment 1, the case where the ΔP / ΔF characteristics are input from the CEMS 31 as the information required to generate the control parameters for the virtual synchronous generator control is described. The control parameter generation circuit 88 uses system information (reference frequency Fref, power target value Pref, ΔFmax information) and inverter capacity Cinv in addition to the ΔP / ΔF characteristics to generate the control parameters.

[0436] like Figure 36 As shown, when the control parameters are generated, the control parameter generation circuit 88 sets the speed regulation rate Kgd and the braking coefficient Dg to predetermined initial values ​​through S2161, thereby initializing the speed regulation rate Kgd and the braking coefficient Dg.

[0437] When the speed regulation rate Kgd and braking coefficient Dg are initialized in S2161, the control parameter generation circuit 88 proceeds to S2162 and calculates the slope of the ΔP / ΔF characteristic using the speed regulation rate Kgd and braking coefficient Dg. In Implementation 1, the control parameter generation circuit 88 ( Figure 11 ) Install simulated virtual synchronous generator control circuit 83 ( Figure 11 This section describes the operation of a virtual synchronous generator model and the use of this model to generate control parameters.

[0438] Furthermore, the method for generating control parameters is not limited to this; it can also be configured, for example, by... Figure 18 The relationship between the speed regulation rate Kgd and the system frequency is pre-stored as tabular data corresponding to each braking coefficient Dg, and... Figure 19 The relationship between the braking coefficient Dg and the system frequency is pre-stored as tabular data corresponding to each speed regulation rate Kgd. These tabular data are used to determine the appropriate speed regulation rate Kgd and braking coefficient Dg.

[0439] In implementation method 1, a virtual synchronous generator model is used... Figures 14-16The results obtained by mathematically modeling the block diagram shown are not limited to this. For example, a virtual synchronous generator control circuit 83 can be generated based on the transfer function of the governor control unit shown in equation (1) and the oscillation equation shown in equation (2). Figure 11 The transfer function is generated, and the structure of control parameters is generated based on the generated transfer function.

[0440] In S2162, the speed regulation rate Kgd and braking coefficient Dg are set for the virtual synchronous generator model, thereby calculating the load fluctuation from the mass system operation circuit 837 when the input load fluctuates by, for example, about 25% of the inverter capacity. Figure 14 The system frequency output is calculated. The reference frequency Fref is subtracted from this result to calculate the differential frequency ΔF. Then, the calculated differential frequency ΔF is divided by the load fluctuation (e.g., inverter capacity × 0.25) to calculate the slope of the ΔP / ΔF characteristic.

[0441] When the slope of the ΔP / ΔF characteristic is calculated in S2162, the control parameter generation circuit 88, via S2163, compares the calculated slope of the ΔP / ΔF characteristic with the slope obtained through... Figure 28 S0563 ( Figure 30 The slopes of the generated ΔP / ΔF characteristics are compared. Specifically, the control parameter generation circuit 88 confirms whether the deviation between the slopes of these two ΔP / ΔF characteristics falls within a predetermined allowable range.

[0442] When the slope deviation falls within the above-mentioned allowable range, the control parameter generation circuit 88 determines that the slopes of the two ΔP / ΔF characteristics are consistent (yes in S2163) and proceeds to S2169.

[0443] On the other hand, when the slope deviation does not fall within the aforementioned allowable range, the control parameter generation circuit 88 determines that the slopes of the two ΔP / ΔF characteristics are inconsistent (no in S2163). In this case, the control parameter generation circuit 88 proceeds to S2164 and changes the braking coefficient Dg. In Embodiment 1, the control parameter generation circuit 88 adds a predetermined value to the current braking coefficient Dg.

[0444] When the braking coefficient Dg is changed in S2164, the control parameter generation circuit 88 confirms in S2165 whether the braking coefficient Dg falls within a predetermined range. If the braking coefficient Dg falls within the predetermined range (yes in S2165), the control parameter generation circuit 88 returns to S2162 and uses the changed braking coefficient Dg to calculate the slope of the ΔP / ΔF characteristic.

[0445] On the other hand, when the braking coefficient Dg exceeds the predetermined range (no in S2165), the control parameter generation circuit 88 determines that the appropriate characteristics cannot be obtained with the current speed regulation rate Kgd. In S2166, the braking coefficient Dg is returned to the initial value, and the speed regulation rate Kgd is changed. Specifically, the control parameter generation circuit 88 adds the predetermined value to the current speed regulation rate Kgd (initial value).

[0446] When the speed regulation rate Kgd is changed in S2166, the control parameter generation circuit 88 confirms in S2167 whether the speed regulation rate Kgd falls within a predetermined range. When the speed regulation rate Kgd deviates from the predetermined range (not in S2167), the control parameter generation circuit 88 proceeds to S2168. Since an appropriate speed regulation rate Kgd and braking coefficient Dg are not obtained, the speed regulation rate Kgd and braking coefficient Dg are set to their respective pre-prepared default values, and the process proceeds to S2169.

[0447] On the other hand, when the speed regulation rate Kgd is within a predetermined range in S2167 (which is true in S2167), the control parameter generation circuit 88 returns to S2162 and calculates the slope of the ΔP / ΔF characteristic using the modified speed regulation rate Kgd and braking coefficient Dg. The control parameter generation circuit 88 repeats the processing of S2162 to S2167 until it is determined to be true in S2163, or until it is determined to be false in S2167.

[0448] Furthermore, when the speed regulation rate Kgd and braking coefficient Dg in S2168 are set to their default values, even if load fluctuations occur, excess or insufficient power cannot be distributed proportionally according to the power ratio based on the operation plan.

[0449] In implementation method 1, according to Figure 19 The braking coefficient Dg and speed regulation rate Kgd can be calculated using the relationship between the braking coefficient Dg and the frequency of the AC system voltage. Alternatively, it can be calculated based on... Figure 18 The braking coefficient Dg and the speed regulation rate Kgd are calculated by showing the relationship between the speed regulation rate Kgd and the frequency of the AC system voltage.

[0450] When the speed regulation rate Kgd and braking coefficient Dg are set, the inertia constant M is calculated by the control parameter generation circuit 88 via S2169. In implementation method 1, the inertia constant M is calculated based on the response time required for the virtual synchronous generator control. Specifically, the response performance of the virtual synchronous generator control is based on the speed governor control circuit 833 ( Figure 14 The governor time constant Tg and the particle system operation circuit 837 obtained by using the oscillation equation. Figure 14The time constant M / Dg is determined by the speed governor time constant. In Embodiment 1, since the default value of the speed governor time constant Tg is used and the speed governor time constant Tg is not generated, only the time constant of the mass system operation circuit 837 is controlled. The time constant of the mass system operation circuit 837 is obtained by M / Dg according to the above equation (3). Therefore, in Embodiment 1, the inertia constant M is calculated by multiplying the time constant of the mass system operation circuit 837, which is determined by the default value, by the braking coefficient Dg.

[0451] When the inertial constant M is calculated in S2069, the dead frequency is calculated by the control parameter generation circuit 88 through S2170. Figure 37 To illustrate the process of calculating the dead-time frequency ( Figure 36 The flowchart of S2170).

[0452] like Figure 37 As shown, when processing begins, the control parameter generation circuit 88 acquires the power target value Pref via S21701. Then, via S21702, the control parameter generation circuit 88 acquires the dead-zone width information notified from CEMS 31. Via S21703, the switching frequency calculation circuit 89 uses the ΔP / ΔF characteristic output from the control parameter generation circuit 88 and the power target value Pref notified from the eighth control circuit 87 to calculate the switching frequency ΔF0 for switching the charging and discharging of the battery 40. Specifically, the switching frequency calculation circuit 89 calculates ΔF where ΔP = -Pref in the ΔP / ΔF characteristic as the switching frequency ΔF0.

[0453] When the switching frequency ΔF0 is calculated in S21703, the switching frequency calculation circuit 89 uses the switching frequency ΔF0 and the dead-time width information obtained in S21702 to calculate the upper and lower limits of the dead-time frequency in S21704. Specifically, the slope of the ΔP / ΔF characteristic is -Pref / ΔF0. Therefore, the switching frequency ΔF0 is -Pref / (the slope of the ΔP / ΔF characteristic).

[0454] When the power target value Pref is positive (discharge), such as Figure 24A As shown, the lower limit frequency of the dead zone is set to ΔF0 + system frequency, and the upper limit frequency of the dead zone is set to ΔF0 + dead zone width + system frequency.

[0455] When the power target value Pref is negative (charging), such as Figure 24B As shown, the upper limit frequency of the dead zone is set to ΔF0 + system frequency, and the lower limit frequency of the dead zone is set to ΔF0 - dead zone width + system frequency.

[0456] Additionally, when the absolute value of the power command is below a predetermined value, such as Figure 24CAs shown, in charge / discharge mode, the lower limit frequency of the dead zone is set to (-dead zone width) / 2, and the upper limit frequency is set to (dead zone width) / 2. The switching frequency calculation circuit 89 outputs the calculated upper and lower limit frequencies of the dead zone to the dead zone detection circuit 90, thus ending the generation process of control parameters.

[0457] Back Figure 33 When the calculation of the control parameters (speed regulation rate Kgd, braking coefficient Dg and inertia constant M) for the virtual synchronous generator control is completed in S216, the control parameter generation circuit 88 notifies the 8th control circuit 87 of the situation and outputs the calculated control parameters to the 8th control circuit 87.

[0458] When the calculated control parameters are received, the 8th control circuit 87 outputs the control parameters to the virtual synchronous generator control circuit 83, thereby updating the control parameters. When the update of the control parameters is complete, the 8th control circuit 87 clears (resets) the register (not shown) where the receive flag is set via S217, so that the processing returns to S201.

[0459] As described above, in the distributed power system according to Embodiment 1, when the generated power of the energy-generating device reaches a balance with the power consumed by the load due to fluctuations in the power consumption of the load or fluctuations in solar irradiance, the power conversion device is controlled to reduce the power supplied to the distributed power source, such as the battery, or the power supplied from the distributed power source to zero. This suppresses unnecessary charging and discharging and repeated charging and discharging among multiple distributed power sources caused by sensor errors in the voltmeter and ammeter, thus suppressing power loss and accelerated battery degradation caused by unnecessary charging and discharging.

[0460] Furthermore, as a method for creating the ΔP / ΔF characteristics when multiple power conversion devices (PCDs) equipped with a static inverter featuring virtual synchronous generator control are connected to a system, firstly, a reference ΔP / ΔF characteristic is generated by treating the multiple PCDs 41, which are the targets for generating power target values, as a single PCD. Using the generated reference ΔP / ΔF characteristic and the sum of the power target values ​​of the multiple PCDs 41, the switching frequency ΔF0 for switching between charging and discharging is calculated. Next, using this switching frequency ΔF0 and the power target value, a drooping characteristic (ΔP / ΔF characteristic) for each PCD 41 is generated. Thus, each PCD 41 can be assigned a ΔP / ΔF characteristic that makes the switching frequency ΔF0 the same among the multiple PCDs 41. Then, the ΔP / ΔF characteristic assigned to each PCD 41 is given a dead zone, thereby controlling the static inverter using the dead-zoned ΔP / ΔF characteristic when the power consumed by the user load and the power generated by the energy generation device reach a balance. Therefore, even when voltmeters and ammeters have sensor errors, unnecessary charging and discharging or repeated charging and discharging between distributed power sources such as batteries can be suppressed. As a result, power loss and damage to batteries caused by unnecessary charging and discharging can be suppressed.

[0461] Implementation method 2.

[0462] In Embodiment 1, a method for generating information for generating control parameters for controlling a virtual synchronous generator equipped in the power conversion device 41 in the CEMS 31, a method for generating control parameters in the power conversion device 41, a method for generating a dead zone assigned to the ΔP / ΔF characteristics, and a control method for the second DC / DC converter 403 and the second DC / AC converter 408 are described.

[0463] In Embodiment 2, the method for assigning a dead time to the ΔP / ΔF characteristic differs from that in Embodiment 1. Specifically, in Embodiment 2, a method for assigning hysteresis instead of a dead time to the ΔP / ΔF characteristic is described. Therefore, in Embodiment 2, some control methods of the second DC / DC converter 403 and the second DC / AC converter 408 differ from those in Embodiment 1, while the circuit structure of the distributed power supply system is the same as in Embodiment 1; therefore, detailed descriptions are omitted.

[0464] Figures 38A-38C A graph illustrating an example of the ΔP / ΔF characteristic (drooping characteristic) imparted to the power conversion device 41 of Embodiment 2. Hysteresis is imparted to the ΔP / ΔF characteristic in each graph.

[0465] Figure 38A A graph showing the ΔP / ΔF characteristics when the power target value Pref notified from CEMS 31 is positive (discharge). Figure 38AThe solid line in the figure shows the ΔP / ΔF characteristic of the battery 40 when it switches from the discharge mode to the charge mode, and the dashed line shows the ΔP / ΔF characteristic of the battery 40 when it switches from the charge mode to the discharge mode.

[0466] Compared with implementation method 1 ( Figure 24A Similarly, when the second DC / AC converter 408 operates in discharge mode, as shown by the solid line, the value of ΔP is fixed at the time point ΔP = -Pref, i.e., at the time point ΔF = ΔF0. Because ΔF = ΔF0, the output of the second DC / AC converter 408 is set to "zero". Thus, the battery 40 is also fixed in discharge mode. The output of the second DC / AC converter 408 is "zero" until the system voltage ΔF exceeds the hysteresis width. Then, when ΔF exceeds the hysteresis width, unlike in embodiment 1, the value of ΔP is set to the value indicated by the ΔP / ΔF characteristic. The second DC / AC converter 408 then operates in charging mode.

[0467] On the other hand, when the second DC / AC converter 408 operates in charging mode, as shown by the dashed line, the value of ΔP is fixed at the time point ΔP = -Pref (the time point ΔF = ΔF0). Because ΔF = ΔF0, the output of the second DC / AC converter 408 is set to "zero". Thus, the battery 40 is also fixed in charging mode. The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF drops below the hysteresis width. Then, when ΔF drops below the hysteresis width, unlike in embodiment 1, the value of ΔP is set to the value indicated by the ΔP / ΔF characteristic. The second DC / AC converter 408 then operates in discharging mode.

[0468] Figure 38B A graph showing the ΔP / ΔF characteristic when the power target value Pref notified from CEMS 31 is negative (charging). Figure 38B The solid line in the figure shows the ΔP / ΔF characteristic of the battery 40 when it switches from the discharge mode to the charge mode, and the dashed line shows the ΔP / ΔF characteristic of the battery 40 when it switches from the charge mode to the discharge mode.

[0469] Compared with implementation method 1 ( Figure 24BSimilarly, when the second DC / AC converter 408 operates in charging mode, as shown by the dashed line, the value of ΔP is fixed at the time point ΔP = Pref, i.e., at the time point ΔF = ΔF0. Because ΔF = ΔF0, the output of the second DC / AC converter 408 is set to "zero". Thus, the battery 40 is also fixed in charging mode. The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF drops below the hysteresis width. Then, when ΔF drops below the hysteresis width, unlike in embodiment 1, the value of ΔP is set to the value indicated by the ΔP / ΔF characteristic. The second DC / AC converter 408 then operates in discharging mode.

[0470] On the other hand, when the second DC / AC converter 408 operates in discharge mode, as shown by the solid line, the value of ΔP is fixed at the time point ΔP = Pref (the time point ΔF = ΔF0). Because ΔF = ΔF0, the output of the second DC / AC converter 408 is set to "zero". Thus, the battery 40 is also fixed in discharge mode. The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF exceeds the hysteresis width. Then, when ΔF exceeds the hysteresis width, unlike in embodiment 1, the value of ΔP is set to the value indicated by the ΔP / ΔF characteristic. The second DC / AC converter 408 then operates in charging mode.

[0471] Figure 38C A graph showing the ΔP / ΔF characteristics when the power target value Pref notified from CEMS 31 is zero (charge / discharge mode). Figure 38C The solid line in the figure shows the ΔP / ΔF characteristic of the battery 40 when it switches from the discharge mode to the charge mode, and the dashed line shows the ΔP / ΔF characteristic of the battery 40 when it switches from the charge mode to the discharge mode.

[0472] Compared with implementation method 1 ( Figure 24C Similarly, when the second DC / AC converter 408 operates in charging mode, as shown by the dashed line, the value of ΔP is fixed at the time point ΔP = 0 (Pref), i.e., at the time point ΔF = ΔF0. Because ΔF = ΔF0, the output of the second DC / AC converter 408 is set to "zero". Thus, the battery 40 is also fixed in charging mode. The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF drops below the hysteresis width. Then, when ΔF drops below the hysteresis width, unlike in embodiment 1, the value of ΔP is set to the value indicated by the ΔP / ΔF characteristic. The second DC / AC converter 408 then operates in discharging mode.

[0473] On the other hand, when the second DC / AC converter 408 operates in discharge mode, as shown by the solid line, the value of ΔP is fixed at the time point ΔP = 0 (Pref) (the time point ΔF = ΔF0). Because ΔF = ΔF0, the output of the second DC / AC converter 408 is set to "zero". Thus, the battery 40 is also fixed in discharge mode. The output of the second DC / AC converter 408 is "zero" until the system voltage ΔF exceeds the hysteresis width. Then, when ΔF exceeds the hysteresis width, unlike in embodiment 1, the value of ΔP is set to the value indicated by the ΔP / ΔF characteristic. The second DC / AC converter 408 then operates in charging mode.

[0474] As described above, when multiple power conversion units 41 equipped with static inverters featuring virtual synchronous generator control are connected to the power distribution system, the hysteresis characteristic (ΔP / ΔF characteristic) imparted to the power conversion units 41 by the virtual synchronous generator control is introduced. This prevents situations where, due to sensor errors, even if the generated power from the large solar power plant 26 is balanced with the power consumed by the load, the following occurs: Figure 22 As shown in (B), the discharge power of battery 40b is used to charge battery 40a (including the charging and discharging relay ball (chasing operation)). This suppresses unnecessary power exchange between batteries 40a and 40b, thus suppressing power loss caused by charging and discharging and accelerating battery degradation.

[0475] Furthermore, in Embodiment 2, similarly to Embodiment 1, as a method for creating the ΔP / ΔF characteristic, firstly, a reference ΔP / ΔF characteristic is generated by treating multiple power conversion devices 41, which are the objects of generating power target values, as a single power conversion device. Using the generated reference ΔP / ΔF characteristic and the sum of the power target values ​​of the multiple power conversion devices 41, the switching frequency ΔF0 for switching between charging and discharging is calculated. Next, using the switching frequency ΔF0 and the power target value of each power conversion device 41, the ΔP / ΔF characteristic of each power conversion device 41 is generated.

[0476] However, the method for generating the ΔP / ΔF characteristic is not limited to this. For example, when multiple power conversion devices 41 are operating in discharge mode, the ΔP / ΔF characteristic of the power conversion device 41 corresponding to the battery 40 with the lowest SOC is generated. Then, the switching frequency ΔF0 is calculated based on the generated ΔP / ΔF characteristic and used as the switching frequency ΔF0 when generating the ΔP / ΔF characteristic for the power conversion devices 41 corresponding to other batteries 40.

[0477] Alternatively, when multiple power conversion devices 41 are operating in charging mode, the ΔP / ΔF characteristic of the power conversion device 41 corresponding to the battery 40 with the highest SOC is generated. Then, the switching frequency ΔF0 is calculated based on the generated ΔP / ΔF characteristic and used as the switching frequency ΔF0 when generating the ΔP / ΔF characteristic for the power conversion devices 41 corresponding to other batteries 40.

[0478] By generating the ΔP / ΔF characteristic in this way, it is possible to generate the ΔP / ΔF characteristic in the discharge mode that matches the battery 40 with the minimum SOC, and in the charging mode that matches the battery 40 with the maximum SOC.

[0479] The following uses Figures 10-16 , Figure 33 , Figure 36 And Figure 38~ Figure 41 The operation of the power conversion device 41 in Embodiment 2 will be explained. Furthermore, the operation of the CEMS 31 is the same as that of the CEMS 31 in Embodiment 1, so the explanation is omitted.

[0480] Next, the fourth control circuit 409 will be described. Figure 7 ) work. Figure 33 This is a flowchart illustrating the operation of the power conversion device 41. (For example...) Figure 33 As shown, when the process begins, similarly to Embodiment 1, the fourth control circuit 409 initializes various control parameters via S200. Next, via S201, the fourth control circuit 409 collects the voltage values ​​measured by voltmeters 401, 406, and 410, the current values ​​measured by ammeters 402, 407, and 411, and the state information (SOC, etc.) of the battery 40, and calculates the charging and discharging power and charge / discharge capacity of the battery based on the collected data.

[0481] The AC voltage of the power distribution system 24, measured by voltmeter 410, is input to the AC frequency detection circuit 81. Figure 11 Through S202, the AC frequency detection circuit 81 detects the zero-crossing point of the AC voltage waveform.

[0482] When a zero-crossing is detected in S202 (yes in S202), the phase detection circuit 810 sets the zero-crossing detection flag via S203. When the processing of S203 ends, or when no zero-crossing is detected in S202 (no in S202), the fourth control circuit 409 controls the second DC / DC converter 403 via S220.

[0483] The following uses Figure 10 and Figure 39This explains the control of the second DC / DC converter 403 in the power conversion device 41 of Embodiment 2.

[0484] As described above, since the power conversion device 41 is equipped with virtual synchronous generator control, the second DC / AC converter 408 is controlled as a voltage source. That is, the second DC / AC converter 408 is voltage controlled. Therefore, the voltage of the DC bus 405 is managed by the second DC / AC converter 403. Figure 39 This is a flowchart illustrating the control processing details of the second DC / DC converter 403.

[0485] In S2201, the third control circuit 404 calculates the charge / discharge power value based on the voltage of the DC bus 405 detected by the voltmeter 406 and the current detected by the ammeter 407. In S2202, the seventh control circuit 74 confirms whether to proceed from the eighth control circuit 87 ( Figure 11 The dead-zone flag (whether it is set) is notified. When the dead-zone flag is not set (no in S2202), the third control circuit 404 generates normal charge / discharge command values ​​via S2204. On the other hand, when the dead-zone flag is set (yes in S2202), the seventh control circuit 74 fixes the current operating mode via S2206. Specifically, if the current operating mode is charging mode, the charging mode is maintained; if it is discharging mode, the discharging mode is maintained. Next, via S2207, the seventh control circuit 74 sets the charge / discharge power command value to zero and outputs it to the second DC / DC converter 403, ending the control processing of the second DC / DC converter 403.

[0486] Back Figure 33 When the control processing of the second DC / DC converter 403 ends, the fourth control circuit 409 controls the second DC / AC converter 408 via S204. The following uses... Figure 11 and Figure 40 This explains the control of the second DC / AC converter 408 in Implementation Method 2.

[0487] Similar to Embodiment 1, the power conversion device 41 is equipped with virtual synchronous generator control, so the second DC / AC converter 408 is controlled as a voltage source. That is, the second DC / AC converter 408 is voltage-controlled. Therefore, when the power supplied to the power distribution system 24 is insufficient, the second DC / AC converter 408 is controlled to increase the output power. On the other hand, when the power supplied to the power distribution system 24 is excessive, the second DC / AC converter 408 is controlled to reduce the output power.

[0488] Figure 40This is a flowchart illustrating the control processing details of the second DC / AC converter 408.

[0489] like Figure 40 As shown, when the effective power calculation circuit 82 of S2021 is used... Figure 11 When calculating the power value based on the measurements of voltmeter 410 and ammeter 411, the calculated power value is integrated in step S2022. When the zero-crossing detection flag is set (yes in step S2023), the effective power calculation circuit 82 proceeds to step S2024, stores the integrated value of the effective power value for one cycle of AC voltage in the storage circuit (not shown) of the 8th control circuit 87, and initializes the integrated value to zero in step S2025.

[0490] When the processing in S2025 ends, or if the zero-crossing detection flag is not set (not in S2023), the dead-time detection circuit 90 detects the dead-time period via S2033. In Embodiment 2, the dead-time detection circuit 90 detects the hysteresis period. Specifically, the dead-time detection circuit 90 detects the hysteresis period based on the system frequency information detected by the AC frequency detection circuit 81 and the upper and lower limits of the hysteresis calculated by the switching frequency calculation circuit 89.

[0491] Figure 41 This is a flowchart illustrating the details of the hysteresis detection process. When processing begins, the dead-time detection circuit 90 detects the hysteresis period based on the switching frequency ΔF0 output from the switching frequency calculation circuit 89, the upper and lower limits of the hysteresis frequency, and the frequency information of the target AC voltage used when voltage-controlling the second DC / AC converter 408. Furthermore, in Embodiment 2, the case where the hysteresis period is detected based on the frequency information of the target AC voltage used when operating the second DC / AC converter 408 under voltage control is described, but it is not limited to this. For example, similar to Embodiment 1, the same effect can be obtained by using the detection result of the system frequency output from the AC frequency detection circuit 81 for control.

[0492] like Figure 41As shown, when processing begins, the dead-time detection circuit 90 acquires the frequency information of the target AC voltage output from the virtual synchronous generator control circuit 83 via S20331. Next, via S20332, the dead-time detection circuit 90 confirms whether hysteresis is detected and the dead-time flag is set. When the dead-time flag is not set (no in S20332), via S20333, it is confirmed whether the frequency of the target AC voltage is near the battery switching frequency ΔF0 (i.e., whether it is near the hysteresis frequency). In Embodiment 2, considering the influence of the sampling phase variation of the voltmeter 410, when it falls within the range of the switching frequency ΔF0 ± 0.01 × ΔFmax, it is considered that the start of the hysteresis period has been detected and control is performed.

[0493] When the frequency of the target AC voltage is near the switching frequency ΔF0 (yes in S20333), the start of the hysteresis period is considered to have been detected in S20334. When the frequency of the target AC voltage is not near the switching frequency ΔF0 (no in S20333), or when the start of the hysteresis period is detected in S20334, the detection process of the hysteresis period ends.

[0494] On the other hand, when the dead-time flag is set (yes in S20332), the dead-time detection circuit 90 confirms whether the battery 40 is in charging mode via S20335. In Embodiment 2, unlike Embodiment 1, the ΔP / ΔF characteristic is incorporating hysteresis instead of a dead time. Therefore, the determination of the end of the hysteresis period depends on whether the battery 40 is in charging or discharging mode. (See also...) Figures 38A-38C This explains the specific approach to the termination condition of the lag.

[0495] Figure 38A To illustrate the ΔP / ΔF characteristic when the power target value Pref notified from CEMS 31 is positive (discharge). For example... Figure 38A As shown, when the second DC / AC converter 408 is in discharge mode, at a time point near ΔP = -Pref (or near ΔF = ΔF0), ΔP is fixed, making the output of the second DC / AC converter 408 "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF exceeds the hysteresis width (the hysteresis width when switching from discharge to charging). At this time, the dead-time flag is set. Furthermore, when ΔF is within the hysteresis width, if the power supplied to the system is insufficient due to the reduced power generation of the large solar power plant 26, causing ΔF to decrease and drop below the switching frequency ΔF0, the dead-time flag is reset, and the power conversion device 41 operates in discharge mode. On the other hand, when ΔF exceeds the upper limit frequency of the hysteresis, ΔP is set to the value shown by the ΔP / ΔF characteristics notified from CEMS 31, causing the second DC / AC converter 408 to operate in charging mode.

[0496] Similarly, when the second DC / AC converter 408 is in charging mode, at a time point near ΔP = -Pref (or near ΔF = ΔF0), ΔP is fixed, making the output of the second DC / AC converter 408 "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF drops below the hysteresis width (the hysteresis width when switching from charging to discharging). At this time, the dead-time flag is set. Furthermore, when ΔF is within the hysteresis width, if the power supplied to the system is excessive due to the increased power generated by the large solar power plant 26, causing ΔF to increase and exceed the switching frequency ΔF0, the dead-time flag is reset, and the power conversion device 41 operates in charging mode. On the other hand, when ΔF drops below the lower limit frequency of the hysteresis, ΔP is set to the value shown by the ΔP / ΔF characteristics notified from CEMS 31, making the second DC / AC converter 408 operate in discharging mode.

[0497] Figure 38B To illustrate the ΔP / ΔF characteristic when the power target value Pref notified from CEMS 31 is negative (charging). For example... Figure 38B As shown, when the second DC / AC converter 408 is in charging mode, at a time point near ΔP = Pref (a time point near ΔF = ΔF0), ΔP is fixed, making the output of the second DC / AC converter 408 "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF drops below the hysteresis width (the hysteresis width when switching from charging to discharging). At this time, the dead-time flag is set. Furthermore, when ΔF is within the hysteresis width, if the power supplied to the system is excessive due to the increased power generated by the large solar power plant 26, causing ΔF to increase and exceed the switching frequency ΔF0, the dead-time flag is reset, and the power conversion device 41 operates in charging mode. On the other hand, when ΔF drops below the lower limit frequency of the hysteresis, ΔP is set to the value shown by the ΔP / ΔF characteristics notified from CEMS 31, making the second DC / AC converter 408 operate in discharging mode.

[0498] Similarly, when the second DC / AC converter 408 is in discharge mode, at a time point near ΔP = Pref (or near ΔF = ΔF0), ΔP is fixed, making the output of the second DC / AC converter 408 "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF exceeds the upper limit frequency of the hysteresis width (the hysteresis width when switching from discharge to charging). At this time, the dead-time flag is set. Furthermore, when ΔF is within the hysteresis width, if the power supplied to the system is insufficient due to a decrease in the generated power of the large solar power plant 26, causing ΔF to decrease and drop below the switching frequency ΔF0, the dead-time flag is reset, and the power conversion device 41 operates in discharge mode. On the other hand, when ΔF exceeds the upper limit frequency of the hysteresis, ΔP is set to the value shown by the ΔP / ΔF characteristics notified from the CEMS 31, causing the second DC / AC converter 408 to operate in charging mode.

[0499] Figure 38C To illustrate the ΔP / ΔF characteristics when the power target value notified from CEMS 31 is almost zero (charge / discharge mode). For example... Figure 38C As shown, when the second DC / AC converter 408 is in charging mode, at a time point near ΔP = 0 (a time point near ΔF = ΔF0 = 0), ΔP is fixed, making the output of the second DC / AC converter 408 "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF drops below the lower limit frequency of the hysteresis width (the hysteresis width when switching from charging to discharging). At this time, the dead-time flag is set. Furthermore, when ΔF is within the hysteresis width, if the power supplied to the system is excessive due to the increased power generated by the large solar power plant 26, causing ΔF to increase and exceed the switching frequency ΔF0, the dead-time flag is reset, and the power conversion device 41 operates in charging mode. On the other hand, when ΔF drops below the lower limit frequency of the hysteresis, ΔP is set to the value shown by the ΔP / ΔF characteristics notified from CEMS 31, making the second DC / AC converter 408 operate in discharging mode.

[0500] Similarly, when the second DC / AC converter 408 is in discharge mode, at a time point near ΔP = 0 (or near ΔF = ΔF0 = 0), ΔP is fixed, making the output of the second DC / AC converter 408 "zero". The output of the second DC / AC converter 408 remains "zero" until the system voltage ΔF exceeds the upper limit frequency of the hysteresis width (the hysteresis width when switching from discharge to charging). At this time, the dead-time flag is set. Furthermore, when ΔF is within the hysteresis width, if the power supplied to the system is insufficient due to a decrease in the generated power of the large solar power plant 26, causing ΔF to decrease and drop below the switching frequency ΔF0, the dead-time flag is reset, and the power conversion device 41 operates in discharge mode. On the other hand, when ΔF exceeds the upper limit frequency of the hysteresis width, ΔP is set to the value shown by the ΔP / ΔF characteristics notified from the CEMS 31, and the second DC / AC converter 408 operates in charging mode.

[0501] Back Figure 41 When battery 40 is in charging mode in S20335 (yes in S20335), the dead-time detection circuit 90 checks in S20336 whether the frequency of the target AC voltage is below the lower limit frequency of the hysteresis. If the frequency of the target AC voltage is below the lower limit frequency of the hysteresis (yes in S20336), the dead-time detection circuit 90 determines in S20337 that the end of the hysteresis period has been detected and terminates the process. On the other hand, when the frequency of the target AC voltage is greater than the lower limit frequency of the hysteresis (no in S20336), the dead-time detection circuit 90 checks in S20338 whether the frequency of the target AC voltage exceeds the upper limit frequency of the hysteresis. If the frequency of the target AC voltage exceeds the upper limit frequency of the hysteresis (yes in S20338), the dead-time detection circuit 90 determines in S20339 that the end of the hysteresis has been detected and terminates the process. When the frequency of the target AC voltage is below the upper limit frequency of the hysteresis (no in S20338), the dead-time detection circuit 90 ends the processing.

[0502] In contrast, when the battery 40 is in discharge mode (No in S20335), the dead-time detection circuit 90 checks in S20340 whether the frequency of the target AC voltage is above the upper limit frequency of the hysteresis. If the frequency of the target AC voltage is above the upper limit frequency of the hysteresis (Yes in S20340), the dead-time detection circuit 90 determines in S20341 that the end of the hysteresis has been detected and terminates the process. On the other hand, when the frequency of the target AC voltage is less than the upper limit frequency of the hysteresis (No in S20340), the dead-time detection circuit 90 checks in S20342 whether the frequency of the target AC voltage has dropped below the lower limit frequency of the hysteresis. If the frequency of the target AC voltage drops below the lower limit frequency of the hysteresis (Yes in S20342), the dead-time detection circuit 90 determines in S20343 that the end of the hysteresis has been detected and terminates the process. When the frequency of the target AC voltage is below the lower limit frequency of the hysteresis (no in S20342), the dead-time detection circuit 90 ends the processing.

[0503] Back Figure 40 When the detection process during the hysteresis period (S2033) ends, the eighth control circuit 87 checks whether the dead-time flag is set via S2027. If the dead-time flag is not set (not in S2027), the eighth control circuit 87 checks whether the start of hysteresis has been detected via S2034. In Embodiment 2, the start of hysteresis is detected using the frequency of the target AC voltage output from the virtual synchronous generator control circuit 83. Alternatively, it can be detected using the detection result of the frequency output from the AC frequency detection circuit 81, or, similarly in Embodiment 1, by whether the absolute value of the charge / discharge power of the battery 40 is below a predetermined value.

[0504] When the start of hysteresis is detected (yes in S2028), the dead time detection circuit 90 sets the dead time flag in a register (not shown) via S2029.

[0505] When the dead time flag is set (yes in S2027), the dead time detection circuit 90 confirms whether the end of hysteresis has been detected via S2031. When the end of hysteresis is detected (yes in S2031), the dead time detection circuit 90 resets the dead time flag in a register (not shown).

[0506] When no hysteresis start is detected (no in S2028) or no hysteresis end is detected (S2031), or when the dead-time flag is set (S2029) or reset (S2032), the fourth control circuit 409 generates control command values ​​for controlling the second DC / AC converter 408 via S2030. Furthermore, the generation of control command values ​​by the inverter voltage control circuit 85 is the same as the process described in Embodiment 1, and therefore its description is omitted.

[0507] Back Figure 33 When the control command value for the second DC / AC converter 408 is generated in S204, the virtual synchronous generator control circuit 83 (…) is activated via S205. Figure 11 The virtual synchronous generator control is executed. In Embodiment 2, similarly to Embodiment 1, one cycle of the AC voltage is used as the control cycle. Furthermore, the control cycle can also be set to an integer multiple of one cycle of the AC voltage, or a predetermined cycle such as a 1-second cycle.

[0508] Figure 14 A block diagram illustrating the structure of the virtual synchronous generator control circuit 83 is provided. When the control timing is determined to have arrived, the 8th control circuit 87 (… Figure 11 The virtual synchronous generator control circuit 83 is instructed to generate information related to the frequency and phase used in voltage control. In Embodiment 2, similarly to Embodiment 1, the third sine wave generation circuit 851 within the inverter voltage control circuit 85 is updated at the zero-crossing point. Figure 13 The frequency and phase of the generated sine wave. Therefore, in Embodiment 2, the control period is the period of the zero-crossing point detected by the AC frequency detection circuit 81. Furthermore, the operation of the virtual synchronous generator control circuit 83 is the same as that described in Embodiment 1, so the description is omitted.

[0509] Back Figure 33 When the virtual synchronous generator control process in S205 ends, the fourth control circuit 409 checks in S206 whether a transmission request for measurement data has been received from CEMS 31. If a transmission request is received from CEMS 31 (yes in S206), the eighth control circuit 87 (…) checks in S207… Figure 11 ) via communication I / F 412 ( Figure 7 The measurement data will be reported to CEMS 31.

[0510] On the other hand, when measurement data is notified in S207, or when there is no transmission request from CEMS 31 (no in S206), the 8th control circuit 87 proceeds to S208 to confirm whether control information has been received from CEMS 31.

[0511] When control information is received from CEMS 31 (yes in S208), the 8th control circuit 87 sets the control information reception flag in S209. When the process in S209 ends, or when no control information is received from CEMS 31 (no in S208), the 8th control circuit 87 checks whether the zero-crossing detection flag is set in S210. When the zero-crossing detection flag is not set (no in S210), the process returns to S201.

[0512] On the other hand, when the zero-crossing detection flag is set (yes in S210), the second sine wave generation circuit 812 (…) is activated via S211. Figure 12 The system acquires information on the frequency and phase of the system voltage and resets the zero-crossing detection flag in S212.

[0513] When the zero-crossing detection flag is reset in S212, the second sine wave generation circuit 812 updates the frequency and phase information of the system voltage to the information taken in S211 via S213.

[0514] When the processing in S213 is completed, the 8th control circuit 87 checks in S214 whether control information has been received from CEMS 31 (whether the control information receiving flag is set). If the receiving flag is not set (no in S214), the processing returns to S201.

[0515] On the other hand, when the receiving flag is set (yes in S214), the 8th control circuit 87 replaces the frequency target value (reference frequency Fref) and the power target value Pref with the received data via S215.

[0516] Through S216, the control parameter generation circuit 88 generates the control parameters (speed regulation rate Kgd, braking coefficient Dg, and inertia constant M) for the virtual synchronous generator control. Figure 36 To illustrate the process of generating control parameters ( Figure 33 The flowchart of S216 is shown. In Embodiment 2, the case where the slope of the ΔP / ΔF characteristic is input from CEMS 31 as the information required to generate the control parameters for virtual synchronous generator control is described, similar to Embodiment 1. Furthermore, in Embodiment 2, similar to Embodiment 1, in addition to using the slope of the ΔP / ΔF characteristic, system information (reference frequency Fref, power target value Pref, ΔFmax information) and inverter capacity Cinv are used as the information required to generate the control parameters to generate the control parameters.

[0517] like Figure 36As shown, when generating control parameters, the control parameter generation circuit 88 initializes the speed regulation rate Kgd and braking coefficient Dg to predetermined initial values ​​via S2161. Via S2162, the control parameter generation circuit 88 uses the speed regulation rate Kgd and braking coefficient Dg to calculate the slope of the ΔP / ΔF characteristic. In Embodiment 2, the control parameter generation circuit 88 is similar to that in Embodiment 1. Figure 11 ) Install simulated virtual synchronous generator control circuit 83 ( Figure 11 This section describes the operation of a virtual synchronous generator model and the use of this model to generate control parameters.

[0518] In S2162, the control parameter generation circuit 88 inputs the set speed regulation rate Kgd and braking coefficient Dg into the virtual synchronous generator model, thereby calculating the slope of the ΔP / ΔF characteristic.

[0519] When the slope of the ΔP / ΔF characteristic is calculated in S2162, the control parameter generation circuit 88 compares the calculated slope of the ΔP / ΔF characteristic with the value obtained through S2163. Figure 28 S0563 ( Figure 30 The slopes of the generated ΔP / ΔF characteristics are compared. Specifically, the control parameter generation circuit 88 confirms whether the deviation between the slopes of these two ΔP / ΔF characteristics falls within a predetermined allowable range.

[0520] When the slope deviation falls within the above-mentioned allowable range, the control parameter generation circuit 88 determines that the slopes of the two ΔP / ΔF characteristics are consistent (yes in S2163), and causes the process to proceed to S2169.

[0521] On the other hand, when the slope deviation does not fall within the aforementioned allowable range, the control parameter generation circuit 88 determines that the slopes of the two ΔP / ΔF characteristics are inconsistent (no in S2163). In this case, the control parameter generation circuit 88 proceeds to S2164 and changes the braking coefficient Dg. The control parameter generation circuit 88 adds a predetermined value to the current braking coefficient Dg.

[0522] When the braking coefficient Dg is changed in S2164, the control parameter generation circuit 88 checks in S2165 whether the braking coefficient Dg falls within a predetermined range. If the braking coefficient Dg falls within the predetermined range (yes in S2165), the control parameter generation circuit 88 returns to S2162 and uses the changed braking coefficient Dg to calculate the slope of the ΔP / ΔF characteristic.

[0523] On the other hand, when the braking coefficient Dg exceeds the predetermined range (no in S2165), the control parameter generation circuit 88 determines that the appropriate characteristics cannot be obtained with the current speed regulation rate Kgd. In S2166, the braking coefficient Dg is returned to the initial value, and the speed regulation rate Kgd is changed. Specifically, the control parameter generation circuit 88 adds the predetermined value to the current speed regulation rate Kgd (initial value).

[0524] When the speed regulation rate Kgd is changed in S2166, the control parameter generation circuit 88 confirms in S2167 whether the speed regulation rate Kgd falls within a predetermined range. When the speed regulation rate Kgd deviates from the predetermined range (not in S2167), the control parameter generation circuit 88 proceeds to S2168, deeming that an appropriate speed regulation rate Kgd and braking coefficient Dg have not been calculated, and sets the speed regulation rate Kgd and braking coefficient Dg to their respective pre-prepared default values, causing the process to proceed to S2169.

[0525] On the other hand, when the speed regulation rate Kgd is within a predetermined range in S2167 (yes in S2167), the control parameter generation circuit 88 returns to S2162 and calculates the slope of the ΔP / ΔF characteristic using the modified speed regulation rate Kgd and braking coefficient Dg. The control parameter generation circuit 88 repeats the processing of S2162 to S2167 until it is determined to be yes in S2163 or no in S2167. Furthermore, in Embodiment 2, similarly to Embodiment 1, according to... Figure 19 The relationship between the braking coefficient Dg and the frequency of the AC system voltage is shown. Calculate the braking coefficient Dg and the speed regulation rate Kgd.

[0526] When the speed regulation rate Kgd and braking coefficient Dg are set, the inertia constant M is calculated by the control parameter generation circuit 88 via S2169. The inertia constant M is calculated based on the response time required for the virtual synchronous generator control. Specifically, the response performance of the virtual synchronous generator control is determined by the governor control circuit 833 (…). Figure 14 The governor time constant Tg and the particle system operation circuit 837 derived from the oscillation equation. Figure 14 The time constant M / Dg is determined by the speed governor. In Embodiment 2, similar to Embodiment 1, the default value of the speed governor time constant Tg is used, and the speed governor time constant Tg is not generated. Therefore, only the time constant of the mass system operation circuit 837 is controlled. The time constant of the mass system operation circuit 837 is obtained using M / Dg according to the above formula (3). Therefore, the inertial constant M is calculated by multiplying the time constant of the mass system operation circuit 837, which is determined by the default value, by the braking coefficient Dg.

[0527] When the inertial constant M is calculated via S2069, the hysteresis frequency is calculated via S2170 by the control parameter generation circuit 88. Figure 37 To illustrate the process of calculating the hysteresis frequency ( Figure 36 The flowchart of S2170).

[0528] like Figure 37 As shown, when processing begins, the control parameter generation circuit 88 acquires the power target value Pref via S21701. Then, via S21702, the control parameter generation circuit 88 acquires the dead-zone width information notified from CEMS 31. Via S21703, the switching frequency calculation circuit 89 uses the ΔP / ΔF characteristic output from the control parameter generation circuit 88 and the power target value Pref notified from the eighth control circuit 87 to calculate the switching frequency ΔF0 for switching the charging and discharging of the battery 40. Specifically, the switching frequency calculation circuit 89 calculates ΔF where ΔP = -Pref in the ΔP / ΔF characteristic as the switching frequency ΔF0.

[0529] When the switching frequency ΔF0 is calculated in S21703, the switching frequency calculation circuit 89 uses the switching frequency ΔF0 and the dead-time width information obtained in S21702 to calculate the upper and lower limits of the hysteresis frequency in S21704. Specifically, the slope of the ΔP / ΔF characteristic is -Pref / ΔF0. Therefore, the switching frequency ΔF0 is -Pref / (the slope of the ΔP / ΔF characteristic).

[0530] like Figures 38A-38B As shown, when switching the battery 40 from discharging to charging, the lower limit frequency of the hysteresis is set to ΔF0, and the upper limit frequency of the hysteresis is set to ΔF0 + hysteresis width. Conversely, when switching the battery 40 from charging to discharging, the upper limit frequency of the hysteresis is set to ΔF0, and the lower limit frequency of the hysteresis is set to ΔF0 - hysteresis width. The switching frequency calculation circuit 89 outputs the calculated upper and lower limit frequencies of the hysteresis to the dead-time detection circuit 90, ending the control parameter generation process.

[0531] Back Figure 33 When the calculation of the control parameters (speed regulation rate Kgd, braking coefficient Dg and inertia constant M) for the virtual synchronous generator control is completed in S216, the control parameter generation circuit 88 notifies the 8th control circuit 87 of the situation and outputs the calculated control parameters to the 8th control circuit 87.

[0532] When the calculated control parameters are received, the 8th control circuit 87 outputs and updates the control parameters to the virtual synchronous generator control circuit 83. When the update of the control parameters is completed, the 8th control circuit 87 clears (resets) the register (not shown) where the receive flag is set via S217, so that the processing returns to S201.

[0533] As described above, in the distributed power system according to Embodiment 2, when the generated power of the energy-generating device reaches a balance with the power consumed by the load due to fluctuations in the power consumption of the load or fluctuations in solar radiation, the power conversion device is controlled to make the power supplied to the distributed power source, such as the battery, or the power supplied from the distributed power source, zero. This suppresses unnecessary charging and discharging and repeated charging and discharging between multiple distributed power sources caused by sensor errors of the voltmeter and ammeter, thus suppressing power loss and accelerated battery degradation caused by unnecessary charging and discharging.

[0534] Furthermore, as a method for creating the ΔP / ΔF characteristics when multiple power conversion devices (PCDs) equipped with a static inverter featuring virtual synchronous generator control are connected to a system, a reference ΔP / ΔF characteristic is first generated by treating the multiple PCDs 41, which are the targets for generating power target values, as a single PCD. Using the generated reference ΔP / ΔF characteristic and the sum of the power target values ​​of the multiple PCDs 41, the switching frequency ΔF0 for switching between charging and discharging is calculated. Next, using this switching frequency ΔF0 and the power target value, the ΔP / ΔF characteristics of each PCD 41 are generated. This allows each PCD 41 to be assigned a decreasing characteristic (ΔP / ΔF characteristic) that makes the switching frequency ΔF0 the same across the multiple PCDs 41. Then, the decreasing characteristic assigned to each PCD 41 is given a hysteresis, thereby controlling the static inverter using the decreasing characteristic with a dead zone when the power consumed by the user load and the power generated by the energy generation device reach a balance. Therefore, even when voltmeters and ammeters have sensor errors, unnecessary charging and discharging or repeated charging and discharging between multiple distributed power sources (such as batteries) can be suppressed. As a result, power loss and damage to batteries caused by unnecessary charging and discharging can be suppressed.

[0535] As described above, according to embodiments 1 and 2, in a power distribution system 24 equipped with multiple power conversion devices 41 having static inverters with virtual synchronous generator control, the drooping characteristic (ΔP / ΔF characteristic) near the switching of charging and discharging of the battery 40 is made to have a dead zone or hysteresis. This allows for the suppression of unnecessary charging and discharging or repeated charging and discharging between multiple batteries, even if the voltmeter and ammeter have sensor errors, when the power consumed by the user load is balanced with the power generated by energy-generating equipment such as the large solar power plant 26, without the need for charging and discharging from the battery 40. This suppresses power loss and damage to the batteries caused by unnecessary charging and discharging.

[0536] Furthermore, according to embodiments 1 and 2, when creating an operation plan (power target value) for the power conversion device 41 for the battery, the configuration is such that control parameters (specifically, the slope of the ΔP / ΔF characteristic) for virtual synchronous generator control are generated based on the switching frequency ΔF0 calculated according to the capacity of the static inverter in each power conversion device 41 and the power target value. This allows the frequency at which the dead zone (or hysteresis) in each power conversion device 41 begins to be the same across multiple power conversion devices 41.

[0537] Additionally, as an example of a descent characteristic (ΔP / ΔF characteristic) with dead zone or hysteresis, although it is shown Figures 24A-24C and Figures 38A-38C The characteristics shown are not limited to these. For example, the dead zone (or hysteresis) when switching from charging to discharging and the dead zone (or hysteresis) when switching from discharging to charging can be configured to differ depending on, for example, the SOC of the battery 40. For example, a structure can be adopted in which a dead zone (or hysteresis) prioritizing charging is provided when the SOC is low, and a dead zone (or hysteresis) prioritizing discharging is provided when the SOC is high.

[0538] Furthermore, in embodiments 1 and 2, regarding the detection of the start of dead zone (or hysteresis), a structure was described that uses the switching of charging and discharging of the battery 40, or the frequency of the AC voltage target value output from the virtual synchronous generator control circuit 83 for detection, but is not limited to this. For example, the same effect can be obtained by using the detection result of the AC frequency of the system voltage output from the AC frequency detection circuit 81 for control.

[0539] Furthermore, while the upper and lower frequency limits for dead zone (or hysteresis) are calculated within the CEMS 31 based on the inverter capacity of the second DC / AC converter 408 of the power conversion device 41 and the SOC of the battery 40, the approach is not limited to this. For example, the upper and lower frequency limits can also be set to predetermined values.

[0540] Furthermore, regarding the width of the dead zone (or hysteresis), the same effect can be achieved even if a structure is used whereby each power conversion device 41, rather than CEMS 31, is generated based on the inverter capacity of the second DC / AC converter 408 and the SOC of the battery 40.

[0541] Furthermore, while embodiments 1 and 2 describe the case where a virtual synchronous generator control is provided in the power conversion device 41, this is not the only scenario. The same effect is achieved when a virtual synchronous generator control is provided in energy-generating equipment such as a wind turbine, which goes without saying. In particular, wind turbines use propellers to rotate the motor, thus having inertial force on the generator side, so the same effect is naturally achieved.

[0542] Furthermore, while embodiments 1 and 2 describe the case of installing large-capacity batteries such as several batteries 40 in the power distribution system 24, it is also possible to equip power conversion devices for household batteries and electric vehicles with virtual synchronous generator control, thus implementing the same control as CEMS 31. In this case, the power conversion devices connected to the power distribution system 24 would be in the hundreds. Moreover, it goes without saying that configuring large-capacity batteries such as batteries 40 (e.g., hundreds of kW to several MW) and household batteries (several kW) would achieve the same effect.

[0543] Furthermore, although the power conversion device 41 has been described in embodiments 1 and 2, it is not limited thereto. In systems where a virtual synchronous generator control is provided, such as those where a static inverter is controlled as a voltage source and the system receives power from sources like solar cells (not limited to large-scale solar power plants, but also residential solar cells), wind turbines, or fuel cells, the same effect can be achieved by similarly configuring the control parameters for generating the virtual synchronous generator control. This goes without saying. Furthermore, on-board batteries from electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), or fuel cell vehicles (FCVs) can also be used.

[0544] Furthermore, while embodiments 1 and 2 describe the application of the technology of this disclosure to a power distribution system, this is not a limitation. The same effect can also be achieved by applying the technology of this disclosure to a power transmission system or a microgrid of a self-sufficient system. Moreover, although embodiments 1 and 2 are described using three-phase AC as an example, this is not a limitation; single-phase AC or single-phase three-wire AC can also be used. Furthermore, even in the case where a system-use battery power conversion device (three-phase AC) and a household battery system (single-phase AC) coexist, if the control parameters for generating a virtual synchronous generator are similarly configured, the same effect will naturally be achieved.

[0545] Furthermore, while embodiments 1 and 2 describe the case where the capacity of the static inverter and the power target value are used for calculation when generating control parameters for virtual synchronous generator control for the static inverter in the power conversion device 41, this is not a limitation. For example, if the ratio of the battery capacity to the static inverter capacity is different, such as when the battery capacity of battery 40a is twice the capacity of the static inverter in the power conversion device 41a, or the battery capacity of battery 40b is three times the capacity of the static inverter in the power conversion device 41b, the same effect can be obtained by configuring the system to generate the operation plan (power target value) considering the aforementioned capacity ratio, or by considering the aforementioned capacity ratio when generating the information required for generating control parameters for virtual synchronous generator control.

[0546] In embodiments 1 and 2, it was described that when the control parameters for virtual synchronous generator control are generated in CEMS 31, the information to be sent when generating the control parameters in CEMS 31 includes system information, the slope of the ΔP / ΔF characteristic (or information required to generate the control parameters), in addition to the power target value, is also sent. However, this is not the only possibility. If the CEMS 31 is configured to send at least the information required to generate control parameters and set the dead zone (or hysteresis) in the power conversion device equipped with virtual synchronous generator control connected to the power distribution system 24, the same effect can certainly be obtained.

[0547] In embodiments 1 and 2, although the case where a virtual synchronous generator model is built-in is described when determining the control parameters of the virtual synchronous generator control unit, or... Figure 19 The relationship between the braking coefficient Dg and frequency is shown in a table format, with multiple speed regulation rates Kgd values ​​pre-stored as tabular data. Based on ΔFmax information, a combination of speed regulation rate Kgd and braking coefficient Dg that has a slope approximately consistent with the ΔP / ΔF characteristic is searched, or... Figure 18 The relationship between the speed regulation rate Kgd and the frequency is shown as tabular data stored in advance according to the values ​​of multiple braking coefficients Dg. Based on the ΔFmax information, the combination of speed regulation rate Kgd and braking coefficient Dg that is roughly consistent with the slope of the ΔP / ΔF characteristic is searched. However, it is not limited to this. For example, it can be done by embedding the virtual synchronous generator control unit in the form of a mathematical formula model or other methods.

[0548] Furthermore, while embodiments 1 and 2 describe the case where the control parameters for virtual synchronous generator control are determined by generating ΔP / ΔF characteristics, this is not a limitation. It can be configured, for example, to install a power distribution system model (digital twin) of substation 20 or less within the CEMS 31, generating the information needed to calculate each control parameter, so that the power distribution system model can be used to optimally operate in the envisioned application case. Alternatively, it can be configured to install AI or similar devices to calculate the control parameters.

[0549] In embodiments 1 and 2, the communication cycle between CEMS 31 and DSO 21 is set to 30 minutes, and the communication cycle between CEMS 31 and each power conversion device 41 is set to 5 minutes, but it is not limited to this. For example, the communication cycle between CEMS 31 and each power conversion device 41 can be set to 1 minute or less.

[0550] Furthermore, in embodiments 1 and 2, although the speed controller model in the speed controller control circuit 833 is modeled as a first-order hysteresis system, it is not limited to this. Needless to say, using a second-order hysteresis system, an LPF (Low Pass Filter), etc., will achieve the same effect.

[0551] Furthermore, in implementation methods 1 and 2, although using Figure 16 The integrator and feedback loop shown are used to model the operational circuit of the particle system, but it is not limited to this. For example, it can also be modeled using a first-order lag system, a second-order lag system, an LPF, etc.

[0552] Furthermore, in embodiments 1 and 2, although the explanation of VQ control, which is frequently implemented in virtual synchronous generator control, has been omitted for simplicity, it goes without saying that the same effect can be obtained by using this method on power conversion devices that are also equipped with VQ control for virtual synchronous generator control. Moreover, the structure of the mass system operation circuit 837 is not limited to... Figure 16 The structure shown.

[0553] Explanation of variations.

[0554] Furthermore, in embodiments 1 and 2, to facilitate understanding, it is explained that the control circuits of the power conversion device 27 for large solar power plants and the power conversion device 41 for batteries are configured as follows: Figures 6 to 16 The structure shown represents the structure of CEMS 31 as follows: Figures 3-5The diagram illustrates a hardware (H / W) configuration, but the same control functionality can be achieved even using software (S / W) installed on the CPU (Central Processing Unit) to implement the functions described in each block, or some blocks. Alternatively, the same control functionality can be achieved, at least for a portion of the blocks, through functional division of software and hardware.

[0555] It should be understood that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of this disclosure is not shown by the foregoing description, but by the claims, and is intended to include all modifications in the same sense and scope as the claims.

[0556] Figure Labels

[0557] 11: Communication circuit; 12: Storage circuit; 13, 88: Control parameter generation circuit; 14: Operation plan creation circuit; 15: Data transmission generation circuit; 16: Control circuit; 20: Substation; 21: Distribution automation system (DSO); 22, 201, 206, 210, 401, 406, 410: Voltmeter; 23: Automatic voltage regulator (SVR); 24: Power distribution system; 25: Communication line; 26: Large solar power plant; 27: Power conversion device for large solar power plant; 28: Switch; 29: Impedance; 30: Synchronous generator; 31: CEMS; 40, 40a~40c: System battery; 41, 41a~40c: Battery power conversion device; 5 1: MPPT control circuit; 52: Voltage control circuit; 53: First switching circuit; 54: Fifth control circuit; 60: Current control circuit; 61, 810: Phase detection circuit; 62: First sine wave generation circuit; 63, 66, 101, 832, 836, 852: Subtractors; 64: First PI control circuit; 65, 91, 103: Multipliers; 67: Sixth control circuit; 68: Second PI control circuit; 69: First PWM converter; 71: Charging control circuit; 72: Discharging control circuit; 73: Second switching circuit; 74: Seventh control circuit; 81: AC frequency detection circuit; 82: Effective power calculation circuit; 83: Virtual synchronous generator control circuit; 84: Inverter circuit. 85: Inverter voltage control circuit; 86: 3rd switching circuit; 87: 8th control circuit; 89: Switching frequency calculation circuit; 90: Dead time detection circuit; 92: First-order lag system model; 93: Limiter circuit; 102: Integrator; 104: Divider; 105, 835: Adder; 106: Phase calculation circuit; 100a~100d: Town; 110: Factory; 135: 3rd management circuit; 131: Reference ΔP / ΔF characteristic calculation circuit; 132: ΔP / ΔF characteristic calculation circuit; 136: Control circuit; 141: Battery operation plan creation circuit; 142: Power generation prediction circuit; 143: Power consumption prediction circuit; 144: Battery operation plan Correction circuit; 145: First management circuit; 146: Second management circuit; 202, 207, 211, 402, 407, 411: Ammeters; 203: First DC / DC converter; 204: First control circuit; 205, 405: DC bus; 208: First DC / AC converter; 209: Second control circuit; 212, 412: Communication I / F; 403: Second DC / DC converter; 404: Third control circuit; 408: Second DC / AC converter; 409: Fourth control circuit; 811: Frequency detection circuit; 812: Second sine wave generation circuit; 833: Speed ​​controller control circuit; 837: Mass system operation circuit; 851: Third sine wave generation circuit;853: 3rd PI control circuit; 854: 2nd PWM converter; 855: 1st current limiting circuit; 600: Load.

Claims

1. A power conversion device connected to an AC system, equipped with virtual synchronous generator control, the power conversion device comprising: The converter transforms the first DC voltage output from the distributed power source into a second DC voltage; The inverter converts the second DC voltage output from the converter into an AC voltage and outputs it to the AC system; The communication circuit receives information required for the control of the virtual synchronous generator, as notified from the management device that manages the distributed power source. The first voltmeter measures the second DC voltage; The second voltmeter measures the AC system voltage of the AC system. Converter control circuit, which controls the converter; A virtual synchronous generator control circuit enables the inverter to possess the transient characteristics of a synchronous generator; and The inverter control circuit controls the inverter as a voltage source based on the AC system voltage information input from the virtual synchronous generator control circuit. The information required for the control of the virtual synchronous generator includes the target power value of the power conversion device. The virtual synchronous generator control circuit calculates the switching frequency at which the charging and discharging of the distributed power source is switched based on the information required for controlling the virtual synchronous generator. The converter control circuit uses the switching frequency to create a frequency range for the AC system voltage and controls the distributed power source to have zero charge / discharge power within the frequency range. The frequency range of the AC system voltage is used to provide a dead zone in the drooping characteristics of the power conversion device that makes the charge / discharge power of the distributed power source zero, or to provide hysteresis for the switching of the charge / discharge of the distributed power source.

2. The power conversion device according to claim 1, wherein... The virtual synchronous generator control circuit includes: The speed governor control circuit simulates the speed governor function of a synchronous generator; and The particle system computing circuit simulated the oscillation equation of the synchronous generator. The speed controller circuit calculates the offset value to be applied to the target power value based on the reference frequency and frequency of the AC system voltage, and outputs the sum of the target power value and the offset value to the mass system calculation circuit. The particle system operation circuit generates the frequency and phase of the AC system voltage in such a way that the deviation between the effective power of the AC system and the summation value is zero, and outputs them to the inverter control circuit.

3. The power conversion device according to claim 1 or 2, wherein... The inverter control circuit generates a target AC voltage based on the AC system voltage information input from the virtual synchronous generator control circuit, and controls the inverter as a voltage source based on the generated target AC voltage and the AC system voltage measured by the second voltmeter.

4. The power conversion device according to any one of claims 1 to 3, wherein The converter control circuit controls the charging and discharging power of the distributed power source in such a way that the second DC voltage measured by the second voltmeter is a predetermined voltage, and controls the charging and discharging power of the distributed power source to be zero when the frequency of the AC system voltage is within the frequency range.

5. The power conversion device according to any one of claims 1 to 4, wherein When the charging / discharging power of the distributed power source is detected to be zero, the converter control circuit determines that the frequency of the AC system voltage falls within the frequency range and controls the distributed power source to have zero charging / discharging power. When the frequency of the AC system voltage is detected to be outside the frequency range, the converter control circuit controls the distributed power source to resume charging / discharging.

6. The power conversion device according to any one of claims 1 to 5, further comprising: An AC frequency detection circuit that detects the frequency of the AC system voltage. Based on the detection results of the AC frequency detection circuit, the converter control circuit detects that the frequency of the AC system voltage is outside the frequency range.

7. The power conversion device according to claim 2, wherein... The converter control circuit detects that the frequency of the AC system voltage is outside the frequency range based on the sum of the values ​​input to the particle system operation circuit or the frequency information of the AC system voltage output from the particle system operation circuit.

8. The power conversion device according to claim 2, wherein The converter control circuit detects that the frequency of the AC system voltage falls within the frequency range based on the sum of the inputs to the mass system operation circuit or the frequency information of the AC system voltage output from the mass system operation circuit.

9. The power conversion device according to any one of claims 1 to 8, further comprising: An ammeter is used to measure the alternating current of the AC system. as well as The effective power calculation circuit calculates the effective AC power output by the inverter based on the measurements from the ammeter and the second voltmeter. The virtual synchronous generator control circuit calculates the sluggishness characteristic of the power conversion device based on the inverter capacity, the target power value, and the control parameters used for controlling the virtual synchronous generator. The descent characteristic represents the relationship between the frequency difference between the AC voltage output by the inverter and the reference frequency of the AC system voltage, and the difference between the effective AC power and the target power value. The virtual synchronous generator control circuit uses the descent characteristic to calculate the switching frequency.

10. The power conversion device according to claim 9, wherein When the power target value corresponds to the discharge of the distributed power source, the converter control circuit uses the switching frequency as the lower limit frequency of the frequency range to control the distributed power source so that its discharge power is zero within the frequency range. When the target power value corresponds to the charging of the distributed power source, the converter control circuit uses the switching frequency as the upper limit of the frequency range to control the distributed power source so that its charging power is zero within the frequency range. When the power target value is zero, the converter control circuit sets the switching frequency to zero, sets the frequency range centered on the switching frequency, and controls the distributed power source to have zero charging and discharging power within the frequency range.

11. The power conversion device according to claim 9, wherein When the distributed power source is switched from discharging to charging, the converter control circuit controls the charging power of the distributed power source to zero until the frequency of the AC voltage output by the inverter exceeds the frequency obtained by adding the hysteresis width to the switching frequency. When the distributed power source is switched from charging to discharging, the converter control circuit controls the charging power of the distributed power source to zero until the frequency of the AC voltage output by the inverter becomes less than the frequency obtained by subtracting the hysteresis width from the switching frequency.

12. The power conversion device according to any one of claims 1 to 11, wherein The converter control circuit receives information from the management device related to the width of the dead zone or the width of the hysteresis.

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