Power conversion system, metering method

Abstract

To measure power derived from renewable energy with high accuracy.SOLUTION: A plurality of DC power measurement units (16a-16c) are connected between a plurality of dispersion type power supplies (6-8) and a plurality of DC / DC converters (11a-11c) respectively. An AC power measurement unit (15) is connected between an inverter (12) and a distribution board (3). A power generation device (6) for converting renewable energy into electric energy and a power storage device (7 or 8) are included in the plurality of dispersion type power supplies (6-8). A control unit (13) calculates a proportional division ratio of a plurality power measured by the plurality of DC power measurement units (16a-16c) in a period when current flows from the inverter (12) to a direction of the distribution board (3), and measures a power generation amount of the power generation device (6) based on the proportional division ratio and power measured by the AC power measurement unit (15).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power conversion system connected to a distributed power source and a metering method.

Background Art

[0002] In order to suppress global warming and realize a low-carbon and decarbonized society, the movement to reduce greenhouse gas emissions such as carbon dioxide is expanding. In Japan, the J-Credit system was launched in April 2013. The J-Credit system is a system in which the state certifies the reduction or absorption amount of greenhouse gas emissions as credits. The certified credits are securitized as environmental values and become a trading target. J-Credit includes credits derived from renewable energy. Credits derived from renewable energy are those that securitize the environmental value of electricity generated from renewable energy (for example, solar power, wind power, hydropower, etc.). In addition, as a certificate similar to credits derived from renewable energy, Japan Nature Conservation Energy Co., Ltd. has obtained certification from a third-party certification body and issues green power certificates.

[0003] In Japan, the Feed-in Tariff (FIT) system for renewable energy was launched in July 2012, and the spread of solar power generation systems has expanded. By using the Feed-in Tariff system, users can sell the surplus of the electricity generated by the solar power generation system to the power company at a fixed price. The environmental value is added to this fixed price.

[0004] Conventionally, the portion of the electricity generated by the solar power generation system for self-consumption has basically not been manifested as an environmental value. In recent years, a movement has been started to securitize the environmental value of the portion of the electricity generated by the solar power generation system for self-consumption and create credits.

[0005] The purchase price under the feed-in tariff system has been decreasing year by year, and the need to self-consume electricity generated by solar power systems is increasing. Accordingly, systems that link solar power generation systems and energy storage systems (hereinafter referred to as hybrid energy storage systems (also called integrated generation and storage systems)) are becoming widespread (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-118209 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the case of solar power generation systems, reverse power flow and self-consumption can be measured relatively easily and with high accuracy. In the case of hybrid energy storage systems, the discharged power from the battery is a mixture of power originating from solar cells (charged by the solar cells) and power originating from the grid (charged by the grid). Therefore, it becomes difficult to accurately measure the power originating from solar cells within the self-consumption.

[0008] This disclosure is made in light of these circumstances, and its purpose is to provide a power conversion system and a metering method that can accurately measure electricity derived from renewable energy. [Means for solving the problem]

[0009] To solve the above problems, a power conversion system in one aspect of the present disclosure comprises: a plurality of DC / DC converters connected to a plurality of distributed power sources, a inverter whose DC side is connected to the confluence point of the plurality of DC / DC converters and whose AC side is connected to a distribution board connected to a power grid and loads; a plurality of DC power meters connected between the plurality of distributed power sources and the plurality of DC / DC converters, a AC power meter connected between the inverter and the distribution board; and a control unit that acquires the power measured from the plurality of DC power meters and the AC power meter, respectively. The plurality of distributed power sources include a power generation device that converts renewable energy into electrical energy and an energy storage device. The control unit calculates the apportionment ratio of the plurality of powers measured by the plurality of DC power meters during the period when current flows from the inverter towards the distribution board, and measures the amount of power generated by the power generation device based on the apportionment ratio and the power measured by the AC power meter.

[0010] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between devices, systems, methods, computer programs, etc., are also valid forms of this disclosure. [Effects of the Invention]

[0011] According to this disclosure, electricity derived from renewable energy sources can be measured with high precision. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram illustrating the power conversion system according to Embodiment 1. [Figure 2] This diagram schematically shows the environmental value of the power generation amount of a solar cell, the discharge amount of a stationary battery, and the discharge amount of an on-board battery according to Embodiment 1. [Figure 3] This is a diagram illustrating the power conversion system according to Embodiment 2. [Modes for carrying out the invention]

[0013] (Embodiment 1) Figure 1 is a diagram illustrating a power conversion system 1 according to Embodiment 1. Multiple distributed power sources are connected to the power conversion system 1. In this embodiment, a solar cell 6, a stationary battery 7, and an on-board battery 8 are connected as multiple distributed power sources.

[0014] The power conversion system 1 is an integrated power conversion system (also called a Power Station®) that combines the power conditioner function for the solar cell 6, the power conditioner function for the stationary battery 7, and the power conditioner function for the vehicle battery 8. The power conversion system 1 mainly comprises a first DC / DC converter 11a, a second DC / DC converter 11b, a third DC / DC converter 11c, an inverter 12, and a control unit 13.

[0015] Solar cell 6 utilizes the photovoltaic effect to directly convert light energy into DC power. As solar cell 6, heterojunction solar cells, polycrystalline silicon solar cells, monocrystalline silicon solar cells, thin-film silicon solar cells, compound semiconductor solar cells, etc., can be used.

[0016] The solar cell 6 is connected to the first DC / DC converter 11a and outputs the generated power to the first DC / DC converter 11a. The first DC / DC converter 11a is connected between the solar cell 6 and the DC bus Bd and is a converter that can adjust the voltage of the DC power output from the solar cell 6. The first DC / DC converter 11a can be configured, for example, as a boost chopper.

[0017] The stationary battery 7 is capable of charging and discharging power and is composed of lithium-ion batteries, nickel-metal hydride batteries, etc. The stationary battery 7 is connected to a second DC / DC converter 11b and its charging and discharging are controlled by the second DC / DC converter 11b. The second DC / DC converter 11b is a bidirectional DC / DC converter connected between the stationary battery 7 and the DC bus Bd, which charges and discharges the stationary battery 7.

[0018] The in-vehicle battery 8 is a drive battery mounted on an electric vehicle and is composed of a lithium-ion battery, a nickel-metal hydride battery, etc. The electric vehicle and the power conversion system 1 are connected by a charging cable. When the electric vehicle is parked at home, the in-vehicle battery 8 is connected to the third DC / DC converter 11c and is controlled for charging and discharging by the third DC / DC converter 11c. The third DC / DC converter 11c is connected between the in-vehicle battery 8 and the DC bus Bd and is a bidirectional DC / DC converter that charges and discharges the in-vehicle battery 8 when the electric vehicle is parked at home.

[0019] In addition, a stationary or in-vehicle battery can also be substituted with a capacitor such as an electric double layer capacitor or a lithium-ion capacitor. In this specification, the battery and the capacitor are collectively referred to as an energy storage device.

[0020] The inverter 12 is connected between the DC bus Bd and the distribution board 3. The first DC / DC converter 11a - the third DC / DC converter 11c are connected in parallel to the DC bus Bd. The inverter 12 converts the DC power supplied from at least one of the first DC / DC converter 11a, the second DC / DC converter 11b, and the third DC / DC converter 11c via the DC bus Bd into AC power and outputs the converted AC power to the distribution board 3. At that time, the inverter 12 can control the voltage or current of the output AC power.

[0021] Also, the inverter 12 can convert the AC power supplied from the commercial power system 2 (hereinafter simply referred to as the system 2) via the distribution board 3 into DC power and output the converted DC power to the second DC / DC converter 11b or the third DC / DC converter 11c. The distribution board 3 is connected to the system 2 and the in-house load 4. The in-house load 4 is a general term for the loads installed in the house.

[0022] It is desirable to use the first DC / DC converter 11a - the third DC / DC converter 11c and the inverter 12 with the same or as close as possible conversion efficiency.

[0023] The control unit 13 controls the entire power conversion system 1. The control unit 13 can be realized through the cooperation of hardware and software resources, or solely through hardware resources. Hardware resources can include analog elements, microcontrollers, DSPs, ROMs, RAMs, ASICs, FPGAs, and other LSIs. Software resources can include programs such as firmware.

[0024] The control unit 13 performs Maximum Power Point Tracking (MPPT) control of the solar cell 6 by controlling the first DC / DC converter 11a. Specifically, the control unit 13 estimates the power generated by the solar cell 6 by measuring the input voltage and input current of the first DC / DC converter 11a, which are the output voltage and output current of the solar cell 6. Based on the measured output voltage of the solar cell 6 and the estimated power generated, the control unit 13 generates a voltage command value to set the power generated by the solar cell 6 to its maximum power point (optimal operating point). For example, the control unit 13 searches for the maximum power point by changing the operating point voltage in predetermined step widths according to the hill-climbing method and generates a voltage command value to maintain the maximum power point. The first DC / DC converter 11a switches in response to a drive signal based on the generated voltage command value.

[0025] The control unit 13 controls the second DC / DC converter 11b to control the charging and discharging of the stationary battery 7. Based on the current command value or voltage command value set by the control unit 13, the second DC / DC converter 11b performs constant current (CC) discharge, constant voltage (CV) discharge, constant current charge, or constant voltage charge of the stationary battery 7. When operating the stationary battery 7 to track at least one of the power generation amount of the solar cell 6 and the power consumption amount of the household load 4, the control unit 13 generates the current command value for the second DC / DC converter 11b according to the voltage of the DC bus Bd.

[0026] The control unit 13 can control the charging and discharging of the on-board battery 8 by controlling the third DC / DC converter 11c. The control unit 13 can communicate with the BMU (Battery Management Unit) of the on-board battery 8 via the communication line in the charging cable. In the case of CHAdeMO (registered trademark), the connection is made via CAN (Controller Area Network). The third DC / DC converter 11c performs constant current discharge, constant voltage discharge, constant current charge, or constant voltage charge of the on-board battery 8 based on the current command value or voltage command value set by the control unit 13 or the BMU of the on-board battery 8.

[0027] The control unit 13 controls the inverter 12 so that the voltage of the DC bus Bd maintains a target value. Specifically, the control unit 13 measures the voltage of the DC bus Bd and generates a current command value to match the measured bus voltage to the target value. If the voltage of the DC bus Bd is higher than the target value, the control unit 13 generates a current command value to increase the output power of the inverter 12, and if the voltage of the DC bus Bd is lower than the target value, it generates a current command value to decrease the output power of the inverter 12. The inverter 12 switches according to the drive signal based on the generated current command value.

[0028] The power supply circuit 14 converts the AC power supplied to the distribution line between the inverter 12 and the distribution board 3 into DC power, and steps it down to a predetermined voltage value to generate a control power supply voltage. For example, the power supply circuit 14 converts the 202±20V AC voltage of system 2 into a 24V DC voltage (control power supply voltage). The power supply circuit 14 supplies the generated control power supply voltage to various loads in the power conversion system 1 (for example, the drive circuits included in the first DC / DC converter 11a, the third DC / DC converter 11c, and the inverter 12). The power supply circuit 14 further steps down the control power supply voltage to generate the power supply voltage (for example, 5V) for the control unit 13 and supplies it to the control unit 13.

[0029] The external connection management device 17 may be a power detection unit, a remote control setting device, or a HEMS (Home Energy Management System) controller. The external connection management device 17 and the main unit of the power conversion system 1 may be connected by a wired connection (e.g., a cable conforming to the RS-485 standard) or by a wireless connection (e.g., Wi-Fi®, low-power wireless). The external connection management device 17 is connected to the router device 20. The external connection management device 17 and the router device 20 are connected by a wired connection (e.g., a LAN cable) or a wireless connection (e.g., Wi-Fi).

[0030] A monitor (not shown) can be connected to the external connection management device 17. The external connection management device 17 and the monitor may be connected directly or via the router device 20. The monitor can display the amount of electricity generated, purchased electricity, sold electricity, electricity usage, electricity rates by time of day, and operating mode of the solar power generation system. This information can also be displayed on the screen of an information terminal (e.g., smartphone, tablet, PC, etc.) owned by a user connected to the router device 20 wirelessly or via a wired connection.

[0031] The external connection management device 17 or monitor may include a recording medium. In that case, the power consumption measurement data can be saved as log data on the recording medium. The recording medium may be built-in or a removable recording medium.

[0032] The external connection management device 17 functions as a gateway for connecting to the external network 9. Network 9 is a general term for communication paths such as the Internet, dedicated lines, and VPNs (Virtual Private Networks), and is not limited to any particular communication medium or protocol. Examples of communication mediums that can be used include fiber optic networks, ADSL networks, CATV networks, mobile communication networks, wireless LANs, and wired LANs. Examples of communication protocols that can be used include TCP (Transmission Control Protocol) / IP (Internet Protocol), UDP (User Datagram Protocol) / IP, and Ethernet (registered trademark).

[0033] A smart meter 5, acting as an AC power meter, is connected between system 2 and distribution board 3. The smart meter 5 is equipped with a voltage sensor and a current sensor, and measures power by multiplying the system voltage measured by the voltage sensor by the current measured by the current sensor. The smart meter 5 can measure the cumulative amount of power at predetermined intervals (for example, every 30 minutes). It can measure both forward and reverse power flow. The smart meter 5 is equipped with a communication function and can transmit the cumulative amount of power at predetermined intervals to the retail electricity provider server 40 via the network 9. The smart meter 5 can also transmit the measured power to the external connection management device 17 in real time.

[0034] An AC power meter 15 is connected between the inverter 12 and the distribution board 3. More specifically, the AC power meter 15 is installed on the distribution line between the inverter 12 and the distribution board 3, on the distribution board 3 side of the branching point N2 of the power circuit 14. The AC power meter 15 is equipped with a voltage sensor and a current sensor, and measures the output power or input power of the power conversion system 1 by multiplying the output voltage or input voltage of the power conversion system 1 measured by the voltage sensor with the output current or input current of the power conversion system 1 measured by the current sensor. The AC power meter 15 outputs the measured output power or input power of the power conversion system 1 to the control unit 13. Note that the multiplication may be performed by the control unit 13.

[0035] AC power meters 15 consist of measuring instruments used for specific measurements (hereinafter referred to as "specific measuring instruments"). In Japan, the Energy Supply Resilience Act was enacted in June 2020. The Energy Supply Resilience Act includes a specific measurement system to create an environment for promoting the utilization of distributed resources. The specific measurement system is a system that, under certain conditions, exceptionally permits the use of measuring instruments that do not undergo verification under the Measurement Act. Businesses that have submitted a prior notification (such as aggregators) can receive an exemption from the provisions of the Measurement Act for new transactions that utilize distributed resources such as households (e.g., solar power generation, EVs), but only for those notified transactions.

[0036] Businesses are required to ensure the accuracy of the specified measuring instruments they use and to be accountable to consumers (such as households) in order to ensure proper measurement and protect consumers. Power conditioners are also subject to the category of specified measuring instruments. Specified measuring instruments are designed so that those who intend to conduct new electricity transactions can flexibly select the tolerance during use from seven levels ranging from 0.9% to 10%, taking into account the needs of the trading parties, the scale of the transaction, and the intended use. Tolerance refers to the permissible difference expressed as the absolute value of the ratio of the measured value minus the true value to the true value. For example, if the n3 class is selected, the tolerance at the time of inspection is set at 2.0%, and the tolerance during use is set at 3.0%. The n3 class is a class in which transactions can be conducted via the transmission network of general transmission and distribution businesses without being accountable to the trading partner, regardless of the scale of the transaction.

[0037] A first DC power meter 16a is connected between the solar cell 6 and the first DC / DC converter 11a. The first DC power meter 16a is equipped with a voltage sensor and a current sensor, and measures the output power of the solar cell 6 by multiplying the output voltage of the solar cell 6, measured by the voltage sensor, by the output current of the solar cell 6, measured by the current sensor. The first DC power meter 16a outputs the output power of the solar cell 6 to the control unit 13. Note that the multiplication may be performed by the control unit 13.

[0038] A second DC power meter 16b is connected between the stationary battery 7 and the second DC / DC converter 11b. The second DC power meter 16b is equipped with a voltage sensor and a current sensor, and measures the charging power or discharging power of the stationary battery 7 by multiplying the charging voltage or discharging voltage of the stationary battery 7 measured by the voltage sensor with the charging current or discharging current of the stationary battery 7 measured by the current sensor. The second DC power meter 16b outputs the charging power or discharging power of the stationary battery 7 to the control unit 13. Note that the multiplication may be performed by the control unit 13.

[0039] A third DC power meter 16c is connected between the on-board battery 8 and the third DC / DC converter 11c. The third DC power meter 16c is equipped with a voltage sensor and a current sensor, and measures the charging power or discharging power of the on-board battery 8 by multiplying the charging voltage or discharging voltage of the on-board battery 8 measured by the voltage sensor with the charging current or discharging current of the on-board battery 8 measured by the current sensor. The third DC power meter 16c outputs the charging power or discharging power of the stationary battery 7 to the control unit 13. Note that the multiplication may be performed by the control unit 13.

[0040] Note that in Figure 1, for the sake of simplification, the voltage sensors for measuring the control voltages of the first DC / DC converter 11a, the third DC / DC converter 11c, and the inverter 12, as well as the current sensors for measuring the control currents, are omitted. In some control applications, the voltage or current values ​​measured by a specific measuring instrument may be used.

[0041] During the output period of the power conversion system 1 in which current flows from the inverter 12 to the distribution board 3, if the stationary battery 7 and the vehicle-mounted battery 8 are not being charged or discharged, the control unit 13 uses the power measured by the AC power meter 15 as the power generated by the solar cell 6, and calculates the amount of power generated by the solar cell 6 by integrating the power generated by the solar cell 6 for a predetermined period.

[0042] During the power conversion system 1's output period, if the stationary battery 7 and the vehicle-mounted battery 8 are charging, the control unit 13 uses the power measured by the AC wattmeter 15 as the power generated by the solar cell 6 (excluding the amount stored), and calculates the amount of power generated by the solar cell 6 (excluding the amount stored) by accumulating the power generated by the solar cell 6 (excluding the amount stored) over a predetermined period. As will be described later, the portion of the power generated by the solar cell 6 that is stored in the stationary battery 7 or the vehicle-mounted battery 8 becomes apparent as power generated when it is discharged from the stationary battery 7 or the vehicle-mounted battery 8.

[0043] During the power conversion system 1's output period, if the stationary battery 7 or the vehicle-mounted battery 8 is discharging, the control unit 13 calculates the apportionment ratio of the multiple powers measured by the first DC wattmeter 16a to the third DC wattmeter 16c. The following explanation assumes that the stationary battery 7 and the vehicle-mounted battery 8 are not charging or discharging simultaneously. Based on this apportionment ratio and the power measured by the AC wattmeter 15, the control unit 13 calculates the power generated by the solar cell 6.

[0044] For example, if the output power of solar cell 6, the discharge power of stationary battery 7, and the discharge power of on-board battery 8 are in a ratio of 1:1:0, the control unit 13 multiplies the power measured by the AC wattmeter 15 by 1 / 2 to calculate the power generated by solar cell 6 (excluding power via the energy storage device). The control unit 13 then calculates the amount of power generated by solar cell 6 (excluding power via the energy storage device) by accumulating the power generated by solar cell 6 (excluding power via the energy storage device) over a predetermined period.

[0045] The control unit 13 calculates the amount of electricity consumed by the household load 4 from the amount of electricity generated by the solar cell 6, based on the amount of electricity obtained from the smart meter 5 via the external connection management device 17 and the amount of electricity generated by the solar cell 6. During the electricity purchase period (forward power flow period), the entire amount of electricity generated by the solar cell 6 is considered self-consumption. During the electricity sales period (reverse power flow period), the control unit 13 subtracts the reverse power flow amount obtained from the smart meter 5 from the amount of electricity generated by the solar cell 6 to calculate the self-consumption of the amount of electricity generated by the solar cell 6. If the stationary battery 7 or the vehicle battery 8 is discharging, the control unit 13 needs to subtract from the amount of electricity generated by the solar cell 6 the reverse power flow amount obtained from the smart meter 5, which has been corrected by multiplying the reverse power flow amount obtained from the smart meter 5 by the apportionment ratio of the amount of electricity generated by the solar cell 6 (excluding that via the energy storage device).

[0046] During the charging period of the stationary battery 7, the control unit 13 records the cumulative amount of power measured by the second DC power meter 16b as grid-derived energy during periods when the power measured by the first DC power meter 16a is zero. During the charging period of the stationary battery 7, the control unit 13 records the cumulative amount of power measured by the second DC power meter 16b as solar-derived energy during periods when the power measured by the AC power meter 15 is zero or is output from the power conversion system 1 to the distribution board 3.

[0047] During the charging period of the stationary battery 7, the control unit 13 calculates the apportionment ratio of the power measured by the first DC power meter 16a to the power measured by the AC power meter 15 when the power measured by the first DC power meter 16a is not zero and the power measured by the AC power meter 15 is in the direction of input from the distribution board 3 to the power conversion system 1. The control unit 13 calculates and records the amount of energy derived from the solar cell by multiplying the cumulative amount of power measured by the second DC power meter 16b by the ratio of the power measured by the first DC power meter 16a. The control unit 13 calculates and records the amount of energy derived from the grid by multiplying the cumulative amount of power measured by the second DC power meter 16b by the ratio of the power measured by the AC power meter 15.

[0048] In this way, during the charging period of the stationary battery 7, the control unit 13 records the capacity of the stationary battery 7, classifying it into capacity derived from the solar cell and capacity derived from the grid, based on the power measured by the first DC power meter 16a, the third DC power meter 16c, and the AC power meter 15, respectively.

[0049] The control unit 13 calculates the apportionment ratio of multiple powers measured by the first DC wattmeter 16a to the third DC wattmeter 16c when the stationary battery 7 is discharging during the output period of the power conversion system 1. Based on this apportionment ratio and the power measured by the AC wattmeter 15 during the output period of the power conversion system 1, the control unit 13 calculates the discharge power of the stationary battery 7. The control unit 13 calculates the discharge amount of the stationary battery 7 by integrating the discharge power of the stationary battery 7 over a predetermined period.

[0050] The control unit 13 calculates the total capacity derived from the solar cells and the capacity derived from the grid that was charged to the stationary battery 7 during a predetermined period, and calculates the ratio of the solar cell-derived capacity to the total capacity charged during the predetermined period based on the calculated total capacity and the solar cell-derived capacity. The control unit 13 multiplies the amount of discharge from the stationary battery 7 during the discharge period by this ratio of solar cell-derived capacity to measure the amount of solar cell-derived discharge from the stationary battery 7 during the discharge period.

[0051] The control unit 13 calculates the amount of electricity consumed by the in-house load 4 from the solar cell discharge amount, based on the amount of electricity obtained from the smart meter 5 via the external connection management device 17 and the amount of discharge from the solar cell of the stationary battery 7. During the electricity purchase period (forward power flow period), the entire amount of discharge from the solar cell becomes the amount of self-consumption. During the electricity sales period (reverse power flow period), the control unit 13 calculates the amount of self-consumption of the solar cell discharge amount by subtracting the reverse power flow amount obtained from the smart meter 5 from the amount of discharge from the solar cell. If the solar cell 6 is generating electricity, the control unit 13 needs to subtract from the solar cell discharge amount a reverse power flow amount corrected by multiplying the reverse power flow amount obtained from the smart meter 5 by the apportionment ratio of the discharge amount of the stationary battery 7.

[0052] The control unit 13 can calculate the amount of discharge from the on-board battery 8 originating from the solar cell during a predetermined period, and the amount of self-consumption within that discharge, using the same calculation method as for the stationary battery 7. Note that the capacity of the on-board battery 8 decreases due to discharge associated with the operation of the electric vehicle and increases due to charging from an external charging facility.

[0053] The BMU of the on-board battery 8 records the amount of power consumed by the on-board battery 8 and the amount of power charged from an external charging facility during the period from when the connection with the power conversion system 1 via the charging cable is disconnected until the next time the charging cable is connected to the power conversion system 1 (hereinafter referred to as the isolation period). When the isolation period ends and the vehicle battery 8 is connected to the power conversion system 1 via the charging cable, the BMU of the on-board battery 8 transmits the amount of power consumed and the amount of power charged during the isolation period to the control unit 13 via the communication line in the charging cable.

[0054] The control unit 13 compares the amount of consumption and the amount of charge during the isolation period, and if the amount of charge is greater, it subtracts the amount of consumption from the amount of charge during the isolation period to calculate the net charge. The control unit 13 calculates the total of the capacity from the home solar panel, the capacity from the grid, and the net charge from external charging equipment that was charged to the on-board battery 8 during a predetermined period, and calculates the ratio of the capacity from the solar panel to the total capacity charged to the on-board battery 8 during the predetermined period based on the calculated total capacity and the capacity from the solar panel.

[0055] The control unit 13 outputs to the external connection management device 17 the amount of self-consumption of the power generated by the solar cell 6, the amount of self-consumption of the discharge amount originating from the solar cell of the stationary battery 7, and the amount of self-consumption of the discharge amount originating from the solar cell of the on-board battery 8 at predetermined intervals. The control unit 13 may also output to the external connection management device 17 the reverse power flow rate of the power generated by the solar cell 6, the reverse power flow of the discharge amount originating from the solar cell of the stationary battery 7, and the reverse power flow of the discharge amount originating from the solar cell of the on-board battery 8.

[0056] The external connection management device 17 transmits to the data server 30 via the network 9 the amount of electricity consumed by the solar cell 6, the amount of electricity consumed by the stationary battery 7 due to solar cell discharge, and the amount of electricity consumed by the vehicle battery 8 due to solar cell discharge, which were received from the main unit of the power conversion system 1.

[0057] The data server 30 is, for example, a server operated by the manufacturer of the power conversion system 1. The data server 30 may be a proprietary server installed in a data center or the company's own facilities, or it may be a cloud server based on a cloud service contract. The manufacturer or partner company of the power conversion system 1 collects the amount of self-consumption (including that via the energy storage device) derived from the amount of electricity generated by the solar cells 6 stored in the data server 30 and applies to the J-Credit Certification Committee. Once the application is approved, J-Credits are issued. This makes the amount of self-consumption derived from the amount of electricity generated by the solar cells 6 tangible as environmental value.

[0058] Figure 2 schematically shows the environmental value of the power generated by the solar cell 6, the discharge amount of the stationary battery 7, and the discharge amount of the vehicle-mounted battery 8 according to Embodiment 1. Of the power generated from the solar cell, the portion that is not consumed on-site but is fed back into the grid has its environmental value realized through other mechanisms such as the Feed-in Tariff (FIT) system.

[0059] The above description illustrates an example in which the control unit 13 of the power conversion system 1 calculates the amount of self-consumption of the power generated by the solar cell 6, the amount of self-consumption of the discharge amount originating from the solar cell of the stationary battery 7, and the amount of self-consumption of the discharge amount originating from the solar cell of the on-board battery 8 for each predetermined period. However, the calculation of the amount of self-consumption of the power generated by the solar cell 6, the amount of self-consumption of the discharge amount originating from the solar cell of the stationary battery 7, and the amount of self-consumption of the discharge amount originating from the solar cell of the on-board battery 8 for each predetermined period may be performed by the data server 30. In this case, the control unit 13 outputs the power measured by the first DC power meter 16a-3rd DC power meter 16c and AC power meter 15, respectively, to the external connection management device 17. The external connection management device 17 transmits the power measured by the first DC power meter 16a-3rd DC power meter 16c and AC power meter 15, respectively, received from the main unit of the power conversion system 1, to the data server 30 via the network 9.

[0060] As described above, according to Embodiment 1, the amount of electricity originating from the solar cell 6 can be measured with high accuracy by measuring the amount of electricity originating from the solar cell 6 based on the apportionment ratio of the power measured by the AC power meter 15 and the power measured by the first DC power meter 16a - third DC power meter 16c.

[0061] If the conversion efficiencies of the first DC / DC converter 11a and the third DC / DC converter 11c are the same or similar, the portion of the power measured by the AC wattmeter 15 that is the output power of the solar cell 6 and the portion that is the discharge power of the stationary battery 7 or vehicle battery 8 can be separated with high precision. The output power of the solar cell 6 and the discharge power of the stationary battery 7 or vehicle battery 8, calculated by apportioning the power measured by the AC wattmeter 15, exclude the conversion losses of the first DC / DC converter 11a, the second DC / DC converter 11b or the third DC / DC converter 11c, the conversion losses of the inverter 12, and the internal consumption of the power conversion system 1, so that the net amount of electricity consumed by the household load 4 can be measured.

[0062] Furthermore, by using specific measuring instruments for the AC power meter 15 and the first DC power meter 16a-third DC power meter 16c, the accuracy of the measurement of the self-consumption amount derived from the power generation amount of the solar cell 6, which is ultimately calculated, can be ensured.

[0063] (Embodiment 2) Figure 3 is a diagram illustrating the power conversion system 1 according to Embodiment 2. The power conversion system 1 according to Embodiment 2 differs from the power conversion system 1 according to Embodiment 2 shown in Figure 1 in that the installation positions of the first DC power meter 16a and the third DC power meter 16c are different.

[0064] In Embodiment 2, the first DC power meter 16a is connected between the first DC / DC converter 11a and the merging point N1 of the first DC / DC converter 11a and the third DC / DC converter 11c on the DC bus Bd. The second DC power meter 16b is connected between the second DC / DC converter 11b and the merging point N1. The third DC power meter 16c is connected between the third DC / DC converter 11c and the merging point N1.

[0065] During the charging period of the stationary battery 7, the control unit 13 calculates the apportionment ratio of the power measured by the first DC power meter 16a to the power measured by the AC power meter 15 during the period when the power measured by the first DC power meter 16a is not zero and the power measured by the AC power meter 15 is in the direction of input from the distribution board 3 to the power conversion system 1. The control unit 13 calculates and records the amount of power derived from the solar cell by multiplying the cumulative amount of power measured by the second DC power meter 16b by the ratio of the power measured by the first DC power meter 16a and the conversion efficiency of the second DC / DC converter 11b. The control unit 13 calculates and records the amount of power derived from the grid by multiplying the cumulative amount of power measured by the second DC power meter 16b by the ratio of the power measured by the AC power meter 15 and the conversion efficiency of the second DC / DC converter 11b. The same applies to the on-board battery 8. Other operations are the same as in Embodiment 1.

[0066] As described above, Embodiment 2 provides the same effects as Embodiment 1. In Embodiment 2, by installing the first DC power meter 16a and the third DC power meter 16c on the DC bus Bd side, the influence of the conversion loss of the first DC / DC converter 11a and the third DC / DC converter 11c can be removed from the power measured by the AC power meter 15. Therefore, even if there is variation in the conversion efficiency of the first DC / DC converter 11a and the third DC / DC converter 11c, the amount of power derived from the amount of power generated by the solar cell 6 can be measured with high accuracy.

[0067] The present disclosure has been described above based on embodiments. The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure.

[0068] In the above embodiment, an example was described in which a solar cell 6 is used as a power generation device that converts renewable energy into electrical energy. However, a wind turbine or a micro-hydroelectric generator can also be used instead of the solar cell 6. In this case, a rectifier is connected between the wind turbine or micro-hydroelectric generator and the first DC / DC converter 11a.

[0069] In the above embodiment, a power conversion system 1 to which a stationary battery 7 and an on-board battery 8 are connected has been described. However, a power conversion system 1 to which only one of either the stationary battery 7 or the on-board battery 8 is connected may also be described.

[0070] The embodiments may be specified by the following items.

[0071] [Item 1] Multiple DC / DC converters (11a-11c) connected to multiple distributed power sources (6-8), The DC side of the inverter (12) is connected to the junction point (N1) of the plurality of DC / DC converters (11a-11c), and the AC side is connected to a distribution board (3) which is connected to the power system (2) and load (4). Multiple DC power meters (16a-16c) are connected between the multiple distributed power sources (6-8) and the multiple DC / DC converters (11a-11c), respectively. An AC power meter (15) is connected between the inverter (12) and the distribution board (3), The system includes a control unit (13) that acquires the power measured from the plurality of DC power meters (16a-16c) and the AC power meter (15), respectively. The aforementioned multiple distributed power sources (6-8) include a power generation device (6) that converts renewable energy into electrical energy, and an energy storage device (7 or 8), The control unit (13) calculates the apportionment ratio of the multiple powers measured by the multiple DC power meters (16a-16c) during the period when current is flowing from the inverter (12) to the distribution board (3), and measures the amount of power generated by the power generator (6) based on the apportionment ratio and the power measured by the AC power meter (15). Power conversion system (1). According to this, the amount of power generated by the power generation device (6) can be measured with high precision. [Item 2] Multiple DC / DC converters (11a-11c) connected to multiple distributed power sources (6-8), The DC side of the inverter (12) is connected to the junction point (N1) of the plurality of DC / DC converters (11a-11c), and the AC side is connected to a distribution board (3) which is connected to the power system (2) and load (4). Multiple DC power meters (16a-16c) are connected between the multiple DC / DC converters (11a-11c) and the confluence point (N1), An AC power meter (15) is connected between the inverter (12) and the distribution board (3), The system includes a control unit (13) that acquires the power measured from the plurality of DC power meters (16a-16c) and the AC power meter (15), respectively. The aforementioned multiple distributed power sources (6-8) include a power generation device (6) that converts renewable energy into electrical energy, and an energy storage device (7 or 8). Power conversion system (1). According to this, the amount of power generated by the power generation device (6) can be measured with high precision. [Item 3] The control unit (13) calculates the apportionment ratio of the multiple powers measured by the multiple DC power meters (16a-16c) during the period when current is flowing from the inverter (12) to the distribution board (3), and measures the amount of power generated by the power generator (6) based on the apportionment ratio and the power measured by the AC power meter (15). The power conversion system described in item 2 (1). According to this, the amount of power generated by the power generation device (6) can be measured with high precision. [Item 4] The control unit (13) calculates the amount of electricity consumed by the load (4) from the amount of electricity generated by the power generator (6), based on the amount of electricity obtained from the AC power meter (5) connected between the power system (2) and the distribution board (3) and the amount of electricity generated by the power generator (6). A power conversion system as described in item 1 or 3 (1). According to this, the amount of electricity generated by the power generation device (6) that is consumed by the load (4) can be measured with high precision. [Item 5] The control unit (13) Based on the power measured by the multiple DC power meters (16a-16c) and the AC power meter (15) during the charging period of the energy storage device (7 or 8), the capacity stored in the energy storage device (7 or 8) is classified into the capacity originating from the power generation device (6) and the capacity originating from the power system (2). The apportionment ratio of the multiple powers measured by the multiple DC power meters (16a-16c) during the period when current flows from the inverter (12) towards the distribution board (3) is calculated, and the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8) is measured based on the apportionment ratio, the power measured by the AC power meter (15), and the ratio of the capacity originating from the power generator (6) to the capacity stored in the energy storage device (7 or 8). A power conversion system (1) as described in any one of items 1 to 4. According to this, the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8) can be measured with high precision. [Item 6] The control unit (13) calculates the amount of discharge consumed by the load (4) from the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8), based on the amount of energy obtained from the AC energy meter (5) connected between the power system (2) and the distribution board (3) and the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8). The power conversion system described in item 5 (1). According to this, the amount of discharge consumed by the load (4) out of the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8) can be calculated with high accuracy. [Item 7] The aforementioned multiple DC power meters (16a-16c) and the AC power meter (15) are specified measuring instruments. A power conversion system (1) as described in any one of items 1 through 6. According to this, the accuracy of the power measured by each of the multiple DC power meters (16a-16c) and AC power meters (15) can be ensured. [Item 8] A method for measuring distributed power sources connected to a power conversion system (1), The aforementioned power conversion system (1) is Multiple DC / DC converters (11a-11c) connected to multiple distributed power sources (6-8), The DC side is connected to the junction point (N1) of the plurality of DC / DC converters (11a-11c), and the AC side is connected to a distribution board (3) which is connected to the power system (2) and load (4), and the inverter (12) is connected to this distribution board (3). Multiple DC power meters (16a-16c) are connected between the multiple distributed power sources (6-8) and the multiple DC / DC converters (11a-11c), or between the multiple DC / DC converters (11a-11c) and the confluence point (N1), respectively. The system includes an AC power meter (15) connected between the inverter (12) and the distribution board (3), The aforementioned multiple distributed power sources (6-8) include a power generation device (6) that converts renewable energy into electrical energy, and an energy storage device (7 or 8), During the period when current flows from the inverter (12) to the distribution board (3), the apportionment ratio of the multiple powers measured by the multiple DC power meters (16a-16c) is calculated, and the amount of power generated by the power generator (6) is measured based on the apportionment ratio and the power measured by the AC power meter (15). Weighing method. According to this, the amount of power generated by the power generation device (6) can be measured with high precision. [Item 9] Based on the amount of electricity obtained from the AC power meter (5) connected between the power system (2) and the distribution board (3), and the amount of electricity generated by the power generator (6), the amount of electricity generated by the power generator (6) that is consumed by the load (4) is calculated. The weighing method described in item 8. According to this, the amount of electricity generated by the power generation device (6) that is consumed by the load (4) can be measured with high precision. [Item 10] Based on the power measured by the multiple DC power meters (16a-16c) and the AC power meter (15) during the charging period of the energy storage device (7 or 8), the capacity stored in the energy storage device (7 or 8) is classified into the capacity originating from the power generation device (6) and the capacity originating from the power system (2). The apportionment ratio of the multiple powers measured by the multiple DC power meters (16a-16c) during the period when current flows from the inverter (12) towards the distribution board (3) is calculated, and the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8) is measured based on the apportionment ratio, the power measured by the AC power meter (15), and the ratio of the capacity originating from the power generator (6) to the capacity stored in the energy storage device (7 or 8). The weighing method described in item 8 or 9. According to this, the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8) can be measured with high precision. [Item 11] Based on the amount of energy obtained from the AC power meter (5) connected between the power system (2) and the distribution board (3), and the amount of discharge originating from the power generator (6) discharged from the energy storage device (7 or 8), the amount of discharge consumed by the load (4) is calculated from the amount of discharge originating from the power generator (6) discharged from the energy storage device (7 or 8). The weighing method described in item 10. According to this, the amount of discharge consumed by the load (4) out of the amount of discharge originating from the power generator (6) that is discharged from the energy storage device (7 or 8) can be calculated with high accuracy. [Explanation of Symbols]

[0072] 1 Power conversion system, 2 System, 3 Distribution board, 4 In-house load, 5 Smart meter, 6 Solar cell, 7 Stationary battery, 8 Vehicle battery, 9 Network, 11a First DC / DC converter, 11b Second DC / DC converter, 11c Third DC / DC converter, 12 Inverter, 13 Control unit, 14 Power circuit, 15 AC power meter, 16a First DC power meter, 16b Second DC power meter, 16c Third DC power meter, 17 External connection management device, 20 Router device, 30 Data server, 40 Retail electricity provider server.

Claims

1. Multiple DC / DC converters connected to multiple distributed power sources, An inverter whose DC side is connected to the junction point of the multiple DC / DC converters, and whose AC side is connected to a distribution board connected to the power system and load, Multiple DC power meters connected between the multiple distributed power sources and the multiple DC / DC converters, An AC power meter connected between the inverter and the distribution board, The system comprises a control unit that acquires the power measured from the plurality of DC power meters and the AC power meter, respectively. The aforementioned multiple distributed power sources include power generation devices that convert renewable energy into electrical energy, and energy storage devices. The control unit calculates the apportionment ratio of the multiple powers measured by the multiple DC power meters during the period when current flows from the inverter towards the distribution board, and measures the amount of power generated by the power generation device based on the apportionment ratio and the power measured by the AC power meter. Based on the power measured by the multiple DC wattmeters and the AC wattmeter during the charging period of the energy storage device, the capacity stored in the energy storage device is classified into the capacity originating from the power generation device and the capacity originating from the power grid. The apportionment ratio of the multiple powers measured by the multiple DC power meters during the period when current flows from the inverter towards the distribution board is calculated, and the amount of discharge originating from the power generator that is discharged from the power storage device is measured based on the apportionment ratio, the power measured by the AC power meter, and the ratio of the capacity originating from the power generator to the capacity stored in the energy storage device. Power conversion system.

2. Multiple DC / DC converters connected to multiple distributed power sources, An inverter whose DC side is connected to the junction point of the multiple DC / DC converters, and whose AC side is connected to a distribution board connected to the power system and load, Multiple DC / DC converters and multiple DC power meters connected between the confluence point, An AC power meter connected between the inverter and the distribution board, The system comprises a control unit that acquires the power measured from the plurality of DC power meters and the AC power meter, respectively. The aforementioned multiple distributed power sources include power generation devices that convert renewable energy into electrical energy, and energy storage devices. The control unit calculates the apportionment ratio of the multiple powers measured by the multiple DC power meters during the period when current flows from the inverter towards the distribution board, and measures the amount of power generated by the power generation device based on the apportionment ratio and the power measured by the AC power meter. Based on the power measured by the multiple DC wattmeters and the AC wattmeter during the charging period of the energy storage device, the capacity stored in the energy storage device is classified into the capacity originating from the power generation device and the capacity originating from the power grid. The apportionment ratio of the multiple powers measured by the multiple DC power meters during the period when current flows from the inverter towards the distribution board is calculated, and the amount of discharge originating from the power generator that is discharged from the power storage device is measured based on the apportionment ratio, the power measured by the AC power meter, and the ratio of the capacity originating from the power generator to the capacity stored in the energy storage device. Power conversion system.

3. The control unit calculates the amount of electricity consumed by the load from the amount of electricity generated by the power generation device, based on the amount of electricity obtained from the AC power meter connected between the power system and the distribution board and the amount of electricity generated by the power generation device. The power conversion system according to claim 1 or 2.

4. Multiple DC / DC converters connected to multiple distributed power sources, An inverter whose DC side is connected to the junction point of the multiple DC / DC converters, and whose AC side is connected to a distribution board connected to the power system and load, Multiple DC / DC converters and multiple DC power meters connected between the confluence point, An AC power meter connected between the inverter and the distribution board, The system comprises a control unit that acquires the power measured from the plurality of DC power meters and the AC power meter, respectively. The aforementioned multiple distributed power sources include power generation devices that convert renewable energy into electrical energy, and energy storage devices. The control unit, Based on the power measured by the multiple DC wattmeters and the AC wattmeter during the charging period of the energy storage device, the capacity stored in the energy storage device is classified into the capacity originating from the power generation device and the capacity originating from the power grid. The apportionment ratio of the multiple powers measured by the multiple DC power meters during the period when current flows from the inverter towards the distribution board is calculated, and the amount of discharge originating from the power generator that is discharged from the power storage device is measured based on the apportionment ratio, the power measured by the AC power meter, and the ratio of the capacity originating from the power generator to the capacity stored in the energy storage device. Power conversion system.

5. The control unit calculates the amount of discharge consumed by the load from the amount of discharge originating from the power generator, based on the amount of energy obtained from the AC power meter connected between the power system and the distribution board, and the amount of discharge originating from the power generator discharged from the energy storage device. A power conversion system according to any one of claims 1 to 4.

6. The aforementioned multiple DC power meters and AC power meters are specified measuring instruments. A power conversion system according to any one of claims 1 to 5.

7. A method for measuring distributed power sources connected to a power conversion system, The aforementioned power conversion system, Multiple DC / DC converters connected to multiple distributed power sources, An inverter whose DC side is connected to the junction point of the multiple DC / DC converters, and whose AC side is connected to a distribution board connected to the power system and load, Multiple DC power meters connected between the multiple distributed power sources and the multiple DC / DC converters, or between the multiple DC / DC converters and the confluence point, The system includes an AC power meter connected between the inverter and the distribution board, The aforementioned multiple distributed power sources include power generation devices that convert renewable energy into electrical energy, and energy storage devices. During the period when current flows from the inverter towards the distribution board, the apportionment ratio of the multiple powers measured by the multiple DC power meters is calculated, and the amount of power generated by the power generation device is measured based on the apportionment ratio and the power measured by the AC power meter. Based on the power measured by the multiple DC wattmeters and the AC wattmeter during the charging period of the energy storage device, the capacity stored in the energy storage device is classified into the capacity originating from the power generation device and the capacity originating from the power grid. The apportionment ratio of the multiple powers measured by the multiple DC power meters during the period when current flows from the inverter towards the distribution board is calculated, and the amount of discharge originating from the power generator that is discharged from the power storage device is measured based on the apportionment ratio, the power measured by the AC power meter, and the ratio of the capacity originating from the power generator to the capacity stored in the energy storage device. Weighing method.

8. Based on the amount of electricity obtained from the AC power meter connected between the power system and the distribution board, and the amount of electricity generated by the power generation device, the amount of electricity generated by the power generation device that is consumed by the load is calculated. The weighing method according to claim 7.

9. Based on the amount of electricity obtained from the AC power meter connected between the power system and the distribution board, and the amount of discharge originating from the power generator discharged from the energy storage device, the amount of discharge consumed by the load is calculated from the amount of discharge originating from the power generator discharged from the energy storage device. The weighing method according to claim 7 or 8.

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