Power conversion equipment, distributed power systems

Abstract

To highly accurately and robustly measure electric energy in a power conversion device.SOLUTION: In a power conversion device (10), a voltage or a current supplied from a distributed power source (20) is converted by a power conversion unit (12) and outputted to a power system (2). Based on the voltage and the current outputted from the power conversion unit (12), a power conversion control unit (15a) generates a command value for controlling the power conversion unit (12). Based on the voltage and the current outputted from the power conversion unit (12), a specific measurement calculation unit (15b) calculates electric energy for specific measurement. A hardware system from detecting the voltage and the current outputted from the power conversion unit (12) to calculating the command value and a hardware system from detecting the voltage and the current outputted from the power conversion unit (12) to calculating the electric energy for specific measurement are provided partially or entirely independently.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device for converting power supplied from a distributed power source, and a distributed power source system. [Background technology]

[0002] As renewable energy gains attention, the use of solar power generation systems and energy storage systems is expanding. In Japan, the Energy Supply Resilience Act was enacted in June 2020. The Energy Supply Resilience Act includes a specified metering system to create an environment that promotes the use of distributed resources.

[0003] The specified measurement system is a system that, under certain conditions, allows the use of measuring instruments that do not undergo inspection under the Weights and Measurement Act as an exception. Businesses (aggregators, etc.) that have submitted prior notification can be exempted from the provisions of the Weights and Measurement Act for new transactions that utilize distributed resources such as households (for example, solar power generation, EVs). From the perspective of ensuring appropriate measurement and protecting consumers (households, etc.), businesses are required to ensure the accuracy of the measuring instruments they use and to be accountable to consumers.

[0004] Power conditioners are subject to the special metering system. Power conditioners connected to commercial power grids (see, for example, Patent Document 1) already detect current and voltage, so it is conceivable that the current detection unit, voltage detection unit, and microcontroller could be shared between power conversion control and calculation of the amount of power for special metering. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-158338 Summary of the Invention [Problem to be solved by the invention]

[0006] When the current detection unit, voltage detection unit, and microcontroller are shared, even if a discrepancy occurs in the detected voltage value or current value, it is difficult to recognize the discrepancy.

[0007] In the calibration of power conditioners during manufacturing, DC current is applied instead of AC current to detect DC leakage, and offset and gain errors in the current detector are detected. Adjustment values ​​to compensate for these errors are then calculated. However, the adjustment values ​​obtained by applying DC current are less accurate than those obtained by applying AC current.

[0008] In the specified measurement system, calculated values ​​of electric energy are used for monetary transactions, so high accuracy is required. Degree The calculated value of the amount of power is obtained.

[0009] The present disclosure has been made in view of these circumstances, and its purpose is to every time To provide a power conversion device and a distributed power supply system capable of measuring the amount of power. [Means for solving the problem]

[0010] In order to solve the above problems, a power conversion device according to one aspect of the present disclosure includes a power conversion unit that converts the voltage or current of power supplied from a distributed power source and outputs the converted power to a power grid, a power conversion control unit that generates a command value for controlling the power conversion unit based on the voltage and current output from the power conversion unit, and a specified meter calculation unit that calculates an amount of power for a specified meter based on the voltage and current output from the power conversion unit. A hardware system that detects the voltage and current output from the power conversion unit and calculates the command value, and a part or all of a hardware system that detects the voltage and current output from the power conversion unit and calculates the amount of power for the specified meter are provided independently. [Effects of the Invention]

[0011] According to the present disclosure, a power conversion device can measure the amount of power with high precision and robustness. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram for explaining a distributed power generation system according to an embodiment; [Figure 2] FIG. 2 is a diagram illustrating a first example of a power conversion control unit and a specific metric calculation unit according to an embodiment. [Figure 3] 10 is a flowchart showing the flow of a process for determining the measurement accuracy of the amount of electric power for a specific meter performed by the power conversion device according to the first embodiment. [Figure 4] FIG. 10 is a diagram illustrating a second example of a power conversion control unit and a specific metric calculation unit according to an embodiment. [Figure 5] 10 is a flowchart showing the flow of a calibration process for a hardware system for power conversion control. [Figure 6] 10 is a flowchart showing the flow of the calibration process for a hardware system for specific metrology. [Figure 7] FIG. 10 is a diagram for explaining the configuration of a power conversion device according to a first modification. [Figure 8] FIG. 10 is a diagram for explaining the configuration of a power conversion device according to a second modification. [Figure 9] 9(a) and 9(b) are diagrams comparing the system configuration of a distributed power supply system according to the embodiment with the system configuration of a conventional distributed power supply system. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 is a diagram illustrating a distributed power system 1 according to an embodiment. The distributed power system 1 according to the embodiment includes a distributed power source 20, a power conversion device 10, and an external connection management device 30. The distributed power source 20 corresponds to a solar cell, a stationary storage battery, an in-vehicle storage battery, a fuel cell, or the like.

[0014] In the following, in this embodiment, a solar cell is assumed as the distributed power source 20. A solar cell can convert light energy directly into DC power by utilizing the photovoltaic effect. As the solar cell, a heterojunction solar cell, a polycrystalline silicon solar cell, a single-crystalline silicon solar cell, a thin-film silicon solar cell, a compound solar cell, or the like can be used. When a solar cell is used as the distributed power source 20, the distributed power system 1 is a photovoltaic power generation system, and the power conversion device 10 is a power conditioner for the solar cell.

[0015] The power conversion device 10 according to the embodiment is a power conditioner with a built-in power metering function that complies with the specified metering system. The power conversion device 10 includes a DC / DC converter 11, an inverter 12, a first CT sensor 131a, a second CT sensor 131b, a first current detection unit 13a, a second current detection unit 13b, a first voltage detection unit 14a, a second voltage detection unit 14b, a power conversion control unit 15a, a specified metering calculation unit 15b, a system control unit 15c, and an external communication unit 16.

[0016] The DC / DC converter 11 is connected between the distributed power source 20 and the DC bus Bd and is a converter capable of controlling the voltage or current of the DC power supplied from the distributed power source 20. When the distributed power source 20 is a solar cell, the DC / DC converter 11 can be configured as a boost chopper. A control circuit (not shown) of the boost chopper controls the boost chopper by MPPT (Maximum Power Point Tracking) so that the output power of the solar cell is maximized.

[0017] Specifically, the control circuit measures the input voltage and input current of a boost chopper to which the power generated by the solar cell is input, and estimates the power generated by the solar cell. Based on the measured output voltage of the solar cell and the estimated power generated, the control circuit generates a voltage command value for causing the solar cell to generate power at the maximum power point (optimum operating point). For example, the control circuit searches for the maximum power point by changing the operating point voltage in predetermined step widths according to a hill-climbing method, and generates a voltage command value to maintain the maximum power point. Based on the generated voltage command value, the control circuit controls the duty ratio of the boost chopper.

[0018] If the distributed power source 20 is a storage battery, the DC / DC converter 11 is configured as a bidirectional DC / DC converter. A control circuit (not shown) of the bidirectional DC / DC converter uses the bidirectional DC / DC converter to perform charge / discharge control such as constant current (CC) discharge, constant voltage (CV) discharge, constant current charge, and constant voltage charge.

[0019] When the distributed power supply system 1 is a hybrid power generation and storage system (also called a power generation and storage linked system), a solar cell and a storage battery are used as the distributed power supply 20, a DC / DC converter 11 for the solar cell is connected between the solar cell and the DC bus Bd, and a DC / DC converter 11 for the storage battery is connected between the storage battery and the DC bus Bd. Furthermore, the power conversion device 10 may include a DC / DC converter for an on-board storage battery for controlling charging and discharging of the on-board storage battery mounted on the electric vehicle.

[0020] The inverter 12 is connected between the DC bus Bd and the distribution board 3. The inverter 12 converts DC power supplied from the DC / DC converter 11 via the DC bus Bd into AC power and outputs the converted AC power to the distribution board 3. In this case, the inverter 12 can convert the voltage or current of the AC power to be output. Note that if the distributed power source 20 is a storage battery, the inverter 12 can also convert AC power supplied from the commercial power system 2 via the distribution board 3 into DC power and output the converted DC power to the DC / DC converter 11. The distribution board 3 is connected to the commercial power system 2 and a load 4. The load 4 is a general term for loads within the home.

[0021] A control circuit (not shown) of the inverter 12 controls the output current, output voltage, or output power of the inverter 12 based on the current command value, voltage command value, or power command value supplied from the power conversion control unit 15a.

[0022] A first CT sensor 131a and a second CT sensor 131b are installed on the distribution line PL between the inverter 12 and the distribution board 3. The first CT sensor 131a and the second CT sensor 131b may have the same specifications or different specifications. When sensors with different specifications are used, the second CT sensor 131b has higher accuracy than the first CT sensor 131a. Note that the response of the second CT sensor 131b may be slower than that of the first CT sensor 131a.

[0023] The first current detection unit 13a generates a value indicating the current flowing through the power distribution line PL based on the secondary current generated by the first CT sensor 131a and outputs the value as an analog value to the power conversion control unit 15a. For example, the first current detection unit 13a includes a shunt resistor connected to a coil wound around the magnetic core of the first CT sensor 131a, and outputs the voltage across the shunt resistor to the power conversion control unit 15a as a value indicating the current flowing through the power distribution line PL. Note that a Hall element method, a Rogowski coil method, or the like may be used instead of the CT method. Alternatively, a shunt resistor may be directly connected to the power distribution line PL instead of the first CT sensor 131a, and a value indicating the current flowing through the power distribution line PL may be generated based on the voltage across the shunt resistor.

[0024] The second current detection unit 13b generates a value indicating the current flowing in the power distribution line PL based on the secondary current generated by the second CT sensor 131b, and outputs the value as an analog value to the specified meter calculation unit 15b. The first current detection unit 13a and the second current detection unit 13b may have the same specifications or different specifications. When different specifications are used, the second current detection unit 13b has higher accuracy than the first current detection unit 13a. Note that the responsiveness of the second current detection unit 13b may be slower than that of the first current detection unit 13a.

[0025] The first voltage detection unit 14a generates a value indicating the voltage of the power distribution line PL and outputs the value as an analog value to the power conversion control unit 15a. For example, the first voltage detection unit 14a includes a voltage dividing resistor and an error amplifier, and outputs a value obtained by converting the voltage of the power distribution line PL (usually about 200 V) into a smaller voltage using the voltage dividing resistor and the error amplifier to the power conversion control unit 15a.

[0026] The second voltage detection unit 14b generates a value indicating the voltage of the power distribution line PL and outputs it as an analog value to the specified meter calculation unit 15b. The first voltage detection unit 14a and the second voltage detection unit 14b may have the same specifications or different specifications. When different specifications are used, the second voltage detection unit 14b has higher accuracy than the first voltage detection unit 14a. Note that the responsiveness of the second voltage detection unit 14b may be slower than that of the first voltage detection unit 14a.

[0027] The power conversion control unit 15a generates a command value for controlling the inverter 12 based on a value indicating the current flowing in the distribution line PL (the output current of the inverter 12) input from the first current detection unit 13a and a value indicating the voltage of the distribution line PL (the output voltage of the inverter 12) input from the first voltage detection unit 14a.

[0028] The specific meter calculation unit 15b calculates the amount of electricity for the specific meter based on a value indicating the current flowing in the distribution line PL (output current of the inverter 12) input from the second current detection unit 13b and a value indicating the voltage of the distribution line PL (output voltage of the inverter 12) input from the second voltage detection unit 14b.

[0029] The system control unit 15c controls the entire system in cooperation with the power conversion control unit 15a, the specified meter calculation unit 15b, and the external communication unit 16. The power conversion control unit 15a, the specified meter calculation unit 15b, and the system control unit 15c are each configured with one microcontroller.

[0030] 2 is a diagram illustrating a first example of a power conversion control unit 15a and a specific metric calculation unit 15b according to an embodiment. In the first example, the power conversion control unit 15a includes a first AD conversion unit 151a, a first conversion unit 152a, a first power amount calculation unit 153a, and a command value generation unit 154a.

[0031] The first AD conversion unit 151a converts the value indicating the output current of the inverter 12, which is input from the first current detection unit 13a, from an analog value to a digital value and outputs the converted value to the first conversion unit 152a. The first AD conversion unit 151a converts the value indicating the output voltage of the inverter 12, which is input from the first voltage detection unit 14a, from an analog value to a digital value and outputs the converted value to the first conversion unit 152a.

[0032] The first AD conversion unit 151a may have an AD converter that converts a value indicating the output current of the inverter 12 from an analog value to a digital value, and an AD converter that converts a value indicating the output voltage of the inverter 12 from an analog value to a digital value, which are provided independently of each other, or may share a single AD converter in a time-sharing manner.

[0033] The first conversion unit 152a converts the value indicating the output current of the inverter 12, which is input from the first AD conversion unit 151a, into an output current value of the inverter 12, and outputs the converted value to the command value generation unit 154a and the first power amount calculation unit 153a. The first conversion unit 152a converts the value indicating the output voltage of the inverter 12, which is input from the first AD conversion unit 151a, into an output voltage value of the inverter 12, and outputs the converted value to the command value generation unit 154a and the first power amount calculation unit 153a.

[0034] The command value generating unit 154a generates a command value for controlling the inverter 12 based on at least one of the output current value and the output voltage value of the inverter 12. When a constant current is output from the power conversion device 10 in the grid-connected mode, the command value generating unit 154a generates a current command value for bringing the difference between the measured output current value of the inverter 12 and the target current value closer to zero.

[0035] In the grid-connected mode, when the power conversion device 10 outputs constant power, the command value generating unit 154a calculates the output power value of the inverter 12 by multiplying the output current value and output voltage value of the inverter 12. The command value generating unit 154a generates a power command value for bringing the difference between the calculated output power value of the inverter 12 and a target power value closer to zero. In the grid-connected mode, when the power conversion device 10 continues to output maximum power from the solar cell, the command value generating unit 154a generates a voltage command value for bringing the difference between the voltage value of the DC bus Bd and the target voltage value closer to zero.

[0036] In the isolated operation mode, the command value generator 154a generates a voltage command value for bringing the difference between the output voltage value of the inverter 12 and the target voltage value closer to zero. The target voltage value in the isolated operation mode is usually set to the grid voltage value.

[0037] The first power amount calculation unit 153a multiplies the output current value and output voltage value of the inverter 12 to calculate the output power of the inverter 12. The first power amount calculation unit 153a integrates the power values ​​calculated at each time to calculate the amount of power for a predetermined period. The first power amount calculation unit 153a outputs the calculated amount of power to the system control unit 15c.

[0038] The specified meter calculation unit 15b includes a second AD conversion unit 151b, a second conversion unit 152b, and a second power amount calculation unit 153b. The second AD conversion unit 151b converts a value indicating the output current of the inverter 12, which is input from the second current detection unit 13b, from an analog value to a digital value and outputs the digital value to the second conversion unit 152b. The second AD conversion unit 151b converts a value indicating the output voltage of the inverter 12, which is input from the second voltage detection unit 14b, from an analog value to a digital value and outputs the digital value to the second conversion unit 152b.

[0039] The second AD conversion unit 151b may have an AD converter that converts a value indicating the output current of the inverter 12 from an analog value to a digital value, and an AD converter that converts a value indicating the output voltage of the inverter 12 from an analog value to a digital value, which are provided independently, or may share a single AD converter in a time-sharing manner.

[0040] The second conversion unit 152b converts the value indicating the output current of the inverter 12 input from the second AD conversion unit 151b into an output current value of the inverter 12 and outputs it to the second power amount calculation unit 153b. The second conversion unit 152b converts the value indicating the output voltage of the inverter 12 input from the second AD conversion unit 151b into an output voltage value of the inverter 12 and outputs it to the second power amount calculation unit 153b.

[0041] The second power amount calculation unit 153b multiplies the output current value and output voltage value of the inverter 12 to calculate the output power value of the inverter 12. The second power amount calculation unit 153b calculates the amount of power for a predetermined period by integrating the power values ​​calculated at each time. The second power amount calculation unit 153b outputs the calculated amount of power to the system control unit 15c.

[0042] The first AD conversion unit 151a and the second AD conversion unit 151b are configured with different specifications. The second AD conversion unit 151b has higher accuracy than the first AD conversion unit 151a. The second AD conversion unit 151b has higher resolution than the first AD conversion unit 151a. For example, the first AD conversion unit 151a may have a resolution of 10 to 12 bits, and the second AD conversion unit 151b may have a resolution of 20 to 24 bits.

[0043] In addition, since the calculation of the amount of electricity for a specific meter does not require real-time performance compared to the feedback control of the inverter 12, the second AD conversion unit 151b may be slower in response than the first AD conversion unit 151a.

[0044] From the above viewpoints, in this embodiment, a successive approximation type AD converter is used in the first AD conversion unit 151a, and a ΔΣ type AD converter is used in the second AD conversion unit 151b. The ΔΣ type AD converter has higher conversion accuracy than the successive approximation type AD converter. The successive approximation type AD converter can operate at a higher speed than the ΔΣ type AD converter.

[0045] In the above description, the first CT sensor 131a, the first current detection unit 13a, the first voltage detection unit 14a, and the power conversion control unit 15a are components of the system for power conversion control. The second CT sensor 131b, the second current detection unit 13b, the second voltage detection unit 14b, and the specified meter calculation unit 15b are components of the system for specified metering. In the configuration examples shown in Figures 1 and 2, the hardware system for power conversion control and the hardware system for specified metering are all provided independently.

[0046] Returning to FIG. 1, the system control unit 15c compares the amount of power calculated by the power conversion control unit 15a with the amount of power for a specified meter calculated by the specified meter calculation unit 15b. If the difference between the two exceeds a predetermined range, the system control unit 15c determines that an abnormality has occurred. If the difference between the two is within the predetermined range, the system control unit 15c outputs the amount of power for a specified meter calculated by the specified meter calculation unit 15b to the external communication unit 16.

[0047] The external communication unit 16 transmits the amount of electricity for specific metering input from the system control unit 15c to the external connection management device 30 in a predetermined communication format.

[0048] The external connection management device 30 may be a power detection unit or a remote control setting device. The external connection management device 30 and the power conversion device 10 may be connected by wire (for example, a cable conforming to the RS-485 standard) or wirelessly (for example, Wi-Fi (registered trademark), low-power wireless). The external connection management device 30 is connected to the router device 5. The external connection management device 30 and the router device 5 are connected by wire (for example, a LAN cable) or wirelessly (for example, Wi-Fi).

[0049] A monitor (not shown) can be connected to the external connection management device 30. The external connection management device 30 and the monitor may be connected directly or via the router device 5. The monitor can display the amount of power generated by the solar power generation system, the amount of power purchased, the amount of power sold, the amount of power used, and the electricity rates by time period. This information can also be displayed on the screen of an information terminal (for example, a smartphone or PC) owned by the user that is connected to the router device 5 wirelessly or via a wired connection.

[0050] The external connection management device 30 or the monitor includes a recording medium, and the measurement data of the amount of power can be stored on the recording medium as log data. The recording medium may be a built-in type or a removable recording medium.

[0051] The external connection management device 30 functions as a gateway for connecting to an external network 6. The network 6 is a general term for communication paths such as the Internet, dedicated lines, and VPNs (Virtual Private Networks), and the communication media and protocols involved are not important. For example, an optical fiber network, an ADSL network, a CATV network, a mobile communication network, a wireless LAN, or a wired LAN can be used as a communication medium. For example, TCP (Transmission Control Protocol) / IP (Internet Protocol), UDP (User Datagram Protocol) / IP, or Ethernet (registered trademark) can be used as a communication protocol.

[0052] The external connection management device 30 transmits the amount of power to be measured received from the external communication unit 16 of the power conversion device 10 to an external server 7 via the network 6. The external server 7 is a server managed and operated by an electricity retailer, an aggregator, an electricity transmission and distribution company, etc. These companies can calculate electricity charges based on the amount of power measured by the power conversion device 10.

[0053] When the external connection management device 30 is a remote control setting device, the external connection management device 30 also functions as an operation terminal for operating the power conversion device 10. An operation unit may be provided on the main body of the power conversion device 10.

[0054] 3 is a flowchart showing the flow of a process for determining the metering accuracy of the amount of electric power for a specified meter performed by the power conversion device 10 according to the first embodiment. While the power conversion device 10 is operating (Y in S10), the power conversion control unit 15a calculates the amount of electric power P1 to be output by the inverter 12 (S11), and the specified meter calculation unit 15b calculates the amount of electric power P2 to be output by the inverter 12 (S12). The system control unit 15c calculates the error between the amount of electric power P1 calculated by the power conversion control unit 15a and the amount of electric power P2 calculated by the specified meter calculation unit 15b (S13).

[0055] The system control unit 15c determines whether the error is within the allowable range (S14). In Japan, the Agency for Natural Resources and Energy's Expert Committee on Metrology has stipulated that a notifier intending to conduct a new electricity trade can flexibly select the tolerance for the measuring instrument used for specified metering from seven levels ranging from 0.9% to 10% in use, taking into account the needs of the trading parties, the size of the trade, and the intended use. The tolerance is 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 specified as 2.0% and the tolerance during use is specified as 3.0%. The n3 class is a class that allows transactions via the power transmission network of a general electricity transmission and distribution utility without accountability to the trading counterparty, regardless of the size of the transaction.

[0056] For example, if the maximum tolerance of the power amount P1 calculated by the power conversion control unit 15a is 8% and the tolerance of the power amount P2 calculated by the specified meter calculation unit 15b is within 3%, the ratio of the power amounts P1 and P2 will be within the range of approximately 0.893 to approximately 1.119. In this example, if there is a discrepancy of approximately 12% or more between the power amounts P1 and P2, it can be assumed that an abnormality has occurred in at least one of the power conversion control system and the specified meter system. The designer can set the allowable error range between the power amounts P1 and P2 based on the maximum tolerance of the power amount P1 calculated by the power conversion control unit 15a and the target tolerance of the power amount P2 calculated by the specified meter calculation unit 15b.

[0057] In step S14, if the difference between the amount of electric power P1 and the amount of electric power P2 is within the allowable range (Y in S14), the system control unit 15c notifies the external communication unit 16 of the amount of electric power P2 calculated by the specified meter calculation unit 15b (S15). If the difference between the amount of electric power P1 and the amount of electric power P2 is outside the allowable range (N in S14), the system control unit 15c executes error processing (S16).

[0058] For example, the system control unit 15c automatically restarts the power conversion device 10 and checks whether the difference between the power amounts P1 and P2 falls within the allowable range. If the difference between the power amounts P1 and P2 does not fall within the allowable range even after restarting the device a predetermined number of times, the system control unit 15c displays a metering function error on a monitor or an information terminal carried by the user. The user, seeing the message on the monitor or information terminal, contacts a maintenance technician and requests repairs. The system control unit 15c may also send a repair request directly to a terminal device installed at a service center of the manufacturer of the power conversion device 10 via the network 6.

[0059] The above-described processing of steps S11 to S16 is constantly executed until the power conversion device 10 is stopped (N in S10). Note that the process of comparing and determining the amount of power P1 and the amount of power P2 may be executed periodically, rather than constantly.

[0060] 4 is a diagram illustrating a second example of the power conversion control unit 15a and the specified metric calculation unit 15b according to the embodiment. In the second example, the power conversion control unit 15a further includes a first adjustment value holding unit 155a and a first error adjustment unit 156a in addition to the first AD conversion unit 151a, the first power amount calculation unit 153a, and the command value generation unit 154a. The specified metric calculation unit 15b further includes a second adjustment value holding unit 155b and a second error adjustment unit 156b in addition to the second AD conversion unit 151b and the second power amount calculation unit 153b.

[0061] The first adjustment value holding unit 155a and the second adjustment value holding unit 155b are each constructed in a non-volatile memory (for example, an Electrically Erasable Programmable Read-Only Memory (EEPROM)) of the microcontroller.

[0062] During the manufacture of the power conversion device 10, the hardware system for power conversion control and the hardware system for specified measurement are calibrated. The CT sensor 131, current detection unit 13, voltage detection unit 14, and microcontroller that make up each of the hardware systems use various active elements (e.g., operational amplifiers, transistors, diodes) and passive elements (e.g., resistors, coils, capacitors). These elements have individual differences due to process variations and the like, and contain offset errors and gain errors.

[0063] In the calibration process during manufacturing, errors in the hardware system for power conversion control are measured, and adjustment values ​​(also called correction values) to compensate for the errors are set and registered in the non-volatile memory of the microcontroller. Similarly, errors in the hardware system for specified measurements are measured, and adjustment values ​​to compensate for the errors are set and registered in the non-volatile memory of the microcontroller.

[0064] 5 is a flowchart showing the flow of the calibration process for the hardware system for power conversion control. A calibration device (not shown) applies a calibration AC voltage to the first voltage detection unit 14a (S20). With the calibration AC voltage applied, the calibration device acquires a voltage value output from the first conversion unit 152a (S21). The calibration device calculates an adjustment value for the voltage value of the hardware system for power conversion control based on the applied voltage value and the acquired voltage value (S22). Specifically, the calibration device calculates an adjustment value for compensating for a gain error between the applied voltage value and the acquired voltage value. The calculated adjustment value for the voltage value is set in the first adjustment value holding unit 155a before shipping the power conversion device 10 (S23).

[0065] The calibration device applies a DC current for calibration to the first CT sensor 131a (S24). With the DC current for calibration applied, the calibration device acquires a current value output from the first conversion unit 152a (S25). The calibration device calculates an adjustment value for the current value of the hardware system for power conversion control based on the applied current value and the acquired current value (S26). Specifically, the calibration device calculates an adjustment value for compensating for offset errors and gain errors between the applied current value and the acquired current value. The calculated adjustment value for the current value is set in the first adjustment value holding unit 155a before shipping the power conversion device 10 (S27).

[0066] FIG. 6 is a flowchart showing the flow of the calibration process for the hardware system for specified measurement. The calibration device applies a calibration AC voltage to the second voltage detection unit 14b (S30). With the calibration AC voltage applied, the calibration device acquires the voltage value output from the second conversion unit 152b (S31). The calibration device calculates an adjustment value for the voltage value of the hardware system for specified measurement based on the applied voltage value and the acquired voltage value (S32). Specifically, the calibration device calculates an adjustment value for compensating for a gain error between the applied voltage value and the acquired voltage value. The calculated adjustment value for the voltage value is set in the second adjustment value storage unit 155b before shipping the power conversion device 10 (S33).

[0067] The calibration device applies a calibration AC current to the second CT sensor 131b (S34). With the calibration AC current applied, the calibration device acquires the current value output from the second conversion unit 152b (S35). The calibration device applies a high-pass filter to the acquired current value (S36). Specifically, the acquired current value is differentiated. This cuts out the DC component from the acquired current value, eliminating the offset error.

[0068] The calibration device calculates an adjustment value for the current value of the specific measurement hardware system based on the applied current value and the current value after application of the high-pass filter (S37). Specifically, it calculates an adjustment value to compensate for a gain error between the applied current value and the current value after application of the high-pass filter. The calculated adjustment value for the current value is set in the second adjustment value holding unit 155b before shipping of the power conversion device 10 (S38).

[0069] Returning to Fig. 4, the first error adjustment unit 156a of the power conversion control unit 15a adjusts the voltage value output from the first conversion unit 152a using the adjustment value of the voltage value set in the first adjustment value holding unit 155a. Similarly, the first error adjustment unit 156a adjusts the current value output from the first conversion unit 152a using the adjustment value of the current value set in the first adjustment value holding unit 155a.

[0070] The second error adjustment unit 156b of the specified metric calculation unit 15b adjusts the voltage value output from the second conversion unit 152b using the adjustment value of the voltage value set in the second adjustment value holding unit 155b. Similarly, the second error adjustment unit 156b adjusts the current value output from the second conversion unit 152b using the adjustment value of the current value set in the second adjustment value holding unit 155b.

[0071] Fig. 7 is a diagram for explaining the configuration of a power conversion device 10 according to Modification 1. In the power conversion device 10 shown in Modification 1, the first CT sensor 131a and the second CT sensor 131b shown in Fig. 1 are shared, and one CT sensor 131 is installed. In this case, the redundancy of the CT sensor 131 is reduced, but costs can be reduced.

[0072] FIG. 8 is a diagram illustrating the configuration of a power conversion device 10 according to Modification 2. In the power conversion device 10 shown in Modification 2, the first CT sensor 131a and the second CT sensor 131b shown in FIG. 1 are shared, and one CT sensor 131 is installed; the first current detection unit 13a and the second current detection unit 13b are shared, and one current detection unit 13 is installed; and the first voltage detection unit 14a and the second voltage detection unit 14b are shared, and one voltage detection unit 14 is installed. In this case, the redundancy of the CT sensor 131, the current detection unit 13, and the voltage detection unit 14 is reduced, but costs can be reduced. Note that one of the current detection unit 13 and the voltage detection unit 14 may be made redundant, and the other may be shared.

[0073] In the above description, the power conversion control unit 15a, the specified meter calculation unit 15b, and the system control unit 15c are each configured with one microcontroller, but the power conversion control unit 15a and the specified meter calculation unit 15b may be integrated into one microcontroller. Also, the specified meter calculation unit 15b and the system control unit 15c may be integrated into one microcontroller, or the power conversion control unit 15a and the system control unit 15c may be integrated into one microcontroller. Also, the power conversion control unit 15a, the specified meter calculation unit 15b, and the system control unit 15c may be integrated into one microcontroller.

[0074] In this way, a part of the hardware system for power conversion control and a part of the hardware system for specific metering may be shared, and the rest may be provided independently.

[0075] As described above, according to this embodiment, by providing a hardware system for power conversion control and part or all of a hardware system for specific metering independently, it is possible to measure the amount of electricity with high precision and robustness.

[0076] 9(a)-(b) are diagrams comparing the system configuration of a distributed power system 1 according to the embodiment with the system configuration of a conventional distributed power system 1. In the conventional distributed power system 1 shown in FIG. 9(b), a watt-hour meter 8 (e.g., a smart meter) is installed between the power conversion device 10 and the distribution board 3. In the distributed power system 1 according to the embodiment shown in FIG. 9(a), the watt-hour meter 8 can be omitted by measuring the amount of power in the power conversion device 10.

[0077] If the current detection unit, voltage detection unit, and microcontroller already installed in the power conversion device 10 are also used for calculating the amount of power, it is difficult to recognize any discrepancies between the detected voltage and current values ​​and their true values. In contrast, in this embodiment, the hardware system for power conversion control and the hardware system for specific metering are separated, making it possible to compare the amounts of power calculated by each system. This enables robust and reliable power metering.

[0078] In order to avoid the risk of DC leakage during calibration during manufacturing of the power conversion device 10, it is common to apply DC current instead of AC current to detect offset and gain errors in the current detection unit and calculate adjustment values ​​to compensate for these errors. However, adjustment values ​​calculated using a DC bias cannot completely compensate for offset and gain errors, and errors remain. They also cannot compensate for nonlinearity errors. In contrast, with an AC bias, nonlinearity errors are rounded off during gain adjustment. Therefore, adjustment values ​​calculated using an AC bias provide higher accuracy in compensating for nonlinearity errors than adjustment values ​​calculated using a DC bias.

[0079] In this embodiment, the adjustment value is calculated using a DC bias when calibrating the hardware system for power conversion control, and the adjustment value is calculated using an AC bias when calibrating the hardware system for specific measurement. The hardware system for power conversion control needs a function to detect DC leakage, so the adjustment value needs to be calculated using a DC bias. This allows the power conversion control unit 15a to stop the inverter 12 if a DC component leaks from the inverter 12 due to a malfunction of the inverter 12, thereby reducing the risk of electric shock and the risk of failure of the output destination device.

[0080] The function to detect DC outflow is implemented in the power conversion control unit 15a, so it does not need to be implemented in the specified meter calculation unit 15b. Furthermore, DC values ​​are not required for calculating the amount of power. Therefore, when calibrating the specified meter hardware system, an adjustment value is calculated using an AC bias. At this time, a high-pass filter is used to cut the DC component.

[0081] By placing the high-pass filter after the second AD conversion unit 151b, it is possible to calculate an adjustment value that compensates for errors caused by elements such as the operational amplifier included in the second AD conversion unit 151b. In this regard, if the high-pass filter is placed before the second AD conversion unit 151b, an adjustment value that cannot compensate for errors generated in the second AD conversion unit 151b will be calculated.

[0082] In this way, by adjusting the hardware system for power conversion control with a DC bias and the hardware system for specific metering with an AC bias, it is possible to improve the accuracy of measuring the amount of electricity while ensuring safety.

[0083] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be readily understood by those skilled in the art that various modifications are possible in the combination of the respective components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0084] In the above embodiment, the system control unit 15c compares the amount of power calculated by the power conversion control unit 15a with the amount of power for the specified meter calculated by the specified meter calculation unit 15b, and determines whether the difference is within a predetermined range. In this regard, in the second embodiment, this power amount comparison and determination process is not essential. That is, the system control unit 15c may output the amount of power for the specified meter calculated by the specified meter calculation unit 15b directly to the external communication unit 16. In this case, although it is not possible to detect the discrepancy in the amount of power for the specified meter in real time, the advantages of adjusting the hardware system for power conversion control with a DC bias and adjusting the hardware system for the specified meter with an AC bias are still obtained.

[0085] The embodiment may be specified by the following items.

[0086] [Item 1] a power conversion unit (12) that converts the voltage or current of power supplied from the distributed power source (20) and outputs the converted voltage or current to the power system (2); a power conversion control unit (15a) that generates a command value for controlling the power conversion unit (12) based on a voltage and a current output from the power conversion unit (12); and a specific meter calculation unit (15b) that calculates the amount of power for a specific meter based on the voltage and current output from the power conversion unit (12), A power conversion device (10) in which a hardware system for detecting the voltage and current output from the power conversion unit (12) and calculating the command value, and a part or all of a hardware system for detecting the voltage and current output from the power conversion unit (12) and calculating the amount of electric power for specific measurement are provided independently. This makes it possible to achieve highly accurate and robust measurement of the amount of electric power. [Item 2] a first voltage detection unit (14a) that detects a voltage output from the power conversion unit (12) and outputs the voltage to the power conversion control unit (15a); a first current detection unit (13a) that detects a current output from the power conversion unit (12) and outputs the detected current to the power conversion control unit (15a); a second voltage detection unit (14b) that detects a voltage output from the power conversion unit (12) and outputs the voltage to the specified measurement calculation unit (15b); a second current detection unit (13b) that detects a current output from the power conversion unit (12) and outputs the detected current to the specified measurement calculation unit (15b); Item 1. The power conversion device (10) according to item 1, further comprising: This allows the voltage detection section and the current detection section to be made redundant, thereby making it possible to build a robust system. [Item 3] the power conversion control unit (15a) calculates an amount of power based on the voltage and current output from the power conversion unit (12); The power conversion device (10) The power conversion device (10) according to item 1 or 2 further comprises a system control unit (15c) that compares the amount of power calculated by the power conversion control unit (15a) with the amount of power for the specific meter calculated by the specific meter calculation unit (15b), and determines that an abnormality has occurred if the difference between the two exceeds a predetermined range. This makes it possible to recognize whether or not there is a discrepancy between the actual value of the specific metering amount of electricity. [Item 4] the power conversion control unit (15a) includes a first AD conversion unit (151a), The specific metric calculation unit (15b) includes a second AD conversion unit (151b), The second AD conversion unit (151b) has a higher resolution than the first AD conversion unit (151a). 4. The power conversion device (10) according to any one of items 1 to 3. This makes it possible to reduce costs while improving the measurement accuracy of the amount of electricity used for specific measurements. [Item 5] The power conversion control unit (15a) a first AD conversion unit (151a) that converts the voltage and current output from the power conversion unit (12) from analog values ​​to digital values, respectively; a first adjustment value holding unit (155a) that holds an adjustment value of the voltage value and an adjustment value of the current value; a first error adjustment unit that adjusts the voltage value converted into a digital value by the first AD conversion unit (151a) using an adjustment value of the voltage value held in the first adjustment value holding unit (155a), and adjusts the current value converted into a digital value by the first AD conversion unit (151a) using an adjustment value of the current value held in the first adjustment value holding unit (155a), The specific measurement calculation unit (15b) a second AD conversion unit (151b) that converts the detected voltage and current output from the power conversion unit (12) from analog values ​​to digital values, respectively; a second adjustment value holding unit (155b) that holds an adjustment value of the voltage value and an adjustment value of the current value; a second error adjustment unit that adjusts the voltage value converted into the digital value by the second AD conversion unit (151b) using the adjustment value of the voltage value held in the second adjustment value holding unit (155b), and adjusts the current value converted into the digital value by the second AD conversion unit (151b) using the adjustment value of the current value held in the second adjustment value holding unit (155b), the adjustment value of the current value held in the first adjustment value holding unit (155a) is a value set based on the current value converted into a digital value by the first AD conversion unit (151a) in a state where a direct current is applied in a calibration before shipping, 3. The power conversion device according to claim 1, wherein the adjustment value of the current value held in the second adjustment value holding unit is a value set based on a current value converted into a digital value by the second AD conversion unit when an AC current is applied, during calibration before shipping. This makes it possible to improve the measurement accuracy of the amount of electricity used for specific measurements while ensuring safety. [Item 6] Item 6. The power conversion device (10) according to item 5, wherein the adjustment value of the current value held in the second adjustment value holding unit (155b) is a value set based on a value obtained by applying a high-pass filter to the current value after it has been converted into a digital value by the second AD conversion unit (151b). This allows for improved accuracy of the adjustment value for the specific measurement. [Item 7] The second AD conversion unit (151b) has a higher resolution than the first AD conversion unit (151a). Item 7. The power conversion device (10) according to item 5 or 6. This makes it possible to reduce costs while improving the measurement accuracy of the amount of electricity used for specific measurements. [Item 8] one or more distributed generation sources (20); A power conversion device (10) according to any one of items 1 to 7; A distributed power system (1) comprising: This makes it possible to achieve highly accurate and robust measurement of the amount of electric power. [Explanation of symbols]

[0087] REFERENCE SIGNS LIST 1 Distributed power system, 2 Commercial power system, 3 Distribution board, 4 Load, 5 Router device, 6 Network, 7 Server, 8 Watt-hour meter, 10 Power conversion device, Bd DC bus, PL Distribution line, 11 DC / DC converter, 12 Inverter, 13a First current detection unit, 13b Second current detection unit, 131a First CT sensor, 131b Second CT sensor, 14a First voltage detection unit, 14b Second voltage detection unit, 15a Power conversion control unit, 15b Specified metering calculation unit, 15c System control unit, 151a First AD conversion unit, 151b Second AD conversion unit, 152a First conversion unit, 152b Second conversion unit, 153a First power amount calculation unit, 153b Second power amount calculation unit, 154a Command value generation unit, 155a first adjustment value holding unit, 155b second adjustment value holding unit, 156a first error adjustment unit, 156b second error adjustment unit, 16 external communication unit, 20 distributed power source, 30 external connection management device.

Claims

1. a power conversion unit that converts the voltage or current of the power supplied from the distributed power source and outputs the converted voltage or current to the power grid; a power conversion control unit that generates a command value for controlling the power conversion unit based on the voltage and current output from the power conversion unit; a specific meter calculation unit that calculates an amount of power for a specific meter based on the voltage and current output from the power conversion unit, a hardware system for detecting the voltage and current output from the power conversion unit and calculating the command value, and a part or all of a hardware system for detecting the voltage and current output from the power conversion unit and calculating the amount of power for the specified meter are provided independently; The specified metering calculation unit includes an AD conversion unit for metering that converts the detected voltage and current output from the power conversion unit from analog values ​​to digital values, respectively; The current value converted into the digital value by the measurement AD conversion unit is adjusted based on the current value converted into the digital value by the measurement AD conversion unit in a state where an AC current is applied, in calibration before shipping. Power conversion device.

2. a first voltage detection unit that detects a voltage output from the power conversion unit and outputs the voltage to the power conversion control unit; a first current detection unit that detects a current output from the power conversion unit and outputs the current to the power conversion control unit; a second voltage detection unit that detects a voltage output from the power conversion unit and outputs the voltage to the specified metric calculation unit; a second current detection unit that detects a current output from the power conversion unit and outputs the detected current to the specified metric calculation unit; The power converter of claim 1 further comprising:

3. A power conversion device, a power conversion unit that converts the voltage or current of the power supplied from the distributed power source and outputs the converted voltage or current to the power grid; a power conversion control unit that generates a command value for controlling the power conversion unit based on the voltage and current output from the power conversion unit; a specific meter calculation unit that calculates an amount of power for a specific meter based on the voltage and current output from the power conversion unit, a hardware system for detecting the voltage and current output from the power conversion unit and calculating the command value, and a part or all of a hardware system for detecting the voltage and current output from the power conversion unit and calculating the amount of power for the specified meter are provided independently; the power conversion control unit calculates an amount of power based on the voltage and current output from the power conversion unit, The power conversion device is The power conversion device further includes a system control unit that compares the amount of power calculated by the power conversion control unit with the amount of power for the specific meter calculated by the specific meter calculation unit, and determines that an abnormality has occurred if the error between the two exceeds a predetermined range.

4. the power conversion control unit includes an AD conversion unit for control, the AD conversion unit for measurement has a higher resolution than the AD conversion unit for control; The power conversion device according to claim 1 or 2.

5. The power conversion control unit an AD conversion unit for control that converts the voltage and current output from the power conversion unit from analog values ​​to digital values; a first adjustment value holding unit that holds an adjustment value of the voltage value and an adjustment value of the current value; a first error adjustment unit that adjusts the voltage value converted into a digital value by the control AD ​​conversion unit using the adjustment value of the voltage value held in the first adjustment value holding unit, and adjusts the current value converted into a digital value by the control AD ​​conversion unit using the adjustment value of the current value held in the first adjustment value holding unit, The specific metric calculation unit is a second adjustment value holding unit that holds an adjustment value of the voltage value and an adjustment value of the current value; a second error adjustment unit that adjusts the voltage value converted into a digital value by the metering AD conversion unit using the adjustment value of the voltage value held in the second adjustment value holding unit, and adjusts the current value converted into a digital value by the metering AD conversion unit using the adjustment value of the current value held in the second adjustment value holding unit, the adjustment value of the current value held in the first adjustment value holding unit is a value set based on a current value converted into a digital value by the control AD ​​conversion unit in a state where a direct current is applied during calibration before shipping, 3. The power conversion device according to claim 1, wherein the adjustment value of the current value stored in the second adjustment value storage unit is a value set based on the current value converted into a digital value by the metering AD conversion unit when an AC current is applied during calibration before shipping.

6. 6. The power conversion device according to claim 5, wherein the adjustment value of the current value held in the second adjustment value holding unit is a value set based on a value obtained by applying a high-pass filter to the current value after it has been converted into a digital value by the metering AD conversion unit.

7. the AD conversion unit for measurement has a higher resolution than the AD conversion unit for control; The power conversion device according to claim 5 or 6.

8. one or more distributed generation sources; The power conversion device according to any one of claims 1 to 7; A distributed power system comprising:

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