Power conversion equipment, distributed power systems

Abstract

To perform highly accurate measurement of power at low cost with a power conversion device.SOLUTION: A control unit 15 calculates an amount of power to be outputted from a power conversion device 10 or an amount of power to be inputted from a system 2 to the power conversion device 10, on the basis of a voltage value detected by a voltage detection unit 14 and a current value detected by a current detection unit 13. A power source circuit 16 generates a power source voltage of the control unit 15. A reference voltage generating circuit 17 generates a reference voltage on the basis of the power source voltage generated by the power source circuit 16. The control unit 15 calculates a power amount in which an error caused by a fluctuation of the power source voltage has been corrected on the basis of the relationship between a preset reference voltage detection value and a reference voltage detection value that is based on the reference voltage supplied from the reference voltage generating circuit 17.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 is gaining 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 Act includes a specified measurement system to improve the environment for promoting the use of distributed resources.

[0003] The specified metrology system is a system that allows the use of measuring instruments that are not inspected under the Measurement Act as an exception under certain conditions. Businesses (aggregators, etc.) that have submitted a notification in advance can be subject to the specified metrology system, and the business operators are obligated to provide explanations to consumers (households, etc.) and to carry out appropriate measurements using measuring instruments with appropriate accuracy.

[0004] Fig. 1 of Patent Document 1 discloses a configuration in which a power selling wattmeter and a power purchasing wattmeter are installed between a power generation system and a commercial grid. Businesses subject to the specified metering system can omit the installation of these wattmeters and use a power conditioner as a special metering instrument. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-192485 A Summary of the Invention [Problem to be solved by the invention]

[0006] Smart meters, which are commonly used as measuring instruments, have a small self-temperature rise, and the impact of temperature on the power measurement value is small. In contrast, power conditioners have a large self-temperature rise, and the impact of temperature on the power measurement value is large. AD converters in particular are greatly affected by fluctuations in power supply voltage due to temperature drift. Deviations in the power supply voltage cause bit errors.

[0007] One solution to this problem would be to use a power supply circuit with excellent temperature characteristics that results in little temperature drift, but this would increase costs and reduce current supply capacity.Another solution would be to install a large-scale cooling system within the power conditioner, but this would increase costs and lead to a larger system.

[0008] The present disclosure has been made in consideration of these circumstances, and has an object to provide a power conversion device and a distributed power system that realizes high-precision power measurement at low cost. [Means for solving the problem]

[0009] In order to solve the above problems, a power conversion device according to an embodiment of the present disclosure includes a DC / DC converter that controls the voltage of DC power supplied from a DC power source, an inverter that converts the DC power supplied from the DC / DC converter into AC power, a voltage detection unit that detects the voltage of a distribution line between the inverter and a distribution board connected to a power system, a current detection unit that detects a current flowing through the distribution line, a control unit that calculates an amount of power output from the power conversion device or an amount of power input from the power system to the power conversion device based on a voltage value detected by the voltage detection unit and a current value detected by the current detection unit, a power supply circuit that generates a power supply voltage for the control unit, and a reference voltage generation circuit that generates a reference voltage based on the power supply voltage generated by the power supply circuit. The control unit calculates the amount of power with an error caused by fluctuations in the power supply voltage corrected based on a relationship between a preset reference voltage detection value and a reference voltage detection value based on a reference voltage supplied from the reference voltage generation circuit. Effect of the Invention

[0010] According to the present disclosure, it is possible to realize low-cost, highly accurate power measurement using a power conversion device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram for explaining a distributed power supply system according to a first embodiment. [Diagram 2] 4 is a waveform chart showing a specific example of a temperature drift correction process performed by the power conversion device according to the first embodiment. [Diagram 3] 4 is a flowchart showing a flow of a temperature drift correction process performed by the power conversion device according to the first embodiment. [Figure 4] FIG. 11 is a diagram for explaining a distributed power supply system according to a second embodiment. [Diagram 5] FIG. 11 is a diagram for explaining a distributed power supply system according to a third embodiment. [Figure 6] 6(a) and 6(b) are diagrams comparing the system configuration of the distributed power supply system according to the first embodiment with the system configuration of a conventional distributed power supply system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1 is a diagram for explaining a distributed power system 1 according to embodiment 1. The distributed power system 1 shown in FIG.

[0013] The power conversion device 10 includes a DC / DC converter 11, an inverter 12, a CT sensor 13a, a current detection unit 13, a voltage detection unit 14, a control unit 15, a power supply circuit 16, and a reference voltage generation circuit 17.

[0014] The solar cell C1 can convert light energy directly into DC power by utilizing the photovoltaic effect. pond,Polycrystalline silicon solar cells, single crystal silicon solar cells, thin film silicon solar cells, compound solar cells, etc. can be used.

[0015] The solar cell 20a is connected to the DC / DC converter 11 of the power conversion device 10 and outputs the generated power to the power conversion device 10. The DC / DC converter 11 is connected between the solar cell 20a and a DC bus and is a converter capable of controlling the voltage of the DC power supplied from the solar cell 20a. The DC / DC converter 11 can be configured, for example, by a boost chopper.

[0016] The converter control circuit (not shown) controls the DC / DC converter 11 by MPPT (Maximum Power Point Tracking) so that the output power of the solar cell 20a is maximized. Specifically, the converter control circuit measures the input voltage and input current of the DC / DC converter 11, which are the output voltage and output current of the solar cell 20a, to estimate the power generated by the solar cell 20a. The converter control circuit generates a voltage command value for making the power generated by the solar cell 20a a maximum power point (optimum operating point) based on the measured output voltage of the solar cell 20a and the estimated power generation. For example, the converter control circuit changes the operating point voltage by a predetermined step width according to a hill-climbing method to search for the maximum power point, and generates a voltage command value to maintain the maximum power point. The DC / DC converter 11 performs switching operation in response to a drive signal based on the generated voltage command value.

[0017] The inverter 12 is connected between the DC bus and the distribution board 3. The inverter 12 converts DC power supplied from the DC / DC converter 11 via the DC bus into AC power, and outputs the converted AC power to the distribution board 3. A commercial power system (hereinafter simply referred to as system 2) is connected to the distribution board 3. A load 4 is further connected to the distribution board 3. The load 4 is a general term for loads within the home.

[0018] An inverter control circuit (not shown) controls the inverter 12 so that the voltage of the DC bus is maintained at a target value. Specifically, the inverter control circuit detects the voltage of the DC bus and generates a current command value for matching the detected bus voltage with the target value. The inverter control circuit generates a current command value for increasing the output power of the inverter 12 when the voltage of the DC bus is higher than the target value, and generates a current command value for decreasing the output power of the inverter 12 when the voltage of the DC bus is lower than the target value. The inverter 12 performs a switching operation in response to a drive signal based on the generated current command value.

[0019] A CT sensor 13a is installed on the distribution line between the inverter 12 and the distribution board 3. The current detection unit 13 outputs a current detection value Io (analog value) obtained by extracting a current flowing through a coil wound around a magnetic core of the CT sensor 13a as a voltage value using a shunt resistor to the control unit 15. Note that instead of the CT method, the current flowing through the distribution line may be measured using a Hall element method, a Rogowski coil method, or the like.

[0020] 1, the voltage detection unit 14 detects the voltage of the distribution line between the inverter 12 and the distribution board 3. In the example shown in Fig. 1, the voltage detection unit 14 detects the voltage between the U phase and the W phase. The voltage detection unit 14 includes a voltage dividing resistor and an error amplifier, and converts the voltage of the distribution line (usually about 200 V) into a smaller voltage using the voltage dividing resistor and the error amplifier. The voltage detection unit 14 outputs the obtained voltage detection value Vo (analog value) to the control unit 15.

[0021] The power supply circuit 16 generates a power supply voltage VDD for the control unit 15. In the example shown in Fig. 1, the power supply circuit 16 steps down the output voltage (e.g., about 250V) of the solar cell 20a to generate the power supply voltage VDD (e.g., about 3.3 to 5V). The power supply circuit 16 can be configured with a power supply IC, and is configured with, for example, a step-down switching regulator. The power supply circuit 16 may be configured in two stages, in which case the first stage steps down the output voltage of the solar cell 20a to 24V or 12V, and the second stage steps down the voltage of 24V or 12V to the power supply voltage VDD.

[0022] Although not shown in FIG. 1, the power supply circuit 16 also supplies the power supply voltage VDD to components other than the control unit 15. Specifically, the power supply voltage VDD is also supplied to some of the amplifiers used in the current detection unit 13 and the voltage detection unit 14. Therefore, a certain level of current supply capability is required. From the viewpoint of reducing power consumption, it is desirable to use a power supply circuit 16 with high conversion efficiency. Therefore, a switching regulator is basically used for the power supply circuit 16, rather than a linear regulator. Note that a switching regulator and a linear regulator (for example, an LDO (Low Dropout Regulator)) may be used in combination.

[0023] The power supply circuit 16 may generate the power supply voltage VDD from the voltage of the distribution line between the inverter 12 and the distribution board 3, instead of from the output voltage of the solar cell 20a. In this case, the power supply circuit 16 needs to include an AC / DC converter in front of the DC / DC converter (e.g., a step-down switching regulator). The power supply circuit 16 may be configured to selectively obtain a voltage from the output voltage of the solar cell 20a or the voltage of the distribution line.

[0024] The reference voltage generating circuit 17 generates a reference voltage Vref based on the power supply voltage VDD generated by the power supply circuit 16. In the example shown in Fig. 1, the reference voltage generating circuit 17 generates the reference voltage Vref by stepping down the power supply voltage VDD. The reference voltage generating circuit 17 can be configured with a power supply IC, for example, a shunt regulator.

[0025] A shunt regulator is a power supply IC that can keep the output voltage constant despite fluctuations in the power supply voltage VDD and temperature fluctuations. Compared to a switching regulator, a shunt regulator has a low current supply capacity and low conversion efficiency. However, the reference voltage generating circuit 17 does not need a high current supply capacity because it basically needs only a current supply capacity to supply the reference voltage Vref to the AD converter 151 of the control unit 15. Generally, there is a trade-off between current supply capacity and temperature characteristics in a power supply IC, and a shunt regulator is a power supply IC that has a low current supply capacity but excellent temperature characteristics.

[0026] Although the temperature characteristic is lower than that of a shunt regulator, a Zener diode may be used as the reference voltage generating circuit 17.

[0027] The control unit 15 is composed of a microcontroller. The microcontroller operates by receiving the supply of the power supply voltage VDD generated by the power supply circuit 16. The control unit 15 calculates the amount of power output from the power conversion device 10 based on the voltage detection value Vo detected by the voltage detection unit 14 and the current detection value Io detected by the current detection unit 13. At that time, the control unit 15 calculates the amount of power in which an error due to fluctuations in the power supply voltage VDD has been corrected based on the relationship between a preset reference voltage measurement value Dref and a reference voltage detection value Dref based on the reference voltage Vref supplied from the reference voltage generation circuit 17. A specific description will be given below.

[0028] The control unit 15 includes an AD converter 151 , a correction coefficient calculation unit 152 , a storage unit 153 , a power amount calculation unit 154 , and an output unit 155 .

[0029] The AD converter 151 converts the voltage detection value Vo (analog value) detected by the voltage detection unit 14, the current detection value Io (analog value) detected by the current detection unit 13, and the reference voltage Vref generated by the reference voltage generation circuit 17 into a voltage detection value Dvo (digital value), a current detection value Dio (digital value), and a reference voltage value Dref (digital value), respectively. For example, a successive approximation type AD converter can be used as the AD converter 151.

[0030] The value after conversion by AD converter 151 ranges from 0 to 1023 when the resolution is 10 bits, and ranges from 0 to 4095 when the resolution is 12 bits. When a voltage with the power supply voltage VDD as the upper limit is input to AD converter 151, the value after conversion is defined as shown in the following (Equation 1). Converted value = converted value × resolution ÷ power supply voltage VDD (Formula 1)

[0031] For example, when the power supply voltage VDD is 5 V and the AD converter 151 has a resolution of 12 bits, the converted value is defined as shown in the following (Equation 2). Converted value = converted value × 4096 ÷ 5 (Formula 2)

[0032] When the temperature inside the power conversion device 10 changes, the power supply voltage VDD generated by the power supply circuit 16 changes. Each detection value converted by the AD converter 151 contains an error component that is inversely proportional to the change in the power supply voltage VDD.

[0033] Therefore, in this embodiment, a mechanism for correcting the temperature drift of the power supply voltage VDD is introduced. Before shipping, the manufacturer of the power conversion device 10 obtains a reference voltage detection value Dref (digital value) obtained by converting a reference voltage value Vref (analog value) supplied from the reference voltage generating circuit 17 at room temperature by an AD converter 151, and registers the reference voltage detection value Dref (digital value) in the storage unit 153 as a factory shipping value.

[0034] The factory-shipped value of the reference voltage detection value Dref may be stored in a non-volatile memory (for example, an EEPROM or a flash memory) outside the control unit 15, rather than in the storage unit 153 (i.e., a ROM built into a microcontroller) in the control unit 15. In this case, the factory-shipped value of the reference voltage detection value Dref is loaded into the RAM in the control unit 15 and used when used.

[0035] The correction coefficient calculation unit 152 compares the factory-shipped value of the reference voltage detection value Dref registered in the storage unit 153 with the reference voltage detection value Dref (digital value) obtained by converting the reference voltage Vref supplied from the reference voltage generation circuit 17 by the AD converter 151, and calculates a correction coefficient. The correction coefficient is defined as the ratio between the two.

[0036] The power amount calculation unit 154 multiplies the voltage detection value Dvo (digital value) obtained by converting the voltage detection value Vo (analog value) detected by the voltage detection unit 14 using the AD converter 151 by the above-mentioned correction coefficient to calculate a corrected voltage detection value Dvo (digital value). Similarly, the power amount calculation unit 154 multiplies the current detection value Dio (digital value) obtained by converting the current detection value Io (analog value) detected by the current detection unit 13 using the AD converter 151 by the above-mentioned correction coefficient to calculate a corrected current detection value Dio (digital value).

[0037] The power amount calculation unit 154 multiplies the corrected voltage detection value Dvo (digital value) by the corrected current detection value Dio (digital value) to calculate a power value. The power amount calculation unit 154 calculates the power amount Dp by integrating the power values ​​calculated at each time. The output unit 155 transmits the power amount Dp calculated by the power amount calculation unit 154 to the external connection management device 30 (also referred to as a remote control setting device).

[0038] The external connection management device 30 and the power conversion device 10 may be connected by wire (e.g., a cable conforming to the RS-485 standard) or wirelessly (e.g., 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 (e.g., a LAN cable) or wirelessly (e.g., Wi-Fi). The external connection management device 30 functions as an operation terminal for operating the power conversion device 10 and as a gateway for connecting to an external network 6.

[0039] The network 6 is a general term for communication paths such as the Internet, a dedicated line, and a VPN (Virtual Private Network), and the communication medium and protocol are not important. For example, an optical fiber network, an ADSL network, a CATV network, a mobile communication network, a wireless LAN, a wired LAN, etc. can be used as a communication medium. For example, TCP (Transmission Control Protocol) / IP (Internet Protocol), UDP (User Datagram Protocol) / IP, Ethernet (registered trademark), etc. can be used as a communication protocol.

[0040] The external connection management device 30 transmits the amount of power Dp received from the control unit 15 of the power conversion device 10 as an amount of power to be metered 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 Dp measured by the power conversion device 10.

[0041] The external connection management device 30 can also relay the exchange of information other than the amount of power for metering between the power conversion device 10 and the server 7. For example, the external connection management device 30 can transmit a control signal (e.g., an output control command) received from the server 7 managed and operated by a power transmission and distribution company to the power conversion device 10. In addition, the external connection management device 30 can transmit log data of the voltage, current, and power of the solar cell 20a received from the power conversion device 10 to the server 7 managed and operated by the manufacturer of the distributed power system 1. Note that the function of the external connection management device 30 may be built into the power conversion device 10.

[0042] Fig. 2 is a waveform chart showing a specific example of temperature drift correction processing by the power conversion device 10 according to the first embodiment. Fig. 2 shows an example in which the power supply voltage generated by the power supply circuit 16 decreases with respect to the power supply voltage at the time of shipment from the factory due to the influence of temperature drift. Since a shunt regulator with high temperature characteristics is used in the reference voltage generation circuit 17, the reference voltage generation circuit 17 continues to output a constant reference voltage even if the temperature inside the power conversion device 10 rises.

[0043] When the power supply voltage generated by the power supply circuit 16 drops, the reference voltage detection value (digital value) output from the AD converter 151 rises even though the reference voltage value (analog value) input from the reference voltage generation circuit 17 to the AD converter 151 is constant. As a result, the correction coefficient calculated by the correction coefficient calculation unit 152 drops to a value lower than 1.

[0044] The voltage detection value (digital value) output from the AD converter 151 rises in response to a drop in the power supply voltage, but the voltage detection value (digital value) is multiplied by a correction coefficient to correct the voltage detection value (digital value) to a value from which the effects of temperature drift have been removed. Similarly, the current detection value (digital value) output from the AD converter 151 rises in response to a drop in the power supply voltage, but the current detection value (digital value) is multiplied by a correction coefficient to correct the current detection value (digital value) to a value from which the effects of temperature drift have been removed. In this way, a power calculation value (digital value) from which the effects of temperature drift have been removed is calculated.

[0045] 3 is a flowchart showing a flow of a temperature drift correction process by the power conversion device 10 according to the embodiment 1. A voltage detection value Vo (analog value), a current detection value Io (analog value), and a reference voltage are input to the AD converter 151 from the current detection unit 13, the voltage detection unit 14, and the reference voltage generation circuit 17, respectively (S10).

[0046] The AD converter 151 may be provided with a plurality of AD converters arranged in parallel for each conversion, or one AD converter may be shared in a time-division manner.

[0047] At the timing when a sampling trigger is input (Y in S11), the AD converter 151 samples the voltage detection value Vo (analog value), the current detection value Io (analog value), and the reference voltage Vref, respectively, in the sample-and-hold circuit (S12). The AD converter 151 converts the voltage detection value Vo (analog value), the current detection value Io (analog value), and the reference voltage sampled in the sample-and-hold circuit into a voltage detection value Dvo (digital value), a current detection value Dio (digital value), and a reference voltage detection value Dref (digital value), respectively, and outputs them (S13).

[0048] The correction coefficient calculation unit 152 calculates a correction coefficient based on the factory default value of the reference voltage detection value Dref registered in the storage unit 153 and the current value of the reference voltage detection value Dref (digital value) supplied from the AD converter 151 (S14).

[0049] The power amount calculation unit 154 multiplies a corrected voltage detection value Dvo (digital value) obtained by multiplying the voltage detection value Dvo (digital value) supplied from the AD converter 151 by the above-mentioned correction coefficient by a corrected current detection value Dio (digital value) obtained by multiplying the current detection value Dio (digital value) supplied from the AD converter 151 by the above-mentioned correction coefficient to calculate a power calculation value (S15). The power amount calculation unit 154 calculates the amount of power Dp by integrating the power calculation value calculated at each sampling timing over time (S16).

[0050] FIG. 4 is a diagram for explaining a distributed power system 1 according to a second embodiment. The distributed power system 1 shown in FIG. 4 is a power storage system, in which a storage battery 20b is installed instead of the solar cell 20a shown in FIG. 1. The storage battery 20b is capable of charging and discharging power, and a lithium ion storage battery, a nickel metal hydride storage battery, a lead storage battery, or the like is used. The storage battery 20b may be a stationary storage battery, or may be a storage battery mounted on an electric vehicle. Note that a capacitor such as an electric double layer capacitor or a lithium ion capacitor may be used instead of the storage battery.

[0051] The storage battery 20b is connected to the DC / DC converter 11, and charging and discharging are controlled by the DC / DC converter 11. In the second embodiment, the DC / DC converter 11 is a bidirectional DC / DC converter connected between the storage battery 20b and a DC bus for charging and discharging the storage battery 20b.

[0052] A converter control circuit (not shown) controls the charging and discharging of the DC / DC converter 11 based on a command value transmitted from the control unit 15. As the charging and discharging control, for example, constant current (CC) control or constant voltage (CV) control is possible.

[0053] In the second embodiment, the inverter 12 is a bidirectional inverter. The inverter 12 can convert DC power input from a DC bus into AC power and output the converted AC power to the distribution board 3, and can also convert AC power supplied from the system 2 via the distribution board 3 into DC power and output the converted DC power to the DC bus. In the second embodiment, when a current flows from the distribution board 3 to the power conversion device 10, power is purchased, and when a current flows from the power conversion device 10 to the distribution board 3, power is sold.

[0054] The components of the power conversion device 10 related to the temperature drift correction function are similar to those in the first embodiment.

[0055] Fig. 5 is a diagram for explaining a distributed power system 1 according to a third embodiment. The distributed power system 1 shown in Fig. 5 is a hybrid power storage system (also called a power generation and storage linked system), and includes a solar cell 20a, a storage battery 20b, a power conversion device 10, and an external connection management device 30. The power conversion device 10 according to the third embodiment includes a DC / DC converter 11a for the solar cell 20a, a DC / DC converter 11b for the storage battery 20b, an inverter 12, a CT sensor 13a, a current detection unit 13, a voltage detection unit 14, a control unit 15, a power supply circuit 16, and a reference voltage generation circuit 17. The DC / DC converter 11a for the solar cell 20a and the DC / DC converter 11b for the storage battery 20b are connected in parallel to a DC bus.

[0056] The components of the power conversion device 10 related to the temperature drift correction function are similar to those in the first embodiment.

[0057] As described above, according to the first to third embodiments, by adding a temperature drift correction function to the power conversion device 10, it is possible to realize low-cost and highly accurate power measurement in the power conversion device 10. This makes it unnecessary to install an independent watt-hour meter between the power conversion device 10 and the distribution board 3.

[0058] 6(a)-(b) are diagrams comparing the system configuration of the distributed power system 1 according to the first embodiment with the system configuration of a conventional distributed power system 1. In the conventional distributed power system 1 shown in FIG. 6(b), a watt-hour meter 8 is installed between a power conversion device 10 and a distribution board 3. When the watt-hour meter 8 is configured as a smart meter, the watt-hour meter 8 includes components equivalent to the CT sensor 13a, current detection unit 13, voltage detection unit 14, control unit 15, and power supply circuit 16 used in the power conversion device 10.

[0059] The watt-hour meter 8 does not include the DC / DC converter 11 and the inverter 12 provided in the power conversion device 10. Therefore, in the watt-hour meter 8, heat is not generated due to switching of the switching elements (MOSFET, IGBT, etc.) included in the DC / DC converter 11 and the inverter 12. In contrast, in the power conversion device 10, heat generated during switching of the switching elements included in the DC / DC converter 11 and the inverter 12 is trapped inside the housing. Therefore, when the watt-hour meter 8 and the power conversion device 10 use power supply circuits of the same order of magnitude, the power supply voltage generated by the power supply circuit 16 in the power conversion device 10 has lower accuracy.

[0060] A temperature drift correction function for compensating for a decrease in accuracy of the power supply voltage generated by the power supply circuit 16 is added to the power conversion device 10 according to the first to third embodiments. Therefore, the power conversion device 10 can measure power with the same accuracy as the watt-hour meter 8 even if parts and members having the same performance as existing hardware performance are used for the CT sensor 13a, the current detection unit 13, the voltage detection unit 14, the control unit 15, and the power supply circuit 16. Therefore, the watt-hour meter 8 can be omitted, and the power measurement function can be consolidated into the power measurement function of the power conversion device 10. This can reduce costs and simplify the system configuration.

[0061] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present disclosure.

[0062] In the above-mentioned embodiments 1-3, the distributed power system 1 has been described in which at least one of the solar cell 20a and the storage battery 20b is connected to the power conversion device 10 as a DC power source. In this regard, a fuel cell can also be used as a DC power source. The power conversion device 10 with the temperature drift correction function according to the present disclosure can also be used in the distributed power system 1 in which a fuel cell is used alone. Moreover, the power conversion device 10 with the temperature drift correction function according to the present disclosure can also be used in the distributed power system 1 in which a fuel cell and at least one of the solar cell 20a and the storage battery 20b are used.

[0063] In the above-described embodiments 1-3, the correction coefficient calculation unit 152 constantly calculates the correction coefficient. In this regard, the correction coefficient calculation unit 152 may update the correction coefficient only when the reference voltage detection value Dref (digital value) supplied from the AD converter 151 has changed by a set value or more, and may continue to use the correction coefficient being used when the reference voltage detection value Dref (digital value) has changed by less than the set value.

[0064] In the above-mentioned embodiments 1-3, an example was described in which the amount of power measured by the power conversion device 10 with the temperature drift correction function is transmitted to the outside as the amount of power for metering. In this regard, the amount of power measured by the power conversion device 10 with the temperature drift correction function may be used for power control in the power conversion device 10. In this case, the accuracy of the power control by the power conversion device 10 is improved. In addition, the amount of power measured by the power conversion device 10 with the temperature drift correction function may be used for monitor display. In this case, the accuracy of the amount of power displayed on the monitor is improved. In this way, a system configuration in which the existing watt-hour meter 8 and the power conversion device 10 with the temperature drift correction function coexist is also included in the scope of the present disclosure.

[0065] The embodiment may be specified by the following items.

[0066] [Item 1] a DC / DC converter (11) that controls the voltage of DC power supplied from a DC power supply (20); an inverter (12) that converts DC power supplied from the DC / DC converter (11) into AC power; a voltage detection unit (14) that detects a voltage of a distribution line between the inverter (12) and a distribution board (3) connected to a power system (2); a current detection unit (13) for detecting a current flowing through the distribution line; a control unit (15) that calculates an amount of power output from the power conversion device (10) or an amount of power input from the power system (2) to the power conversion device (10) based on the voltage value detected by the voltage detection unit (14) and the current value detected by the current detection unit (13); and a power supply circuit (16) that generates a power supply voltage for the control unit (15); a reference voltage generating circuit (17) that generates a reference voltage based on a power supply voltage generated by the power supply circuit (16), The control unit (15) calculates the amount of power in which an error caused by fluctuations in the power supply voltage has been corrected based on a relationship between a preset reference voltage detection value and a reference voltage detection value based on a reference voltage supplied from the reference voltage generation circuit (17). This makes it possible to realize highly accurate power measurement at low cost in the power conversion device (10). [Item 2] 2. The power conversion device (10) according to item 1, wherein the control unit (15) outputs the calculated amount of power to the outside as an amount of power to be measured. This makes it possible to omit the installation of a watt-hour meter. [Item 3] The control unit (15) 3. The power conversion device (10) according to item 1 or 2, further comprising an AD converter (151) that converts the voltage detected by the voltage detection unit (14), the current detected by the current detection unit (13), and the reference voltage generated by the reference voltage generation circuit (17) into digital values, respectively. This allows the amount of power to be calculated with high precision by digital calculation. [Item 4] 4. The power conversion device (10) according to item 3, wherein the preset reference voltage detection value is set before shipment based on a value obtained by converting a reference voltage supplied from the reference voltage generation circuit (17) by the AD converter (151). According to this, by preparing a reference value for the standard voltage detection value that also reflects the individual difference of each power conversion device (10), it is possible to estimate the effect of temperature drift with high accuracy. [Item 5] The control unit (15) a correction coefficient calculation unit (152) that calculates a correction coefficient by comparing the preset reference voltage detection value with a reference voltage detection value obtained by converting a reference voltage supplied from the reference voltage generation circuit (17) into a digital value by the AD converter (151); a power amount calculation unit (154) which multiplies a voltage value obtained by converting a voltage value detected by the voltage detection unit (14) into a digital value by the AD converter (151) by the correction coefficient, multiplies a current value obtained by converting a current value detected by the current detection unit (13) into a digital value by the AD converter (151) by the correction coefficient, multiplies the corrected voltage value by the current value to calculate a power value, and calculates a power amount by integrating the calculated power value; The power conversion device (10) according to item 3 or 4, further comprising: This enables the control unit (15) of the power conversion device (10) to calculate the amount of power with high accuracy, with the effect of temperature drift removed. [Item 6] 6. The power conversion device (10) according to any one of items 1 to 5, wherein the DC power supply (20) is a solar cell (20a), a storage battery (20b), or a fuel cell. This allows the amount of power supplied from the distributed power sources to be measured by the power conversion device (10) connected to the distributed power sources. [Item 7] A DC power source (20); A power conversion device (10) according to any one of items 1 to 6; A distributed power system (1) comprising: This makes it possible to realize highly accurate power measurement at low cost in the power conversion device (10). [Explanation of symbols]

[0067] 1 distributed power system, 2 system, 3 distribution board, 4 load, 5 router device, 6 network, 7 server, 8 power meter, 10 power conversion device, 11 DC / DC converter, 12 inverter, 13 current detection unit, 13a CT sensor, 14 voltage detection unit, 15 control unit, 151 AD converter, 152 correction coefficient calculation unit, 153 memory unit, 154 power amount calculation unit, 155 output unit, 16 power supply circuit, 17 reference voltage generation circuit, 20a solar cell, 20b storage battery, 30 external connection management device.

Claims

1. A power conversion device used as a specified meter, A DC / DC converter that controls a voltage of DC power supplied from a DC power source; an inverter for converting DC power supplied from the DC / DC converter into AC power; a voltage detection unit that detects a voltage of a distribution line between the inverter and a distribution board connected to a power grid; a current detection unit that detects a current flowing through the power distribution line; a control unit that calculates an amount of power output from the power conversion device or an amount of power input from the power grid to the power conversion device based on a voltage value detected by the voltage detection unit and a current value detected by the current detection unit; a power supply circuit that generates a power supply voltage for the control unit; a reference voltage generating circuit that generates a reference voltage based on a power supply voltage generated by the power supply circuit, The control unit calculates the amount of power in which an error caused by fluctuations in the power supply voltage has been corrected based on a relationship between a preset reference voltage detection value and a reference voltage detection value based on a reference voltage supplied from the reference voltage generation circuit.

2. The power conversion device according to claim 1 , wherein the control unit outputs the calculated amount of power to an outside source as an amount of power to be measured.

3. The control unit is 3. The power conversion device according to claim 1, further comprising an AD converter that converts the voltage detected by the voltage detection unit, the current detected by the current detection unit, and the reference voltage generated by the reference voltage generation circuit into digital values.

4. 4. The power conversion device according to claim 3, wherein the preset reference voltage detection value is set before shipment based on a value obtained by converting a reference voltage supplied from the reference voltage generating circuit by the AD converter.

5. The control unit is a correction coefficient calculation unit that calculates a correction coefficient by comparing the preset reference voltage detection value with a reference voltage detection value obtained by converting a reference voltage supplied from the reference voltage generation circuit into a digital value by the AD converter; a power amount calculation unit that multiplies a voltage value obtained by converting a voltage value detected by the voltage detection unit into a digital value by the AD converter by the correction coefficient, multiplies a current value obtained by converting a current value detected by the current detection unit into a digital value by the AD converter by the correction coefficient, calculates a power value by multiplying the corrected voltage value by the current value, and calculates a power amount by integrating the calculated power value; The power conversion device according to claim 3 or 4, further comprising:

6. 6. The power conversion device according to claim 1, wherein the DC power supply is a solar cell, a storage battery, or a fuel cell.

7. A DC power source; The power conversion device according to any one of claims 1 to 6, A distributed power system comprising:

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