JP2018125922A - Power conversion device and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device which reduces the occurrence of an unnecessary operation of a breaker.SOLUTION: The power conversion device comprises an acquisition unit that acquires a ground-fault current value or a form of a solar cell, and a control unit. The control unit acquires a lowest sensitivity current value among sensitivity current values of breakers provided between the power conversion device and a commercial power system, and acquires known information. The known information includes respective combinations of known ground-fault current values or known forms of respective power generation modules and known values of inrush currents due to the ground capacitance of respective power generation module in multiple kinds of power generation modules. Furthermore, the control unit calculates a predicted value of inrush current generated by the ground capacitance of the solar cell on the basis of the ground-fault current value or the form of the solar cell and the known information. In addition, the control unit determines whether or not the calculated predicted value is greater than a determination threshold based on the minimum sensitivity current value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device and a control method thereof.

  Solar cells have a larger ground capacitance than other devices. Therefore, the circuit breaker provided between the solar cell and the commercial power system is operated when it should not be operated due to the ground capacitance of the solar cell (hereinafter referred to as “unnecessary operation”). There is.

  For example, if a ground capacitance exists, a ground fault current that flows to the ground via the ground capacitance is generated. When a large ground fault current (inrush current) occurs temporarily due to the large earth capacitance of the solar cell, a large current flows into the circuit breaker connected to the commercial power system, and the circuit breaker operates unnecessarily. May end up.

  Therefore, methods for preventing an unnecessary operation of the circuit breaker due to a ground fault current are disclosed (Patent Documents 1 and 2). In Patent Document 1, when a ground fault current is detected, an unnecessary operation of the circuit breaker is prevented by interrupting a current that enters the circuit breaker. Further, in Patent Document 2, when a ground fault current is detected, an unnecessary operation of the circuit breaker is prevented by reducing a current flowing into the circuit breaker.

JP 2001-161032 A JP 2002-252986 A

  By the way, the circuit breaker may operate unnecessary due to improper setting of the circuit breaker. For example, the circuit breaker operates based on the set sensitivity current value. If the sensitivity current value is inappropriately set for the solar cells to be combined, the circuit breaker may operate unnecessarily.

  Here, in Patent Documents 1 and 2, when a ground fault current occurs, that is, when a phenomenon that causes an unnecessary operation of the circuit breaker occurs, an unnecessary operation of the circuit breaker is prevented by executing a predetermined process. Is done. In order to further reduce the occurrence of unnecessary circuit breaker operation, it is desirable to determine whether or not the circuit breaker settings are appropriate before the occurrence of the circuit breaker unnecessary operation occurs, that is, in advance. It is.

  The objective of this indication made in view of this point is to provide the power converter device which reduces generation | occurrence | production of the unnecessary operation | movement of a circuit breaker more.

  A power conversion device according to an embodiment of the present disclosure is a power conversion device that converts DC power generated by a solar cell including a plurality of power generation modules into AC power. The power converter includes an acquisition unit that acquires a ground fault current value or a format of the solar cell, and a control unit. The control unit acquires a minimum sensitivity current value among sensitivity current values of a circuit breaker provided between the power conversion device and the commercial power system, and acquires known information. The known information includes each combination of a known ground fault current value or type of each power generation module in a plurality of types of power generation modules and a known value of the inrush current due to the ground capacitance of each power generation module. Further, the control unit calculates a predicted value of an inrush current generated due to the ground capacitance of the solar cell based on the ground fault current value or type of the solar cell and the known information. In addition, the control unit determines whether or not the calculated predicted value is larger than a determination threshold value based on the minimum sensitivity current value.

  A control method for a power conversion device according to an embodiment of the present disclosure is a control method for a power conversion device that converts DC power generated by a solar cell including a plurality of power generation modules into AC power. The method for controlling the power converter includes a step of acquiring a ground fault current value or a format of the solar cell, and a sensitivity current value of a circuit breaker provided between the power converter and a commercial power system. Obtaining a sensitivity current value. Furthermore, the control method of the power converter includes each of a known ground fault current value or type of each power generation module in a plurality of types of power generation modules and a known value of an inrush current due to the ground capacitance of each power generation module. Obtaining known information including the combination. In addition, the method for controlling the power converter calculates a predicted value of the inrush current generated due to the ground capacitance of the solar cell based on the ground fault current value or type of the solar cell and the known information. Including the steps of: In addition, the method for controlling the power converter includes a step of determining whether or not the calculated predicted value is larger than a determination threshold value based on the minimum sensitivity current value.

  According to the power converter concerning one embodiment of this indication, generation | occurrence | production of the unnecessary operation | movement of a circuit breaker can be reduced more.

It is a functional block diagram showing a schematic structure of a power conversion system concerning a 1st embodiment of this indication. It is a functional block diagram which shows schematic structure of the electricity distribution panel shown in FIG. It is a table | surface which shows the known information which concerns on 1st Embodiment of this indication. 6 is a flowchart illustrating an example of an operation of the power conversion device according to the first embodiment of the present disclosure. It is a figure which shows a mode when an inrush current generate | occur | produces in the power conversion system shown in FIG. It is a functional block diagram showing a schematic configuration of a distribution board according to Modification 1. It is a table | surface which shows the known information which concerns on 2nd Embodiment of this indication. 6 is a first flowchart illustrating an example of an operation of a power conversion device according to a second embodiment of the present disclosure. 12 is a second flowchart illustrating an example of an operation of the power conversion device according to the second embodiment of the present disclosure.

  Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings.

(First embodiment)
The power conversion system 1 including the power conversion device 30 according to the first embodiment of the present disclosure will be described with reference to FIG. The power conversion system 1 is provided in a customer facility. The power conversion system 1 is connected to a commercial power system 2 and supplies power to a load device 3 installed in a customer facility. The power conversion system 1 includes a solar cell 10, a storage battery 11, a distribution board 20, and a power conversion device 30. Although the power conversion system 1 which concerns on this embodiment is provided with the one solar cell 10 and the one storage battery 11, it is not limited to this. The number of solar cells and the number of power storage devices included in the power conversion system 1 may be two or more.

  In FIG. 1, a solid line connecting each functional block indicates a flow of power. Moreover, in FIG. 1, the broken line which connects each function block shows the flow of the control signal or the information communicated. The communication indicated by the broken line may be wired communication or wireless communication.

  The solar cell 10 includes a plurality of power generation modules. The solar cell 10 generates direct-current power from sunlight energy by a plurality of power generation modules. The solar cell 10 supplies the generated DC power to the power converter 30.

  Further, the solar cell 10 has a ground capacitance C1. The electrode of the ground capacitance C1 is, for example, a power generation cell and a frame of a power generation module. The dielectric of the ground capacitance C1 is, for example, a sealing material and a glass panel for sealing the power generation cell and the frame. The capacitance value of the ground capacitance C1 varies depending on the type of the power generation cell (for example, crystalline silicon, CIS compound semiconductor), the stacked structure of the power generation module, the material such as the sealing material used for the power generation module, and the like. In other words, the capacitance value of the ground capacitance C <b> 1 varies depending on the type of power generation module included in the solar cell 10. For example, the value of the ground capacitance of a solar cell using a CIS compound semiconductor is often larger than the value of the ground capacitance of a solar cell using crystalline silicon.

  In the power conversion system 1, a ground fault current is generated by the ground capacitance C1. Further, in the power conversion system 1, an inrush current that flows from the commercial power system 2 to the power conversion device 30 is generated due to the ground capacitance C1. The inrush current is generated, for example, when a large current temporarily flows from the commercial power system 2 to the ground capacitance C1 when no charge is accumulated in the ground capacitance C1. Here, both the ground fault current and the inrush current are generated due to the ground capacitance C1. Therefore, both the ground fault current value and the inrush current value depend on the capacitance value of the ground capacitance C1. As described above, the capacitance value of the ground capacitance C <b> 1 varies depending on the type of power generation module included in the solar cell 10. Therefore, the ground fault current value and the inrush current value also vary depending on the type of power generation module included in the solar cell 10.

  The storage battery 11 includes a lithium ion battery and a nickel metal hydride battery. The storage battery 11 supplies DC power to the power converter 30 by discharging the charged power. In addition, the storage battery 11 is charged with power from the commercial power system 2 and the solar battery 10.

  The distribution board 20 is provided between the power conversion device 30 and the commercial power system 2. The distribution board 20 distributes the power supplied from the power converter 30 and the power supplied from the commercial power system 2 to the load device 3.

  Moreover, the distribution board 20 is provided with the circuit breakers 21 and 22 as shown in FIG. The circuit breakers 21 and 22 operate based on the sensitivity current value set for each. In the present embodiment, the sensitivity current value of the circuit breaker 21 will be described as being smaller than the sensitivity current value of the circuit breaker 22. Specifically, for example, even if the circuit breaker 21 and the circuit breaker 22 are set to the same 30 mA sensitivity current value, the sensitivity current of the circuit breaker 21 is reduced due to individual differences in manufacturing. There is a case.

  The circuit breaker 21 is, for example, a main power circuit breaker using an earth leakage breaker. The circuit breaker 21 is provided between the load device 3 and the commercial power system 2. In the present embodiment, the circuit breaker 21 is provided between the power converter 30 and the load device 3 and the commercial power system 2.

  When the circuit breaker 21 detects a current value larger than the sensitivity current value, the circuit breaker 21 disconnects the commercial power system 2 from the load device 3 and the power conversion device 30. The sensitivity current value of the circuit breaker 21 is set based on, for example, the type of the load device 3 and the total capacity of the load device 3. The selection of the circuit breaker 21 or the setting of the changeover switch of the sensitivity current value is performed by a contractor when the circuit breaker 21 is installed, for example.

  The circuit breaker 22 is a solar power generation breaker, for example. The circuit breaker 22 is provided between the solar cell 10 and the commercial power system 2. In the present embodiment, the circuit breaker 22 is provided between the power conversion device 30, the commercial power system 2, and the load device 3.

  When the breaker 22 detects a current value larger than the sensitivity current value, the breaker 22 disconnects the commercial power system 2 and the load device 3 from the power conversion device 30. The sensitivity current value of the circuit breaker 22 is set based on, for example, the type of the solar battery 10. Selection of the circuit breaker 22 or setting of the changeover switch of the sensitivity current value is performed by a contractor when the solar cell 10 is installed.

  In FIG. 1, the power conversion device 30 converts the DC power generated by the solar cell 10 and the DC power discharged by the storage battery 11 into AC power. The power conversion device 30 is a so-called multi-DC link type. The power conversion device 30 includes a DC power transformation unit 31A, 31B, an orthogonal transformation unit 32, a filter unit 33, a grid interconnection switch 34, an acquisition unit 35, a communication unit 36, a display unit 37, and a storage unit. 38 and a control unit 39. In addition, although the output of the power converter device 30 which concerns on this embodiment is a single phase 3 wire system, the output format of a power converter device is not restricted to this, For example, even if it is a single phase 2 wire system or a 3 phase system Good.

  The DC power transformers 31A and 31B are, for example, DC / DC converters. The direct-current power transformer 31 </ b> A adjusts the voltage of the direct-current power supplied from the solar cell 10. The DC power transformer 31 </ b> B adjusts the voltage of DC power supplied from the storage battery 11. Further, the DC power transformer 31 </ b> B adjusts the voltage of the DC power supplied from the DC power transformer 31 </ b> A or the orthogonal transform unit 32 when the storage battery 11 is charged.

  The orthogonal transform unit 32 is, for example, an inverter. The orthogonal transform unit 32 converts the DC power supplied from the DC power transformers 31A and 31B into AC power. Moreover, the orthogonal transformation part 32 converts the alternating current power supplied from the commercial power system 2 into direct current power when charging the storage battery 11.

  The filter unit 33 includes coils L1 and L2 and capacitors C2 and C3. The filter unit 33 reduces AC power noise output from the orthogonal transform unit 32.

  The grid interconnection switch 34 is provided between the filter unit 33 and the acquisition unit 35. The grid interconnection switch 34 is switched on / off based on the control of the control unit 39. The grid interconnection switch 34 is turned on when the power converter 30 is grid-connected. The grid connection switch 34 is turned off when the power converter 30 is disconnected.

  The acquisition unit 35 acquires the ground fault current value of the solar cell 10. For example, the acquisition unit 35 is a current sensor that detects an actual measurement value of a ground fault current value by measurement. In the present embodiment, the acquisition unit 35 is more specifically configured by a split-type clamp sensor that can be attached after installation of an electric wire.

  The acquisition unit 35 may be provided between the output side of the DC power transformation units 31 </ b> A and 31 </ b> B, in other words, the downstream side of the circuit breaker 22 of the distribution board 20. In the present embodiment, the acquisition unit 35 is provided between the grid interconnection switch 34 and the distribution board 20.

  An electric wire extending from the grid interconnection switch 34 to the distribution board 20 is inserted into the acquisition unit 35. In the present embodiment, U-phase, O-phase, and W-phase wires extending from the grid interconnection switch 34 to the distribution board 20 are inserted. Further, in the case of a two-wire system, such as between the direct-current power transformer 31A and the orthogonal transform unit 32, the acquisition unit 35 is inserted with electric current forward and return wires.

  The acquisition unit 35 measures the ground fault current value of the solar cell 10 from the difference current flowing in the inserted electric wire. The acquisition unit 35 notifies the control unit 39 of the ground fault current value as a signal. Since the current value measured by the clamp sensor is in the form of a voltage value, the control unit 39 converts it into a current value. Examples of the method for measuring the ground fault current include a zero-phase current monitoring method, a resistance-divided midpoint grounding method, and an AC signal injection method. In the present embodiment, it is assumed that the ground fault current value is measured from the difference between the current values by the zero-phase current monitoring method.

  The communication unit 36 communicates with other devices via a network. For example, the communication part 36 communicates with the server of the manufacturing company of the solar cell 10 via a network.

  The display unit 37 displays various information related to the power conversion device 30 based on the signal acquired from the control unit 39. For example, when the display unit 37 acquires a warning signal from the control unit 39, the display unit 37 displays a warning screen. For example, when the display unit 37 acquires a predetermined signal from the control unit 39, the display unit 37 displays an input reception screen for causing the power conversion device 30 to execute each function.

  The display unit 37 includes a touch panel formed of a transparent member and functions as an interface that receives a user operation.

  The storage unit 38 stores a program describing information necessary for processing of the power conversion device 30 and processing contents for realizing each function of the power conversion device 30. For example, the storage unit 38 stores sensitivity current values of the circuit breakers 21 and 22, known information, a ground fault current value of the solar cell 10, and the like. The known information will be described later.

  The control unit 39 controls and manages the entire power conversion device 30. The control unit 39 is configured by any suitable processor such as a general-purpose CPU (central processing unit) that reads software for executing processing of each function. Or the control part 39 may be comprised by the processor for exclusive use specialized in the process of each function, for example.

  The control unit 39 according to the present embodiment determines whether or not there is a possibility that the circuit breaker may operate unnecessary due to the inrush current generated due to the ground capacitance C1 of the solar cell 10. Hereinafter, this determination process will be described. Note that the control unit 39 may automatically execute this determination process, for example, about once a month. Or the control part 39 may perform this determination process, for example, when the execution request | requirement of this determination process is acquired from the display part 37. FIG. The execution request for the determination process can be input from the display unit 37 by, for example, a contractor installing the solar battery 10.

  The control unit 39 acquires at least the minimum sensitivity current value among the circuit breakers 21 and 22 provided between the power conversion device 30 and the commercial power system 2. In the present embodiment, the control unit 39 acquires the sensitivity current value of the circuit breaker 21 as the minimum sensitivity current value. The control unit 39 may acquire the sensitivity current value of the circuit breaker 21 from the storage unit 38 that stores the sensitivity current value in advance. Alternatively, the control unit 39 may acquire the sensitivity current value of the circuit breaker 21 from the display unit 37 when the contractor inputs the sensitivity current value of the circuit breakers 21 and 22 from the display unit 37, for example. In obtaining the minimum sensitivity current value, individual differences in each circuit breaker need not be considered.

  The control unit 39 acquires known information. The known information includes each combination of a known ground fault current value of each power generation module and a known value of the inrush current due to the ground capacitance of each power generation module in a plurality of types of power generation modules. Furthermore, the known information may include the type of each power generation module. For example, the control unit 39 acquires the known information from the storage unit 38 that stores the known information in advance. Alternatively, the control unit 39 may acquire known information from a server of a business operator such as a power generation module manufacturing company on the network via the communication unit 36.

  FIG. 3 shows known information according to the first embodiment of the present disclosure. Examples of the plurality of types of power generation modules include power generation module A to power generation module E. The solar cell 10 has one or more solar cell strings in which a predetermined number of power generation modules are connected in series or in parallel. The solar cell string is configured by connecting the same type of power generation modules. In the present embodiment, the known ground fault current value is caused by the ground capacitance of the power generation module A to the power generation module E when the power generation module A to the power generation module E generates power at the rated voltage value, respectively. This is the value of the ground fault current that occurs. In the present embodiment, the known ground fault current value and the known inrush current value are values per one of the power generation modules A to E.

  The known ground fault current value of the power generation module A is 0.30 [mA], and the known value of the inrush current due to the ground capacitance of the power generation module A is 0.70 [mA]. The model of the power generation module A is “ΔΔ01”.

  The known ground fault current value of the power generation module B is 0.50 [mA], and the known value of the inrush current due to the ground capacitance of the power generation module B is 1.20 [mA]. The model of the power generation module B is “ΔΔ02”.

  The known ground fault current value of the power generation module C is 0.70 [mA], and the known value of the inrush current due to the ground capacitance of the power generation module C is 1.50 [mA]. The model of the power generation module C is “☆☆ 21”.

  The known ground fault current value of the power generation module D is 0.10 [mA], and the known value of the inrush current due to the ground capacitance of the power generation module D is 0.20 [mA]. The type of the power generation module D is “□□ 30”.

  The known ground fault current value of the power generation module E is 0.13 [mA], and the known value of the inrush current due to the ground capacitance of the power generation module E is 0.25 [mA]. The model of the power generation module E is “□□ 60”.

  In the present embodiment, the known ground fault current value is based on the rated voltage value of the power generation module A to the power generation module E, but is not limited thereto. For example, the known ground fault current value may be a value when the power generation module A to the power generation module E each generate power at an arbitrary voltage value (different from the rated voltage value). In the present embodiment, the known ground fault current value is a value per one of the power generation modules A to E, but is not limited thereto. For example, the known ground fault current value may be a value per solar cell string in which a predetermined number of power generation modules E to E are connected.

  The control unit 39 acquires the ground fault current value of the solar cell 10 measured by the acquisition unit 35 when the electric charge is sufficiently accumulated in the ground capacitance C1. For example, the control unit 39 acquires the ground fault current value of the solar cell 10 measured by the acquisition unit 35 when the solar cell 10 is generating power. Further, when the solar cell 10 is generating power, the generated voltage of the solar cell 10 may be stable.

  In the present embodiment, the control unit 39 acquires the ground fault current value of the solar cell 10 that is generated when the solar cell 10 is generating power at the rated voltage value. When the known ground fault current value is a value when the power generation module A to the power generation module E is generating power at a voltage value (different from the rated voltage value), the control unit 39 indicates that the solar cell 10 is The ground-fault current value of the solar cell 10 generated when generating power at the voltage value is acquired.

  The control unit 39 calculates a predicted value of the inrush current generated due to the ground capacitance C1, based on the acquired ground fault current value of the solar cell 10 and the known information. An example of calculating the predicted value of inrush current will be described in <Calculation Example 1 of predicted value of inrush current> below.

  The control unit 39 determines whether or not the predicted value of the inrush current is larger than the determination threshold value. The determination threshold is a value based on the minimum sensitivity current value among the at least one circuit breakers 21 and 22 acquired by the control unit 39. The determination threshold value may be, for example, a value that is smaller than the minimum sensitivity current value (the sensitivity current value of the circuit breaker 21) by a first predetermined value. The first predetermined value includes, for example, the ground fault current value of another device (the power converter 30 and the load device 3) provided between the solar cell 10 and the circuit breaker 21. Alternatively, the determination threshold may be, for example, a predetermined ratio (for example, 2/3) of the sensitivity current value of the circuit breaker 21.

  When the control unit 39 determines that the predicted value of the inrush current is larger than the determination threshold, the control unit 39 generates a warning signal. The control unit 39 may transmit the generated warning signal to the display unit 37 of the power conversion device 30 or may transmit the warning signal to a construction company server on the network via the communication unit 36.

  For example, when the determination process is periodically executed, the control unit 39 may generate a warning signal for causing the display unit 37 to display a warning screen for the user and transmit the warning signal to the display unit 37. The warning screen for the user includes, for example, a warning for the user that “the breaker specification may be inappropriate. Please contact us”. In addition, the control unit 39 may generate a warning signal for the construction company and transmit it to the server of the construction company on the network via the communication unit 36.

  Further, for example, when the determination process is executed based on the input of the execution request to the display unit 37, the control unit 39 generates a warning signal for displaying the warning screen for the contractor on the display unit 37, and displays the warning signal. You may transmit to the part 37. The warning screen for the contractor includes, for example, a specific cause such as “the ground fault current value may exceed the sensitivity current value of the breaker”.

<Calculation example 1 of predicted value of inrush current>
The control unit 39 subtracts the ground fault current value of the power conversion device 30 from the ground fault current value of the solar cell 10 to calculate a subtraction value. As the ground fault current value of the power conversion device 30, a value determined as the specification of the power conversion device 30 may be used. At this time, the control unit 39 may acquire the ground fault current value of the power conversion device 30 from the storage unit 38 stored in advance. Alternatively, the control unit 39 may acquire the ground fault current value of the power conversion device 30 from the server of the manufacturer of the power conversion device 30 on the network via the communication unit 36.

  The control unit 39 subtracts the ground fault current value of the power converter 30 from the ground fault current value of the solar cell 10 and then subtracts the ground fault current value of the load device 3 to calculate a subtraction value. Also good. When the load device 3 includes an electric device that is used while being grounded, such as a washing machine, the load device 3 also generates a ground fault current. When the minimum sensitivity current value is the circuit breaker 22, the ground fault current value of the load device 3 need not be considered.

  The control unit 39 calculates the divided current value by dividing the calculated subtraction value by the number of power generation modules included in the solar cell 10. The control unit 39 may acquire the number of power generation modules included in the solar cell 10 from the storage unit 38 stored in advance or may be acquired from the display unit 37. For example, when the number of power generation modules is input from the display unit 37 by the contractor, the control unit 39 acquires the number of power generation modules included in the solar cell 10 from the display unit 37.

  The control unit 39 selects the known value of the inrush current combined with the known ground fault current value closest to the divided current value from the known information. For example, when the divided current value is 0.65 [mA], the known ground fault current value closest to the divided current value in the known information is the ground fault current value 0.7 [mA] of the power generation module C. It is. At this time, the control unit 39 selects the known value 1.5 [mA] of the inrush current of the power generation module C.

  Note that the control unit 39 may generate a warning signal when it is determined that the divided current value is greater than each known ground fault current value included in the known information by a second predetermined value or more. The second predetermined value can be set based on, for example, a measurement error of the acquisition unit 35 or a standard error of a known ground fault current value.

  The control unit 39 calculates a predicted value of the inrush current by multiplying the known value of the selected inrush current by the number of power generation modules included in the solar cell 10. After multiplication, the control unit 39 may add the ground fault current value of the power conversion device 30 to calculate the predicted value of the inrush current. Alternatively, after multiplication, the control unit 39 may calculate the predicted value of the inrush current by adding the ground fault current value of the power conversion device 30 and the ground fault current value of the load device 3.

[System operation]
Hereinafter, an example of the operation of the power conversion device 30 according to the first embodiment of the present disclosure will be described with reference to FIG. The control unit 39 starts the determination process when acquiring a determination process execution request from the display unit 37. The determination process execution request is generally input from the display unit 37 by the contractor in a state where the grid connection switch 34 is turned off after the installation of the solar cell 10 is completed. Moreover, the control part 39 complete | finishes a determination process, when making the power converter device 30 transfer to power-off after the start of a determination process.

  The control unit 39 acquires the sensitivity current value of the circuit breaker 22 as the minimum sensitivity current value from the display unit 37, for example, and acquires known information from the storage unit 38, for example (step S101). The control part 39 determines whether the solar cell 10 is generating electric power (step S102). When it is determined that the solar cell 10 is generating power (step S102: Yes), the control unit 39 proceeds to the process of step S103. On the other hand, when it is determined that the solar cell 10 is not generating power (step S102: No), the control unit 39 repeatedly performs the process of step S102 until the solar cell 10 starts generating power.

  In the process of step S103, the control unit 39 turns on the grid interconnection switch 34.

  The grid interconnection switch 34 is turned on when the solar cell 10 is generating electric power by the processes in steps S102 and S103. In other words, the grid interconnection switch 34 is kept off when charges are not accumulated in the ground capacitance C1 by the processing of steps S102 and S103. Thereby, in this embodiment, before completing a determination process, it can prevent that an inrush current generate | occur | produces and a circuit breaker will carry out unnecessary operation | movement.

  In the process of step S104, the control unit 39 acquires the ground fault current value of the solar cell 10 measured by the acquisition unit 35. In the process of step S105, the control unit 39 calculates a predicted value of the inrush current based on the ground fault current value of the solar cell 10 measured by the acquisition unit 35 and the known information acquired in the process of step S101.

  In the process of step S106, the control unit 39 determines whether or not the predicted value of the inrush current is larger than the determination threshold value. When the control unit 39 determines that the predicted value of the inrush current is larger than the determination threshold (step S106: Yes), the control unit 39 proceeds to the process of step S107. On the other hand, when the control unit 39 determines that the predicted value of the inrush current is smaller than the determination threshold (step S106: No), the control unit 39 proceeds to step S108.

  In the process of step S107, the control unit 39 generates a warning signal. After a predetermined time has elapsed (step S108), the control unit 39 performs the process of step S109 in the same manner as the process of step S102. When it is determined that the solar cell 10 is generating power (step S109: Yes), the control unit 39 proceeds to the process of step S104. On the other hand, when it determines with the control part 39 not generating the solar cell 10 (step S109: No), it repeats the process of step S109 until the solar cell 10 starts an electric power generation.

  As described above, in the power conversion device 30 according to the first embodiment, the predicted value of the inrush current is calculated based on the ground fault current value measured by the acquisition unit 35 and the known information of a plurality of types of power generation modules. Furthermore, in this embodiment, it is determined whether the calculated predicted value of the inrush current is larger than a determination threshold value. As described above, in the present embodiment, it is possible to determine whether or not the setting of the circuit breaker 21 is appropriate before the inrush current is generated, that is, in advance.

  Here, the setting or the like of the circuit breaker 21 may be inappropriate. For example, the contractor may erroneously set the sensitivity current value of the circuit breaker 21 due to an input error. For example, a contractor may select the specification of the circuit breaker 21 by mistake. Thus, even when the setting of the circuit breaker 21 is inappropriate, according to the power conversion device 30 according to the present embodiment, the setting of the circuit breaker 21 or the like can be corrected in advance by a contractor or the like. Therefore, according to the power converter 30 which concerns on this embodiment, generation | occurrence | production of the unnecessary operation | movement of the circuit breaker 21 can be reduced more.

  Furthermore, according to the power conversion device 30 according to the first embodiment, the control unit 39 can acquire known information from the server of the power generation module manufacturing company on the network via the communication unit 36. Thereby, in this embodiment, the latest known information can be acquired. Furthermore, more combinations of known ground fault current values and known values of inrush current can be obtained.

  In addition, according to the power conversion device 30 according to the present embodiment, it is possible to prevent a situation that can be caused by an unnecessary operation of the circuit breaker 21 as described in <Situations that can be caused by an unnecessary action> below.

<Situations that can occur due to unnecessary operations>
Hereinafter, a situation that may occur due to an unnecessary operation of the circuit breaker 21 will be described. First, generation of an inrush current will be described with reference to FIG.

  The inrush current is generated when the grid interconnection switch 34 is turned on from off when no electric charge is accumulated in the ground capacitance C1.

  For example, during the daytime period when the solar cell 10 is generating power, the charge amount of the ground capacitance C1 is maintained constant by the generated current of the solar cell 10, so that the grid interconnection switch 34 is turned on from off. Even if it does, inrush current does not occur, only a fixed amount of ground fault current continues to flow. In addition, for example, even in the night time zone when the solar cell 10 stops power generation, if the grid interconnection switch 34 is on, the charge amount of the ground capacitance C1 is from the commercial power system 2. Since the current is kept constant, no inrush current is generated. However, if a power failure occurs in the commercial power system 2 and the grid interconnection switch 34 is turned off at night when the solar cell 10 stops generating power, the current from the commercial power system 2 to the ground capacitance C1 is reduced. The charge amount of the ground capacitance C1 is reduced and is reduced. In addition, if the time during which the commercial power system 2 is out of power, that is, the time during which the grid connection switch 34 is turned off, is increased to some extent, the ground capacitance C1 is not charged. At this time, when the commercial power system is restored and the grid interconnection switch 34 is turned on from off, a current flows from the commercial power system 2 to the ground capacitance C1 at once (see the thick arrow).

  Here, in the power converter connected only to the solar cell, when the commercial power system is restored, the grid interconnection switch is switched from off to on in order to use the generated power of the solar cell. When the grid connection switch is switched from off to on, no inrush current is generated because the solar cell is generating power. In addition, when the solar cell stops power generation, such a power converter does not sell the power generated by the solar cell to the power company, and the grid interconnection switch can be switched from off to on. Inrush current does not occur.

  However, in the multi-DC link type power conversion device 30, system interconnection with a distributed power source such as the storage battery 11 is desired even when the solar cell 10 stops power generation. When the grid connection switch 34 is switched from OFF to ON in such a situation, an inrush current is generated.

  If the generated inrush current value is larger than the sensitivity current value of the circuit breaker 21, the circuit breaker 21 will perform an unnecessary operation. That is, the circuit breaker 21 disconnects the commercial power system 2 and the load device 3. When the load device 3 is disconnected from the commercial power system 2, even if the commercial power system 2 is restored, the power supply from the commercial power system 2 to the load device 3 may be interrupted. Furthermore, when the circuit breaker 21 is provided between the commercial power system 2 and the power conversion device 30 as in the present embodiment, the circuit breaker 21 also disconnects the commercial power system 2 and the power conversion device 30. When the power conversion device 30 is disconnected from the commercial power system 2, a situation may occur in which the power of the storage battery 11 cannot be supplied to the load device 3. Furthermore, it becomes impossible to charge the storage battery 11 with the electric power from the commercial power system 2 during the night time when the electricity bill is reduced.

  On the other hand, according to the power conversion device 30 according to the present embodiment, when the setting of the circuit breaker 21 or the like is inappropriate, the setting of the circuit breaker 21 or the like can be corrected in advance by a contractor or the like. Therefore, according to the power converter 30 which concerns on this embodiment, the situation which may arise by the unnecessary operation | movement of the circuit breaker 21 can be prevented.

  As described above, the inrush current is generated under a specific condition such that the grid interconnection switch 34 is turned off or the like in a time zone in which the solar cell 10 stops generating power. Therefore, after several years have passed since the solar cell 10 was installed, the circuit breaker may suddenly operate unnecessarily. Finding out the cause of a circuit breaker that suddenly caused unwanted operation is a difficult task.

  On the other hand, according to the power conversion device 30 according to the present embodiment, it is possible to determine whether or not the setting of the circuit breaker is appropriate before the inrush current is generated, that is, in advance. Therefore, according to the power conversion device 30 according to the present embodiment, it is possible to prevent a situation in which the circuit breaker suddenly performs unnecessary operations after several years have passed since the solar cell 10 was installed.

  Furthermore, in order to reduce the occurrence of unnecessary operation of the circuit breaker, a method of calculating a predicted value of the inrush current and setting the sensitivity current value of the circuit breaker higher than the calculated predicted value of the inrush current is conceivable. In this method, the predicted value of the inrush current is calculated using the value of the ground capacitance of the solar cell.

  However, for example, due to a mistake by a contractor, a different type of solar cell 10 may be installed and connected to the power converter. That is, the solar cell that has obtained the value of the ground capacitance for the calculation of the predicted value of the inrush current may be different from the solar cell 10 that is actually connected to the power converter. In such a case, if the sensitivity current value of the breaker is set based on the predicted value of the inrush power, the sensitivity current value of the breaker will be lower than the actual value of the inrush current, and the breaker may be operated unnecessarily. Can occur. Moreover, even if it is a power converter device which can respond to many types of solar cells, it is difficult to specify beforehand the solar cell connected to a power converter device.

  In contrast, in the power conversion device 30 according to the present embodiment, the predicted value of the inrush current is not calculated using the capacitance value of the ground capacitance C1 of the solar cell 10. The power conversion device 30 according to the present embodiment selects a power generation module suitable for the current situation using known information of a plurality of types of power generation modules, and calculates a predicted value of an inrush current in the solar cell 10. Therefore, according to the power conversion device 30 according to the present embodiment, the actual value of the inrush current increases due to the solar cell 10 of a different type from the schedule being connected to the power conversion device, and the circuit breaker is unnecessary. Can prevent the situation.

  In the first embodiment, the acquisition unit may be an interface that acquires the type of the solar cell 10. Hereinafter, a configuration in which the display unit 37 acquires the format of the solar cell 10 as the acquisition unit will be described as a first modification.

<Modification 1>
The known information according to the modified example 1 includes each combination of the type of each power generation module in the plurality of types of power generation modules and the known value of the inrush current due to the ground capacitance of each power generation module.

  The display unit 37 according to the modified example 1 acquires the format of the solar cell 10 that the user inputs from the display unit 37. When the display unit 37 acquires the format of the solar cell 10, the display unit 37 notifies the control unit 39 of the acquired format of the solar cell 10.

  The control unit 39 calculates a predicted value of the inrush current based on the type of the solar cell 10 and the known information according to the first modification. For example, if the model of the solar cell 10 is “☆☆ 21”, the control unit 39 selects the known value 1.50 [mA] of the inrush current of the power generation module C from the known information. Furthermore, the control unit 39 calculates the predicted value of the inrush current by multiplying the selected known inrush current value 1.50 [mA] by the number of power generation modules included in the solar cell 10.

  In addition, the control part 39 which concerns on the modification 1 does not need to perform the process of above-mentioned step S102-S104.

  In the power conversion device 30 according to the first modification, the predicted value of the inrush current is calculated based on the format of the solar cell 10 acquired by the display unit 37 and the known information of a plurality of types of power generation modules. Furthermore, also in the modification 1, it is determined whether the calculated predicted value of the inrush current is larger than a determination threshold value. As described above, even in the first modification, it is possible to determine whether or not the setting of the circuit breaker 21 is appropriate before the inrush current is generated, that is, in advance. Therefore, even in the power conversion device 30 according to the first modification, the occurrence of unnecessary operation of the circuit breaker 21 can be further reduced. Furthermore, the power conversion device 30 according to the first modification can also prevent a situation that may occur due to an unnecessary operation of the circuit breaker 21.

<Modification 2>
In FIG. 6, schematic structure of the electricity distribution panel 20A which concerns on the modification 2 is shown. 6, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

  In the modification 2, the circuit breaker 21 which is a main power breaker, for example, is provided between the commercial power system 2 and the power conversion device 30 and the load device 3.

  In the modification 2, the control part 39 acquires the sensitivity current value of the circuit breaker 22 provided between the power converter device 30 and the commercial power grid 2 as the minimum sensitivity current value.

  The control unit 39 calculates the predicted value of the inrush current in the same manner as described above, and determines whether or not the calculated predicted value of the inrush current is larger than the determination threshold value. In the modified example 2, the determination threshold value may be a value that is smaller than the sensitivity current value of the circuit breaker 22 by a first predetermined value, for example. In the second modification, the first predetermined value includes, for example, a ground fault current value of another device (for example, the power conversion device 30) provided between the solar cell 10 and the circuit breaker 22. Alternatively, the first predetermined value may be a predetermined ratio (for example, 2/3) of the sensitivity current value of the circuit breaker 22.

  Here, a situation that may occur due to an unnecessary operation of the circuit breaker 22 will be described. If the generated inrush current value is larger than the sensitivity current value of the circuit breaker 22, the circuit breaker 22 will perform an unnecessary operation. That is, the circuit breaker 22 disconnects the commercial power system 2 and the power conversion device 30. When the power conversion device 30 is disconnected from the commercial power system 2, a situation may occur in which the power of the storage battery 11 cannot be supplied to the load device 3. Furthermore, it becomes impossible to charge the storage battery 11 with the electric power from the commercial power system 2 during the night time when the electricity bill is reduced.

  On the other hand, according to the power converter 30 which concerns on the modification 2, when the setting of the circuit breaker 22 etc. are improper, the setting of the circuit breaker 22 etc. may be corrected by the construction contractor etc. in advance. Therefore, according to the power converter 30 which concerns on the modification 2, the situation which may arise by the unnecessary operation | movement of the circuit breaker 22 can be prevented.

(Second Embodiment)
Next, a power conversion system according to the second embodiment of the present disclosure will be described. The power conversion system according to the second embodiment can employ the same configuration as that of the power conversion system 1 according to the first embodiment. Therefore, the following description will focus on differences from the first embodiment with reference to FIGS. 1 and 2.

  In the second embodiment, the control unit 39 performs MPPT (Maximum Power Point Trunking) control on the solar cell 10. For example, the control unit 39 outputs the output of the solar cell string by the DC power transformer 31A so that the operating voltage value of the solar cell string constituting the solar cell 10 follows the voltage value of the maximum power point of the solar cell string. Control the voltage value. In addition, when the solar cell 10 is comprised from a some solar cell string, the direct-current power transformation part may be provided for every solar cell string.

  Also in the second embodiment, the control unit 39 acquires known information as in the first embodiment. Unlike the known information according to the first embodiment, the known information according to the second embodiment differs from the known information according to the first embodiment to a plurality of known locations when each power generation module generates power by a plurality of voltage values within a predetermined range, in other words, MPPT control. Including the leakage current value.

  FIG. 7 shows known information according to the second embodiment of the present disclosure. In the present embodiment, the known plural types of power generation modules are the power generation module A to the power generation module E. In the present embodiment, the plurality of voltage values within the predetermined range are {90 [V], 88 [V], 86 [V]}. The power generation module used in the second embodiment is the power generation module C, and the rated voltage value is 90 [V].

  When the power generation module A generates power at a plurality of voltage values {90 [V], 88 [V], 86 [V]} within a predetermined range, the known ground fault current values are {0.30 [mA], respectively. ], 0.24 [mA], 0.24 [mA]}. In the power generation module A, the known value of the inrush current is 0.70 [mA]. The model of the power generation module A is “ΔΔ01”.

  When the power generation module B generates power at a plurality of voltage values {90 [V], 88 [V], 86 [V]} within a predetermined range, the known ground fault current values are {0.50 [mA], respectively. ], 0.40 [mA], 0.40 [mA]}. In the power generation module B, the known value of the inrush current is 1.20 [mA]. The model of the power generation module B is “ΔΔ02”.

  The known ground fault current values when the power generation module C generates power at a plurality of voltage values {90 [V], 88 [V], 86 [V]} within a predetermined range are {0.70 [mA], respectively. ], 0.56 [mA], 0.55 [mA]}. In the power generation module C, the known value of the inrush current is 1.50 [mA]. The model of the power generation module C is “☆☆ 21”.

  When the power generation module D generates power at a plurality of voltage values {90 [V], 88 [V], 86 [V]} within a predetermined range, the known ground fault current values are {0.10 [mA], respectively. ], 0.08 [mA], 0.08 [mA]}. In the power generation module D, the known value of the inrush current is 0.20 [mA]. The type of the power generation module D is “□□ 30”.

  The known ground fault current values when the power generation module E generates power at a plurality of voltage values {90 [V], 88 [V], 86 [V]} within a predetermined range are {0.13 [mA], respectively. ], 0.10 [mA], 0.09 [mA]}. In the power generation module E, the known value of the inrush current is 0.25 [mA]. The model of the power generation module E is “□□ 60”.

  The predetermined range is set so as to include a voltage value assumed as a voltage value near the maximum operating point of the power generation module, for example. In the present embodiment, the predetermined range is defined with the rated voltage value as an upper limit value and a voltage value that is several percent lower than the rated voltage value as a lower limit value. This is often based on the fact that the voltage value at the maximum operating point of the power generation module is lower than the rated voltage value of the power generation module. Of course, in setting the predetermined range, it is not necessary to set the rated voltage value to the upper limit value. For example, the rated voltage value may be the median value.

  The control unit 39 measures the ground of the solar cell 10 when the solar cell 10 is generating power at a voltage value near the maximum power point in MPPT control (hereinafter also referred to as “maximum operating voltage value”) measured by the acquisition unit 35. Get the current value. Furthermore, the control unit 39 also acquires the maximum operating voltage value of the solar cell 10.

  Based on the ground fault current value of the solar cell 10, the maximum operating voltage value of the solar cell 10, and the known information according to the second embodiment, the control unit 39 generates an inrush current caused by the ground capacitance C1. The predicted value of is calculated. Hereinafter, an example of calculating the predicted value of the inrush current according to the second embodiment will be described.

<Calculation example 2 of predicted value of inrush current>
The control unit 39 calculates the divided current value in the same manner as in <Inrush Current Predicted Value Calculation Example 1>.

  The control unit 39 divides the maximum operating voltage value of the solar cell 10 by the series number of power generation modules constituting the solar cell string to calculate a divided voltage value. The control unit 39 may acquire the serial number of the power generation modules constituting the solar cell string from the storage unit 38 that stores the serial number of the power generation modules in advance. Or the control part 39 may acquire the serial number of the power generation module which comprises a solar cell string from the display part 37, when a contractor inputs the serial number of a power generation module from the display part 37, for example.

  The control unit 39 selects a predetermined voltage value closest to the divided voltage value as a first selection value from a plurality of voltage values in a predetermined range of known information. For example, when the control unit 39 calculates the divided voltage value as 88.4 [V], among the plurality of voltage values {90 [V], 89 [V], 88 [V]} in a predetermined range of known information. Then, the voltage value 88 [V] is selected as the first selection value.

  The control unit 39 determines whether the difference between the divided voltage value and the first selection value is within a voltage threshold value. For example, in the second embodiment, the voltage threshold is set to 0.5 [V] in advance. In such a configuration, the control unit 39 selects the voltage value 88 [V] as the first selection value when calculating the divided voltage value as 88.4 [V]. At this time, the difference between the divided voltage value 88.4 [V] and the first selection value 88 [V] is within the voltage threshold 0.5 [V]. Therefore, the control unit 39 determines that the difference between the divided voltage value and the first selection value is within the voltage threshold.

  When the control unit 39 determines that the difference between the divided voltage value and the first selected value is the voltage threshold value, the control unit 39 selects the divided current value and the highest among the plurality of known ground fault current values corresponding to the first selected value. A close known ground fault current value is selected as the second selection value. As in the above example, the known ground fault current values from the power generation module A to the power generation module E corresponding to the first selection value 88 [V] are {0.24 [mA], 0.40 [mA], 0. .56 [mA], 0.08 [mA], 0.10 [mA]}. Therefore, the control unit 39 has a known ground fault current value 0.56 [mA] of the power generation module C which is the closest value to the divided current value 0.55 [mA] from among the plurality of ground fault current values. Is selected as the second selection value.

  Further, the control unit 39 selects a known value of the inrush current combined with the second selection value from the known information. For example, the control unit 39 selects the known value 1.50 [mA] of the inrush current of the power generation module C combined with the second selection value 0.56 [mA].

  When the control unit 39 selects a known value of the inrush current, the control unit 39 calculates a predicted value of the inrush current in the same manner as in <Inrush Current Predicted Value Calculation Example 1>.

  When the control unit 39 refers to the known information and determines that the difference between the divided voltage value and the first selection value exceeds the voltage threshold, the operating voltage of the solar cell 10 is a voltage value based on the first selection value. You may control so that it may correspond. The voltage value based on the first selection value is calculated, for example, by multiplying the first selection value by the total number obtained by adding the series number and the parallel number of power generation modules constituting the solar cell string. Furthermore, the control unit 39 may measure the ground fault current value of the solar cell 10 by the acquisition unit 35 when the operating voltage of the solar cell 10 matches the first selection value.

[System operation]
Hereinafter, an example of the operation of the power conversion device 30 according to the second embodiment of the present disclosure will be described with reference to FIGS. 8 and 9. The control unit 39 starts the determination process when acquiring a determination process execution request from the display unit 37. Moreover, the control part 39 complete | finishes a determination process, when making the power converter device 30 transfer to a power-off mode after the start of a determination process. Note that the processing in steps S201 to S203 shown in FIG. 8 is the same as the processing in steps S101 to S103 shown in FIG.

  The control unit 39 performs MPPT control on the solar cell 10 (step S204). Thereafter, the control unit 39 acquires the ground fault current value of the solar cell 10 measured by the acquisition unit 35 when the solar cell 10 is generating power at a voltage value near the maximum power point in the MPPT control (step S205). . At this time, the control unit 39 also acquires the maximum operating voltage value of the solar cell 10.

  The control unit 39 divides the maximum operating voltage value of the solar cell 10 by the series number of power generation modules constituting the solar cell string, and calculates a divided voltage value (step S206). The control unit 39 selects a voltage value closest to the divided voltage value from among a plurality of voltage values within a predetermined range of the known information as the first selection value (step S207).

  The control unit 39 determines whether or not the difference between the divided voltage value and the first selection value is within a voltage threshold (step S208). When it is determined that the difference between the divided voltage value and the first selection value is within the voltage threshold (step S207: Yes), the control unit 39 proceeds to the process of step S210 illustrated in FIG. On the other hand, when it is determined that the difference between the divided voltage value and the first selection value exceeds the voltage threshold value (step S207: No), the control unit 39 proceeds to the process of step S209.

  In the process of step S209, the control unit 39 generates the solar cell 10 with the voltage value based on the first selection value, and further acquires the ground fault current value of the solar cell 10 when the power is generated with the voltage.

  The processes in steps S210 to S214 shown in FIG. 8 are the same as the processes in steps S105 to S109 shown in FIG.

  As described above, also in the power conversion device 30 according to the second embodiment, the solar cell 10 calculates the predicted value of the inrush current based on the maximum operating voltage value, the ground fault current value of the solar cell 10, and the known information. To do. Furthermore, also in the second embodiment, it is determined whether or not the calculated predicted value of the inrush current is larger than a determination threshold value. Therefore, also in 2nd Embodiment, generation | occurrence | production of the unnecessary operation | movement of a circuit breaker can be reduced more similarly to 1st Embodiment.

  Furthermore, in the power conversion device 30 according to the second embodiment, the predicted value of the inrush current is calculated using the ground fault current value of the solar cell 10 when the solar cell 10 generates power at a voltage value near the maximum power point. To do. Thereby, in 2nd Embodiment, while performing MPPT control with respect to the solar cell 10, it calculates the predicted value of an inrush current, and determines whether there is a possibility that a circuit breaker will carry out unnecessary operation | movement. Can do. Therefore, in the second embodiment, it is not necessary to interrupt the MPPT control in order to determine whether or not there is a possibility of unnecessary operation of the circuit breaker. Thereby, in this embodiment, it can prevent that the electric power supplied to the load apparatus 3 reduces by interrupting MPPT control. In addition, since the power conversion device 30 according to the second embodiment does not have to interrupt the MPPT control, it is suitable for more regular determination processing.

  Moreover, according to the power converter device 30 which concerns on 2nd Embodiment, if it determines with the difference of a division voltage value and a 1st selection value exceeding a voltage threshold value, the solar cell 10 will be a voltage value based on a 1st selection value. The ground fault current value of the solar cell 10 when the power is generated at is measured. The voltage value based on the first selection value is a voltage value close to the maximum operating voltage value of the solar cell 10. Therefore, the power converter 30 can reduce the difference between the operating voltage value of the solar cell 10 and the maximum operating voltage value of the solar cell 10 when the ground fault current value is measured. Therefore, the power conversion device 30 can perform the determination process while suppressing a decrease in the output power of the solar cell 10.

  Also in the second embodiment, the first and second modifications of the first embodiment can be applied.

(Third embodiment)
In the third embodiment, a method for correcting the predicted value of the inrush current calculated by the method according to the first embodiment or the method according to the second embodiment will be described.

  The control unit 39 according to the third embodiment corrects the predicted value of the inrush current based on the correction coefficient. The correction coefficient is calculated by dividing the division current value calculated by the method according to the first embodiment or the method according to the second embodiment by the known ground fault current value closest to the division current value.

  For example, the control unit 39 calculates the divided current value as 0.65 [mA] by the method according to the first embodiment. At this time, in the known information of the first embodiment shown in FIG. 4, the known ground fault current value closest to the divided current value 0.65 [mA] is the known ground fault current value 0. 7 [mA]. The control unit 39 calculates the correction coefficient as 0.928 (= 0.65 [mA] ÷ 0.7 [mA]). The control unit 39 multiplies the known value 1.50 [mA] of the inrush current of the power generation module C by the number of power generation modules included in the solar cell 10 (assumed to be 32), so that the predicted value of inrush current 48 [ mA] (= 1.50 [mA] × 32 sheets) is calculated. The control unit multiplies the predicted value of inrush current 48 [mA] by a correction coefficient 0.928 to correct the predicted value of inrush current. The predicted value of the inrush current after correction is calculated as 44.54 [mA] (= 48 [mA] × 0.928).

  The ground fault current value and the inrush current value of the solar cell 10 change according to the capacitance value of the ground capacitance C <b> 1 of the solar cell 10. Therefore, if the difference between the divided current value and the known ground fault current value closest to the divided current value is large, it is generated due to the calculated predicted value of the inrush current and the ground capacitance C1. The difference from the actual value of the inrush current can be large.

  In contrast, in the power conversion device 30 according to the third embodiment, the predicted value of the inrush current is corrected by the correction coefficient. Thereby, in 3rd Embodiment, the difference between the estimated value of the calculated inrush current and the actual value of the inrush current generated due to the ground capacitance C1 can be reduced. Therefore, the power conversion device 30 according to the third embodiment can improve the accuracy of the predicted value of the inrush current.

(Fourth embodiment)
In the fourth embodiment, a method for correcting the predicted value of the inrush current calculated by the method according to the first embodiment or the method according to the second embodiment will be described.

  The actual value of the inrush current generated due to the ground capacitance C1 may vary depending on the weather. For example, when it rains and the light receiving surface of the solar cell 10 is wet, the capacitance value of the ground capacitance C1 increases, and the actual value of the inrush current generated due to the ground capacitance C1 increases. For example, when the light receiving surface of the solar cell 10 is sunny and dry, the capacitance value of the ground capacitance C1 becomes small, and the actual value of the inrush current generated due to the ground capacitance C1 becomes small.

  In addition, the ground fault current value of the solar cell 10 may vary depending on the condition of the ground where the power conversion device 30 is installed. For example, when the ground on which the power conversion device 30 is installed is wet, the ground resistance value between the ground capacitance C1 and the ground decreases, and the ground fault current value of the solar cell 10 increases. For example, when the ground to which the power conversion device 30 is grounded is dry, the ground resistance value between the ground capacitance C1 and the ground increases, and the ground fault current value of the solar cell 10 decreases.

  Therefore, in the fourth embodiment, the control unit 39 acquires the weather information of the place where the power conversion device 30 is arranged or the ground information regarding the wetness of the place, and based on the acquired weather information or the ground information, the inrush current is acquired. Correct the predicted value. Hereinafter, this process will be described in <Correction process based on weather information> and <Correction process based on ground information>.

<Correction process based on weather information>
The weather information includes, for example, information on whether or not it rains on the execution date of the determination process. For example, the control unit 39 acquires weather information from a server or the like in a weather prediction period on the network via the communication unit 36.

  When it is determined that it will rain on the execution day of the determination process based on the acquired weather information, the control unit 39 corrects the predicted value of the inrush current by multiplying it by a correction coefficient. The correction coefficient is calculated, for example, by dividing the capacitance value of the ground capacitance C1 when the light receiving surface is dry by the capacitance value of the ground capacitance C1 when the light receiving surface is wet.

<Correction process based on ground information>
The ground information includes, for example, information on whether or not the place where the power conversion device 30 is placed is wet on the execution date of the determination process. For example, the control unit 39 acquires ground information from the contractor via the display unit 37. For example, the control unit 39 displays a request to input ground information on the display unit 37 and presents it to the contractor. The contractor who has seen this display visually checks whether the place where the power conversion device 30 is placed is wet and inputs ground information from the display unit 37.

  When the control unit 39 determines that the place where the power conversion device 30 is placed is wet based on the acquired ground information, the control unit 39 corrects the predicted value of the inrush current by multiplying by a correction coefficient. The correction coefficient is calculated based on, for example, a grounding resistance value when the ground is dry and a grounding resistance value when the ground is wet.

  In general houses and the like, the ground in which the grounding member for grounding the power conversion device 30 is embedded may be separated from the place where the power conversion device 30 is disposed. At this time, the ground information may include information on whether or not the ground in which the grounding member is embedded is wet on the execution date of the determination process.

  As described above, in the fourth embodiment, the predicted value of the inrush current can be accurately calculated by correcting the predicted value of the inrush current based on the correction coefficient. Therefore, according to the fourth embodiment, it is possible to more accurately determine whether or not there is a possibility that the circuit breaker may perform an unnecessary operation.

  Although one embodiment of the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various variations and modifications based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions included in each component, step, etc. can be rearranged so as not to be logically contradictory, and a plurality of components, steps, etc. can be combined or divided into one It is. Also, an embodiment of the present invention has been described centering on the apparatus. However, the present invention can also be realized as a method, a program executed by a processor included in the apparatus, or a storage medium storing the program. Therefore, it should be understood that these are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1,1a Power conversion system 2 Commercial power system 3 Load apparatus 10 Solar cell 11 Storage battery 20 Distribution board 21, 22 Circuit breaker 30, 30a Power conversion device 31A, 31B DC power transformation part 32 Orthogonal conversion part 33 Filter part 34 System connection System switch 35 Acquisition unit 36 Communication unit 37 Display unit 38 Storage unit 39 Control unit

Claims (14)

A power conversion device that converts DC power generated by a solar cell including a plurality of power generation modules into AC power,
An acquisition unit for acquiring a ground fault current value or format of the solar cell;
The minimum sensitivity current value among the sensitivity current values of the circuit breaker provided between the power converter and the commercial power system is acquired, and the known ground fault current value or format of each power generation module in a plurality of types of power generation modules And known information including each combination of the known value of the inrush current due to the ground capacitance of each power generation module, and the solar cell based on the ground fault current value or form of the solar cell and the known information A control unit that calculates a predicted value of the inrush current that is generated due to the ground capacitance and determines whether the calculated predicted value is larger than a determination threshold value based on the minimum sensitivity current value. Power conversion device. The power conversion device according to claim 1,
The said control part is a power converter device which produces | generates a warning signal, when it determines with the said predicted value being larger than the said determination threshold value. The power conversion device according to claim 1 or 2,
The power conversion device, wherein the determination threshold is a predetermined ratio of the minimum sensitivity current value. The power converter according to any one of claims 1 to 3,
The acquisition unit acquires the format of the solar cell,
The known information includes the type of each power generation module in the plurality of types of power generation modules,
The control unit selects the known value combined with the type of the solar cell from the known information, and further multiplies the selected known value by the number of power generation modules included in the solar cell to calculate the predicted value. A power conversion device for calculating The power converter according to any one of claims 1 to 3,
The acquisition unit acquires a ground fault current value of the solar cell when the solar cell is generating power at a rated voltage value,
The known information includes a plurality of ground fault current values based on a rated voltage value of each power generation module in the plurality of types of power generation modules. In the power converter device according to any one of claims 1 to 3 and 5,
The known ground fault current value is a value per one of the plurality of types of power generation modules,
The control unit subtracts the ground fault current value of the power conversion device from the ground fault current value of the solar cell, further calculates the division current value by dividing by the number of power generation modules included in the solar cell,
The control unit selects the known value combined with the known ground fault current value closest to the divided current value from the known information, and further adds the number of the power generation modules to the selected known value. A power converter that multiplies and calculates the predicted value. The power converter according to any one of claims 1 to 3,
The control unit performs MPPT control on the solar cell,
The acquisition unit measures a ground fault current value of the solar cell when the solar cell is generating power at a voltage value near the maximum operating point in MPPT control,
The known ground fault current value includes a plurality of known ground fault current values based on a plurality of voltage values within a predetermined range of each power generation module in the plurality of types of power generation modules. The power conversion device according to claim 7,
The control unit calculates a divided voltage value by dividing a voltage value near the maximum operating point by a series number of power generation modules constituting the solar string constituting the solar cell, and a plurality of voltage values within the predetermined range. When the difference between the divided voltage value and the first selected value exceeds the voltage threshold, the solar cell is selected as the first selected value. The power converter which measures the ground-fault current value of the said solar cell when generating with the voltage value based on a selection value. The power conversion device according to claim 7,
The known ground fault current value is a value per one of the plurality of types of power generation modules,
The control unit subtracts the ground fault current value of the power conversion device from the ground fault current value of the solar cell, further calculates the division current value by dividing by the number of power generation modules included in the solar cell,
The control unit calculates a divided voltage value by dividing a voltage value near the maximum operating point by a series number of power generation modules forming a solar string included in the solar cell, and calculates the divided voltage value within the predetermined range from the known information. When the voltage value closest to the divided voltage value is selected as the first selected value from the plurality of voltage values, and it is determined that the difference between the divided voltage value and the first selected value is within the voltage threshold value, A known ground fault current value closest to the divided current value is selected as a second selected value from a plurality of known ground fault current values corresponding to the first selected value, and is combined with the second selected value. A power conversion device that selects the known value. The power conversion device according to claim 6 or 9,
The control unit multiplies the selected known value by the number of the power generation modules, and further adds a ground fault current value of the power conversion device to calculate the predicted value. The power conversion device according to claim 6 or 9,
The circuit breaker having the minimum sensitivity current value is provided between the commercial power system and a load device to which the power converter supplies power,
The control unit calculates the predicted value by multiplying the selected known value by the number of the power generation modules and then adding the ground fault current value of the power converter and the leakage current value of the load device. A power converter. The power conversion device according to any one of claims 6 and 9 to 11,
The said control part is a power converter device which correct | amends the said estimated value based on the correction coefficient calculated by dividing the said division current value by the said known ground fault current value of the value nearest to the said division current value. The power conversion device according to any one of claims 6 and 9 to 11,
The said control part is a power converter device which acquires the information of at least one of the weather information and the ground information of the place where the said power converter device is arrange | positioned, and correct | amends the said predicted value based on this acquired information. A method for controlling a power converter that converts DC power generated by a solar cell including a plurality of power generation modules into AC power,
Obtaining a ground fault current value or format of the solar cell;
Obtaining a minimum sensitivity current value among the sensitivity current values of a circuit breaker provided between the power converter and the commercial power system;
Obtaining known information including each combination of a known ground fault current value or type of each power generation module in a plurality of types of power generation modules and a known value of inrush current due to the ground capacitance of each power generation module;
Calculating a predicted value of inrush current generated due to the ground capacitance of the solar cell based on the ground fault current value or type of the solar cell and the known information;
Determining whether or not the predicted value is greater than a determination threshold value based on the minimum sensitivity current value.

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