JP6388528B2 - Ground fault detection device - Google Patents

Description

  The present invention relates to a ground fault detection device that detects a ground fault generated in a solar power generation system.

  Conventionally, as described in Patent Document 1 described below, a photovoltaic power generation system is operated by switching between a grid operation and a self-sustained operation. In addition, some solar power generation systems include a ground fault detection circuit that detects a ground fault of a solar cell at the time of interconnection operation, as described in Patent Document 2 below. When a ground fault is detected by the ground fault detection circuit, the solar power generation system can be operated safely by stopping the operation.

JP 2010-259170 A JP-A-9-182449

  However, according to the above-described conventional technique, there is a problem that the ground fault can be detected during the interconnection operation and the ground fault cannot be detected during the independent operation.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the ground fault detection apparatus which can detect a ground fault at the time of independent operation.

In order to solve the above-described problems and achieve the object, the present invention provides a ground fault in the solar power generation system based on a detection result in a current detection unit that detects a ground fault current in the solar power generation system. A ground fault detection circuit that determines presence / absence; and a control unit that performs control to change a ground fault determination criterion in the ground fault detection circuit during the interconnection operation and the independent operation . The ground fault detection circuit is characterized in that the detection sensitivity when determining the ground fault with respect to the ground fault current is set higher in the independent operation than in the grid operation .

  According to the present invention, there is an effect that a ground fault can be detected during independent operation.

The figure which shows the structural example of a solar energy power generation system provided with the ground fault detection apparatus concerning Embodiment 1. FIG. The figure which shows the state of a solar power generation system when a ground fault generate | occur | produces at the time of interconnection operation in Embodiment 1. The figure which shows the ground fault electric current detected with the zero phase current transformer when the ground fault generate | occur | produces at the time of interconnection operation in Embodiment 1. The figure which shows the state of the solar energy power generation system when a ground fault generate | occur | produces at the time of self-sustained operation in Embodiment 1. The figure which shows the ground-fault current detected with the zero phase current transformer when the ground fault generate | occur | produces at the time of self-sustained operation in Embodiment 1.

  Below, the ground fault detection apparatus concerning embodiment of this invention is demonstrated in detail based on drawing. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a solar power generation system 100 including a ground fault detection device according to the first embodiment of the present invention.

  The solar power generation system 100 includes a solar cell 1 that performs solar power generation and outputs DC power, a connection box 2 that connects the solar cell 1 and the power conditioner 8, and a ground fault generated in the solar power generation system 100. The voltage is boosted by a zero-phase current transformer (ZCT) 3 that is a current detection unit that detects a ground-fault current due to the solar cell, a converter 4 that boosts the voltage of DC power from the solar cell 1, and the converter 4. The inverter 5 for converting the DC power into AC power, the interconnection relay 6 for turning on / off the connection between the power conditioner 8 and the AC system 9, and the connection between the power conditioner 8 and the self-supporting load 10 AC power that can be supplied to AC power from the power conditioner 8, and can be supplied with AC power from the independent relay 7 that turns on and off and the power conditioner 8. Provided with integrated 9, and independence load 10 that operates by being supplied with AC power from the power conditioner 8, and a control circuit 11 for controlling the operation of the power conditioner 8.

  In the photovoltaic power generation system 100 shown in FIG. 1, a power conditioner 8 is configured by the zero-phase current transformer 3, the converter 4, the inverter 5, the interconnection relay 6, and the self-supporting relay 7. In FIG. 1, the interconnection relay 6 and the self-supporting relay 7 are both turned off. However, during the interconnection operation, the interconnection relay 6 is turned on and the self-contained relay 7 is turned off. The system relay 6 is off and the self-supporting relay 7 is on. In addition, about the zero phase current transformer 3, if the fluctuation | variation of the ground fault current by the ground fault which generate | occur | produced in the solar power generation system 100 can be detected, you may use another structure. In FIG. 1, the neutral line between the AC system 9 and the power conditioner 8 is assumed to be grounded at the ground point A.

  A control circuit 11 including a ground fault detection device includes a ground fault detection circuit 12 that determines the presence or absence of a ground fault in the photovoltaic power generation system 100 based on the ground fault current detected by the zero-phase current transformer 3, and a power condition. The control unit 13 that controls the operation of the controller 8 and controls the ground fault detection circuit 12 to change the ground fault determination criteria, and the display that displays the operation state of the photovoltaic power generation system 100, the occurrence of the ground fault, and the like. Unit 14 and a switch 15 that is a selection unit that accepts selection of a grid connection operation or a self-sustained operation by the user for the operation mode of the photovoltaic power generation system 100.

  Specifically, the control unit 13 controls the operation of the power conditioner 8 by controlling the operation of the converter 4, the inverter 5, the interconnection relay 6, and the self-supporting relay 7. Further, the control unit 13 performs control to change the ground fault determination criterion in the ground fault detection circuit 12 during the grid operation and the self-sustaining operation based on the operation mode selected by the switch 15.

  It continues and the operation | movement which detects the ground fault which generate | occur | produces in the solar power generation system 100 in a ground fault detection apparatus is demonstrated.

  First, a case where a ground fault occurs during the interconnected operation will be described. When the operation mode of the photovoltaic power generation system 100 is the interconnection operation, first, the user selects the interconnection operation with the switch 15. The control unit 13 receives a notification that the interconnection operation is selected from the switch 15 and controls the power conditioner 8 to operate in the interconnection operation.

  FIG. 2 is a diagram illustrating a state of the photovoltaic power generation system 100 when a ground fault occurs during the interconnected operation in the first embodiment. In FIG. 2, the difference from FIG. 1 is that the interconnection relay 6 is on, and the description of the self-supporting load 10 is omitted because it is unnecessary during the interconnection operation. Moreover, the state in which the ground fault has generate | occur | produced between the solar cell 1 and the junction box 2 is shown. A ground fault point between the solar cell 1 and the junction box 2 is defined as a ground fault point B.

  FIG. 3 is a diagram showing a ground fault current Ir detected by the zero-phase current transformer 3 when a ground fault occurs during the grid operation in the first embodiment.

  As shown in FIG. 2, when a ground fault occurs between the solar cell 1 and the junction box 2, the ground fault point B → the ground point A → the AC system 9 → the interconnection relay 6 → the inverter 5 → the converter 4 → zero. A current loop of phase current transformer 3 → junction box 2 → ground fault B is generated. With this current loop, the ground fault current Ir shown in FIG. 3 is detected in the zero-phase current transformer 3.

  Information on the ground fault current Ir shown in FIG. 3 detected by the zero phase current transformer 3 is input from the zero phase current transformer 3 to the ground fault detection circuit 12. Under the control of the control unit 13, the ground fault detection circuit 12 sets the detection sensitivity of the ground fault current Ir to be lower during the interconnected operation than during the independent operation. The detection sensitivity is the smallest change amount of current that can be detected in the measurement. The ground fault detection circuit 12 can detect a current change exceeding the set detection sensitivity. Here, as an example, the detection sensitivity of the ground fault current Ir during the interconnection operation is set in the range of 30 mA to 100 mA.

  The ground fault detection circuit 12 determines whether or not a ground fault has occurred in the photovoltaic power generation system 100 with the detection sensitivity set by the control from the control unit 13. When it is determined that a ground fault has occurred in the solar power generation system 100, the ground fault detection circuit 12 notifies the control unit 13 of the occurrence of a ground fault. Then, when notified of the occurrence of the ground fault from the ground fault detection circuit 12, the control unit 13 performs control to turn off the interconnection relay 6 and stop the operation of the power conditioner 8.

  Next, a case where a ground fault occurs during the independent operation will be described. When the operation mode of the solar power generation system 100 is the independent operation, the user first selects the independent operation with the switch 15. The control unit 13 receives a notification that the autonomous operation has been selected from the switch 15 and controls the power conditioner 8 to operate in the autonomous operation.

  FIG. 4 is a diagram illustrating a state of the photovoltaic power generation system 100 when a ground fault occurs during the independent operation in the first embodiment. In FIG. 4, the difference from FIG. 1 is that the self-supporting relay 7 is turned on. In addition, a ground fault is generated between the solar cell 1 and the junction box 2, and further, a ground fault is generated in the self-supporting load 10 outside the power conditioner 8. A ground fault point between the solar cell 1 and the junction box 2 is defined as a ground fault point B. The ground fault location of the self-supporting load 10 is defined as a ground fault point C. Here, although the case where a ground fault is caused by the self-supporting load 10 will be described, the ground fault location may be a wiring portion between the self-supporting load 10 and the power conditioner 8.

  FIG. 5 is a diagram showing the ground fault current Ir detected by the zero-phase current transformer 3 when a ground fault occurs during the self-sustaining operation in the first embodiment. In FIG. 5, IrDC represents a direct current component of the ground fault current Ir, and IrAC represents an alternating current component of the ground fault current Ir.

  As shown in FIG. 4, when a ground fault occurs between the solar cell 1 and the junction box 2, and further a ground fault occurs on the side of the self-supporting load 10, the ground fault point B → the ground fault point C → the self-supporting state. A current loop of load 10 → self-supporting relay 7 → inverter 5 → converter 4 → zero phase current transformer 3 → junction box 2 → ground fault B is generated. By this current loop, the ground fault current Ir shown in FIG. 5 is detected in the zero-phase current transformer 3.

  Information on the ground fault current Ir shown in FIG. 5 detected by the zero phase current transformer 3 is input from the zero phase current transformer 3 to the ground fault detection circuit 12. Under the control of the control unit 13, the ground fault detection circuit 12 sets the detection sensitivity of the ground fault current Ir higher during the independent operation than during the grid operation. Here, as an example, the detection sensitivity of the ground fault current Ir during the independent operation is set to be less than 30 mA.

  The ground fault detection circuit 12 determines whether or not a ground fault has occurred in the photovoltaic power generation system 100 with the detection sensitivity set by the control from the control unit 13. When it is determined that a ground fault has occurred in the solar power generation system 100, the ground fault detection circuit 12 notifies the control unit 13 of the occurrence of a ground fault. Then, when notified of the occurrence of the ground fault from the ground fault detection circuit 12, the control unit 13 performs control to turn off the self-supporting relay 7 and stop the operation of the power conditioner 8.

  The control unit 13 performs control to change the ground fault determination standard in the ground fault detection circuit 12, that is, the detection sensitivity of the ground fault current Ir in the grid operation and the independent operation. When a ground fault is detected during the self-sustaining operation, as shown in FIG. 5, a ground fault current Ir including a direct current component IrDC and an alternating current component IrAC flows. In general, the AC component IrAC has a greater effect on the human body than the DC component IrDC. Therefore, if the detection sensitivity during the independent operation is set to be low as in the case of the interconnection operation, the human body is not sufficiently protected. . On the other hand, if the detection sensitivity is set to be high in the interconnected operation as in the independent operation, there is a risk of erroneous detection during the interconnected operation due to the influence of voltage fluctuation such as an instantaneous power failure on the AC system 9 side.

  For this reason, the control unit 13 sets the detection sensitivity within the range of 30 mA to 100 mA during the interconnected operation and sets the detection sensitivity to less than 30 mA during the independent operation with respect to the determination criterion of the ground fault current Ir in the ground fault detection circuit 12. Set it so that the detection sensitivity during autonomous operation is higher than the detection sensitivity during interconnected operation. In the ground fault detection circuit 12, for example, when the ground fault current Ir is 50 mA, it is determined that there is no ground fault when the detection sensitivity during the interconnection operation is 100 mA, and there is a ground fault during the independent operation. Is determined. As a result, the control unit 13 can determine a ground fault even during a self-sustained operation even if the current is smaller than the detection sensitivity during the interconnected operation.

  As described above, according to the present embodiment, the control unit 13 uses the ground fault detection circuit 12 for the ground fault current Ir generated in the photovoltaic power generation system 100 during the independent operation and the interconnection operation. Change the ground fault criteria. Specifically, when the control unit 13 selects the independent operation from the user with the switch 15, the control unit 13 sets the detection sensitivity of the ground fault current Ir at the time of the independent operation to the ground fault detection circuit 12 more than at the time of the connected operation. We decided to set it high. Thereby, even when a ground fault occurs during the independent operation of the photovoltaic power generation system 100 and a ground fault current Ir including the direct current component IrDC and the alternating current component IrAC is generated, the ground fault detection circuit 12 appropriately determines the ground fault. And can protect the photovoltaic power generation system 100 and the user.

  In the present embodiment, the range of detection sensitivity at the time of interconnected operation is overlapped with the range of detection sensitivity at the time of independent operation, but this is an example, and the present invention is not limited to this. .

  Moreover, in this Embodiment, although the control part 13 received the information of the operation mode which the user selected from the switch 15, and set the detection sensitivity of the ground fault detection circuit 12, it is not limited to this. The switch 15 notifies the information on the operation mode selected by the user to the ground fault detection circuit 12 together with the control unit 13, and the ground fault detection circuit 12 receives the information on the operation mode selected by the user directly from the switch 15 and detects the detection sensitivity. May be set.

Embodiment 2. FIG.
In the first embodiment, the ground fault determination standard at the time of the grid operation and the independent operation is changed, and the detection sensitivity of the ground fault current Ir at the independent operation is increased. In the second embodiment, a method of using the detection ground fault current Irs in which the AC component IrAC is weighted more than the DC component IrDC in the determination of the ground fault during the independent operation will be described.

  The ground fault detection circuit 12 makes the detection sensitivity constant during the interconnection operation and the independent operation, and separates the detected ground fault current Ir into the AC component IrAC and the DC component IrDC during the independent operation. The ground fault detection circuit 12 calculates the following equation (1) using the average value of the direct current component IrDC and the value obtained by multiplying the effective value of the alternating current component IrAC by the coefficient K after obtaining the effective value of the alternating current component IrAC. To calculate the detection ground fault current Irs. In the ground fault detection circuit 12, as an example, when K = 1.67, the detection ground fault current Irs is, for example, 30 mA × 1.67≈50 mA which is the determination value in the self-sustaining operation used in the first embodiment. When it becomes above, it determines with the earth fault having generate | occur | produced.

    Irs = average value of IrDC + effective value of IrAC × K (1)

  When it is determined that a ground fault has occurred in the solar power generation system 100, the ground fault detection circuit 12 notifies the control unit 13 of the occurrence of a ground fault, as in the first embodiment. Then, when notified of the occurrence of the ground fault from the ground fault detection circuit 12, the control unit 13 performs control to turn off the self-supporting relay 7 and stop the operation of the power conditioner 8.

As described above, according to the present embodiment, the ground fault detection circuit 12 separates the detected ground fault current Ir into the alternating current component IrAC and the direct current component IrDC when the photovoltaic power generation system 100 is operating independently. The determination of the ground fault is performed using the average value obtained from the direct current component IrDC and the value obtained by weighting the effective value obtained from the alternating current component IrAC. Thereby, the ground fault detection circuit 12 makes it easier to determine the ground fault during the self-sustained operation than in the case where the effective value obtained from the AC component IrAC is not weighted. The photovoltaic system 100 and the user can be appropriately protected.
In the first and second embodiments described above, the selection of the interconnection operation or the independent operation is described as being performed by the switch 15 that is the selection unit. However, this selection is performed by the control unit 13 in which the AC system 9 is energized, for example. The same effect can be obtained even if the operation is performed by selecting the independent operation when the AC system 9 is out of power when the AC system 9 is out of power.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  DESCRIPTION OF SYMBOLS 1 Solar cell, 2 Junction box, 3 Zero phase current transformer, 4 Converter, 5 Inverter, 6 interconnection relay, 7 Autonomous relay, 8 Power conditioner, 9 AC system, 10 Autonomous load, 11 Control circuit, 12 Ground fault Detection circuit, 13 control unit, 14 display unit, 15 switch, 100 solar power generation system.

Claims (4)

Based on the detection result in the current detection unit that detects the ground fault current of the solar power generation system, a ground fault detection circuit that determines the presence or absence of the ground fault in the solar power generation system,
A control unit that performs control to change a ground fault determination criterion in the ground fault detection circuit at the time of interconnected operation and autonomous operation;
Equipped with a,
The ground fault detection circuit sets the detection sensitivity at the time of determining the ground fault with respect to the ground fault current higher than that at the time of the interconnection operation in the independent operation.
A ground fault detection device characterized by that. Based on the detection result in the current detection unit that detects the ground fault current of the solar power generation system, a ground fault detection circuit that determines the presence or absence of the ground fault in the solar power generation system,
During self-sustained operation, the ground fault current is separated into an AC component and a DC component, and a ground fault is determined using a value obtained by weighting the effective value obtained from the AC component and an average value obtained from the DC component. A control unit;
A ground fault detection device comprising: The system further comprises a selection unit that accepts selection of the grid-operated operation or the independent operation by the user for the operation mode of the solar power generation system,
The ground fault detection device according to claim 1 or 2 , wherein the control unit switches the operation mode of the photovoltaic power generation system to the interconnection operation or the self-sustained operation based on a notification from the selection unit. The control unit switches the operation mode of the photovoltaic power generation system to the interconnected operation when the AC system is energized, and switches the operation mode of the photovoltaic power generation system to the independent operation when the AC system is out of power. Item 3. The ground fault detection device according to Item 1 or 2 .

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