JP2015046963A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter capable of ensuring safety easily, when switching the AC powers for system interconnection and system independence of output voltages different from each other.SOLUTION: A power converter includes a system interconnection relay 5 outputting an AC power for system interconnection of an inverter circuit 2 by relay on during system interconnection mode, and an independence relay 7 connected in parallel with the system interconnection relay 5, and outputting an AC power for independence of an output voltage different from the system interconnection of the inverter circuit 2 by relay on during independent mode. A protection switch circuit 8 operates to interrupt connection of the system interconnection relay 5 and the independence relay 7, even if the independence relay 7 is operated erroneously relay on, when the system interconnection relay 5 is relay on and the independence relay 7 is relay off.

Description

  The present invention relates to a power conversion device that converts DC power output from a solar cell into AC power.

  2. Description of the Related Art Conventionally, there is known a solar system that converts DC power output from a DC power source such as a solar cell into commercial AC power by using a power converter including an inverter circuit and outputs the AC power. As an example of this, a solar cell array including a plurality of solar cell panels, and a small-capacity inverter circuit (power conversion device) that converts the output of the solar cell array from direct current to alternating current and supplies it to a power cable for system interconnection A solar power generation device including a plurality of solar cell array units each including an inverter unit is included (for example, Patent Document 1).

  By the way, there is also known a power conversion device that outputs AC power for grid interconnection by switching by a switching (control) element and outputs independent AC power independent from this during a power failure or the like (for example, Patent Document 2).

  FIG. 3 is a block diagram showing a conventional power converter. An inverter circuit 52 that converts DC power of a solar cell such as a solar panel S into AC power, a grid connection mode that controls conversion to AC power for grid connection, and an alternating current for independent output voltage. A mode switching unit 54 for switching to a self-sustaining mode for controlling conversion to electric power, a grid interconnection relay 55 for outputting AC power for grid interconnection of the inverter circuit when the relay is on, and grid interconnection in the grid interconnection mode A self-supporting relay 57 that is connected in parallel with the relay and outputs AC power for self-support of the inverter circuit 52 when the relay is on is provided in the self-support mode.

JP 2010-279234 A JP 2010-259170 A

  However, if the output voltage for grid connection is, for example, 200 VAC and the output voltage for stand-alone is 100 VAC, the grid-connected relay is relay-on, the stand-alone relay is relay-off, and an AC100V standard electrical device is connected to the stand-alone outlet. When the self-sustained relay is turned on due to a failure of an internal component such as a transistor that drives the self-supporting relay, the AC200V voltage is supplied to the AC100V electrical equipment. There was a problem that it could lead to an unexpected accident.

  In particular, when power outages occur frequently due to earthquakes, etc., it is assumed that there will be more cases of forgetting that AC 100V electrical equipment remains connected to an independent outlet because of the increased use of AC power for autonomous use. Therefore, it is necessary to take safety measures against this.

  The present invention has an inverter circuit that converts the DC power of a solar cell into AC power, and easily secures safety when switching between grid output and independent AC power of different output voltages It aims at providing the power converter which can be performed.

  In order to achieve the above object, a power conversion device according to the present invention includes an inverter circuit that converts DC power of a solar cell into AC power, a grid connection mode that performs conversion control to AC power for grid connection, and A mode switching unit that switches to a stand-alone mode that controls conversion of output voltage to a stand-alone AC power that is different from the above, and a grid connection that outputs AC power for grid connection of the inverter circuit when the relay is on in the grid connection mode. And a self-supporting relay that is connected in parallel to the system relay and the grid-connected relay and outputs AC power for self-supporting of the inverter circuit when the relay is on in the self-supporting mode. When the grid connection relay is relay-on and the self-sustained relay is relay-off, a protective switch circuit is provided that operates to shut off the connection between the self-sustained relay and the grid-connected relay even if the self-sustained relay malfunctions when the relay is on. Yes.

  According to this configuration, when the grid interconnection relay is relay-on and the independent relay is relay-off, the connection between the grid-connected relay and the autonomous relay is always cut off even if the independent relay malfunctions when the relay is on. Therefore, for example, even if an internal component failure occurs and AC power of the grid connection relay is output from the self-supporting relay, this can be prevented by interrupting the relay. As a result, when switching between grid power and independent AC power with different output voltages, it is easy to ensure safety even when the electrical equipment of the independent voltage standard is still installed in the independent outlet. Securement is possible.

  Preferably, the grid interconnection relay is connected to commercial AC power of the inverter circuit based on the first control element being turned on, and the self-supporting relay is connected to the inverter circuit based on the second control element being turned on. The protective switch circuit is a third control element connected in series between the self-supporting relay and the second control element, and the first control element is turned on. In this case, the self-supporting relay and the second control element are always cut off. In this case, safety can be secured with a simple configuration even if the second control element that drives the self-supporting relay fails.

  Preferably, the inverter circuit is connected in parallel to a plurality of solar cells. Therefore, desired power can be obtained from a plurality of solar cells.

  In the present invention, when the grid connection relay is relay-on and the self-sustained relay is relay-off, even if the self-sustained relay malfunctions when the relay is on, the connection between the self-sustained relay and the grid-connected relay is always cut off. Safety can be easily ensured when switching between AC power for grid connection and independent AC power.

It is a block diagram which shows the power converter device which concerns on one Embodiment of this invention. It is a circuit diagram which shows a part of power converter device of FIG. It is a block diagram which shows the conventional power converter device.

  FIG. 1 is a block diagram showing a power converter 1 according to an embodiment of the present invention. The inverter circuit 2 which converts, for example, 2 kW DC power of the solar cell S made of a solar panel into AC power is included. A solar system that outputs electric power of a desired voltage can be configured by connecting a plurality of the power converters 1 and a plurality of solar cells S in parallel and collecting a plurality of facilities respectively wired to a current collection box.

  A power conversion device 1 in FIG. 1 includes an inverter circuit 2 that performs power conversion by a switching operation of a control element (not shown) such as a transistor, an inverter circuit 2, and a control unit 3 that controls the entire device. The control unit 3 switches between a grid connection mode that is a control mode of the inverter circuit 2 that is converted into AC power for grid connection and a self-sustained mode that is converted into AC power for independent use with a different output voltage. A mode switching unit 4 is provided. For example, the output voltage of AC power for grid connection is AC200V, and the output voltage of AC power for stand-alone is AC100V.

  The power conversion device 1 is connected in parallel with the grid interconnection relay 5 and the grid interconnection relay 5 that output AC power for grid interconnection of the inverter circuit 2 when the relay is turned on in the grid interconnection mode. And a self-supporting relay 7 that outputs AC power for self-support of the inverter circuit 2 when the relay is on.

  Protective switch that operates to cut off the connection between the grid interconnection relay 5 and the self-sustained relay 7 even if the self-reliant relay 7 malfunctions when the relay is on when the grid interconnection relay 5 is relay-on and the self-sustained relay 7 is relay-off A circuit 8 is provided.

  FIG. 2 is a circuit diagram showing a part of the power conversion apparatus of FIG. The grid interconnection relay 5 is connected to the grid interconnection AC power of the inverter circuit 2 based on the first control element T1 and the fourth control element T4 being turned on, and the self-sustaining relay 7 is connected to the second control element. Based on the ON state of the element T2, the inverter circuit 2 is connected to the AC power for self-supporting. The protection switch circuit 8 is a third control element T3 connected in series between the self-supporting relay 7 and the second control element T2, and when the first control element T1 is on, Is always disconnected from the control element T2. In this case, safety can be ensured with a simple configuration.

  When the grid connection relay switches 11 and 12 are turned on, the first control element T1 and the fourth control element T4 are turned on via the photocoupler PC, the grid connection relay 5 is turned on, and the AC 200V grid connection is established. AC power is output.

  When the self-supporting relay switch 13 is turned on, the second control element T2 is turned on via the photocoupler PC, and the self-supporting relay 7 is turned on. When the first control element T1 is turned on by the third control element T3 connected in series between the self-supporting relay 7 and the second control element T2 in the protection switch circuit 8, the cut-off state is based on this on signal. Thus, the independent relay 7 and the second control element T2 are always disconnected.

  In the above configuration, when the grid connection relay 5 is relay-on and the self-sustained relay 7 is relay-off, even if the self-sustained relay 7 malfunctions to relay-on, the third control element T3 is independent from the self-sustained relay 7 and the second control element T2. And the connection between the grid interconnection relay 5 and the self-supporting relay 7 is cut off. Therefore, unlike the conventional case, when the grid connection relay 5 is relay-on, the output voltage of AC 200 V for grid connection is not output from the self-sustaining relay 7, so that the AV100V standard electrical device is connected to the outlet of the self-sustaining relay 7. Even if it remains connected, AC200V is not applied, and there is no possibility of deteriorating and burning electrical equipment or causing unexpected accidents to the human body.

  Thus, in the present invention, when the grid connection relay is relay-on and the self-sustained relay is relay-off, the connection between the grid-connected relay and the self-supporting relay is always cut off even if the self-supporting relay malfunctions when the relay is on. Therefore, for example, even if an internal component failure occurs and AC power of the grid connection relay is output from the self-supporting relay, this can be prevented by interrupting the relay. As a result, when switching between grid power and independent AC power with different output voltages, it is easy to ensure safety even when the electrical equipment of the independent voltage standard is still installed in the independent outlet. Securement is possible.

  Note that the protection switch circuit 8 turns off the third control element T3 based on the ON signal of the fourth control element T4 instead of the first control element T1, and sets the self-supporting relay 7 and the second control element. You may make it interrupt | block between T2.

1: Power conversion device 2: Inverter circuit 3: Control unit 4: Mode switching unit 5: Grid interconnection relay 7: Stand-alone relay 8: Protection switch circuit T1: First control element T2: Second control element T3: Second Third control element T4: Fourth control element S: Solar cell

Claims (3)

An inverter circuit that converts the DC power of the solar cell into AC power;
A mode switching unit that switches between a grid interconnection mode that performs conversion control to AC power for grid interconnection and a self-sustained mode that performs conversion control to AC power for independent output voltage different from this,
Connected in parallel with the grid interconnection relay that outputs AC power for grid interconnection of the inverter circuit when the relay is turned on in the grid interconnection mode, and connected to the grid interconnection relay in the autonomous mode. Equipped with a self-supporting relay that outputs AC power,
When the grid connection relay is relay-on and the self-sustained relay is relay-off, a protective switch circuit is provided that operates to disconnect the grid-connected relay and the self-sustained relay even if the self-sustained relay malfunctions when the relay is on. The power converter. In claim 1,
The grid interconnection relay is connected to AC power for grid interconnection of the inverter circuit based on turning on of the first control element, and the self-supporting relay is connected to the inverter circuit based on turning on of the second control element. Connected to independent AC power
The protection switch circuit is a third control element connected in series between the self-supporting relay and the second control element. When the first control element is on, the protection switch circuit is connected to the self-supporting relay and the second control element. A power converter that always cuts the gap. In claim 1 or 2,
A power conversion device in which the inverter circuit is connected in parallel to a plurality of solar cells.

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