JPH09215205A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conversion apparatus in which a current to be consumed by a parallel-off switch is eliminated in a steady sate, which enhances the efficiency of a photovoltaic power generation system and whose efficiency is high. SOLUTION: An apparatus 4 which supplies electric power to a load 6 in linkage with a commercial power supply system 7 is constituted of a power conversion part 4a in which electric power to be input from a DC power supply 1 is converted into an alternating current so as to be output, of an AC voltage detection circuit 4c which detects the output voltage of the power conversion part 4a, of a parallel-off switch 5 which parallels off linkage with the commercial power supply system 7 and of a switching drive circuit 4e which operates the parallel-off switch 5. In this case, when the parallel-off switch 5 is formed as a switching structure having a self-hold function, a switching part 5a of the parallel-off switch 5 maintains a linkage state even when an exciting current is not available continuously as long as a system voltage and an inverter output voltage are normal, and a parallel-off state is released when the voltages are abnormal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter, and more particularly to a power converter for converting a direct current power source such as a solar cell into an alternating current and connecting it to a commercial power source system to supply power to a load.

[0002]

2. Description of the Related Art Conventionally, a DC power source such as a solar cell is converted into an AC power source, and is connected to a commercial power source system to supply power to a load.
An example of a grid interconnection inverter device as a power conversion device is shown in FIG. 3, which is disclosed in JP-A-1-107661. FIG. 3 is a basic configuration diagram of the solar power generation system. This solar power generation system is a solar cell 1
A diode 2, a capacitor 3, an inverter circuit unit 4, and an opening / closing unit 5. Then, the power is supplied to the load 6 in cooperation with the commercial power supply system 7.

The solar cell 1 is a direct current power source for converting electric power. The diode 2 prevents a current from flowing backward from the inverter circuit section 4 which is a power conversion section, and has an anode terminal on the positive side of the solar cell 1 and a cathode terminal on the positive side input end of the inverter circuit section 4. The connected capacitor 3 is an electrolytic capacitor that smoothes the output voltage of the solar cell 1. The positive electrode terminal is connected to the positive input terminal of the inverter circuit unit 4, and the negative terminal is connected to the negative input terminal of the inverter circuit unit 4. To be done. The inverter circuit unit 4 is a power conversion unit that converts the DC power supply of the solar cell 1 into AC and outputs the AC power. The inverter circuit section 4 inputs the DC output of the solar cell 1 through both ends of the positive electrode terminal and the negative electrode terminal of the capacitor 3, Converted to and output. The inverter circuit unit 4 generally includes a switch element (not shown) that is bridge-connected to form an inverter bridge, a low-pass filter that is connected to an output end of the bridge connection, and a PWM control unit that controls the switch element. Configured. The switch 5 is a switch of an AC contactor device, which is a switch driven by an AC power source, for example, and a switch for such an application is generally called a disconnecting switch. The opening / closing unit 5 has one end connected to one end of the output of the inverter circuit unit 4 and the other end connected to one end of the load 6. Further, the inverter circuit unit 4 has a voltage detection unit (not shown) that detects the output voltage of the inverter circuit unit 4 and an opening / closing operation unit that operates the opening / closing unit 5 by the output signal of the voltage detection unit. It has a function to open and close. The load 6 is an AC load, and is connected to the commercial power supply system 7 and the output of the inverter circuit unit 4 via the switching unit 5. Then, in the above solar power generation system, the inverter circuit unit 4 supplies power to the load 6 at the same time as the commercial power supply system 7. This connected state is called interconnection.

In the above photovoltaic power generation system, when the output of the solar cell 1 is converted to a normal voltage value by the inverter circuit section 4 and the commercial power supply system 7 is in the power supply state, the closing circuit 5 is closed. The state is continued and the interconnection is maintained. In addition, when an abnormal voltage value (meaning voltage increase, voltage decrease, frequency increase, and frequency decrease) is detected by the voltage detection unit of the inverter circuit unit 4 at the time of abnormality, that is, during interconnection, or commercial operation When the power supply system 7 is in a power failure state,
The opening / closing part 5 is opened.

[0005]

By the way, it is well known that the period of the above interconnection is significantly longer than the period of abnormality or power failure. Further, in the above-described photovoltaic power generation system, in order to maintain the interconnection state, it is necessary to continuously supply the exciting current to the exciting coil of the AC contactor device of the disconnecting switch. Therefore, in the power conversion device described above, the consumption current in the steady state is large by the amount of this exciting current, and the conversion efficiency is low.

The present invention has been made in view of the above circumstances, and an object of the present invention is to eliminate the current consumed by the disconnecting switch in a steady state and to improve the efficiency of the solar power generation system. An object is to provide an efficient power conversion device.

[0007]

In order to achieve the above object, a power conversion device according to claim 1 is a power conversion device that supplies power to a load by linking with a commercial power supply system, and a direct current power supply. A power conversion unit that converts the power input from the AC to output the AC power, a voltage detection unit that detects the output voltage of the power conversion unit, and a disconnecting switch that disconnects the interconnection with the commercial power supply system, In the power conversion device having an opening / closing operation section for operating the disconnecting switch, the disconnecting switch has an opening / closing structure having a self-holding function. As a result, the switching section of the disconnecting switch is maintained in the interconnected state when the system voltage and the inverter output voltage are normal even if the exciting current is not continuously present, and the disconnecting state is released when these voltages are abnormal. .

The power converter according to a second aspect of the invention has, in addition to the opening / closing operation section of the first aspect, a charging section that is charged at the time of interconnection, and the parallel disconnection switching is performed by the charge energy of the charging section. The vessel is supposed to be operated. Accordingly, the power supply circuit for operating the disconnecting switch is formed to have the charging section.

Further, in the power converter according to the third aspect, in addition to the voltage detecting section according to the first or the second aspect, the output voltage is input to the optical insulation element to detect the output voltage. As a result, the opening / closing operation section that operates the disconnecting switch is insulated from the power circuit by the optical isolation element.

In addition to the voltage detecting unit according to the first to third aspects, the power converter according to the fourth aspect detects both an overvoltage and an undervoltage. As a result, the overvoltage and the undervoltage are detected by the one voltage detection unit.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a power converter according to the present invention will be described below with reference to FIGS. 1 and 2. FIG.
FIG. 2 is a system configuration diagram of the power conversion device of the present invention, and FIG. 2 is a circuit configuration diagram of an AC voltage detection circuit and a switch drive circuit, which are main parts of the power conversion device of the present invention.

The power converter 4 has a solar cell 1 as a DC power source connected to an input side and loads 6, 6 connected to an output side. The loads 6 and 6 are connected to the power conversion device 2 and the commercial power supply system 7 via a neutral wire of single-phase three-wire wiring. Then, the power conversion device 2 converts the DC power input from the solar cell 1 into AC power, and supplies this AC power to the load 6 and the commercial power supply system 7.

The power converter 4 is, as shown in FIG.
Similar to the conventional example, the diode D1 which is a diode for preventing current from flowing back to the input stage and the solar cell 1
And a capacitor C1 which is a capacitor for smoothing the input voltage from. And an inverter circuit 4a,
Inverter drive circuit 4b, AC voltage detection circuits 4c and 4c that are voltage detection units, AC current detection circuit 4d, DC voltage detection circuit 4f, inverter control circuit 4g, and switch drive circuit 4e that is a switching operation unit. And the opening / closing parts 5a, 5
It is constituted by a polar type latching relay 5 which is a disconnecting switch having a and 5a.

The inverter circuit 4a is composed of switch elements Q1, Q2, Q which are bridge-connected to form an inverter.
3, Q4, a choke coil L1 forming a low-pass filter connected to the output terminal of the inverter circuit, and a capacitor C2. In addition, diodes D1, D2, D3, and D4 are connected between the emitters and collectors of the switch elements Q1, Q2, Q3, and Q4 such that the emitter side of each is the anode and the collector side is the cathode.

The inverter drive circuit 4b is a PWM for controlling switching of the switch elements Q1, Q2, Q3 and Q4.
The control circuit inputs the PWM control signal from the inverter control circuit 4f to control switching of the switch elements Q1, Q2, Q3, Q4.

The AC voltage detection circuits 4c and 4c are connected to the load 6,
6 is a circuit for detecting an AC voltage applied to the circuit 6. One end of each of the AC voltage detection circuits 4c and 4c is an inverter circuit 4
Bidirectional input type photocoupler PC1 (PC2) whose one end and the other end of the output of a are connected to the neutral line through R1 (R2)
And a triac T1 (T2) connected to both ends of the input terminal of the bidirectional input type photocoupler PC1 (PC2),
A resistor R3 having one end connected to the gate input of the triac T1 (T2) and the other end connected to one end of the output of the inverter circuit 4a.
(R4) and the cathodes are connected in series by connecting the cathodes, one end of the anode is the gate of the triac T1 (T2), and the other end is the bidirectional input photocoupler PC1 (PC
2) Zener diodes ZD1 and ZD2 (ZD3 and ZD) connected to the connection between the input terminal and the resistor R1 (R2)
4) and are comprised. Here, the Zener diodes ZD1 and ZD2 (ZD3 and ZD4) are connected in series with mutually opposite polarities. Then, when the inverter circuit 4a is connected to the commercial power supply system 7 via the opening / closing sections 5a, 5a, 5a, one end of the output of the inverter circuit 4a and the neutral line are connected to the input terminal of the bidirectional input photocoupler PC1 (PC2). The voltage between the lines is input to detect an abnormal voltage value, that is, a voltage rise and a voltage drop over a predetermined voltage range, and a switch is driven from the output terminal of the bidirectional input photocoupler PC1 (PC2). The detection signal is output to the circuit 4e. Further, the AC voltage detection circuits 4c and 4c simultaneously output the detection signal to an inverter control circuit 4g described later.

The AC current detection circuit 4d is a circuit for detecting an AC current flowing through the loads 6 and 6, and is provided by one or both of the connection lines between the inverter circuit 4a and the switching section 5a. The output is input and an alternating current signal is output to the inverter control circuit 4f described later.

The switch drive circuit 4e includes an open / close unit 5 which will be described later.
It is a relay operation circuit for driving the polarized latching relay 5 having a. This switch drive circuit 4e includes a diode bridge DB1 and a capacitor C3 that rectify and smooth the output voltage of the inverter circuit 4a, and an AC voltage detection circuit 4
c, a resistor R5 (R6) for pulling up the output from the capacitor C3 to the positive electrode side of the capacitor C3, and one end of the set operation coil 5b of the polar type latching relay 5 described later is the collector terminal, and the positive electrode side of the capacitor C3 is Switch S
A transistor Q4 connected to the base terminal via W1 and a resistor R9 to control the exciting current of the operating coil 5b, one end of the reset operating coil 5c is a collector terminal, and outputs from the AC voltage detection circuits 4c and 4c are diodes D5 ( D
6) and a transistor Q5 connected to the base terminal via a resistor R7 and controlling the exciting current of the operating coil 5c. In the figure, C4 and C5 are noise absorbing capacitors, and R8 and R10 are transistors Q4 and Q5.
This is a bias resistor.

The DC voltage detection circuit 4f includes a capacitor C1.
The voltage detection circuit that detects the DC voltage across the two ends outputs the DC voltage signal of the solar cell 1 to the inverter control circuit 4g.

The inverter control circuit 4g is a circuit for outputting the drive signal of the inverter drive circuit 4b. The inverter control circuit 4g receives the AC voltage signal from the AC voltage detection circuit 4c, the AC current signal from the AC current detection circuit 4d, and the DC voltage signal from the DC voltage detection circuit 4f to maximize the power generation efficiency of the solar cell 1. The PWM control signal of the inverter circuit 4a is changed so that

The polarized latching relay 5 is a disconnecting switch that opens and closes the connection between the power converter 4 and the commercial power system 7, and is arranged between the output of the power converter 4 and the connecting line between the commercial power system 7. Three open / close parts 5a, 5a, 5a provided and the open / close part 5a
It is configured to have a set operation coil 5b for opening / closing and a reset operation coil 5c. In this polarized latching relay 5, the three-pole switching parts 5a, 5a, 5a are closed by a pulsed exciting current flowing through the set operating coil 5b, and a pulsed exciting current flows through the reset operating coil 5c. The open state is maintained, and the state immediately before that is maintained even when there is no exciting current.

Next, the operation of the power conversion device having the above configuration will be described. When DC power is output from the solar cell 1, first, it is stored in the capacitor C1. By this capacitor C1, the DC voltage output from the solar cell, which changes from 0 to approximately 300 V and constantly changes, is smoothed and input to the inverter circuit 4a. Then, it is switched by the switch elements Q1, Q2, Q3, Q4 forming the inverter bridge of the inverter circuit 4a, and is converted into a substantially sine wave current including harmonic components synchronized with the commercial power supply. This substantially sine wave current is converted into a commercial power source smoothed by a low pass filter including a choke coil L1 and a capacitor C2, and output as an alternating current. The alternating current output is generated by pressing the set switch SW1 of the switch drive circuit 4e and passing an operating current through the set operating coil 5b through the transistor Q4 for about 1 second, thereby opening / closing the opening / closing sections 5a, 5a, 5a. Becomes a closed state, is combined with the supply current from the commercial power supply system 7, and is input to the loads 6, 6.

If the output of the solar cell 1 is converted to a normal voltage value by the power converter 4 and the commercial power supply system 7 is in the power supply state, the closed state of the opening / closing section 5 is continued and the interconnection is established. Maintained. Then, at the time of abnormality, that is, when the voltage increase or voltage decrease is detected by the AC voltage detection circuit 4c, the photocoupler PC1 or PC2 is turned off, and the opening / closing unit 5 is opened.
Is opened. Specifically, when an overvoltage is generated in the connection line between the inverter circuit 4a and the opening / closing section 5a, any one of the Zener diodes ZD1, ZD2, ZD3, and ZD4 is turned on in accordance with the polarity of the overvoltage. Then, the triac T1 or T2 whose Zener diode is connected to the gate terminal is turned on. Then, the photocoupler PC1 or PC2 is turned off, the voltage on the cathode side of the diode D5 or D6 rises, and an operation current flows through the reset operation coil 5c of the polar type latching relay 5 via the transistor Q5 to open / close the opening / closing section 5a. 5a, 5
a is in an open state. Also, when the output of the inverter circuit 4a is significantly reduced or turned off, the photocoupler PC1,
The PC2 is turned off, the voltage on the cathode side of the diode D5 or D6 rises, and the reset operation coil 5c of the polar type latching relay 5 is connected via the transistor Q5.
The operating current flows from the capacitor C3, and the opening / closing sections 5a, 5
a and 5a are opened.

In the above operation, since the disconnecting switch is the polar type latching relay 5, the opening / closing section 5a is
The exciting current is set only when the interconnection is started, and the steady interconnection state is maintained even if there is no exciting current thereafter, and the excitation current for the interconnection state at the disconnect switch is unnecessary. Becomes Therefore, the conversion efficiency of the power conversion device 4 is high. In addition, the operation energy of the capacitor C3 is used to operate the operation coils 5b and 5c of the polar type latching relay 5. As a result, the power supply circuit for operating the polarized latching relay 5 is formed with the charging portion, that is, the capacitor C3, and the opening / closing portion 5a is reliably operated even when the output of the inverter circuit 4a is significantly reduced or turned off. It will be one. In addition, the AC voltage detection circuits 4c and 4c have a bidirectional input photocoupler PC1 (PC) at the input portion of the AC voltage output from the inverter circuit 4a.
By using 2), the voltage can be detected with a simple circuit configuration. Furthermore, the switch drive circuit 4e, which is an opening / closing operation section for operating the polarized latching relay 5, is insulated from the power circuit by an optical insulation element. Therefore,
The switch drive circuit 4e operates the polarized latching relay 5 only by the power supply circuit formed by the diode bridge DB1 and the capacitor C3 that rectifies and smoothes the output voltage of the inverter circuit 4a. As a result, a stable circuit operation is possible with a circuit configuration in which current does not sneak. The AC voltage detection circuits 4c and 4c are connected to the input side of the bidirectional input type photocoupler PC1 (PC2) by the triac T.
1 (T2) and Zener diodes ZD1 and ZD2 (Z
D3, ZD4) is added to the circuit for detecting an overvoltage to detect both the undervoltage and the overvoltage, so that the switch drive circuit 4e for operating the polarized latching relay 5 is set to the undervoltage. This has an effect that the circuit can be simplified because it can be used for both abnormal operation of overvoltage.

In the description of the embodiments of the present invention, the disconnecting switch has been described as a polar type latching relay, but the present invention is not limited to this, and a rotary relay or the like may be used as appropriate. Also, the optical insulation element has been described as a bidirectional input type photocoupler element, but it may be a magnetic signal transmission means. Further, the operating portion of the polarized latching relay is not limited to one having a capacitor or the like that is charged at the time of interconnection, and a power source may be appropriately configured. Further, the AC voltage detection circuit is not limited to one that detects both overvoltage and undervoltage.

[0026]

In the power converter according to the first aspect of the present invention, the switching section of the parallel disconnecting switch is maintained in the interconnected state when the system voltage and the inverter output voltage are normal even when the exciting current is not continuously applied. Since the disconnection state is released when these voltages are abnormal,
A continuous exciting current is unnecessary, and the conversion efficiency of the power converter is high.

In addition to the effect of the power conversion device according to the first aspect of the present invention, the power supply circuit for operating the decoupling switch is formed to have the charging section. The opening / closing part can be reliably operated even when the output of is significantly reduced or turned off.

The power converter according to a third aspect of the present invention is
In addition to the effect of the first or second aspect, since the switching operation section for operating the disconnecting switch is insulated from the power circuit by the optical insulation element, stable circuit operation is possible by the circuit configuration without current sneak. Becomes

The power converter according to a fourth aspect of the present invention is
In addition to the effects of the first to third aspects, since the overvoltage and the undervoltage are detected by one voltage detection unit, the switch drive circuit 4e for operating the polarized latching relay 5 is provided with both the undervoltage and the overvoltage. The circuit can be simplified because it can be used for operation in the event of an abnormality.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an AC voltage detection circuit and a switch drive circuit, which are essential parts of the power conversion device of the present invention.

FIG. 3 is a basic configuration diagram of a conventional photovoltaic power generation system.

[Explanation of symbols]

1 Solar Cell 4 Power Converter 4a Inverter Circuit (Power Converter) 4c AC Voltage Detector (Voltage Detector) PC1, PC2 Bidirectional Input Photocoupler (Optical Insulation Device) 4e Switch Driver Circuit (Switch Operator) C3 Capacitor (charging part) 5 Polarized latching relay (disconnect switch) 5a Switching part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H02M 7/48 9181-5H H02M 7/48 R H02N 6/00 H02N 6/00

Claims (4)

[Claims] 1. A power conversion device that supplies power to a load by linking with a commercial power supply system, the power conversion unit converting power input from a DC power supply into AC and outputting the AC, and the power conversion unit. In the power conversion device, there is provided a voltage detecting unit for detecting an output voltage of the power converter, a disconnecting switch for disconnecting an interconnection with a commercial power supply system, and an opening / closing operating unit for operating the disconnecting switch. The row switch has an opening / closing structure having a self-holding function. 2. The opening / closing operation section has a charging section that is charged when the connection is established, and the disconnection switch is operated by the charge energy of the charging section. Power converter. 3. The voltage detecting unit inputs the output voltage to an optical insulation element to detect the output voltage.
The power converter according to any one of the preceding claims. 4. The power conversion device according to claim 1, wherein the voltage detection unit detects both an overvoltage and an undervoltage.