JPWO2013157091A1 - Grid-connected inverter device - Google Patents

Abstract

The grid-connected inverter device is a grid-connected inverter device that links a DC power source to a commercial power system, and includes an inverter main circuit unit that converts DC power into AC power, and the inverter main circuit unit from the commercial power system. A switch to be disconnected, a first voltage detector for detecting a voltage on the inverter main circuit side with respect to the switch, and a second voltage detector for detecting a voltage on the commercial power system side with respect to the switch An error corrector that holds a detection error correction value for correcting a phase error included in the detection value of the first voltage detector and the detection value of the second voltage detector; and An inverter control unit for controlling the inverter main circuit unit based on a detection value of the voltage detector, a detection value of the second voltage detector, and a detection error correction value held in the error corrector;

Description

  The present invention relates to a grid interconnection inverter device.

  The grid interconnection inverter device receives DC power generated by the solar battery, converts the DC power into AC power by the inverter, and supplies the converted AC power to the commercial power system. In the grid-connected inverter device, since it is necessary to disconnect the inverter from the commercial power system at night when the solar cell is not generating power, a switch is provided between the inverter and the commercial power system.

  In Patent Document 1, in a grid-connected inverter device in which an inverter main circuit includes a switching element and a filter, two switches are interposed in two lines other than the neutral line of the commercial power system, and the filter It is described that a resistor is connected between the middle point of the capacitor in the middle and the neutral line of the commercial power system to provide a predetermined time difference between the timings at which the two switches are turned on. Thereby, according to patent document 1, the balance of the phase voltage is not disturbed by the prior input of one switch, and the commercial power system when the other one switch is subsequently switched from the grid-connected inverter device. It is said that it is possible to suppress inrush current inflow.

  In Patent Document 2, a distributed power source configured to output a sinusoidal AC voltage using a booster circuit, an inverter circuit, and a filter circuit using a solar cell as a power source is connected to a commercial power source 3 via a disconnecting switch. In a photovoltaic power generation system connected to two main lines, it is described that a disconnection switch is closed and system interconnection is started after an on / off operation of a switching element of an inverter circuit is started. Thus, according to Patent Document 2, the main circuit breaker (earth leakage breaker) between the disconnecting switch and the commercial power source does not operate due to the ground fault generated in the distributed power source, and the commercial power source is normal. Regardless, it is said that the malfunction that the main breaker is cut off can be prevented.

Japanese Patent No. 3911157 Japanese Patent No. 3563967

  In the technique described in Patent Document 1, the resistor is necessary only when closing the switch because the inverter is connected to the commercial system, and is not necessary in a normal operation state. Moreover, in the technique described in Patent Document 1, there is a power loss due to a resistor, and conversion efficiency may be reduced as a whole of the grid-connected inverter device.

  In the technique described in Patent Document 2, there is no description about the inrush current, and there is no description about how to suppress the inrush current.

  The present invention has been made in view of the above, and obtains a grid-connected inverter device capable of improving the conversion efficiency of the grid-connected inverter device and suppressing the inrush current from the commercial power system to the grid-connected inverter device. For the purpose.

  In order to solve the above-described problems and achieve the object, a grid-connected inverter device according to one aspect of the present invention is a grid-connected inverter device that links a DC power source to a commercial power system, and includes DC power Main circuit unit for converting AC to AC power, a switch for disconnecting the inverter main circuit unit from a commercial power system, and a first voltage detector for detecting the voltage on the inverter main circuit unit side with respect to the switch And a phase included in a second voltage detector that detects a voltage on the commercial power system side with respect to the switch, a detected value of the first voltage detector, and a detected value of the second voltage detector An error corrector that holds a detection error correction value for correcting an error, a detection value of the first voltage detector, a detection value of the second voltage detector, and a detection error held in the error corrector Based on the correction value and Characterized by comprising an inverter control unit for controlling the serial inverter main circuit unit.

  According to the present invention, the inverter main circuit unit is controlled based on the detection value of the first voltage detector, the detection value of the second voltage detector, and the detection error correction value held in the error corrector. The increase of the inrush current due to the variation in the voltage detection accuracy between the first voltage detector and the second voltage detector can be suppressed. In addition, since the inrush current can be suppressed without using a resistor, and a resistor dedicated to inrush current suppression is not required, the loss of AC power that the grid-connected inverter device should supply to the commercial power system can be reduced. The conversion efficiency of the entire system inverter device can be improved. That is, the efficiency of the grid interconnection inverter device can be improved, and the inrush current from the commercial power system to the grid interconnection inverter device can be suppressed.

FIG. 1 is a diagram illustrating a configuration of a grid-connected inverter device according to an embodiment. FIG. 2 is a diagram showing a configuration of a grid interconnection inverter device according to a basic form.

  Embodiments of a grid-connected inverter device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
Before describing the grid interconnection inverter device 100 according to the embodiment, the grid interconnection inverter device 1 according to the basic mode will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration of the grid interconnection inverter device 1 according to the basic mode. In the following, a case where the grid-connected inverter device 1 is connected to the single-phase three-wire commercial power system AC will be exemplarily described. However, a connection form between the grid-connected inverter device 1 and the commercial power system AC is described. This is not the case.

  The grid-connected inverter device 1 links the DC power source DC to the commercial power grid AC. The DC power source DC is a solar cell, for example, and generates DC power. That is, the grid-connected inverter device 1 receives DC power generated by the DC power source DC, converts the DC power into AC power by the inverter main circuit unit 4, and supplies the converted AC power to the commercial power system AC. To do. In the grid-connected inverter device 1, since the inverter main circuit unit 4 needs to be disconnected from the commercial power system AC at night when the DC power source DC (for example, a solar cell) is not generating power, the inverter main circuit unit Switches 7a and 7b are provided between 4 and the commercial power system AC.

  Specifically, as shown in FIG. 2, the grid-connected inverter device 1 has two input terminals IN1, IN2 connected to both ends of the DC power source DC, that is, the P-side end and the N-side terminal, and three output terminals. OUT1 to OUT3 are connected to three lines of the commercial power system AC. The grid-connected inverter device 1 includes a smoothing circuit 3, an inverter main circuit unit 4, a filter circuit 6, two voltage lines VL1 and VL2, a neutral line ML, two switches 7a and 7b, a resistor 8, and inverter control. Part 5 and opening / closing control part 2.

  The smoothing circuit 3 receives direct current power from the direct current power source DC via the input terminals IN1 and IN2. The smoothing circuit 3 has, for example, a smoothing capacitor C3, smoothes DC power using the smoothing capacitor C3, and supplies it to the inverter main circuit unit 4.

  The inverter main circuit unit 4 receives the smoothed DC power from the smoothing circuit 3. The inverter main circuit unit 4 converts DC power into AC power. The inverter main circuit unit 4 includes, for example, a plurality of switching elements Q1 to Q4, and performs a switching operation in which the plurality of switching elements Q1 to Q4 are turned on / off at a predetermined timing under the control of the inverter control unit 5. , DC power is converted to AC power. Each of the switching elements Q1 to Q4 includes, for example, a field effect transistor (FET) such as a MOS transistor and a free wheel diode for protecting the field effect transistor. Alternatively, each switching element Q1 to Q4 may include, for example, an insulated gate bipolar transistor (IGBT) and a free-wheeling diode for protecting the insulated gate bipolar transistor, although not shown. The inverter main circuit unit 4 supplies the converted AC power to the filter circuit 6 from the output nodes 4a and 4b.

  The filter circuit 6 receives AC power from the inverter main circuit unit 4. The filter circuit 6 attenuates noise (for example, switching noise accompanying switching of the switching elements Q1 to Q4) included in the AC power output from the inverter main circuit unit 4. The filter circuit 6 includes, for example, two reactors L1 and L2 and two capacitors C1 and C2. For example, the two reactors L1 and L2 are inserted in series between the input nodes 6a and 6b of the filter circuit 6 and the output nodes N1 and N2, respectively. Both ends of the two capacitors C1 and C2 are connected to the two output nodes N1 and N2 of the filter circuit 6, and the midpoint of the two capacitors C1 and C2 is connected to the other output node N3 of the filter circuit 6. ing. The filter circuit 6 attenuates noise included in the AC power using, for example, two reactors L1 and L2 and two capacitors C1 and C2, and outputs the attenuated noise from the three output nodes N1 to N3.

  The two voltage lines VL1 and VL2 are provided to connect the two output nodes N1 and N2 and the two output terminals OUT1 and OUT2 when the two switches 7a and 7b are closed. That is, the two voltage lines VL1 and VL2 are arranged between both ends of the two capacitors C1 and C2 and the commercial power system AC.

  The neutral line ML connects the output node N3 and the output terminal OUT3. That is, the neutral line ML is arranged between the midpoint of the two capacitors C1 and C2 and the commercial power system AC.

  The two switches 7a and 7b disconnect the inverter main circuit unit 4 from the commercial power system AC, for example, at night when the DC power source DC (for example, a solar battery) is not generating power. In the daytime when the solar cell is generating power, the inverter main circuit unit 4 is connected to the commercial power system AC.

  Specifically, the two switches 7a and 7b are provided on the two voltage lines VL1 and VL2. For example, the switch 7a electrically connects the output node N1 and the output terminal OUT1 when closed, and electrically disconnects the output node N1 and the output terminal OUT1 when opened. For example, the switch 7b electrically connects the output node N2 and the output terminal OUT2 when closed, and electrically disconnects the output node N2 and the output terminal OUT2 when opened. The two switches 7a and 7b disconnect the inverter main circuit unit 4 from the commercial power system AC when both are opened, and connect the inverter main circuit unit 4 to the commercial power system AC when both are closed. Make it.

  The resistor 8 suppresses inrush current from the commercial power system AC to the inverter main circuit unit 4 when connecting the inverter main circuit unit 4 to the commercial power system AC, that is, when the two switches 7a and 7b are closed. To do. That is, the resistor 8 is provided in order to prevent the contact life of the switches 7a and 7b from being reduced due to the inrush current.

  Specifically, the resistor 8 is provided on the neutral line ML. That is, the resistor 8 has one end electrically connected to the output node N3 and the other end electrically connected to the output terminal OUT3.

  The inverter control unit 5 supplies a control signal to each control terminal of the plurality of switching elements Q1 to Q4, and turns on / off the plurality of switching elements Q1 to Q4 respectively at a predetermined timing to perform a switching operation. When the inverter controller 5 starts the switching operation of the plurality of switching elements Q1 to Q4, the inverter controller 5 notifies the switching controller 2 to that effect. Moreover, the inverter control part 5 notifies that to the opening / closing control part 2, when complete | finishing switching operation | movement of the some switching elements Q1-Q4.

  When the switching control unit 2 receives a notification that the switching operations of the plurality of switching elements Q1 to Q4 have started, the two switches 7a and 7b are closed so that the two switches 7a and 7b are closed in response to the notification. To control. In addition, when the switching control unit 2 receives a notification that the switching operation of the plurality of switching elements Q1 to Q4 is finished, the two switches 7a and 7b are opened so that the two switches 7a and 7b are opened in response to the notification. , 7b.

  In this grid-connected inverter device 1, the resistor 8 is provided only to suppress the inrush current from the commercial power system AC to the inverter main circuit unit 4 when the two switches 7 a and 7 b are closed. It is an element and is necessary only when the switch 7 is closed in order to connect the inverter to the commercial system, and is not necessary in a normal operation state. That is, in a normal operation state, the resistor 8 is a useless component for the grid interconnection inverter device 1, and there is a possibility that the manufacturing cost of the grid interconnection inverter device 1 is wasted.

  Further, in a normal operation state, there is a power loss of the resistor 8 itself in the grid interconnection inverter device 1, and the AC power to be supplied to the commercial power grid AC by the grid interconnection inverter device 1 is converted into thermal energy by the resistor 8. The conversion efficiency of the grid-connected inverter device 1 as a whole may be reduced.

  Further, in the grid-connected inverter device 1, after starting the switching operation of the plurality of switching elements Q1 to Q4 of the inverter main circuit unit 4, the two switches 7a and 7b are closed to connect the inverter main circuit unit 4 to the commercial power system AC. However, with respect to the two switches 7a and 7b, the voltage between the output node N1 and the output node N2 on the inverter main circuit unit 4 side and the output on the commercial power system AC side are connected to the two switches 7a and 7b. There may be a voltage difference from the voltage between the terminal OUT1 and the output terminal OUT2. The grid-connected inverter device 1 cannot recognize such a voltage difference at all. If such a voltage difference is large, an inrush current from the commercial power system AC to the inverter main circuit unit 4 may be generated depending on the wiring impedance. May increase.

  Therefore, in the present embodiment, as shown in FIG. 1, in the grid-connected inverter device 100, the resistor 8 is removed from the neutral wire ML and the inverter main circuit is connected to the two switches 7a and 7b. The voltage between the output node N1 and the output node N2 on the part 4 side is detected by the first voltage detector 19, and the voltage between the output terminal OUT1 and the output terminal OUT2 on the commercial power system AC side is detected with the second voltage The voltage difference is obtained by detecting with the voltage detector 18 and obtaining the difference between the detected value of the first voltage detector 19 and the detected value of the second voltage detector 18 with the inverter control unit 15. The inverter control unit 15 controls the inverter main circuit unit 4 with the two switches 7a and 7b opened to synchronize the output voltage of the inverter main circuit unit 4 and the voltage of the commercial power system AC. It aims at suppressing inrush current from commercial power system AC at the time of closing switches 7a and 7b after that to inverter main circuit part 4.

  Here, it is assumed that the inverter control unit 15 uses the voltage difference obtained as the difference between the detection value of the first voltage detector 19 and the detection value of the second voltage detector 18 as it is, so that the inverter main circuit unit 4 Consider a case where the switching operations of a plurality of switching elements Q1 to Q4 are controlled. In this case, the first voltage detector 19 and the second voltage detector 18 tend to have variations in their voltage detection accuracy, and the output of the inverter main circuit unit 4 is affected by the variation in the voltage detection accuracy. It is difficult to synchronize the voltage and the voltage of the commercial power system AC, and it is difficult to suppress the inrush current.

  Therefore, in the present embodiment, in the grid-connected inverter device 100, the phase error included in the detection value of the first voltage detector 19 and the detection value of the second voltage detector 18 is further converted into a phase error detector. A detection error correction value for detecting the phase error and correcting the phase error is held in the error corrector 21, and the inverter control unit 15 detects the detection value of the first voltage detector 19 and the second voltage detection. The voltage difference obtained as a difference from the detection value of the converter 18 is corrected using the detection error correction value held in the error corrector 21, and a plurality of inverter main circuit units 4 are corrected using the corrected voltage difference. The switching operation of the switching elements Q1 to Q4 is controlled.

  Specifically, the first voltage detector 19 and the second voltage detector 18 are configured by general transformers and electronic components. Therefore, even if the actual commercial power supply voltage is detected, the output of the voltage detector causes a phase error with respect to the actual voltage due to the characteristics of the components. In addition, the phase error generated due to the characteristics of individual components varies. Therefore, it is difficult to uniformly determine a correction value for correcting the phase error. However, if the component is a single component, there are few factors that cause the phase error to change. Therefore, if the phase error of the voltage detector is known in advance, the influence of the phase error can be eliminated.

  The phase error detector 20 is a detector for removing the influence of the phase error. For example, when the grid-connected inverter device 100 is shipped from the factory, the first voltage detector 19 and the second voltage detector 19 are used. The phase error of the voltage detector 18 is detected, and the detected phase error is supplied to the error corrector 21.

  The error corrector 21 receives the detected phase error from the phase error detector 20. The error corrector 21 obtains a detection error correction value for correcting the phase error, and records and holds the obtained detection error correction value. In addition, since the phase error detector 20 is necessary only at the time of shipment from the factory, the phase error detector 20 may not be mounted on the grid interconnection inverter device 100.

  The error corrector 21 records and holds a detection error correction value for correcting the phase error detected by the phase error detector 20, and outputs the detection error correction value to the inverter control unit 15.

  The inverter control unit 15 uses the detection error correction value in a state where the two switches 7a and 7b are opened, so that the output voltage of the inverter main circuit unit 4 and the voltage of the commercial power system AC are synchronized. The circuit unit 4 is controlled. That is, the inverter control unit 15 uses the detection error correction value to perform a plurality of switching operations of the inverter main circuit unit 4 so that the phase of the output voltage of the inverter main circuit unit 4 matches the phase of the voltage of the commercial power system AC. The switching operation of the elements Q1 to Q4 is controlled.

For example, the detection value of the first voltage detector 19 and V _19, the second detected value of the voltage detector 18 and V _18, PE ₁₉ a phase error included in the detection value of the first voltage detector 19 Assuming that the phase error included in the detection value of the second voltage detector 18 is PE ₁₈ , the voltage difference ΔV before correction is obtained by the following equation 1, for example.
ΔV = V ₁₉ −V ₁₈ Formula 1
At this time, if phase error PE ₁₉ > phase error PE ₁₈ , a correction value ΔV ₁₉ for the detection value V ₁₉ of the first voltage detector 19 is obtained by using the following equation 2, for example, using a predetermined coefficient K.
ΔV ₁₉ = K (PE ₁₉ −PE ₁₈ ) Equation 2
When Equation 1 is corrected using the correction value ΔV ₁₉ , the corrected voltage difference ΔV ′ is obtained by Equation 3 below, for example.
ΔV ′ = V ₁₉ + ΔV ₁₉ −V ₁₈ Formula 3

  The inverter control unit 15 includes a plurality of switching elements of the inverter main circuit unit 4 so that the phase of the output voltage of the inverter main circuit unit 4 matches the phase of the voltage of the commercial power system AC according to the corrected voltage difference. The switching operation of Q1 to Q4 is controlled.

  For example, when the phase of the output voltage of the inverter main circuit unit 4 is delayed compared to the phase of the voltage of the commercial power system AC, the inverter control unit 15 generates the control signals for the plurality of switching elements Q1 to Q4. The phase of the carrier wave used is advanced.

  Alternatively, for example, when the phase of the output voltage of the inverter main circuit unit 4 is advanced compared to the phase of the voltage of the commercial power system AC, the inverter control unit 15 generates control signals for the plurality of switching elements Q1 to Q4. The phase of the carrier wave used at the time is delayed.

  Then, when the corrected voltage difference falls within a predetermined allowable range, the inverter control unit 15 determines that the output voltage of the inverter main circuit unit 4 and the voltage of the commercial power system AC are synchronized, and accordingly. Notify the opening / closing controller 12. Moreover, the inverter control part 15 notifies that to the switching control part 12, when complete | finishing switching operation | movement of several switching element Q1-Q4.

  When the switching control unit 12 receives a notification that the output voltage of the inverter main circuit unit 4 and the voltage of the commercial power system AC are synchronized, the two switching units 7a and 7b are closed according to the notification. The switches 7a and 7b are controlled. When the switching control unit 12 receives a notification that the switching operations of the plurality of switching elements Q1 to Q4 are finished, the two switches 7a and 7b are opened so that the two switches 7a and 7b are opened according to the notification. , 7b.

  As described above, in the embodiment, in the grid-connected inverter device 100, the first voltage detector 19 detects the voltage on the inverter main circuit unit 4 side with respect to the switches 7a and 7b, and the second voltage detection. The device 18 detects the voltage on the commercial power system AC side with respect to the switches 7a and 7b. The error corrector 21 holds a detection error correction value for correcting a phase error included in the detection value of the first voltage detector 19 and the detection value of the second voltage detector 18. Based on the detection value of the first voltage detector 19, the detection value of the second voltage detector 18, and the detection error correction value held in the error corrector 21, the inverter control unit 15 To control. Thereby, an increase in inrush current due to variations in voltage detection accuracy between the first voltage detector 19 and the second voltage detector 18 can be suppressed. In addition, since the inrush current can be suppressed without using a resistor, and a resistor dedicated to inrush current suppression is not required, the loss of AC power that the grid interconnection inverter device 100 should supply to the commercial power system AC can be reduced. Conversion efficiency can be improved as a whole of the grid interconnection inverter device 100. That is, the conversion efficiency of the grid interconnection inverter device 100 can be improved, and the inrush current from the commercial power system AC to the grid interconnection inverter device 100 can be suppressed.

  In the embodiment, since a resistor dedicated to inrush current suppression is not required, the manufacturing cost of the grid-connected inverter device 100 can be reduced.

  Further, in the embodiment, the inverter control unit 15 has the detection value of the first voltage detector 19, the detection value of the second voltage detector 18, and the error corrector 21 with the switches 7 a and 7 b opened. Is controlled so that the output voltage of the inverter main circuit unit 4 and the voltage of the commercial power system AC are synchronized with each other. Thereby, when the switches 7a and 7b are closed thereafter, the inrush current from the commercial power system AC to the grid-connected inverter device 100 can be effectively suppressed.

  In the embodiment, the two switches 7a and 7b are provided on the two voltage lines VL1 and VL2, and the first voltage detector 19 is provided on the two voltage lines VL1 on the filter circuit 6 side. , VL2 is detected, and the second voltage detector 18 detects the voltage between the two voltage lines VL1 and VL2 on the commercial power system AC side. Thereby, since the number of switches can be reduced compared with the case where a switch is provided also in neutral line ML, the manufacturing cost of the grid connection inverter apparatus 100 can be reduced. Further, since the first voltage detector 19 and the second voltage detector 18 detect the voltage between the two voltage lines VL1 and VL2 provided with the two switches 7a and 7b, the resistor 8 (FIG. 2), it is possible to effectively prevent the contact life of the switches 7a and 7b from being reduced due to the inrush current.

  As described above, the grid interconnection inverter device according to the present invention is useful for interconnection between a solar cell and a commercial power system.

DESCRIPTION OF SYMBOLS 1 Grid connection inverter apparatus 2 Switching control part 3 Smoothing circuit 4 Inverter main circuit part 5 Inverter control part 6 Filter circuit 7a, 7b Switch 8 Resistor 12 Opening / closing control part 15 Inverter control part 18 2nd voltage detector 19 1st 1 voltage detector 20 phase error detector 21 error corrector 100 grid-connected inverter device

Claims (3)

A grid-connected inverter device that links a DC power source to a commercial power system,
An inverter main circuit for converting DC power to AC power;
A switch for disconnecting the inverter main circuit from the commercial power system;
A first voltage detector for detecting a voltage on the inverter main circuit side with respect to the switch;
A second voltage detector for detecting a voltage on the commercial power system side with respect to the switch;
An error corrector that holds a detection error correction value for correcting a phase error included in the detection value of the first voltage detector and the detection value of the second voltage detector;
An inverter control unit that controls the inverter main circuit unit based on a detection value of the first voltage detector, a detection value of the second voltage detector, and a detection error correction value held in the error corrector When,
A grid-connected inverter device comprising: The inverter control unit includes a detection value of the first voltage detector, a detection value of the second voltage detector, and a detection error correction value held in the error corrector while the switch is open. 2. The grid-connected inverter device according to claim 1, wherein the inverter main circuit unit is controlled so that an output voltage of the inverter main circuit unit and a voltage of the commercial power system are synchronized with each other. A filter circuit having two reactors and two capacitors, for attenuating noise included in the AC power output from the inverter main circuit unit;
Two voltage lines arranged between both ends of the two capacitors and the commercial power system;
A neutral wire disposed between the midpoint of the two capacitors and the commercial power system;
Further comprising
The two switches are provided on the two voltage lines,
The first voltage detector detects a voltage between the two voltage lines on the filter circuit side,
The grid-connected inverter device according to claim 1 or 2, wherein the second voltage detector detects a voltage between the two voltage lines on the commercial power system side.

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