JP6537723B2 - Grid-connected inverter device - Google Patents

Description

  The present invention relates to a grid-connected inverter device linked to a commercial power system.

  The grid-connected inverter device converts the DC voltage boosted in each of the converter circuits, which are a plurality of step-up choppers for boosting the voltage output from each of the plurality of solar cells, into an AC voltage. And an inverter unit.

  The converter circuit is configured by combining a switching element represented by a transistor, a reactor, a capacitor and a diode. In the case where a plurality of converter circuits configured in this manner are connected in parallel, when a failure occurs in a diode that constitutes a part of the plurality of converter circuits and a short circuit failure occurs, the output side Current flows from the DC power supply of another converter circuit to be connected back to the input side, that is, the DC power supply side. If such a backflow current is input to a DC power supply represented by a solar cell, the DC power supply may be damaged or its performance may be degraded.

  The prior art disclosed in Patent Document 1 determines that the diode has a short circuit failure by detecting that the input DC voltage has risen to the same value as the output voltage of the converter circuit, and stops the converter circuit. This prevents damage or performance degradation of the DC power supply.

Patent No. 5278837 gazette

  When the DC power source connected to the input side of the converter circuit is a solar cell, the number of solar cells connected in series varies depending on the shape of the roof of the house, so the voltage applied to each of the plurality of converter circuits varies It becomes. Specifically, in the grid-connected inverter device including a plurality of sets of converter circuits from the first to the fourth converter circuit, the first input voltage applied to each of the first to the third converter circuits is It is assumed that the diode of the fourth converter circuit is short-circuited, which is identical and the second input voltage applied to the fourth converter circuit is smaller than the first input voltage. At this time, the output voltages of the first to third solar cell strings connected to the first to third converter circuits and the output voltage of the fourth solar cell string connected to the fourth converter circuit And the diode characteristics of each solar cell string cause a reverse current in the fourth solar cell string. The prior art disclosed in Patent Document 1 is configured to detect a diode failure and stop the operation of the converter circuit, but in the above-mentioned event, the reverse current can not be stopped, and the solar cell May cause the performance degradation or damage of the

  This invention is made in view of the above, Comprising: It aims at obtaining the grid connection inverter apparatus which can prevent performance degradation of DC power supply.

In order to solve the problems described above and to achieve the object, the grid-connected inverter device of the present invention comprises a plurality of converter circuits to which power output from each of a plurality of DC power supplies is input, and a plurality of converter circuits. An inverter circuit that converts a DC voltage output from each into an AC voltage, a short circuit fault detection unit that detects a short circuit fault of a diode that configures each of the plurality of converter circuits, and a short circuit fault detection unit detects a short circuit fault of the diode And a gate pulse command generation unit for outputting a gate pulse command for controlling a switching element forming each of the plurality of converter circuits, wherein each of the plurality of converter circuits includes a reactor, a switching element, and a diode. , Boost DC voltage input from each of the plurality of solar cells A converter circuit constituting a voltage divider circuit, wherein a system interconnection inverter device for generating a driving power of the devices constituting the system interconnection inverter device by electric power supplied from the solar cell, short-circuit failure detecting section is a diode The gate pulse command generation unit stops the operation of the switching element forming the converter circuit including the diode short- circuited and detects the short circuit failure , and configures the converter circuit including the diode not short-circuited. And a gate pulse command for shorting the switching element .

  The grid-connected inverter device according to the present invention has the effect of being able to prevent the performance deterioration of the DC power supply.

The figure which shows the solar energy power generation system containing the grid connection inverter apparatus which concerns on Embodiment 1 of this invention. Diagram of converter control unit shown in FIG. 1 Flowchart related to operation at the time of determination of a diode short circuit failure by the converter control unit of the grid interconnection inverter device according to the first embodiment of the present invention A flowchart relating to an operation at the time of determination of a diode short circuit failure by the converter control unit of the grid interconnection inverter device according to Embodiment 2 of the present invention Flowchart related to operation at the time of determination of a diode short circuit failure by the converter control unit of the grid interconnection inverter device according to Embodiment 3 of the present invention

  Hereinafter, a grid interconnection inverter device according to an embodiment of the present invention will be described in detail based on the drawings. The present invention is not limited by the embodiment.

Embodiment 1
FIG. 1 is a view showing a solar power generation system including a grid-connected inverter device according to Embodiment 1 of the present invention. The solar power generation system 100 includes a plurality of solar cell strings 1a, 1b, 1c, and 1d, which are a plurality of direct current power supplies, and a grid-connected inverter device 3 to which the plurality of solar cell strings 1a, 1b, 1c, and 1d are connected. . Below, the some solar cell string 1a, 1b, 1c, 1d may be abbreviate | omitted as "the some solar cell string 1." Each of the plurality of solar cell strings 1 has a configuration in which a plurality of solar cell modules (not shown) are connected in series, and generates DC power according to the amount of solar radiation.

  The grid-connected inverter device 3 includes a converter control unit 16. Converter control unit 16 generates gate pulse commands Gs for controlling each of the plurality of converter circuits 4a, 4b, 4c, 4d, and for each of the plurality of gate pulse generators 17a, 17b, 17c, 17d. Output. The grid-connected inverter device 3 according to the embodiment is characterized by the operation of the gate pulse command Gs by the converter control unit 16. Below, several converter circuits 4a, 4b, 4c, 4d may be abbreviate | omitted as "the several converter circuit 4." In addition, the plurality of gate pulse generators 17a, 17b, 17c, and 17d may be abbreviated as "a plurality of gate pulse generators 17".

  Below, the structure of the apparatus which comprises the grid connection inverter apparatus 3 centering on the converter control part 16 is demonstrated concretely.

  The grid-connected inverter device 3 includes a plurality of positive electrode input terminals 101a, 101b, 101c, and 101d, a plurality of negative electrode input terminals 102a, 102b, 102c, and 102d, and system output terminals 103 and 104.

  The positive electrode output terminal of the solar cell string 1a is connected to the positive electrode input terminal 101a, and the negative electrode output terminal of the solar cell string 1a is connected to the negative electrode input terminal 102a. Likewise, the positive electrode output ends of the solar cell strings 1b, 1c, and 1d are connected to the positive electrode input terminals 101b, 101c, and 101d, respectively. The negative electrode output terminals of the solar cell strings 1b, 1c, and 1d are connected to the negative electrode input terminals 102b, 102c, and 102d, respectively.

  Two grid connection lines connected to the commercial power grid 2 are connected to the grid output terminals 103 and 104.

  The grid-connected inverter device 3 further includes a plurality of smoothing capacitors 7 a, 7 b, 7 c and 7 d, a plurality of converter circuits 4, a smoothing capacitor 8, an inverter circuit 5, and an output relay 6.

  The smoothing capacitor 7 a smoothes the DC voltage output from the solar cell string 1 a and input to the converter circuit 4 a. One end of the smoothing capacitor 7a is connected to the positive electrode input terminal 101a and the positive electrode input end of the converter circuit 4a via the DC bus P on the positive electrode side. The other end of the smoothing capacitor 7a is connected to the negative electrode input terminal 102a and the negative electrode input end of the converter circuit 4a via the DC bus N on the negative electrode side.

  Converter circuit 4a has a reactor 9a, a switching element 10a and a diode 11a.

  One end of the reactor 9a is a positive electrode input end of the converter circuit 4a. One end of the reactor 9a is connected to the positive electrode input terminal 101a and one end of the smoothing capacitor 7a. The other end of the reactor 9a is connected to the anode of the diode 11a and the collector of the switching element 10a.

  The cathode of the diode 11a is a positive output end of the converter circuit 4a. The cathode of the diode 11 a is connected to one end of the smoothing capacitor 8 and the positive input end of the inverter circuit 5.

  The emitter of the switching element 10 a is connected to the other end of the smoothing capacitor 7 a and the other end of the smoothing capacitor 8. The gate pulse signal 17a1 output from the gate pulse generator 17a is input to the gate of the switching element 10a. Gate pulse signal 17a1 is a signal for boosting the voltage output from solar cell string 1a to a voltage necessary for inverter circuit 5 to generate an alternating voltage, or diode 11a shorts switching element 10a when a short circuit failure is detected. It is a signal.

  The gate pulse generator 17a outputs the gate pulse signal 17a1 to the switching element 10a based on the gate pulse command Gs input from the converter control unit.

  Smoothing capacitor 7b smoothes the DC voltage output from solar cell string 1b and input to converter circuit 4b. One end of the smoothing capacitor 7b is connected to the positive electrode input terminal 101b and the positive electrode input end of the converter circuit 4b via the DC bus P on the positive electrode side. The other end of the smoothing capacitor 7b is connected to the negative electrode input terminal 102b and the negative electrode input end of the converter circuit 4b via the DC bus N on the negative electrode side.

  Converter circuit 4b has a reactor 9b, a switching element 10b and a diode 11b.

  One end of the reactor 9 b is a positive electrode input end of the converter circuit 4 b. One end of the reactor 9b is connected to the positive electrode input terminal 101b and one end of the smoothing capacitor 7b. The other end of the reactor 9b is connected to the anode of the diode 11b and the collector of the switching element 10b.

  The cathode of the diode 11 b is a positive output end of the converter circuit 4 b. The cathode of the diode 11 b is connected to one end of the smoothing capacitor 8 and the positive input end of the inverter circuit 5.

  The emitter of the switching element 10 b is connected to the other end of the smoothing capacitor 7 b and the other end of the smoothing capacitor 8. The gate pulse signal 17b1 output from the gate pulse generator 17b is input to the gate of the switching element 10b. The gate pulse signal 17b1 is a signal that boosts the voltage output from the solar cell string 1b to a voltage necessary for the inverter circuit 5 to generate an AC voltage, and the diode 11b shorts the switching element 10b when a short circuit failure is detected. is there.

  The gate pulse generator 17b outputs the gate pulse signal 17b1 to the switching element 10b based on the gate pulse command Gs input from the converter control unit.

  The smoothing capacitor 7c smoothes the DC voltage output from the solar cell string 1c and input to the converter circuit 4c. One end of the smoothing capacitor 7c is connected to the positive electrode input terminal 101c and the positive electrode input end of the converter circuit 4c through the DC bus P on the positive electrode side. The other end of the smoothing capacitor 7c is connected to the negative electrode input terminal 102c and the negative electrode input end of the converter circuit 4c via the DC bus N on the negative electrode side.

  Converter circuit 4c includes a reactor 9c, a switching element 10c and a diode 11c.

  One end of the reactor 9c is a positive electrode input end of the converter circuit 4c. One end of the reactor 9c is connected to the positive electrode input terminal 101c and one end of the smoothing capacitor 7c. The other end of the reactor 9c is connected to the anode of the diode 11c and the collector of the switching element 10c.

  The cathode of the diode 11c is a positive output end of the converter circuit 4c. The cathode of the diode 11 c is connected to one end of the smoothing capacitor 8 and the positive input end of the inverter circuit 5.

  The emitter of the switching element 10 c is connected to the other end of the smoothing capacitor 7 c and the other end of the smoothing capacitor 8. The gate pulse signal 17c1 output from the gate pulse generator 17c is input to the gate of the switching element 10c. The gate pulse signal 17c1 is a signal that boosts the voltage output from the solar cell string 1c to a voltage necessary for the inverter circuit 5 to generate an AC voltage, and the diode 11c shorts the switching element 10c when a short circuit failure is detected. is there.

  The gate pulse generator 17c outputs the gate pulse signal 17c1 to the switching element 10c based on the gate pulse command Gs input from the converter control unit.

  The smoothing capacitor 7d smoothes the DC voltage output from the solar cell string 1d and input to the converter circuit 4d. One end of the smoothing capacitor 7d is connected to the positive electrode input terminal 101d and the positive electrode input end of the converter circuit 4d through the DC bus P on the positive electrode side. The other end of the smoothing capacitor 7d is connected to the negative electrode input terminal 102d and the negative electrode input end of the converter circuit 4d via the DC bus N on the negative electrode side.

  Converter circuit 4d includes a reactor 9d, a switching element 10d and a diode 11d.

  One end of the reactor 9d is a positive electrode input end of the converter circuit 4d. One end of the reactor 9d is connected to the positive electrode input terminal 101d and one end of the smoothing capacitor 7d. The other end of the reactor 9d is connected to the anode of the diode 11d and the collector of the switching element 10d.

  The cathode of the diode 11 d is a positive output end of the converter circuit 4 d. The cathode of the diode 11 d is connected to one end of the smoothing capacitor 8 and the positive input end of the inverter circuit 5.

  The emitter of the switching element 10 d is connected to the other end of the smoothing capacitor 7 d and the other end of the smoothing capacitor 8. The gate pulse signal 17d1 output from the gate pulse generator 17d is input to the gate of the switching element 10d. The gate pulse signal 17d1 is a signal that boosts the voltage output from the solar cell string 1d to a voltage necessary for the inverter circuit 5 to generate an AC voltage, and the diode 11d shorts the switching element 10d when a short circuit failure is detected. is there.

  The gate pulse generator 17d outputs the gate pulse signal 17d1 to the switching element 10d based on the gate pulse command Gs input from the converter control unit.

  One end of the smoothing capacitor 8 is connected to the cathode of each of the plurality of diodes 11 a, 11 b, 11 c, and 11 d and the positive input end of the inverter circuit 5. The other end of the smoothing capacitor 8 is connected to the anode of each of the plurality of diodes 11 a, 11 b, 11 c, 11 d and the negative input end of the inverter circuit 5. The smoothing capacitor 8 smoothes the DC voltage output from each of the plurality of converter circuits 4 and input to the inverter circuit 5.

  The inverter circuit 5 operates to convert the charging voltage of the smoothing capacitor 8 into an AC voltage. The AC output terminal of the inverter circuit 5 is connected to the system output terminals 103 and 104 via the output relay 6.

  The output relay 6 is disposed between the inverter circuit 5 and the two system output terminals 103 and 104. The output relay 6 is a function of opening and closing a connection path between the inverter circuit 5 and the commercial power grid 2.

  The grid-connected inverter device 3 further includes a plurality of current detectors 12a, 12b, 12c, and 12d, and a plurality of voltage detectors 13a, 13b, 13c, and 13d. The plurality of current detectors 12 a, 12 b, 12 c, 12 d, the plurality of voltage detectors 13 a, 13 b, 13 c, 13 d and the converter control unit 16 constitute a control unit 200 of the grid interconnection inverter device 3.

  Control unit 200 is used to drive a plurality of converter circuits 4. Specifically, control unit 200 generates a gate pulse command determined by MPPT (Maximum Power Point Tracking) control, which is maximum power tracking control that causes the operating points of the plurality of solar cell strings 1 to follow the maximum power point. . Alternatively, when the control unit 200 detects a short circuit failure of the diodes 11a, 11b, 11c, and 11d that form the plurality of converter circuits 4, the switching elements 10a, 10b, and 10c, which respectively configure the plurality of converter circuits 4. Gate pulse signals 17a1, 17b1, 17c1 and 17d1 which short 10d are generated.

  The switching elements 10a, 10b, 10c and 10d shown in FIG. 1 are IGBTs (Insulated Gate Bipolar Transistors), but may be transistors other than IGBTs. One example is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

  Moreover, although four converter circuits 4a, 4b, 4c, 4d are used in the grid interconnection inverter device 3, the number of converter circuits may be two or more. In the first embodiment, one example of converter circuits 4a, 4b, 4c, 4d is shown, but the configuration of the converter circuit is not limited to the illustrated example, and switching elements 10a, 10b, 10c, 10d and diodes 11a, 11b, 11c, Any other power conversion circuit may be used as long as it converts the DC voltage into a desired DC voltage value using 11 d.

  Although four solar cell strings 1a, 1b, 1c and 1d are connected to the grid-connected inverter device 3 in FIG. 1, the number of connected solar cell strings is not limited to the illustrated example, and two or more solar cell strings are connected. I hope there is. In this case, a number of converter circuits 4 corresponding to the number of solar cell strings are used in the solar power generation system 100.

  Hereinafter, the configuration of the control unit 200 will be specifically described.

  A current detection element 30a is disposed on the DC bus N on the negative side between the negative input terminal 102a and the converter circuit 4a. The current detection element 30a detects the current value at the position. A current transformer or a shunt resistor is used for the current detection element 30a.

  The current detector 12a is realized by an amplifier or a level shift circuit, and converts a voltage in direct proportion to the current detected by the current detection element 30a into a current detection voltage within a low voltage range that can be handled by the power computing device 14a Do. The current detection voltage corresponds to the current value Isa of the output current of the solar cell string 1a. The current value Isa output from the current detector 12 a is input to the converter control unit 16.

  One end of the voltage detector 13a is connected to the positive electrode input terminal 101a, one end of the reactor 9a, and one end of the smoothing capacitor 7a in the DC bus P on the positive electrode side. The other end of the voltage detector 13a is connected to the negative electrode input terminal 102a and the other end of the smoothing capacitor 7a in the DC bus N on the negative electrode side.

  The voltage detector 13a detects a voltage value Vsa which is an output voltage value of the solar cell string 1a. The voltage value Vsa output from the voltage detector 13 a is input to the converter control unit 16.

  A current detection element 30b is disposed on the DC bus N on the negative side between the negative electrode input terminal 102b and the converter circuit 4b. The current detection element 30b detects the current value at the position. A current transformer or a shunt resistor is used for the current detection element 30b.

  The current detector 12b is realized by an amplifier or a level shift circuit, and converts a voltage in direct proportion to the current detected by the current detection element 30b into a current detection voltage within a low voltage range that can be handled by the power computing device 14b. Do. The current detection voltage corresponds to the current value Isb of the output current of the solar cell string 1b. The current value Isb output from the current detector 12 b is input to the converter control unit 16.

  One end of the voltage detector 13b is connected to the positive electrode input terminal 101b, one end of the reactor 9b, and one end of the smoothing capacitor 7b in the DC bus P on the positive electrode side. The other end of the voltage detector 13b is connected to the negative electrode input terminal 102b and the other end of the smoothing capacitor 7b in the DC bus N on the negative electrode side. The voltage detector 13 b detects a voltage value Vsb that is an output voltage value of the solar cell string 1 b. The voltage value Vsb output from the voltage detector 13 b is input to the converter control unit 16.

  A current detection element 30c is disposed on the DC bus N on the negative side between the negative input terminal 102c and the converter circuit 4c. The current detection element 30c detects the current value at the position. A current transformer or a shunt resistor is used for the current detection element 30c.

  The current detector 12c is realized by an amplifier or a level shift circuit, and converts a voltage in direct proportion to the current detected by the current detection element 30c into a current detection voltage within a low voltage range that the power computing device 14c can handle. Do. This current detection voltage corresponds to the current value Isc of the output current of the solar cell string 1c. The current value Isc output from the current detector 12 c is input to the converter control unit 16.

  One end of the voltage detector 13c is connected to the positive electrode input terminal 101c, one end of the reactor 9c, and one end of the smoothing capacitor 7c in the DC bus P on the positive electrode side. The other end of the voltage detector 13c is connected to the negative electrode input terminal 102c and the other end of the smoothing capacitor 7c in the DC bus N on the negative electrode side. The voltage detector 13c detects a voltage value Vsc which is an output voltage value of the solar cell string 1c. The voltage value Vsc output from the voltage detector 13 c is input to the converter control unit 16.

  A current detection element 30d is disposed on the DC bus N on the negative side between the negative electrode input terminal 102d and the converter circuit 4d. The current detection element 30d detects the current value at the position. A current transformer or a shunt resistor is used for the current detection element 30d.

  The current detector 12d is realized by an amplifier or a level shift circuit, and converts a voltage in direct proportion to the current detected by the current detection element 30d into a current detection voltage within a low voltage range that can be handled by the power computing device 14d Do. The current detection voltage corresponds to the current value Isd of the output current of the solar cell string 1d. The current value Isd output from the current detector 12 d is input to the converter control unit 16.

  One end of the voltage detector 13d is connected to the positive electrode input terminal 101d, one end of the reactor 9d, and one end of the smoothing capacitor 7d in the DC bus P on the positive electrode side. The other end of the voltage detector 13d is connected to the negative electrode input terminal 102d and the other end of the smoothing capacitor 7d at the DC bus N on the negative electrode side. The voltage detector 13d detects a voltage value Vsd which is an output voltage value of the solar cell string 1d. The voltage value Vsd output from the voltage detector 13 d is input to the converter control unit 16.

  Converter control unit 16 generates gate pulse command Gs for operating converter circuits 4 based on the plurality of current values Isa, Isb, Isc, Isd and the plurality of voltage values Vsa, Vsb, Vsc, Vsd. Output to the plurality of gate pulse generators 17.

  Specifically, converter control unit 16 determines whether any one of diodes 11a, 11b, 11c and 11d constituting each of the plurality of converter circuits 4 has a short circuit failure, ie, diodes 11a, 11b, 11c and 11d. The presence or absence of any short circuit failure is determined. Further, converter control unit 16 generates a first gate pulse command 21 a that causes the plurality of converter circuits 4 to operate at the maximum power point of the plurality of solar cell strings 1. Then, converter control unit 16 selects and selects one of first gate pulse command 21a and second gate pulse command 22a that shorts all switching elements of converter circuits 4 when a short circuit failure occurs. The first gate pulse command 21a or the second gate pulse command 22a is output to the plurality of gate pulse generators 17 as a gate pulse command Gs.

  Next, the configuration of converter control unit 16 will be described in detail.

  FIG. 2 is a block diagram of converter control unit 16 shown in FIG. The converter control unit 16 shown in FIG. 2 includes a short circuit fault detection unit 20, an MPPT control unit 21, and a gate pulse command generation unit 22.

  The short circuit fault detection unit 20 receives the current values Isa, Isb, Isc and Isd detected by the plurality of current detectors 12a, 12b, 12c and 12d, and converts the plurality of converter circuits based on the current values Isa, Isb, Isc and Isd. It is determined whether there is a short circuit failure in any of the diodes 11a, 11b, 11c and 11d that constitute each of the four.

  When the diodes 11a, 11b, 11c, and 11d constituting each of the plurality of converter circuits 4 are normal without short circuit failure, the current values Isa, Isb, Isc, and Isd ≧ 0. On the other hand, when any of the diodes 11a, 11b, 11c and 11d constituting each of the plurality of converter circuits 4 has a short circuit failure, the current value becomes a value smaller than zero. When the diode 11d has a short circuit failure, a reverse current flows in the solar cell string 1d connected to the converter circuit 4d, so the current value detected by the current detector 12d is Isd <0.

  That is, the short circuit fault detection unit 20 determines that no short circuit fault has occurred in any of the diodes 11a, 11b, 11c and 11d based on the following equation (1), and based on the following equation (2), the diodes 11a, 11b, It is determined that a short circuit failure has occurred in either of 11c and 11d. Then, the short circuit fault detection unit 20 outputs the determination result 20a indicating the presence or absence of the short circuit fault to the gate pulse command generation unit 22.

Isa ≧ 0, Isb ≧ 0, Isc ≧ 0 and Isd ≧ 0 (1)
Isa <0, Isb <0, Isc <0 or Isd <0 (2)

  In Patent Document 1 described above, the short circuit fault is detected when the input DC voltage rises to the same value as the output voltage of the converter circuit. However, when the solar cell is connected as a DC power supply, the input DC voltage may be the same value as the output voltage of the converter circuit depending on the number of connected solar cells even if the diode does not have a short circuit failure. For this reason, there is a possibility that the short circuit fault of the diode is erroneously detected in comparison between the input DC voltage and the output voltage of the converter circuit.

  In order to prevent such erroneous detection of a short circuit failure, converter control unit 16 of grid-connected inverter device 3 according to the first embodiment is directed to the direction of the current flowing between the solar cell and grid-connected inverter device 3. It is comprised so that the presence or absence of a short circuit failure may be determined.

  The MPPT control unit 21 controls the current values Isa, Isb, Isc, Isd detected by the plurality of current detectors 12a, 12b, 12c, 12d and the voltages detected by the plurality of voltage detectors 13a, 13b, 13c, 13d. The values Vsa, Vsb, Vsc, and Vsd are input, and the first gate pulse command 21a determined by the MPPT control is generated and output to the gate pulse command generation unit 22.

  MPPT control for detecting the maximum power point of a solar cell string is generally implemented by a well-known hill climbing method. In addition, since various methods are proposed for MPPT control, it may be implemented by control other than the hill climbing method. Since the output characteristics of the solar cell have the maximum power point, the hill climbing method estimates the direction of the maximum point by increasing and decreasing the power of the solar cell, and detects the maximum point by changing the voltage and current little by little. is there.

  The gate pulse command generation unit 22 inputs the determination result 20a indicating the presence or absence of the short circuit failure output from the short circuit failure detection unit 20 and the first gate pulse command 21a output from the MPPT control unit 21 and the determination result Based on 20a, the presence or absence of a short circuit failure is determined. Then, the gate pulse command generation unit 22 outputs the first gate pulse command 21a described above as the gate pulse command Gs to the gate pulse generators 17a, 17b, 17c, 17d or the gate according to the determination result of the short circuit failure. The second gate pulse command 22a generated by the pulse command generator 22 is generated and output to the gate pulse generators 17a, 17b, 17c and 17d as a gate pulse command Gs.

  Specifically, gate pulse command generation unit 22 that has determined that short circuit failure has not occurred according to determination result 20a generates gate pulse using first gate pulse command 21a output from MPPT control unit 21 as gate pulse command Gs. The signals are output to the units 17a, 17b, 17c and 17d. The gate pulse command generation unit 22 that has determined that a short circuit failure has occurred based on the determination result 20a generates a second gate pulse command 22a that shorts all the switching elements 10a, 10b, 10c and 10d of the plurality of converter circuits 4. Then, the second gate pulse command 22a is output to the gate pulse generators 17a, 17b, 17c and 17d as a gate pulse command Gs.

  The configuration of converter control unit 16 will be described in more detail.

  When the diode has a short circuit failure, the reverse current to the solar cell string can not be stopped even when the operation of all the switching elements 10a, 10b, 10c and 10d constituting each of the plurality of converter circuits 4 is stopped. Therefore, converter control unit 16 does not allow the reverse current to flow to the solar cell string connected to the converter circuit in which the diode has a short circuit failure, so that all switching elements 10a, 10b, 10c, By short-circuiting 10 d, the plurality of solar cell strings 1 are all shorted. This makes it possible to prevent the reverse current from flowing to the solar cell string connected to the shorted converter circuit of the diode.

  The operation of converter control unit 16 described above will be described using FIG.

  FIG. 3 is a flowchart relating to an operation at the time of determination of a diode short circuit failure by the converter control unit of the grid-connected inverter device according to Embodiment 1 of the present invention.

  (S1) The short circuit fault detection unit 20 receives the current values Isa, Isb, Isc, Isd detected by the plurality of current detectors 12a, 12b, 12c, 12d.

  (S2) The short circuit fault detection unit 20 determines whether or not the diode 11a of the converter circuit 4a has a short circuit fault according to the following equation (3).

  Isa 0 0 [A] (3)

  (S3) When the current value Isa satisfies the condition of the above equation (3) (S2, Yes), the short circuit fault detection unit 20 determines that the diode 11a of the converter circuit 4a is normal, and the determination result 20a is gate pulse commanded It is output to the generation unit 22.

  (S4) When the current value Isa does not satisfy the condition of the above equation (3) (S2, No), the short circuit failure detection unit 20 determines that the diode 11a of the converter circuit 4a has a short circuit failure and determines the determination result 20a. It is output to the gate pulse command generation unit 22.

(S5) The short circuit fault detection unit 20 determines whether or not the diode 11b of the converter circuit 4b has a short circuit fault according to the following equation (4).
Isb 0 0 [A] (4)

  (S6) When the current value Isb satisfies the condition of the above equation (4) (S5, Yes), the short-circuit failure detection unit 20 determines that the diode 11b of the converter circuit 4b is normal, and determines the determination result 20a as a gate pulse command It is output to the generation unit 22.

  (S7) If the current value Isb does not satisfy the condition of the above equation (4) (S5, No), the short circuit failure detection unit 20 determines that the diode 11b of the converter circuit 4b has a short circuit failure, and the determination result 20a is It is output to the gate pulse command generation unit 22.

  (S8) The short circuit fault detection unit 20 determines whether or not the diode 11c of the converter circuit 4c has a short circuit fault according to the following equation (5).

  Isc 0 0 [A] (5)

  (S9) If the current value Isc satisfies the condition of the above equation (5) (S8, Yes), the short circuit failure detection unit 20 determines that the diode 11c of the converter circuit 4c is normal, and the determination result 20a is gate pulse commanded It is output to the generation unit 22.

  (S10) If the current value Isc does not satisfy the condition of the above equation (5) (S8, No), the short circuit failure detection unit 20 determines that the diode 11c of the converter circuit 4c has a short circuit failure, and the determination result 20a is It is output to the gate pulse command generation unit 22.

  (S11) The short circuit fault detection unit 20 determines whether or not the diode 11d of the converter circuit 4d has a short circuit fault according to the following equation (6).

  Isd 0 0 [A] (6)

  (S12) When the current value Isd satisfies the condition of the above equation (6) (S11, Yes), the short-circuit failure detection unit 20 determines that the diode 11d of the converter circuit 4d is normal, and determines the determination result 20a as a gate pulse command It is output to the generation unit 22.

  (S13) When the current value Isd does not satisfy the condition of the above equation (6) (S11, No), the short circuit failure detection unit 20 determines that the diode 11d of the converter circuit 4d has a short circuit failure and determines the determination result 20a It is output to the gate pulse command generation unit 22.

  (S14) The MPPT control unit 21 computes the first gate pulse command 21a determined by the MPPT control.

  (S15) The gate pulse command generation unit 22 determines the presence or absence of a short circuit failure of the diode based on the determination result 20a output from the short circuit failure detection unit 20 in S2 to S12.

  (S16) If there is a short circuit failure in the diode (S15, Yes), gate pulse command generation unit 22 generates a second gate pulse command that is a switching element short circuit command to short all switching elements 10a, 10b, 10c, 10d. 22a is generated and output to each of the plurality of gate pulse generators 17a, 17b, 17c, 17d as a gate pulse command Gs.

  (S17) If the diode does not have a short circuit failure (S15, No), the gate pulse command generation unit 22 selects the first gate pulse command 21a calculated in S14, and generates a plurality of gate pulses as a gate pulse command Gs. Output to each of the devices 17a, 17b, 17c, 17d.

  (S18) The plurality of gate pulse generators 17a, 17b, 17c, 17d generate gate pulse signals 17a1, 17b1, 17c1, 17d1 corresponding to the type of the received gate pulse command Gs. That is, in the case of the gate pulse command Gs corresponding to the first gate pulse command 21a, gate pulse signals 17a1, 17b1, 17c1 and 17d1 are generated to boost the voltage output from the solar cell string 1a. In the case of the gate pulse command Gs corresponding to the second gate pulse command 22a, gate pulse signals 17a1, 17b1, 17c1 and 17d1 for shorting all the switching elements 10a, 10b, 10c and 10d are generated.

  In the following, the operation of the grid-connected inverter device 3 will be described using specific numerical values. In addition, the numerical value demonstrated below is an example, and the numerical value used by operation | movement of the grid connection inverter apparatus 3 is not limited to these.

In the present embodiment, a case where the diode 11d of the converter circuit 4d is broken will be described as an example. Specific numerical values are as shown in the following equations (7) to (11).
Vsa, Vsb, Vsc = 300 [V] (7)
Vsd = 100 [V] (8)
Isa, Isb, Isc = 5 [A] (9)
Isd = −30 [A] (10)
Short-circuit current of solar cell string = 10 [A] (11)

  The operation of converter control unit 16 will be described according to the flowchart shown in FIG.

  In S1 to S13, the input current value has a relationship of Isa ≧ 0, Isb ≧ 0, Isc ≧ 0, Isd <0, and in S14, the MPPT control unit 21 calculates the first gate pulse command 21a. However, in S15, the gate pulse command generation unit 22 outputs, as a gate pulse command Gs, a second gate pulse command 22a that shorts all the switching elements 10a, 10b, 10c, and 10d of the plurality of converter circuits 4.

  As described above, the grid-connected inverter device 3 according to the first embodiment determines whether or not the diodes 11a, 11b, 11c, and 11d of the converter circuits 4a, 4b, 4c, and 4d have a short circuit failure. If the diode does not have a short circuit failure, the gate pulse command of the converter circuit according to the control command of the MPPT control unit 21 is output. If the diode has a short circuit failure, the gate pulse command to short the switching elements of the converter circuit It is configured to output. As in the prior art shown in Patent Document 1, it is not possible to prevent the reverse current to the solar cell just by stopping the operation of the converter circuit, and there is a possibility of causing the performance deterioration or breakage of the solar cell. According to the grid-connected inverter device 3 of the first embodiment, the short circuit failure of the diode is detected, and all switching elements of the converter circuit are shorted, thereby preventing the reverse current to the solar cell and the performance deterioration of the solar cell Or you can prevent damage.

Second Embodiment
The grid-connected inverter device 3 according to the first embodiment shorts all the switching elements of the converter circuit when the diode detects a short circuit fault, all the plurality of solar cell strings 1 are short circuited, and the diode is a short circuit fault The reverse current does not flow in the solar cell string connected to the converter circuit. The grid-connected inverter device 3 according to the second embodiment short-circuits a solar cell string connected to the converter circuit by short-circuiting a switching element forming a converter circuit including a short-circuited diode, thereby causing a short-circuit failure. The solar cell string connected to the converter circuit having a diode that is not connected is configured not to flow a reverse current. The configuration of the grid-connected inverter device 3 according to the second embodiment is the same as that of the grid-connected inverter device 3 according to the first embodiment except for the operation of the converter control unit 16, and therefore the description thereof is omitted.

  FIG. 4 is a flowchart relating to an operation at the time of determination of a diode short circuit failure by the converter control unit of the grid-connected inverter device according to Embodiment 2 of the present invention. The difference from the flowchart shown in FIG. 3 is that the processes of S16 and S18 are replaced with the processes of S26 and S28. In the second embodiment, among the plurality of converter circuits 4a, 4b, 4c, 4d, a short circuit failure occurs in the diode 11a that constitutes the converter circuit 4a, and the diodes 11b, 11c, which constitute the converter circuits 4b, 4c, 4d. It is assumed that no short circuit failure occurs in 11 d.

  (S26) If there is a short circuit failure in the diode 11a (S15, Yes), the gate pulse command generation unit 22 generates a second gate pulse command 22a that is a switching element short circuit command to short the switching element 10a. It outputs to the gate pulse generator 17a as the command Gs.

  (S28) The gate pulse generator 17a that has received the gate pulse command Gs generates a gate pulse signal 17a1 that shorts the switching element 10a.

  Due to the generation of the gate pulse signal 17a1, the solar cell string 1a connected to the converter circuit 4a including the short-circuited diode 11a is short-circuited. Furthermore, the current outputted from the solar cell strings 1b, 1c and 1d connected to the converter circuits 4b, 4c and 4d having normal diodes flows to the switching element 10a constituting the converter circuit 4a having a short circuited diode 11a. Therefore, no reverse current flows in the solar cell strings 1b, 1c, 1d. Therefore, performance degradation or damage of the solar cell can be prevented. In addition, according to the grid-connected inverter device 3 according to the second embodiment, only the switching element that constitutes the converter circuit including at least the shorted diode is short-circuited. Therefore, the converter control unit is compared to the first embodiment. The generation operation of the gate pulse command Gs by 16 can be simplified.

  In addition, although it is set as the structure which shorts only the switching element of the converter circuit provided with the short circuit failure diode according to the grid connection inverter apparatus 3 which concerns on Embodiment 2, the switching element to short-circuit is a switching circuit of the converter circuit provided with the short circuit failure diode. The same effect can be obtained by including one or more switching elements of the converter circuit including a diode that is not short-circuited, as long as the elements are included.

Third Embodiment
In the grid-connected inverter device 3 according to the first embodiment, the drive power of the devices constituting the grid-connected inverter device 3 is generated by the power supplied from the commercial power grid 2. However, when the DC power source connected to the grid-connected inverter device 3 is the solar cell string 1, the power supplied from the solar cell string 1 generates drive power of the devices constituting the grid-connected inverter device 3. Is common. When the grid-connected inverter device 3 according to the first embodiment is configured to generate the drive power by the power supplied from the solar cell string 1, the grid-connected inverter device 3 according to the first embodiment Then, when all the switching elements 10a, 10b, 10c and 10d of the plurality of converter circuits 4 are shorted, each of the plurality of solar cell strings 1 is in the shorted state. Therefore, the electric power generated by the plurality of solar cell strings 1 can not be supplied to the grid-connected inverter device 3, and the switching elements 10a, 10b, 10c, and 10d of the plurality of converter circuits 4 are turned off. Therefore, in the configuration in which the grid-connected inverter device 3 according to the third embodiment generates the drive power from the power generated by the plurality of solar cell strings 1, the reverse current is prevented by the operation described below. The configuration of the grid-connected inverter device 3 according to the third embodiment is the same as that of the grid-connected inverter device 3 according to the first embodiment except for the operation of the converter control unit 16, and therefore the description thereof is omitted.

  FIG. 5 is a flowchart relating to an operation at the time of determination of a diode short circuit failure by a converter control unit of a grid-connected inverter device according to a third embodiment of the present invention. The difference from the flowchart shown in FIG. 3 is that the processes of S16 and S18 are replaced with the processes of S36 and S28. In the third embodiment, among the plurality of converter circuits 4a, 4b, 4c, 4d, a short circuit failure occurs in the diode 11a that constitutes the converter circuit 4a, and the diodes 11b, 11c, which constitute the converter circuits 4b, 4c, 4d. It is assumed that no short circuit failure occurs in 11 d.

  (S36) When diode 11a has a short circuit failure (S15, Yes), gate pulse command generation unit 22 is a switching element forming converter circuits 4b, 4c, 4d including diodes 11b, 11c, 11d not having a short circuit failure. A second gate pulse command 22a, which is a switching element short circuit command for shorting 10b, 10c, 10d, is generated and output as a gate pulse command Gs to each of the gate pulse generators 17b, 17c, 17d.

  (S38) Each of the gate pulse generators 17b, 17c and 17d that has received the gate pulse command Gs generates and outputs a gate pulse signal corresponding to the type of the received gate pulse command Gs. That is, in the case of the gate pulse command Gs corresponding to the first gate pulse command 21a, gate pulse signals 17b1, 17c1, 17d1 for boosting the voltages output from the solar cell strings 1b, 1c, 1d are output. In the case of the gate pulse command Gs corresponding to the second gate pulse command 22a, a gate pulse signal 17a1 is generated which shorts the switching elements 10b, 10c and 10d.

  The current output from the solar cell strings 1b, 1c, 1d connected to the converter circuits 4b, 4c, 4d provided with the diodes 11b, 11c, 11d not having a short circuit fault by short-circuiting the switching elements 10b, 10c, 10d. Flows through the switching elements 10b, 10c, and 10d that constitute the converter circuits 4b, 4c, and 4d including the diodes 11b, 11c, and 11d that do not have a short circuit failure, but are connected to the converter circuit 4a including the diode 11a that has a short circuit failure. No reverse current flows in the solar cell string 1a.

  Since the solar cell string 1a is short-circuited by the short circuit failure of the diode 11a, the output voltage of the solar cell string 1a decreases, but since the diode 11a is normal, the current output from the solar cell string 1a is blocked Be done. Therefore, the reverse current to the solar cell string 1a is not generated, and the above-mentioned drive power can be generated by the power supplied from the solar cell string 1a.

  According to the grid-connected inverter device 3 according to the third embodiment, even when the components of the grid-connected inverter device 3 are driven by the power of the solar cell string, the short-circuited state of the switching element can be maintained. , It is possible to prevent the performance deterioration or damage of the solar cell.

  By using a MOSFET configured using silicon carbide (SiC) as switching elements 10a, 10b, 10c and 10d included in grid-connected inverter device 3 according to the first to third embodiments, the following can be realized. You can get the effect. Since a short circuit failure of the diode is detected and a current flows in the short-circuit controlled switching element, heat is generated due to the loss due to the ON resistance of the switching element. By using a MOSFET configured using silicon carbide as the switching elements 10a, 10b, 10c, and 10d, the ON resistance can be reduced, and heat generation can be suppressed. Further, since heat generation at the time of detection of a short circuit failure of the diode can be suppressed, the radiator (not shown) connected to each of the converter circuits 4a, 4b, 4c, 4d can be miniaturized, and the weight of the grid interconnection inverter device 3 It can be lightened.

  The configuration shown in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and one of the configurations is possible within the scope of the present invention. Parts can be omitted or changed.

  DESCRIPTION OF SYMBOLS 1a, 1b, 1c, 1d Solar cell string, 2 commercial power grid, 3 grid interconnection inverter apparatus, 4a, 4b, 4c, 4d converter circuit, 5 inverter circuit, 6 output relay, 7a, 7b, 7c, 7d, 8 Smoothing capacitor 9a, 9b, 9c, 9d Reactor, 10a, 10b, 10c, 10d switching element, 11a, 11b, 11c, 11d diode, 12a, 12b, 12c, 12d current detector, 13a, 13b, 13c, 13d Voltage detector, 16 converter control unit, 17a, 17b, 17c, 17d gate pulse generator, 17a1, 17b1, 17c1, 17d1 gate pulse signal, 20 short circuit fault detection unit, 20a judgment result, 21 MPPT control unit, 21a first Gate pulse command, 22 gate pulse command Generation unit, 22a second gate pulse command, 30a, 30b, 30c, 30d current detection element, 100 photovoltaic system, 101a, 101b, 101c, 101d positive input terminal, 102a, 102b, 102c, 102d negative input terminal, 103, 104 system output terminals, 200 control unit.

Claims (2)

A plurality of converter circuits into which electric power output from each of a plurality of solar cells is input; an inverter circuit converting a DC voltage output from each of the plurality of converter circuits into an AC voltage; A short circuit fault detection unit for detecting a short circuit fault of a diode constituting each, and for controlling a switching element constituting each of the plurality of converter circuits when the short circuit fault detection unit detects a short circuit fault of the diode A gate pulse command generation unit for outputting a gate pulse command, wherein each of the plurality of converter circuits boosts a direct current voltage input from each of the plurality of solar cells by a reactor, a switching element, and a diode Converter circuit that forms the The power a system interconnection inverter device for generating a driving power of the devices constituting the system interconnection inverter device,
When the short circuit fault detection unit detects a diode short circuit fault,
The gate pulse command generation unit is configured to stop the operation of the switching element forming the converter circuit including the shorted diode and to short the switching element forming the converter circuit including the diode not shorted. A grid interconnection inverter device characterized by outputting a gate pulse command of The grid-connected inverter device according to claim 1, wherein a MOSFET configured using silicon carbide is used as the switching element.

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