JP2009011043A - Fault detection device for chopper circuit - Google Patents

Abstract

A fault detection device for a chopper circuit capable of detecting when a fault has occurred in at least one of elements connected in parallel with semiconductor switching elements driven by one gate drive circuit and preventing the damage from spreading. It is to provide.
In a chopper circuit 3 connected to a main circuit of a power conversion device and connecting a plurality of IGBT elements 11 to 14 in parallel, a gate control unit 20 for generating a gate signal for controlling on / off of the elements 11 to 14 The gate drive circuit 30 for supplying the gate signals to all the IGBT elements 11 to 14 connected in parallel, and the on / off states of the elements 11 to 14 are compared with the magnitude of the gate-emitter voltage and the reference voltage. A comparison circuit 45 that determines an on state when the magnitude of the voltage between the emitters is larger than the reference voltage, and an off state otherwise, and a first failure determination unit 26 that determines a failure based on the presence or absence of a feedback signal It is equipped with.
[Selection] Figure 1

Description

The present invention relates to a power conversion device provided with a chopper circuit composed of semiconductor switching elements, and to a device for detecting a failure of the chopper circuit.

As a conventional failure detection method of a power conversion device configured using a semiconductor-switching element, for example, a voltage-driven self-extinguishing element such as an IGBT element, for example, a gate signal applied to the semiconductor switching element from a gate drive circuit and the element There is a mismatch detection device that compares a feedback signal that feeds back this state to the gate drive circuit and discriminates an abnormality when the two do not match (Patent Document 1).

However, in the conventional failure detection apparatus using the mismatch detection circuit, failure detection is possible when there is one IGBT element and one gate drive circuit, that is, one parallel configuration, but a plurality of IGBT elements are the main circuit. In the case of the parallel configuration, a plurality of gate drive circuits for receiving the feedback signal are required, resulting in a problem that the power conversion device is enlarged.
JP 11-356035 A

The present invention improves the above-described problems, and detects a failure of an element even when a failure occurs in at least one of the elements in which semiconductor switching elements driven by one gate drive circuit are connected in parallel. By performing the protection operation, the current balance between the parallel elements is disrupted, and an excessive current flows through the faulty element or other healthy elements, preventing avalanche faults from occurring and preventing damage from spreading. A failure detection apparatus is provided.

A failure detection device for a chopper circuit according to claim 1 of the present invention is a chopper circuit that is connected to a main circuit of a power conversion device and is configured by connecting a plurality of semiconductor switching elements in parallel. Gate control means for generating a gate signal for controlling off, gate drive means for supplying all the semiconductor switching elements connected in parallel to the gate signal, and on / off states of all the semiconductor switching elements connected in parallel, A comparison means for comparing the magnitude of the gate-emitter voltage with a reference voltage, determining that the gate-emitter voltage is larger than the reference voltage, and determining the on-state; otherwise, determining the off-state. When a gate-on signal is given to all the semiconductor switching elements connected in parallel, the plurality of elements are all turned on. In the case of the first failure determination means, it is determined as normal by outputting a feedback signal from the comparison means, and a failure is determined by not outputting a feedback signal when at least one of the plurality of elements is not in an ON state. It is characterized by comprising.

According to a second aspect of the present invention, there is provided the chopper circuit failure detection device according to the first aspect, further comprising voltage detection means for detecting a collector-emitter voltage of a plurality of semiconductor switching elements connected in parallel to the main circuit, When a gate-off signal is applied to all the semiconductor switching elements connected in parallel, when all of the plurality of elements are in an off state, it is determined that a potential difference occurs in the voltage detection circuit, and the normal state is determined. When at least one of the voltage detection circuits is not in an OFF state, the voltage detection circuit includes a second failure determination means for determining a failure by indicating a potential difference of zero or a value close thereto.

A failure detection device for a chopper circuit according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the semiconductor switching element is formed of an IGBT element or a GTO element.

According to the chopper circuit failure detection apparatus of the first aspect of the present invention, when an on-gate signal is applied to the semiconductor switching elements having a parallel configuration in the mode in which the energy of the direct current accumulated in the series reactor is maintained, When a failure occurs in at least one of the parallel devices driven by one gate drive circuit, the feedback signal is compared to detect the failure of the device and perform an appropriate protection operation, thereby providing a current between the parallel devices. It is possible to prevent the damage from spreading due to an avalanche failure caused by an excessive current flowing through the failure element or other healthy elements due to an imbalance.

According to the failure detection device for a chopper circuit according to claim 2, when an off-gate signal is given to a semiconductor switching element having a parallel configuration in a mode in which the energy of the DC current accumulated in the series reactor is output to the load, When a failure occurs in at least one of the parallel elements driven by the gate drive circuit, the failure of the element is monitored by monitoring the voltage value of the voltage detection circuit connected in parallel with the collector-emitter of the semiconductor switching element. By detecting and performing an appropriate protection operation, it is possible to prevent an excessive current from flowing through the failure element to cause an open failure or breakage, thereby preventing damage from spreading.

According to the chopper circuit failure detection apparatus of the third aspect, since the semiconductor switching element is formed of the IGBT element or the GTO element, the reliability can be improved.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 shows a chopper configuration in which an IGBT element is used as a semiconductor switching element and a series reactor is connected to a DC voltage source.

In FIG. 1, 1 is a DC power source, 2 is a series reactor, 3 is a chopper circuit, 4 is a DC capacitor connected between DC output terminals of the chopper circuit 3, and 5 is connected between DC output terminals of the chopper circuit 3. A DC load, 8 is a diode connected between the series reactor 2 and the DC load 5, and 11 to 14 operate as a closed switch in a mode in which the energy of the DC current is stored in the series reactor 2, and is stored in the series reactor 2. In the mode for outputting the energy of the direct current, the IGBT 11 is a semiconductor switching element connected in parallel and operates as a chopper. The elements 11 to 14 and the diode 8 constitute the chopper circuit 3.

A voltage detection circuit 15 is connected in parallel with the collector-emitter of the IGBT elements 11 to 14, and a second failure determination unit 18 is further connected thereto. Further, a gate control unit 20 serving as a gate control unit that applies a gate signal to the IGBT elements 11 to 14 and a gate drive circuit 30 serving as a gate drive unit are provided.

The gate controller 20 includes a gate signal generation circuit 25, a light emitter 21 connected thereto, and a light receiver 22 that receives a gate signal from the gate signal generation circuit 25 and a signal from the gate drive circuit 30. The first failure determination unit 26 is provided.

Further, signal transmission is performed between the light emitter 21 of the gate controller 20 and the light receiver 31 of the gate drive circuit 30 and between the light emitter 32 of the gate drive circuit 30 and the light receiver 22 of the gate controller 20. Are connected by optical transmission cables 23 and 24.

The gate drive circuit 30 is connected to a light receiver 31 with a gate pulse amplifier circuit 33, which is connected to gate drive signal output terminals G and E via gate resistors 34-37. The gate drive signal output from here is connected to the gate terminal G and the emitter terminal E of the IGBT elements 11 to 14 of the chopper circuit 3 through electric cables 51 to 54.

Further, the gate drive circuit 30 is provided with a comparison circuit 45, and comparators 38 to 41 are connected between the threshold voltage set value 42 and the gate signal output terminal GE. . The comparators 38 to 41 compare the voltage between the gate signal output terminals GE and the threshold voltage, and output “1” when the voltage between GE is high, and “0” when low. Is output. Further, the comparators 38 to 41 are connected to the light emitter 32 through an AND gate 43.

Next, the operation of the chopper circuit failure detection apparatus configured as described above will be described. A loop 16 in FIG. 1 shows a current path in a mode in which the energy of the direct current accumulated in the series reactor 2 is held. When the parallel-configured IGBT elements 11 to 14 are in the ON state, a current is passed between the parallel elements. It shall be evenly balanced.

In the gate control unit 20, an on-gate signal is generated by the gate signal generation circuit 25, and this is converted into an optical signal by the light emitter 21 to emit light, and is again electrically transmitted by the light receiver 31 of the gate drive circuit 30 through the optical transmission cable 23. Converted to a signal. This signal is amplified by the gate pulse amplifier circuit 33, and an on-gate voltage is simultaneously applied from the gate signal output terminal GE to each IGBT element 11-14 of the chopper circuit 3.

At this time, an on-gate voltage higher than the threshold voltage required to turn on the IGBT elements 11 to 14 is applied between the gate signal output terminals GE of the gate drive circuit 30, but the comparators 38 to 41. When the GE voltage is compared with the threshold voltage from the threshold voltage setting value 42 and the GE voltage is high, each of the comparators 38 to 41 outputs "1". Is sent to the AND gate 43, and the output from the AND gate 43 is “1”, causing the light emitter 32 to emit light. This optical signal is sent to the light receiver 22 of the gate controller 20 via the optical transmission cable 24, where it is converted into an electrical signal and received as a feedback signal.

As a result, the first failure determination unit 26 of the gate control unit 20 receives a feedback signal indicating that each of the IGBT elements 11 to 14 is on as a result of giving the on-gate command signal. Determine.

Normally, a high impedance state is maintained between the gate and emitter of the IGBT elements 11 to 14 in a normal state, but on-gate to each IGBT element 11 to 14 of the parallel element at the same time in a state where a short circuit failure or the like has occurred. When the command is given, the impedance between the gate and the emitter is short-circuited or lowered to about several ohms, the voltage drop due to the gate resistors 34 to 37 becomes large, and a normal on-gate voltage cannot be applied.

When such a failure state occurs in at least one of the IGBT elements 11 to 14, the voltage between the gate drive signal output terminals GE becomes lower than the threshold voltage setting value 42. At least one of 38 to 41 outputs “0”, and the AND gate 43 outputs “0”.

As a result, the first failure determination unit 26 of the gate control unit 20 receives the output signal “0” in which at least one of the IGBT elements 11 to 14 is not in the on state even though the on gate signal is given. At least one of the elements 11 to 14 can be determined as a failure. When it is determined that a failure has occurred in this way, an appropriate OFF signal is output to all the IGBT elements 11 to 14 to stop the chopper circuit and perform an appropriate protective operation such as consuming the energy accumulated in the series reactor 2 with a resistor. Do.

As described above, when an on-gate signal is given to the IGBT elements 11 to 14 in parallel configuration in the mode in which the energy of the direct current accumulated in the series reactor 2 is held, at least of the parallel elements driven by one gate driving circuit. When a failure occurs in one element, the feedback signal is compared to detect the failure of the element, and by performing an appropriate protection operation, the current balance between the parallel elements is disrupted and the failed element or other healthy element It is possible to prevent an excessive current from flowing through the avalanche and causing an avalanche to cause damage.

Further, a loop 17 in FIG. 1 shows a current path in a mode in which the energy of the direct current accumulated in the series reactor 2 is output to the load, and the IGBT elements 11 to 14 configured in parallel operate as a chopper that repeatedly turns on and off. To do.

The gate signal generation circuit 25 of the gate control unit 20 generates an on-gate signal or an off-gate signal, which is converted into an optical signal by the light emitter 21 and emits light, and is received by the light receiver 31 of the gate drive circuit 30 via the optical transmission cable 23. It is converted again into an electrical signal. This signal is amplified by the gate pulse amplifier circuit 33, and an on-gate voltage or an off-gate voltage is simultaneously applied from the gate signal output terminal GE to each IGBT element 11-14 of the chopper circuit 3.

The IGBT elements 11 to 14 are repeatedly turned on and off. When an off-gate signal is given to the IGBT elements 11 to 14, the voltage detection circuit 15 connected in parallel with the collector-emitter is connected by the gate control unit 20. If the voltage value of the voltage detection circuit 15 indicates zero or a value close to this even though an off-gate command is given, at least one of the IGBT elements is in a short-circuit fault state, The second failure determination unit 18 determines this as a failure that does not enter the off state, and performs an appropriate protection operation.

Thus, in the mode in which the energy of the DC current accumulated in the series reactor 2 is output to the load, when an off-gate signal is given to the IGBT elements 11 to 14 in parallel configuration, the parallel element driven by one gate drive circuit When a failure occurs in at least one of the elements, the voltage value of the voltage detection circuit 15 connected in parallel with the collector-emitter of the IGBT elements 11 to 14 is monitored to detect the failure of the element. By performing the protective operation, it is possible to prevent an excessive current from flowing through the failure element, leading to an open failure or breakage, thereby preventing the spread of damage.

It is a circuit diagram which shows the failure detection apparatus of the chopper circuit of the power converter device by one Embodiment of this invention.

Explanation of symbols

1 DC power supply
2 series reactor
3 Chopper circuit
4 DC capacitor
5 DC load
8 Diode
11-14 IGBT element
15 Voltage detection circuit
16 Loop showing current path
17 Loop showing current path
18 Second failure determination unit
20 Gate controller
21 Light emitter
22 Receiver
23 Optical transmission cable
24 Optical transmission cable
25 Gate signal generation circuit
26 First failure determination unit
30 Gate drive circuit
31 Receiver
32 Light emitter
33 Gate pulse amplifier
34-37 Gate resistance
38-41 comparator
42 Threshold voltage setting value
43 AND Gate
45 Comparison circuit
51-54 Electric cable

Claims (3)

  In a chopper circuit connected to a main circuit of a power conversion device and configured by connecting a plurality of semiconductor switching elements in parallel, gate control means for generating a gate signal for controlling on / off of the semiconductor switching elements, and the gate The gate driving means for applying signals to all the semiconductor switching elements connected in parallel, the on / off states of all the semiconductor switching elements connected in parallel, the magnitude of the gate-emitter voltage and the reference voltage are compared, and the gate When the magnitude of the voltage between the emitters is larger than the reference voltage, it is determined to be in the on state, otherwise it is determined to be in the off state, and when the gate on signal is given to all the semiconductor switching elements connected in parallel When the plurality of elements are all on, a feedback signal is output from the comparison means. A failure of a chopper circuit, comprising: a first failure determination means for determining a failure by not outputting a feedback signal when at least one of the plurality of elements is not in an ON state. Detection device.   2. The failure detection device for a chopper circuit according to claim 1, further comprising a voltage detection means for detecting a collector-emitter voltage of a plurality of semiconductor switching elements connected in parallel to the main circuit, wherein all of the semiconductor switching elements connected in parallel with gate-off signals. When the plurality of elements are all in the off state, it is determined that the voltage detection circuit is normal by generating a potential difference, and when at least one of the plurality of elements is not in the off state, the voltage detection circuit A failure detection device for a chopper circuit, comprising: a second failure determination means for determining a failure by indicating that the potential difference between the first and second potentials is zero or a value close thereto.   3. The chopper circuit failure detection device according to claim 1, wherein the semiconductor switching element is formed of an IGBT element or a GTO element.