JPH0732531B2 - Power converter failure detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention is a bipolar mode FET (hereinafter referred to as BIFET).
(GE product name IGT) and FET are related to the failure detection circuit of the power converter consisting of a bridge circuit composed of static induction type self-extinguishing elements.

(Prior Art) An example of a conventional inverter circuit is shown in FIG. The AC power supply 1 is converted into direct current by the rectifier 2 including the diodes 21 to 26, and the voltage smoothed by the capacitor 3 is converted into the AC voltage by the inverter bridge 4 including the electric valves 41 to 46 in which the BIFET and the diode are connected in anti-parallel. Load terminal U,
Supply to V and W. In the operation of the inverter, the signal generated by the pulse width modulation control (hereinafter, PWM control) circuit 5 drives the BIFET of the inverter bridge 4 via the AND circuit 6 and the gate drive circuit 7, respectively. When the output voltage and the output frequency of the inverter bridge 4 are simultaneously controlled by the PWM control circuit 5, recently, a method of generating a PWM signal using a microprocessor is often adopted. The PWM signal is passed by the AND circuit 6 to the gate drive circuit 7 only when no failure occurs, so that the gate drive circuit 7 turns on / off the electric valves 41 to 46 of the inverter bridge 4. The current detector 8 connected to the DC bus of the inverter bridge 4 detects the current, and the overcurrent detector 9
Accordingly, when an overcurrent flows, all the electric valves of the inverter bridge 4 are turned off and the fault current of the inverter bridge is cut off by the condition input of the AND circuit 6.

On the other hand, when the ground current is detected by the zero-phase current transformer 10 and the ground fault is detected by the ground fault detector 11, the input condition of the AND circuit 6 is turned off and the electric valve of the inverter bridge 4 is turned off to ground. Cut off the current.

(Problems to be Solved by the Invention) In this conventional method, when the output terminal W phase in FIG. 3 is grounded and the R phase of the AC power supply 1 is positive with respect to the ground, the ground current is a diode. In some cases, the current flows in the circuit of 21 → electric valve 45 → ground of W phase and does not flow in the current detector 8. Therefore, the zero-phase current transformer 10 and the ground fault detector 11 are separately provided to protect against a ground fault.

As described above, conventionally, in addition to the overcurrent protection circuit, a ground protection circuit article has been required, and the number of circuits is large, which is an obstacle to miniaturization.

The present invention provides a fault detection circuit for a power converter that determines and protects a ground fault by adding a few economical logic elements without the need for special ground protection equipment.

[Structure of Invention]

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a failure detection device for a power converter in which electrostatic induction type self-extinguishing elements are bridge-connected. Collector of the extinguishing element
A detection circuit that outputs a failure detection signal when the voltage between the emitters exceeds a predetermined value and there is a drive signal applied between the gate and the emitter, and a failure signal of the element group connected to the positive side of the DC side of the bridge. And a failure signal of an element group connected to the negative side of the bridge on the DC side, and when the logical product of the failure signals of these two groups is established, a short-circuit failure on the load side of the bridge or a failure on the bridge. When the logical sum of the failure signals of the two groups is established, a failure detecting device is configured by providing a logical operation means for determining a ground failure (or a short circuit failure of the element).

(Operation) In the above configuration, when a short circuit occurs on the load side, a short-circuit current flows through the positive and negative electrostatic induction type self-extinguishing elements of the bridge in the short-circuit route, and the logical product is established to cause a short-circuit failure. It is determined that the bridge has failed.

When a grounding accident occurs on the load side, a ground current flows through the grounding point to the positive and negative side static induction self-extinguishing elements of the bridge, but the positive side and negative side of the element turn on at the same time. Therefore, the logical product is not established, and it is determined that there is a ground fault or a short-circuit fault of the element.

(Example) FIG. 1 shows an example of the present invention. The same parts as those in FIG. 3 are denoted by the same reference numerals and the description thereof will be omitted.

The gate drive circuit 7 sends a gate drive signal to the electric valves 41 to 46 of the inverter bridge 4 via the abnormality detection circuits 12 to 17. The abnormality detection circuits 12 to 17 output a detection signal based on the collector voltage of the BIFET of each electric valve and the gate drive signal when the gate drive signal is in the ON state and the collector voltage is higher than the set value. The detection signal is sent to the delay circuits 18 and 19,
When the detection signal continues for a certain period of time or more, 19 determines that it is abnormal and outputs a signal. The outputs of the delay circuits 18 and 19 are OR circuits 30 and 31.
Is input to the upper BIFET group and the lower BIFET group of the inverter bridge 4, and the abnormality is detected.
Outputs a failure detection signal A for detecting any abnormality in BIFET.

On the other hand, the outputs of the OR circuits 30 and 31 are input to the AND circuit 33,
It is detected that both the upper BIFET group and the lower BIFET group are abnormal, and this signal C is output as an overcurrent fault.

The output of the AND circuit 33 is passed through a knot circuit 34 and the output of the OR circuit 32 and the AND circuit 35 are ANDed to output a signal B.
This signal B is output when either the upper BIFET group or the lower BIFET group is abnormal, and in this case, it is generally a ground fault. However, the B signal is output even when one of the BIFETs in Shimogori has a short-circuit fault, but the short-circuit fault rarely occurs from the beginning, and a short-circuit fault may occur when the overcurrent state continues for a certain period of time. In general, the probability of ground fault is extremely high when the B signal is output.

A specific example of the abnormality detection circuits 12 to 17 is shown in FIG.

The drive signal e _i applies the voltage of the DC power supply 51 to the gate of the BIFET 44 via the amplifier composed of the resistor 52 and the transistors 58 and 59 to turn on the BIFET. On the other hand, the collector voltage of BIFET is detected by the resistor 60 and the Zener diode 56, and when the collector voltage is higher than a predetermined set value determined by the Zener voltage etc., the transistor 55 is turned on and the drive signal e _{i is set} to the resistors 52, 53.
The voltage is divided by to suppress the overcurrent value of the BIFET 44, and at the same time, the light emitting diode of the photocoupler 54 is driven and the transistor 63 on the photocoupler light receiving side is turned on to output the output e _o as an abnormal signal. The resistor 57 prevents the base of the transistor 55 from opening, and
62 is a pull-up resistor. In this circuit, the photocoupler 54 has a condition that a current flows only when the drive signal e _i is “1”, and the abnormality detection signal is not output when the drive signal e _i is “0”.

In the normal ON state, the collector voltage of the BIFET 44 drops to several V or less, but in the overcurrent state, the collector voltage of the BIFET 44 rapidly rises to several tens of V or more, and this state is detected as an abnormality.

(For details of these, Japanese Patent Application No. 60-23334 filed earlier.
See Japanese Patent Application No. 60-92870. ) In the circuit of FIG. 1, considering a load side short circuit accident, for example, when terminals V and W are short-circuited, the voltage of capacitor 3 is divided by BIFET 43 and 42 at the moment when BIFET 43 and 42 are turned on. The abnormality detection circuits 16 and 14 of BIFETs 43 and 42 output the abnormality detection signals to the delay circuits 18 and 19, and this state is maintained for a certain time (10 μm
If it continues for more than about S), the OR circuits 30 and 31 operate to output the signals A and C, and the signal C is judged to be an overcurrent fault.

Next, considering the case where the W phase is grounded, the voltage of the power supply 1 is applied to the BIFET 42 at the moment when the BIFET 42 is turned on, through the ground circuit (BIFET 42 → the circuits of diodes 22, 24 and 26), and B
When an overcurrent flows through the IFET 42, the collector voltage of the BIFET 42 rises and the abnormality detection circuit 14 outputs a signal.

When the BIFET45 is on, the voltage of the power supply 1 is applied to the diode 21,23,25 → BIFET45 → ground circuit,
The abnormality detection circuit 17 outputs a signal. BIFET 45 and 42 are controlled so that the ON signal does not enter at the same time, so the OR circuit
In the case of a ground accident, signals 30 and 31 do not output at the same time, and in the case of a grounding accident, either one output is output, so signals A and B are output.

As described above, in the case of a general overcurrent, the failure signal can output the signals A and C, and in the case of a grounding accident, the signals A and B can be output, so that the failure content can be determined and the failure diagnosis can be facilitated. It is possible.

In addition, the inverter bridge has been explained when using BIFET in the case of three phases, but it is a switching element that can be driven by a voltage signal such as FET, and the same method can be adopted for the element whose collector voltage rises at the time of overcurrent. Needless to say.

〔The invention's effect〕

As described above, according to the present invention, the overcurrent detection circuit is separated into two sets above and below the DC bus of the inverter bridge without providing a special ground fault detection circuit, and only the logical operation of AND and OR is used. It is possible to provide a failure detection circuit of a power converter that can display the details of a failure and can be realized as a failure diagnosis extremely easily, economically, and compactly.

[Brief description of drawings]

FIG. 1 is an embodiment of a failure detection circuit according to the present invention, FIG. 2 is a detailed view of the abnormality detection circuit of FIG. 1, and FIG. 3 is a conventional failure detection circuit. 1 ... AC power supply, 2 ... Rectifier, 21-26 ... Diode, 3 ... Capacitor 4 ... Inverter bridge 41-46 ... Electric valve, 5 ... PWM control circuit 6 ... AND circuit, 7 ... Gate drive circuit 8 …… Current detector, 9 …… Overcurrent detector 10 …… Zero-phase current transformer, 11 …… Ground fault detector 12 ～ 17 …… Abnormality detection circuit, 18,19 …… Delay circuit 30 , 31,32 …… OR circuit, 33,35 …… AND circuit 34 …… NOT circuit, 51 …… DC power supply 55,58,59 …… Transistor, 54,63 …… Photo coupler 56 …… Zener diode 52 , 53,57,60,62 …… Resistance

Claims (2)

[Claims] 1. A failure detection device for a power converter, which comprises a bridge connection of static induction self-extinguishing elements, wherein the collector-emitter voltage of the static induction self-extinction element exceeds a predetermined value, and A detection circuit which outputs a failure detection signal when there is a drive signal applied between the gate and the emitter, and a failure signal of the element group connected to the positive side of the direct current side of the bridge and a negative side of the direct current side of the bridge. The failure signals of the two groups are detected separately, and when the logical product of the failure signals of these two groups is established, it is judged as a short-circuit failure on the load side of the bridge or a failure of the bridge, and the failure signals of the two groups are detected. A failure detecting device for a power converter, which is provided with a logical operation means for determining a ground fault (or a short-circuit fault of the element) when the logical sum of is established. 2. The delay signals of the two groups are configured such that a delay time until the electrostatic induction type self-extinguishing element is turned on after the drive signal is applied is not output. A failure detection device for a power converter according to claim 1.