JPH04308455A - Protective system for power converter - Google Patents

Abstract

PURPOSE:To protect low rated voltage components of a power control means against breakdown upon conduction failure of a control rectifying element constituting a step-down chopper. CONSTITUTION:A voltage detector 21 detects the voltage between the anode and cathode of a first control rectifying element 3 connected, together with a second control rectifying element 4, in series between the positive and negative electrodes of a DC power supply 1. Thus detected voltage is fed to a conduction failure detector 22 which decides conduction failure of the first control rectifying element 3 if thus detected voltage is zero regardless of the fact that a controller is delivering a switching state control signal to the first control rectifying element 3, and then the switching state control signal is delivered to the second control rectifying element 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the protection of power converters against DC power sources.

0002

[Prior Art] Fig. 4 shows, for example, P1 of the Electric Vehicle Research Group's "Science of Electric Vehicles" February 1990 issue (vol. 43 No. 2).
5 to P19 show circuits of the conventional power conversion device. In the figure, 1 is a DC power supply, 2 is a switch that opens the subsequent circuit from the DC power supply, and 3 and 4 are first and second controlled rectifier elements (3 and 4 are represented by the circuit symbol of a GTO thyristor). (However, any element may be used as long as the switching state can be controlled.) 5 and 6 are the first control rectifier elements connected in antiparallel to the first and second control rectifier elements 3 and 4, respectively.
and a second diode; 7 is a reactor connected to the connection point of the first controlled rectifying element 3 and the second controlled rectifying element 4;
8 is a fill capacitor connected to the other end of the reactor 7 and the negative electrode side of the DC power supply 1; 9 is a power control means for supplying power to the main motor 10; and 11 is a power control means for supplying power to the main motor 10; This is a control device that outputs signals G1 and G2 that control switching states.

Next, the operation will be explained. Normally, during operation of the power conversion device, the switch 2 is closed, and the DC power source 1 is connected to the anode of the first controlled rectifier 3 and the cathode of the second controlled rectifier 4 through the switch 2. The power control means 9 uses components with low voltage ratings, with the main purpose of reducing the size and cost. Therefore, the steady voltage of the filter capacitor 8 is set lower than that of the DC power supply 1. The voltage control is performed by a step-down chopper made up of a first control rectifier 3 and a first diode 6, and a step-up chopper made up of a second control rectifier 4 and a second diode 5.

First, the operation of the step-down chopper will be explained. The step-down chopper acts during power operation to supply power from the DC power source 1 to the main motor 10, and reduces the opening/closing time ratio of the first control rectifying element 3, that is, the conduction rate α.

The voltage E FC of the filter capacitor 8 is adjusted with respect to the voltage E S of the DC power supply 1 by Equation 1. This E
FC is a value determined by the voltage rating of the components used in the power control means 9. When the first control rectifying element 3 is on, the voltage ES of the DC power supply 1 appears across the second diode 6, and the second diode 6 is off, and the load current gradually increases. . When the first controlled rectifying element 3 is turned off, the load current flows through the second diode 6 and gradually decreases. The reactor 7 inserted in series with the load serves to reduce the ripple of the negative current.

Next, the operation of the boost chopper will be explained. The boost chopper operates during regeneration when the main motor 10 operates as a generator. When the second control rectifying element 4 is on, the energy generated from the main motor 10 passes through the power control means 9 and is stored in the reactor 7. When the second control rectifying element 4 is off, the energy stored in the reactor 7 and the traction motor 10 are transferred to the power control means 9.
The energy generated is regenerated to the DC power supply 1 through the first diode 5. However, it goes without saying that these regeneration modes are based on the premise that there is a load on the DC power supply 1 side that absorbs regenerative energy. The time during which the second control rectifier 4 constituting the boost chopper is on is t
If we assume that the reactor 7 is sufficiently large and the current flowing through the reactor 7 is a constant value I1, then when the second control rectifying element 4 is on, the reactor 7 The energy stored in is E
FC ・I 1 ・t ON .

Next, when the second controlled rectifying element 4 is turned off, the energy regenerated into the DC power supply 1 is (ES-E
FC )・I 1・t OFF. In steady state,
Since these two are equal, E FC ・I 1・t ON
= (E S - E FC )・I 1・t OFF, so

[Math 2] is obtained. In the above formula,

Equation 3 Therefore, the output voltage E S of the boost chopper becomes larger than the input voltage E FC of the boost chopper. At this time, for the conduction rate β of the boost chopper,

##EQU4## As described above, by using a step-down chopper and a step-up chopper for the DC power supply 1, the input voltage of the power control means 9 at the subsequent stage can be kept low.

[0007]

[Problems to be Solved by the Invention] Since the conventional power converter is configured as described above, when the first control rectifying element has a conduction failure, the input side of the power control means that supplies power to the main motor is A certain filter capacitor will be connected to a DC power supply via a reactor, and the voltage will exceed the voltage rating of the power control means.
There was a problem in that there was a very high possibility of voltage breakdown of components.

The present invention has been made to solve the above-mentioned problems, and even when the first control rectifying element has a conduction failure, the component parts of the power control means having a low voltage rating can be prevented from being destroyed. It is an object of the present invention to provide a protection method for a power conversion device that can quickly protect the power converter.

[0009]

[Means for Solving the Problems] A protection system for a power conversion device according to the present invention includes first and second switching elements connected in series between the positive and negative poles of a DC power supply, and a protection system for these switching elements. A control device that outputs an on/off control signal, a reactor connected to a connection point between the first and second switching elements, and a filter connected between the other end of the reactor and the negative electrode side of the DC power source. In a power converter device comprising a capacitor and a power control means connected in parallel with the filter capacitor and supplying power to the main motor, when a continuity failure of the first switching element is detected, a second switching signal is sent to the control device. and a continuity fault detection means for commanding the output of an ON control signal to the element, and the continuity fault detection means includes a method for detecting a continuity fault from the voltage across the first switching element, and a method for detecting the continuity fault from the voltage across the filter capacitor. The present invention is characterized by using a method of detecting a conduction failure or a method of detecting a conduction failure from the value of current flowing through the reactor.

0010

[Operation] When the continuity fault detection means detects a fault in the first switching element using any of the above methods, the on-control signal is outputted from the first switching element to the second switching element to the control device. A command is issued to switch output to the switching element, and by making the second switching element conductive, the filter capacitor connected in parallel with the second switching element is shorted, preventing a voltage rise, and reducing the circuit voltage of the power converter. is immediately reduced to zero.

[0011]

EXAMPLES Example 1 An example of the present invention will be described below with reference to the drawings. 1st
In the figure, the same reference numerals as in FIG. 4 are the same as in FIG. 21 is a voltage detector that detects the voltage between the anode and cathode of the first controlled rectifier 3; 22 is the voltage detector 21;
A conduction failure of the first control rectifier 3 is detected from the output signal G1 of the control device 11 that controls the switching state of the first control rectifier 3, and the control device 11
This is a continuity fault detector that outputs a continuity fault signal.

Next, the operation will be explained. In the power conversion device configured as described above, when the first controlled rectifying element 3 causes a conduction failure, the first controlled rectifying element 3
The voltage between the anode and the cathode becomes 0, and the output of the voltage detector 21 also becomes 0. In addition, during normal times, the control device 11
Only when the output signal G1 of the first
The controlled rectifying element 3 is conductive, and the output of the voltage detector 21 is 0.
becomes.

Therefore, the output of the voltage detector 21 and the output signal G1 of the control device 11 are compared, and if the output of the voltage detector 21 is 0 when G1 is issuing an off command, the first
It is assumed that the continuity failure of the controlled rectifying element 3 is detected, and the continuity failure detector 22
outputs a continuity failure detection signal to the control device 11.

Upon receiving the continuity failure detection signal, the control device 11 first outputs a command to open the switch 2 from the power supply in order to disconnect the subsequent circuits, and the switch 2 is opened. However, if only switch 2 is opened, reactor 7
Since the energy stored in the filter capacitor 8 is transferred to the filter capacitor 8, overvoltage in the circuit including the power control means 9 after the filter capacitor 8 cannot be prevented.

Therefore, an ON command G2 is further outputted to the second controlled rectifying element 4, thereby making the second controlled rectifying element 4 conductive. When switch 2 is open, the first
When both of the control rectifying elements 3 and 4 conduct, the filter capacitor 8 is short-circuited through the reactor 7, and the voltage rating is reduced for the circuit including the power control means 9 after the filter capacitor 8. It is possible to prevent the voltage above from being applied, and also to quickly reduce the circuit voltage to 0, thereby protecting the entire power conversion device.

Another embodiment of the invention will be described. In FIG. 2, numeral 31 is a voltage detector that detects the voltage of the filter capacitor 8, and 32 is a voltage detector that detects the voltage of the filter capacitor 8. This is a continuity fault detector that detects a continuity fault in the first control rectifying element based on the magnitude of the current fault and outputs a continuity fault signal to the control device 11.

Next, the operation will be explained. When the first controlled rectifying element 3 has a conduction failure, the filter capacitor 8 is connected to the DC power supply 1 through the reactor 7, and the DC current is It will be charged from the power source 1.

The continuity fault detector 32 detects this voltage rise in the filter capacitor 8 between the output of the voltage detector 31 and a predetermined threshold value (determined from the voltage rating of the filter capacitor and voltage conversion means). When the output of the voltage detector 31 exceeds the threshold value, a continuity failure signal is output to the control device 11. The following operations are similar to those in the first embodiment.

Embodiment 3 Another embodiment of the present invention will be described. In FIG. 3, 41 is a current detector that detects the current of the reactor 7, and 42 is the output of the current detector 41 at a predetermined threshold value (determined from the filter capacitor and the voltage rating of the voltage conversion means). ), it is ranked first due to its size.
This is a continuity fault detector that detects a continuity fault in the controlled rectifying element and outputs a continuity fault signal to the control device 11.

Next, the operation will be explained. When the first controlled rectifying element has a continuity failure, the filter capacitor 8 will be connected to the DC power supply 1 through the reactor 7, and a current with an amplitude determined by the inductance of the reactor 7 and the capacity of the filter capacitor 8 will flow through the reactor. It will flow to 7. The current of this reactor is detected by the current detector 41, and the continuity fault detector 42 detects the output of the current detector 41 and a predetermined threshold (determined from the voltage rating of the filter capacitor and voltage conversion means). When the output of the current detector 41 exceeds the threshold value, a continuity failure signal is output to the control device 11. The following operations are similar to those in the first embodiment.

In the above embodiment, the first and second control rectifier elements are represented by GTOs, but any element may be used as long as the switching state can be controlled. Further, although the main motor is expressed as an induction motor, it is natural that a direct current motor can also be used to obtain the same effect.

[0022]

As described above, according to the present invention, the second switching element is made conductive when the first switching element has a conduction failure, so that the power control means after the filter capacitor can be controlled with a simple configuration. The effect is that it is possible to provide a highly reliable device at a low price that can suppress the voltage of the included circuit to below the rated voltage and protect the circuit from voltage breakdown.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a power conversion device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a power conversion device according to another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional power conversion device.

[Explanation of symbols]

1 DC power supply 3 First control rectifier 4 Second control rectifier 7 Reactor 8 Filter capacitor 9 Power control means 10 Main motor 11 Control device 22 Continuity fault detector 32 Continuity fault detector 42 Continuity fault detector

Claims (4)

[Claims] 1. First and second switching elements connected in series between a positive pole and a negative pole of a DC power source, a control device that outputs an on/off control signal to these switching elements, and a control device that outputs an on/off control signal to these switching elements, A reactor connected to the connection point of the second switching element, a filter capacitor connected between the other end of the reactor and the negative electrode side of the DC power supply, and a filter capacitor connected in parallel with the filter capacitor to provide power to the main motor. The power conversion device includes a continuity failure detection unit that instructs the control device to output an ON control signal to the second switching element when a continuity failure of the first switching element is detected. A protection method for a power conversion device characterized by: 2. The power converter protection system according to claim 1, wherein the continuity failure detection means detects a voltage between an anode and a cathode of the first switching element. 3. The power converter protection system according to claim 1, wherein the continuity failure detection means detects a voltage of a filter capacitor. 4. The power converter protection system according to claim 1, wherein the continuity failure detection means detects a current in a reactor.