JPH10164854A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a switching element against application of an overvoltage. SOLUTION: Currents flowing through transistors 3A-3D are monitored by means of short circuit detection/interruption circuits 5A, 5B and short circuit detection circuits 6A, 6B. When short circuit of power supply is detected, the transistors 3A, 3D are turned off at a timing slower than a normal timing according to the interrupting operation of the short circuit detection/interruption circuits 5A, 5B and a gate signal from a gate control section 16. Subsequently, one of the transistors 3B or 3C is turned on and the other is turned off at a timing slower than the normal timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power converter, and more particularly to a power converter suitable for use as a three-level inverter.

[0002]

2. Description of the Related Art As inverters, there are known an inverter provided with two switching elements per phase and a so-called three-level inverter provided with four switching elements per phase. The three-level inverter has a function of protecting the switching elements from short-circuiting of the power supply, for example, when three of the four switching elements are turned on at the same time, the power supply may be short-circuited and the switching elements may be damaged. The one provided with is proposed.
For example, as described in JP-A-6-327262, current detecting means for detecting the current of a switching element connected to the high voltage side of the DC bus and the current of the switching element connected to the low voltage side of the DC bus are provided. When an overcurrent is detected by any of the current detection means,
Of the four switching elements, both the switching element connected to the high voltage side of the DC bus and the switching element connected to the low voltage side of the DC bus are turned off, and then the two switching elements connected to the output terminal side are turned off. Things to turn on are suggested. With such a configuration,
Even when an overcurrent is detected, it is possible to prevent the entire voltage of the DC bus (DC power supply) from being applied to a single switching element.

[0003]

In the prior art, when an overcurrent is detected, two switching elements directly connected to a DC power supply are turned off, and then two switching elements directly connected to an output terminal are connected together. Since the switching element is turned on, if the switching element directly connected to the DC power supply breaks down at this time, damage to the switching element may be increased due to the continuation of the power supply short circuit. When a power supply short circuit occurs, an excessive current flows through the switching element. At this time, if the switching element is cut off at a high speed, since di / dt is large, the switching element may break down due to an overvoltage generated by wiring inductance. There is.

An object of the present invention is to provide a power converter capable of preventing an overvoltage from being applied to a switching element when an abnormality occurs.

[0005]

In order to achieve the above object, the present invention provides a power supply system comprising a plurality of DC power supplies connected in series between a positive terminal and an output terminal connected to a load. A positive-side main switching element and a positive-side auxiliary switching element connected in series, and a negative-side main switching element and a negative side inserted between the negative terminal and the output terminal of the DC power supply and connected in series with each other; The auxiliary switching element, the positive connection point of the positive main switching element and the positive auxiliary switching element is the cathode side, and the neutral point where the plurality of DC power supplies are connected in series with each other is the anode side, and the positive connection point is The positive side rectifying element connected to the neutral point, the negative side connection point of the negative side main switching element and the negative side auxiliary switching element is the anode side, and the neutral point is the cathode side. The negative-side rectifier connected to the negative-side connection point and the neutral point, a plurality of freewheel rectifiers connected in anti-parallel to each of the switching elements, and each at a timing according to the mode of the control pattern. Switching control means for controlling a switching operation of a switching element to generate a three-level conversion output, wherein the positive main switching element is connected to a positive terminal of the DC power supply, and the positive auxiliary switching element is An output terminal, wherein the negative-side main switching element is connected to a negative-side terminal of the DC power supply, and the negative-side auxiliary switching element is configured to detect an abnormality of a load current in the power converter connected to the output terminal; Load current abnormality detecting means, and the positive side main switch irrespective of a control pattern mode in response to a detection output of the load current abnormality detecting means. And an auxiliary switching control means for turning off the element and the negative side main switching element and thereafter turning on one of the positive side auxiliary switching element and the negative side auxiliary switching element and turning off the other. The power converter is configured as follows.

In configuring the power converter, short-circuit detecting means for detecting short-circuit of at least one of the plurality of DC power supplies is provided in place of the load current abnormality detecting means, and short-circuit detecting means is provided as auxiliary switching control means. In response to the detection output of the detection means, regardless of the mode of the control pattern,
The positive switching element and the negative main switching element are turned off, and thereafter, a function having a function of turning on one of the positive auxiliary switching element and the negative auxiliary switching element and turning off the other is provided. it can.

In configuring the power converter, each of the main switching elements is turned off in response to the detection output of the load current abnormality detecting means, the short circuit detecting means, and the short circuit detecting means and the load current abnormality detecting means. After that, the auxiliary switching element may be configured to have a function of turning on one of the auxiliary switching elements and turning off the other.

In configuring each of the power converters,
The following factors can be loaded: (1) The auxiliary switching control means turns off the switching element to be turned off at a timing later than the timing set by the mode of the control pattern when the short-circuit detection means detects the short-circuit.

(2) When the short-circuit is detected by the short-circuit detecting means, the auxiliary switching control means determines the mode of the control pattern or the direction of the load current, and based on the result of the determination,
One of the positive auxiliary switching element and the negative auxiliary switching element is turned on and the other is turned off.

(3) The short-circuit detecting means comprises a plurality of current detecting means for respectively detecting that the current of each switching element is larger than the abnormal load current value.

According to the above means, when the load current is abnormal or when the short circuit of the DC power supply is detected, each of the main switching elements is controlled to be off, and thereafter, one of the auxiliary switching elements is turned on. Since the other is controlled to be turned off, even if one of the main switching elements breaks down in the process of this control, the power supply short circuit is prevented by the turned off auxiliary switching element. For this reason, it is possible to prevent an overvoltage from being applied to the switching element. In addition, when the power supply short circuit is detected, the switching element is turned off at a timing later than the timing according to the mode of the control pattern, so that it is possible to prevent the switching element from being broken down due to an overvoltage generated by the wiring inductance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a power converter showing one embodiment of the present invention. In FIG. 1, the power converter is:
It is configured as a three-phase three-level inverter (however, FIG. 1 shows a configuration for only one phase), and is connected to DC power supplies 1A and 1B. DC power supply 1A, 1B
Are connected in series with each other, and a series connection point is grounded as a neutral point O. Then, between the positive terminal of the DC power supply 1A and the negative terminal of the DC power supply 1B, four IGBTs (Insulates) are provided as self-extinguishing switching elements.
d Gate Bipolar Transisto
r: Hereinafter, simply referred to as a transistor. ) 3A, 3B,
3C and 3D are connected in series and inserted.
The transistor 3A is connected in series with the transistor 3B as a positive auxiliary switching element as a positive main switching element, the collector of the transistor 3A is connected to the positive terminal of the DC power supply 1A, and the emitter of the transistor 3B is connected to the output terminal 10A. It is connected to the. A positive connection point 12 which is a series connection point of the transistors 3A and 3B.
Is connected to the clamp diode 2A connected to the neutral point O. Transistor 3C is connected in series with transistor 3D as a negative-side main switching element as a negative-side auxiliary switching element. The collector of transistor 3C is connected to output terminal 10, and the emitter of transistor 3D is connected to the negative terminal of DC power supply 1B. Connected to the side terminal. Further, a clamp diode 2B connected to a neutral point O is connected to a negative connection point 14, which is a connection point between the transistors 3C and 3D in series. Further, freewheel diodes 4A to 4D as freewheel rectifiers are connected in anti-parallel to the transistors 3A to 3D.

The transistors 3A and 3D are provided with short-circuit detection / cutoff circuits 5A and 5B, respectively.
Each of the transistors 3B and 3C has a short-circuit detection circuit 6
A and 6B are provided. The short-circuit detection / cutoff circuits 5A and 5B are configured such that the current flowing through each of the transistors 3A and 3D is higher than the abnormal load current value based on the current corresponding to the voltage between the positive and negative electrodes of the transistors 3A and 3D (the voltage between the collector and the emitter). It has a function as a current detecting means for detecting a large value, and a function as a short-circuit detecting means for detecting a power supply short-circuit from a detection value of the current detecting means. Furthermore, short-circuit detection / cutoff circuits 5A, 5B
Has a function of shutting off the transistors 3A and 3D at a timing later than the timing set in the control pattern mode of the gate control unit 16 when a short circuit is detected.

On the other hand, the short-circuit detection circuits 6A and 6B detect a current corresponding to the voltage between the positive and negative main electrodes (voltage between the emitter and the collector) of the transistors 3B and 3C, and detect that the current is larger than the abnormal load current value. It has a function as a short-circuit detecting means for detecting a power supply short-circuit from the detection output of the current detecting means.
The short-circuit detection / cutoff circuits 5A and 5B and the short-circuit detection circuit 6
A and 6B are connected to the gate control unit 16, respectively. The gate control unit 16 includes a load current detector 18 for detecting a current flowing through a circuit connecting the output terminal 10 and a load.
Is detected.

The gate control unit 16 includes an on / off control unit 2
0, an OR gate 22, a latch circuit 24, a comparator 26, and a latch circuit 28. OR gate 22
Includes short-circuit detection / cutoff circuits 5A and 5B and short-circuit detection circuit 6
The detection outputs A and 6B are input, and a high-level signal is output to the on / off control unit 20 via the latch circuit 24 in response to one of the detection outputs.
The comparator 26 has a load overcurrent set value (load current abnormal value) 30
Is compared with the detected current of the load current detector 18, and when the detected current exceeds the load overcurrent set value 30, a high-level signal indicating an abnormal load current is sent to the on / off control unit 20 via the latch circuit 28. Output. That is, the load current detector 18 and the comparator 26 are configured as load current detection means.

The on / off control unit 20 is connected to the gates of the transistors 3A and 3D via the short-circuit detection / cutoff circuits 5A and 5B, and is directly connected to the gates of the transistors 3B and 3C. This on / off control unit 20
Are configured as switching control means for controlling the switching operation of each of the transistors 3A to 3D at a timing according to the mode of the control pattern to generate a three-level conversion output. For example, as shown in FIG. 2, in mode 1, the transistors 3A and 3C are alternately turned on and off while the transistor 3D is turned off and the transistor 3B is turned on.
With A off and transistor 3C on,
The transistors 3B and 3D are alternately turned on and off to generate an AC sine wave signal at the output terminal 10.

The on / off control unit 20 is configured as an auxiliary switching means together with the interruption circuit of the short-circuit detection / interruption circuits 5A and 5B.
, The transistors 3A and 3D are turned off regardless of the mode of the control pattern, and then one of the transistors 3B and 3C is turned on and the other is turned off. . In the ON / OFF control unit 20, a circuit for supplying a gate signal to the gates of the transistors 3B and 3C is provided with a control circuit 32 and a diode D1 as a time constant circuit.
Resistors R1, R2, R3, switch S1, capacitor C1
Is provided. The switch S1 is turned on during normal operation, and a gate signal for turning on the transistors 3B and 3C is a diode D1, resistors R1, R2 and R2.
3, is supplied to each transistor via the switch S1 and the capacitor C1. At this time, the resistors R1, R2, and R3 are connected in parallel, and since the resistors R1 and R3 are small, the time constant is small. When the transistors 3B and 3C are turned off in a normal state, the gate signal has a negative voltage, so that only the resistors R2 and R3 are connected in parallel. However, since the resistance value of the resistor R3 is small, the time constant is small.

On the other hand, when the short circuit is detected, the switch S1 is turned off. Therefore, when the transistors 3B and 3C are turned off when the short circuit is detected, the time constant of the gate signal that becomes a negative voltage is determined by the resistor R2 and the capacitor C1. The time constant is larger than the off time constant in the normal state. Therefore, when the transistors 3B and 3C are turned off during a short circuit, the transistors 3B and 3C can be safely turned off at a later timing than in a normal state, even when a large current is cut off.

Next, the operation of the three-level inverter shown in FIG. 1 will be described with reference to FIGS.

First, when the three-level inverter is operating in accordance with the mode 1 shown in FIG. 2, when the transistor B is turned on, as shown in FIG.
The transistors 3A and 3C are turned on and off alternately. At this time, the current IL flows from the inverter toward the load. When the transistor 3A breaks down while the transistors 3B and 3C are turned on, as shown in FIG. 4B, all the transistors 3A, 3B and 3C are turned on, and both ends of the DC power supply 1A are short-circuited. It will be done. When a power supply short-circuit occurs and a short-circuit of the power supply is detected by one of the short-circuit detection / cutoff circuit 5A and the short-circuit detection circuits 6A and 6B, the transistors 3A and 3B are turned off and then specified in the control pattern mode. At a timing later than the timing, the transistor 3C is turned off.
At this time, the transistor 3B is kept on. That is, when any one of the transistors 3B and 3C is turned on and one of the transistors 3B and 3C is turned off, the mode of the control pattern is determined or the load current is flowing from the output terminal 10 to the load side. Turn off. After the transistor 3C is turned off, a current flows in a state as shown in FIG. Therefore, even if the transistor 3A breaks down while the transistors 3B and 3C are turned on, the transistor 3C is turned off, so that the short circuit at both ends of the DC power supply 1A is prevented from continuing. It is possible to prevent another transistor from being successively broken by the breakdown of the transistor 3A. That is, it is possible to prevent an overvoltage from being applied to another transistor due to the breakdown of the transistor 3A.

Next, when the three-level inverter operates according to the mode 2 shown in FIG. 2, the transistor 3A is turned off and the transistor 3 is turned off, as shown in FIG.
When C is off, the transistors 3B, 3D
Are turned on and off alternately, and the current I flows from the load to the DC power supply 1B side.
L flows. If the transistor 3D breaks down while the transistors 3B and 3C are on, this means that the transistors 3B, 3C and 3D are turned on at the same time, and both ends of the DC power supply 1B are short-circuited and the power supply is short-circuited. . This power supply short circuit causes short circuit detection circuits 6A and 6A.
B, when detected by any of the short-circuit detection / cutoff circuits 5B, the transistors 3A and 3D are turned off at a timing later than the timing according to the control pattern. After that, the transistor 3C among the transistors 3B and 3C
Is turned on, and the transistor 3B is turned off. Also in this case, the transistor 3B is turned off at a timing later than the normal timing set by the mode of the control pattern. When one of the transistors 3B and 3C is turned off, the mode 2 of the control pattern is determined or the direction of the load current is determined. In this case, since the load current is flowing from the load to the power supply 1B, the transistor 3B is turned off.

As described above, when the transistor 3D breaks down while the transistors 3B and 3C are on, after the transistor 3A is turned off,
Since the transistor 3C is turned on and the transistor 3B is turned off at a timing later than usual, it is possible to prevent the power supply short circuit from continuing, and to apply an overvoltage to the transistors other than the transistor 3D that caused the breakdown. Can be prevented from being applied.

In the above-described embodiment, the operation when the power supply is short-circuited has been described. However, even when the load current is abnormal, after turning off the transistors 3A and 3D, one of the transistors 3B and 3C is turned on and the other is turned on. Is turned on, it is possible to prevent the power supply short circuit from continuing, and to prevent an overvoltage from being applied to the transistors 3A to 3D when the load current is abnormal, and to continue the power supply short circuit. , And chain damage of the transistors can be prevented.

Further, in the above-described embodiment, the case where the IGBT is used as the switching element has been described.
As the self-extinguishing type element, for example, a gate-off thyristor (GTO), a field effect transistor (FET), or the like can be used. In the case of a device such as a GTO, when a power supply is short-circuited or when a load current is abnormal, the device can be turned off without delaying the timing of the device to be turned off from the normal timing.

[0026]

As described above, according to the present invention,
When the power supply is short-circuited or when the load current is abnormal, each positive and negative main switching element is turned off, and then one of the positive and negative auxiliary switching elements is turned on and the other is turned off. In addition, it is possible to prevent an overvoltage from being applied to the switching element, and to contribute to improvement in reliability of the switching element.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a power converter according to an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining a control mode of the power converter shown in FIG.

FIG. 3 is an explanatory diagram of a configuration of a time constant circuit.

FIG. 4 is an explanatory diagram for explaining an operation in a mode 1;

FIG. 5 is an explanatory diagram for explaining an operation in a mode 2;

[Explanation of symbols]

 1A, 1B DC power supply 2A, 2B Clamp diode 3A, 3B, 3C, 3D IGBT 4A, 4B, 4C, 4D Freewheel diode 5A, 5B Short circuit detection / cutoff circuit 6A, 6B Short circuit detection circuit 16 Gate control unit 18 Load current detection Unit 20 ON / OFF control unit 22 OR gate 24 Latch circuit 26 Comparator 28 Latch circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Tachikawa 5-2-1 Omika-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Omika Plant

Claims (6)

[Claims] 1. A positive main switching element and a positive auxiliary switching element inserted between the positive terminals of a plurality of DC power supplies connected in series and an output terminal connected to a load and connected in series with each other. A negative main switching element and a negative auxiliary switching element inserted between the negative terminal and the output terminal of the DC power supply and connected in series with each other; a positive main switching element and a positive auxiliary switching element A positive-side rectifying element connected to the positive-side connection point and the neutral point as a positive-side connection point with the cathode side and a neutral point where the plurality of DC power supplies are connected in series to each other as an anode side, A negative side rectifier connected to the negative side connection point and the neutral point with the negative side connection point between the negative side main switching element and the negative side auxiliary switching element as the anode side and the neutral point as the cathode side Element, a plurality of freewheel rectifiers connected in anti-parallel to each of the switching elements, and switching control for controlling the switching operation of each switching element at a timing according to the mode of the control pattern to generate a three-level conversion output. Means, the positive-side main switching element is connected to a positive-side terminal of the DC power supply, the positive-side auxiliary switching element is connected to the output terminal, and the negative-side main switching element is connected to the negative side of the DC power supply. A power current converter connected to the output terminal, wherein the negative auxiliary switching element is connected to the output terminal, wherein the load current abnormality detecting means for detecting an abnormality of the load current; and The positive main switching element and the negative main switching element are turned off regardless of the mode of the control pattern. And an auxiliary switching control means for turning on one of the positive auxiliary switching element and the negative auxiliary switching element and turning off the other thereafter. 2. A positive-side main switching element and a positive-side auxiliary switching element which are inserted between the positive terminals of a plurality of DC power supplies connected in series and an output terminal connected to a load and connected in series with each other. A negative main switching element and a negative auxiliary switching element inserted between the negative terminal and the output terminal of the DC power supply and connected in series with each other; a positive main switching element and a positive auxiliary switching element A positive-side rectifying element connected to the positive-side connection point and the neutral point as a positive-side connection point with the cathode side and a neutral point where the plurality of DC power supplies are connected in series to each other as an anode side, A negative side rectifier connected to the negative side connection point and the neutral point with the negative side connection point between the negative side main switching element and the negative side auxiliary switching element as the anode side and the neutral point as the cathode side Element, a plurality of freewheel rectifiers connected in anti-parallel to each of the switching elements, and switching control for controlling the switching operation of each switching element at a timing according to the mode of the control pattern to generate a three-level conversion output. Means, the positive-side main switching element is connected to a positive-side terminal of the DC power supply, the positive-side auxiliary switching element is connected to the output terminal, and the negative-side main switching element is connected to the negative side of the DC power supply. A power converter connected to a terminal, wherein the negative-side auxiliary switching element is connected to the output terminal; wherein the short-circuit detecting means for detecting a short circuit of at least one of the plurality of DC power supplies, In response to a detection output, the positive main switching element and the negative main switching element are independent of the mode of the control pattern. And an auxiliary switching control means for turning off the switching element and thereafter turning on one of the positive auxiliary switching element and the negative auxiliary switching element and turning off the other. 3. A positive-side main switching element and a positive-side auxiliary switching element inserted between the positive terminals of a plurality of DC power supplies connected in series and an output terminal connected to a load and connected in series with each other. A negative main switching element and a negative auxiliary switching element inserted between the negative terminal and the output terminal of the DC power supply and connected in series with each other; a positive main switching element and a positive auxiliary switching element A positive-side rectifying element connected to the positive-side connection point and the neutral point as a positive-side connection point with the cathode side and a neutral point where the plurality of DC power supplies are connected in series to each other as an anode side, A negative side rectifier connected to the negative side connection point and the neutral point with the negative side connection point between the negative side main switching element and the negative side auxiliary switching element as the anode side and the neutral point as the cathode side Element, a plurality of freewheel rectifiers connected in anti-parallel to each of the switching elements, and switching control for controlling the switching operation of each switching element at a timing according to the mode of the control pattern to generate a three-level conversion output. Means, the positive-side main switching element is connected to a positive-side terminal of the DC power supply, the positive-side auxiliary switching element is connected to the output terminal, and the negative-side main switching element is connected to the negative side of the DC power supply. A short-circuit detecting means for detecting a short-circuit of at least one of the plurality of DC power supplies, wherein the short-circuit detection means detects a short-circuit of at least one of the plurality of DC power supplies; Of the load current abnormality detecting means for detecting the short-circuit detecting means and the detection output of the load current abnormality detecting means. The positive main switching element and the negative main switching element are turned off irrespective of the mode of the control pattern in response to at least one of the detection outputs, and then one of the positive auxiliary switching element and the negative auxiliary switching element is turned off. And an auxiliary switching control means for turning on the other and turning off the other. 4. The auxiliary switching control means turns off a switching element to be turned off at a timing later than a timing set by a control pattern mode when a short circuit is detected by the short circuit detection means. 4. The power converter according to 2, 3 or 4. 5. The auxiliary switching control means determines a mode of a control pattern or a direction of a load current when a short circuit is detected by the short-circuit detection means, and based on the determination result, a positive auxiliary switching element and a negative auxiliary switching element. 5. The power converter according to claim 1, wherein one of the power converters is turned on and the other is turned off. 6. A short-circuit detecting means comprising a plurality of current detecting means for respectively detecting that the current of each switching element is larger than an abnormal load current value. 6. The power converter according to claim 4 or 5.