JPH1066348A - Short-circuit protector of 3-level power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect IGBT's(insulated gate bipolar transistors) of which a power converter outputting voltage of 3 levels, i.e., positive, negative and zero, from an overcurrent caused by a short-circuit, etc. SOLUTION: IGBT's 1a-1d are turned on and off by a gate controller 6 through gate drivers 2a-2d. When a short-circuit failure is detected by a short- circuit detector in the gate driver (2a, 2b, 2c or 2d), if the fact is transmitted to the gate controller 6 through a signal line (5a, 5b, 5c or 5d), the gate controller 6 controls an order in which the gate drivers are put into protective operations through a logic circuit 6A so as to avoid a prohibiting mode. With this constitution, the IGBT's are protected from excessive voltage burdens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an insulated gate bipolar transistor (hereinafter abbreviated as IGBT).
And a short-circuit protection device for a three-level power converter capable of outputting three levels of positive, zero, and negative voltages.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional example of this kind. In the figure, reference numerals 1a to 1d denote IGBTs as switching elements constituting one phase of the power converter, for example, elements 1a and 1b
To turn on (switching pattern 1) a positive DC voltage, to turn on elements 1b and 1c (switching pattern 2) to zero voltage, and to turn on element 1c
When 1 and 1d are turned on (switching pattern 3), a negative voltage is output.

[0003] Reference numerals 2a to 2d denote a gate drive device which includes a short-circuit detection device and a short-circuit protection device and drives a switching element, and 6 denotes a gate control device which controls these devices. Reference numerals 3a to 3d denote signal lines for transmitting on / off signals of a normal IGBT from the gate control device 6 to the gate drive devices 2a to 2d. Reference numerals 5a to 5d denote information detected by the gate drive devices 2a to 2d. Are shown.

In the case of a three-level power converter, when the apparatus is normally stopped, control is performed so that the IGBT 1a or 1d on the DC side is gated off first, and then the IGBT 1b or 1c on the AC side is turned off. In other words, in this type of short-circuit protection device, when a short-circuit occurs, the device is simply turned off immediately. In particular, when a short-circuit of the device is detected, the short-circuit state of the device is determined, and the device protection function of the gate drive device is determined according to a certain logic. No action has been taken to operate it.

[0005]

By the way, a three-level power converter requires a certain condition in a switching state,
For example, if the two IGBTs 1c and 1d of the lower arm are turned on and the IGBT 1c on the AC side is turned off first,
The current of the load flows back to the element of the upper arm, and this IGBT1
The potential on the collector side of c rises to the potential of P of the power supply.
Further, at this time, since the DC-side IGBT 1d is on, the emitter-side potential becomes the N potential of the power supply. Therefore, the above-described method causes a problem that the voltage of the power supply is applied to the element (1c in this case) whose short-circuit protection has been stopped. This problem is the same as described above if the two elements 1a and 1b of the upper arm are turned on and the element 1b is turned off first. Therefore, a mode in which switching is inhibited so that such a problem does not occur is hereinafter referred to as an inhibition mode. An object of the present invention is to protect the elements by preventing the inhibition mode.

[0006]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a three-level power converter comprising an IGBT is provided with a gate control unit for controlling the switching of each IGBT, and a short circuit. A detection circuit and a short-circuit protection circuit.
A short-circuit protection device for a three-level power converter for protecting the IGBT from overcurrent, comprising a logic circuit responsive to an output from the short-circuit detection circuit. A dedicated line for providing the output signal to the gate drive section is provided, and when a short circuit is detected, the logic circuit controls the start order of the short-circuit protection operation by the gate drive section.

According to the first aspect of the present invention, only the lock signal is output from the logic circuit, and upon detection of a short circuit, the gate drive unit to which the lock signal is not input can immediately start the short-circuit protection operation ( The invention according to claim 2) or, while the short-circuit protection circuit is always locked, only the unlock signal is output from the logic circuit, and the gate drive is performed only when the unlock signal is received when the short circuit is detected. The unit can immediately start the short-circuit protection operation (the invention of claim 3), or the gate drive unit immediately upon inversion of the input signal from the logic circuit upon detection of a short circuit, or after a certain period of time has elapsed. When the short-circuit protection operation is started and the input signal is not inverted, the state at the time of short-circuit detection can be maintained (the invention of claim 4).

[0008]

FIG. 1 is a block diagram showing an embodiment of the present invention. As is apparent from FIG. 4, this is different from the conventional example shown in FIG. 4 in that a logic circuit 6A is provided in the gate control device 6, and the gate control device 6 protects the gate driving devices 2a to 2d from short-circuit. This is the same as FIG. 4 except that signal lines 4a to 4d for transmitting signals to the device are added.

In such a configuration, an IGBT is
1a and IGBT1b, when passing through the route, the IGBT
Assume that 1c is turned on incorrectly and an arm short circuit occurs.
In this case, a short circuit is detected by the gate drive devices 2a to 2c, and this is transmitted to the gate control device 6 through the signal lines 5a to 5c. The gate control device 6 knows that a short circuit has occurred in the IGBTs 1a to 1c by this, and outputs an ON signal to the gate drive devices 2a and 2b.
Since the off signal is output to the gate driving devices 2c and 2d, it can be determined that the IGBT 1c has erroneously fired for some reason. Therefore, the gate control device 6 first causes the gate drive device 2a to start the protection operation, and locks the gate drive of the other IGBTs so as not to operate by the regular on / off signals. Next, after a certain time, the gate driving device 2b of the IGBT 1b starts the protection operation. These protection operation and lock signals are performed by dedicated signal lines 4a to 4d in order to distinguish them from normal on / off signals.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention. This example is different from FIG. 1 in that the short-circuit detection devices of the gate driving devices 2a to 2d directly supply a short-circuit detection signal to the short-circuit protection device, and the gate control device 6 to which the short-circuit detection signal is input. Thus, only the gate drive device to be locked or not is determined, and a lock signal is transmitted to the gate drive device via the dedicated signal lines 4a to 4d. Therefore, the gate drive device that has received the lock signal maintains the state at the time of the short circuit, and the gate drive device that has not received the lock signal immediately enters the short-circuit protection operation to protect the device.

In FIG. 2 as well, assuming that an IGBT 1c is erroneously turned on and an arm short circuit occurs when current flows through a route passing through the IGBT 1a and the IGBT 1b, this is detected by the gate drive devices 2a to 2c, and the information is detected. The signal is transmitted to the gate control device 6 through the signal lines 5a to 5c.
In the gate control device 6, the IGBTs 1a to IG
When it is known that a short circuit has occurred in the BT 1c, the gate drive devices 2a and 2b receive an ON signal and the gate drive device 2
Since an off signal is output to c and 2d, IGB
It can be determined that T1c is erroneously fired for some reason.
Therefore, the gate control device 6 first operates the gate drive device 2
In order to start the protection operation, the gate lock signal is not input, and the gate drive of the other IGBTs is locked so as not to be operated by regular ON / OFF signals. Next, after a certain time, the gate lock of the gate drive device 2b of the IGBT 1b is released, and the protection operation is started. The protection operation and the lock signal are performed by the dedicated lines 4a to 4d in order to be distinguished from the normal ON / OFF signal, as in the case of FIG.

In the above description, the gate control device 6 supplies the gate lock signal. However, if the gate drive device maintains the short-circuit protection function in a locked state,
It can be as follows. That is, when the gate control device 6 receives the signal indicating the detection of the short circuit, only the gate drive device to be unlocked is determined and the signal lines 4 a to 4
The lock release signal is transmitted to the gate driving device via c. The gate drive that has received the unlock signal starts short-circuit protection, and the gate drive that has not received the unlock signal holds the locked state.

Also in this case, IGBT 1a and IGBT 1b
Assuming that the IGBT 1c is erroneously turned on and an arm short circuit occurs at the time of passage through the route, the short circuit is detected by the gate drive devices 2a to 2c, and the information is transmitted to the gate control device 6 through the signal lines 5a to 5c. Conveyed to. In the gate control device 6, the IGBTs 1a to
Since it is known that a short circuit has occurred in the IGBT 1c, an ON signal is output to the gate drive devices 2a and 2b, and an OFF signal is output to the gate drive devices 2c and 2d.
It can be determined that the BT1c has been erroneously fired for some reason. Therefore, the gate control device 6 first inputs a signal to release the gate lock in order to start the protection operation to the gate drive device 2a, and the gate drive of the other IGBTs is operated by the normal on / off signal and short-circuit protection function. Lock not to. Next, after a certain time, IGB
Release the gate lock of the gate drive device 2b of T1b,
Start the protection operation. The protection operation and the lock signal are performed by the dedicated lines 4a to 4d in order to distinguish them from the normal ON and OFF signals, as in the conventional case.

FIG. 3 is a block diagram showing a third embodiment of the present invention. As apparent from comparison with FIG. 2, this example is characterized in that the dedicated lines 4a to 4d are deleted from FIG. 2, and that the gate lock signal is transmitted via the signal lines 3a to 3d. is there. Here, when the detection of the short circuit is transmitted to the gate control device 6, only the gate drive device to be protected is determined, and the polarity of the signal output when the short circuit is detected is inverted. The gate drive device starts the short-circuit protection operation on condition that the short-circuit is detected and the polarity of the input signal is inverted. Therefore, the dedicated lines 4a to 4d for short-circuit protection are not required. At this time, the start timing of the short-circuit protection operation can be delayed by shifting the timing of inverting the polarity of the input signal from each other. In the gate driving device in which the polarity of the input signal is not inverted, the state at the time of detecting the short circuit is maintained. In the gate drive device in which no short circuit is detected in the off state, the gate control device 6 does not particularly output a signal so as to maintain the off state. In this example, when a short circuit is detected, an inversion signal is input to the gate drive device 2a of the IGBT 1a via the signal line 3a, and after a predetermined time, the IGBT 1a
If an inversion signal is input to the gate drive device in the order of BT1b and IGBT1c, the same short-circuit protection operation as in FIG. 1 can be performed.

[0015]

According to the present invention, when the short circuit is detected, the gate drive device performs the protection operation of the element so as not to enter the inhibition mode of the three-level power converter based on the position information of the element that has detected the short circuit. With this configuration, there is an advantage that the device can be stopped without applying a large voltage duty to the IGBT element when the short-circuit protection is stopped.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional example.

[Explanation of symbols]

1a to 1d IGBT, 2a to 2d gate drive device,
3a to 3d, 4a to 4d, 5a to 5d: signal line, 6: gate control device, 6A: logic circuit.

Claims (4)

[Claims] 1. A three-level power converter composed of an IGBT includes a gate control unit for controlling switching of each IGBT, a short-circuit detection circuit and a short-circuit protection circuit, and receives a signal from the gate control device. A gate drive unit for driving each IGBT; and a short-circuit protection device for a three-level power converter for protecting the IGBT from overcurrent, wherein the gate control unit responds to an output from a short-circuit detection circuit,
A short-circuit protection device for a three-level power converter, further comprising a logic circuit for controlling a start order of a short-circuit protection operation by the gate driver. 2. The gate driver according to claim 1, wherein only a lock signal is output from the logic circuit, and when a short circuit is detected, the gate driver to which the lock signal is not input immediately starts a short circuit protection operation. Short-circuit protection device for a three-level power converter. 3. The short-circuit protection circuit is always locked, while the logic circuit outputs only an unlock signal, and the gate driver immediately short-circuits only when the unlock signal is received upon detection of a short circuit. The short-circuit protection device for a three-level power converter according to claim 1, wherein a protection operation is started. 4. The gate driving section starts a short-circuit protection operation immediately when an input signal from the logic circuit is inverted at the time of detecting a short-circuit or after a lapse of a predetermined period. The short-circuit protection device for a three-level power converter according to claim 1, wherein the state is maintained.