JP3393034B2 - Overvoltage protection circuit for electric vehicle power converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overvoltage prevention circuit for an electric vehicle power converter when the electric vehicle enters a non-voltage section.

[0002]

2. Description of the Related Art A power conversion device for an AC electric vehicle is an AC-DC exchange converter using a switching element connected to an AC voltage circuit taken from a power line through a transformer. This switching element controls the switching timing in synchronization with the circuit voltage waveform.

In an AC electrification section of a railroad, a train line is divided at regular intervals, and power is supplied from a substation for each segment, so a power outage occurs for a certain period of time when passing between segments, but as an AC load. When a rotating machine such as a blower is connected, a voltage is induced by the inertial energy of rotation, and the voltage and frequency of the electric car side circuit gradually attenuates after the power line is cut off. The existing power conversion device continues to operate at this voltage, and therefore has stopped operating by detecting a decrease in voltage and a decrease in frequency, which are operation limits.

[0004]

With the recent improvement in semiconductor technology, a self-exciting converter having a reversible function of power running / regeneration has been used for drive control of an AC electric vehicle.
Immediately after a power line failure, the alternating cycle of the electric-vehicle-side circuit voltage waveform may instantaneously increase due to the interaction with the rotating machine.

On the other hand, in the power converters connected in parallel to the same circuit, there is no problem if the operation is stopped by detecting the increase of the alternating period, that is, the decrease of the frequency, but the detection delay time actually occurs. Therefore, it cannot be stopped instantaneously, and the operation continues for several cycles.

Since the power supply cycle signal for controlling the switching timing of the switching element of the power conversion device uses the resonance filter, it cannot follow even if the alternating cycle increases instantaneously, and the switching phase with respect to the power supply voltage is apparent. As a result, the DC voltage output from the power converter suddenly rises above a specified value, and adverse effects such as failure of load equipment occur. The present invention is to solve this problem.

[0007]

An overvoltage protection circuit for a power converter according to the present invention comprises an input voltage polarity detector connected from a waveform of an input voltage circuit through a resonance filter and an input current polarity detector of the power converter converter. And performing a logical operation on the polarities of the detection signals of the two detectors to control the conduction timing of the switching element of the power converter converter.

Further, the overvoltage prevention circuit of the power converter according to the present invention has the above-mentioned function, and when the input voltage polarities of the converter are the same, the switching element of the power converter converter is turned on / off at an appropriate conduction timing.
When the polarity becomes opposite, all the switching elements of this converter are turned off immediately.

Since the overvoltage prevention circuit of the power converter according to the present invention is configured as described above, when the alternating period of the input circuit voltage is steady, the power supply synchronizing signal and the actual input current through the resonance filter are The polarities are always the same,
The switching element turns on and off at an appropriate conduction timing, but when the alternating period of the input circuit voltage suddenly increases instantaneously, the polarities of the power supply synchronizing signal and the input current become opposite polarities for one period. By turning off all and holding this, it is possible to prevent overvoltage of the DC output voltage of the power converter. Hereinafter, one embodiment of the present invention,
It will be described in detail with reference to the drawings.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of an overvoltage protection circuit for a power converter when a thyristor is used as a switching element, and FIG. 2 is an overvoltage protection circuit for the power converter shown in FIG. FIG. 3 is a block diagram showing signals and logics of each unit according to the configuration of FIG. 2, and the same reference numerals as those in FIG. 2 denote parts having the same functions. In FIG. 1, a converter 4 by a thyristor mixing bridge is connected to an AC voltage 3 taken from a train line 1 through a transformer 2, and an output of this converter 4 is a DC output voltage smoothed by an LC filter 5. To be converted. On the other hand, a current detector 6 and an input current polarity detector 7, and a resonance filter 8 and an input voltage polarity detector 9 are connected to the AC voltage 3, and the outputs of these polarity detectors 7 and 9 are polarity logic operation unit 10, Gate control circuit 1
It is supplied to the converter 4 via 1.

The detailed circuit will be described below with reference to FIG. When the AC voltage 3 is steady, the signal from the input voltage polarity detector 9 causes the switching timing control circuit 12 to operate, and the thyristor of the converter 4 is ignited at an appropriate phase via the gate circuit 13.

When the alternating period of the AC voltage 3 suddenly increases, the input polarity voltage detector 9 detects it, and the polarity logic operation unit 10 operates the input polarity current detector 7 to gate the output signal. By shutting off the signal of the input part of the circuit 13 and turning off the gate of the thyristor, it is possible to prevent the overvoltage of the DC output voltage. In this state, the polarity logic operation unit 10
It is held by and is released by the reset signal 14.

The above is an example of the case where a thyristor is used as a switching element, but the present invention can also be applied when another switching element such as a GTO or a transistor is used. Further, it goes without saying that the polarity detector and the polarity logic operation can be realized by software of a computer.

[0014]

As described above, according to the present invention, in the power converter installed in the AC electric vehicle, when the power is passed through between the power supply sections of the electric power line and the power is cut off, the input circuit voltage of the power converter is reduced. It is possible to prevent the DC output voltage from becoming an overvoltage even if the alternating period of suddenly increases, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is an overvoltage prevention circuit diagram showing an embodiment of a power conversion device when a thyristor is used as a switching element.

FIG. 2 is a block diagram showing signals and logic of each unit according to the embodiment of FIG.

[Explanation of symbols]

1 train line 2 transformer 3 AC voltage 4 converter 5 LC filter 6 AC detector 7 Input current polarity detector 8 resonance filters 9 Input voltage polarity detector 10 Polarity logic operation unit 11 Gate control circuit 12 Switching timing control circuit 13 Gate circuit 14 Reset signal

Claims (2)

(57) [Claims] 1. A converter using a switching element for converting an AC voltage taken from a power line via a transformer into a desired DC voltage, and a switching timing control circuit for giving an ON / OFF operation to the switching element at an appropriate conduction timing. In the electric vehicle power conversion device configured by, when the alternating period of the alternating voltage is in a steady state, operate the converter with the switching timing control circuit,
When the alternating period increases, the polarities of the detection signals of these two detectors are logically calculated by the input voltage polarity detector and the input current polarity detector connected via the resonance filter from the input voltage waveform of the converter. And a conduction timing of the switching element of the co-inverter is controlled by an output signal of a polarity logic operation unit. 2. When the input current polarities of the converter are the same polarity, the switching elements of the converter are turned on and off at an appropriate conduction timing, and when the polarities are opposite, all the switching elements of the instant converter are turned off. The overvoltage prevention circuit for an electric vehicle power converter according to claim 1, which holds this state.