JPH07154974A - Power converter apparatus - Google Patents

Abstract

PURPOSE:To obtain a power converter apparatus in which a resistor for overvoltage suppression is not overheated and damaged even when an AC switch is not opened normally due to a fault or the like and whose reliability is high in the power converter apparatus which is mounted on an AC electric vehicle. CONSTITUTION:A current detector 15 which detects the current of a resistor 11 for overvoltage suppression is provided. When an AC switch is not opened normally, an AC circuit breaker 2 is opened under the condition of the output of the current detector 15, and a current to the resistor 11 for overcurrent suppression from the AC power supply is cut off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter including a PWM converter and an inverter mounted on, for example, an AC or AC / DC electric vehicle, and more particularly to an overvoltage suppressing device for the power converter.

[0002]

2. Description of the Related Art FIG. 5 shows a generally well-known PWM.
It is a figure which shows the main circuit structure of the alternating current electric vehicle provided with the converter and the inverter, for example, it is introduced in February 19th, the 26th "Cybernetics utilization in railway domestic symposium collection" P191-195. . In the figure, 1 is a pantograph which slides on an overhead wire and is connected to an AC power source, 2 is an AC circuit breaker, 3 is a transformer, 4 is an arm element consisting of a GTO thyristor and a diode connected in antiparallel to the bridge. The configured PWM converter, 5 is a filter capacitor connected to the DC side of the PWM converter 4, 6 is a PWM inverter connected to the filter capacitor 5, and 7 is an electric motor connected to the three-phase AC side of the PWM inverter 6. is there.

Reference numeral 8 is an AC switch connected and inserted between the transformer 3 and the PWM converter 4, and reference numerals 9 and 10 are a charging switch and a charging resistor respectively connected between both electrodes of the AC switch 8. Reference numerals 11 and 12 respectively denote an overvoltage suppressing resistor and an overvoltage suppressing thyristor connected between both ends of the filter capacitor 5, and 13 denotes an overvoltage detector for detecting an overvoltage applied to the filter capacitor 5. Suppression circuit 14
Make up.

Next, the operation will be described. High-voltage AC power from the AC power source collected from the pantograph 1 is supplied to the primary winding of the transformer 3 through the AC breaker 2. Then, the AC power stepped down to a predetermined voltage by the secondary winding of the transformer 3 is supplied to the PWM converter 4 via the AC switch 8. The PWM converter 4 converts the single-phase AC power into DC power and operates so as to keep the voltage across the filter capacitor 5 constant. The PWM inverter 6 converts the DC power from the filter capacitor 5 into a variable voltage,
It is converted into three-phase AC power of variable frequency and drives the electric motor 7, which is an AC load. The PWM converter 4 and the PWM inverter 6 can perform not only the power running operation but also the regenerative braking operation. At the time of braking, contrary to the above-described operation, the electric motor 7
The AC power from is returned to the overhead wire side from the pantograph 1 via the transformer 3.

By the way, if the load seen from the electric vehicle suddenly decreases due to the disconnection of the pantograph 1 or a sudden change of the load during regenerative braking, and the voltage across the filter capacitor 5 becomes higher than usual, the PWM converter 4 and the PWM inverter 6 are driven. An abnormal voltage will be applied to the semiconductor element. Therefore, in order to prevent such an adverse effect, the overvoltage suppressing circuit 14
Is provided.

That is, when the voltage across the filter capacitor 5 becomes higher than a predetermined value, the overvoltage detector 13 detects it, and the overvoltage suppressing thyristor 12 is ignited by the detection output signal, whereby the filter capacitor 5 is turned on. Short-circuiting via the overvoltage suppressing resistor 11 releases the energy stored in the filter capacitor 5 to reduce its voltage. If this state is left as it is, the PW
Since the current continues to flow through the overvoltage suppressing resistor 11 through the diode of the M converter 4, the AC switch 8 is opened and the continuous current is cut off after a predetermined time has elapsed from the ignition of the overvoltage suppressing thyristor 12. Therefore, the heat capacity of the overvoltage suppressing resistor 11 is also set to a relatively small value on the assumption of the above operation.

[0007]

Since the conventional overvoltage suppressing circuit in the electric vehicle is configured as described above, the AC switch 8 is opened even if the opening command is output due to a failure or the like. If it does not operate, the current continues to flow through the overvoltage suppressing resistor 11, resulting in overburning and resulting in a serious accident.

The present invention has been made in order to solve the above-mentioned problems, and even if the AC switch does not normally open due to a failure or the like, the overvoltage suppressing resistor may be overheated and burned. The purpose is to obtain a highly reliable power conversion device.

[0009]

According to a first aspect of the present invention, there is provided a power converter including a current detector for detecting the current of the resistor, and when the AC switch does not perform the opening operation, the current detector The AC circuit breaker is opened under the AND condition between the output and the AC switch opening operation command output.

A power converter according to a second aspect of the present invention includes a current detector for detecting the AC side current of the converter, and when the AC switch does not perform the opening operation, the output of the current detector and the opening of the AC switch. The AC breaker is opened under the AND condition with the operation command output.

Further, the power converter according to claim 3 is provided with a voltage detector for detecting the voltage across the resistor, and when the AC switch does not perform the opening operation, the output of the voltage detector and the opening of the AC switch. The AC breaker is opened under the AND condition with the operation command output.

[0012]

In the power converter according to the first aspect of the present invention, when the AC switch does not normally perform the opening operation even though the opening operation command is output, the current detection for detecting the current of the resistor is performed. The AC circuit breaker opens the circuit on the condition of the output of the resistor and interrupts the follow current to the resistor.

In the power converter according to the second aspect of the present invention, the current detection for detecting the AC side current of the converter when the AC switch does not normally perform the opening operation even though the opening operation command is output. The AC circuit breaker opens the circuit on the condition of the output of the resistor and interrupts the follow current to the resistor.

Further, in the power converter according to the third aspect of the present invention, when the AC switch does not normally perform the opening operation even though the opening operation command is output, the voltage detection for detecting the voltage across the resistor is performed. The AC circuit breaker opens the circuit on the condition of the output of the resistor and interrupts the follow current to the resistor.

[0015]

EXAMPLES Example 1. 1 is a diagram showing a main circuit configuration of an AC electric vehicle according to a first embodiment of the present invention. The difference from the conventional one is that a current detector 15 for detecting the current of the overvoltage suppressing resistor 11 is provided, and the conventional overvoltage suppressing resistor 11, the overvoltage suppressing thyristor 12, the overvoltage detector 13 and the current detector are provided. An overvoltage suppressing circuit 16 is composed of 15.

Next, the voltage suppression protection operation when an overvoltage occurs in the filter capacitor 5 during regenerative braking will be described with reference to the flowchart of FIG. The generated AC power from the electric motor 7 is PWM inverter 6, PWM
If the absorption capacity of regenerative power is lowered due to disconnection of the pantograph 1 or the like while returning to the overhead wire side via the converter 4 and the transformer 3 for regeneration, the filter capacitor 5
The voltage across both ends suddenly rises. When this voltage exceeds a predetermined value, the overvoltage detector 13 detects this overvoltage (step S1), and the PWM inverter 6 and the PWM converter 4 are detected.
Is turned off (steps S2 and S3) to stop the regenerative braking operation, and the overvoltage suppressing thyristor 12
Is ignited (step S4), the energy stored in the filter capacitor 5 is discharged through the overvoltage suppressing resistor 11 (step S5), and the voltage across it is dropped.

Simultaneously with the ignition of the overvoltage suppressing thyristor 12, a current is supplied from the overhead wire side to the overvoltage suppressing resistor 11 through the diode of the PWM converter 4. Therefore, an opening operation command is output to open the AC switch 8 after a lapse of a certain time from the ignition of the overvoltage suppressing thyristor 12 (step S6). As a result, if the AC switch 8 normally opens, the current flowing through the overvoltage suppressing resistor 11 disappears (YES in step S7). However, if the AC switch 8 does not normally open due to a failure or the like (NO in step S7) and the output of the current detector 15 remains ON (step S8), the AC breaker 2 is opened. (Step S9) Overvoltage suppressing resistor 1 from the overhead wire side
The current supplied to 1 is cut off. As a result, overheating and burning of the overvoltage suppressing resistor 11 is prevented.

The opening operation command to the AC circuit breaker 2 is the output of the opening operation command to the AC switch 8 and the current detector 15.
However, the command output timing is set only in advance from the timing of the opening operation command output to the AC switch 8 in consideration of the time required to shut off the AC switch 8 in the normal state. Delay. Thereby, it is determined whether or not the AC switch 8 is not opened (NO in step S7).

Example 2. FIG. 3 is a diagram showing a main circuit configuration of an AC electric vehicle according to a second embodiment of the present invention. In this embodiment, the current detector 17 is provided on the AC side of the PWM converter 4, and the overvoltage suppressing resistor 11, the overvoltage suppressing thyristor 12, the overvoltage detector 13, and the current detector 17 constitute an overvoltage suppressing circuit 18. Here, after the overvoltage suppression protection operation by the ignition of the overvoltage suppression thyristor 12, when the AC switch 8 does not normally open due to a failure or the like, on condition that the output of the current detector 17 remains ON. The AC breaker 2 is opened.

Since a current detector is usually provided on the AC side of the PWM converter 4 for the purpose of converter control and overcurrent protection, these permanent current detectors can be used as the current detector 17. Therefore, there is an advantage that the cost is reduced accordingly.

Example 3. FIG. 4 is a diagram showing a main circuit configuration of an AC electric vehicle according to a third embodiment of the present invention. In this embodiment, a voltage detector 19 for detecting the voltage across the overvoltage suppressing resistor 11 is provided, and the overvoltage suppressing circuit is constituted by the overvoltage suppressing resistor 11, the overvoltage suppressing thyristor 12, the overvoltage detector 13 and the voltage detector 19. Make up 20. Here, after the overvoltage suppression protection operation by the ignition of the overvoltage suppression thyristor 12, if the AC switch 8 does not normally open due to a failure or the like, on condition that the output of the voltage detector 19 remains ON. The AC breaker 2 is opened.

For example, in the case of modifying the existing product by applying the present invention, it is necessary to add the above-mentioned current detector or voltage detector. However, in the former current detector, it is connected in series with the conducting conductor of the circuit. Although it is inserted, the latter voltage detector does not require such a connection, and a connection for contacting the circuit conductor in parallel is sufficient, and there is an advantage that the modification contents are generally simple.

Example 4. In each of the above-described embodiments, the case where the invention is applied to an AC electric vehicle has been described. However, since the circuit configuration of an AC / DC electric train is the same as that of an AC electric vehicle when traveling in the AC section, the present invention is not limited to this. Of course, it can be applied to the DC train in exactly the same manner, and in that case, the same effect as that of the above-described embodiment is obtained. Further, the cause of the overvoltage generated in the filter capacitor 5 is not limited to the disconnection of the pantograph, so the present invention is widely applied to a power conversion device including a converter and an inverter and further including the above-mentioned overvoltage suppressing circuit. The same effect can be achieved.

[0024]

As described above, according to the present invention, the current of the resistor of the overvoltage suppressing circuit is detected, and the AC circuit breaker is opened under the AND condition between the detection output and the AC switch opening operation command output. Therefore, even if the AC switch is not opened, overheating and burning of the resistor can be prevented.

Further, by detecting the AC side current of the converter,
Since the AC circuit breaker is opened under the AND condition between the detection output and the AC switch opening operation command output, overheating and burning of the resistor can be prevented even without the AC switch opening operation. Further, in this case, the required current detector has an advantage that it can be used also as a current detector required for other purposes.

Further, the voltage across the resistor of the overvoltage suppressing circuit is detected, and the AC circuit breaker is opened under the AND condition of this detection output and the AC switch opening operation command output. Therefore, the AC switch opening operation is performed. Without it, overheating and burning of the resistor is prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a main circuit configuration of an AC electric vehicle according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of overvoltage suppression protection of FIG.

FIG. 3 is a diagram showing a main circuit configuration of an AC electric vehicle according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a main circuit configuration of an AC electric vehicle according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a main circuit configuration of a conventional AC electric vehicle.

[Explanation of symbols]

 1 Pantograph 2 AC Breaker 4 PWM Converter 5 Filter Capacitor 6 PWM Inverter 7 Motor 8 AC Switch 11 Overvoltage Suppression Resistor 12 Overvoltage Suppression Thyristor 13 Overvoltage Detector 15, 17 Current Detector 16, 18, 20 Overvoltage Suppression Circuit 19 Voltage detector

Claims (3)

[Claims] 1. A converter connected to an AC power source via an AC circuit breaker, a capacitor connected to the DC side of the converter, an inverter connected between the capacitor and an AC load, and a voltage of the capacitor is predetermined. When the voltage exceeds the value of, the overvoltage suppressing circuit that suppresses the overvoltage of the capacitor by short-circuiting the capacitor through a resistor, and the operation of the overvoltage suppressing circuit that is connected between the AC power supply and the converter In a power conversion device equipped with an AC switch that opens after a lapse of time and shuts off the follow-up current from the AC power supply to the resistor, a current detector that detects the current of the resistor is provided, and the AC switch opens. If not, open the AC breaker under the AND condition of the output of the current detector and the output of the opening operation command of the AC switch. Power conversion apparatus characterized by the the like. 2. A converter connected to an AC power source via an AC circuit breaker, a capacitor connected to the DC side of the converter, an inverter connected between the capacitor and an AC load, and a voltage of the capacitor is predetermined. When the voltage exceeds the value of, the overvoltage suppressing circuit that suppresses the overvoltage of the capacitor by short-circuiting the capacitor through a resistor, and the operation of the overvoltage suppressing circuit that is connected between the AC power supply and the converter In a power conversion device equipped with an AC switch that opens after a lapse of time and shuts off the follow-up current from the AC power supply to the resistor, a current detector that detects the AC side current of the converter is provided, and the AC switch is opened. When not operating, the AC cutoff is made by ANDing the output of the current detector and the open operation command output of the AC switch. Power conversion device is characterized in that so as to open the. 3. A converter connected to an AC power source via an AC circuit breaker, a capacitor connected to the DC side of the converter, an inverter connected between the capacitor and an AC load, and a voltage of the capacitor being predetermined. When the voltage exceeds the value of, the overvoltage suppressing circuit that suppresses the overvoltage of the capacitor by short-circuiting the capacitor through a resistor, and the operation of the overvoltage suppressing circuit that is connected between the AC power supply and the converter In a power conversion device equipped with an AC switch that opens after a lapse of time and shuts off the follow-up current from the AC power supply to the resistor, a voltage detector that detects the voltage across the resistor is provided, and the AC switch is opened. When not operating, open the AC circuit breaker under the AND condition of the output of the voltage detector and the open operation command output of the AC switch. Power conversion apparatus characterized by the the to.