JP2980796B2 - 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 a power converter including, for example, a PWM converter and an inverter mounted on an AC or AC / DC electric vehicle, and more particularly to an overvoltage suppressing device.

[0002]

2. Description of the Related Art FIG. 5 shows a generally well-known PWM.
FIG. 3 is a diagram showing a main circuit configuration of an AC electric vehicle including a converter and an inverter, which is introduced in, for example, the 26th “Transactions on Cybernetics in the Railways Domestic Symposium” published on February 1990, pp. 191 to 195. . In the figure, 1 is a pantograph connected to an AC power supply by sliding on an overhead wire, 2 is an AC circuit breaker, 3 is a transformer, 4 is a bridge of an arm element composed of a GTO thyristor and a diode connected in anti-parallel thereto. 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 3-phase AC side of the PWM inverter 6. is there.

[0003] Reference numeral 8 denotes an AC switch connected and inserted between the transformer 3 and the PWM converter 4, and 9 and 10 denote a charging switch and a charging resistor respectively connected between both poles of the AC switch 8. 11 and 12 are overvoltage suppressing resistors and thyristors connected between both ends of the filter capacitor 5, respectively, and 13 is an overvoltage detector for detecting an overvoltage applied to the filter capacitor 5; Suppression circuit 14
Is configured.

Next, the operation will be described. High-voltage AC power from the AC power supply collected from the pantograph 1 is supplied to the primary winding of the transformer 3 through the AC circuit breaker 2. 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 operates to convert single-phase AC power to DC power and 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,
The power is converted into three-phase AC power of variable frequency to drive the electric motor 7 as an AC load. The PWM converter 4 and the PWM inverter 6 can perform not only a power running operation but also a regenerative braking operation.
From the pantograph 1 via the transformer 3 to the overhead line side.

When the load seen from the electric vehicle suddenly decreases due to a disconnection of the pantograph 1 or a sudden change in the load during the regenerative braking, and the voltage across the filter capacitor 5 becomes higher than usual, the PWM converter 4 and the PWM inverter 6 are turned off. An abnormal voltage is applied to the semiconductor element. Therefore, in order to prevent such adverse effects, the overvoltage suppression circuit 14
Is provided.

That is, when the voltage between both ends of the filter capacitor 5 becomes higher than a predetermined value, the overvoltage detector 13 detects this, and the overvoltage suppression thyristor 12 is fired by the detection output signal, so that the filter capacitor 5 is turned off. Short-circuiting occurs via the overvoltage suppressing resistor 11 to release the energy stored in the filter capacitor 5 to lower its voltage. If this state is left, PW
Since a current continues to flow through the diode of the M converter 4 to the overvoltage suppression resistor 11, the AC switch 8 is opened after a predetermined time has elapsed since the overvoltage suppression thyristor 12 is fired to interrupt the subsequent flow. Therefore, the heat capacity of the overvoltage suppressing resistor 11 is set to a relatively small value on the premise of the above operation.

[0007]

Since the overvoltage suppression circuit in the conventional electric vehicle is constructed as described above, the AC switch 8 is opened even if an open command is output due to a failure or the like. If the operation is not performed, the current continues to flow through the overvoltage suppressing resistor 11, and there is a problem that overheating and burning may occur and a serious accident may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Even if the AC switch does not normally open due to a failure or the like, the overvoltage suppression resistor may be overheated and burned. It is intended to obtain a highly reliable power converter.

[0009]

According to a first aspect of the present invention, there is provided a power conversion device including a current detector for detecting a current of a resistor of the power conversion device. The AC circuit breaker is opened under an AND condition between the output and the opening operation command output of the AC switch.

According to a second aspect of the present invention, the power converter includes a current detector for detecting an 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 circuit breaker is opened under an AND condition with the operation command output.

According to a third aspect of the present invention, the power converter includes a voltage detector for detecting a voltage between both ends of 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 circuit breaker is opened under an 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 despite the output of the opening operation command, the current detection for detecting the current of the resistor is performed. The AC circuit breaker opens the circuit under the condition of the output of the device and cuts off the flow to the resistor.

Further, in the power converter according to the present invention, when the AC switch does not normally perform the opening operation despite the output of the opening operation command, the current detection for detecting the AC side current of the converter. The AC circuit breaker opens the circuit under the condition of the output of the device and cuts off the flow to the resistor.

Further, in the power converter according to the third aspect, when the AC switch does not normally perform the opening operation despite the output of the opening operation command, the voltage detection detecting the voltage across the resistor. The AC circuit breaker opens the circuit under the condition of the output of the device and cuts off the flow to the resistor.

[0015]

[Embodiment 1] FIG. 1 is a diagram showing a main circuit configuration of an AC electric vehicle according to Embodiment 1 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. 15 constitutes an overvoltage suppression circuit 16.

Next, the voltage suppression protection operation when an overvoltage occurs in the filter capacitor 5 during the regenerative braking will be described with reference to the flowchart of FIG. The AC power generated from the electric motor 7 is converted to a PWM inverter 6 and a PWM
If the regenerative power absorbing ability is reduced due to the disconnection of the pantograph 1 or the like while the power is being regenerated to the overhead line via the converter 4 and the transformer 3, the filter capacitor 5
Voltage rises sharply. When this voltage exceeds a predetermined value, the overvoltage detector 13 detects this overvoltage (step S1), and outputs the PWM inverter 6 and the PWM converter 4
(Steps S2 and S3) to stop the regenerative braking operation and to set the overvoltage suppressing thyristor 12
Is fired (step S4), and the energy stored in the filter capacitor 5 is discharged via the overvoltage suppressing resistor 11 (step S5) to lower the voltage between both ends.

Simultaneously with the firing 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, after a lapse of a predetermined time from the firing of the overvoltage suppressing thyristor 12, an opening operation command is output to open the AC switch 8 (step S6). As a result, if the AC switch 8 is normally opened, there is no current flowing through the overvoltage suppressing resistor 11 (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 circuit breaker 2 is opened. (Step S9) Overvoltage suppression resistor 1 from overhead line side
The current supplied to 1 is interrupted. Thus, overheating of the overvoltage suppressing resistor 11 is prevented.

The opening operation command to the AC circuit breaker 2 includes the output of the opening operation command to the AC switch 8 and the current detector 15.
The timing of the command output is changed from the timing of the opening operation command output to the AC switch 8 by a time set in advance in consideration of the time required for the AC switch 8 to normally shut off. Delay. Thereby, it is substantially determined that the AC switch 8 is not open (NO in step S7).

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

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

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

For example, when modifying the existing product to apply the present invention, it is necessary to additionally install the above-described current detector or voltage detector, but in the former current detector, the current detector or the voltage detector is connected in series with the conducting conductor of the circuit. Although it is necessary to insert the voltage detector, the latter is not necessary, and only the connection for making parallel contact with the circuit conductor is sufficient, and there is an advantage that the remodeling content is generally simplified.

Embodiment 4 FIG. In each of the embodiments described above, the case where the present invention is applied to an AC electric vehicle has been described. However, the AC / DC train has the same circuit configuration as that of the AC electric vehicle when the AC section runs in the AC section. It is needless to say that the present invention can be applied to a DC train in exactly the same manner, and in this case, the same effect as that of the above embodiment can be obtained. Further, the cause of the occurrence of overvoltage in the filter capacitor 5 is not limited to the pantograph separation, so the present invention is widely applied to a power converter including a converter and an inverter and further including the above-described overvoltage suppression circuit. The same effect can be obtained.

[0024]

As described above, according to the present invention, the current of the resistor of the overvoltage suppression circuit is detected, and the AC circuit breaker is opened under the AND condition between the output of the detection and the command to open the AC switch. Therefore, even if there is no opening operation of the AC switch, overheating and burning of the resistor can be prevented.

Further, the AC side current of the converter is detected,
Since the AC circuit breaker is opened based on the AND condition between the detection output and the AC switch opening operation command output, overheating and burning of the resistor can be prevented without the opening operation of the AC switch. Further, in this case, there is an advantage that the necessary current detector can be used also as a current detector required for another use.

Further, since the voltage at both ends of the resistor of the overvoltage suppression circuit is detected and the AC circuit breaker is opened under an AND condition between the detection output and the command output of the opening operation of the AC switch, the opening operation of the AC switch is performed. The overheating and burning of the resistor can be prevented even without the above.

[Brief description of the 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. 1;

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 Embodiment 3 of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pantograph 2 AC circuit 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02M 7/42-7/98 B60L 3/00

Claims (3)

(57) [Claims] 1. A converter connected to an AC power supply via an AC circuit breaker, a capacitor connected to a DC side of the converter, an inverter connected between the capacitor and an AC load, and a voltage of the capacitor being predetermined. Over-voltage suppression circuit that suppresses over-voltage of the capacitor by short-circuiting the capacitor via a resistor when the value of the over-voltage suppression circuit is exceeded, and a predetermined voltage from the operation of the over-voltage suppression circuit connected between the AC circuit breaker and the converter. A power converter having an AC switch for opening after a lapse of time and interrupting a flow from the AC power supply to the resistor, comprising a current detector for detecting a current of the resistor, wherein the AC switch is opened. When not operating, the AC circuit breaker is opened according to the AND condition between the output of the current detector and the open operation command output of the AC switch. Power conversion device is characterized in that the so that. 2. A converter connected to an AC power supply via an AC circuit breaker, a capacitor connected to a DC side of the converter, an inverter connected between the capacitor and an AC load, and a voltage of the capacitor being predetermined. given from the operation of the connected the overvoltage suppression circuit between the overvoltage suppression circuit for suppressing overvoltage of the capacitors, and the AC circuit breaker and the converter by short-circuiting through resistors the capacitor when it exceeds the value A power conversion device including an AC switch that opens after a lapse of time to block a subsequent flow from the AC power supply to the resistor, includes a current detector that detects an AC side current of the converter, and the AC switch includes: When the opening operation is not performed, the AC interruption is performed by an AND condition between the output of the current detector and the opening operation command output of the AC switch. Power conversion device is characterized in that so as to open the vessel. 3. A converter connected to an AC power supply via an AC circuit breaker, a capacitor connected to a DC side of the converter, an inverter connected between the capacitor and an AC load, and a voltage of the capacitor being predetermined. given from the operation of the connected the overvoltage suppression circuit between the overvoltage suppression circuit for suppressing overvoltage of the capacitors, and the AC circuit breaker and the converter by short-circuiting through resistors the capacitor when it exceeds the value A power conversion device including an AC switch that opens after a lapse of time to block a subsequent flow from the AC power supply to the resistor, further comprising a voltage detector that detects a voltage across the resistor, wherein the AC switch is When the opening operation is not performed, the AC circuit breaker is activated by an AND condition between the output of the voltage detector and the opening operation command output of the AC switch. Power conversion device is characterized in that so as to release.