POWER CONVERSION DEVICE

• US 20130003429A1
• Filed: 02/25/2010
• Published: 01/03/2013
• Est. Priority Date: 02/25/2010
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Murahashi, Akihiro
• Granted Patent: US 8,988,909 B2
• Time in Patent Office: Days
• US Class Current: 363/56.01
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: B60L 9/22 polyphase motors
• CPC Class Codes: G01R 31/42 AC power supplies
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G01R 31/64 Testing of capacitors
• CPC Class Codes: H02H 7/16 for capacitors for synchronous capacitors H02H7/06
• CPC Class Codes: H02M 1/322 Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode

Abstract

A power conversion device includes a main circuit unit (direct-current main circuit) that converts direct-current power into alternating-current power, and a control unit that controls the direct-current main circuit. The direct-current main circuit includes a voltage detector (detector) that detects a capacitor voltage and a discharge circuit that discharges energy accumulated in a capacitor. The control unit includes a detection circuit that estimates a capacitor voltage during a normal operation based on a voltage transmitted from the voltage detector in a state where the main circuit unit is disconnected from a power supply and that detects a sign that a short circuit fault occurs in the capacitor, and a control circuit that outputs a control signal for controlling the discharge circuit to operate when the control circuit receives a detection signal from the detection circuit.

Claims

1. A power conversion device comprising:

a direct-current main circuit that converts direct-current power into alternating-current power; and

a control unit that controls the direct-current main circuit, wherein

the direct-current main circuit includes

a capacitor that constitutes the direct-current main circuit, a detector that detects a voltage of the capacitor, and a first discharge circuit that includes the capacitor and a first resistor, and that discharges electric charge accumulated in the capacitor via the first resistor, and

the control unit includes a detection circuit that compares a transition of a voltage estimated based on an initial voltage detected by the detector at a time of disconnecting the direct-current main circuit from a power supply and on a time constant of the first discharge circuit with a transition of a voltage detected by the detector, and that generates a detection signal indicating a sign that a short circuit fault occurs in the capacitor, and the control unit disconnects the direct-current main circuit from the power supply when the direct-current main circuit is not disconnected from the power supply for a predetermined period of time.

2. The power conversion device according to claim 1, wherein

the direct-current main circuit includes a second discharge circuit that includes a second resistor and that discharges electric charge accumulated in the capacitor via the second resistor, and

the control unit includes a control circuit that controls the second discharge circuit to operate when the control circuit receives a detection signal from the detection circuit.

6. The voltage conversion device according to claim 1, wherein the detection circuit latches a detection state when the detection circuit detects an abnormality of the capacitor.

7. The power conversion device according to claim 1, wherein the detection circuit notifies outside that the detection circuit has detected a sign that a short circuit fault occurs in the capacitor.

3. A power conversion device comprising:

a direct-current main circuit that converts direct-current power into alternating-current power; and

a control unit that controls the direct-current main circuit, wherein

the direct-current main circuit includes

a capacitor that constitutes the direct-current main circuit, a detector that detects a voltage of the capacitor, and a first discharge circuit that includes the capacitor and a first resistor, and that discharges electric charge accumulated in the capacitor via the first resistor, and

the control unit includes a detection circuit that generates a detection signal indicating a sign that a short circuit fault occurs in the capacitor based on a gradient of an instant decrease for a period of time since the voltage detected by the detector at a time of disconnecting the direct-current main circuit from a power supply drops from a steady state until the voltage detected by the detector rises again to be closer to the steady state.

4. The power conversion device according to claim 3, wherein a detection level of the detection circuit at which the detection circuit detects the instant decrease in the voltage detected by the detector is set between a voltage decrease rate during occurrence of the instant short circuit in the capacitor and a voltage decrease rate that possibly occurs during a normal operation.

5. The power conversion device according to claim 3, wherein

the direct-current main circuit includes a second discharge circuit that includes a second resistor and that discharges electric charge accumulated in the capacitor via the second resistor, and

the detection circuit masks a detecting function of detecting a decrease in the voltage only when a voltage decrease rate when the second discharge circuit operates is substantially equal to a voltage decrease rate during occurrence of an instant short circuit in the capacitor.

8. The power conversion device according to claim 3, wherein the control circuit disconnects the direct-current main circuit from a power supply when the direct-current main circuit is not disconnected from the power supply for a predetermined period of time.

9. The power conversion device according to claim 3, wherein the detection circuit latches a detection state when the detection circuit detects an abnormality of the capacitor.

10. The power conversion device according to claim 3, wherein the detection circuit notifies outside that the detection circuit has detected a sign that a short circuit fault occurs in the capacitor.