Power converter with voltage and current fault setting

• US 7,345,379 B2
• Filed: 11/30/2004
• Issued: 03/18/2008
• Est. Priority Date: 12/25/2003
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Okayama, Hideo, Fujii, Toshiyuki
• Primary Examiner(s): Sherry; Michael
• Assistant Examiner(s): DESCHERE, ANDREW M
• Application Number:
  US10/998,835
• Publication Number:
  US 20050141157A1
• Time in Patent Office: 1,204 Days
• Field of Search: 361/18, 361/79, 361/88, 361/90, 361/92, 361/93.2, 307/45, 307/46, 307/47, 307/103, 307/125, 307/130, 307/131, 363/55, 323/207
• US Class Current: 307/45
• CPC Class Codes: H02J 3/06 Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
• CPC Class Codes: H02J 3/1814 wherein al least one reactive element is actively controlled by a bridge converter, e.g. unified power flow controllers [UPFC]
• CPC Class Codes: Y02E 40/10 Flexible AC transmission systems [FACTS]

Abstract

A power converter includes a steady-state controller for outputting a first voltage command such that a detected power value matches a power command, a transient controller for outputting a second voltage command such that a voltage detected before the occurrence of a fault is maintained when the fault occurs, and a voltage command selector for switching the voltage command in such a way that the first voltage command is output when no power fault is detected and the sum of the first and second voltage commands is output when any power fault is detected.

Claims

1. A power converter comprising:

first and second terminals connected in series with a power line of a power system;

a power conversion circuit for outputting a voltage applied between said first and second terminals by converting power fed from an energy storage circuit;

first and second voltage sensors for detecting voltages at said first and second terminals, respectively;

a current sensor for detecting a current flowing from said first terminal to said second terminal;

a fault sensor for detecting the presence or absence of any voltage fluctuation fault at either of said first and second terminals based on sensing signals of said first and second voltage sensors and said current sensor;

a first controller for outputting a first voltage command for controlling the output voltage of said power conversion circuit such that a detected power value calculated from the sensing signals of said first and second voltage sensors and said current sensor matches a specific power command;

a second controller for outputting a second voltage command for controlling the output voltage of said power conversion circuit such that the voltage detected by one of said first and second voltage sensors remains the same as before the occurrence of a fault if said fault sensor detects the presence of the fault; and

a voltage command selector for switching the voltage command to be output to said power conversion circuit in such a way that the first voltage command is output to said power conversion circuit if said fault sensor detects the absence of the fault and the sum of the first and second voltage commands is output to said power conversion circuit if said fault sensor detects the presence of the fault.

2. The power converter according to claim 1, wherein said first controller includes:

an active power detecting circuit for determining the value of active power by multiplying the sensing signal of one of said first and second voltage sensors by the sensing signal of said current sensor; and

an active power control circuit for outputting the first voltage command for generating reactive power such that a deviation of the detected active power value from an active power command input into said active power control circuit becomes zero.

3. The power converter according to claim 1, wherein said first controller includes:

a reactive power detecting circuit for determining the value of reactive power by multiplying the sensing signal of one of said first and second voltage sensors by the sensing signal of said current sensor; and

a power factor control circuit for outputting the first voltage command for generating reactive power such that a deviation of the detected reactive power value from a reactive power command input into said power factor control circuit becomes zero, the reactive power command being set based on a target power factor.

4. The power converter according to claim 1, wherein said fault sensor outputs a fault signal including information on the presence or absence of any voltage fluctuation fault and information on whether the fault has occurred on the side of said first or second terminal;

and

wherein said second controller includes a voltage command polarity reversing circuit for reversing the polarity of the second voltage command which is output in response to the fault signal such that the voltage detected by the voltage sensor connected to one of said first and second terminals on which no fault is detected maintains the same level as before the occurrence of the fault when said fault sensor has output the fault signal.

5. The power converter according to claim 4, wherein a current change rate sensor is inserted between the first and second terminals in series with output terminals of said power conversion circuit;

and

wherein said fault sensor outputs the fault signal according to the polarity of the voltage detected by one of said first and second voltage sensors and the magnitude and polarity of an output of said current change rate sensor.

6. The power converter according to claim 1, wherein said first controller includes a current limitation control circuit for adding or subtracting a voltage limitation amount to or from the first voltage command depending on the polarity of the value of the current detected by said current sensor such that the absolute value of the detected current value decreases when this absolute value exceeds a specified value.

7. The power converter according to claim 1, wherein said power converter interconnects first and second power supplies with said first terminal connected to the first power supply and said second terminal connected to the second power supply.

8. The power converter according to claim 1, wherein said power converter connects a power supply to a load to which electric power is supplied from the power supply with said first terminal connected to the power supply and said second terminal connected to the load.