CURRENT BALANCE CONTROL FOR NON-INTERLEAVED PARALLEL BRIDGE CIRCUITS IN POWER CONVERTER

• US 20140204630A1
• Filed: 01/18/2013
• Published: 07/24/2014
• Est. Priority Date: 01/18/2013
• Status: Active Grant

• Current Assignee: GE Energy Power Conversion Technology Limited (General Electric Company)
• Original Assignee: General Electric Company
• Inventors: Wagoner, Robert Gregory, Klodowski, Anthony Michael
• Granted Patent: US 9,343,991 B2
• Time in Patent Office: Days
• US Class Current: 363/37
• CPC Class Codes: H02M 5/293 using semiconductor devices only
• CPC Class Codes: H02M 5/42 by static converters
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: H02P 2101/15 for wind-driven turbines
• CPC Class Codes: H02P 2207/073 wherein only one converter is used, the other windings being supplied without converter, e.g. doubly-fed induction machines
• CPC Class Codes: H02P 9/007 Control circuits for doubly fed generators

Abstract

Systems and methods for reducing current imbalance between parallel bridge circuits used in a power converter of a power generation system, such as a wind driven doubly fed induction generator (DFIG) system, are provided. The power converter can include a plurality of bridge circuits coupled in parallel to increase the output power capability of the system. Each of the bridge circuits can include a pair of switching elements, such as insulated gate bipolar transistors (IGBTs), coupled in series with one another. The switching elements of the parallel bridge circuits can be controlled, for instance, using control commands (e.g. pulse width modulation commands) according to a substantially non-interleaved switching pattern. The timing of the control commands according to the substantially non-interleaved switching pattern can be adjusted to reduce current imbalance between the parallel bridge circuits.

Claims

1. A power converter system, comprising:

a power converter, said power converter comprising a plurality of bridge circuits coupled in parallel, each bridge circuit comprising at least one switching element;

a control system configured to provide control commands to the switching elements of the plurality of bridge circuits to control pulse width modulation of the switching elements according to a substantially non-interleaved switching pattern, the control system further configured to adjust timing of the control commands to reduce current imbalance between the plurality of bridge circuits coupled in parallel.

2. The power converter system of claim 1, wherein the switching element comprises an insulated gate bipolar transistor (IGBT).

3. The power converter system of claim 1, wherein the power converter comprises a rotor side converter and a line side converter.

4. The power converter system of claim 1, wherein at least one inductive element is coupled between the plurality of bridge circuits.

5. The power converter system of claim 4, wherein the at least one inductive element comprises an output inductor coupled in series with a bridge output for each of the plurality of bridge circuits coupled in parallel.

6. The power converter system of claim 1, wherein the control system is configured to adjust the timing of the control commands according to a closed loop control process.

7. The power converter system of claim 6, wherein the closed loop control process monitors a bridge current of each of the plurality of bridge circuits coupled in parallel and adjusts the timing of the control commands based on the bridge current.

8. The power converter system of claim 1, wherein the control system is configured to adjust the timing of the control commands according to an open loop control process.

9. The power converter system of claim 1, wherein the power converter is coupled to a wind driven doubly fed induction generator.

10. The power converter system of claim 9, wherein said power converter is coupled to a rotor of said wind driven doubly fed induction generator.

11. A method of providing an output power to a load, comprising:

receiving, at a power converter, an alternating current power generated at a generator;

converting, with the power converter, the alternating current power to an output power, the power converter comprising a plurality of bridge circuits coupled in parallel, each bridge circuit comprising a pair of switching elements coupled in series with one another;

receiving control commands to control pulse width modulation of the switching elements according to a substantially non-interleaved switching pattern; and

adjusting the timing of the control commands to reduce current imbalance between the plurality of bridge circuits coupled in parallel.

12. The method of claim 11, wherein the method further comprises providing the output power to the load.

13. The method of claim 12, wherein the load comprises an electrical grid.

14. The method of claim 11, wherein the timing of the control commands is adjusted according to a closed loop control process.

15. The method of claim 14, wherein the closed loop control process comprises:

monitoring a bridge current of each of the plurality of bridge circuits coupled in parallel; and

adjusting the timing of the control commands based on the bridge current.

16. The method of claim 11, wherein the timing of the control commands is adjusted according to an open loop control process.

17. A doubly fed induction generator system, comprising:

a doubly fed induction generator configured to generate alternating current power;

a rotor side converter configured to receive the alternating current power and convert the alternating current power to a DC output;

a line side converter coupled to said rotor side converter via a DC link, the line side converter configured to receive the DC output from the rotor side converter and convert the DC power to an output power, at least one of the rotor side converter or the line side converter comprising a plurality of bridge circuits coupled in parallel, each bridge circuit comprising a pair of switching elements coupled in series with one another

a controller, said controller configured to provide control commands to control pulse width modulation of the switching elements of the plurality of bridge circuits according to a substantially non-interleaved switching pattern, the controller further configured to adjust the timing of the control commands to reduce current imbalance between the plurality of bridge circuits coupled in parallel.

18. The power converter of claim 17, wherein an inductive element is coupled between the plurality of bridge circuits coupled in parallel.

19. The power converter of claim 17, wherein the power converter comprises a plurality of current sensors, each current sensor configured to provide a signal indicative of a bridge current of one of the plurality of bridge circuits coupled in parallel.

20. The power converter of claim 19, wherein the controller is configured to adjust the timing of the control commands based at least in part on the signals indicative of the bridge current.