Variable-speed wind power system with improved energy capture via multilevel conversion

• US 20040022081A1
• Filed: 05/30/2003
• Published: 02/05/2004
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Alliance For Sustainable Energy LLC
• Original Assignee: Lee Jay Fingersh, Osama A. Al-Naseem, Robert W. Erickson
• Inventors: Erickson, Robert W., Fingersh, Lee Jay, Al-Naseem, Osama A.
• Granted Patent: US 6,900,998 B2
• Time in Patent Office: Days
• US Class Current: 363/159
• CPC Class Codes: H02M 5/297 for conversion of frequency
• CPC Class Codes: H02M 7/4835 comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

A system and method for efficiently capturing electrical energy from a variable-speed generator are disclosed. The system includes a matrix converter using full-bridge, multilevel switch cells, in which semiconductor devices are clamped to a known constant DC voltage of a capacitor. The multilevel matrix converter is capable of generating multilevel voltage wave waveform of arbitrary magnitude and frequencies. The matrix converter can be controlled by using space vector modulation.

Claims

1. A matrix converter, comprising:

a plurality of input ends;

a plurality of output ends; and

a plurality of multilevel switch cells,

each one of the plurality of input ends being electrically linked to each one of the plurality of output ends via at least one of the plurality of multilevel switch cells.

2. The matrix converter of claim 1, further comprising a plurality of inductors, wherein each of the plurality of input and output ends is electrically connected to at least one of the plurality of inductors.

3. The matrix converter of claim 1, wherein each of the plurality of multilevel switch cells comprises:

a full bridge inverter, comprising

a first and second terminals,

a positive and negative nodes, and

four inverter arms, each arm comprising a diode having a positive pole and a negative pole, and a transistor having a gate, an emitter and collector, with the emitter electrically connected to the negative pole and the collector electrically connected to the positive pole, a first and second of the four inverter arms being electrically connected to the positive node to the first and second terminal, respectively, and a third and fourth of the four inverter arms being electrically connected to the negative node to the first and second terminal, respectively, with the diode in each of the four arms forwardly directed toward the positive node; and

a capacitor electrically connected between the positive and negative nodes.

4. The matrix converter of claim 3, further comprising a plurality of inductors, wherein each of the plurality of input and output ends is electrically connected to at least one of the plurality of inductors.

5. The matrix converter of claim 1, wherein each one of the plurality of input ends being electrically linked to each one of the plurality of output ends via at least two of the plurality of multilevel switch cells.

6. The matrix converter of claim 5, wherein the at least two switch cells are electrically connected in series with each other.

7. The matrix converter of claim 5, wherein the at least two switch cells are electrically connected in parallel with each other.

8. The matrix converter of claim 1, further comprising a controller electrically connected to the switch cells and adapted to change the electrical potential difference between at least one of the plurality of output ends and at least one of the plurality of input ends.

9. The matrix converter of claim 3, further comprising a controller electrically connected to the gates of the transistors adapted to turn the transistors off and on.

10. The matrix converter of claim 8, wherein the controller is a pulse width modulator.

11. An electrical power generator, comprising:

an energy conversion unit having a plurality of output ends and adapted to convert non-electrical energy into multi-phase ac electricity and to supply each phase of the electricity to a respective one of the plurality of output ends; and

a matrix converter of claim 1, at least a subset of the plurality of the input ends of the matrix converter being electrically connected to the output ends of the energy conversion unit.

12. The generator of claim 11, wherein the energy conversion unit is a variable-speed wind turbine.

13. A method of synthesizing a voltage, the method comprising:

providing an input multi-phase ac electrical voltage;

applying each of the input ac electrical voltage to a respective one of a plurality of input ends of a matrix converter, which comprises;

a plurality of output ends, and

a plurality of multilevel switch cells,

each one of the plurality of input ends being electrically linked to each one of the plurality of output ends via at least one of the plurality of multilevel switch cells; and

controlling the voltages at the plurality of output ends.

14. The method of claim 13, wherein each of the plurality of multilevel switch cells comprises

a full bridge inverter, comprising:

a first and second terminals,

a positive and negative nodes, and

four inverter arms, each arm comprising a diode having a positive pole and a negative pole, and a transistor having a gate, an emitter and collector, with the emitter electrically connected to the negative pole and the collector electrically connected to the positive pole, a first and second of the four inverter arms being electrically connected to the positive node to the first and second terminal, respectively, and a third and fourth of the four inverter arms being electrically connected to the negative node to the first and second terminal, respectively, with the diode in each of the four arms forwardly directed toward the positive node; and

a capacitor electrically connected between the positive and negative nodes and

the step of changing the electrical potential difference comprises changing the on/off state of at least one of the transistors.

15. The method of claim 13, wherein the step of controlling the voltages comprises modulating the voltages at an output end of the matrix converter by pulse-width modulation.

16. The method of claim 15, wherein the modulating step comprises space vector modulation.

17. The method of claim 13, wherein each one of the plurality of input ends being electrically linked to each one of the plurality of output ends via at least two of the plurality of multilevel switch cells in parallel with each other, and further comprising turning off one of the at least two switch cells while keeping the other of the two on.

18. The method of claim 17, wherein the step of apply the input voltages comprises electrically connecting the matrix converter to a wind turbine electric generator, and turning off one of the at least two switch cells while keeping the other of the two on when the wind turbine rotate at a speed below a predetermined value.

19. An electrical system, comprising:

a first multi-phase ac system having a first plurality of terminals, each of which is adapted to conduct electricity of one of a first plurality of phases to or from the first multi-phase ac system;

a second multi-phase ac system having a second plurality of terminals, each of which is adapted to conduct electricity of one of a second plurality of phases to or from the second multi-phase ac system; and

a plurality of multilevel matrix converters, each of which comprising;

a plurality of input ends,

a plurality of output ends, and

a plurality of multilevel switch cells,

each one of the plurality of input ends being electrically linked to each one of the plurality of output ends via at least one of the plurality of multilevel switch cells,

at least a subset of the plurality of the input ends of each matrix converter being electrically connected to the first plurality of terminals of the first multi-phase ac system, and

at least a subset of the plurality of the output ends of each matrix converter being electrically connected to the second plurality of terminals of the first multi-phase ac system.

20. The electrical system of claim 20, wherein the first ac system comprises a variable-speed wind turbine generator, and the second ac system comprises a utility grid.