Modular multi-level adjustable supply with parallel connected active inputs

• US 6,301,130 B1
• Filed: 08/15/2000
• Issued: 10/09/2001
• Est. Priority Date: 09/01/1999
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Robicon Corp. (Siemens AG)
• Inventors: Rastogi, Mukul, Aiello, Marc F., Hammond, Peter W.
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/637,368
• Time in Patent Office: 420 Days
• Field of Search: 363/34, 363/37, 363/39, 363/40, 363/44, 363/47, 363/48, 363/65, 363/67, 363/68, 363/69, 363/70, 363/71
• US Class Current: 363/37
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters

Abstract

An improvement in a power drive is disclosed that allows four quadrant operation with reduced harmonics. The power drive has a multiphase, non phase shifted transformer with a single common input connected inductive reactance. Multiple series connected power cells are utilized, each configured for four quadrant operation and having a multiphase input and a single phase output, each controllable to reduce harmonics in both the input source line and the output line. Each power cell includes a three phase input converter, a smoothing filter, and a single phase output converter. A method for operating the power drive includes the steps of selectively controlling switching events at the input and output of each power cell such that switching events in respective power cells are spaced apart in time thereby reducing harmonic components. The method can be implemented using pulse width modulation control based upon interdigitated carrier signals which control the input and output of each power cell.

Claims

1. A reduced harmonics power drive for a multi-phase AC load comprising:

a multi-phase power transformer having at least one primary winding circuit and a plurality of secondary winding circuits, said primary winding circuit electrically connectable to a multi-phase AC power source;

a plurality of power cells, each of said power cells comprising;

a controllable multi-phase input connected to a respective one of said plurality of secondary winding circuits;

a smoothing filter; and

a controllable single-phase output to said multi-phase AC load; and

a modulation controller connected to each of said plurality of power cells, said modulation controller selectively controlling a series of switching events in said controllable multi-phase input such that one of said input phases of each of said power cells is switched simultaneously with corresponding input phases of all other power cells to reduce harmonics in input lines from said power source.

2. The power drive of claim 1 wherein said single phase output of a subset of said plurality of power cells are used in each phase output to said multi-phase AC load, said power cells in each of said subsets being connected serially.

3. The power drive of claim 1 wherein said modulation controller uses a common modulation signal to control said multi-phase input of each of said plurality of power cells.

4. The power drive of claim 1 wherein said switching events for any phase input of said controllable multi-phase input for each of said power cells is temporally separated from said switching events for all other phase inputs of said controllable multi-phase input for each of said power cells.

5. The power drive of claim 1 wherein said switching events for said controllable single phase output of each of said plurality of power cells in each phase output line are temporally spaced from each other, thereby reducing harmonic components in lines to said AC load.

6. The power drive of claim 5 wherein said controllable single phase output comprises a plurality of semiconductor switches arranged in an H-bridge configuration, said plurality of semiconductor switches being operably connected to said smoothing filter and said controllable multi-phase input, and each of said plurality of semiconductor switches being connected to said modulation controller.

7. The power drive of claim 1 wherein said a multi-phase power transformer further comprises:

a plurality of yoke members, one of which is provided between said primary and each of said plurality of secondary winding circuits;

at least one winding connecting said primary and said plurality of secondary winding circuits;

a plug member connecting said each of said plurality of yoke members;

a first end cap provided at a primary winding circuit side of said transformer and a second end cap provided at a secondary winding circuit side of said transformer to complete both magnetic circuits of said common magnetic structure; and

an air gap between said first end cap and said plurality of yoke members.

8. The power drive of claim 1 wherein said plurality of secondary winding circuits have no phase shift with respect to each other, further comprising a multi-phase brake resistor combination connected to said primary winding to brake said load upon loss of input voltage.

9. The power drive of claim 1 wherein each of said input phases of said controllable multi-phase input includes a pair of IGBTs having an input function pole connected to said modulation controller, and further wherein said modulation controller modulates each of said poles using an identical modulation function to control said switching events.

10. The power drive of claim 1 wherein all of said secondary winding circuits are in phase with each other.

11. The power drive of claim 1 wherein each of said secondary winding circuits has the lowest possible secondary leakage reactance.

12. The power drive of claim 11 wherein said secondary leakage reactance of each of said secondary winding circuits is less than or equal to four percent.

13. The power drive of claim 1 wherein said smoothing filter is connected between said controllable multi-phase input and said controllable single phase output.

14. The power drive of claim 1 wherein said plurality of secondary winding circuits have no phase shift with respect to each other, further comprising a single multi-phase line reactor connected to said primary winding circuit for providing a common reactance to each of said controllable multi-phase inputs.

15. The power drive of claim 14 wherein said multi-phase line reactor is combined into a common magnetic structure with said primary winding circuit.

16. The power drive of claim 14 further comprising a multi-phase line reactor and resistor damped capacitor filter connected to said primary winding circuit to further reduce input current distortion.

17. The power drive of claim 1 wherein said smoothing filter comprises at least one capacitor.

18. The power drive of claim 1 wherein said smoothing filter has an impedance sufficiently large to a pulsating output current such as to force current cancellation between magnetically paralleled inputs of said power cells, thereby minimizing filter capacitor ripple current and voltage.

19. A reduced harmonics power drive for a multi-phase AC load comprising:

a multi-phase power transformer having at least one primary winding circuit, and a plurality of secondary winding circuits, each of said secondary winding circuits having associated therewith a leakage reactance;

a plurality of power cells, each of said power cells comprising;

a controllable multi-phase input connected to a respective one of said plurality of secondary winding circuits;

a smoothing filter; and

a controllable single-phase output to said multi-phase AC load; and

a modulation controller connected to each of said plurality of power cells;

wherein said modulation controller selectively controls a series of switching events in said controllable multi-phase input and said controllable single phase output of each of said plurality of power cells to reduce harmonics in input lines from said power source and in output lines to said load; and

wherein said smoothing filter of each of said power cells is matched to said leakage reactance of the secondary winding circuit connected to a respective power cell, such that the resonant frequency between said secondary leakage reactance and said capacitance of said smoothing filter is greater than the frequency of the output power.

20. The power drive of claim 19 wherein said resonant frequency is at least two times the frequency of the output power.

21. A reduced harmonics power drive for a multi-phase AC load comprising:

a multi-phase power transformer comprising;

at least one primary winding circuit said primary winding circuit electrically connectable to a multi-phase AC power source;

a plurality of secondary winding circuits, said secondary winding circuits having no phase shift with respect to each other; and

a single multi-phase line reactor connected to said primary winding circuit;

a plurality of power cells, each of said power cells comprising;

a controllable multi-phase input comprising a multi-phase input bridge connected to a respective one of said plurality of secondary winding circuits;

a smoothing filter; and

a controllable single phase output to said multi-phase AC load; and

a modulation controller connected to each of said plurality of power cells;

wherein one of said input phases of each of said power cells is switched by said modulation controller simultaneously with corresponding input phases of all other power cells; and

wherein said single multi-phase line reactor provides a common reactance to each of said controllable multi-phase inputs of said plurality of power cells.

22. The power drive of claim 21 wherein each of said secondary winding circuits has a leakage reactance associated therewith and said smoothing filter of each of said power cells has a capacitance and further wherein the capacitance of said smoothing filter of each of said power cells is matched to said leakage reactance of the secondary winding circuit connected to a respective power cell, such that the resonant frequency between said secondary leakage reactance and said capacitance of said smoothing filter is greater than the frequency of the output power.

23. In a power drive having a multi-phase power transformer a plurality of power cells each having a plurality of phase input poles and a modulation controller connected to each of said plurality of power cells, a method for enabling four quadrant operation while reducing harmonics comprising the steps of:

providing a common reactance, connected to a primary winding of said multi-phase power transformer, for each of said power cells;

switching said input poles of said power cells in parallel with the corresponding input poles of all other power cells, but temporally spaced from other input poles in the same power cell;

providing a plurality of secondary windings on said multi-phase power transformer, said secondary windings having a leakage reactance; and

providing a capacitive element as a smoothing filter for each of said power cells and matching said capacitance of each of said smoothing filters with said leakage reactance of said secondary windings, such that the resonant frequency between said secondary leakage reactance and said capacitance of said smoothing filter is greater than the frequency of the output power.