Multilevel inverters and methods of controlling multilevel inverters

• US 10,491,138 B1
• Filed: 02/07/2019
• Issued: 11/26/2019
• Est. Priority Date: 02/07/2019
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Rtx Corporation)
• Original Assignee: Hamilton Sundstrand Corporation (Rtx Corporation)
• Inventors: Thompson, Ernest, White, Adam Michael
• Primary Examiner(s): Nguyen, Matthew V
• Application Number:
  US16/270,068
• Time in Patent Office: 292 Days
• CPC Class Codes: H02M 1/0016 Control circuits providing compensation of output voltage deviations using feedforward of disturbance parameters
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/123 Suppression of common mode voltage or current
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/4833 Capacitor voltage balancing
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters

Abstract

A method of controlling an inverter includes generating a neutral-phase reference waveform, generating a neutral-phase midpoint compensation waveform using the neutral-phase reference waveform, and generating a neutral-phase compensated duty cycle waveform using the neutral-phase midpoint compensation waveform. Neutral-phase switch command signals are generated for switches of a neutral-phase of the inverter using the neutral-phase compensated duty cycle waveform. Inverters and computer program products are also described.

Claims

1. A method of controlling an inverter, comprising:

generating a neutral-phase reference waveform;

generating a neutral-phase midpoint compensation waveform using the neutral-phase reference waveform;

generating a neutral-phase compensated duty cycle waveform using the neutral-phase midpoint compensation waveform; and

generating neutral-phase switch command signals for switches of a neutral-phase of the inverter using the neutral-phase compensated duty cycle waveform.

2. The method as recited in claim 1, wherein the inverter has a neutral wire and M-phases, M being greater than or equal to 3.

3. The method as recited in claim 1, wherein generating a neutral-phase reference waveform comprises generating phase reference waveforms for each phase of the inverter.

4. The method as recited in claim 1, wherein generating a neutral-phase reference waveform comprises generating the neutral-phase reference waveform using a pulse-density modulation technique.

5. The method as recited in claim 1, wherein generating a neutral-phase midpoint compensation waveform comprises generating a phase midpoint compensation waveform for each phase of the inverter.

6. The method as recited in claim 1, wherein generating a neutral-phase compensated duty cycle waveform comprises generating a phase compensated duty cycle waveform for each phase of the inverter.

7. The method as recited in claim 1, wherein generating a neutral-phase compensated duty cycle waveform comprises subtracting one-half the neutral-phase reference waveform from a minimum of 0 and the neutral-phase reference waveform.

8. The method as recited in claim 1, wherein generating a neutral-phase compensated duty cycle waveform comprises adding one-half the neutral-phase reference waveform to a maximum of 0 and the neutral-phase reference waveform.

9. The method as recited in claim 1, wherein generating neutral-phase switch command signals for switches of a neutral-phase of the inverter comprises generating phase switch command signals for switches of each phase of the inverter using a phase compensated duty cycle waveform for each phase of the inverter.

10. The method as recited in claim 1, further comprising connecting each phase of the inverter to a midpoint rail for equivalent periods of time during switching cycles of the inverter.

11. The method as recited claim 1, further comprising:

receiving direct current (DC) at the inverter; and

inverting the DC power into alternating current (AC) power using the neutral-phase switch command signals.

12. A multilevel inverter, comprising:

a neutral-phase with a plurality of switches;

a direct current (DC) midpoint rail connected to the switches; and

a controller operatively connected to the plurality of switches and disposed in communication with a memory having instructions recorded thereon that, when read by the controller cause the controller to;

generate a neutral-phase reference waveform;

generate a neutral-phase midpoint compensation waveform using the neutral-phase reference waveform;

generate a neutral-phase compensated duty cycle waveform using the neutral-phase midpoint compensation waveform; and

generate neutral-phase switch command signals for switches of a neutral-phase of the inverter using the neutral-phase compensated duty cycle waveform.

13. The inverter as recited in claim 12, wherein the inverter has a neutral wire and M-phases, M being greater than or equal to 3, and wherein the instructions further cause the controller to:

generate phase reference waveforms for each phase of the inverter;

generate a phase midpoint compensation waveform for each phase of the inverter using the phase reference waveforms;

generate a phase compensated duty cycle waveform for each phase of the inverter using the phase midpoint compensation waveforms; and

generate phase switch command signals for switches of each phase of the inverter using a phase compensated duty cycle waveform for each phase of the inverter.

14. The inverter as recited in claim 12, wherein the inverter has a neutral wire and M-phases, M being greater than or equal to 3, and wherein the instructions further cause the controller to connect each phase of the inverter to a midpoint rail for equivalent periods of time during switching cycles of the inverter phases.

15. The inverter as recited in claim 12, further comprising a multilevel DC link connected to the inverter.

16. The inverter as recited in claim 12, further comprising a rectifier connected to the inverter.

17. The inverter as recited in claim 16, further comprising a variable frequency AC power source connected to the inverter by the rectifier.

18. The inverter as recited in claim 16, further comprising an AC bus connected to the inverter, the AC bus comprising an A-phase lead, a B-phase lead, a C-phase lead, and a neutral-phase lead.

19. A computer program product tangibly embodied on a computer readable medium, the computer program product including instructions that, when executed by a processor, cause the processor to perform operations comprising:

generating a neutral-phase reference waveform;

generating a neutral-phase midpoint compensation waveform using the neutral-phase reference waveform;

generating a neutral-phase compensated duty cycle waveform using the neutral-phase midpoint compensation waveform; and

generating neutral-phase switch command signals for switches of a neutral-phase of the inverter using the neutral-phase compensated duty cycle waveform.

20. The computer program product of claim 19, wherein the instructions cause the processor to further perform the operation:

connecting each phase of the inverter to a midpoint rail for equivalent periods of time during switching cycles of the inverter phases.