Methods and apparatus for three-phase inverter with reduced energy storage

• US 7,839,023 B2
• Filed: 11/08/2007
• Issued: 11/23/2010
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Jacobson, Boris S., Holmansky, Evgeny N.
• Primary Examiner(s): KAPLAN, HAL IRA
• Application Number:
  US11/936,896
• Publication Number:
  US 20090021081A1
• Time in Patent Office: 1,111 Days
• Field of Search: 307/77, 307/82, 323/266, 363/43, 363/132
• US Class Current: 307/77
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 7/4826 operating from a resonant DC source, i.e. the DC input voltage varies periodically, e.g. resonant DC-link inverters
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Methods and apparatus for a circuit including first and second energy sources, a rectifier coupled to the first and second energy sources, first and second energy storage devices coupled end-to-end across the positive and negative rails, and a single three-level inverter coupled to the rectifier for providing three-phase sinusoidal output voltages.

Claims

1. A circuit, comprising:

first and second energy sources coupled in series, the first energy source including a first DC-DC converter that generates a first modulated DC waveform on a first energy storage device coupled to the first energy source, the second energy source including a second DC-DC converter that generates a second modulated DC waveform on a second energy storage device coupled to the second energy source, wherein the first DC-DC converter is operably coupled in series with the second DC-DC converter to form a positive rail, a negative rail, and a neutral; and

a single multi-level inverter coupled to the positive rail, negative rail, and neutral, the multi-level inverter configured to unfold and sum the first and second modulated DC waveforms to produce three-phase sinusoidal output voltages.

2. The circuit according to claim 1, wherein the first and second DC-DC converters comprise respective first and second current source DC-DC converters.

3. The circuit according to claim 2, wherein the first and second energy storage devices are capacitive;

the first energy storage device is coupled end-to-end across the positive rail and the neutral; and

the second energy storage device is coupled end-to-end across the negative rail and the neutral.

4. The circuit according to claim 1, wherein the three-phase output signals are at a frequency of about 60 Hz.

5. The circuit according to claim 1, wherein the three-phase output signals are at a frequency of about 50 Hz.

6. The circuit according to claim 1, wherein the three-phase output signals are at a frequency of about 400 Hz.

7. The circuit according to claim 1, wherein the frequency of the three-phase output signals varies from zero to a predetermined maximum frequency.

8. The circuit according to claim 1, wherein the inverter includes switches to commutate once per cycle of the output frequency.

9. The circuit according to claim 3, wherein the voltages of the first and second capacitive energy storage devices are described as follows:

10. The circuit according to claim 1, wherein the multi-level inverter output phase voltages are described as follows:

11. The circuit according to claim 1, wherein the first and second energy sources are bidirectional.

12. The circuit of claim 1, wherein the inverter operates at an output frequency and includes switches to commutate once per cycle of the output frequency according to the table that follows:

13. A method comprising:

coupling first and second energy sources in series, the first energy source including a first DC-DC converter and the second energy source including a second DC-DC converter, wherein the first DC-DC converter is operably coupled in series with the second DC-DC converter to form a positive rail, a negative rail, and a neutral;

coupling first and second energy storage devices to the first and second energy sources, such that the first energy storage device is coupled end-to-end across the positive rail and the neutral, and the second energy storage device is coupled end-to-end across the negative rail and the neutral;

generating a first modulated DC voltage waveform on the first energy storage device and a second modulated DC voltage waveform on the second energy storage device;

coupling a single three-level inverter to the positive rail, negative rail, and neutral; and

unfolding and summing the first and second modulated DC waveforms to produce three-phase sinusoidal output voltages at outputs of the three-level inverter.

14. The method according to claim 13, wherein the first and second energy sources are current sources.

15. The method according to claim 13, wherein the first and second energy storage devices are capacitors.

16. The method according to claim 13, wherein the three-phase output signals are at a frequency of about 60 Hz.

17. The method according to claim 13, wherein the three-phase output signals are at a frequency of about 50 Hz.

18. The method according to claim 13, wherein the three-phase output signals are at a frequency of about 400 Hz.

19. The method according to claim 13, wherein the frequency of the three-phase output signals varies from zero to a predetermined maximum frequency.

20. The method according to claim 13, wherein the voltages of the first and second energy storage devices are described as follows:

21. The method according to claim 13, wherein the inverter operates at an output frequency and includes switches to commutate once per cycle of the output frequency.

22. The method according to claim 13, wherein the inverter operates at an output frequency and includes switches to commutate once per cycle of the output frequency according to the table that follows:

23. The method according to claim 13, wherein the multi-level inverter output phase voltages result from summation of two voltages V_C1, V_C2 and are described as follows:

24. The method of claim 13, further comprising:

configuring the single three-level inverter to unfold and sum the first and second modulated DC waveforms to produce the three-phase sinusoidal output voltages.

25. A method for generating a three-phase output voltage, the method comprising:

providing a first energy source comprising a first DC-DC converter that generates a first modulated DC waveform and a second energy source comprising a second DC-DC converter that generates a second modulated DC waveform, wherein each DC waveform comprises two or more segments, with each segment corresponding to a predetermined portion of a fundamental frequency sinusoid;

coupling the first energy source in series with the second energy source to form a positive rail, a neutral, and a negative rail;

coupling a first energy storage device between the positive rail and the neutral, such that the first energy source generates the first modulated DC waveform on the first energy storage device;

coupling a second energy storage device between the negative rail and the neutral, such that the second energy source generates the second modulated DC waveform on the second energy storage device;

coupling a multi-level inverter to the positive rail, neutral, and negative rail;

configuring the multi-level inverter to unfold and sum each of the first and second modulated DC waveforms in accordance with a predetermined switching scheme; and

generating three-phase sinusoidal output voltages at the multi-level inverter outputs.

26. The method of claim 25, wherein the predetermined portion comprises a 60°

segment of the fundamental frequency sinusoid.

27. The method of claim 25, wherein the multi-level inverter operates at an output frequency and includes a plurality of switches configured to operate in accordance with the predetermined switching scheme, which involves commutating the switches once per cycle of the output frequency according to the following table:

28. The method of claim 25, further comprising distributing voltages associated with the first modulated DC waveform and the second modulated DC waveform between output phases of the multi-level inverter, to generate output voltages according to the table that follows: