VERSATILE CYCLOINVERTER POWER CONVERTER CIRCUITS

• US 3,742,336 A
• Filed: 11/24/1971
• Issued: 06/26/1973
• Est. Priority Date: 11/24/1971
• Status: Expired due to Term

• Current Assignee: Burnice D. Bedford
• Original Assignee: Burnice D. Bedford
• Inventors: Bedford, Burnice D.
• Primary Examiner(s): Shoop, Jr., William M.
• Application Number:
  US05/201,673
• Time in Patent Office: 580 Days
• Field of Search: 321/5,7,69
• US Class Current: 363/1
• CPC Class Codes: H02M 5/271 from a three phase input voltage
• CPC Class Codes: H02M 7/515 using semiconductor devices only

Abstract

A family of high-frequency-link solid state power converters having an input and output switching circuit that function as a high frequency parallel capacitor commutated control inverter and a cycloconverter output circuit to supply variable frequency and variable voltage power to a load. The tuned commutation circuit for the inverter switches, preferably thyristors, includes commutating inductance in parallel with the commutation capacitor. By operating the inverter at a variable frequency greater than the resonant frequency, the commutating energy or commutating angle changes as a function of the load. The cycloconverter switches are phase controlled with respect to the high frequency inverter voltages. Depending on the circuit configuration, a-c or d-c supply voltage is converted to polyphase a-c, single phase a-c, or d-c output voltage, and power flow in either direction can be obtained. An application is a variable speed a-c motor drive.

Claims

1. A versatile power converter circuit comprising a first switching circuit including a plurality of solid state switches for converting an electric potential to a higher frequency voltage wave, a second switching circuit including a plurality of phase controlled solid state switches for converting the higher frequency voltage wave to a desired output voltage waveform, tuned parallel capacitor commutation circuit means for supplying a controlled variable amount of commutation energy for turning off said solid state switches in said switching circuits, said commutation circuit means comprising a commutation capacitor and parallel commutating inductance means tuned to a predetermined constant resonant frequency, and control means for operating said first and second switching circuits in synchronism.

2. A circuit according to claim 1 wherein said control means operates said switching circuits and said tuned parallel capacitor commutation circuit means at a selected operating frequency greater than the resonant frequency, to thereby increase the amount of commutating energy as the operating frequency is increaseD.

3. A circuit according to claim 1 wherein said control means operates said switching circuits and said tuned parallel capacitor commutation circuit means at a substantially constant operating frequency, and said commutation circuit means further includes variable auxiliary parallel commutating inductance means for controlling the amount of commutating energy available from said commutation circuit means.

4. A circuit according to claim 3 wherein said first and second switching circuits are cycloconverter configuration circuits and said commutation circuit means is coupled therebetween.

5. A circuit according to claim 3 wherein said first and second switching circuits are polyphase cycloconverter circuits, and said commutation circuit means is coupled therebetween, said power converter circuit being operative to convert a polyphase electric potential to a variable frequency, variable voltage output waveform.

6. A versatile power converter circuit comprising a first switching circuit including a plurality of solid state switches for converting an electric potential to a high frequency voltage wave as compared to the frequency of a desired output voltage waveform, a second switching circuit including a plurality of solid state switches that are phase controlled to convert the high frequency voltage wave to the desired output voltage waveform, tuned parallel capacitor commutation circuit means connected in said first switching circuit for supplying a controlled variable amount of commutating energy for turning off said solid state switches in said switching circuits, said commutation circuit means comprising a commutation capacitor and parallel commutating inductance means tuned to a predetermined constant resonant frequency, and control means for operating said switching circuits in synchronism at a variable operating frequency greater than said resonant frequency to thereby vary the net capacitive reactance of said commutation circuit means.

7. A circuit according to claim 6 wherein said power converter circuit further includes a coupling transformer for coupling the high frequency voltage wave to said second switching circuit.

8. A circuit according to claim 7 wherein said parallel commutating inductance means is provided by the inductance of said coupling transformer.

9. A circuit according to claim 7 wherein said first switching circuit is an inverter and said second switching circuit is a cycloconverter for producing a variable frequency, variable voltage output waveform.

10. A circuit according to claim 9 wherein said inverter is a single phase inverter connected to a source of unidirectional voltage, and said cycloconverter comprises a plurality of single phase-to-single phase cycloconverter circuits for producing a variable frequency, variable voltage polyphase output waveform.

11. A circuit according to claim 6 wherein said first switching circuit is a single phase inverter connected to a source of unidirectional voltage, and said second switching circuit comprises at least one phase controlled rectifier for producing a variable unidirectional output voltage.

12. A circuit according to claim 11 wherein said power converter circuit further includes a high frequency coupling transformer for coupling the high frequency voltage wave produced by said single phase inverter to said phase controlled rectifier, and wherein said second switching circuit additionally includes a second phase controlled rectifier coupled to said high frequency coupling transformer for producing another independently variable unidirectional output voltage.

13. A circuit according to claim 6 wherein said first and second switching circuits are polyphase cycloconverter circuits for converting a polyphase electric potential to a variable frequency, variable voltage polyphase output waveform, and wherein both of said cycloconverter circuits are symmetrical half wave cycloconverter circuits.

14. A versatile power converter circuit Comprising a high frequency linear coupling transformer having a primary winding and inductively coupled secondary winding means, a single phase inverter circuit coupled to said primary winding including a plurality of solid state switches for converting an electric potential to a high frequency voltage wave, a cycloconverter circuit coupled to said secondary winding means including a plurality of solid state switches for converting the high frequency voltage wave to a desired low frequency polyphase output voltage waveform, tuned parallel capacitor commutation circuit means connected in said inverter circuit for supplying a controlled variable amount of commutating energy for turning off said solid state switches, said commutation circuit means comprising a commutation capacitor and parallel commutation inductance means tuned to a predetermined resonant frequency, and control means for operating said inverter and cycloinverter circuits in synchronism at a variable operating frequency greater than the resonant frequency to thereby control the net capacitive reactance of said commutation circuit means according to the load requirements.

15. A circuit according to claim 14 wherein said commutating inductance means is provided by the inductance of said high frequency coupling transformer, and said commutation capacitor is connected across at least a portion of the primary winding thereof.

16. A circuit according to claim 14 wherein said single phase inverter circuit includes additional solid state switches connected to obtain reverse current flow capability.

17. A circuit according to claim 14 wherein said single phase inverter circuit is constructed in the full bridge circuit configuration, and said commutation circuit means is connected across at least a portion of the primary winding of said high frequency coupling transformer.

18. A circuit according to claim 14 wherein the secondary winding means of said high frequency coupling transformer comprises three center-tapped secondary windings, and said cycloconverter circuit comprises three delta-connected single phase-to-single phase cycloconverter circuits each coupled to one of said secondary windings.

19. A circuit according to claim 18 wherein each single phase-to-single phase cycloconverter circuit comprises bidirectional conducting solid state switches connected to each end of its respective secondary winding, series filter inductor means, and shunt filter capacitor means.

20. A circuit according to claim 14 wherein the secondary winding means of said high frequency coupling transformer comprises a single center-tapped secondary winding, and said cycloconverter circuit comprises three wye-connected single phase-to-single phase cycloconverter circuits each coupled to said secondary winding.

21. A circuit according to claim 20 wherein each single phase-to-single phase cycloconverter circuit comprises bidirectional conducting solid state switches connected to each end of said secondary winding, series filter inductor means, and shunt filter capacitor means.

22. A circuit according to claim 14 wherein the secondary winding means of said high frequency coupling transformer comprises a single secondary winding, and said cycloconverter circuit is a three-phase, half wave cycloconverter circuit.

23. A circuit according to claim 22 wherein said three-phase, half wave cycloconverter circuit comprises a center-tapped reactor connected at its center tap to said secondary winding, first and second groups of said solid state switches respectively connected between each output terminal and either end of said reactor, and filter capacitor means.

24. A versatile power converter circuit comprising a first cycloconverter circuit including a plurality of solid state switches operated to convert a low frequency polyphase electric potential to a high frequency voltage wave, a second cycloconverter circuit including a plurality of solid state switches for convertinG the high frequency voltage wave to a desired low frequency polyphase output voltage waveform, a tuned parallel capacitor commutation circuit coupled between said first and second cycloconverter circuits for supplying a controlled variable amount of commutating energy for turning off said solid state switches in said cycloconverter circuits, said tuned commutation circuit comprising a commutation capacitor and a parallel commutating inductor tuned to a predetermined resonant frequency, and control means for operating said first and second cycloconverter circuits in synchronism at a variable operating frequency greater than the resonant frequency to thereby control the net capacitive reactance of said tuned commutation circuit according to the load requirements.

25. A circuit according to claim 24 wherein said first and second cycloconverter circuits are symmetrical and are both half wave cycloconverter circuits.

26. A circuit according to claim 25 wherein each of said half wave cycloconverter circuits includes two groups of oppositely poled solid state switches respectively connected between a circuit terminal and either end of a center-tapped reactor, and further includes filter capacitor means, said commutation circuit being connected between a neutral circuit terminal and the center-tap of each reactor.