Current stiff converters with resonant snubbers

• US 5,949,664 A
• Filed: 06/18/1998
• Issued: 09/07/1999
• Est. Priority Date: 06/19/1997
• Status: Expired due to Term

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Bernet, Steffen, Cardoso Filho, Braz de J., Lipo, Thomas A.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US09/099,635
• Time in Patent Office: 446 Days
• Field of Search: 363/34, 363/35, 363/37, 363/53, 363/54, 363/56, 363/57, 363/85, 363/96, 363/128, 363/135, 363/136
• US Class Current: 363/37
• CPC Class Codes: H02M 1/34 Snubber circuits
• CPC Class Codes: H02M 1/342 Active non-dissipative snubbers
• CPC Class Codes: H02M 7/521 in a bridge configuration
• 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

A current stiff power conversion system, such as a rectifier, inverter, or AC-to-AC converter is provided wherein power converter switching devices in the power conversion system may be switched at or near zero voltage conditions to minimize or eliminate switching losses and increase switching frequencies. Zero voltage switching conditions are achieved by providing a snubber capacitor across each switching device in the power conversion system, and connecting an active commutation unit, including an inductor and an active commutation unit switching device connected in series across DC bus lines in parallel with the bridge of power conversion switching devices. Zero voltage switching conditions for the power conversion switching devices are achieved by controlling the power conversion switching devices and the active commutation unit to establish a resonance between the snubber capacitors and the active commutation unit to drive the voltage across incoming switching devices in the power conversion system to at or near zero. Zero current switching of the active commutation unit switching device, and reduced switching device stress in the power conversion system, is achieved by controlling the power conversion switching devices to establish zero current switching conditions and a desired snubber driving voltage for the active commutation unit before the active commutation unit is turned on to establish the resonance condition. Since zero voltage switching conditions for the power conversion switching devices is achieved each switching cycle, the power conversion system may be controlled using a PWM control scheme.

Claims

1. A current stiff power conversion system, comprising:

(a) a bridge of power conversion switching devices connected across DC bus lines and responsive to power conversion switching device control signals;

(b) a snubber capacitor connected across each of the power conversion switching devices;

(c) an active commutation unit connected across the DC bus lines in parallel with the bridge of power conversion switching devices and responsive to active commutation switching control signals; and

(d) controller means for providing the power conversion switching device control signals to the power conversion switching devices and the active commutation switching control signals to the active commutation unit such that the power conversion switching devices are controlled to turn on and off under approximately zero voltage switching conditions and to create a zero current switching condition for the active commutation unit and such that the active commutation unit is controlled to turn on and off under said zero current switching condition to establish a resonance between the snubber capacitors and the active commutation unit to establish said approximately zero voltage switching conditions.

2. The current stiff power conversion system of claim 1 wherein the voltage across incoming power conversion switching devices is reduced to zero before the incoming switching devices are turned on.

3. The current stiff power conversion system of claim 1 wherein the power conversion switching devices are gate-turn-off thyristors.

4. The current stiff power conversion system of claim 1 wherein the bridge of power conversion switching devices forms a rectifier connecting AC input lines to the DC bus lines and wherein the controller means includes means for providing power conversion switching device control signals to the power conversion switching devices to generate a DC output signal on the DC bus lines from an AC input signal on the AC input lines.

5. The current stiff power conversion system of claim 4 wherein the controller means includes means for providing PWM switching device control signals to the power conversion switching devices to generate the DC output signal on the DC bus lines from the AC input signal on the AC input lines.

6. The current stiff power conversion system of claim 1 wherein the bridge of power conversion switching devices forms an inverter connecting the DC bus lines to AC output lines and wherein the controller means includes means for providing power conversion switching device control signals to the power conversion switching devices to generate an AC output signal on the AC output lines from a DC input signal on the DC bus lines.

7. The current stiff power conversion system of claim 6 wherein the controller means includes means for providing PWM switching device control signals to the power conversion switching devices to generate the AC output signal on the AC output lines from the DC input signal on the DC bus lines.

8. The current stiff power conversion system of claim 1 wherein the active commutation unit includes and active commutation unit inductor connected in series with an active commutation unit switching device responsive to the active commutation switching control signals.

9. The current stiff power conversion system of claim 8 wherein the active commutation unit switching device is a gate-turn-off thyristor.

10. The current stiff power conversion system of claim 1 wherein the controller means includes means for providing power conversion switching device control signals to the power conversion switching devices to control the power conversion switching devices after an outgoing switching device is tuned off but before the active commutation unit is turned on to establish a desired snubber driving voltage.

11. A current stiff power conversion system, comprising:

(a) a rectifier bridge of rectifier switching devices forming a rectifier connected between AC input lines and DC bus lines and responsive to rectifier switching device control signals;

(b) a rectifier snubber capacitor connected across each of the rectifier switching devices;

(c) a first active commutation unit connected across the DC bus lines in parallel with the bridge of rectifier switching devices and responsive to first active commutation switching control signals;

(d) an inverter bridge of inverter switching devices forming an inverter connected between the DC bus lines and AC output lines and responsive to inverter switching device control signals;

(e) an inverter snubber capacitor connected across each of the inverter switching devices;

(f) a second active commutation unit connected across the DC bus lines in parallel with the bridge of inverter switching devices and responsive to second active commutation switching control signal; and

(g) controller means for providing the rectifier switching device control signals to the rectifier switching devices and the first active commutation switching control signals to the first active commutation unit to control the rectifier switching devices to turn on and off under approximately zero voltage switching conditions to generate a DC signal on the DC bus lines from an AC signal on the AC input lines and to establish a zero current switching condition for the first active commutation unit and for controlling the first active commutation unit to turn on and off under said zero current switching condition to establish a resonance between the first active commutation unit and the rectifier snubber capacitors to establish said zero voltage switching condition for said rectifier switching devices, and for providing the inverter switching device control signals to the inverter switching devices and the second active commutation switching control signals to the second active commutation unit to control the inverter switching devices to turn on and off under approximately zero voltage switching conditions to generate an AC signal on the AC output lines from the DC signal on the DC bus lines and to establish a zero current switching condition for the second active commutation unit and for controlling the second active commutation unit to turn on and off under said zero current switching condition to establish a resonance between the second active commutation unit and the inverter snubber capacitors to establish said zero voltage switching condition for said inverter switching devices.

12. The current stiff power conversion system of claim 11 wherein the voltage across incoming rectifier and inverter switching devices is reduced to zero before the incoming inverter and rectifier switching devices are turned on.

13. The current stiff power conversion system of claim 11 wherein the rectifier and inverter switching devices are gate-turn-off thyristors.

14. The current stiff power conversion system of claim 11 wherein the controller means includes means for providing PWM switching device control signals to the rectifier and inverter switching devices to control the rectifier switching devices to generate the DC signal on the DC bus lines from the AC input signal on the AC input lines and to control the inverter switching devices to generate the AC output signal on the AC output lines from the DC signal on the DC bus lines.

15. The current stiff power conversion system of claim 11 wherein the first and second active commutation units each include an active commutation unit inductor connected in series with an active commutation unit switching device responsive to the first or second active commutation switching control signals.

16. The current stiff power conversion system of claim 15 wherein the active commutation unit switching devices are gate-turn-off thyristors.

17. The current stiff power conversion system of claim 11 wherein the controller means includes means for providing rectifier switching device control signals to the rectifier switching devices to control the rectifier switching devices after an outgoing rectifier switching device is turned off but before the first active commutation unit is turned on to establish a first desired snubber driving voltage, and for providing inverter switching device control signals to the inverter switching devices to control the inverter switching devices after an outgoing inverter switching device is turned off but before the second active commutation unit is turned on to establish a second desired snubber driving voltage.

18. A method for controlling a current stiff power conversion system having a bridge of power conversion switching devices connected across DC bus lines to achieve approximately zero-voltage turn on and turn off the power conversion switching devices, comprising the steps of:

(a) connecting a snubber capacitor across each of the power conversion switching devices in the bridge of power conversion switching devices;

(b) connecting an active commutation unit in parallel with the bridge of power conversion switching devices across the DC bus lines;

(c) turning off an outgoing one of the power conversion switching devices;

(d) controlling the power conversion switching devices to establish a zero current switching condition for the active commutation unit;

(e) turning on the active commutation unit under said zero current switching condition to establish a resonance between the snubber capacitors and the active commutation unit to reduce a voltage across the incoming power conversion switching device to approximately zero; and

(f) turning on the incoming power conversion switching device when the voltage across the incoming power conversion switching device is approximately zero.

19. The method of claim 18 wherein the voltage across the incoming power conversion switching device is reduced to zero before the incoming switching device is turned on.

20. The method of claim 18 wherein the bridge of power conversion switching devices forms a rectifier connecting AC input lines to the DC bus lines and including the step of repeating the steps of turning off an outgoing power conversion switching device and turning on an incoming power conversion switching device in a pattern to generate a DC output signal on the DC bus lines from an AC input signal on the AC input lines.

21. The method of claim 20 wherein the steps of turning off an outgoing power conversion switching device and turning on an incoming power conversion switching device are repeated in a PWM pattern to generate the DC output signal on the DC bus lines from the AC input signal on the AC input lines.

22. The method of claim 18 wherein the bridge of power conversion switching devices forms an inverter connecting the DC bus lines to AC output lines and including the step of repeating the steps of turning off an outgoing power conversion switching device and turning on an incoming power conversion switching device in a pattern to generate an AC output signal on the AC output lines from a DC input signal on the DC bus lines.

23. The method of claim 22 wherein the steps of turning off an outgoing power conversion switching device and turning on an incoming power conversion switching device are repeated in a PWM pattern to generate the AC output signal on the AC output lines from the DC input signal on the DC bus lines.

24. The method of claim 18 wherein the active commutation unit includes and active commutation unit inductor connected in series with an active commutation unit switching device and wherein the step of turning on the active commutation unit includes the step of turning on the active commutation unit switching device.

25. The method of claim 18 wherein the step of controlling the power conversion switching devices includes the step of turning on a power conversion switching device after an outgoing switching device is tuned off but before turning on the active commutation unit to establish the resonance between the snubber capacitors and the active commutation unit to establish a desired snubber driving voltage.