Adaptive Soft Switching Control For Power Converter

• US 20150318784A1
• Filed: 08/27/2012
• Published: 11/05/2015
• Est. Priority Date: 08/27/2012
• Status: Active Grant

• Current Assignee: Bombardier Transportation GmbH (Bombardier Incorporated)
• Original Assignee: Bombardier Transportation GmbH (Bombardier Incorporated)
• Inventors: Woronowicz, Konrad, Wu, Di
• Granted Patent: US 9,698,684 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• 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

Control apparatus for use in controlling a power converter adapted to carry out power conversion between a high-voltage end and a low-voltage end. The control apparatus comprises an input configured for receiving at least one input signal conveying a sensed voltage across the high-voltage end, a sensed voltage across the low-voltage end and a sensed current through the low-voltage end; circuitry configured for determining a target switching frequency, a target dead time and a target duty cycle for the converter based at least in part on the sensed voltages, the sensed current and at least one circuit characteristic of the converter; and an output configured for releasing at least one output signal to cause the converter to carry out soft switching in accordance with the target switching frequency, the target dead time and the target duty cycle.

Claims

1. A control apparatus for use in controlling a power converter adapted to carry out power conversion between a high-voltage end and a low-voltage end, the control apparatus comprising:

an input configured for receiving at least one input signal conveying a sensed voltage across the high-voltage end, a sensed voltage across the low-voltage end and a sensed current through the low-voltage end;

circuitry configured for determining a target switching frequency, a target dead time and a target duty cycle for the converter based at least in part on the sensed voltages, the sensed current and at least one circuit characteristic of the converter; and

an output configured for releasing at least one output signal to cause the converter to carry out soft switching in accordance with the target switching frequency, the target dead time and the target duty cycle.

2. The control apparatus defined in claim 1, the circuitry being configured for dynamically determining the target switching frequency, the target dead time and the target duty cycle dynamically in response to changes in the at least one of the sensed voltages or the sensed current.

3. The control apparatus defined in claim 1, further comprising a plurality of sensors for capturing the sensed voltages and the sensed current.

4. The control apparatus defined in claim 1, wherein the circuitry comprises a current regulator configured for receiving an indication of a reference current and for dynamically determining the target duty cycle based on a difference between the desired reference current and the sensed current through the low-voltage end.

5. The control apparatus defined in claim 4, wherein the circuitry further comprises a dead time and switching frequency determiner configured for determining the target dead time and the target switching frequency based at least in part on at least one of the sensed voltages and the reference current.

6. The control apparatus defined in claim 5, wherein the dead time and switching frequency determiner is configured for computing the target dead time and an initial commutation current within the converter based at least in part on the sensed voltages and at least one circuit characteristic of the power converter.

7. The control apparatus defined in claim 6, wherein the converter is characterized by a resonant circuit and wherein the at least one circuit characteristic of the converter comprises a characteristic impedance of a resonant circuit.

8. The control apparatus defined in claim 6, wherein the dead time and switching frequency determiner is configured for computing the target switching frequency based on at least the sensed voltages, the reference current, the target dead time, the initial commutation current and the at least one circuit characteristic of the converter.

9. The control apparatus defined in claim 8, wherein the circuitry further comprises a voltage regulator for determining the reference current based on a reference voltage and at least one of the sensed voltages.

10. The control apparatus defined in claim 5, further comprising a memory storing an association between sensed voltage and reference current values and corresponding dead time and switching frequency values, wherein the dead time and frequency determiner is configured for setting, as the target dead time and the target switching frequency, the dead time and switching frequency values retrieved from the memory as corresponding to the sensed voltages and the reference current.

11. The control apparatus defined in claim 1, wherein the at least one output signal conveys the target switching frequency, the target dead time and the target duty cycle.

12. The control apparatus defined in claim 1, wherein the at least one output signal is provided to a switching controller for controlling time instants at which at least one switching element of the converter is to be switched between on and off states.

13. The control apparatus defined in claim 1, wherein the at least one output signal is indicative of time instants at which at least one switching element of the converter is to be switched between on and off states.

14. The control apparatus defined in claim 1, wherein the converter is a three-phase converter and wherein the at least one output signal comprises three sets of at least one output signal per set, one set for each respective phase of the converter.

15. The control apparatus defined in claim 1, further comprising a duty cycle adjustment unit for adjusting the target duty cycle with an offset.

16. A method for controlling a power converter adapted to carry out power conversion between a high-voltage end and a low-voltage end, the method comprising:

determining a voltage across the high-voltage end, a voltage across the low-voltage end and a current through the low-voltage end;

determining a target switching frequency, a target dead time and a target duty cycle for the converter based at least in part on the voltage across the high-voltage end, the voltage across the low-voltage end, the current through the low-voltage end and at least one circuit characteristic of the converter; and

releasing at least one output signal for causing the converter to carry out soft switching in accordance with the target switching frequency, the target dead time and the target duty cycle.

17. The method defined in claim 16, wherein determining a target switching frequency, a target dead time and a target duty cycle for the converter comprises:

determining the target switching frequency and the target dead time based at least in part on the voltage across the high-voltage end, the voltage across the low-voltage end, a desired average output current and the at least one circuit characteristic of the converter; and

determining the target duty cycle based at least in part on the current through the low-voltage end and the desired average output current.

18. The method defined in claim 17, wherein determining the target switching frequency and the target dead time further comprises:

determining the desired average output current based at least in part on the voltage across the high-voltage end and a reference voltage.

19. The method defined in claim 17,

wherein the converter comprises a first switching sub-circuit with a first terminal and a second terminal, the first terminal of the first switching sub-circuit connected to a first terminal of the high-voltage end, the first switching sub-circuit comprising a first switching element with a first freewheeling diode, a first snubber capacitor and a first control input for controlling switching of the first switching element;

a second switching sub-circuit with a first terminal and a second terminal, the first terminal of the second switching sub-circuit connected to the second terminal of the first switching sub-circuit, the second terminal of the second switching sub-circuit connected to a second terminal of the high-voltage end, the second switching sub-circuit comprising a second switching element with a second freewheeling diode, a second snubber capacitor and a second control input for controlling switching of the second switching element;

an inductor with a first terminal and a second terminal, the first terminal of the inductor connected to the second terminal of the first switching sub-circuit and to the first terminal of the second switching sub-circuit, the second terminal of the inductor connected to a first terminal of the low-voltage end;

wherein a second terminal of the low-voltage end is connected to the second terminal of the second switching sub-circuit and to the second terminal of the high-voltage end;

wherein the first switching element is switchable from an off state to an on state and back to the off state in accordance with a switching frequency and a duty cycle, whereby upon the first switching element switching to the off state, current flowing through the inductor in a direction of average current begins to decrease;

wherein the second switching element is switchable from an off state to an on state and back to the off state while the first switching element remains in the off state;

wherein a dead time interval corresponds to the time interval between switching of the second switching element to the off state and switching of the first switching element back to the on state.

20. The method defined in claim 19, wherein the soft switching produces a commutation current corresponding to the current through the inductor in a direction opposite to the direction of average current flow, the commutation current having an initial value at the beginning of the dead time interval;

and wherein determining the target switching frequency and the target dead time comprises;

determining the target dead time and a desired initial value for the commutation current based at least in part on the voltage across the high-voltage end, the voltage across the low-voltage end and the at least one circuit characteristic of the converter; and

determining the target switching frequency based at least in part on the voltage across the high-voltage end, the voltage across the low-voltage end, the target dead time, the desired average output current, the desired initial value for the commutation current and the at least one circuit characteristic of the converter.

21. A computer-readable storage medium storing computer-readable instructions which, when executed by a controller, cause the controller to execute a method of controlling a power converter adapted to carry out power conversion between a high-voltage end and a low-voltage end, the method comprising:

determining a voltage across the high-voltage end, a voltage across the low-voltage end and a current through the low-voltage end;

determining a target switching frequency, a target dead time and a target duty cycle for the converter based at least in part on the voltage across the high-voltage end, the voltage across the low-voltage end, the current through the low-voltage end and at least one circuit characteristic of the converter; and

releasing at least one output signal for causing the converter to carry out soft switching in accordance with the target switching frequency, the target dead time and the target duty cycle.

22-32. -32. (canceled)