Circuits and techniques for interfacing with an electrical grid

• US 9,401,664 B2
• Filed: 03/12/2013
• Issued: 07/26/2016
• Est. Priority Date: 05/25/2012
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Pierquet, Brandon J., Perreault, David J.
• Primary Examiner(s): Finch, III, Fred E
• Assistant Examiner(s): ROSARIO BENITEZ, GUSTAVO A
• Application Number:
  US13/795,633
• Publication Number:
  US 20130314948A1
• Time in Patent Office: 1,232 Days
• Field of Search: 363/123, 363/132, 363/37, 363/65, 363/71, 363/131, 363/157, 363/159, 363/8, 363/9, 363/95, 307/82
• US Class Current: 1/1
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: H02M 7/497 sinusoidal output voltages being obtained by combination of several voltages being out of phase
• CPC Class Codes: H02M 7/797 using semiconductor devices only

Abstract

Circuit topologies and control methods for a multi-phase grid interface are described. In at least one embodiment, a power conversion circuit is provided that includes an inverter stage, a transformer stage, and a cycloconverter stage. The cycloconverter stage may include one cycloconverter circuit for each of multiple phases associated with a multi-phase grid. In some embodiments, each cycloconverter circuit may include first and second half-bridge circuits coupled back-to-back.

Claims

1. A power conversion circuit having an input port to receive a direct current (DC) input signal and multiple output ports to provide a multi-phase alternating current (AC) output signal, the power conversion circuit comprising:

an inverter circuit to convert the DC input signal to an AC current signal at an inverter circuit output port, the inverter circuit including a number of controllable switches;

a transformer stage having an input port and multiple output ports, the transformer stage coupled to receive the AC current signal at the transformer stage input port and configured to provide at least one of electrical isolation and voltage transformation between the inverter circuit output port and the multiple output ports of the power conversion circuit; and

a cycloconverter stage having multiple cycloconverter circuits, with each of the multiple cycloconverter circuits supporting a corresponding phase of the multi-phase AC output signal of the power conversion circuit and including a number of controllable switches, wherein each of the multiple cycloconverter circuits includes an input port coupled to receive an input signal from a corresponding output port of the transformer stage and an output port to provide an AC output signal of the power conversion circuit for the corresponding phase, and each of the multiple cycloconverter circuits are controlled, at least in part, by select ones of the controllable switches in the cycloconverter circuits to provide a phase-shift between a resonant AC current and a switching voltage of the cycloconverter circuits at which outputs of the cycloconverter circuits provide the AC output signal of the power conversion circuit for the corresponding phase, wherein the phase-shift is based, at least in part, on polarity of an applied voltage at a corresponding cycloconverter stage output port,

wherein the controllable switches of said cycloconverter stage are controlled relative to a switching function of said cycloconverter stage which determines power flow through said cycloconverter stage, and the power flow through said cycloconverter stage is modulated by modifying the switching function of said cycloconverter stage relative to the resonant AC current.

2. The power conversion circuit of claim 1, wherein:

one or more of the input ports of the multiple cycloconverter circuits are galvanically isolated from the inverter circuit.

3. The power conversion circuit of claim 2, wherein:

each of the input ports of the multiple cycloconverter circuits are galvanically isolated from the input ports of the other cycloconverter circuits.

4. The power conversion circuit of claim 1, wherein:

the multiple cycloconverter circuits are each comprised of first and second half-bridge circuits, wherein the first and second half-bridge circuits include first and second unidirectional voltage blocking half-bridge circuits coupled in a back-to-back configuration.

5. The power conversion circuit of claim 1, wherein:

each of the multiple cycloconverter circuits includes a first half-bridge circuit having first, second, and third terminals and a second half-bridge circuit having first, second, and third terminals, wherein the first terminal of each of the first and second half-bridge circuits corresponds to the input port of the cycloconverter circuit, the second terminal of each of the first and second half-bridge circuits corresponds to the output port of the cycloconverter circuit, and the third terminals of the first and second half-bridge circuits are coupled to one another.

6. The power conversion circuit of claim 4, further comprising:

a controller to control switching of the controllable switches within the inverter circuit and the controllable switches in each of the multiple cycloconverter circuits, the controller being configured to;

for a first polarity of a voltage signal provided at the output port of a first cycloconverter circuit, bias first and second switches of the first half-bridge circuit of the first cycloconverter circuit into their conduction states and modulate the first and second switches of the second half-bridge of the first cycloconverter circuit.

7. The power conversion circuit of claim 6, wherein:

the controller is configured to;

for a second, different polarity of the voltage signal provided at the output port of the first cycloconverter circuit, bias the first and second switches of the second half-bridge circuit of the first cycloconverter circuit into their conduction states and modulate the first and second switches of the first half-bridge circuit of the first cycloconverter circuit.

19. The power conversion circuit of claim 1 wherein the switching voltage of the cyclococonverter circuits is determined by the switching function of said cycloconverter stage.

20. The power conversion circuit of claim 1 wherein said transformer stage is further configured to provide impedance shaping between the inverter circuit output port and the transformer stage output ports and to generate AC current signals at the transformer stage output ports, wherein the AC current signal generated by said inverter circuit is provided having a first voltage level and the AC current signals generated by said transformer stage are provided having a second, different voltage level.

21. The power conversion circuit of claim 20 wherein the AC current signals generated by said transformer stage are provided having a first frequency and the AC output signals of the power conversion circuit are provided having a second, different frequency.

22. The power conversion circuit of claim 1 wherein the resonant AC current is provided by a resonant circuit which is serially coupled in a select portion of a signal path between an input port of said inverter circuit and the input ports of said cycloconverter circuits.

23. The power conversion circuit of claim 1 wherein magnitude of the resonant AC current signal is selected to control power flow through at least one of said inverter circuit and said cycloconverter stage.

24. The power conversion circuit of claim 1 wherein the switches of said inverter circuit are controlled relative to a switching function of said inverter circuit which determines power flow through said inverter circuit, and the power flow through said inverter circuit is modulated by modifying the switching function of said inverter circuit relative to the resonant AC current signal.

8. A power conversion circuit having input terminals to receive a direct current (DC) voltage signal and output terminals to provide a multi-phase alternating current (AC) voltage signal, the power conversion circuit comprising:

an inverter circuit having input terminals and output terminals, the input terminals corresponding to the input terminals of the power conversion circuit, wherein the inverter circuit is configured to convert a DC voltage signal received at the input terminals to a high-frequency AC signal at the output terminals;

a transformer stage having an input port coupled to the output port of the inverter circuit and having at least two output ports, wherein the transformer stage is configured to provide voltage transformation for the high-frequency AC signal received at the output of the inverter circuit; and

a cycloconverter stage having multiple cycloconverter circuits, with each of the multiple cycloconverter circuits having an input port to receive a signal from a corresponding output port of the transformer stage and an output port to deliver an output signal having a corresponding phase of the multi-phase AC voltage signal, the multiple cycloconverter circuits each being configured to receive the signal from the corresponding output of the transformer stage and to frequency convert the signal to generate the corresponding output signal, each cycloconverter circuit comprising;

a first half-bridge circuit having first, second, and third terminals; and

a second half-bridge circuit having first, second, and third terminals;

wherein the first terminal of each of the first and second half-bridge circuits corresponds to one of the input terminals of the cycloconverter circuit, the second terminal of each of the first and second half-bridge circuits corresponds to one of the output terminals of the cycloconverter circuit, and the third terminal of each of the first and second half-bridge circuits is coupled to the third terminal of the other of the first and second half-bridge circuits, and wherein each of the multiple cycloconverter circuits are controlled, at least in part, by select ones of the first and second half-bridge circuits in the cycloconverter circuits to provide a phase-shift between a resonant AC current and a switching voltage of the cycloconverter circuits at which outputs of the cycloconverter circuits provide the AC output signal of the power conversion circuit for the corresponding phase, wherein the phase-shift is based, at least in part, on polarity of an applied voltage at a corresponding cycloconverter stage output port, and wherein each of the first and second half-bridge circuits are controlled relative to a switching function of said cycloconverter stage which determines power flow through said cycloconverter stage, and the power flow through said cycloconverter stage is modulated by modifying the switching function of said cycloconverter stage relative to the resonant AC current.

9. The power conversion circuit of claim 8, wherein:

the first half-bridge circuit of each cycloconverter circuit comprises first and second switches each having first, second, and third terminals and a bypass capacitor and the second half-bridge circuit of the cycloconverter circuit comprises first and second switches each having first, second, and third terminals and a bypass capacitor.

10. The power conversion circuit of claim 9, further comprising:

a controller to control switching of switches within the inverter circuit and the multiple cycloconverter circuits, the controller being configured to;

for a first polarity of a voltage signal provided at the output port of a first cycloconverter circuit, bias first and second switches of the first half-bridge circuit of the first cycloconverter circuit into their conduction states and modulate the first and second switches of the second half-bridge of the first cycloconverter circuit.

11. The power conversion circuit of claim 10, wherein:

the controller is configured to;

for a second, different polarity of the voltage signal provided at the output port of the first cycloconverter circuit, bias the first and second switches of the second half-bridge circuit of the first cycloconverter circuit into their conduction states and modulate the first and second switches of the first half-bridge circuit of the first cycloconverter circuit.

12. The power conversion circuit of claim 9, further comprising:

a controller to control switching of switches within the inverter circuit and the multiple cycloconverter circuits, the controller being configured to;

for at least some operating conditions, modulate the first switch of the first half-bridge circuit and the second switch of the second half-bridge circuit on and off substantially simultaneously, and modulate the second switch of the first half-bridge circuit and the first switch of the second half-bridge circuit on and off substantially simultaneously.

13. The power conversion circuit of claim 9, further comprising:

a controller to control switching of switches within the inverter circuit and the multiple cycloconverter circuits, the controller being configured to;

for at least some operating conditions, modulate the first switch of the first half-bridge circuit and the first switch of the second half-bridge circuit on and off substantially simultaneously, and modulate the second switch of the first half-bridge circuit and the second switch of the second half-bridge circuit on and off substantially simultaneously.

14. In a system, a power conversion circuit having an input port to receive a direct current (DC) input signal and multiple output ports to provide a multi-phase alternating current (AC) output signal, the power conversion circuit comprising:

two or more cycloconverter circuits each having an input and an output, with each cycloconverter circuit comprising;

a first half-bridge circuit having first, second, and third terminals, the first half-bridge circuit comprising first and second switches each having first, second and third terminals and a bypass capacitor; and

a second half-bridge circuit having first, second, and third terminals, the second half-bridge circuit comprising first and second switches each having first, second, and third terminals and a bypass capacitor;

wherein the first terminal of each of the first and second half-bridge circuits corresponds to the input of the cycloconverter circuit, the second terminal of each of the first and second half-bridge circuits corresponds to the output of the cycloconverter circuit, and the third terminal of the first half-bridge circuit is coupled to the third terminal of the second half-bridge circuit; and

wherein each of the cycloconverter circuits generates an AC output signal having a corresponding phase of the multi-phase AC output signal of the power conversion circuit, and wherein each of the cycloconverter circuits are provided as part of a cycloconverter stage and are controlled, at least in part, by select ones of the first and second half-bridge circuits in the cycloconverter circuits to provide a phase-shift between a resonant AC current and a switching voltage of the cycloconverter circuits at which outputs of the cycloconverter circuits provide the AC output signal of the power conversion circuit for the corresponding phase, wherein the phase-shift is based, at least in part, on polarity of an applied voltage at a corresponding cycloconverter stage output port, and wherein each of the first and second half-bridge circuits are controlled relative to a switching function of said cycloconverter stage which determines power flow through said cycloconverter stage, and the power flow through said cycloconverter stage is modulated by modifying the switching function of said cycloconverter stage relative to the resonant AC current.

15. The system of claim 14, further comprising:

a controller to control switching of switches within the two or more cycloconverter circuits, the controller being configured to;

for a first polarity of a voltage signal provided at the output port of a first cycloconverter circuit, bias first and second switches of the first half-bridge circuit of the first cycloconverter circuit into their conduction states and modulate the first and second switches of the second half-bridge of the first cycloconverter circuit.

16. The system of claim 15, wherein:

the controller is configured to;

for a second, different polarity of the voltage signal provided at the output port of the first cycloconverter circuit, bias the first and second switches of the second half-bridge circuit of the first cycloconverter circuit into their conduction states and modulate the first and second switches of the first half-bridge circuit of the first cycloconverter circuit.

17. The system of claim 14, further comprising:

a controller to control switching of switches within the two or more cycloconverter circuits, the controller being configured to;

for at least some operating conditions, modulate the first switch of the first half-bridge circuit and the second switch of the second half-bridge circuit on and off substantially simultaneously, and modulate the second switch of the first half-bridge circuit and the first switch of the second half-bridge circuit on and off substantially simultaneously.

18. The system of claim 14, further comprising:

a controller to control switching of switches within the two or more cycloconverter circuits, the controller being configured to;

for at least some operating conditions, modulate the first switch of the first half-bridge circuit and the first switch of the second half-bridge circuit on and off substantially simultaneously, and modulate the second switch of the first half-bridge circuit and the second switch of the second half-bridge circuit on and off substantially simultaneously.