Single phase cycloconverter with integrated line-cycle energy storage

• US 9,531,300 B2
• Filed: 09/10/2014
• Issued: 12/27/2016
• Est. Priority Date: 09/16/2013
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Enphase Energy Incorporated
• Inventors: Harrison, Michael J., Zimmanck, Donald Richard
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Tiku, Sisay G
• Application Number:
  US14/482,021
• Publication Number:
  US 20150078053A1
• Time in Patent Office: 839 Days
• Field of Search: 363 5602- 5605, 363/132, 363/149, 363152-153, 363/95, 363/98
• US Class Current: 1/1
• CPC Class Codes: H02M 5/2932 with automatic control of output voltage, current or power
• CPC Class Codes: H02M 5/297 for conversion of frequency
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• 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

A method and apparatus for line-cycle storage of a single-phase cycloconverter. The method includes receiving input power from an input port of the singe-phase cycloconverter and monitoring an AC output port of the single-phase cycloconverter. The method measures energy stored in a line-cycle energy storage circuit coupled to one line of the AC output port of the single-phase cycloconverter, and determines a phase difference between a monitored AC voltage of the AC output port and the measured voltage of the line-cycle energy storage circuit. The method controls switches in the single-phase cycloconverter to selectively store energy in the line-cycle energy storage circuit based on the phase difference.

Claims

1. A method for line-cycle energy storage in a single-phase cycloconverter comprising:

receiving input power from an input port of the singe-phase cycloconverter;

monitoring an AC output port of the single-phase cycloconverter;

measuring energy stored in a line-cycle energy storage circuit coupled to one line of the AC output port of the single-phase cycloconverter;

determining a phase difference between a monitored AC voltage of the AC output port and a measured voltage of the line-cycle energy storage circuit; and

controlling switches in the single-phase cycloconverter to selectively store energy in the line-cycle energy storage circuit based on the phase difference.

2. The method of claim 1, wherein controlling switches further comprises operating the switches such that a voltage across the line-cycle energy storage circuit has a phase difference of 45 degrees when compared to the monitored AC voltage.

3. The method of claim 2, wherein a current of the line-cycle energy storage circuit has a current phase difference of 135 degrees when compared to a current of the monitored AC output port further coupled to an AC source.

4. The method of claim 1, wherein controlling switches further comprises operating the switches such that the magnitude of the monitored AC voltage is equal to the magnitude of the measured voltage of the line-cycle energy storage circuit.

5. The method of claim 1, wherein controlling switches further comprises operating in a reduced power mode wherein the magnitude of the voltage across the line-cycle energy storage circuit and magnitude of the current circulated through the line-cycle energy storage circuit is halved.

6. The method of claim 1, wherein controlling switches further comprises operating the switches such that a magnitude of a current of the line-cycle energy storage circuit is the same value as the magnitude of a current of the monitored AC output port coupled to an AC source.

7. The method of claim 1, wherein the received input power is a DC power and the AC output port is coupled to an AC source.

8. The method of claim 1, further comprising providing reactive power support and filtering through the line-cycle energy storage circuit comprising at least one line-cycle capacitor and at least one inductor coupled to the output port.

9. An apparatus operative to provide line-cycle energy storage in a single-phase cycloconverter comprising:

a controller operating pairs of switches of the single-phase cycloconverter;

a first pair, second pair, and third pair of switches coupled in parallel;

an AC output port coupled across the first pair and second pair of switches;

a line-cycle storage circuit coupled to the output port for single-phase operation; and

a monitoring circuit coupled to the controller, configured to measure voltages at the AC output port and the line-cycle storage circuit and maintain a predetermined phase difference between the measured voltages.

10. The apparatus of claim 9, wherein the line-cycle storage circuit comprises at least one line-cycle capacitor coupled between a line of the AC output port and the third pair of switches.

11. The apparatus of claim 10, wherein the controller operates the switches such that a voltage of the line-cycle storage circuit and a voltage of an AC source coupled to terminals of the AC output port have a phase difference of 45 degrees.

12. The apparatus of claim 10, wherein the controller operates the switches such that a current of the line-cycle storage circuit and a current of an AC source coupled to terminals of the AC output port have a phase difference of 135 degrees.

13. The apparatus of claim 10, wherein the line-cycle storage circuit is coupled between the AC output port and an AC source via a cable integrated with at least one capacitor and inductor.

14. The apparatus of claim 9, wherein the line-cycle storage circuit comprises at least one surge protection inductor serially coupled to each line of the single-phase output port, and at least one capacitor coupled in parallel between each line of the single-phase output port.

15. A system for line-cycle storage of a single-phase cycloconverter, comprising:

at least one photovoltaic (PV) module;

at least one cycloconverter, with an input port coupled to the at least one PV module, wherein each of the at least one cycloconverter employs;

a controller operating pairs of switches of the single-phase cycloconverter;

a first pair, second pair, and third pair of switches coupled in parallel;

an AC output port coupled across the first pair and second pair of switches;

a line-cycle storage circuit coupled to the output port for single-phase operation; and

a monitoring circuit coupled to the controller, configured to measure voltages at the AC output port and the line-cycle storage circuit and maintain a predetermined phase difference between the measured voltages.

16. The system of claim 15, wherein the line-cycle storage circuit comprises at least one line-cycle capacitor coupled between a line of the AC output port and the third pair of switches.

17. The system of claim 16, wherein the controller operates the switches such that a voltage of the line-cycle storage circuit and a voltage of an AC source coupled to terminals of the AC output port have a phase difference of 45 degrees.

18. The system of claim 16, wherein the controller operates the switches such that a current of the line-cycle storage circuit and a current of an AC source coupled to terminals of the single-phase output port have a phase difference of 135 degrees.

19. The system of claim 16, wherein the line-cycle storage circuit further comprises two capacitors coupled to the first pair, second pair, and third pair of switches and a line of the single-phase output port.

20. The system of claim 15, wherein the line-cycle storage circuit comprises at least one surge protection inductor serially coupled to each line of the single-phase output port, and at least one capacitor coupled in parallel between each line of the AC output port.