Single phase cycloconverter with integrated line-cycle energy storage
View Patent ↗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.
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.