Case 13884

Ultra High Efficiency Grid-Tied Power Conversion

Keywords:

Alternating current, grid connected electronics, photovoltaic inverter systems, PVs

Applications:

Connecting photovoltaics to the AC distribution system and power suppliers

Problem:

Power losses in photovoltaic inverters.

Technology:

This invention proposes a new circuit topology and control method for an AC connected power converter. Here the DC connected inverter transforms the DC source into high frequency AC, with the transformation stage providing both voltage gain and appropriate impedance shaping. The cycloinverter is controlled to modulate the transfer of the high frequency resonant current in response to the changing voltage of the AC port. The buffer-block acts in a similar manner, but is controlled to absorb or deliver power to the storage port which compensates for the power mismatch between the DC and AC ports.

Advantages:
  • Variable-voltage energy storage to decouple energy buffering from PV panel voltage and power tracking requirements.
  • Full soft-switching, with only unipolar devices, allows conduction losses to scale back linearly with output power.
  • Controllable over wide input and output voltages, and output power levels.
  • Positioning of the buffer-block on the high-voltage side of the transformer reduces the required transformer size and enables elimination of electrolytic capacitors for energy buffering. Use of unipolar devices allows full bi-directional power flow (4 quadrant) operation, enabling the converter to perform reactive power compensation on the grid.

Inventors:
  • Professor David J. Perreault (Department of Computer Science and Electrical Engineering, MIT)
  • Brandon J. Pierquet (Department Computer Science and Electrical Engineering, MIT)

Intellectual Property:

US Patent Application 13/011,317 filed 1/21/2011

PCT Patent Application PCT/US2011/022056 filed 1/21/2011

Publications:

Last revised: February 21, 2012

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