Very high efficiency three phase power converter

• US 8,730,702 B2
• Filed: 03/01/2010
• Issued: 05/20/2014
• Est. Priority Date: 03/03/2009
• Status: Active Grant

• Current Assignee: Parker Intangibles LLC (Parker-Hannifin Corporation)
• Original Assignee: Renewable Power Conversion, Inc.
• Inventors: Stern, Michael Joseph
• Primary Examiner(s): Zhang, Jue
• Assistant Examiner(s): Jackson, Lakaisha
• Application Number:
  US12/715,372
• Publication Number:
  US 20100226159A1
• Time in Patent Office: 1,541 Days
• Field of Search: 363/37, 363/71, 363/98, 363/131, 363/132
• US Class Current: 363/132
• CPC Class Codes: H02M 1/0048 Circuits or arrangements for reducing losses using snubbers H02M1/34
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• 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
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A DC-to-AC power converter is disclosed which provides current regulated three-phase AC outputs and very high conversion efficiencies. The converter sinks power from an external DC current source and steers that current directly into two phases of a three-phase load by using complementary semiconductor switches in disparate half-bridges of a six-pole bridge. The steering switch selection rotates every 60° to direct current into the two phases with the largest voltage differential at any given time. The remaining half-bridge acts as a high-frequency, bi-directional current source to balance the three-phase load currents. This topology and control method significantly reduces power conversion losses. Prior art converters first convert “soft” DC sources to voltage sources and then to AC current sources. The invention eliminates the need for large filter inductors and DC bus capacitors used in prior art converters. The invention is optimized for photovoltaic, utility-grid-interactive applications.

Claims

1. A DC current source to AC current source power converter apparatus for supplying power to a three-phase AC electrical grid comprising;

a DC current source and a means for selectively coupling said DC current source to the three-phase AC electrical grid for a portion of an AC electrical grid cycle synchronized with electrical grid phase voltages and signs for a fixed period on each phase and wherein said means excludes an energy storage capacitor located either directly across the DC current source or effectively across the DC current source, with respect to altering the DC current source impedance as seen by the power converter apparatus and further comprising an inductor in series with said DC current source and a semiconductor switching matrix wherein said semiconductor switching matrix comprises a means for selectively coupling said DC current source directly across two phases of the three-phase AC electrical grid, synchronized with three-phase AC electrical grid phase voltages and signs and wherein said semiconductor switching matrix further comprises a means for regulating current into the remaining third phase of the three-phase AC electrical grid.

2. The DC current source to AC current source power converter apparatus according to claim 1 wherein said DC current source is a photovoltaic current source.

3. A photovoltaic source to AC current source power converter apparatus for supplying power to an AC electrical grid comprising a photovoltaic source, an input capacitor connected across said photovoltaic source, a DC voltage source to DC current source converter stage with an input port across said input capacitor and an output port common with an input port of a semiconductor switching matrix and a means of controlling said semiconductor switching matrix to selectively couple said DC voltage source to DC current source converter stage output port to the AC electrical grid for a portion of an AC grid electrical cycle and wherein said means excludes an energy storage capacitor directly or effectively across the input port of the semiconductor switching matrix and further comprising a means for selectively and directly coupling the DC voltage source to DC current source converter stage output port to each phase of a three-phase electrical grid, synchronized with three-phase electrical grid phase voltages and signs for a rotating 120 degree coupling period per AC electrical grid phase and said photovoltaic source and further comprising a means for selectively coupling said DC voltage source to DC current source converter stage output port and a means for regulating current into the remaining third phase of the three-phase AC electrical grid where said remaining third phase is a phase without direct couplings to said DC voltage source to DC current source converter stage output port at any instant in time.

4. The photovoltaic source to AC current source power converter apparatus for supplying power to an AC electrical grid, according to claim 3, further comprising a means to couple the DC voltage source to DC current source converter stage output port to each phase of a three phase electrical grid, synchronized with electrical grid phase voltages and signs for a fixed period on each phase.

5. The photovoltaic source to AC current source power converter apparatus for supplying power to an AC electrical grid, according to claim 3, further comprising a means to couple the DC voltage source to DC current source converter stage output port to each phase of a three-phase electrical grid, synchronized with electrical grid phase voltages and signs for a rotating 120 degree coupling period per AC electrical grid phase and said photovoltaic source.