Converter topologies for common mode voltage reduction

Patent metadata

Field	Value
Publication number	US-9825556-B2
Application number	US-201615080142-A
Country	US
Kind code	B2
Filing date	Mar 24, 2016
Priority date	Mar 25, 2015
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

An inverter includes a three-winding transformer, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, and an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adapted to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid. At least two of the DC-AC inverter, the cycloconverter, or the active filter are electrically coupled via a common reference electrical interconnect.

First claim

The invention claimed is:

1. An inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid, the inverter comprising:
a three-winding transformer that includes a first winding, a second winding, and a third winding;
a DC-AC inverter electrically coupled to the first winding of the transformer, wherein the DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding;
a cycloconverter electrically coupled to the second winding of the transformer, wherein the cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid; and
an active filter electrically coupled to the third winding of the transformer, wherein the active filter is adapted to sink and source power with one or more energy storage devices based on an instantaneous mismatch in power between the DC source and the AC grid,
wherein each of the DC-AC inverter, the cycloconverter, and the active filter is electrically coupled to a common reference electrical interconnect.

2. The inverter of claim 1 , wherein the DC-AC inverter comprises a half-bridge inverter circuit and a capacitor divider electrically coupled with the half-bridge inverter circuit.

3. The inverter of claim 2 , wherein the first winding includes a first terminal and a second terminal;
wherein the half-bridge inverter circuit comprises a first electrical switch electrically coupled to a second electrical switch at a first node;
wherein the capacitor divider comprises a first capacitor electrically coupled to a second capacitor and the first terminal at a second node; and
wherein the DC-AC inverter comprises an inductor electrically coupled in series to the second terminal and the first node.

4. The inverter of claim 3 , wherein the DC-AC inverter is electrically coupled to the common reference electrical interconnect at the second node.

5. The inverter of claim 1 , wherein the cycloconverter comprises a set of electrical switches and a capacitor divider electrically coupled with the set of electrical switches.

6. The inverter of claim 5 , wherein the second winding includes a first terminal and a second terminal;
wherein the set of electrical switches comprises a first subset of electrical switches electrically coupled to a second subset of electrical switches at a first node;
wherein the capacitor divider comprises a first capacitor electrically coupled to a second capacitor and the first terminal at a second node; and
wherein the cycloconverter comprises an inductor electrically coupled in series to the second terminal and the first node.

7. The inverter of claim 6 , wherein the cycloconverter is electrically coupled to the common reference electrical interconnect at the second node.

8. The inverter of claim 6 , wherein each of the first subset of electrical switches and the second subset of electrical switches consists of a pair of blocking switches electrically coupled in series.

9. The inverter of claim 1 , wherein the active filter comprises at least one energy storage device, a half-bridge switching circuit, and a capacitor divider electrically coupled to the at least one energy storage device and the half-bridge switching circuit.

10. The inverter of claim 9 , wherein the third winding includes a first terminal and a second terminal;
wherein the half-bridge switching circuit comprises a first electrical switch electrically coupled to a second electrical switch and the first terminal at a first node; and
wherein the capacitor divider comprises a first capacitor electrically coupled to a second capacitor and the second terminal at a second node.

11. The inverter of claim 10 , wherein the active filter is electrically coupled to the common reference electrical interconnect at the second node.

12. An inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid, the inverter comprising:
a transformer that includes a first winding and a second winding;
a DC-AC inverter electrically coupled to the first winding of the transformer, wherein the DC-AC inverter is adapted to convert the DC waveform to an AC waveform delivered to the transformer at the first winding;
a cycloconverter electrically coupled to the second winding of the transformer via a first connection and to the DC-AC inverter via a common reference electrical interconnect, wherein the cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid; and
an active filter electrically coupled to the second winding of the transformer, wherein the active filter is adapted to sink and source power with one or more energy storage devices based on an instantaneous mismatch in power between the DC source and the AC grid.

13. The inverter of claim 12 , wherein the cycloconverter comprises a set of electrical switches and a capacitor divider electrically coupled with the set of electrical switches.

14. The inverter of claim 13 , wherein the second winding includes a first terminal and a second terminal;
wherein the set of electrical switches comprises a first subset of electrical switches electrically coupled to a second subset of electrical switches at a first node;
wherein the capacitor divider comprises a first capacitor electrically coupled to a second capacitor and the first terminal at a second node; and
wherein the cycloconverter comprises an inductor electrically coupled in series to the second terminal and the first node.

15. The inverter of claim 14 , wherein the active filter comprises at least one energy storage device, a half-bridge switching circuit, and a second capacitor divider electrically coupled to the at least one energy storage device and the half-bridge switching circuit.

16. The inverter of claim 15 , wherein the half-bridge switching circuit comprises a first electrical switch and a second electrical switch electrically coupled to the inductor and the second terminal at a common node; and
wherein the second capacitor divider comprises a third capacitor and a fourth capacitor electrically coupled to the first terminal at the second node.

17. An inverter for converting an input direct current (DC) waveform from a DC source to an output alternating current (AC) waveform for delivery to an AC grid, the inverter comprising:
a controller having a processor and a memory;
a transformer that includes a first winding and a second winding;
a DC-AC inverter electrically coupled to the first winding of the transformer, wherein the DC-AC inverter is adapted to converter the DC waveform to an AC waveform delivered to the transformer at the first winding;
a cycloconverter electrically coupled to the second winding of the transformer and to the DC-AC inverter via a common reference electrical interconnect, wherein the cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid; and
an active filter electrically coupled to the second winding of the transformer and comprising a plurality of electrical switches and one or more energy storage devices,
wherein the controller is adapted to control the switching cycles of the plurality of electrical switches of the active filter to sink and source power with the one or

Assignees

• Sunpower Corp

Inventors

• Rodriguez Fernando

Classifications

• H02M7/5387

  in a bridge configuration · CPC title

• H02M5/16

  for conversion of frequency · CPC title

• H02M7/4807

  having a high frequency intermediate AC stage · CPC title

• H02J7/34

  Parallel operation in networks using both storage and other DC sources, e.g. providing buffering (H02J7/14 takes precedence) · CPC title

• H02M5/458

  using semiconductor devices only · CPC title