Bidirectional energy converter with controllable filter stage

• US 8,971,057 B2
• Filed: 03/24/2010
• Issued: 03/03/2015
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Stem, Inc.
• Original Assignee: Stem, Inc.
• Inventors: Smith, Lynn B.
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Quddus, Nusrat
• Application Number:
  US12/731,070
• Publication Number:
  US 20100244775A1
• Time in Patent Office: 1,805 Days
• Field of Search: 323/205, 323/207, 363/15, 363/17, 363/34, 363/89, 363/95, 363/98, 363/37, 363/39, 363/40, 363/44, 363/45, 363/48, 363/126, 363/131, 363/133
• US Class Current: 363/15
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02M 3/33584 Bidirectional converters
• CPC Class Codes: H02M 7/797 using semiconductor devices only

Abstract

The invention provides a bidirectional converter that operates under an AC generation mode or a charge mode. The bidirectional converter may be a single component or circuit, which may include a DC-DC conversion stage using a unique “Smith 2 Stage conversion” technique and a DC-AC conversion stage or AC-DC conversion stage using a switchable filter depending on the mode. During the charge mode, the converter may be able to control the voltage and current of the DC output using a software algorithm, to match the battery being charged, or the DC receiver. This may enable the converter to control the nature of the DC output so it can be adapted to any energy storage technology. The controllable output voltage and synchronizable frequency may allow the converter to be used in series combinations to achieve a variety of high voltage outputs from simpler building blocks.

Claims

1. A bidirectional converter comprising:

at least one DC terminal;

at least one AC terminal;

a DC-DC conversion stage disposed between the DC terminal and the AC terminal;

a bridge conversion stage disposed between the DC-DC conversion stage and the AC terminal, wherein the bridge conversion stage is selectively operable to invert a current when the current is flowing from the DC terminal to the AC terminal and to rectify the current when the current is flowing from the AC terminal to the DC terminal; and

a controllable filter stage disposed between the DC-DC conversion stage and the bridge conversion stage that is selectively operable to disable a filter when the bridge conversion stage is operable to invert the current and to enable the filter when the bridge conversion stage is operable to rectify the current.

2. The converter of claim 1, further comprising a single digital signal processor.

3. The converter of claim 2, wherein the single digital signal processor provides a plurality of pulse width modulated (PWM) outputs.

4. The converter of claim 1, further comprising a plurality of digital signal processors.

5. The converter of claim 4, wherein the plurality of digital signal processors are microcontrollers or microprocessors.

6. The converter of claim 1, wherein the DC-DC conversion stage includes a plurality of transistors driving an isolation transformer.

7. The converter of claim 6, wherein the transistors are configured to receive a drive waveform that operates at a 50% duty cycle.

8. The converter of claim 1, wherein the bridge conversion stage includes an “

H”

bridge.

9. The converter of claim 8 wherein the output of the “

H”

bridge passes through a low pass filter.

10. The converter of claim 1 wherein the converter may be able to switch between inverting a current and rectifying the current within milliseconds.

11. The converter of claim 1 wherein the bridge conversion stage utilizes a Smith 2 Stage Conversion technique.

20. The converter of claim 2, wherein the controllable filter stage is controllable via an output of the digital signal processor.

21. The converter of claim 4, wherein the controllable filter stage is controllable via an output of a digital signal processor included in the plurality of digital signal processors.

12. A method for modifying a current, said method comprising:

providing at least one AC terminal and at least one DC terminal;

providing a DC-DC conversion between the AC terminal and the DC terminal;

providing a bridge conversion disposed between the DC-DC conversion and the AC terminal;

causing the bridge conversion to invert a current when the current is flowing from the DC terminal to the AC terminal and to rectify the current when the current is flowing from the AC terminal to the DC terminal, wherein said inverting and rectifying occur when current is flowing within the same circuit;

providing a controllable filter stage disposed between the DC-DC conversion and the bridge conversion; and

causing the controllable filter stage to selectively disable a filter when the bridge conversion is inverting the current and to enable the filter when the bridge conversion is rectifying the current.

13. The method of claim 12 wherein the bridge conversion includes an “

H”

bridge which provides a sine wave output when the current is flowing from the DC to the AC terminal, and which receives a sine wave input when the current is flowing from the AC terminal to the DC terminal.

14. The method of claim 13 wherein the “

H”

bridge communicates with a digital signal processor via pulse width modulated signal.

15. The method of claim 12 wherein the bridge conversion utilizes a Smith 2 Stage Conversion technique.

16. The method of claim 12 further comprising providing a plurality of digital signal processors that may control input and output functions between the AC terminal the DC terminal while remaining electrically isolated from one another.

17. The method of claim 12 wherein the DC-DC conversion is performed using a plurality of rectifiers, wherein a first set of rectifiers operate at a first duty cycle, and the second set of rectifiers operate at a second duty cycle.

18. The method of claim 12 wherein the current modification switches between inverting the current and rectifying the current within milliseconds.

19. The method of claim 12 further comprising controlling the AC voltage and frequency, thereby permitting the control of the output AC voltage between 110 VAC and 138 VAC and allowing series operation with multiple units to achieve higher voltages.