BIDIRECTIONAL ENERGY CONVERTER

• US 20100244775A1
• Filed: 03/24/2010
• Published: 09/30/2010
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Stem, Inc.
• Original Assignee: Stem, Inc.
• Inventors: Smith, Lynn B.
• Granted Patent: US 8,971,057 B2
• Time in Patent Office: Days
• US Class Current: 320/140
• 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; and

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.

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 2, 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 4, 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 6 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.

12. A battery charger comprising:

one or more synchronous rectifiers that provide a voltage and current;

a current sense configured to sense current into or out of a battery; and

a digital signal processor configured to provide a pulse width modulated output to the one or more synchronous rectifiers and receive current sensing data from the current sense,

wherein the digital signal processor controls the pulse width modulated output to achieve a desired voltage and current based on the received current sensing data.

13. The battery charger of claim 12 comprising a plurality of digital signal processors.

14. The battery charger of claim 13 wherein the pulse width modulated output controls the voltage on a bus across a capacitor.

15. The battery charger of claim 14 wherein the voltage on the bus is inputted to a second digital signal processor and relied upon by the second digital signal processor to control the pulse width modulated output.

16. The battery charger of claim 12 further comprising a DC to DC converter driver stage.

17. The battery charger of claim 16, further comprising a filter that eliminates high frequency noise from the output of the DC to DC converter drive stage when the battery charger is operating in a charge mode, and that isolates noise and electrical transients generated in the DC to DC converter driver stage from being reflected to a battery bus circuit when the battery charger is operating in an inverter mode.

18. The battery charger of claim 13 wherein an isolated data path is provided between the plurality of digital signal processors.

19. The battery charger of claim 12 wherein the one or more synchronous rectifiers utilizes a switchable filter to provide the voltage and current.

20. 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;

inverting a current when the current is flowing from the DC terminal to the AC terminal, and rectifying 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.

21. The method of claim 20 further comprising providing a bridge conversion disposed between the DC-DC conversion and the AC terminal.

22. The method of claim 21 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.

23. The method of claim 22 wherein the “

H”

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

24. The method of claim 21 wherein the bridge conversion utilizes a Smith 2 Stage Conversion technique.

25. The method of claim 20 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.

26. The method of claim 20 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.

27. The method of claim 20 wherein the current modification switches between inverting the current and rectifying the current within milliseconds.

28. The method of claim 20 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.