Inverter for a Distributed Power Generator

• US 20100236612A1
• Filed: 02/19/2010
• Published: 09/23/2010
• Est. Priority Date: 02/20/2009
• Status: Active Grant

• Current Assignee: SPARQ Systems, Inc.
• Original Assignee: SPARQ Systems, Inc.
• Inventors: Jain, Praveen, Bakhshai, Alireza, Khajehoddin, Sayed Ali
• Granted Patent: US 8,670,249 B2
• Time in Patent Office: Days
• US Class Current: 136/252
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

Provided is a maximum power point (MPP) tracker for a PV cell inverter, and a PV cell inverter. The MPP tracker decouples output power oscillations from the input power generation and extracts maximum available power from the PV cell. The PV cell inverter uses the MPP tracker and generates a sinusoidal output current from the MPP tracker output. The sinusoidal output current may be fed to a power distribution grid. The PV cell inverter may use a pulse width modulation technique to cancel harmonics in the sinusoidal output current. The circuits use a minimum number of components and avoid use of large electrolytic capacitors.

Claims

1. A circuit for use with a distributed power generator, comprising:

a high side input point and a low side input point for the distributed power generator;

a high side output point and a low side output point; and

(i) a parallel input capacitor; and

a means that regulates voltage across the capacitor;

wherein regulating voltage across the capacitor substantially removes distributed power generator input voltage oscillation;

or

(ii) a series input inductor; and

a means that regulates current through the series input inductor;

wherein regulating current through the series input inductor substantially removes distributed power generator input current oscillation.

2. The circuit of claim 1, wherein voltage across the capacitor is regulated between a lower limit and an upper limit.

3. The circuit of claim 1, wherein the means that regulates voltage across the capacitor comprises:

a switch connected between the high side input point and a node;

an output inductor connected between the node and the high side output point; and

a diode connected between the node and the low side output point.

4. The circuit of claim 3, wherein the upper limit is a reference voltage and the lower limit is calculated so that a switching frequency of the switch and the distributed power generator input voltage oscillation or input current oscillation do not exceed selected values.

5. The circuit of claim 4, wherein the reference voltage is obtained from a maximum power point tracking (MPPT) algorithm.

6. The circuit of claim 1, including a controller for the switch.

7. The circuit of claim 6, wherein the controller is a hysteresis controller.

8. The circuit of claim 1, wherein current through the series input inductor is regulated between a lower limit and an upper limit.

9. The circuit of claim 8, wherein the means that regulates current through the series input inductor comprises:

a switch connected between the series input inductor output and the low side input point; and

a diode connected in series between the series input inductor and the high side output point.

10. The circuit of claim 8, wherein the upper limit is a reference current and the lower limit is calculated so that a switching frequency of the switch and the distributed power generator input current oscillation do not exceed selected values.

11. The circuit of claim 10, wherein the reference current is obtained from a maximum power point tracking (MPPT) algorithm.

12. The circuit of claim 8, including a controller for the switch.

13. The circuit of claim 12, wherein the controller is a hysteresis controller.

14. The circuit of claim 1, wherein the distributed power generator is a photovoltaic cell.

15. An inverter for a distributed power generator, comprising:

the circuit of claim 1; and

a means that generates a sinusoidal output current from the circuit output.

16. The inverter of claim 15, wherein:

the circuit includes a parallel input capacitor and a means that regulates voltage across the capacitor, and the inverter comprises a current source inverter;

or

(ii) the circuit includes a series input inductor and a means that regulates current through the series input inductor, and the inverter comprises a voltage source inverter.

17. The inverter of claim 15, wherein the distributed power generator is a photovoltaic cell.

19. The inverter of claim 15, including a compensator, wherein the compensator modifies a pulse width modulation (PWM) reference signal of the voltage source inverter or the current source inverter, to cancel one or more harmonic in the voltage source inverter or current source inverter output current.

20. The inverter of claim 19, wherein the distributed power generator is a photovoltaic cell.

18. A compensator for use with a voltage source inverter or a current source inverter, wherein the compensator modifies a pulse width modulation (PWM) reference signal of the voltage source inverter or current source inverter, to cancel one or more harmonic in the voltage source inverter or current source inverter output current.

21. A method for obtaining power from a distributed power generator, comprising:

(i) connecting a capacitor across the output voltage of the distributed power generator; and

actively regulating voltage across the capacitor;

wherein regulating voltage across the capacitor substantially removes distributed power generator voltage oscillation;

or

(ii) connecting a series input inductor to the output of the distributed power generator; and

actively regulating current through the inductor;

wherein regulating current through the inductor substantially removes distributed power generator current oscillation.

22. The method of claim 21, comprising:

using a switch to regulate the voltage across the capacitor;

or

(ii) using a switch to regulate the current through the inductor.

23. The method of claim 22, including regulating the voltage across the capacitor between an upper limit and a lower limit.

24. The method of claim 23, wherein the upper limit is a reference voltage and the lower limit is calculated so that a switching frequency of the switch and the distributed power generator input voltage oscillation or input current oscillation do not exceed selected values.

25. The method of claim 23, comprising using hysteresis to control the switch.

26. The method of claim 21, wherein the distributed power generator is a photovoltaic cell.

27. A method for obtaining power from a distributed power generator and producing a sinusoidal output current, comprising:

(i) connecting a capacitor across the output voltage of the distributed power generator;

actively regulating voltage across the capacitor to substantially remove distributed power generator voltage oscillation; and

using a current source inverter to produce the sinusoidal output current;

or

(ii) connecting a series input inductor to the output of the distributed power generator;

actively regulating current through the inductor to substantially remove distributed power generator current oscillation; and

using a voltage source inverter to produce the sinusoidal output current.

28. The method of claim 27, further comprising connecting the sinusoidal output voltage or current to a power distribution grid.

29. The method of claim 27, wherein the distributed power generator is a photovoltaic cell.

31. The method of claim 27, further comprising modifying a pulse width modulation (PWM) reference signal of the voltage source inverter or current source inverter to cancel one or more harmonic in the voltage source inverter or current source inverter output current.

32. The method of claim 31, wherein the distributed power generator is a photovoltaic cell.

30. A method of obtaining power from voltage source inverter or a current source inverter, comprising modifying a pulse width modulation (PWM) reference signal of the voltage source inverter or current source inverter to cancel one or more harmonic in the voltage source inverter or current source inverter output current.