PHOTOVOLTAIC INVERTER SYSTEM AND METHOD OF STARTING SAME AT HIGH OPEN-CIRCUIT VOLTAGE

• US 20120026769A1
• Filed: 07/29/2010
• Published: 02/02/2012
• Est. Priority Date: 07/29/2010
• Status: Active Grant

• Current Assignee: GE Grid Solutions LLC (GE Aerospace)
• Original Assignee: General Electric Company
• Inventors: Schroeder, Stefan, Shen, Jie, El-Barbari, Said Farouk Said, Roesner, Robert
• Granted Patent: US 8,395,919 B2
• Time in Patent Office: Days
• US Class Current: 363/131
• CPC Class Codes: H02J 2300/22 The renewable source being solar energy
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• 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

A power inverter system includes a DC to AC inverter configured to convert DC voltage from a DC power source to AC voltage. A DC link couples the DC power source and the inverter. An inverter pre-charger operates to pre-charge the inverter to achieve a desired DC link voltage prior to connecting the power inverter system to an AC power grid. A phased lock loop synchronizes the pre-charged inverter to the AC power grid prior to connecting the power inverter system to the AC power grid. The pre-charged inverter regulates the DC link voltage to about the minimum voltage level that allows control of AC grid currents via the inverter subsequent to connecting the power inverter system to the AC grid. The inverter operates in a maximum power point tracking control mode only subsequent to a first voltage transient caused by connecting the DC power source to energize the power inverter system.

Claims

1. A power inverter system, comprising:

a DC power source;

a DC to AC inverter configured to convert DC voltage from the DC power source to AC voltage;

a DC link coupling the DC power source and the inverter, the DC link having a DC link voltage;

an inverter pre-charger configured to pre-charge the inverter to achieve a desired DC link voltage prior to connecting the power inverter system to an AC power grid; and

a phased lock loop configured to synchronize the pre-charged inverter to the AC power grid prior to connecting the power inverter system to the AC power grid, wherein the pre-charged inverter is further configured to regulate the DC link voltage to about the minimum voltage level that allows control of AC grid currents via the inverter subsequent to connecting the power inverter system to the AC grid, and further wherein the inverter is further configured to operate in a maximum power point tracking control mode subsequent to a first voltage transient caused by connecting the DC power source to the power inverter system.

2. The power inverter system according to claim 1, wherein the DC power source comprises a photovoltaic array.

3. The power inverter system according to claim 1, further comprising a DC to AC inverter control system, wherein the inverter is configured to regulate the DC link voltage in response to commands received via the inverter control system.

4. The power inverter system according to claim 3, wherein the control system is integral to the inverter.

5. The power inverter system according to claim 3, wherein the control system is external to the inverter.

6. The power inverter system according to claim 3, further comprising a DC to DC converter configured to boost the DC voltage generated via the DC power source.

7. The power inverter system according to claim 6, further comprising a DC to DC converter control system, wherein the DC to DC converter is configured to operate in the maximum power point tracking control mode subsequent to the first voltage transient and in response to commands received from the DC to DC converter control system.

8. The power inverter system according to claim 7, wherein the DC to DC converter control system is integral to the DC to DC converter.

9. The power inverter system according to claim 7, wherein the DC to DC converter control system is external to the DC to DC converter.

10. The power inverter system according to claim 7, wherein the DC to DC converter control system is integrated with the inverter control system.

11. The power inverter system according to claim 1, further comprising a switching mechanism configured to connect the power inverter system to the AC power grid.

12. The power inverter system according to claim 11, further comprising a switching mechanism configured to connect the power inverter system to the DC power source.

13. A method of operating a power inverter system, the method comprising:

pre-charging a DC to AC inverter to achieve a desired DC link voltage that is less than a predetermined DC voltage source open circuit voltage;

synchronizing the resultant inverter output voltage to a predetermined AC power grid voltage via a phase-locked loop

connecting the synchronized inverter to the AC power grid;

activating a DC link voltage control and regulating the DC link voltage to about the minimum level that allows control of grid currents generated via the inverter; and

connecting the DC voltage source to the power inverter system subsequent to activating the DC link voltage control and regulating the DC link voltage to about the minimum level, such that the inverter adjusts power to the AC power grid to maintain a constant DC link voltage, and further such that the inverter commences maximum power point tracking control subsequent to the first DC voltage source voltage transient following connection of the DC voltage source to the power inverter system.

14. The method of operating a power inverter system according to claim 13, wherein regulating the DC to AC inverter comprises overmodulating the inverter.

15. The method of operating a power inverter system according to claim 13, wherein regulating the DC to AC inverter comprises inputting reactive power to the inverter from the AC power grid.

16. The method of operating a power inverter system according to claim 13, wherein connecting the DC voltage source to the power inverter system comprises closing a circuit breaker.

17. A method of operating a power inverter system, the method comprising:

pre-charging a DC to AC inverter to achieve a desired DC link voltage that is less than a predetermined DC voltage source open circuit voltage;

synchronizing the resultant inverter output voltage to a predetermined AC power grid voltage via a phase-locked loop

connecting the synchronized inverter to the AC power grid;

activating a DC link voltage control and regulating the DC link voltage to about the minimum level that allows control of grid currents generated via the inverter;

activating a DC-DC converter and a corresponding maximum power point (MPP) voltage control mechanism and regulating the converter input voltage to about the minimum voltage level; and

connecting the DC voltage source to the power inverter system subsequent to activating the converter and regulating the converter input voltage to about the minimum level, such that the converter commences maximum power point tracking control subsequent to the first DC voltage source voltage transient following connection of the DC voltage source to the power inverter system.

18. The method of operating a power inverter system according to claim 17, wherein regulating the DC to AC inverter comprises overmodulating the inverter.

19. The method of operating a power inverter system according to claim 17, wherein regulating the DC to AC inverter comprises inputting reactive power to the inverter from the AC power grid.

20. The method of operating a power inverter system according to claim 17, wherein connecting the DC voltage source to the power inverter system comprises closing a circuit breaker.