Solar inverter and control method

• US 8,184,460 B2
• Filed: 05/28/2009
• Issued: 05/22/2012
• Est. Priority Date: 05/28/2009
• Status: Active Grant

• Current Assignee: GE Grid Solutions LLC (GE Vernova, Inc.)
• Original Assignee: General Electric Company
• Inventors: O'Brien, Kathleen Ann, Teichmann, Ralph
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US12/473,700
• Publication Number:
  US 20100302819A1
• Time in Patent Office: 1,090 Days
• Field of Search: 363/55, 363/56.01, 363/95, 363/97, 363/98, 363/123, 363/131, 307/52
• US Class Current: 363/97
• 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 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A power generation system including a photovoltaic (PV) module to generate direct current (DC) power is provided. The system includes a controller to determine a maximum power point for the power generation system and a boost converter for receiving control signals from the controller to boost the power from the PV module to a threshold voltage required to inject sinusoidal currents into the grid. A DC to alternating current (AC) multilevel inverter is provided in the system to supply the power from the PV module to a power grid. The system also includes a bypass circuit to bypass the boost converter when an input voltage of the DC to AC multilevel inverter is higher than or equal to the threshold voltage.

Claims

1. A power generation system comprising:

a photovoltaic (PV) module to generate direct current (DC) power;

a controller for determining a maximum power point for the power generation system;

a boost converter comprising boost inductors, diodes, and switching devices for receiving control signals from the controller to boost the power from the PV module to a threshold voltage required to inject sinusoidal currents into the grid;

a direct current (DC) to alternating current (AC) multilevel inverter to supply the power from the PV module to a power grid; and

a bypass circuit for bypassing the boost inductors, diodes, and switching devices of the boost converter when an input voltage of the DC to AC multilevel inverter is higher than or equal to the threshold voltage.

2. The system of claim 1, wherein the controller is further configured to send MPPT control signals to the boost converter under normal operating conditions and to send MPPT control signals to the multilevel DC/AC inverter during bypass operating conditions.

3. The system of claim 1, wherein the boost converter comprises a two inductor boost converter.

4. The system of claim 1, wherein the boost converter comprises two diodes and two switching devices.

5. The system of claim 1, wherein the boost converter comprises one switching device and four diodes.

6. The system of claim 4, wherein the switching devices comprise an insulated gate bipolar transistor or a power metal oxide field effect transistor.

7. The system of claim 1, wherein an output stage of the boost converter comprises a split DC link.

8. The system of claim 7, wherein the split DC link is coupled between the boost converter and the multilevel inverter.

9. The system of claim 7, wherein the split DC link comprises two capacitors with a center tap in between.

10. The system of claim 9, wherein the two inductor boost converter controls a voltage at the center tap.

11. The system of claim 1, wherein the multilevel inverter is selected from a diode clamped multilevel inverter, a flying capacitor multilevel inverter and a cascaded H-bridge multilevel inverter.

12. The system of claim 1, wherein the multilevel inverter comprises a three level inverter.

13. The system of claim 1, wherein the bypass circuit comprises a power diode.

14. The system of claim 1, wherein the bypass circuit comprises two silicon carbide diodes.

15. The system of claim 1, wherein the multilevel inverter is configured to directly obtain maximum power from the PV module when the boost converter is bypassed.

18. The system of claim 1, wherein the bypass circuit comprises a voltage controlled switch.

16. A method of delivering solar power from a power generation system comprising a photovoltaic (PV) module, the method comprising:

determining a threshold voltage for generating sinusoidal currents for the power generation system;

determining whether an output voltage of the PV module at maximum power production is higher than the threshold voltage;

when the output voltage of the PV module is less than the threshold voltage, boosting the power from the PV module to achieve the threshold voltage level via a boost converter comprising boost inductors, diodes, and switches and then converting the boosted power to alternating current (AC) power; and

when the output voltage of the PV module is higher than the threshold voltage, bypassing the boost inductors, diodes, and switches of the boost converter and directly converting the power from the PV module to AC power.

17. The method of claim 16, further comprising, when the output voltage of the PV module is higher than the threshold voltage, using MPPT control signals when directly converting the power from the PV module to AC power.