POWER CONDITIONING UNIT

• US 20120033463A1
• Filed: 10/19/2011
• Published: 02/09/2012
• Est. Priority Date: 01/13/2006
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Enecsys Limited
• Inventors: Rodriguez, Cuauhtemoc
• Granted Patent: US 8,811,047 B2
• Time in Patent Office: Days
• US Class Current: 363/35
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

The present invention relates to a power conditioning unit for delivering power from a dc power source to an ac output, particularly ac voltages greater than 50 volts, either for connecting directly to a grid utility supply, or for powering mains devices independent from the mains utility supply. We describe a power conditioning unit for delivering power from a dc power source to an ac mains output, the power conditioning unit comprising an input for receiving power from said dc power source, an output for delivering ac power, an energy storage capacitor, a dc-to-dc converter having an input connection coupled to said input and an output connection coupled to the energy storage capacitor, and a dc-to-ac converter having an input connection coupled to said energy storage capacitor and an output connection coupled to said output, wherein said energy storage capacitor has a capacitance of less than twenty microfarads.

Claims

1. A solar power conditioning unit for delivering power from a solar or photovoltaic panel dc power source to an ac mains power supply output, the power conditioning unit comprising:

a power conditioning unit input for receiving power from said dc power source;

a power conditioning unit output for delivering ac power;

an energy storage capacitor;

a dc-to-dc converter having an input connection coupled to said power conditioning unit input and an output connection coupled to the energy storage capacitor; and

a dc-to-ac converter having an input connection coupled to said energy storage capacitor and an output connection coupled to said power conditioning unit output;

wherein said energy storage capacitor is a non-electrolytic capacitor; and

wherein said power conditioning unit comprises two control blocks, a first, power extraction control block to control said dc-to-dc converter to control power extracted from said dc power source and provided to said energy storage capacitor, and a second, power injection control block to control said dc-to-ac converter to control power injected into said ac mains power supply from said energy storage capacitor; and

wherein said power extraction control block has an input coupled to said power conditioning unit input for receiving power from said dc power source and has an output to control said dc-to-dc converter and is configured to regulate a voltage of said dc power source to control power extracted from said dc power source to said energy storage capacitor.

2. A power conditioning unit according to claim 1 wherein said two control blocks operate independently.

3. A power conditioning unit according to claim 2 wherein said two control blocks share a common microcontroller.

4. A power conditioning unit as claimed in claim 1 wherein said power injection control block has an input coupled to said energy storage capacitor and an output coupled to control said dc-to-ac converter and is configured to control an amplitude of an ac current provided to said ac mains power supply output.

5. A power conditioning unit as claimed in claim 1 wherein said power injected into said ac mains supply has a sinusoidal shape, and wherein said first control block is configured to extract a substantially constant power from said dc power source over a period of said sinusoidal shape.

6. A power conditioning unit as claimed in claim 5, wherein an instantaneous ac power output of said power conditioning unit has a sinusoidal shape, wherein said power extracted from said dc power source is substantially constant over a cycle of said ac power output, and wherein a difference between said power extracted from said dc power source and said instantaneous ac power output defines an energy mismatch which appears as said fluctuating sinusoidal component of said dc voltage on said energy storage capacitor.

7. A power conditioning unit according to claim 1 wherein said dc-to-dc converter comprises:

at least one power transistor for transferring power from the input connection of the dc-to-dc converter to the output connection of the dc-to-dc converter; and

wherein said power extraction control block comprises;

a sensing circuit for sensing a voltage on said input connection; and

a driver circuit for driving said at least one power transistor device responsive to said sensing to control said power transfer.

8. A power conditioning unit according to claim 7, wherein the power extraction control block further comprises a reference voltage generator, and wherein the driver circuit is configured to substantially minimise a difference between a reference voltage from said reference voltage generator and the sensed voltage.

9. A power conditioning unit according to claim 7 further comprising a system to perform maximum power point tracking of said dc power source by maintaining a voltage or current from the dc power source substantially at a reference voltage or current, wherein said system to perform maximum power point tracking is configured to control said at least one power transistor converter responsive both to a voltage or current from said dc power source and to a voltage or current on said energy storage capacitor.

10. A power conditioning unit as claimed claim 1 wherein said fluctuating sinusoidal component of said dc voltage on said energy storage capacitor has a frequency of twice that of said ac power.

11. A power conditioning unit according to claim 1, wherein said energy storage capacitor has a capacitance of less than twenty microfarads.

12. A power conditioning unit according to claim 11, wherein said energy storage capacitor comprises a film-type capacitor.

13. A power conditioning unit according to claim 1 wherein said dc-to-dc converter includes a transformer coupled between said input connection and said output connection.