Solar photovoltaic systems

• US 8,674,668 B2
• Filed: 11/16/2010
• Issued: 03/18/2014
• Est. Priority Date: 06/07/2010
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Enecsys Limited
• Inventors: Chisenga, Lesley, Engle, Paul Randal Jr., Matthews, Andrew John
• Primary Examiner(s): Behm, Harry
• Application Number:
  US12/947,116
• Publication Number:
  US 20110298305A1
• Time in Patent Office: 1,218 Days
• Field of Search: 323/906, 323/266, 363/95
• US Class Current: 323/266
• 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: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• 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 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• 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

Abstract

We describe a photovoltaic (PV) power generation system comprising at least two PV panels and a power conditioning unit. The dc power outputs of the PV panels are connected in parallel to a dc power input of the power conditioning unit. The power conditioning unit comprises a dc-to-dc converter having an input coupled to the dc power input and an output coupled to a dc link of the unit, a dc-to-ac converter having an input coupled to the dc link and an ac mains power supply output, and an energy storage capacitor coupled to the dc link. The power conditioning unit is configured to perform maximum power point tracking (MPPT) responsive to a level of power flowing into the dc power input, and the level of power flowing into said dc power input is sensed at the dc link. In preferred implementations the energy storage capacitor is a non-electrolytic capacitor.

Claims

1. A photovoltaic power generation system, the system comprising:

at least two photovoltaic panels each having a dc power output;

a power conditioning unit having a dc power input and an ac mains power supply output for delivering ac power to an ac mains power supply;

wherein said dc power outputs of said at least two photovoltaic panels are connected in parallel with one another to said dc power input of said power conditioning unit;

wherein said power conditioning unit comprises;

a dc-to-dc converter having an input coupled to said dc power input and having an output coupled to a dc link of said power conditioning unit;

a dc-to-ac converter having an input coupled to said dc link and having an output coupled to said ac mains power supply output; and

an energy storage capacitor coupled to said dc link;

wherein said power conditioning unit is configured to perform maximum power point tracking (MPPT) responsive to a level of power flowing into said dc power input, wherein said level of power flowing into said dc power input is sensed at said dc link;

wherein said power conditioning unit comprises an MPPT controller coupled to control said dc-to-ac converter to perform said maximum power point tracking (MPPT);

wherein said controller has a sense input coupled to said energy storage capacitor to sense at said energy storage capacitor a signal responsive to the level of power flowing into said dc power input of said power conditioning unit, and wherein said controller is configured to perform said MPPT by controlling said dc-to-ac converter to control power injected into said ac mains power supply responsive to said level of power flowing into said dc power input of said power conditioning unit sensed at said dc link and

wherein said ac mains power supply output is a three phase output, and wherein said power conditioning unit comprises one said dc-to-ac converter per phase, each coupled to said dc link.

2. A photovoltaic power generation system as claimed in claim 1 wherein a voltage on said energy storage capacitor has a sinusoidal voltage component at twice a frequency of said ac mains power supply, wherein said sense input of said controller senses a value of said sinusoidal voltage component, and wherein said controller is configured to control an amplitude of an ac current provided to said ac mains power supply output such that an amount of power transferred to said ac mains power supply output is dependent on an amplitude of said sinusoidal voltage component on said energy storage capacitor.

3. A photovoltaic power generation system as claimed in claim 2 wherein said controller is configured to control said amplitude of said ac current provided to said ac mains power supply output to substantially maximize said value of said sinusoidal voltage component.

4. A photovoltaic power generation system as claimed in claim 1 wherein said controller is configured to control said dc-to-ac converter to track a maximum power point of said dc power outputs without directly measuring a dc voltage or dc current provided from said dc power outputs.

5. A photovoltaic power generation system as claimed in claim 1 wherein said power conditioning unit has a single, common MPPT control system for said at least two photovoltaic panels.

6. A photovoltaic power generation system as claimed in claim 1 wherein said energy storage capacitor is a non-electrolytic capacitor.

7. A photovoltaic power generation system as claimed in claim 1 wherein said power conditioning unit comprises a single said dc-to-ac converter coupled to said parallel-connected photovoltaic panels.

8. A photovoltaic power generation system as claimed in claim 1 wherein respective positive and negative terminals of said photovoltaic panels are connected to one another.

9. A photovoltaic power generation system as claimed in claim 1 wherein said photovoltaic panels comprise parallel series-connected panels, wherein said photovoltaic panels are connected in parallel to one another via one or more intermediate respective series-connected panels.

10. A photovoltaic power generation system, the system comprising:

a first plurality of photovoltaic panels connected in series with each other having a first positive connection and a first negative connection at either end of the first plurality of photovoltaic panels connected in series;

a second plurality of photovoltaic panels connected in series with each other having a second positive connection and a second negative connection at either end of the second plurality of photovoltaic panels connected in series;

a power conditioning unit having a dc power input and an ac mains power supply output for delivering ac power to an ac mains power supply;

wherein the dc power input comprises a positive connection and a negative connection;

wherein the first plurality of photovoltaic panels and the second plurality of photovoltaic panels are connected in parallel with one another by coupling the first and second positive connections together and the first and second negative connections together, wherein the first and second positive connections are coupled to the positive connection of said dc power input of said power conditioning unit and the first and second negative connections are coupled to the negative connection of said dc power input of said power conditioning unit;

wherein said power conditioning unit comprises a dc-to-ac converter, and a dc link coupled to said dc power input of said power conditioning unit and an input of said dc-to-ac converter, wherein said power conditioning unit does not include a voltage-increasing dc-to-dc converter between said dc power input and said dc link, wherein said dc-to-ac converter has an output coupled to said ac mains power supply output, and wherein said power conditioning unit further comprises an energy storage capacitor coupled to said dc link;

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

wherein said power conditioning unit is configured to perform maximum power point tracking (MPPT) responsive to a level of power flowing into said dc power input; and

a controller configured to control an amplitude of an ac current provided to said ac mains power supply output such that an amount of power transferred to said ac mains power supply output is dependent on a peak amplitude of a fluctuating sinusoidal component of a dc voltage on said energy storage capacitor, wherein said controller has a sense input coupled to said energy storage capacitor to sense at said energy storage capacitor a signal responsive to the level of power flowing into said dc power input of said power conditioning unit, and a control output to control said dc-to-ac converter such that the amplitude of the ac current provided to said ac mains power supply output is dependent on an amplitude of said sinusoidal voltage component on said energy storage capacitor, and wherein said controller is configured to perform said MPPT by controlling said dc-to-ac converter.

11. A photovoltaic power generation system as claimed in claim 10 configured to control the amplitude of the ac current provided to said ac mains power supply output such that the amount of power transferred to said ac mains power supply output is dependent on the peak amplitude of the fluctuating sinusoidal component of the dc voltage on said energy storage capacitor to control power injected into said ac mains power supply responsive to said level of power flowing into said dc power input of said power conditioning unit sensed at said dc link.

12. A photovoltaic power generation system as claimed in claim 10 wherein said ac mains power supply output is a three phase output, and wherein said power conditioning unit comprises one said dc-to-ac converter per phase each coupled to a common said dc link.