Power conditioning units

• US 10,193,467 B2
• Filed: 06/16/2017
• Issued: 01/29/2019
• Est. Priority Date: 01/13/2006
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Inc.
• Inventors: Chisenga, Lesley, Amaratunga, Gehan Anil Joseph, Rodriguez, Cuauhtemoc
• Primary Examiner(s): Mehari, Yemane
• Application Number:
  US15/625,862
• Publication Number:
  US 20170288406A1
• Time in Patent Office: 592 Days
• Field of Search: 363 24, 363 37, 363 40, 363 41, 363 95, 363131, 363132
• 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 3/40 Synchronising a generator for connection to a network or to another generator
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• 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 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 5/45 using semiconductor devices only
• 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: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

We describe a power conditioning unit with maximum power point tracking (MPPT) for a dc power source, in particular a photovoltaic panel. A power injection control block has a sense input coupled to an energy storage capacitor on a dc link and controls a dc-to-ac converter to control the injected mains power. The power injection control block tracks the maximum power point by measuring a signal on the dc link which depends on the power drawn from the dc power source, and thus there is no need to measure the dc voltage and current from the dc source. In embodiments the signal is a ripple voltage level and the power injection control block controls an amplitude of an ac current output such that an amount of power transferred to the grid mains is dependent on an amplitude of a sinusoidal voltage component on the energy storage capacitor.

Claims

1. A power conditioning unit comprising:

a controller;

a DC input for receiving DC power from an energy generation device;

a DC to DC converter coupled to the DC input and to an energy storage device; and

a DC to AC converter coupled to the energy storage device and to an AC grid, the DC to AC converter converting energy stored in the energy storage device to AC power and outputting it in synchronization with the AC grid, wherein the controller uses a measurement taken from the energy storage device to maintain operation of the power conditioning unit at a maximum power point of the energy generation device.

2. The power conditioning unit of claim 1 wherein the controller maintains operation of the power conditioning unit at the maximum power point by controlling the DC to AC converter converting energy stored in the energy storage device to AC power for output to the AC grid.

3. The power conditioning unit of claim 2 wherein the controlling the DC to AC converter includes:

sensing, at a circuit node coupled to the energy storage device, a signal responsive to a level of DC power received from the energy generation device; and

controlling the DC to AC converter to adjust an amplitude of the AC power output in synchronization with the AC grid to substantially maximize the sensed signal.

4. The power conditioning unit of claim 3 wherein the sensed signal is used to derive a control signal having an amplitude dependent on the level of DC power received from the energy generation device.

5. The power conditioning unit of claim 2 wherein the DC to AC converter is controlled by increasing or decreasing a switching rate of the DC to AC converter.

6. The power conditioning unit of claim 1 wherein the energy storage device comprises a capacitor.

7. The power conditioning unit of claim 1 further comprising a DC voltage amplification stage coupled between the energy generation device and the energy storage device.

8. The power conditioning unit of claim 7 wherein the DC voltage amplification stage has a substantially constant amplification factor.

9. The power conditioning unit of claim 7 further comprising a DC voltage amplification stage control block configured to regulate power flow from the energy generation device to the DC to AC converter.

10. The power conditioning unit of claim 1 wherein the energy generation device includes one or more photovoltaic panels.

11. A power conditioning unit comprising:

an input for receiving power from an energy generation device;

an output for delivering AC power to an AC grid;

an energy storage device coupled to the input for storing energy from the energy generation device;

a DC to AC converter coupled between the energy storage device and the AC grid; and

a controller for controlling the DC to AC converter to maintain operation of the power conditioning unit at a maximum power point of the energy generation device based on a measurement taken from the energy storage device.

12. The power conditioning unit of claim 11 wherein the controller maintains operation of the power conditioning unit at the maximum power point by controlling the DC to AC converter converting energy stored in the energy storage device to AC power for output to the AC grid.

13. The power conditioning unit of claim 12 wherein the controlling the DC to AC converter includes:

sensing, at a circuit node coupled to the energy storage device, a signal responsive to a level of DC power received from the energy generation device; and

controlling the DC to AC converter to adjust an amplitude of the AC power delivered to the AC grid to substantially maximize the sensed signal.

14. The power conditioning unit of claim 13 wherein the sensed signal is used to derive a control signal having an amplitude dependent on the level of DC power received from the energy generation device.

15. The power conditioning unit of claim 11 wherein the DC to AC converter is controlled by increasing or decreasing a switching rate of the DC to AC converter.

16. The power conditioning unit of claim 11 wherein the energy storage device comprises a capacitor.

17. The power conditioning unit of claim 11 further comprising a DC voltage amplification stage coupled between the energy generation device and the energy storage device.

18. The power conditioning unit of claim 17 wherein the DC voltage amplification stage has a substantially constant amplification factor.

19. The power conditioning unit of claim 17 further comprising a DC voltage amplification stage control block configured to regulate power flow from the energy generation device to the DC to AC converter.

20. The power conditioning unit of claim 11 wherein the energy generation device includes one or more photovoltaic panels.