Method and system for controlling a multi-stage power inverter

• US 8,611,107 B2
• Filed: 04/27/2011
• Issued: 12/17/2013
• Est. Priority Date: 04/27/2011
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Solarbridge Technologies Incorporated (Totalenergies Se)
• Inventors: Chapman, Patrick, O'Connell, Andrew, Sams, Timothy, Martina, Eric
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Pham, Emily P
• Application Number:
  US13/095,179
• Publication Number:
  US 20110261601A1
• Time in Patent Office: 965 Days
• Field of Search: 323/906, 363/15, 363/21.04, 363/21.12, 363/131, 363/132, 307/46, 307/82
• US Class Current: 363/21.04
• 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 1/007 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 3/33523 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

A method for controlling an multi-stage inverter comprises controlling an input converter of the multi-stage inverter with an input controller and controlling an output converter of the multi-stage inverter with an output controller separate from the input controller. The input controller and output controller may be galvanically isolated. Additionally, the method may include communicating data between the input controller and the output controller over a power bus of the multi-stage inverter.

Claims

1. A method for controlling a multi-stage inverter for converting direct current (DC) power from a DC source to alternating current (AC) power, the multi-stage inverter including a DC power bus, the method comprising:

controlling operation of an input converter of the multi-stage inverter electrically coupled to the DC power bus with an input controller to (i) convert the DC power from the DC source to a DC power signal supplied to the DC power bus and (ii) modulate the DC power signal to communicate data from the input controller to an output controller over the DC power bus, wherein the output controller is galvanically isolated from the input controller; and

controlling operation of an output converter of the multi-stage inverter electrically coupled to the DC power bus with the output controller;

wherein to modulate the DC power signal comprises to modulate a bus voltage of the DC power bus to communicate the data from the input controller to the output controller.

2. The method of claim 1, further comprising transmitting data from the output controller to a remote device over an AC power line.

3. The method of claim 1, wherein controlling operation of the input converter comprises controlling the input converter to draw a maximum amount of power from a photovoltaic (PV) module.

4. The method of claim 1, wherein controlling operation of the input converter comprises sensing a magnitude of a current output and a voltage output of the DC source.

5. The method of claim 4, wherein controlling the operation of the input converter further comprises generating a current command signal based on the magnitude of the current output and the voltage output of the DC source.

6. The method of claim 4, wherein controlling the operation of the input converter further comprises sensing a magnitude of the bus voltage of the DC power bus.

7. The method of claim 6, wherein controlling the operation of the input converter further comprises generating a plurality of switching signals for an inverter circuit of the input controller based on the magnitude of the current output, the voltage output, and the bus voltage.

8. The method of claim 1, further comprising:

controlling the operation of the input converter with the input controller to convert an input DC waveform to an output DC waveform;

supplying the output DC waveform to the DC power bus; and

controlling the operation of the output converter with the output controller to converter the output DC waveform to an AC waveform.

9. The method of claim 1, further comprising supplying power to the input controller from the DC source.

10. The method of claim 1, wherein controlling the operation of the output converter comprises controlling the operation of the output converter to convert a DC waveform to an AC waveform suitable for delivery to an AC grid, and further comprising supplying power to the output converter from the AC grid.

11. The method of claim 1, wherein controlling the operation of the output converter comprises sensing a magnitude of the bus voltage of the DC power bus and generating a plurality of switching signals for an inverter circuit of the output controller based on the magnitude of the bus voltage and an average power bus voltage value.

12. An inverter for converting direct current (DC) power from a DC source to alternating current (AC) power, the inverter comprising:

an input converter electrically coupled to a power bus and configured to convert an input DC waveform of the DC source to a bus waveform supplied to the power bus based on a first plurality of switching signals;

an output converter electrically coupled to the power bus and configured to convert the bus waveform to an output AC waveform based on a second plurality of switching signals;

an input controller electrically coupled to the input converter, the input controller comprising (i) first sensing circuitry to sense a magnitude of an output voltage of the DC source, a magnitude of an output current of the DC source, and a magnitude of a bus voltage of the power bus and (ii) a first control module configured to generate the first plurality of switching signals based on the magnitude of the output voltage, the output current, and the bus voltage; and

an output controller electrically coupled to the output converter and galvanically isolated from the input controller, the output controller comprising (i) second sensing circuitry to sense a magnitude of the bus voltage of the power bus (ii) a second control module configured to generate the second plurality of switching signals based on the magnitude of the bus voltage and an average power bus voltage value;

wherein the input controller comprises communication circuitry configured to control the input converter to modulate the bus waveform to communicate data between the input controller and the output controller over the power bus.

13. The inverter of claim 12, wherein the input controller further comprises an internal power supply configured to generate power for the input controller based on a power signal received from the DC source.

14. The inverter of claim 12, wherein the output controller further comprises an internal power supply configured to generate power for the output controller based on a power signal received from an AC grid.

15. The inverter of claim 12, wherein the output controller further comprises a power line communication circuit configured to communicate with a remote device over an AC power line.

16. One or more non-transitory, machine-readable storage media comprising a plurality of instructions stored thereon that, in response to execution, cause a multi-stage inverter for converting direct current (DC) power from a DC source to alternating current (AC) power, to:

control operation of an input converter of the multi-stage inverter electrically coupled to a DC power bus of the multi-stage inverter with an input controller to (i) convert the DC power from the DC source to a DC power signal supplied to the DC power bus and (ii) modulate the DC power signal to communicate data from the input controller to an output controller over the DC power bus, wherein the output controller is galvanically isolated from the input controller; and

control operation of an output converter of the multi-stage inverter electrically coupled to the DC power bus with the output controller,

wherein to modulate the DC power signal comprises to modulate a bus voltage of the DC power bus to communicate the data from the input controller to the output controller.

17. The one or more non-transitory, machine readable storage media of claim 16, wherein to control operation of the input converter comprises to control the input converter to draw a maximum amount of power from a photovoltaic (PV) module.

18. The one or more non-transitory, machine readable storage media of claim 16, wherein to control operation of the input converter comprises to sense a magnitude of a current output and a voltage output of the DC source.

19. The one or more non-transitory, machine readable storage media of claim 18, wherein to control the operation of the input converter further comprises to sense a magnitude of the bus voltage of the DC power bus.

20. The one or more non-transitory, machine readable storage media of claim 16, wherein to control the operation of the output converter comprises to sense a magnitude of the bus voltage of the DC power bus and generate a plurality of switching signals for an inverter circuit of the output controller based on the magnitude of the bus voltage and an average power bus voltage value.