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1. WO2010080431 - POWER INVERTER CONTROL FOR GRID-TIE TRANSITION

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Claims

1. A control system for a power inverter (140), wherein the power inverter is coupled to a contactor (180) configured to connect and disconnect a grid (190), the control system comprising: a plurality of output voltage sensors (172-175) and a plurality of output current sensors (182-185), wherein the output voltage sensors are configured to measure at least two line voltages at the contactor and the output current sensors are configured to measure at least two line currents at the contactor, once the grid is connected; a controller (200) connected to the output voltage sensors and output current sensors, the controller being configured to: determine a target amplitude and a target frequency for an output voltage of the power inverter; and determine a plurality of power transistor switching pulses based on the target amplitude and the target frequency; and an interface circuit (210) connected to the controller and the power inverter, the interface circuit being configured to provide the power transistor switching pulses to the power inverter.

2. The control system of claim 1 , wherein the controller is further configured to synchronize the power inverter with the grid after an instruction to connect the grid is received and before the grid is connected.

3. The control system of claim 1 , wherein the power inverter is further connected to at least one power source (110 or 120), wherein the power source supplies DC power to the power inverter.

4. The control system of claim 3, wherein the control system further includes: an input voltage sensor (171) configured to measure a DC voltage supplied by the power source and an input current sensor (181) configured to measure a DC current supplied by the power source, wherein the controller is further configured to determine a reference active power based on the DC voltage and the DC current.

5. The control system of claim 4, wherein the controller being configured to determine the target frequency includes the controller being configured to: calculate an active power based on the line voltages and the line currents; and match the active power with the reference active power using a feedback control loop .

6. The control system of claim 1 , wherein the controller being configured to determine the target amplitude includes the controller being configured to: determine a reference reactive power using power factor correction; calculate a reactive power based on line voltages and the line currents; and match the reactive power with the reference reactive power using a feedback control loop.

7. A control method for a power inverter (140), wherein the power inverter is coupled to a contactor (180) configured to connect and disconnect a grid (190), the control method comprising: measuring at least two line voltages and at least two line currents at the contactor, once the grid is connected; determining a target amplitude and a target frequency for an output voltage of the power inverter; determining a plurality of power transistor switching pulses based on the target amplitude and the target frequency; and providing the power transistor switching pulses to the power inverter.

8. The control method of claim 7, wherein the control method further includes: measuring a DC voltage and a DC current supplied by a power source to the power inverter; and determining a reference active power based on the DC voltage and the DC current.

9. The control method of claim 8, wherein determining the target frequency includes: calculating an active power based on the line voltages and the line currents; and matching the active power with the reference active power using a feedback control loop, wherein the feedback control loop includes an integration loop and a power droop loop, wherein the power droop loop includes a low pass filter (412).

10. The control method of claim 7, wherein determining the target amplitude includes: calculating a reactive power based on line voltages and the line currents; and matching the reactive power with the reference reactive power using a feedback control loop, wherein the feedback control loop includes an integration loop and a power droop loop, wherein the power droop loop includes a low pass filter (406).