Methods for anti-islanding in distributed-source electrical power generation and distribution systems and electrical systems and apparatus using same

Abstract

A method of detecting an interruption of grid electrical power at an output of an inverter power train coupled to an electrical grid includes generating a reference waveform representing a power train output current waveform with a current control loop. An out-of-phase control signal is generated, which is synchronized and out-of-phase with a grid voltage waveform, with a voltage control loop coupled to the output of the inverter power train, the voltage control loop having a gain proportional to an inverter power train load impedance. The reference waveform and the out-of-phase control signal are combined to generate a power train control signal for producing a small phase difference between the inverter power train output current waveform and the grid voltage waveform. The inverter power train output is monitored for a change and the inverter power train is turned off in response to a change in the inverter power train output caused by an increase in inverter power train load impedance resulting from an interruption in the grid electrical power.