Research of an active islanding detection based on slight asymmetry modulation

In the paper an active islanding detection algorithm is proposed based on grid-connected distributed generation system. If the modulation sinusoidal waveform of the DSP controller presents has been a slight asymmetry, the output current of the inverter would reveal the same amount of asymmetry, then the output power will be keep an orderly change between two consecutive half-cycle. When in grid-connected scenario, the change of output power is insignificant; however, once the islanding event takes place, the frequency of PCC(the point of common coupling) will change own to the change of output power, an appropriate use of this change of frequency can be a useful indicator for the identification of islanding. The experimental results demonstrate effectiveness and easily realized of the proposed algorithm on photovoltaic grid-connected generation system.