Islanding detection method for grid-connected PV inverter under parallel operation

摘要

The present invention relates to a method for detecting a stand-alone operation of a grid-connected photovoltaic parallel inverter. More specifically, the method prevents application of external disturbances in a parallel operation of the inverter to prevent a negative effect on the power quality of the inverter while enhancing the stand-alone operation detection performance. Accordingly, the method includes the steps of: detecting an angular frequency () of each output voltage from a phase locked loop (PLL) unit while executing a D-Q conversion operation on outputs of the inverter connected to a solar power generation system; measuring a frequency error () in a specific frequency band after removing a noise component in each frequency in a band pass filter (BPF) unit; and increasing the frequency error () to reflect an invalid current increase amount (gain(Kpf)) on an invalid current command value (id-ref) to increase an invalid current when the frequency error () exceeds a preset zero-band range.