Power Equations and Non-Detection Zone of Passive Islanding Detection and Protection Method for Grid Connected Photovoltaic Generation System

Islanding detection and protection is an important concern for grid connected photovoltaic (PV) power generation system due to personnel and equipment safety. Over/under voltage protection (OVP/UVP) and over/under frequency protection (OFP/UFP) are basical inverter resident passive islanding detection method (IDM) for detecting an islanding condition by monitor parameters in point of common coupling (PCC) such as voltage amplitude and frequency and then cause the inverter to shut down when there is sufficient transition from normal specified conditions. The real and reactive power equations and Non-Detection Zone (NDZ) of OVP/UVP and OFP/UFP methods for grid connected PV system are derived and analyzed in this paper. Analyses show that the behavior of the system at the time of disconnection will depend on the imbalance power at the instant before the switch opens to form the island, these results also indicate the NDZ of OVP/UVP and OFP/UFP methods is considerable large and the reaction times for these protective methodologies may be variable or unpredictable.