A study of impact on power system stability originated from new islanding detection method in PV systems

In Japan, a unique islanding detection method, named New Islanding Detection Method, is widely equipped with grid-tied photovoltaic generation systems (PVs) to accurately detect their islanding operation. However, some research results show that the extensive installation of new islanding detection method brings negative impacts on stability of main power grids. This is because the islanding detection method has a possibility to detect frequency fluctuation caused by main grid’s faults, and the resulting undesirable operation intensifies the frequency fluctuations more. The authors especially focus on a frequency feedback mechanism in the islanding detection method, and then clarify some impacts on the stability of main grids which are originated from the growth in penetration of the islanding detection method in PVs. Through numerical simulations and discussions on their results, the authors concluded as, (1) the transient stability can be improved when active power output of PVs are set to constant current characteristics, and (2) the dynamic stability can be improved by maintaining constant impedance characteristics in the active power output of PVs when the PVs keep fluctuating the frequency and the voltage in the main power grids.