Decentralized power system emergency control in the presence of high wind power penetration

The frequency thresholds in the classical Under Frequency Load Shedding (UFLS) are constant and prespecified independent of event scale and place. Furthermore, almost all of recent LS schemes are based on System Frequency Response method to estimate the active power deficit using initial frequency gradient following the event; a method that may no longer be valid in the presence of renewable energy sources. The Adaptive Under Frequency and Voltage LS (AUFVLS) scheme which is a decentralized and automatic LS plan and benefits from locally measured frequency and voltage is proposed to tune the frequency thresholds of LS relays online based on voltage deviation from pre-disturbance value. Instead of active power deficit estimation, the load feeders with more voltage decline and hence higher assigned frequency thresholds are shed first i.e. the feeders often located in the neighborhood of event point. The method efficiency is confirmed by numerical simulations conducted in DigSilent PowerFactory software with cascading events and islanding contingencies with different level of wind power share and active power deficit and compared to the classical UFLS method.