Synchrophasor measurements-based under frequency load shedding using bus voltage index and estimated disturbance magnitude

When a disturbance occurs in a power system which leads to a decline in frequency, the power grid voltage stability is also at risk. In this research, we propose an improved under frequency load shedding technique that incorporates both the estimated disturbance and the voltage index of load buses. Based on the swing equation the disturbance is estimated in real time and the value is used for load shedding. Instead of shedding prefixed load-buses, all load-buses participate in the shedding process. When a disturbance occurs the voltage drop of each bus is expressed as a fraction of the total calculated voltage drops, and this gives the bus voltage index of the load buses. The greater the bus voltage index the more the load that is to be shed from the respective bus. It is also shown that the use of phasor measurements reduces the complexities of using the Jacobian to calculate voltage stability indicators.