An Improved Under Frequency Load Shedding Scheme Based on Rate of Change of Frequency

In allusion to the traditional UFLS scheme´s deficiencies of changeless frequency setting value and amount of load shedding of every run, this paper proposes improved UFLS scheme which can alter the frequency setting value of the first run and the amount of load shedding of every run dynamically according to the magnitude of frequency change rate, namely the insufficient amount of active power. The simulation results of stand-alone model show that the reformative UFLS scheme can restrain the frequency falling depth effectively, fit speed controller preferably, make full use of system rotating spare capacity, and reduce the amount of load shedding and the possibility of over-cut or owes-cut.