Power Deficit Calculation and under Frequency Load Shedding Strategy Based on the Frequency Deviation Area

Abstract

Aiming at the power deficit calculation inaccuracy and the fixed amount of load shed by under frequency load shedding (UFLS), a power deficit calculation algorithm and an UFLS strategy based on frequency deviation area are proposed in this paper. The assumption that the frequency deviation areas of every bus are equal to the system center of inertia (COI) frequency deviation area at the same time is theoretically proved. Then, the relationship between the COI frequency deviation area and the system power deficit is derived. The UFLS can calculate the system power deficit only using the local frequency deviation area measured. The startup mechanism of the UFLS power deficit calculation program is designed and different UFLS schemes are proposed. Finally, the power deficit calculation algorithm and UFLS strategy are tested in the IEEE 39 and IEEE 145 bus system. The case studies show that the algorithm in this paper can calculate the power deficit accurately and the UFLS strategy can raise the minimum frequency of the system and accelerate the frequency recovery.