Abstract

The frequency stability is a basic principle in the power system operation. Various reasons such as, load shedding, load restoring, and short circuits cause large frequency fluctuations which threaten the system security and could lead to complete blackouts as well as damages to the system equipment. Hence, this paper proposes a coordination of Load Frequency Control (LFC), which uses an optimized PID controller-based Moth Swarm algorithm (MSA) and digital under/over frequency relay for a realistic multi-source power system protection considering different cases study of load shedding and restoring. The discrete-time data of system frequency which obtained from data conversion system is applied for energizing the digital frequency relay under the normal and faulted conditions. The presented digital frequency relay will include both over and under frequency functions. To prove the efficient effect of the proposed coordination, the Egyptian Power System (EPS), which contains three dynamics subsystems, hydro, reheat, and non reheat power plants was investigated for the MATLAB/SIMULINK simulation considering the effect of system nonlinearity. The obtained simulation results stated the effectiveness of the proposed coordination to maintain the power system frequency stability and security. Furthermore, the superiority of the under/over digital frequency relay in terms of accuracy and speed has been approved.