Using a Two-Stage Lead-Lag PSS in an Accurate Combined Model of LFC-AVR to Simultaneously Control Frequency and Voltage in an Interconnected Multi-Area Power System

Frequency and terminal voltage deviations are two significant challenges in interconnected power systems. Variations in load or any disturbances affect the amounts of active and reactive power and it has an adverse effect on the normal operation of the power system. To avoid these adverse effects, it is essential to maintain frequency and terminal voltage at their nominal values. A suitable solution is the implementation of a combined LFC-AVR model. However, obtaining real and reliable results necessitates an accurate combined dynamic model of LFC-AVR. So, this paper proposes an accurate model for a two-area multi-unit power system that includes AVR and LFC loops. Furthermore, to control frequency and voltage simultaneously, a PID controller is employed in the LFC loop, while another PID controller is used in the AVR loop. Additionally, a two-stage lead-lag PSS is incorporated into the excitation control loop to enhance the performance of LFC and AVR. Notably, the impact of AVR on the LFC loop is taken into account. It is assumed that both areas of the power system are identical, with each area comprising gas, reheat thermal and hydro units, considering the physical limitations of GDB and GRC. The ITSE is chosen as the objective function. The TLBO algorithm is utilized to identify optimal values for controllers in the LFC loop, AVR loop, and PSS under a ۰.۰۱ p.u. SLP. To check the reliability and efficiency of the proposed model, a sensitivity analysis (±۵۰% change in loading) has been conducted. The proposed method is compared with the DE algorithm and the RCGA. The simulation results indicate that employing the proposed hybrid model enhances the damping performance of the LFC and AVR systems, thanks to the substantial role of the PSS in mitigating LFOs and improving the stability of the power system.

کلیدواژه ها:

Low frequency oscillation ، Load frequency control ، automatic voltage regulator ، teaching learning-based optimization