Dynamic Performance Evaluation of Decentralized Load Frequency Controllers for Interconnected Thermal Power System with Parallel AC-DC Tie-lines: A Comparative Study

Abstract

The main objective of Load Frequency Control (LFC) is to balance the total system generation against system load losses so that the desired frequency and power interchange with neighboring systems are maintained. Any mismatch between generation and demand causes the system frequency to deviate from its nominal value. Thus high frequency deviation may lead to system collapse. This necessitates a very fast and accurate controller to maintain the nominal system frequency. This study presents an analysis on dynamic performance of two-area thermal power system interconnected via parallel AC-DC tie-lines when subjected to load disturbances. The dc link is used as system interconnection in parallel with ac tie-line. The dc link is considered to be operating in constant current control mode and the power flow deviation through dc link is modeled based on frequency deviation at rectifier end. This study also deals with the application of various controllers namely Proportional plus Integral (PI) Controller, Dual Mode Controller, Fuzzy Logic Controller and Particle Swarm Optimization (PSO) tuned PI Controller for load frequency control of an interconnected power system with AC-DC tie-lines. The above controllers are simulated using MATLAB and their performance is analyzed. Outcome of the analysis shows the superiority of PSO tuned PI Controller over the other control methods.