Active disturbance rejection control for load frequency control of Bangladesh power system

Abstract

Energy shortage is considered as the most critical infrastructure constraint to the economic growth of Bangladesh. One of the main causes of the supply shortage, among others, is the poor operational efficiency of power plants. For the operation of a large power system maintaining the proper power quality has always been a difficult task. Increasing number of major power grid blackouts that have been experienced around the world including Bangladesh (2007, November and December) in recent years show that today’s power system operation requires more careful consideration of all forms of system instability and control problems and introduction of more effective and robust control strategies. In this thesis an Active disturbance rejection control (ADRC) based decentralized Load Frequency Control (LFC) system for Bangladesh Power System (BPS) is developed and a proposal has been made for feedback connections from various load rich areas to generation rich areas to minimize the area control error. The frequency control system maintains frequency and tieline power flows to specified values in the presence of physical constraints and model uncertainties. As power load demand varies randomly in an interconnected power system, both area frequency and tie-line power interchange also vary. The objectives of LFC are to minimize the transient deviations in these variables (area frequency and tie-line power interchange) and to ensure their steady state errors to be zeros. Unexpected external disturbances, parameter uncertainties and model uncertainties are big challenges for LFC design. As an increasingly popular practical control technique, ADRC has the advantages of requiring little information from the plant model and being robust against disturbances and uncertainties. A solution to the LFC problem based on ADRC is an alternative one. Performance analysis of ADRC is done by comparing with Proportional Integral Derivative (PID) controller and for two area non-reheat and reheat turbine unit. ADRC is also implemented on a large power station. Finally, the design of BPS is done considering its radial connection and proposal is made about feedback connection based on the performance of ADRC. The dynamic model of the power system and the controller design based on the model are elaborated. Simulation results show that ADRC controller is attractive for the LFC problem in terms of its stability and robustness.