State Space Based Load Frequency Control of Multi-Area Power System

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The main aim of this thesis is to present a state space based load frequency control (LFC) system in conventional and restructured power system environment emphasizing on multisource power generation (MSPG). An output feedback controller (OFC) is presented with a pragmatic point of view. As full state feedback controllers (FSFCs) require the transfer of information from all parts of the system to a central control facility for processing, which for large scale interconnected power system could prove to be prohibitive, more practical and alternative forms of feedback controllers such as OFCs have been the subject of extensive investigation in the various control engineering applications. As these controllers use only a subset of the state vector for feedback purposes, they are simpler, more practical and easy to implement than the FSFCs. A simple algorithm is presented to optimize the OFC gains. All the power system models presented for LFC study have been simulated using MATLAB Simulation tool and dynamic responses, thereof, are obtained at optimum controller gain settings. The dynamic responses obtained with OFC have been compared with that of FSFC and in most of the cases improved results are obtained. Most of the researchers worked on LFC of power systems considering thermal unit with non-reheat turbines. In this thesis, the LFC is extended for the conventional power systems with the combinations of non-reheat turbines, reheat turbines and hydro turbine. The control area having MSPG represented by an equivalent of thermal or hydro unit dynamics only may not result in a realistic design of LFC control. Therefore, new power system models with MSPG are presented in this thesis for LFC study in both conventional and restructured power system environment. The LFC system is further improved by considering AC-DC tie lines and thyristor controlled phase shifter (TCPS). Modified LFC of an interconnected power system with MSPG is proposed in restructured power system environment considering all the possible contracts between generation companies (GENECOs) and distribution companies(DISCOs). The LFC of hydro power plants operational in KHOZESTAN, IRAN has also been studied. The proposed controller performs well on this hydro plant and improves the frequency deviation responses remarkably. The proposed controller shows its capability and flexibility by providing the desirable dynamic responses to all the power system models studied. To examine the robust performance of the OFC, the system parameters and operating load conditions are varied by औ25% from their nominal values to obtain the dynamic responses. The effects of generation rate constraint (GRC) and variation in step load perturbations (SLPs) are also examined. Dynamic responses are obtained by varying the regulation parameter and the most appropriate value is suggested for the power systems with MSPG. Many research work on LFC systems have been reported in recent years. Still there is much room for further improvement and extensions of such schemes in new power system environment. In this thesis, LFC systems of several new models have been presented and improved dynamic responses are obtained.
Supervisor: Somanath Majhi