Adaptive backstepping control based emegency scheme for improving transient stability of power systems with renewable energy sources

Abstract

Due to the high demand for electrical energy, operation of modern power systems under stressed loading conditions have become more common. Renewable energy sources are incorporated into modern power systems (RES) that include solar photovoltaics (PV), wind turbines, etc., and complex loads that can considerably alter the electrical system's dynamics. The power system comprises synchronous generators and other energy sources linked together to generate electrical power. When a severe disturbance on the electrical grid occurs, the supply of electrical power may be endangered, and this must be ensured by selecting the corrective action. Transient instabilities occur after extreme contingencies, which are a significant threat to the dynamic security of systems. In this condition, the generator's rotor speeds and rotor angles change suddenly, which causes quick altering of electrical power, and therefore, maintaining system security in tricky conditions is one of the crucial tasks in electrical engineering. The corrective control is applied after disturbance. Emergency control schemes, such as transient stability excitation control (TSEC), can improve the system's stability. TSEC enhances transient stability by controlling excitation system of generators. This control is one of the conventional excitation control techniques that is compared with other methods in this thesis. Besides the emergency control schemes, Power System Stabilizer (PSS) can be a proper solution to decrease the oscillations in a power system in the transient period. A multi-machine power system consists of generators, turbines, transformers, transmission lines, and loads. To design the dynamics of a power system, the set of differential-algebraic equations (DAEs) should be solved with numerical methods. Differential equations include synchronous generator and turbine inter-area equations, and algebraic equations include stator algebraic equations and network equations. In this study, a tandem-compound single-reheat steam turbine controlled by a speed governor is considered, and it produces the related mechanical power for inputting to synchronous generators. Synchronous generators can be designed with different degrees of accuracy to make the related electrical power. In this study, the 3th order (flux-decay) model synchronous generator with the first-order excitation system (static exciter) is regarded. The network side consists of transmission lines, loads, and other components. This study replaces RES with the related synchronous generator with equal injected real and reactive power. In this thesis, Adaptive backstepping control (ABC) is proposed to improve the transient stability of power systems during emergency conditions. The thesis problem and the modeling studies are aligned with the studies of collaboration in the TUBITAK project no. 118E184 and in our published paper, whereas the development of ABC-based controller is the main contribution of this thesis.