Research On Voltage Stability Of Power Systems Based On Adaptive Control And Numerical Continuation Algorithms

Development of modern power systems towards large scale power system, high voltage, and long-distance transmission plays an important role in economical use of energy, but also challenges the power system security. With several widespread system blackouts resulting from voltage collapse throughout the world in recent years, the problem of voltage stability has attracted persistent interests of researchers.In this dissertation we focus on two aspects: First, reseach on bifurcations of power system differential-algebraic: numerical continuation algorithms. Second, A Model Reference Adaptive Control is presented for power systems differential-algebraic equations, to improve the dynamic stability as well as increase the system's load ability. The organization of the thesis is as follows.Based on the bifurcation theory, the three types of bifurcations encountered in the power system dynamic: Saddle-Node Bifurcation, Singularity-Induced Bifurcation and Hopf Bifurcation is introduced by some examples. The continuation method to calculate the solution branches is illustrated and the basic procedures of calculating bifurcations of dynamic system are given. Some software for the study of dynamical systems is introduced to contrast their capabilities.AUTO2000 is recommended for an example of general bifurcation software. Its function, manual, instruction and localization is presented in detail by a classic example. Some advices and tips are given for using AUTO2000 better.The power system dynamics model with algebraic constraints in the form of power flow equations is studied here as differential-algebraic system. Linearization is used to get a linear original differential equations model and then the dynamic analysis is presented through its eigenvalue analysis by IEEE-I Two bus power system as an example. The bifurcations are discussed due to system parameters changing. Finally, according to the above analysis, we introduce our motivation to adaptive control to improving the system's dynamic and stabilizing the existing equilibrium without changing the original equilibrium value.Model Reference Adaptive Control schemes are reviewed for a linear system with uncertainly system parameters. Associated mathematical proofs of Lyapunouv stability are also provided. A dynamic equilibrium tracking mechanism is presented to obtain the equilibrium value for uncertain or changing operating condition and apply the technique of MRAC for power systems to stabilize the equilibrium. IEEE-I Two bus power system are given as an example to demonstrate our approaches. It is proved that the system can improve the dynamic stability as well as increase the system's load ability.