Study On Passivity-Based Control Methods For Power System With FACTS

With the rapid development of modern power system that is characterized by expanding scale, increasing interconnected network, and diversity of operating conditions, the system is made more complicated to operate and control. Flexible AC Transmission System (FACTS) provides an effective means which can significantly improve the capacity of power transmission, enhance system stability, and makes the system operate in a more flexible way. But with the quantity of FACTS devices installed in power system increasing, operation of the system is put forward new demands. Research of control strategies for FACTS, coordinated control between FACTS and other devices in system, and coordinated control between multiple FACTS devices in order to improve the operating stable level of power system, has great value in engineering application.Power system models represented by a set of nonlinear differential algebraic equations (NDAEs) can combine a variety of electrical installations, and facilitate the research of coordinated control between these devices. Therefore, research of control strategies for stabilizing of NDAEs has theoretical and practical value. Passivity-based control (PBC) methods, as represented by Hamiltonian system theory of NDAEs, are increasingly concerned by researchers. It is still an important research subject that combining passivity-based control methods with other control strategies, making it more then applying them in power system. This paper around the issues above, the main results achieved are as follows:1,Based on the summary of Hamiltonian system of ordinary differential equations (ODEs), a novel and more generalized Hamiltonian system for NDAEs is presented while taking into account the characteristics of power system model described by NDAEs. The conditions of Hamiltonian realization, construction of the Hamiltonian function, and design strategies of stability controllers are given. Considering the interference and uncertainties in the system, the H∞control problem is studied, and the corresponding stabilizing controller with which the system can remain asymptotically stable and robust is designed. Combined with energy-shaping and adaptive control methods, the conditions of adaptive H∞control for the proposed NDAEs Hamiltonian system are analyzed. And the design method of the corresponding feedback controller that can guarantee asymptotic stability of the closed-loop system and improve system dynamic performance is given.2,For structure preserving multi-machine power system represented in NDAEs, the Hamiltonian realization and control strategies based on energy shaping for the system with nonlinear loads are studied. The nonlinear control problem and L2-gain disturbance attenuation problem of the system with shunt FACTS are studied respectively. And coordinated controllers for excitation and STATCOM, coordinated L2-gain disturbance attenuation controllers for excitation and STATCOM are proposed respectively. Simulation results show the correctness of the proposed methods and the effectiveness of the designed control law.3,The problem of coordinated multi-objective control for multi-shunt FACTS is studied. Based on the Hamiltonian realization for multi-machine power system with SVC and STATCOM, coordinated controllers are designed for these FACTS devices via the approach of energy shaping. Compared to the independent control methods for FACTS, simulation results show that the proposed controllers can provide stronger voltage support, and improve the transient stability of the system in case of different fault conditions. Considering the uncertainties of internal parameters and external disturbances, adaptive robust controllers are designed to meet the uncertain parameters and dynamic process for STATCOM and SVC via the method of L2-gain disturbance attenuation combined with adaptive control. Simulation results show that the voltage stability can achieve better robustness with adaptive law.4,Based on the power injection model of TCSC, a novel mathematical model of TCSC that can make it convenient to design controllers by Hamiltonian theory is proposed. Then the synthesized model of Hamiltonian system for multi-machine power system with multiple different types of FACTS——TCSC and SVC is derived, and the coordinated controllers of TCSC and SVC are designed via singular perturbation theory combined with generalized Hamiltonian system theory. Simulation results show that the coordination of TCSC and SVC can achieve better voltage support, power control, and transient stability, and reaches the purpose of multi-objective control.