Study On Interaction And Coordination Of Multiple FACTS Devices

In virtue of the fast and reliable regulation characteristics, flexible AC transmission system (FACTS) technology plays an important role in the optimization of power flow distribution and improvement of the power system stability and transmission capacity. With the increasing interconnection of power network in China, acceleration of smart grid construction and the growing prosperity of the new energy industry, more and more FACTS devices will be applied in power system. That brings enormous economic benefit as well as some new challenges to the power system operation. Especially, the interaction and the coordinated operation of multiple FACTS devices to enhance power system stability, are the main topics which should be focused on.At present, the study on the interaction and coordinated operation of multiple FACTS devices is still in the exploratory stage. There is a lot of research work needed to be carried out, including the impact of FACTS interaction on power system stability and the direction of the development of FACTS coordination, which has great theoretical significance and application value. Focusing on those topics, the contents of this dissertation include the following parts:Aiming at the interaction of FACTS controllers, an index is proposed to measure the interaction degree based on modal series method. The single mode and the nonlinear interaction between modes are both fully taken into account in the algorithm. With this technique, the index reflects the power system nonlinear characteristics, and indicates the interaction of FACTS controllers quantitatively. The simulation results in the study case validate the proposed index, and also show that it can provides guidance for the parameter tuning of FACTS controllers in power system.In order to fully develop the control characteristic of FACTS devices and improve the dynamic stability of power system, the multiple FACTS centralized coordination control architecture based on wide area measurement system (WAMS) is established in the paper. Considering the inherent time delay characteristics of WAMS signals, an anti-delay FACTS-coordinated control algorithm is proposed. The stability criterion for delay system is derived from free-weighting matrix theory. In view of the practical requirement of power system, a minimum damping ratio threshold is set to ensure strong damping mode for system operation. The delay margin of algorithm is also analyzed.To study the adaptability of multi-FACTS coordinated control algorithm when the system operation mode changes, based on the structure of the dynamic output feedback control and the theory of the polytopic linear differential inclusion (PLDI), a wide-area multi-FACTS coordinated control algorithm for multiple load cases is proposed in this paper. In virtue of the output feedback signals from WAMS, in the situation of unknown time delay, the delay margin is analyzed. Moreover, under the circumstance when delay can be estimated, the proposed algorithm is improved by adopting the Pade approximation.Simultaneous coordinated tuning of FACTS controllers is an effective and practical way for FACTS coordinated operation. In this paper, wavelet transform is used to analyze the necessity of coordinated tuning. Based on quantum genetic algorithm (QGA) and extreme learning machine, the multi-FACTS Simultaneous coordinated tuning algorithm is proposed. To improve the efficiency of the optimization algorithm, QGA is developed in four ways, including:multi-target applications, niche initialization, quantum catastrophe and a new adaptive rotation angle strategy. Finally, the tuning algorithm is validated in two study cases.