Control Of Wide-Area Power Systems With Limited Communication

The interconnection of area grids is the development trend of power systems, which helps optimize the allocation of resources and enhance the power supply reliability, but also makes the power grid much more complex and harder to control. A small malfunction in the interconnected power grid may lead to a large scale of power system accident and immeasurable losses. Therefore, it is necessary to improve the safety monitoring level of the power grid. By using the technology of synchronized phasor measurement and GPS, Wide-area Measurement System (WAMS) can monitor the dynamic behavior of whole power systems in real time, which makes up for the deficiency of traditional method, and provides a good condiction for the stability of interconnected power grid. However, the performance of WAMS depends on communication network, information transmission problems such as time delays, packet drops and limited communication may have a negative impact on the control performance of power systems. Thus, there is a significant interest in power systems control with information transmission problems.This thesis focused on both centralized control and distributed control of wide-area power systems with limited communication. The main work is as follows:Firstly, several commonly used models of power systems are analized. For reducing computational complexity, but without loss of generality, the practial third-order model is chosen. Furthermore, an interconnected model of wide-area power systems is derived based on the practial third-order model. Then, by using Direct Feedback Linearization (DFL) method, a distributed model is derived.Secondly, the control problem of the power system is investigated based on wide-area signals with limited communication in a centralized control framework. A communication sequence is introduced to describe the phenomenon of limited communication, and then the power system can be modeled as a switched system. By using Lyapunov stability theory and switched system approach, the sufficient conditions for exponential stability of the power system and design procedures for the stabilizing controller are presented. The effectiveness of the proposed method is illustrated by the simulation of a two-area system.Thirdly, a distributed control problem is studied for wide-area power systems with limited communication between subsystems. By using a cooperative control strategy, an optimal performance index for the distributed power system is proposed. Then, a DMPC algorithm is proposed by using Lyapunov stability theory and LMI technique. The effectiveness of the proposed method is illustrated by a Matlab simulation of the WSCC nine-bus power system.Finally, A summarization of the research results in this thesis is given, and the problems to be solved in the future are prospected.