Research On Interacion Effect And Coordination Control Of Multiple FACTS Damping Controllers In Power System

Flexible AC Transmission System (FACTS) plays an important role in enhancing security and stability of power system as well as improving operational efficiency of the grid. With the wide applications of FACTS technology and devices in power systems, the interaction analysis and coordinated control among multiple FACTS controllers in power system become one of the hot topics. More and more studies show that individually designed and well-run FACTS controllers cannot guarantee the performance conditions while commissioning the controller. Certain interactions exist between FACTS devices, which will worsen the control effect of FACTS seriously and even threaten the safe operation of the system. The Interaction and coordination of multiple FACTS controllers became the key technical issues of the actual grid. Study on the possibility and mechanism of interaction as well as the coordinated control problem among multiple FACTS devices, and study on the coordinated control strategy for improving power system stability has important theoretical and practical significance. Thorough studies and useful discussions on interaction mechanism, interaction analysis method and coordinated control method of multi-FACTSs for large power system have been made in this dissertation. Main contributions and innovations are described as following:1) The interaction mechanism among multiple FACTS damping controllers in power system was studied, and a novel multi-FACTS interaction mechanism analysis method on the base of Selective Modal Analysis (SMA) and multivariable frequency domain control theory was presented. First of all, the multi-FACTS interaction characteristic was extracted with the help of SMA. Then the interaction relations among the multi-FACTS and occurred conditions were derived using multivariable frequency domain control theory. Furthermore, the mechanism of interaction was theoretically proved on the base of the above research. The results show that there is certain conditional relationship between multiple FACTS damping controllers in the same power system. When the parameters satisfy a certain condition, the negative interaction of multiple FACTS occur, which even threaten the safe operation of the system. In order to ensure the coordinated operation of multiple FACTS controllers, the controller parameters should satisfy the coordinated operation conditions. The simulation results validated the conclusion.2) The interaction among multiple FACTS damping controllers in power system was studied, and a novel multi-FACTS interaction analysis method on the base of Effective Open-loop Process (EOP) theorem was presented. First of all, the EOP under the framework of power system damping control was deduced, and the Damping Control Effective Open-loop Process (DCEOP) for multiple FACTS interaction analysis was established. Then a new interaction analysis method based on DCEOP spectral radius and multivariable promotion Nyquist theorem was proposed, which can determine whether the system contains negative interactions among FACTS damping controllers. Furthermore, two novel interaction quantitative indexes based on DCEOP were derived and proposed, which offer quantitative interaction analysis for multiple FACTS controllers. Finally, the simulation results for typical system as well as a practical power grid verified the validity and efficiency of the method proposed in this dissertation.3) The coordinated control method among multiple FACTS damping controllers in power system was studied, and a novel coordinated control design technique based on Mesh Adaptive Direct Search (MADS) algorithm was proposed, which could ensure the coordinative operation of multiple FACTS damping controllers in the same power grid. This method used the frequency domain design idea to ensure the robustness of the multiple controllers under different operation schemes, and ensured the coordination of multi-controller running ability on the base of MADS algorithm, thus ultimately achieved coordinated operation and control of multiple FACTS damping controllers. The simulation results validated the conclusion.4) The coordinated control method among multiple FACTS damping controllers in power system was studied, and a novel coordinated control technique based on Wide-area Collaborative Expert Control System Theory was proposed. First of all, the grid operation status and interaction level of multiple FACTS controllers was monitored in real time based on the advanced experience of control experts, and efficient extraction of the feature quantity of multiple FACTS coordinated control was achieved. Then, the real-time coordination control decisions were automatic generated through regional expert subsystems which ensured the coordinated control of multi-FACTSs within the regional grid. Finally, the regional expert subsystems were supervised and coordinated by the collaborative-main system and the coordinated control of multi-FACTSs of the whole grid was realized in real time. This method provided a new solution to solve the multi-FACTSs coordinated control problem in complex power systems. The simulation results and test results validated the conclusion.