The Interaction Analysis And Coordination Control Of Multiple SSSC Components

Since entering the 21 st century,power grid structure and operation mode are increasingly complex with the rapid development of China’s power grid and smart grid construction.It requires the power grid can flexibly control the power flow distribution by certain means and can improve the stability of the system.Therefore,the FACTS technology will be widely used in the power grid.Static synchronous series compensator(SSSC)as a representative of the second generation series of FACTS element and the main part of the third generation of FACTS element-UPFC will pour into power grid operation.Due to the component of the controller design and coordination problems,it may produce the adverse effects on the system and affect the operation of power system stability and security when multiple SSSC components put into operation in power grid at the same time.Because of these problems,the analysis of interactions between multiple SSSC components and coordinated control are studied in this article,the main content of the study are as follows:(1)This paper refers to the basic theory of flexible ac transmission system and the current research status of SSSC components.It summarizes the interaction of flexible ac transmission system(FACTS)elements and the main analysis method.And it analyzes the methods of the coordination control in a variety of FACTS at home and abroad put forward in recent years.Then,it introduces the wide-area measurement system(WAMS)technology and modular multilevel converter(MMC)and other emerging technologies in the application of FACTS.(2)This paper establishes the extended Phillips-Heffron model of multimachine power system furnishing two static synchronous series compensators.In this paper,an interaction comprehensive analysis method based on RGA and of NI standard is put forward.Using RGA method to provide specific information and NI standards provided by the system as whole information quantitatively analyzes the two SSSC electric distance and different parameters are set at different cases,the strength of the interaction degree.And using PSCAD sets up simulation system to simulate interaction between SSSC elements under different conditions.(3)This paper puts forward a multiple control variable matching method based on the existing NI index theory which is suitable for large-scale,multivariate.Using this method finds the optimal pairing combination to make the interaction between controller control variables minimal.Through the analysis of the optimal pairing combination,it can get one group of input—output variables to make the relationship with the severity of interaction the largest in the optimal pairing combination.On the basis of this relationship,it can work out the corresponding coordinate control strategy of multiple FACTS components.Through the calculation and analysis of the simulation system,it proved that the proposed control variable pairing method is feasible.And through the corresponding simulation by using PSCAD to build a simulation system which contains SSSC components,it proved that the strategy of coordination commissioning is feasible and practical.(4)This paper builds a model of a new series FACTS device based on Modular Multilevel Converter(MMC),which is hereafter called MMC-SSSC.On the basis of detailed analysis on the structural characteristics and control principle of MMC-SSSC device,this paper puts forward two control schemes in the context of normal operation and line fault.Then,the paper uses the state feedback linearization and integral sliding mode variable structure control method to optimize a power controller of MMC-SSSC.It makes the active and reactive power of transmission line decouple and eliminates the nonlinear characteristics.It also improves the robustness of control system.At the same time,the auxiliary dc capacitance voltage controller is designed to stabilise capacitor voltage.Finally,the proposed control scheme and design of controller optimization results are verified by the time domain simulation.(5)This paper proposes a wide area coordinated control strategy for multiple SSSC components.It divides the control of whole system into two layers,including "autonomy" control and "separation of powers" control.Two layers are provided real-time system state data by WAMS.And it uses the "decomposition-coordination" algorithm to realize the full system optimization control of multiple SSSC controllers.Using PSCAD builds a two area four machine simulation system.And the control effect of the proposed control strategy has carried on the simulation.