Modeling And Research Of Three-level Static Synchronous Series Compensator

With the development of economy and the progress of science and technology,the demand for electric power in our country is increasing,and traditional power system has been difficult to adapt to this development requirements.Therefore,the flexible AC transmission(FACTS)technology has been paid more and more attention in recent years.The static synchronous series compensator(SSSC)is a new type of FACTS device with good prospects for development,which can adjust the equivalent impedance of the line,adjust the power flow of the system and increase the transmission capacity of the line.In this paper,the current research status of SSSC device and the technical applications are briefly introduced.The working principle and functions of SSSC are analyzed by simple two-machine system.Several common SSSC topologies are compared,and three level structure is selected as the main circuit structure of SSSC device,and the working principle of three-level structure is analyzed.In this paper,two methods are used to establish the mathematical model of SSSC:(1)Using the output modeling method,the SSSC is equivalent to a synchronous voltage source connected in series.The mathematical model is established by using the output of the AC side and the DC side,and the factors influencing the output of SSSC are analyzed.(2)The topology modeling method is used to establish the model based on the topology of the SSSC main circuit and the relationship between the switching state and the output of the inverter.According to the mathematical model of SSSC,the control strategy is proposed.The three-level SVPWM modulation method is given,and the neutral-point voltage balance problem is analyzed.Based on the research of SSSC mathematical model and control strategy,the simulation software MATLAB is used to build a three-level SSSC model,and the three-level SVPWM control algorithm and the functions of SSSC are simulated.The distribution of power flow before and after equipment switching is analyzed,verified the correctness and rationality of the model.Finally,on the basis of the existing conditions of the laboratory,the hardware and software design of the small experimental system is carried out.The digital signal processor TMS320F2812 is used as the controller,and some modules of the system are verified.