Research On Improving Transent Stability Basrd On Optimal Variable Aim Control Considering Excitation And FACTS Effect

At present,with the interconnection of regional power grids,the scale of power system is gradually increasing.The operating environment of power systems in long-distance transmission lines is very severe,and the stability problem of the power grids becomes more prominent.A large number of studies show that the control of generator potential through the excitation system can improve the transient stability of the system.The addition of flexible AC transmission system(FACTS)in the system can improve the transmission capacity and improve the transient stability of the system.Therefore,in order to improve the stability problem of large-capacity and long-distance transmission lines,this paper considers the effects of excitation and FACTS simultaneously in the system,and adopts the optimal variable target control that directly uses the nonlinear system model without linearizing the system.Design control laws to improve the transient stability of the system.On the basis of expounding the structure and classification of excitation system,this paper analyzes the influence mechanism of the generator excitation system on the transient stability of the system,expounds the structure and working principle of the power system stabilizer(PSS).and takes an example to analyze the effect of additional excitation device on improving the transient stability of single machine infinite bus system.In power system with high transmission level,when faults occurs,the stability of the system can not meet the required requirements only through excitation device.In order to improve the transient stability of large-capacity systems,the controllable interphase power controlloer(TCIPC)device in FACTS isintroduced into the system.Based on the analysis of the basic structure of the Interphase Power Controller(IPC),this paper deduces the relationship between the transmission power of the tie line with TCIPC and the control parameters of the interphase power controller.It shows that the transmission power capability of the line can be improved and the transisent stability of the system can be improved by controlling the equivalent inductance and capacitance of the interphase power controller.Taking the single-machine infinite bus system with TCIPC controller,the fifth-order model for transient stability research of single-machine long-distance transmission system considering excitation and the effect of TCIPC parameters on transimmion power is derived.The fifth-order model designs the control strategy of excitation and TCIPC power control.Taking the TCIPC single-machine infinity system as an example,the system of excitation and TCIPC controllers is compared with the conventional control and the optimal variable target control curve.The simulation results verify that the optimal variable target control strategy can effectively improve the transient stability of the system..Through the series compensation device TCIPC in FACTS to improve the transmission capacity of the line,the transient stability of the system can be improved,and the transient stability of the system has a certain relationship with the bus voltage.Static Var Compensator(SVC)in FACTS It can improve the bus voltage and have certain influence on transient stability.Based on the above research on the transient stability of the single-machine infinite system with TCIPC controller,the SVC is connected in parallel to the single-machine infinite system bus,and the SVC effect is considered.The sixth-order transient stability research model adopts the optimal variable target control design control strategy and simulates the simulation results.The results show that the interaction of excitation,TCIPC and SVC can improve the transient stability of the system better than their respective effects.