Research On The Control Strategy For Improving Power Transmission Capability By Thyristor Controlled Series Compensation

With the continuous development of the national economy, domestic need on power energy increases rapidly, so does the transmission of electric energy. Many domestic power transmission systems are Long distance transmission and high power transmission. Under this condition, the research on improving transmission capacity is very significant for domestic power system development.Currently, Thyristor Controlled Series Compensation(TCSC for short) is the most mature technique on research for Flexible AC Transmission System(FACTS for short). TCSC can adjust its capacitive reactance continuously to compensate the system equivalent impedance of the power transmission system, which is beneficial to improve system stability and transmission capacity. In this article, the effect of TCSC on improving power system transmission capacity is discussed.The concept and affect factor of improving power system transmission capacity are introduced in this paper first, as while as the applications of TCSC in power system.?Secondly, the structure, operation principle and working characteristics of TCSC are discussed. Then based on the analysis of power system stability, the action mechanism of TCSC on improving power system transmission capacity is explained.Considering its significant effects on operation, the control strategy of TCSC is discussed in detail in this paper. The control system is divided into two sections: stability control and impedance control.In Chapter 4 of this paper, the PID impedance controller of TCSC is designed and simulated. As the simulation indicated, compared to the open loop control, the PID control performs well with a constant reference impedance. While the PID controller can not adapt to different reference impedance. In view of that disadvantage, improved PID controller based on immune control is designed, which improves the power system operation performance and advance the transmission capacity better in simulation.Stability control strategy of TCSC is discussed emphatically in Chapter 5. The system nonlinear state equation is linearized by the method of exact linearization via state feedback, furthermore linear optimal controller of TCSC is designed. This controller can realize higher power transmission capacity when keeping system power angle stable. The optimal controller based on exact linearization via state feedback performs very well in improving the system stability and transmission capacity, which is verified in simulation.