UPFC Simulation Analyzation And Its Controller Design

As the most flexible controller of the Flexible AC Transmission System (FACTS), a Unified Power Controller (UPFC) can control concurrently or selectively the transmission voltage, impedance and phase angle, and the real and reactive power flow in the line. This paper introduces the structure, principle, dynamic model, performance and basic operating models of the UPFC.This thesis setes up a Simulink model of UPFC after analyze its principle. And then, this model is applied into a three-phase system to observe its influences to power quality. At first, this paper finds whether UPFC could compensate the system voltage. As s result, it is obvious that UPFC could keep the system voltage in sine wave when in the three-phase fault. On the other hand, it is found that UPFC has no negative influence to voltage of the stable system. Then the ability of UPFC to stabilize active and reactive power after a three-phase fault in transmission line is researched. The characteristics of damp power pulse when a new equipment switch into a stable system is also analyzed.The third, this thesis researches the dynamic interaction among its multiple functional UPFC and two UPFC controllers in the single machine system. It gives the synchronous generator model of the power system which time-domain simulation adopt, and the integration model of a single machine infinite system that equipped with a UPFC. It gives four single-input single-output of UPFC PI controllers to complete the four basic functions. In the process of designing, the interactive impact is found exist between a number of control channels. And there is different interaction between control channels with different operational point of the UPFC. At last analysis, the interaction affect of the two UPFC under different control operation is pointed.At last, in this paper the singular value decomposition (SVD) based controller of UPFC is proposed to reduce or eliminate the dynamic interaction between the active and reactive power flow. The performance of the proposed SVD controller is evaluated in both ideal and practical systems. The results obtained are then compared with those found for the static decoupled (SD) and PI controllers. It is observed that the proposed SVD controller can significantly reduce the dynamic interaction between the active and reactive power flow through the line and it is achieved by decoupling the interaction between the direct and quadrature axes control variables.