Control Strategy Research Of UPFC And Influence Caused By UPFC Installed In Power System

The development and application of FACTS would be enable to promote the power system technology innovating, and improve the economic performance and security stability performance of power system. UPFC is the strongest one of FACTS controllers so far. It obviously improves the static dynamic performance of power system. The research and application situation of FACTS and UPFC are introduced.The methods of power flow analysis of power system with Unified Power Flow Controller (UPFC) are introduced. On the basis of that, the way that power flow analysis connects with Steady-state model of UPFC is adopted to analyze the change of system electrical values with different control objectives, When power system is Steady-state model a control strategy which chooses the middle control instead of direct control method in series control system is analyzed and ooptimized. Simulation results proved the control strategy is reasonable.The design of UPFC controller divides into two parts. First, on the basis of mathematical model of UPFC shunt inverter, a double close loop control system of UPFC shunt inverter is designed, Circuit decoupling control realizes decoupling effect of dq axis circuit on inside loop. D axis circuit control dc-link capacitor voltage and q axis circuit control shunt node voltage on outside loop, as the same time,the precious level and responding velocity of control system is improved by admitting circuit feedforward section and circuit feedback section. High voltage levelc is adopted in simulation system. The way of Standard value is adopted to analyze and computer all kinds of control parameter; The second, the power flow transmission capacity is analyzed in a general UPFC system. The P-Q two dimension plane figure which makes the enable control region of power flow clearly is drawn. The UPFC controller is designed based on the three loop control model, it modifies the control parameters of circuit link, voltage link and power link. Especially,a way with the theory of small signal and frequency analysis are adopted to analyze the control strategy of power link. Finally, the simulation experiment of series control system is operated in accord with shunt control system which have been designed. The result of simulation proved the effectiveness and rationality of designed UPFC controller. Besides, the simulation experiment of two different power flow control strategy—power coupling and power decoupling are operated, comparing each other's good and bad in terms of stability and response velocity performance.It is a important point to analyze the influence of power system which obtains UPFC. According the control system which designed in the paper, a new 11-deminsion dynastic model of UPFC is proposed. The model combines the generation model and excitation model to construct a integral linearization model of power system with UPFC. Eigen-value analysis method is adopted to prove the Multi-Generation system with UPFC is small signal stability.