| Flexible AC Transmission System or FACTS is an important aspect of the power electronic technology application in power ac transmission system. It can make the present power grid resource into great use and can realize the best utility of power energy. Therefore this new technology may cause the great reform on power transmission and distribution system in the future. Unified Power Flow Controller, a typical and the most flexible controller of FACTS, can control concurrently or selectively the transmission line voltage, impedance and angle or alternatively, the real and reactive power flow in the line.The steady and dynamic mathematic models of UPFC are investigated, and the basic control performances and the control system structure are also discussed in this paper. Then the UPFC power flow control characteristics and the fundamental principles of UPFC control arc put forward.Current Control of the PWM (CC-PWM) converter, one of the devices in UPFC, is studied and the control scheme of PWM rectifier is discussed in this paper. Based on the traditional control on PWM rectifier, space vector PWM predictive current controller is presented using the switching function model. For the system as complex and changeable as PWM, a self-adaptive intelligent fuzzy PID controller is used, which is verified that it decreases the response time of the system sharply and does a great help to better the control performance and robust of PWM rectifier.Furthermore, the neutral network intelligent power flow controllers are proposed on the basis of traditional PID control for the study of UPFC power flow control. The artificial neutral network power flow controller and the fuzzy neutral network power flow controller with the combination of fuzzy logic and neutral network system are designed in this paper. And the simulation results show that these two intelligent controllers are better than the PID controller by comparing the response time and the steady and dynamic performances. |
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