Fuzzy Control And Application On Power Systems Voltage Stability

Voltage stability has become an important issue as the development of modern power industry which makes the power system suffer more and more pressure. Concluding from some accidents in power system recent years, system condition will get worse when extensive voltage instability or collapse happens. In some serious situation, it could lead to large area power failure causing big economic loss and inconvenience in daily life.Voltage instability or collapse is related to many factors. Based on the summarization of many previous works, this dissertation concludes two main reasons: The instability of reactive power is the core issue of voltage collapse. The rotor swing on generator side often causes low-frequency oscillation, which will eventually cause the loss of stability of system if have not enough damping. Based on the above, two strategies are proposed to improve voltage stability. One is adding static VAR compensator (SVC) to improve voltage stability of load-side. The other is inhibiting low-frequency oscillation with power system stabilizer (PSS).Combination of reasons for voltage instability, this article applies fuzzy control theory in power system stability control. Introduce the basic design of fuzzy controller, then propose SVC fuzzy controlling and fuzzy-type power system stabilizer (FPSS).(1) This article has set up a simple model of single-machine infinite bus power system and with SVC system.(2) The linear model of system is got by ways of feedback linearization technology. The SVC of the fuzzy sliding mode controller is designed by integrating fuzzy control and sliding mode variable structure control with their respective advantages. Fuzzy-controller effectively eliminates the chattering caused by variable structure control. (3) The FPSS controller is designed for the single-machine infinite bus power system above. The parameters of controller which designed by ways of formula inherent is self-adjusting.(4) The simulation proved that SVC controller can effectively improve the system power environment, power and power angle changes can be subsided rapidly. FPSS can suppress oscillations more effectively.