| Flexible Alternating Current Transmission Systems, referred to as FACTS. FACTS is automatic control device which is composed of high-power electronic components. To optimize power system's mode by adjusting network parameters or operating parameters. It has the advantage of improving transmission ability and reducing backup capacity. As the weakness of our country's power grid structure and uneven distribution of power resources, the application of FACTS technique is much prospect in our country. UPFC is the latest generation of FACTS devices, and also the most powerful FACTS controller so far. Not only can it control the voltage on transmission line, but also control power flow. This paper introduced the research application status on UPFC.This paper analyzed the effect of UPFC on power system, established a 9-order linearization model considered the dynamic behavior of DC capacitor and UPFC control system, and used the characteristic value method to analyze small disturbance stability of power system including UPFC. The analysis considered different steady operating conditions.Power system has more requirements on control performance of UPFC controller. As the control process is increasingly complex, it is not possible to get the acurate mathematic model of controlled object, so traditional control performance of the conventional PI control based on accurate model is less able to meet the requirements of power system. Based on fuzzy control theory and PI control technology, aiming at the characteristics of the UPFC, this paper designed an adaptive fuzzy PI controller of UPFC, combining the two together with their respective advantages.Finally, through deep research on fuzzy control theory and fuzzy variable universe theory, the paper optimized adaptive variable universe on fuzzy adaptive PI controller designed before. It used MATLAB/SIMULINK software to simulate the above controllers. The simulation results show that the effectiveness and correctness of the design controller. |
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