Optimal Switching Threshold Based Static Var Compensator

Due to the increasing loads of electric power system, demand on reactive power isalso increasing. To reduce the reactive power transmission on the power line, it isnecessary to install the reactive power compensation devices in proper position ofelectric network.Based on the analysis of compensation principle, capacitors connection way andthe control strategy, considering the economical efficiency, an optimal switchingthreshold based static var compensator is designed in this thesis. Combining the fuzzycontrol theory and the nine-region controlling method, a kind of intelligent voltageand reactive-power fuzzy controller is designed to adjust the transformer tap as wellas the capacitors switching. The compound criterion is effectively overcome thedefect of switching oscillation. Through the simulation, it's validated that thiscriterion can effectively control the electric network voltage and process the reactivecompensation.Considering the superiorities of the binary encoding mode allocated capacitors,the optimum threshold of binary encoding mode based switching capacitors isdiscussed on this paper. It is verified that the equivalence distribution principle is theoptimal threshold of switching capacitors principle based on the binary encodingmode and the optimum threshold value is provided. With the equivalence distributionprinciple, the reactive compensation would response more quickly and accurately.Combining the nine-region controlling based fuzzy controller and the equivalencedistribution principle of the optimum threshold, the hardware structure of thiscompensation device is given in the thesis. A zero-cross detection circuit is providedto insure that the thyristors are triggered in the zero-voltage condition thus greatlyreduced surge current. In this way, the optimal switching threshold based static varcompensator could fleetly and truly compensate reactive power.