| With the rapid development of modern science and technology, various non-liner electricdevices were increasingly widespread applied in various fields such as electric system,industry, transportation and family. These devices provide high-speed, high efficiency andenergy-saving control, but also bring out a large of harmonics and reactive currents which leadto reducing power quality and polluting the security, stability and economic environment ofpower system. Active power filter is a kind of electronic device to optimize the power qualityefficiently and flexibly, to restrain harmonic and compensate reactive power dynamically. Theresearch is focused on the active power filter in this thesis.By applying fuzzy control in active power filter and by relying on MATLAB/SIMULINKas the design platform, an active power filter based on fuzzy control is proposed in this thesis.Detailed analysis of the various harmonic current detection algorithms and compare theiradvantages and disadvantages, the ip-iqalgorithm is selected out because it has high detectionprecision and widespread application. But in certain circumstances, the traditional activepower filter based on ip-iqalgorithm and hysteresis comparator current tracking control willrun slightly worse. Aimed at this defect, the tracking circuit is improved by involving fuzzycontrol in current track. The variate-value between the compensation current command signaland the actual compensation current signal as an input value, the change rate of variate-valueas another input, the fuzzy controller outputs a PWM signal to control the main circuitswitching on/off. By adding compensation current to the grid, the harmonics is offset andpower quality is improved greatly.In this thesis, the simulation experiment of improved fuzzy system is executed, and theexperiment results prove that active power filter based on fuzzy control can suppress theharmonics, purify the grid pollution, improve the power quality, and achieve the desired bestresults. |
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