Study On The Testing Method Of The Voltage Sag Based On Wavelet And DQ Algorithm

The voltage sag is one of most hot topics in dynamic electric energy problems. Nowadays, masses of new power and electron facilities have been put into use widely by people, and the normal working of those facilities, especially those sensitive ones, require a high quality of electric network and power, chiefly the voltage sag. Moreover, the voltage sag can spread in the electric network. So people have every reason to research and develop the voltage sag. However, before developing the voltage sag, people have to test it, because the results of the test would directly influence its development. On account of the above, this essay will chiefly focus on the test methods of the voltage sags.DVR is the most effective and popular equipment in the voltage sag. And it uses the fictitious three-phase DQ decomposition method. For having found some deficiencies of that method, this essay puts forward a new kind of the voltage sag test method—based on the wavelet and DQ algorithm .This new DQ algorithm grounds on unidirectional voltage's no time prolong structure, nevertheless, the fictitious three-phase DQ decomposition method can only get the other two voltage depends on the processing single-phase data. According to their different principles, the conclusion can be drew that the new method can overcome the latter's shortage.Taking the voltage sag related perturbation into consideration, during the progress of emulation, people can use the small wave's unique dominance in singularity testing to preprocess the voltage sag signal noise, and to pinpoint the voltage sag signal at the same time, and then utilize small wave's frequency division to extract low-frequency perturbation among the voltage sag signal. The emulation of this new method proves the lack of the synchronism and availability in the three-phase DQ decomposition method. On the other hand, the new DQ algorithm increases the testing accuracy, and the combination of the small wave and the new DQ algorithm can test the voltage sag completely in many aspects, such as the time of duration, phase-angle offset, noise interference and so on. The emulation also shows the small wave and DQ algorithm based method can arrived stable condition sooner than the fictitious three-phase DQ decomposition method.