Realization of Wavelet Soft Threshold De-noising Technology Based on Visual Instrument

Electric power network injects with amount of harmonic current because of widespread use of nonlinear load, which does great harm to the using electricity consumption. In order to prevent harmonic current from influencing safety of system’s operation, we should know how much the distorted wave contains harmonic and take corresponding measure to make suppression or compensation of it. But due to a lot of noise affect existing, so detection result is inaccuracy, by using multi-resolution wavelet method, we get more accurate network voltage and currency, which can carry on next harmonic detection, etc. By simulation software of MATLAB combing with LabVIEW, wavelet de-noising has better function in filtering high frequency and noise signal, etc than traditional low-passing filter of Butterworth. Through harmonic detection simulation, result is exact through THD% calculation, which difference between standard value and measurement value is very small in THD% measurement error of 0.01%. Wavelet soft threshold de-noising technology can be applied into other monitor, such as three-phase unbalance factor monitor, frequency tracking monitor, fundamental wave monitor, etc.