A wavelet based power quality monitoring system considering noise effects

Based on the discrete wavelet transform (DWT), a power quality (PQ) monitoring system could easily and correctly detect and localize the disturbances in power systems. However, once the signal under investigation is corrupted by noise, the performance of the DWT on detecting the disturbance would greatly degrade, due to the difficulty in giving appropriate thresholds to eliminate the noises. To enhance the capability of the wavelet-based PQ monitoring system, this paper proposes a denoising approach for the detection of transient disturbance events in noisy environment. In the proposed denoising approach, the thresholds to eliminate the noises are adaptively determined according to the background noises. The abilities of the DWT in detecting and localizing the disturbances can hence be restored.