Real-time method for detecting the fundamental component of line voltage

A real-time method for detecting the fundamental component of the line voltage under distorted circumstance is proposed in the paper. Voltage data within a fixed-width window are used to estimate the amplitude and phase of the fundamental component. The window moves with the time, so each observation time has its corresponding characteristic data. In this way, the method can work well even when the line voltage is changing violently. Then theoretical analysis is carried out to prove the fact that the method is also valid when the actual periods of the line voltage is slightly different from the width of the observation window under distorted and noisy circumstance. Moreover, if the line periods varies too much, this method can reduce the error by adjusting the width of the window to fit the line periods. Finally, the method is realized in real-time by two DSPs, and applied in an active power filter. Related results demonstrate the validity of the method and its usefulness in industry applications.