Synchronization to Disturbed Utility-Network Signals Using a Multirate Phase-Locked Loop

This paper presents a digital-signal-processing system suitable for synchronization in applications where the synchronization signal is severely disturbed, and where the signal frequency and amplitude are variable. The system is based on a multirate phase-locked loop. The main advantages of the multirate approach are that it relaxes the implementation of the antialiasing filter, and it enables one to accommodate the varying amplitude of the input signal. The antialiasing filter, which is in this case a high-order bandpass filter, is implemented in the digital part of the system. This feature is achieved by applying the oversampling technique to the input signal. The antialiasing filter automatically adapts to the input-signal-frequency variations through the system´s variable sample-rate operation. This paper deals with modeling, analysis, control, and implementation issues of the proposed system. The system is implemented on a platform based on the Texas Instruments TMS320C31 digital signal processor. Tracking properties of the implemented system are verified with realistic signals such as a sinusoidal signal containing notch-type disturbance and noise and an arc-furnace voltage signal