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Synchronization techniques for power quality instruments

Voltage characteristics measurement in power systems requires the accurate fundamental frequency estimation and the signal synchronization, even in the presence of disturbances. In this paper, the authors have developed and tested two innovative techniques for instrument synchronization. The first is based on signal spectral analysis techniques, performed by means of chirp-Z (CZT) analysis. The second is a PLL software, based upon a time-domain coordinate transformation and an innovative phase detection technique. In order to evaluate how synchronization techniques are adversely affected by the application of a disturbing influence, experimental tests have been carried out, taking into account the requirements of the standards. The proposed techniques have been compared with standard hardware solutions. In the paper, the proposed techniques are described, experimental results are presented and the accuracy specifications are discussed.