A space vector phase-locked-loop approach to synchrophasor, frequency and rocof estimation

Phasor measurement units represent the most advanced measurement devices in ac power systems. Their most important feature is permitting to estimate synchrophasor, frequency and rate of change of frequency of voltages and currents in a shared, synchronized timescale. Most of the estimation algorithms have been designed to operate with a unique signal; however, ac power systems are inherently three-phase and weakly unbalanced during regular operation. Therefore, these three-phase signals benefit from peculiar properties than can be leveraged by specifically suited measurement algorithms. For this reason, space vector based techniques have been proposed. Usually, the reference frame is supposed to be stationary or rotating at the rated angular frequency. This work proposes to exploit measurements performed in a previous reporting instant in order to generate the instantaneous angular position of the reference frame, so that it tracks the phase evolution of the positive sequence synchrophasor. A P class implementation is reported, and the results highlight excellent performance. Accuracy is remarkable even under conditions going well beyond those required by compliance tests.