Real-time voltage stability assessment using phasor measurement units: Influence of synchrophasor estimation algorithms

Power network operators are rapidly embracing the synchrophasor technology for real-time stability assessment due to its superiority over conventional supervisory control and data acquisition (SCADA) systems. Synchrophasor devices (i.e., phasor measurement units (PMUs)) are procured from different vendors to construct the wide-area measurment systems (WAMSs), and hence the PMUs from different vendors may be based on different synchrophasor estimation algorithms (SEAs). Although all synchrophasor devices comply with the IEEE synchrophasor standard, stability assessment using the phasor estimated via different synchrophasor device types may lead to different stability assessment outcomes. This paper investigates the effect of SEAs on real-time voltage stability evaluation. Three prominent synchrophasor algorithms, namely quadrature demodulation (QD), discrete Fourier transform (DFT), and phasor locked loop (PLL) algorithms are considered in this study. Real-time voltage stability was assessed using an enhanced Lyapunov exponent based algorithm. Enhancements to the Lyapunov exponent based real-time voltage stability assessment algorithm are proposed while considering practical implications. The New England (NE) 39 bus system is used as the test system, and PMUs are placed in the test system to achieve optimal observability by using an optimal PMU placement (OPP) algorithm. Simulation results show that each SEA detects the instability condition under different time-frames, while some SEAs could make false alarms under certain dynamic conditions. Therefore, a rigorous benchmark process should be mandated via standards to ensure a consistent stability assessment process from synchrophasor network.