Study of WLS state estimation convergence characteristics under topology errors

Abstract

Power system state estimation determines the optimal system states based on the network model and the gathered measurements from the system. Weighted least square (WLS) state estimation is the most commonly used method in power industry, and it may suffer divergence under stressed system conditions. This paper investigates the impacts of variations of line power flow increment and topology errors on convergence property of the WLS state estimator. A simple 3-bus system and the IEEE 118-bus system are used as the test cases and simulation results are reported. Furthermore, this paper also studies the effect of adding phasor measurement unit (PMU) voltage phasor measurements to convergence property of WLS state estimation. Simulation results show that adding PMU measurements could generally improve the robustness of state estimation, but there exists a few special cases violating the rule and needs to be taken care when applying PMU measurements in state estimation.