Linear State Estimation Considering Refresh Rates of RTU and PMU Measurements

Phasor measurement units provide synchrophasor measurements that are more accurate and have a higher refresh rate than the conventional measurements obtained via remote terminal units. Estimating the state of a system after each update of synchrophasor data can allow for tracking dynamic behaviour of the system. However, the issue of partial system observability by synchrophasors needs to be overcome. In this paper, three fully linear weighted least square-based state estimation algorithms are proposed to address the mismatch between refresh rates of synchrophasor and conventional measurements. State estimates are provided at time instances when both types of measurements are refreshed, as well as when only a new set of synchrophasors arrives. Simulations are performed on a number of test systems of different sizes to evaluate and compare performance of the proposed algorithms.