Approach for linear state estimation considering zero-injected currents

With the increasing complexity of operating conditions, the operators of power system rely on the energy management system (EMS) more and more. The state estimation is the core of EMS. The invention of phasor measurement unit (PMU) provides new opportunities for state estimations. In China, all of the 500kV and above substations are equipped with PMU. The linear state estimation based on PMU measurements is possible. In this paper, the approach for linear state estimation based on PMU measurements is proposed. The detailed model of the linear state estimation is presented. To improve the accuracy, the zero-injected currents at connecting buses are considered as virtual measurements. The proposed linear state estimation is solved by the linear weighted least squares (LWLS). The IEEE 39 and IEEE 118bus testing systems are applied to test the proposed method. The simulating results show that the accuracy of the estimated states by the linear state estimation based on PMU is higher than the traditional nonlinear state estimations and the speed of computation is faster than the nonlinear estimation.