New EPS state estimation algorithms based on the technique of test equations and PMU measurements

Large system blackouts that have occurred in different countries in the first five years of the new millenium prove the need of updating and improvement of software for EPS monitoring and control (SCADA/EMS-applications). The updating of software for EPS monitoring and control (SCADA/EMS-applications) has become possible on a qualitatively new level owing to WAMS (wide-area measurement system), that allows the EPS state to be controlled synchronously and with high accuracy. The phasor measurement units (PMU) are the main measurement equipment in these systems. One of the applications, which will be significantly affected by the introduction of PMU, is the state estimation (SE). State estimation is an important procedure that provides reliable and qualitative information for EPS control. The state estimation results in calculation of steady state (current conditions) of EPS on the basis of measured state variables and data on the state of scheme topology. The measurements used for state estimation include mainly the measurements received from SCADA system. As compared to a standard set of measurements received from SCADA, PMU installed in the node can measure voltage phasor in this node and current phasors in some or all branches adjacent to this node with high accuracy. The use of additional high accuracy measurements improves observability of calculated network, enhances the efficiency of methods for bad data detection, increases accuracy and reliability of the obtained estimates.