Decentralized Robust State Estimation of Active Distribution Grids Incorporating Microgrids Based on PMU Measurements

The development of active distribution grids brings with it a demand for a higher accuracy of state estimation. Micro-phasor measurement units (μPMUs) deployed in distribution grids provide necessary but insufficient support for the state estimation of enhanced performance. This paper deals with a decentralized PMU-based robust state estimation of active distribution grids incorporating microgrids. The PMU-based robust state estimation is formulated as a quadratic programming problem and solved in a decentralized manner to accommodate the autonomous operation mode among microgrids, as well as to preserve information privacy between different operators. During each iteration of the decentralized method, each microgrid evaluates its bad measurements and sends its local optimization objective with respect to boundary states to the utility grid for a unified optimization. The proposed iteration scheme between the utility grid and microgrids has significant advantages over regular iteration methods, in terms of its convergence rates and minimal data exchange between operators. Case studies of different systems are presented that demonstrate the exactness and efficiency of the proposed method.