Static State Estimation with Inequality Constraints in a Complementarity Framework for Detecting Infeasible Operation States

Abstract

This paper presents a new approach for incorporating inequality constraints into the equality-constrained weighted least squares state estimator, without modifying the way in which this estimator is formulated and solved. In this proposal, the inequality constraints are first represented as complementarity constraints, which are then transformed into equality constraints by using the Fischer-Burmeister merit function. The resulting set of equations are directly included in the set of equality constraints associated with the original constrained state estimation problem; therefore, the infeasible operating state, which is associated with the violation of a system's physical limit, is automatically detected during the iterative solution of the estimation problem. Under this condition, the compliance of the system's physical constraints is also automatically performed during the estimation solution process. The proposed approach also provides information about physical limits that were enforced, which could be employed to analyze the infeasible state estimation's causes. The validity and effectiveness of the proposed approach is fully demonstrated in the IEEE 14-bus benchmark network, the CIGRE test system and in the 7659-bus representation of the Mexican interconnected power system.