Treatment of inequality constraints in power system state estimation

A new formulation of the power system state estimation problem and a new solution technique are presented. The formulation allows for inequality constraints such as VAr limits on generators and transformer tap ratio limits. In addition, unmeasured loads can be modeled as unknown but bounded quantities. The solution technique is an interior point method that uses logarithmic barrier functions to treat the inequality constraints. The authors describe computational issues arising in the implementation of the algorithm. Numerical results are given for power systems ranging in size from six to 118 buses