Study on novel model for optimal coordinated voltage emergency control

This paper presents an innovative model for optimal coordinated voltage emergency control (OCVEC), in which the dynamics of loads and the continuous/discrete nature of control measures are fully incorporated. Based on this model, a methodology for emergently maintaining voltage stability against voltage collapse is developed, with global coordination on various controls distributed over different geographical locations. For the construction of the optimization problem, the integral of load bus voltage deviations is defined as the voltage stability performance index (PI). Following the variation principle in the optimal control theory, the sensitivities of the PI with respect to control operations are exactly derived and evaluated using results from the quasi-steady-state (QSS) fast time domain simulation so that the intricate and formidable OCEVC model can be transformed into a tractable mixed-integer linear programming problem. The merits of this approach have been demonstrated by the case studies on the New England test power system.