Abstract:

Based on the quasi-steady-state assumption, an optimal coordinated voltage control model consisting of the constraint of continuous and discrete time differential-algebraic equations is established, and a direct method from the modern optimal control theory is applied to solving this dynamic optimization problem. Then, according to Radau collocation method, the dynamic optimization problem is converted to a nonlinear programming one that contains continuous and discrete variables. Moreover, in order to consider the discrete characteristics of the turn ratio of on-load regulating transformer, the switchable capacitor bank and the shedding load, a nonlinear primal-dual interior-point algorithm incorporating the penalty function mechanism for discrete variables is used during the solving of this problem. Simulated results on New England 10-machine 39-bus system demonstrate that the proposed method improves the long-term voltage stability of power systems because it effectively coordinates the actions of different control devices

Key words: long-term voltage stability, coordinated voltage control, direct dynamic optimization, Radau collocation method, discrete control