A decoupled semismooth Newton method for optimal power flow

In the deregulated environment, optimization tools that coordinate both system and security and economy are widely used to support system operation and decision. In this paper, we present a new decoupled approach to solve optimal power flow (OPF) and available transfer capability (ATC) problems. First, the KKT system of original optimization problem is reformulated equivalently to nonsmooth equations using a so-called nonlinear complementarity problem (NCP) function. Based on the new reformulation, we then apply the inherent weak-coupling characteristics of power systems and design a decoupled Newton algorithm in which a decomposition-correction strategy is considered. The combination of semismooth Newton method and decoupled strategy shares those advantages of two methods such as fast convergence and saving computation cost. Meanwhile, the new method is supported by theoretical convergence. Numerical examples of both OPF and ATC problems demonstrate that the new algorithm has potential to solve large-scale optimization problems.