In power system operation, it is necessary to consider both security and economy which are contradictory to each other. A very powerful means to satisfy this requirement is Optimal Power Flow (OFF). The Newton OFF with sparsity technique seems suited to on-line use from the viewpoint of computational speed. However, the method has several defects concerning convergence characteristics. This paper studies the following two problems to be overcome to use it in on-line tasks.
First, the P-Q decoupled OPF, which is usually faster than coupled one, does not converge in some systems. For such cases, we propose to introduce a decelerating factor to improve its convergence characteristics. Next, when many constraints are violated and enforced simultaneously, convergence tends to be difficult or the solution sometimes converges at a non-optimal point. Therefore, it is very important to identify binding inequalities effectively. In this paper, we propose an effective method of identifying binding inequalities based on the. Kuhn-Tucker condition. The validity of the proposed method is confirmed through numerical simulations on several test systems.