INVESTIGATION OF FACTORS CAUSING SLOW CONVERGENCE IN NEWTON OPTIMAL POWER-FLOW

Factors causing slow convergence in the Newton optimal power flow (OPF ) approach are presented in this paper. The solution speed of the appr oach is evaluated by the numbers of the main and trial iterations. The OPF discussed in this paper deals with minimization of the system MW losses while satisfying system security constraints by adjusting react ive power controllers. The factors causing slow convergence include (a ) insufficient sources of reactive power, (b) a solution space with a flat bottom, and (c) the load model. This paper helps to clarify the a mbiguous phenomena of slow convergence. The main phenomena, explanatio ns and termination criterion/enhanced treatment are presented for each factor. The IEEE 30- and 118-bus systems and a practical 217-bus syst em, namely, the Taipower system, are used to serve as samples in this paper.