Optimal reactive power planning method enhancing voltage stability margin using successive multiobjective fuzzy LP method

Lack of adequate reactive power support in a transmission system limits the real power transfer capacities leading to low voltages and Voltage Collapse (VC) at load centers. This paper presents a Successive Multiobjective Fuzzy LP (SMFLP) method to optimally site and size shunt capacitors such that the cost of the newly sited capacitors is minimum, the real power transmission loss is minimum, and the Voltage Stability Margin (VSM) is maximum while obtaining the utmost satisfaction of all the violated load bus voltage constraints. The SMFLP method uses the Successive LP (SLP) framework to successively linearize the Nonlinear Programming (NLP) problem of Optimal Reactive Power Planning (ORPP) and uses the Multiobjective Fuzzy LP (MFLP) technique to solve the linearized LP problems. Singular values of the Load flow Jacobian based Index (SLJI) is used to rank and select the best prospective sites for siting shunt capacitors. A set of few least singular values of the load flow Jacobian is used as VSM indicator. This set is expressed in terms of the control vector and is optimized to maximize VSM in the proposed method. The SMFLP method of ORPP was tested upon 6 and 57 bus IEEE test systems. The results of the studies are presented showing the effect of ORPP on the singular values of the load flow Jacobian.