Optimal capacitor allocation in radial distribution systems for loss reduction: A two stage method

This paper presents an efficient approach for capacitor allocation in radial distribution systems that determine the optimal locations and sizes of capacitors with an objective of reduction of power loss and improving the voltage profile. A loss sensitivity technique is used to select the candidate locations for the capacitor placement. The size of the optimal capacitor at the compensated nodes is determined simultaneously by optimizing the loss saving equation with respect to the capacitor currents. The performance of the proposed method (PM) was investigated on several distribution systems and it was found that significant voltage profile improvement and loss saving can be achieved by optimal allocation of capacitors in the system. However this method is sensitive to the distribution network configuration. In a 28 node feeder the matrix of capacitor sizing becomes close to singular or badly scaled and results may be inaccurate. In 85 node feeder the same matrix becomes singular and no solution obtained. For the 28 node feeder a two stage technique is proposed: a reconfiguration of the feeder in the first stage followed by optimal capacitor allocation as a second stage. For the 85 node feeder a slight movement of the capacitor location was sufficient to reach optimal capacitor allocation. The proposed two stage technique is also applicable to the 85 node feeder for given optimum configuration of the tie switches. Simulations, using genetic algorithm are conducted for the two (28 and 85 nodes) systems allowing detection of loss reduction and voltage improvement due to capacitor placement.

► Optimal capacitor allocation in radial distribution systems is determined with an objective of reducing power loss and improving the voltage profile.
► Optimal capacitors sizes at the compensated nodes are determined simultaneously by optimizing the loss saving equation with respect to the capacitor currents.
► Two stages technique is proposed to ensure solution of optimal capacitor allocation problem for capacitor locations creating close to or singular capacitor sizing matrix.
► This is achieved by system reconfiguration as a first stage followed by optimal capacitor allocation as second stage.