A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Energy

Thesis (M.Eng.) - Asian Institute of Technology, 2008

Reconfiguration and capacitor placement are major conventional methods for loss reduction in distribution systems. The penetration of distributed generation (DG) into distribution systems has been increasing in many parts of the world due to environment concerns, electricity liberalization, etc. If DG is placed properly, it will be a new and effective method to reduce losses. However, the combination of reconfiguration, DGs and capacitors is considered as one of the latest and most effective methods to minimize losses. Such a combinatorial method is rather complex and can be better solved by some optimization techniques. Firstly, this thesis develops and improves the analytical based method using a novel comprehensive formula to find the optimal size, location and power factor of five types of single DG simultaneously to minimize losses. Secondly, an improved analytical (IA) based method is proposed to place optimal three types of multiple DGs and/or capacitors for loss reduction. Thirdly, an IA based method is also developed to solve optimal reconfiguration with multiple DG and/or capacitor placement. Finally, two loss sensitivity factor (LSF) and the exhaustive load flow (ELF) based methods to place either DGs or capacitors are developed and compared with the IA based method. The methods based on the IA, LSF and ELF techniques have been tested and validated on three test distribution systems. The results show that the IA based method can demand a short computational time as compared with the LSF based method; but it can lead to an optimal or near optimal solution as compared with the ELF based method. The LSF based method may not lead to the best allocation of DGs or capacitors for loss reduction. The IA based method has been applied to a 687-bus practical distribution system of Lam Dong Distribution Department under Power Company No. 2. The results indicate that the proposed method is efficient. When only one DG is considered to optimize the size, location and power factor simultaneously, the loss reduction is significant at 89.68%. When reconfiguration with placing one DG and a capacitor is considered, the loss reduction is better at 94.64%. As the combination of either six DGs and five capacitors or reconfiguration with six DGs and five capacitors, the loss reduction is highest at nearly 99%. However, the loss reduction will be reached at 100%, if the number of DGs is unlimited.