In this paper a straightforward method for line independency-based modelling of electrical power distribution systems is proposed. The proposed method can determine the backward and forward sweeping routes of distribution systems for calculating line currents and bus voltages. To do that, the method identifies the independent lines in consecutive steps. An independent line is a line in the distribution system whose current does not depend on the current of other lines in the system. The proposed line independency-based network modelling is required to be performed only once and prior to the load flow analysis. The output of the proposed method, which is suitable for backward/forward load flow analysis, includes matrices which determine the steps, the order of lines, and the start and end points in the system for hierarchical calculation of currents and voltages. In this paper, the forward/backward approach is used as the load-flow algorithm since it is suitable for radial distribution systems with unbalanced loads. The proposed methodology is applied on two IEEE distribution systems and the results show its efficiency in load flow analysis.

Demand response (DR) and flexible AC transmission system (FACTS) devices can be effectively used for congestion management in power transmission systems. However, demand response program (DRP) implementation can itself affect the optimum location of FACTS devices, which is one of the main issues in power system planning.This paper investigates the impact of DRPs on unified power flow controller (UPFC) placement. The harmony search algorithm is employed to determine the optimum locations and parameter setting of UPFC in a long-term framework.The optimization problem is solved with different objectives including generation and congestion cost reduction, as well as loss reduction. In this paper, the proposed approach is analyzed using 5 different cases, which are defined in such a way that they demonstrate the impact of DRPs on the UPFC placement problem. The IEEE reliability test system is used as an illustrative example to demonstrate the necessity of considering DRPs for UPFC placement.