System Modification Process to Reduce Calculation Complexity in Backward Forward Sweep Algorithm

In backward forward sweep algorithm, even though forward sweep (FW) to compute bus voltages, backward sweep (BW) is to compute branch currents, junction bus voltage calculation is required as mandatory additional step in backward sweep process. This calculation complexity increases with increase in number of junction buses particularly when loads are also connected to junction buses and consequently, execution time also increases. This paper concentrates on this problem and contributes with System Modification Process (SMP) to reduce Backward Forward (BW-FW) sweep algorithm calculations complexity. In SMP, transfer buses are connected to a given electrical distribution system to avoid calculating junction bus voltage, which is a mandatory step in backward sweep process, thus decoupling the voltage and current calculations. Hence in this present work, conventional backward forward sweep algorithm is modified as Decoupled Backward Forward Sweep (DBFS) algorithm. The system modification process is demonstrated with a 3-node lateral as numerical example and implemented on practical 55 bus three-phase unbalanced distribution system. In Matlab simulation, the efficiency of the DBFS algorithm has been tested with unbalanced radial distribution systems (URDS). The simulation outcomes in terms of number of repetition, execution time obtained, bus voltages per phase, and total computed power per phase with DBFS are compared to conventional BW-FW sweep algorithm results to demonstrate the proposed method efficiency. From the results, the proposed DBFS algorithm not only reduces conventional BW-FW sweep algorithm calculations complexity but also requires less amount of execution time (including SMP) to achieve same results without degrading the efficiency.