An accurate voltage solution method for radial distribution systems

This paper formulates a set of equations (SOE) to describe a radial distribution system with high R/X ratio. The SOE comprises 3(N - 1) second-order equations and an equal number of variables for an N-bus system. The proposed method solves this SOE using the first-order Newton-Raphson technique. The SOE model accounts for elements such as transformers, transmission lines, shunt capacitors, constant PQ loads, and constant impedance loads. Irrespective of the R/X ratio values of the lines in the system, the SOE preserves a strong diagonal characteristic. As well, this SOE is devoid of bus phase angles, unlike the 2(N - 1) ac power flow equations used to describe transmission systems. The proposed method is compared with other methods reported in the literature for distribution systems, such as Newton-based methods and recursive methodologies that use forward and reverse sweeps. Tests conducted on radial distribution systems with 43, 69, and 5002 buses show the new method to be more accurate than other methods reported in the literature.