Graph-theoretic-based approach for solving load flow problem of AC-DC radial distribution network with distributed generations

Abstract

Owing to the rising power demand, depleting conventional energy sources and recent advancement in incorporatingdeeper injections of renewable energy resources into the grid, the existing distribution system will have to take into account DCinjections/withdrawals, thus giving rise to AC-DC distribution system. The load-flow in the aforementioned systems is an exigenttask because of the presence of power converters. This work presents a novel and computationally efficient load-flow algorithmfor AC-DC radial distribution network utilizing the notion of graph-theory with matrix-algebra. The remarkable trait of theproposed methodology lies in the formulation of path impedance matrix, loads beyond branch matrix, path drop matrix, slackbus to other buses drop matrix and load flow matrix which will remain unaffected for the entire load-flow operation. The per-unitequivalent model of power converters has been developed for solving load-flow equations in per-unit. Various models ofdistributed generations are also incorporated in the proposed load-flow study. The developed method is capable of addressingthe aforementioned modeling challenges. The proposed technique has been tested on several AC-DC test networks thatinclude different operating modes of power converters and various models of DGs, which proves feasibility and legitimacy of theproposed technique.