Abstract
The Newton–Raphson (NR) method is still frequently applied for computing load flow (LF) due to its precision and quadratic convergence properties. To compute LF in a low voltage distribution system (LVDS) with unbalanced topologies, each branch model in the LVDS can be simplified by defining the neutral and ground voltages as zero and then using Kron’s reduction to transform into a 3 × 3 branch matrix, but this decreases accuracy. Therefore, this paper proposes a modified branch model that is also reduced into a 3 × 3 matrix but is derived from the impedances of the phase-A, -B, -C, neutral, and ground conductors together with the grounding resistances, thereby increasing the accuracy. Moreover, this paper proposes improved LF equations for unbalanced LVDS with both PQ and PV nodes. The improved LF equations are based on the polar-form power injection approach. The simulation results show the effectiveness of the modified branch model and the improved LF equations.
Highlights
Newton–Raphson Power Flow forA low voltage distribution system (LVDS) is responsible for providing electricity to end-users and connecting with its distribution transformer, which receives electricity from a medium voltage feeder
The current injection NR method with the modified 4 × 4 branch matrix can suffer from the lack of convergence in the LVDSs with PV nodes [10] where the 4 × 4 branch matrix neglects only the voltage existence of the ground conductor
Improved load flow (LF) equations are proposed for the application to the unbalanced DSs with both PQ and PV nodes where, at the PV nodes following [13,14], the voltage magnitude and phase angle of each phase are balanced and the sum of real power generation of each phase is constant
Summary
A low voltage distribution system (LVDS) is responsible for providing electricity to end-users and connecting with its distribution transformer, which receives electricity from a medium voltage feeder. The current injection NR method with the modified 4 × 4 branch matrix can suffer from the lack of convergence in the LVDSs with PV nodes [10] where the 4 × 4 branch matrix neglects only the voltage existence of the ground conductor. Improved LF equations are proposed for the application to the unbalanced DSs with both PQ and PV nodes where, at the PV nodes following [13,14], the voltage magnitude and phase angle of each phase are balanced and the sum of real power generation of each phase is constant.
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