Impact of DG on Voltage Unbalance in Canadian Benchmark Rural Distribution Networks

Distribution networks are three-phase systems supplying electricity to loads. While, ideally, the load at each point of the network would be equally distributed among the three phases, this is not the case in practice. The three-phase voltages and currents are thus unbalanced due to the different magnitudes of loads at each phase. The integration of single-phase distributed generation (DG), e.g., photovoltaic (PV) units installed at secondary networks, adds more challenges to the voltage unbalance in distribution networks. This paper investigates through simulations the impact of DG on the voltage unbalance in Canadian benchmark rural distribution networks. The maximum penetration levels of DG that can be integrated into distribution networks are determined taking into consideration the standard limits of voltage unbalance, operating voltage limits, and thermal ratings of the feeder. Different configurations of voltage regulators and DG are studied. Simulation results showed that the voltage unbalance factor (VUF) decreases with the integration of three-phase DG especially when high penetration levels of DG are located close to the end of the main feeder. Up to 24 MW of three-phase DG can be connected to the main feeder, which is 154% of the total peak load, without violating any of the limits. It was also found that the maximum size of a single-phase DG can be at least 3 times the peak load of a given node at any single-phase lateral.