Performance analysis of a mini-grid when connected to the main grid distribution network

Abstract

This study examines the technical performance of a mini-grid when integrated to the main grid distribution network. The extension of the national electricity grid to areas formerly served by minigrids in Uganda presents an alternative operation model to the mini-grids in a way that the two networks can be interconnected to allow energy exchange. The case study is 1.6MW Kalangala Infrastructure Services Hybrid Solar Thermal Mini-grid in Uganda. The study involved collecting data from field personnel which included power plant data, line parameter data, and daily load profiles. The mini-grid network was modeled using DigSilent PowerFactory software to simulate and analyze the distribution network both independently and when connected to the main grid. Parameters such as bus bar voltages, line losses, and power factor were examined under different operation scenarios. Results indicate that voltages remain within acceptable limits during normal operation when there are no fluctuations in solar power supply and no excess power generation. However, there are increased line losses upon interconnection with the external grid, due to the location of point of interconnection. The results further indicate that upon integration the fluctuations in solar power output will have no significant impact on voltage and power factor.