Intra-minutes technical impacts of PV grid integration on distribution network operation of a rural community under extreme PV power delivery

Abstract

Integration of PV systems with distribution networks causes some technical challenges to the electrical grid and the distribution network. Most of the conducted researches concentrate on the long horizon impacts (hourly and daily based data). This study aims to capture the extreme technical impacts of PV grid integration on the distribution network at small time scale (few minutes) such that optimum mitigation techniques can be selected. The study assumes that the instantaneous peak power that would be generated from the PV array is considered constant (does not vary) for a small time frame such that the distribution network is subjected to the ultimate possible impacts (extreme impacts). Consequently, the extreme impacts are determined when the PV array produces the peak (extreme) power corresponding to the rating of installed PV array. The paper investigates the influence of both PV size (penetration level) and PV location (siting) on several technical issues such as: voltage profile at different buses, power losses across cables and short circuit currents at different nodes subjected to symmetrical fault conditions. In addition, the impacts on the total harmonic distortion (THD) of buses voltages and currents have been computed. The 3-Φ grid-connected inverter is controlled by instantaneous power control strategy to adjust the penetration level to the desired value. The obtained results indicate that the increase in PV penetration level improves the voltage profile along the network nodes and leads to a reduction in power losses across the cables as well. However, the PV grid integration has adverse effects on the distribution network protection system since the increase in PV penetration level results in higher values of the short circuit currents under symmetrical fault conditions compared with the network without renewable resource. Accordingly, the settings of overcurrent relays have to be revised to handle the under-reach (blinding of protection) or over-reach (sympathetic tripping) conditions of the relaying protection system. Moreover, the obtained results indicate that the THDs are negatively affected by the increase of the penetration level. Owing to the results, the PV allocation (PV injecting node) has also its own effects on the distribution network. The overall system is investigated using professional version of PSIM.