Stochastic assessment of the impact of photovoltaic distributed generation on the power quality indices of distribution networks

•Power quality indices based on the cumulative duration are evaluated.•DG may degrade the voltage conformity indices in feeders with voltage regulators.•The connection of DG increases the lifespan of the voltage regulators.•DG causes large variations in the voltage unbalance indices.•Power quality is less affected by the photovoltaic DG than the fossil DG.

This paper aims to assess the impact of photovoltaic distributed generation (PVDG) connection on the power quality indices (PQI) of distribution networks, such as: long term voltage variations (voltage conformity issues) and voltage unbalance. The stochastic nature of PVDG and loads were considered in the study using probabilistic techniques. The impact of PVDG on the number of tap changes of the voltage regulators was investigated. The tests results in a real life large scale distribution network demonstrated that the PVDG can cause around 31% of improvements in the voltage conformity indices. This impact is less beneficial than the one associated with the connection of conventional distributed generation due to the variability in the primary energy resource. Furthermore, it was demonstrated that the connection of PVDG increases the lifespan of the voltage regulators as a result of a reduction about 20% in the number of tap changes.