Studying Voltage Fluctuations in the MV Distribution Grid with a Renewable Energy Source

The increasing penetration of renewable energy sources (RESs), such as photovoltaic and wind power plants, into the medium-voltage distribution grid creates significant concerns regarding voltage control at local substations. Understanding the specifics of the RES operation impact on the phenomenon and propagation of voltage fluctuations in the distribution grid is important for engineering solutions in the RES design and operation practice. The presented article describes an algorithm for estimating the impact of RES on voltage fluctuations in the medium-voltage grid. The algorithm utilises a RES fixed power factor control mode and is implemented in a grid model developed using software for power flow calculations. The study shows the impact of various RES power factor types on the nature of voltage fluctuations in the distribution grid. The RES operation with lagging reactive power factors, as a method of reducing voltage fluctuation magnitudes, results in a more complex nature of voltage fluctuation propagation compared to those with leading power factor. Based on simulations of a true medium-voltage grid, the possibility of optimal mitigation of voltage fluctuations in a grid by selecting the required RES reactive power factor has been proven. The presented model also allows for calculating changes in distribution grid energy losses depending on the RES reactive power factors, ensuring a practical solution of the control strategy.