Prevention of overvoltage induced by large penetration of photovoltaics in distribution networks by electric vehicles

Large penetration of distributed photovoltaic (PV) systems in distribution networks (DNs) helps reduce greenhouse gas emissions. However, the peak generation of PV in the DN may be more than the total load demand, and the extra power can cause overvoltage issue. To solve this issue, we proposed to take advantage of ever-increasing plug-in electric vehicles (PEV) to absorb the extra generation and regulate the voltage. By using PEVs as energy storage when the PV generation peaks, the excess power can be shaved as well as the voltage can be controlled within a safe margin. We compared the distributed method (by using residential PEVs) and centralized method (by using electric taxi swapping stations). In the centralized management, an optimization algorithm is proposed to minimize network losses while maintaining the voltage security. Voltage sensitivity indices are used to calculate the number of needed PEVs. Power balance equations and the other practical limits are implemented as the constraints of the optimization algorithm. Simulation studies under various scenarios have been carried out on a 33-bus test feeder to verify the effectiveness of the solutions.