Static Operational Impacts of Residential Solar PV Plants on the Medium Voltage Distribution Grids—A Case Study Based on the Danish Island Bornholm

Driven by the Energy Strategy 2050 of Denmark, renewable energy sources (RESs) are increasingly integrated into the Danish power grid. Solar photovoltaic (PV) plants play an important role in this process. This paper conducted a study to investigate the impacts of residential solar PV integration in the distribution grid on voltage security and grid loss based on the 10 kV distribution grid in Bornholm. Three case studies are performed to test three different reactive power control methods, i.e., PF(P), constant PF and constant Q, at different penetration levels. The assessment of the impacts of PV integration and different control methods are done in the DIgSILENT PowerFactory. It was found that PV integration can contribute to reducing the loss of the system, increased overvoltage in buses and overload in transformers, and 40% penetration at the low voltage is considered to be an optimal level based on the result. PF(P) control gives the best performance among all three methods under the current grid codes. With constant PF control, it was found that the system loss can be significantly reduced if the PV systems operate with a power factor of 0.9 leading, which is not the norm of the current Danish grid code.