Interferences between local voltage control strategies of HV/MV-transformer and distributed generators
Local reactive power provision by photovoltaic (PV) inverters can contribute to maintaining the voltage in distribution grids and therefore contribute to reduce grid reinforcement measures, caused by an increased PV penetration. This study investigates the interferences and dynamics of a parallel and autonomous operation of HV/MV on-load tap changer (OLTC) control and autonomous PV inverter control. The focus of this investigation is to identify whether reactive power provided by PV inverters can cause an increase of HV/MV transformer tap changes. The analysis is based on simulations of a real German distribution grid with a high share of PV generation. To incorporate realistic power fluctuations of PV systems in the investigated grid, geographically distributed solar irradiation measurements are used as input data for the simulations. The simulations show that reactive power provided by PV inverters can lead to an increase of reactive power fluctuations over the HV/MV transformer and can thus cause a significant increase of OLTC tap changes. The number of additional tap changes depends on the reactive power control strategy of the PV inverters.