Voltage Control in Low Voltage Networks by Photovoltaic Inverters – PVNET.dk

Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products already on order provided that such alterations can be made without subsequential changes being necessary in specifications already agreed. All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. This work is licensed under a Creative Commons Attribution-NoDerivs 3.0 Unported License 2 3 Summary This report provides an analysis on the main voltage regulation techniques that can be applied in the low voltage (LV) network with standard photovoltaic (PV) inverter technology. The main purpose of the research is to verify if reactive power can be used in LV networks to increase the hosting capacity, by controlling the voltage and hereby increase the hosting capacity of the LV networks. The hosting capacity of a LV network is defined by the amount of PV power which can be installed in the network before certain limits are reached. The evaluated limits in this report are: overloading of LV cables, overloading of MV/LV transformers and overvoltage at the outermost distribution box. Two types of Volt-VAR control schemes are presented: the power factor depending on active power output of the PV inverters-PF(P) and reactive power depending on the terminal voltage of the PV inverter-Q(U). A generic LV grid model with 71 users and a 100 kVA feeding transformer is used in the simulations, being considered as representative for the Bornholm network. All users are equipped with PV systems, each of equal power size and PV panel orientation. Furthermore, a simple MV network is implemented in order to observe the voltage variations in the 10 kV network as well. The energy consumption for each of the 71 users is based on time-series of generic consumption. The PV generation is based on synthesized hourly irradiance by the PVsyst software, taking both clear sky and covered sky into consideration. The results indicate that without voltage control the overvoltage phenomena starts for a PV capacity of 1.5 kW per residence (total 107 kW). By applying a standard PF(P) control scheme, the overvoltage condition is avoided up to a PV penetration level of 1.8 kW per residence (total 124 kW) and still keeps the amount of exchanged reactive power low, PF > 0.95. By applying Q(U) control, the overvoltage …