Grid-connected PV plants. Power quality and technical requirements

Nowadays, there are a large number of photovoltaic (PV) plants connected to the distribution networks of some European countries such as Germany, Italy or Spain. In some cases the level of PV penetration in the energy mix of these countries has been increasing strongly over the last few years, as is the case of Spain, without determining the real influence of these facilities. The current technical problems of distribution companies and network operators due to PV distributed generation (overvoltage in nodes, reverse power flow, the islanding, voltage sags, reactive power demand...) are solved assuming new stringent regulatory requirements for all PV energy producers. There are situations that may affect the power quality and proper operation of distribution network, mainly in low demand cases with several generation plants connected to the same grid. In this paper power quality parameters as voltage level, frequency, power factor (PF), harmonic distortion, flicker and voltage unbalance have carried out at different Spanish distribution networks, in order to observe their evolution from the AC side of PV inverters and the point of common coupling (PCC) to the electrical power substation. The main phenomena that could affect the proper functioning of the network are showed and described in this paper, pointing out the main problems that could affect the increased penetration of PV plants in the network.