Effects of the Operating Point on PV Systems Equipped with Energy Storage

While the electrical characteristic of a photovoltaic (PV) generator has exactly one maximum power point (MPP) during uniform operating conditions, several MPPs may exist during non-uniform operating conditions. As strongly varying global MPP (GMPP) voltage produces large fluctuations in the inverter reference voltage, it would be advantageous to keep the inverter operating point constantly close to the nominal MPP voltage to secure more predictable and straightforward operation of the PV system. This paper presents an experimental study of the effects of the operating point on the operation of PV systems equipped with energy storage systems. A scenario in which the MPP closest to the nominal MPP voltage is used all the time as the operating point is compared to operating at the GMPP. The effects of inverter sizing on the selection of the operating point of the PV systems are also investigated. The study is based on measured current–voltage curves of two PV strings.