Single-phase multifunctional inverter with dynamic saturation scheme for partial compensation of reactive power and harmonics

Abstract

Single and three-phase photovoltaic inverters are essential components of the photovoltaic (PV) systems to extracting the PV power and injecting it into the grid. Thus, in order to extract the maximum power of the solar array for various solar irradiation tracks, it is used a maximum power point tracker (MPPT) algorithm. Due to variations in solar irradiance, inverters have a current margin, which is not explored during the day. Thereby, many works have proposed the multifunctional operation. This concept consists in aggregate to the inverter control strategy other functions, such as harmonics and reactive power compensation. However, most important fact and less related in literature is the necessity of techniques to compensate partially reactive power and harmonics of the load, ensuring that the inverter works below the rated current. Hence, the present work proposes a current dynamic saturation scheme in order to compensate partially reactive power and harmonics of the load during the multifunctional operation. Simulations show that the dynamic saturation prevents the inverter to inject low-order harmonics, while ensuring the operation below the system rated current. Furthermore, control performance is evaluated for five grid-connected PV system in parallel association, in order to show the effectiveness of proposed control strategy for various dispersed PV systems in the grid. To ensure that the proposed method is applied with the maximum efficiency of the PV system, this work compares, during inverter multifunctional operation, the instantaneous and dynamic efficiency between three MPPT algorithms proposed in literature: perturb and observe; dP — perturb and observe; modified perturb and observe.