Research And Development Of3kW Photovoltaic Grid-CFonnected Inverter System

With the development of society, the traditional energy is gradually drying up. As theSolar Energy has the advantage of non-pollution, wide distribution and abundant, moreand more people pay attention on it. Photovoltaic Inverter is the power converter stage ofgrid-connected PV system which has relationship with system performance and life. Inthis context, this paper discusses about the research and development of PhotovoltaicInverter as follows:Topology Structure of PV Inverter is studied and a one-phase, two-stage,transform-less scheme is selected to meet the commands. Several commonly usedMaximum Power Point Tracking (MPPT) algorithm is analyzed. To ensure the rapidityand stability of tracking, variable step Perturbation and Observation method based on P-Ucurve slope is proposed. Then, invert strategy is analyzed. Through analyzing theadvantages and disadvantages of current control method, Repeated PI Control is used torealize non-error tracking. The origin of DC Bus voltage oscillation and the effect on theoperating point of PV panel is also analyzed. The use of a novel compensation algorithmbased on feed-forward control is proposed to attenuate this oscillation. This algorithm isachieved by adding a duty cycle component D to the output of MPPT controller.By using Saber software, the simulation model of Photovoltaic Grid-ConnectedInverter is build and the validity of selected structure, MPPT algorithm, on-grid strategyand supression algorithm is verified.Based on the theory above, the hardware and software of3kW PV Grid-ConnectedInverter are designed. Experiment on maximum power point tracking, on-grid invert,oscillation suppression and long-term operation is accomplished. The results show that thesystem meets all the demand and has good performance.