Research On 3kW Single-Phase PV Grid-Connected Inverter

Nowadays, with the rapid development of economy, the demand for energy is increasing gradually and environmental issues caused by traditional energy is concerned greatly. Faced with an increasingly serious problem of energy, since the solar energy is an abundant, renewable and clean energy, so all countries in the world has been paid more attention to it. The solar energy is applied mainly by photovoltaic generation, in addition, the grid-connected photovoltaic generation takes a large proportion in the market. So it has both theoretical and practical significance to study grid-connected photovoltaic inverter.A 3 kW single-phase grid-connected inverter is developed with two stage non-isolated circuit structure. The front stage uses boost circuit, and it will boost the PV array’s output voltage and complete maximum power point tracking. The back stage takes full-bridge topology with DC bypass, and it can be a good solution to the common mode current problem, and the simulation results show that the selected topology has a good inhibitory effect to common mode current.Then, the maximum power point tracking techniques is discussed. The characteristics of several common MPPT methods are analyzed and summarized. the oscillation and misjudgment of perturbation and observation method is analyzed, then a perturbation and observation method based on optimal gradient duty cycle is employed. Next, inverter control strategies are analyzed and the advantages and disadvantages of several common strategies are summarized. By analyzing and comparing PI, PR and quasi-PR control strategy, the quasi-PR inverter control strategy is applied in this paper. Finally, the Matlab simulation results for MPPT method and quasi-PR control strategy verify the feasibility of the improved disturbance and observation method and quasi-PR control.Lastly, based on TI’s TMS320F2812DSP control chip, inverter signal acquisition circuit, driven and protection circuits are designed, and the main circuit device selection and calculation process of the main parameters are presented. Moreover, a test prototype is designed and experimental debugging is carried out.The experimental results show that the improved disturbance and observation method can effectively eliminate oscillation and reduce misjudgment, and the full-bridge topology with DC bypass has a good ability to suppress common mode current, and quasi-PR control strategy generates little harmonic with good stable performance. Finally, the key indexes, such as efficiency, harmonics, power factor and so on, achieve the requirements.