The Design Of3KW Single-phase Photovoltaic Grid-connected Inverter

Under the background of energy depletion and serious environmental pollution, people pay more and more attention to the photovoltaic power generation technology. Photovoltaic grid-connected inverter is the core of the entire photovoltaic power generation system to realize the conversion and control of energy. And its performance largely affects the stability and efficiency of the system, so the design of photovoltaic grid-connected inverter is extremely important.In this paper, a3K.W single-phase photovoltaic grid-connected inverter is designed. The inverter adopts two-stage and non-isolated structure, the former stage uses Boost converter to realize the boost of the photovoltaic cells’output voltage and maximum power point tracking(MPPT), and the latter stage uses the classic single-phase full-bridge inverter to complete the inversion. In this paper, some control strategies are compared and analyzed. The system includes booster, inverter and filter parts, they are respectively designed in this paper. The system uses TMS320F2808to control the MPPT, the DC bus voltage, the pulse width of DC/DC and DC/AC, etc.In this paper, photovoltaic cells’MPPT technology is also studied. After comparing several common MPPT algorithms, an improved variable-step perturbation and observation method is proposed, the effectiveness of the method is verified by Simulink. In addition, the MPPT methods based on fuzzy control and neural network are respectively proposed. Because the perturbation and observation method exists oscillation and erroneous judgment, a MPPT method based on power prediction is proposed. The islanding effect detection of photovoltaic grid-connected system is also studied in this paper, a bi-directional periodic perturbation active frequency drift method is proposed, and the effectiveness of the method is also verified by simulation.Based on the theories in this paper, the hardware and the software of3KW single-phase photovoltaic grid-connected inverter are designed. Finally a prototype is made, and the results of the prototype verify the effectiveness of the system’s design and control strategies in this paper. The grid-connected current of the prototype is high-quality and the indexes, including European efficiency and THD, all satisfy the system’s requirements.