Research And Design Of Micro Grid Connected Photovoltaic Inverter

Compared with the traditional fossil energy, photovoltaic grid-connected generation has advantages such as clean, non-pollution, renewable, and so on. Especially, the micro photovoltaic grid-connected inverter has been applied in numerous solar power systems widely. High frequency isolation transformer is adopted to suppress the common mode current mainly in traditional micro photovoltaic grid-connected inverter topology. However, this method causes problems easily such as transformer saturation, system efficiency reduction. Therefore, a new type of non-isolated micro photovoltaic grid connected power generation topology is designed in this paper, which can reduce the common mode current effectively and lower the capacity of decoupling capacitors by improving the control strategy.The main content is listed as follows:Firstly, the basic principle of photovoltaic grid-connected generation is introduced in this paper, and the mathematical model of the photovoltaic cell components is established. Meanwhile, the maximum power point tracking control method of photovoltaic grid-connected generation system is analyzed in detail.Secondly, a new type of non-isolation photovoltaic grid-connected inverter topology is designed and its working principle is analyzed. And the structure has a good restraint effect on common mode current through the MATLAB simulation. Then, a small power resistance is used in the clamp channel to further improve the effect of suppressing the common mode current of the topology.Thirdly, a new type control strategy of photovoltaic grid-connected inverter is proposed in this paper. It is verified by MATLAB simulation that this control strategy can play important role in stabilizing the intermediate DC voltage level and reducing the decoupling capacitor capacity. In addition, as the proportional resonant(PR) control is used to track the sinusoidal signal of a certain frequency, and the open loop gain is infinite, so the real-time tracking without static error can be achieved. Therefore, the PR controller is adopted for grid-connected current inner loop control in this paper.Finally, on the basis of theoretical analysis and simulation, the software and hardware of system are designed, and the grid-connected experiment is also carried out. The correctness and feasibility of the practice scheme are verified by the results of the simulation and experiment.