The Research And Design Of Photovoltaic Grid-connected Microinverter System Based On FPGA

Distributed micro grid connected photovoltaic system, especially the buildingintegrated photovoltaic (Building Integrated PV, BIPV) power generation system,with the advantages of little investment, short construction period, covering an area ofsmall, policy support and so on, has become the mainstream of grid connectedphotovoltaic power generation. Micro inverter (Micro-inverter, MI) is the core part ofthe micro grid connected PV system, its working efficiency, output waveform qualityand reliability directly determines the performance of system. Therefore, the researchof grid connected photovoltaic micro inverter has the very high engineeringapplication value.Firstly, this paper studies the basic structure and working principle ofphotovoltaic cells, and gets the engineering mathematical model, then sets up thesimulation model based on Matlab/Simulink simulation platform. The simulationresults show that the model can simulate running situation of photovoltaic cells undervarious conditions.Secondly, this paper analyses several common maximum power point trackingcontrol algorithm, and then considering from two aspects the rapidity and accuracy,combined with the method of advance and retreat and the golden section method, thispaper proposes a new type of maximum power point tracking algorithm. Thisalgorithm can solve the problem of oscillation energy loss, and the simulation resultsverify the feasibility of the algorithm.Then, according to the MI’s small size and high efficiency, this paper adopts highfrequency transformer isolation type two level power converter topology, i.e. the firstlevel circuit using the DC/DC topology and the second level circuit using the DC/ACtopology. In addition, this paper also presents a novel flyback converter based on softswitching technology model, and the circuit is applied to the first level DC/DCtopology structure in order to reduce the high frequency loss of power switch tube.Then, this paper introduces the photovoltaic grid connected MI system structure,and studies and designs the control strategy of the system after the establishment of the control model of the system. This paper analyzes the PI control, the PR controland the quasi PR control, and compares their advantages and disadvantages andverifies them by simulation analysis. The simulation results show that the quasi PRcontroller has a smaller steady-state error and stronger anti-interference ability.Finally, taking FPGA chip of ALTERA company Cyclone IV series devices inmodel EP4CE10E22CBN as the core of controlling circuit, this paper introduces thehardware and software design of photovoltaic grid connected MI system.