MPPT Of PV Generation System Based On Variable Step-size INC Method

Solar photovoltaic power generation is an important part of the new energyapplication, which has good prospects for development, obtained the widespreadattention. The photovoltaic system with maximum power point tracking control canmaintain the output power of the system at the maximum power. It is the main meansto improve the overall efficiency of the system. The maximum power pointtracking control usually uses impedance matching principle, uses a DC/DC circuitconnect the PV module and load, by adjusting the switching frequency of theswitching device in DC/DC circuit, realizes impedance matching, to achieve thepurpose of maximum power transmission. International and domestic academics havedone a lot of research on the photovoltaic maximum power point controltechnology, designed a variety of methods to control, achieved rich results.Through analyzing the output characteristics of photovoltaic cells, and the workingprinciple and characteristics of commonly used maximum power point tracking controlalgorithm. Aiming at the problem that the traditional variable-step INC method can notmaintain good tracking performance, because of the scope of work under the variablestep-size tracking mode has been changed when the illumination changed. According tothe characteristics of the PV array’s output power, the output power as adynamic correction into the switch condition between the fixed step-size tracking modeand the variable step-size tracking mode, the variable step tracking mode can work tokeep good performance. At the same time, optimize the step change rules of variablestep mode, making the variable step-size tracking process more smoothly.Use of the engineering model of photovoltaic array, established the simulationmodel of photovoltaic cells in MATLAB/simulink simulation platform. According to thesystem structure of independent photovoltaic power generation, based on the Boostcircuit as the DC/DC conversion circuit, further established the simulation model of thephotovoltaic maximum power point tracking control system. Simulated changes ofillumination, the tracking performance of the traditional variable step-size incrementalconductance method and the improved algorithm are simulation tested.Finally, based on digital signal controller dsPIC33FJ64GS606which produced byMicrochip company as the core control chip, according to the circuit structure of thecontrol system, completed the system hardware circuit design. The control principle of the control algorithm, using the software of MPLAB IDE to complete the design ofsystem software. Set up the illumination control circuit, artificial illumination changesin the indoor, the tracking performance of the traditional variable step-size incrementalconductance method and the improved algorithm are tested.Simulation and experiment indicate the effectiveness of the improved variablestep incremental conductance method. The simulation and experimental results showthat, the improved control algorithm has better robustness and adaptable than thetraditional variable step size algorithm, Especially in rapid illumination changessituation, the proposed method can maintain a good dynamic performance andsteady-state precision.