| With the progress of industrial reforms,human society has entered an unprecedented level of prosperity,but behind the huge economic production capacity are problems such as energy waste,ecological imbalances and environmental pollution.As far as the current global traditional energy storage-production ratio is concerned,relying solely on the development of traditional energy sources can no longer meet people’s energy consumption needs.And the exploitation and utilization of these exhaustible energy sources will produce a wide variety of pollutants.In order to alleviate human’s pressure on energy and ecology,it is necessary to develop non-depleted clean energy such as solar energy and wind energy on a large scale.As a non-depleted clean energy,solar energy has the advantages of safe,green,low carbon,and inexhaustible.Therefore,the utilization of solar energy has become an important way to alleviate human’s pressure on energy.Because the output of the photovoltaic module itself has a strong nonlinear characteristic,it is difficult to maintain the operating point at the maximum power point during the photoelectric conversion process.And the light energy utilization rate is not high.Therefore,improving the photoelectric conversion efficiency is the primary problem to be overcome in the development of photoelectric utilization,and has practical research significance.Starting from the independent photovoltaic maximum power point tracking(MPPT)system,this thesis first analyzes the working principle and output characteristics of photovoltaic cells.And then it selects the Boost converter circuit with better performance in the DC/DC converter circuit according to the system needs.Finally,the algorithm flows and control principles of MPPT algorithm,which is commonly used in maximum tracking controller for photovoltaic system,are compared,including constant voltage tracking algorithm(CVT),perturbation and observation algorithm(P&O),incremental conductance algorithm(INC)and fuzzy logic control algorithm(FLC),and the performances of the abovealgorithms are summarized.By further analyzing the shortcomings of the traditional P&O algorithm,a piecewise variable step-size P&O algorithm is proposed to optimize the response speed and steady-state accuracy of the traditional algorithm.Then,the simulation model of the photovoltaic MPPT control system based on Boost converter circuit is built in MATLAB / Simulink,and the photovoltaic module,PWM modulation and MPPT control parts are built respectively according to each algorithm.The improved P&O Algorithm and other traditional algorithms are simulated and compared in the simulation environment,which proves that the algorithm is feasible and has practical significance.In addition to the piecewise variable-step P&O algorithm,a Soft computing-based P&O algorithm,that is,the P&O algorithm based on fuzzy logic control,is proposed to improve the performance of MPPT control by selecting the perturbation step through fuzzy logic controller.At the same time,the MPPT control module of the algorithm is built and simulated in the MATLAB / Simulink simulation environment to verify its feasibility.The comparison of three simulation results shows that the two improved algorithms are better than the traditional P&O algorithm in response speed,steady-state accuracy and so on.Finally,the article summarizes the full-text work,and makes an outlook for the follow-up work plan. |
