Research On Improved Photovoltaic MPPT Control Algorithm Based On Riccati Equation

Due to environmental pollution and energy consumption,solar energy has gradually become the focus of attention and research.Photovoltaic power generation is an important way to rationally use solar energy,but it still has the following shortcomings:(1)The output efficiency is low,and it is easily affected by the external environment.(2)Grid-connected links are prone to produce harmonic components,which affect power quality.In view of the above problems,this thesis takes photovoltaic grid-connected power generation system as the research object,and studies the photovoltaic system maximum power point tracking(MPPT)and grid-connected issues.First,the photovoltaic power generation system was analyzed,the circuit principle and topology of photovoltaic cells were studied in detail,and its simulation model was built through the Simulink platform to clarify its output characteristics.Aiming at the advantages and disadvantages of the DC/DC conversion circuit,the Boost step-up conversion circuit is designed to realize the maximum power tracking technology.Then,the typical MPPT algorithm is analyzed,and an improved variable-step-length conductance is proposed to solve the problems that the variable-step-length conductance increment method is likely to oscillate near the maximum power point during the tracking process and is greatly affected by external light intensity.In order to solve the under-damped oscillation of the Boost circuit caused by the external disturbance of the photovoltaic power generation system in the actual situation,it is proposed to apply the Riccati equation to the maximum power point tracking technology of the photovoltaic system,and the Riccati equation is calculated to make the photovoltaic system stable.The tracking performance of the proposed optimization algorithm is verified by simulation.Finally,the grid-connected control strategy of the photovoltaic MPPT system is studied,and the control strategy is discussed for the photovoltaic DC/AC inverter unit.After analyzing the classification and principle of photovoltaic inverters,the three-phase bridge-type grid-connected inverter structure is selected as the research object,and the voltage and current double closed-loop control method is selected in the subsequent grid-connected link.In order to prevent the generation of harmonic components,the grid-connected scheme of PI regulation and SVPWM control is introduced.The simulation results show that this method can maintain the grid connection with the unit power factor of the current and keep the harmonic injection at a low level.