Research On Maximum Power Point Tracking Of PV System Under Partially Shaded Conditions

Photovoltaic power generation is a process that uses the photoelectric effect of photovoltaic cells to convert light energy into electrical energy.It is an important application for humans to use solar energy sources and is the most promising new energy technology.The difficulty of this application is how to ensure the photoelectric conversion efficiency and make the system run stably.A common method is to control the maximum power point tracking(MPPT)of the PV array.However,in actual situations,the photovoltaic array may have a mismatch effect in the case of uneven illumination,resulting in power loss or even burning of the battery.In order to avoid this phenomenon,a bypass diode should be connected in parallel across the photovoltaic cell assembly to share the excessive current,but the introduction of the bypass diode will change the electrical characteristics of the photovoltaic cell,causing the local output of the photovoltaic array to appear locally.The value affects the efficiency of MPPT control.To this end,this paper studies the maximum power point tracking control technology of photovoltaic power generation system under uneven illumination.The specific work includes:1.Firstly,the structure of the photovoltaic power generation system is briefly introduced,and the Boost boost circuit is determined as the DC converter of the photovoltaic power generation system MPPT circuit.On this basis,the mathematical model of photovoltaic cell was deduced and simulated,and the output characteristic curve of the photovoltaic array under uniform illumination was obtained.Then,based on the analysis of the equivalent impedance adjustment principle of photovoltaic array,several commonly used MPPTs were compared.The advantages and disadvantages of the tracking method are verified,and the problems of some methods and the effectiveness of the solution are verified by simulation.2.Secondly,the mathematical model of photovoltaic cells under non-uniform illumination conditions is derived.It is concluded that when the PV array is exposed to different degrees of illumination,its characteristic curve will show multi-knee shape and the characteristic curve will show multi-peak shape.Then a linear constraint function is given,which is used to re-set the working point to fall within the voltage range to which the global maximum power point belongs,and then use the operating point as the starting point to re-track to the PV array through the hysteresis comparison method.Maximum power.Finally,a simulation model is built to verify its feasibility.3.Then,in order to improve the output ripple of the MPPT controller,a switching inductor parallel-interleaved Boost circuit with high gain and low output ripple is presented.Based on the theoretical analysis of the switched inductor structure and the parallel staggered structure,the boost gain and output ripple of the two structures are derived respectively,and the advantages of the switched inductor parallel staggered Boost circuit are verified by simulation.4.Finally,a 5kW photovoltaic grid-connected inverter is designed.The MPPT algorithm is tested on this platform.The comparison of experiments demonstrates the efficiency of the proposed MPPT method under shadow illumination.