Research On Single-Phase Photovoltaic Grid-Connected System Based On Improved Quasi-Z Source Inverter

With the progress of Industry 5.0,the development and utilization of renewable energy in the world has reached new heights.Among them,solar energy has attracted much attention due to its advantages of clean and pollution-free,abundant storage and high safety factor,and it has quickly become a global energy source.One of the effective ways of scarcity,therefore,the update of photovoltaic power generation technology is the general trend.Photovoltaic cell array,as an important unit of photoelectric conversion,its stability and conversion efficiency are crucial,among which the maximum power point tracking control technology(MPPT)can well control the working process of photovoltaic cells,while the traditional MPPT algorithm is at maximum power.In the point tracking process,there are problems of insufficient stability and slow response;grid-connected inverters,as DC/AC inverter units,play a key role in energy conversion and transmission,while Z-source/quasi-Z source inverse(ZSI/Q-ZSI)overcomes the shortcomings of the traditional voltage/current type inverter and realizes the single-stage buck-boost function.Although it also has shortcomings,it still has high research value.To this end,the article focuses on Q-ZSI’s single-phase photovoltaic grid-connected power generation system,mainly for the low efficiency,poor stability of the photovoltaic cell in the photoelectric conversion process,and the excessive capacitance voltage stress in the Q-ZSI topology.The problem is to make improvements to the MPPT control algorithm and topology.The article first introduces the classification of photovoltaic power generation system,selects the grid-connected photovoltaic power generation system as the research object of this paper,analyzes the output characteristics of photovoltaic cells,studies the MPPT control algorithm of photovoltaic cells,and determines the P&O algorithm with hysteresis control.Then,the topology of Q-ZSI is improved to reduce the voltage stress of the capacitor in the quasi-Z source network.Finally,the voltage-current dual-loop control strategy and the AFD islanding detection method based on positive feedback(AFDPF)are adopted to realize the single-phase grid connection of the improved Q-ZSI-1 and detect the islanding effect generated in the grid connection.Based on the above theoretical analysis and design,the traditional perturbation observation method(P&O),conductance increment method(INC)and MPPT simulation model with hysteresis control P&O algorithm are built by Matlab/Simulink simulation software to analyze the simulation waveform.The advantages of hysteresis control P&O algorithm in tracking stability and response speed are verified.The traditional Q-ZSI and improved Q-ZSI open-loop control simulation model are built,the simulation waveform is analyzed and the improved topology is verified.The advantages of reducing the capacitive stress;constructing the improved Q-ZSI-1single-phase grid-connected model and islanding detection model,analyzing the simulation waveform and verifying the feasibility of the grid-connected system and the effectiveness of the islanding detection.Figure[79] Table[4] Reference[67].