Design Of Single-phase Photovoltaic Inverter Based On Double Closed-loop PI And Quasi-PR Control

As the most promising clean energy in the 21 st century,solar energy has received widespread attention in recent years.Photovoltaic power generation technology is becoming more and more mature,and its development is getting better and better.As the core of photovoltaic power generation technology,inverter plays an important role in the whole system,and its good performance can greatly improve the efficiency of the entire power generation system.Therefore,it is very important to study the control strategy of the inverter.However,the traditional PID control strategy does not achieve static-free regulation of the inverter output voltage.Therefore,this paper proposes a double closed-loop PI and quasi-PR control method,which is controlled by a PI controller for the current inner loop and a quasi-PR controller for the voltage outer loop.And through the simulation of MATLAB/Simulink simulation platform,the experimental prototype is designed with DSP28335 as the core.The specific contents include the following parts:Firstly,the main circuit model of single-phase photovoltaic inverter is designed.The model mainly includes four parts,namely photovoltaic part,DC boost part,inverter part and filtering part.A mathematical model is built for the unipolar SPWM-controlled inverter,and the model is simplified.In the photovoltaic part,the maximum power tracking(MPPT)is selected by the disturbance observation method.In order to improve the susceptibility of the method,the instantaneous power is changed into the average power step mode to improve the stability.Design a BOOST boost circuit in the DC boost section.The inverter part adopts single-phase full-bridge inverter circuit,and the control part adopts a double closed-loop control model combining current inner loop and capacitor voltage outer loop combined with inductor current and disturbance current feedforward.On this basis,the LC filter is designed.The current inner loop adopts the PI controller,and the voltage outer loop adopts the quasi-PR controller to compare and analyze the characteristics of PI,PR and quasi-PR.Then,a simulation experiment of single-phase photovoltaic inverter was carried out.Based on the MATLAB/Simulink simulation platform,the photovoltaic panel simulation module,the maximum power tracking module of the photovoltaic panel,the DC-AC module,the SPWM control module,the quasi-proportional resonance controller module(quasi-PR module)and the LC filter module are built.After setting the parameters that meet the requirements,the simulation waveforms of each module are obtained,and the verification accuracy and feasibility are verified.The simulation experiments of half load,full load and resistive load are carried out.The simulation waveforms under two different control strategies,PR and quasi PR,are compared.The dynamic characteristics of the double closed loop PI and quasi PR control strategy are verified by FFT analysis.Finally,the hardware design,software design and experimental prototype experiment of singlephase PV inverter are carried out.The BOOST boost circuit,DC-AC inverter circuit,clock circuit,reset circuit,AD sampling circuit and power circuit part are designed with DSP28335 as the core.The software part uses C language as the programming language,and writes MPPT control algorithm and SPWM control algorithm respectively.The design of single-phase photovoltaic inverter is completed.The prototype experiment was carried out in the experimental platform of the power electronics laboratory for prototype construction,debugging and experimental data collection.The simulation and experimental results show that the double-closed-loop PI and quasi-PR control strategies can achieve no-difference adjustment in the design of single-phase PV inverters.The quasi-PR controller achieves infinite gain and wide bandwidth at the fundamental frequency.The designed single-phase PV inverter has good performance and lays a solid foundation for the development of photovoltaic power generation.