Research On MPPT And Grid-connection Control Strategy In Photovoltaic Power Generation System

Energy is the source of power and material basis for the advancement of mankind.With the continuous development of society,human beings are using more and more traditional energy sources,which has created a shortage of energy and damage to the living environment,so it is especially important to find new renewable energy sources.Solar energy has been widely used because of its renewable and non-polluting advantages.In this context,the research in this paper is based on the photovoltaic power generation system and focuses on the maximum power point tracking technology and grid-connected control strategy.Firstly,the working principle and mathematical model of PV cell are analyzed,and the simulation model of PV cell is built in MATALAB/Simulink to simulate the output characteristic curve of PV cell under various light intensities and temperatures.Considering that the PV array will have partial shading,the output characteristic curves of the PV array under uniform illumination and partial shading are simulated.Secondly,to address the contradiction between the tracking performance and step size of the traditional maximum power point tracking technique of the disturbance observation method and the conductivity increment method,an improvement strategy of variable step size is proposed,and the superiority of the tracking performance of the improved algorithm is verified through simulation comparison.For the shortage of speed and accuracy of the particle swarm algorithm in tracking the maximum power point under local shadowing conditions,the improvement strategy of dynamically adjusting the inertia weight and learning factor of the particle swarm algorithm is proposed,and the results show that the improved particle swarm algorithm tracks the maximum power point in shorter time and higher output power through simulation comparison,which verifies the superiority of the improved particle swarm algorithm and improves the photovoltaic The results show that the improved particle swarm algorithm tracks the maximum power point with shorter time and higher output power.The mathematical model of LCL grid-connected PV inverter in different coordinate systems is analyzed again,and the parameters of LCL filter are designed.For the problem of inherent resonance spikes in LCL filter,which affects the stability of grid-connected PV system,the active damping control with capacitor current feedback is adopted to suppress the resonance spikes and improve the stability of the system.Finally,for the problem that PI control of three-phase PV grid-connected inverter control strategy has good dynamic performance and poor harmonic suppression ability while repetition control has strong harmonic suppression ability but insufficient dynamic performance,PI+repetition composite control strategy is adopted to realize the complementarity between two control strategies,and the simulation comparison in MATLAB/Simulink shows that PI+repetition composite The results show that the PI+repeat composite control strategy is better than the single PI control,and the total harmonic distortion rate of the incoming current is reduced from 4.98% to 2.44%,and the harmonics in the grid are effectively suppressed,which verifies the effectiveness of PI+repeat composite control and the superiority of the harmonic suppression ability,and improves the grid-connected power quality of the PV power generation system.Figure [75] Table [6] Reference [72]...