Research On PV Grid-Connected System With Power Quality Conditioner

The photovoltaic grid-connected system with power quality adjustment function is a device with photovoltaic grid-connected and power quality comprehensive management functions,which realizes photovoltaic grid-connected,current harmonic control and voltage compensation.This thesis mainly studies the three aspects of maximum power tracking algorithm,current control technology and system power allocation.In order to realize the problem of Maximum Power Point Tracking(MPPT)in photovoltaic grid-connected systems,this thesis first analyzes the mathematical model of photovoltaic cells and studies the output characteristics of photovoltaic cells in series and parallel;in view of the output characteristics of photovoltaic systems and the defects of traditional observation disturbance algorithm,this thesis proposes an improved observation disturbance method based on fuzzy neural network,and adopts K-means hierarchical clustering to optimize the neural network;theoretical analysis and MATLAB simulation verification show that the improved MPPT algorithm can quickly track the voltage when the photovoltaic system receives light changes and reduce power fluctuations.In order to realize the photovoltaic grid connection and power quality management functions,this thesis designs the quasi-PR current controller to enhance the gain of the fundamental frequency of the system,this thesis also improves the first-order generalized integrator to achieve high gain of the specified subharmonics and reduce the impact of grid frequency fluctuations;Considering that the resonance spike of the LCL filter affects the stability of the system,this thesis constructs the equivalent capacitor current feedback by the method of multi-state variable feedback and highpass filter,and designs the gain and cut-off frequency of the high-pass filter;this thesis also proposes an algorithm to coordinate the system power of the series converter and the parallel converter in combination with the voltage compensation method,the series device quickly compensates and reduces the power taken by the parallel device when the grid voltage changes.This thesis designs the inverter filter parameters and DC voltage stabilization capacitor parameter,and verifies the control methods through MATLAB simulation and RTLAB experiments.The experimental results show that the photovoltaic gridconnected system with power quality adjustment function is effective and feasible.There are 67 figures,3 charts,and 87 references in the thesis.