Design And Simulation Study Of Two-Stage Photovoltaic Power Generation System

In the early 21 st century,China has made remarkable achievements in the research of distributed energy grid-connection.The new energy power generation represented by distributed photovoltaic power generation ranks first in the world in terms of installed capacity and generating capacity.This thesis compares and analyzes the advantages and disadvantages of single-stage photovoltaic power generation system and two-stage photovoltaic power generation system,determines the two-stage photovoltaic power generation system as the research object,adopts the modular design idea,Design and study the circuit parameters and control strategies related to the pre-stage BOOST circuit module of photovoltaic cells and the post-stage three-phase bridge inverter(DC/AC module)based on LCL filter,and simulate and analyze the designed two-stage photovoltaic power generation system in MATLAB/Simulink.The effectiveness of the two-stage photovoltaic power generation system and its control strategy is verified by simulation experiments.The perturbation observation method is selected as the maximum power tracking control algorithm of BOOST circuit,and the duty ratio is adjusted in real time to realize the real-time tracking of the voltage emitted by the photovoltaic panel,so as to achieve the maximum utilization of the electric energy emitted by the solar cell.Voltage regulator C2 is added to stabilize the voltage of the DC bus.In this thesis,I filter is used to adjust the AC power output by DC/AC module,and real-time control the waveform,amplitude and phase of the current output by DC/AC module.In this thesis,the control strategy of active damping to suppress resonance is determined.A double current closed-loop control strategy is adopted,which uses capacitor current as the inner control loop and grid-connected current as the outer control loop.PI controller is adopted for grid-connected current outer loop control and capacitor current inner loop control,and the voltage feedback link is moved forward to avoid the influence of grid voltage on grid-connected current waveform.The software phase-locked loop(PLL)is selected as the tool of frequency and phase locking for the two-stage photovoltaic power generation system to ensure that the grid-connected current is in the same frequency and phase as the current of the large grid.DC/AC module adopts vector control to reduce the harmonic loss of output current and improve the utilization rate of grid-connected voltage.