Research On Harmonic Suppression Grid-Connected Inverter Of Photovoltaic Power Generation System

The global energy system is accelerating towards a green and low-carbon future.With the development of the speed and scale of renewable energy,a large proportion of renewable energy power systems are becoming a reality.However,due to the large amount of nonlinear load in the power grid,harmonic pollution will be brought about.The grid connected inverter can not only provide input power to the grid side,but also compensate for harmonic components,improve the utilization rate of new energy and improve power quality.on the two stage three phase photovoltaic power generation system,in-depth research on its maximum power tracking technology,grid-connected current control technology and harmonic detection technology are conducted.The main research contents are structured as follows:First,this paper studies the modeling of photovoltaic power generation system.Since the traditional constant step size perturbation observation method cannot guarantee the speed and steady state precision of the max power following at the same time,a new variable step size perturbation observation method is designed,the method can guarantee the speed and steady state precision of the max power following of photovoltaic system.At the same time,the normalized regulatory factors can be applied to different environmental conditions and have high application value.Secondly,the harmonic detection method based on the instantaneous reactive power theory is studied in detail in this thesis.In order to solve a hard nut to crack that the phase-locked loop in the traditional ip-iq harmonic detection method is difficult to meet requirements for accuracy when the power system has voltage distortion or high-order harmonics,an enhanced generalized integrator structure is proposed,and a phase-locked loop based on the improved generalized integrator is designed.On this basis,an enhanced ip-iq harmonic detection method is proposed to eliminate the influence of voltage distortion or higher harmonics in the input signal.The effectiveness of the method was verified by Matlab simulation.Then,for the sake of solve the problems of poor dynamic performance of traditional PI grid-connected current controllers and the difficulty of achieving high-order harmonics without error tracking,the MPC model predictive controller is introduced in this thesis,and the discrete mathematical models,predictive models and value functions are established to compensate The control delay of the reference current.Furthermore,the simulation models of traditional PI controller and MPC current controller are built to analyze the steady-state performance and dynamic performance of the current controller in different control modes.Finally,the enhanced ip-iq harmonic detection algorithm and MPC current controller are combined and applied to the grid connected PV inverter system module for power grid connection and harmonic current detection and suppression.The Matlab/Simulink toolbox is used to build a grid-connected inverter system simulation model.The simulation results verified the harmonic detection and suppression performance of the grid-connected inverter and the enhanced control strategy.