Research On The Harmonic Characteristics Of Grid-connected Wind Power System And Its Suppression Strategy

With the development of wind power generation technology,the total installed capacity of wind power continues to increase.However,the operation and control of grid-connected wind power systems require a large number of power electronic devices to participate.In the course of their work,they inevitably generate harmonics.These harmonics could pose a threat to the normal work of electric power equipment and power grid.In order to ensure the safe and stable operation of the power system,it is significant to study the harmonic characteristics of the grid-connected wind power generation system.Based on this,the corresponding harmonics suppression strategies are taken to reduce the harm caused by the harmonics injected into the grid by the wind power systems,and the wind power industry can gain sustained development.In this paper,the global mainstream grid-connected DFIG-based and PMSG-based wind generation system are analyzed.The research is mainly about the harmonic characteristics of wind power systems under different operating conditions and the harmonic suppression effect of active power filter and passive power filter applied to wind power system is analyzed and compared.First of all,the mathematical models of each part are established on the basis of analysis of aerodynamic characteristics of wind turbine.Based on the four-component model of wind speed,three combined wind speed models are established in MATLAB,and the Maximum Power point Tracking is analyzed and simulated in MATLAB.Secondly,the structure and working principle of doubly-fed and direct-drive wind power generation system are expounded.The basic equations and mathematical models of doubly fed induction generator(DFIG)and permanent magnet synchronous generator(PMSG)are analyzed and deduced.This paper focuses on analyzing and constructing two vector control strategies for grid-connected operation of wind power system.Two detailed simulation models of wind power generation system for harmonic analysis are established using MATLAB,and the effectiveness of the control strategy is verified.Then,the influence of the three-phase converter circuit of wind power system and the working state of the wind power system on the harmonic characteristics of the system is explored.Using the wind power generation system model built in MATLAB,the harmonic characteristics of the system under different operating conditions are simulated and researched from two perspectives of the interior of wind farm and the power grid.The influence of wind speed,the type of wind,the type of wind turbines and power flow between wind turbines under different operating states on the system harmonics is summarized.Finally,the harmonic suppression performance of active and passive power filters applied to wind power system is compared and analyzed.One active power filter simulation models and four passive power filter simulation models are built using MATLAB.Taking the current of Point of Common Coupling(PCC)in wind power system,It is verified that the active power filter can compensate multiple harmonics in real time and the harmonic suppression performance for the wind power system is better compared to passive power filter.