Research On Control Strategy Of Direct Drive Permanent Magnet Wind Power Converter System

In recent years,the continuous development of new energy technologies,people entering the era of energy Internet,wind power is one of them.With the development of wind power,offshore wind power generation and wind power systems that suitable for ultra-low wind speed are developing rapidly.And direct-drive wind power system has become a hot spot in many countries.In the wind power system,the control part determines the performance of the system,selecting a appropriate control strategy will make the system has a better performance.Firstly,the paper analyze the theory of direct-drive wind power system and establish the mathematic models of generator-side and grid-side converter.For the generator-side converter,the paper uses the vector control strategy to control the permanent magnet synchronous generator,and then add the sensorless-control algorithm.We study the sliding mode observer algorithm based on arctan and sliding mode observer algorithm based on PLL For the two algorithms,the paper establishes the MATLAB simulation model and analysis the performance of the system at steady state and dynamic state.In the grid-side converter,the paper studies the vector control algorithm based on the grid voltage orientation,and the direct power control algorithm based on grid voltage orientation,then builds the MATLAB simulation model.Because of the need of obtaining grid phase accurately,this paper analyzes the software PLL algorithm in detail,and studies the performance of PLL algorithm under single-synchronous coordinate system and double-synchronous coordinate system.The paper uses simulation tool to verify the performance of the PLL.when the phase mutation,voltage imbalance,grid voltage harmonic and grid voltage drop.Finally,we set up the experimental platform,and use the DSP28335 of TI Company to write the software program of power generation experiments and grid-connected experiments,and verify the control strategies of the generation side and the grid side.The paper verifies the sensorless algorithm on the low-power PMSM platform,and compares the two algorithms about obtaining the rotor position The experimental results show that under the condition of low speed,the algorithm can estimate the actual position of the rotor accurately.