The Study On LVRT Technology Of Permanent Magnet Directly-driven Wind Turbine Based On Hybrid Energy Storage

With the continuous increase of energy demand and decrease of non-renewable energy sources,it is becoming an important part of sustainable development to Develop renewable energy.Wind power has been widely used because of its mature technology.With the increase of grid-connected wind power generation capacity,the mutual influence between wind power generation system and power grid becomes more and more important.Therefore,it is important to improve the low voltage ride-through capability of wind power system.Firstly,this paper introduces the composition,working principle and mathematical model of permanent magnet direct-drive wind turbines system,and the problem of large output power fluctuation and low voltage ride through capability.The characteristics of the storage battery and the super capacitor energy storage element are analyzed.By using the advantages of the energy storage elements,the hybrid energy storage system can be improved in the direct current side of the permanent magnet direct-drive wind turbines system,which can effectively improve the stability of the grid-connected wind power system and low voltage ride through capability.Secondly,According to the charging and discharging characteristics of each energy storage device,supercapacitor is preferentially charged and discharged.When the supercapacitor charge and discharge capacity is insufficient,Battery charging and discharging of hybrid energy storage device real-time control strategy,and limit power is set to overcome the harm to the energy storage device caused by excessive charging and discharging,the service life of the device extends.When the power grid is in normal operation,the smoothness of the grid-connected power of the wind power system is improved;when the power grid voltage sags,and a comprehensive control method of grid side converter is proposed.The wind power system provides reactive power to the power grid to accelerate the recovery of the power grid voltage and help to improve the low-voltage ride through capability of wind turbine.Then,the capacity allocation method of opportunity constrained programming is used to optimize the hybrid energy storage cost with the improved particle swarm optimization algorithm,which makes the energy storage cost and power quality determine the capacity of battery and super capacitor under the optimal constraint condition Configuration,and it has good practicality and economy.Finally,study on the protection measures of low voltage ride through protection of hybrid energy storage,the control method of grid side converter is improved,and the comprehensive protection scheme of hybrid energy storage of permanent magnet direct drive wind power system is established.A complete system simulation model is set up on the Matlab/Simulink simulation platform,and simulation research is carried out.The simulation results show that the permanent magnet direct-drive wind power system can effectively adjust the power grid demand power and smoothen the wind power fluctuation,and improve low-voltage ride through capability of the wind power system in the DC side parallel hybrid energy storage system.