Modeling And Simulation Of Tidal Current Power Generation System Considering Velocity And LVRT

The problems caused by energy depletion and environmental degradation are becoming more and more obvious,and the development of renewable energy has attracted more and more attention in recent years.Tidal current energy,as a renewable energy,has been paid more and more attention.This paper aims to establish a tidal current generation system,simulate the tidal velocity,and then take the low voltage ride through(LVRT)problem into account.Finally,a tidal current generation system considering the tidal velocity and LVRT is established and verified by simulation.Firstly,we improve the DFIG,introduce the turbine,transmission device,generator,converter and so on of the tidal current generation system,carry out the mathematical modeling,then carry out the simulation verification of different tidal velocity in the MATLAB / Simulink system.The experimental results show the effectiveness and stability of the model.Secondly,for tidal velocity,kernel density estimation with non parametric is adopted,and the seasonal and time period factors are taken into account.A segmented sampling method considering season and time sequence is proposed.The probability model of tidal velocity is established.The velocity data is obtained by probability sampling,and the probability model suitable for tidal velocity is found.At the same time,the typical daily velocity curves of spring and neap tides in different seasons are obtained by clustering method,and the simulation results in the model prove the applicability of the power generation model in the real velocity environment.Finally,on the issue of LVRT,in order to prevent crew being separated from the grid during the process of voltage drop,this paper proposes a control strategy combining hardware and software protection.Crowbar is used in hardware protection and virtual resistance is used in software protection.However,crowbar has some disadvantages.When it is put into operation,the doubly fed machine will absorb a lot of reactive power,which makes the voltage recovery slow or even lower.Therefore,we consider the use of virtual resistance to overcome the shortcomings of crowbar,but the virtual resistance can not effectively suppress the rotor side over-current when the voltage sag is deep.Therefore,this paper proposes a control strategy combining crowbar and virtual resistance,which determines the switching of the two protections according to the degree of voltage sag.