The Research Of The High Voltage Ride Through Technologies Of PMSG

In recent years,as people pay much attention to environmental problems and sustainable development,wind power as a pollution-free,inexhaustible and clean energy has made rapid progress.However,due to the inherent randomness and intermittent influence of wind power,the impact of large-scale wind power grid connected to the grid can not be underestimated.Compared to the doubly fed wind turbine,PMSG,eliminating the gearbox in the structure,and connecting with the power grid by the voltage source converter based HVDC,has the advantages of high reliable technology and economic benefits.Compared with doubly fed wind turbine,direct drive wind turbines have saved the gearbox,which it not only improves the efficiency,but also reduces the cost of operation and maintenance.For now,the domestic and foreign scholars mainly are concerned on the problem of the low voltage ride through technology and the transient analysis of the wind turbine by the voltage drop.However,in the grid voltage swell,there are insufficient attention to the research of high voltage ride through.Many accidents of high voltage ride through show that the voltage swell fault is more serious,compared harm to voltage sags,so the wind turbine high voltage off network fault is imperative.In this paper,the 1.5MW direct drive wind turbine is taken as the research object,and the simulation model is established in Matlab/Simulink.The main work of this article is as follows:Firstly,the mathematical model of permanent magnet direct-drive wind power generation system and the grid side converter have been analyzed in detailed.The whole control strategy of generator-side converter control and grid-side converter control was studied.The 1.5MW unit simulation model of wind power has laid a solid foundation.Secondly,the key issue in the HVRT is how to consume excess energy during the fault after transient analysis,and then put forward the application of Crowbar circuit and super capacitor circuit through high voltage ride through.Based on this,an integrated control based on ultra-capacitor energy storage circuit and reactive current is proposed,and the correctness of the scheme is verified by simulation.Thirdly,the control performance of grid side inverter for wind turbine during HVRT is studied.The research shows that the active current of the grid connected inverter may be limited or even out of control during the fault.Once the wind turbine is out of control,the uncontrollability of grid side inverter will reverse the flow and lead to the over-voltage or over-current of the DC side.According to the capacity limitation of grid connected inverter and the vector relationship between grid voltage and grid side inverter voltage and current,there are three kinds of situations.Based on this,a scheme for improving the reference value of DC bus voltage and providing reactive current is proposed.In order to prove the effectiveness of the proposed scheme,the scheme is compared with the traditional control,and the effectiveness of the control strategy is proved by the simulation of the Matlab/Simulink platform.