Research On Main Converter Of Low Wind Speed Maglev Vertical Axis Wind Turbine

China has abundant resources of low-wind-speed wind energy.With the development of renewable energy and the maturity of wind power generation technology,low-wind-speed wind power has become one of the focuses of future wind power development.The existing wind turbines have the problems of large starting resistance torque and low wind energy utilization,which are hard to meet the demand of low-wind-speed starting.Therefore,our team proposes a low-wind-speed maglev vertical-axis wind power generation system.The system consists of wind turbine,main generator(permanent magnet direct drive generator,PMSG),maglev system and main converters(including machine-side converter MSC and grid-side converter GSC)etc.This paper focuses on the main converters.In order to realize low-wind-speed power generation,the power consumption of main converters must be minimum.In view of the stator current harmonics of the main generator can cause generator body's vibration,threatening the stable operation of the maglev system.Thus,to ensure the stability of the maglev system,the AC side current harmonic content of the generator side converter(that is,the stator current of the main generator)must be minimum.To this end,this paper has carried out the following research:First,the development status of the topology,control strategy and filters of main converters in low-wind-speed maglev vertical axis wind power generation system are studied and analyzed.Second,aiming at the proposed low-wind-speed maglev vertical-axis wind power generation system,the mathematical models of its wind turbine,PMSG and main converters are established,and the working principles of each part are analyzed.The machine-side converter(MSC)adopts the zero d-axis current(ZDC)control strategy,and the grid-side converter(GSC)adopts the grid voltage-oriented control strategy.The simulation experiment is carried out on the MATLAB/Simulink simulation platform to verify the control effect of the proposed control strategy on the current harmonics.The simulation results show that the harmonic components of the machine-side and grid-side currents are both within the allowable range of the distortion rate,which verifies the effectiveness of the proposed control strategy.Third,the model predictive control strategy is proposed for the MSC.Model predictive control(MPC)has less switching times,which can reduce the switching loss and improve response speed.However,low switching times will increase current harmonics and loss of the converters to some extent.In order to improve the response speed,this paper proposes a dual-loop control strategy with the current inner loop and the speed outer loop,and the former adopts a finite set model predictive control strategy,the latter adopts a PI controller.The simulation analysis results show that the proposed MPC control strategy can improve the response speed,and ensure the harmonic component of the stator current within the allowable range specified by the relevant standard,and the less power consumption compared with the ZDC control strategy.Fourth,in order to further reduce the power consumption of the main converters and the total harmonic distortion rate(THD)of the grid-connected current,an improved active damping control strategy of the GSC is proposed.The simulation results show that the THD of the grid-connected current and power consumption are reduced,and the required inductance is also reduced,which verify the effectiveness of the proposed control strategy.Finally,in order to study the performance of the control strategies of the main converters,the experimental platform for GSC is built respectively.The hardware design,welding and connection of each link are completed in turn.After debugging,the experiment platform based on d SPACE is built,and experiment with GSC is carried out.The results show that the THD of the grid-connected current meets the requirements of the national standard under the proposed control strategy.