Research On Control Strategy Of A New Type Of Direct-drive AC Excitation Wind Power Generation System

In order to alleviate energy crisis and solve environmental pollution,new energy is increasingly developed and utilized by all countries in the world.Wind energy has many advantages,such as great development potential,clean and clean,and so on,it has became the most large-scale and commercialized development and application of new energy.In recent years,wind power generation technology has continuously been improved.Constant speed constant frequency(CSCF)power generation system is replaced by variable speed constant frequency(VSCF)wind power generation system because of its high efficiency,good stability and easy grid-connected operation.The doubly-fed wind power generation system and the direct-drive permanent magnet wind power generation system are the two most used systems in the variable speed constant frequency wind power generation system.Based on the analysis of the structure characteristics of these two kinds of system and its performance advantages and disadvantages,a new direct-drive AC excitation wind power system is introduced in this paper,the novel wind power system has the wide speed range maximum utilization of wind energy,high reliability of low voltage ride through capability,high system reliability,the new type of direct-drive AC excitation wind power generation system will have more advantages in the future.A mathematical model of wind turbine and new direct-drive AC excitation generator under various coordinates is derived.Aiming at the two most concerned problems such as grid-connected and maximum wind power point tracking(MPPT)in wind power system,the principle is introduced in detail,and a control strategy based on vector control is proposed.The generator-side converter and grid-side converter are double PWM converters,stator voltage oriented vector control is used in the generator-side converter,grid voltage oriented vector control is adopted in the grid-side converter,they are coordinately controlled to realize the DC bus voltage stability,active power and reactive power decoupling,adjustable power factor.Stator flux oriented vector control is adopted in the excitation converter.In the grid-connected control process,the stator no-load voltage is controlled by controlling the excitation current to ensure the reliable operation of the generator-side PWM rectifier and realize the grid-connected operation;In the MPPT control process,the generator speed is controlled by controlling the excitation current to achieve the maximum wind energy tracking.Besides,the control strategy is simulated and analyzed by using Simlink module of Matlab,the simulation results show that: the system has good dynamic and static performance when the wind speed changes in a large range,grid-connected operation and maximum power point tracking can be realized.The feasibility and effectiveness of the control strategy are verified.The hardware and software of grid-side converter control system is designed.In the hardware circuit,main circuit and control circuit are mainly designed,the software is designed based on DSP28335 controller.At last,the control system is verified by experiment,the experimental results show that the waveform is better and accord with the proposed control strategy,the control strategy of grid-side converter and the correctness of designed control system are verified.