| With the development of power electronics in the direction of efficiency and systemization,this has led to an order of magnitude increase in the amount of man-made electromagnetic energy generated in space.Electromagnetic noise interferes other devices or systems through circuit connections or space,resulting in more and more complex electromagnetic environment.To ensure normal operation of the system itself or other electronic devices,it is essential to reduce the electromagnetic noise generated and emitted in this electromagnetic environment,as well as improving the suppression technology of electromagnetic interference.In this thesis,a military wind turbine is used as the object of research to analyze,model and suppress electromagnetic interference from it.The main points of this thesis are as follows:(1)Analysis of the principle of electromagnetic interference from wind turbine drive systems.The first step is to fully understand the composition structure and working mechanism of the wind turbine,which is described as HPWM-LON.Then,according to the concept of EMI,the source and propagation path are theoretically studied.Depending on the propagation path,conduction and radiation are analyzed separately.A detailed path analysis of the conducted disturbance currents is carried out by using a fan circuit principle.Finally,based on the radiation principle of very small dipoles,the electromagnetic radiation intensity of the wire in the space region is analyzed.(2)Modeling of principal electronic components in the drive system.First,the SPICE model is used to describe the electrical characteristics of MOSFET.The model parameters and their coupling equations are studied in detail.Then the SPICE model of the MOSFET NCEP0160 AG is built based on Si MOSFET core type.The effect of the static characteristics parameters in the SPICE model on the electrical characteristics curve simulated by the SPICE model simulation is analyzed,then the parameters are optimized by using the Optimization.Finally,the SPICE model of the principal components is obtained by writing the model parameters into the file according to SPICE syntax rules.(3)Modeling,simulation and testing of wind turbines in electromagnetic interference.The EMI experiment platform for wind turbines is built according to EMI experimental test standards.The test methods and experimental equipment for the experiment are introduced.Then,the conducted interference model and the cable radiation interference model for the wind turbine drive system are developed separately.By comparing model simulations and experiments,the spike points,amplitudes and curve trends of the wind turbine’s electromagnetic interference results are basically the same,which lays the foundation for the verification of the interference suppression method later on.(4)Electromagnetic interference suppression for wind turbines.EMI filters and shielded wires are used in this article to suppress electromagnetic interference.Firstly,the circuit structure of the filter is studied.The common-mode differential-mode combined filter is used to suppress electromagnetic interference.Based on the cutoff frequency of the single-stage LC filter,The component parameters of the filter are obtained by parameter optimization using the Optimization tool.Finally,EMI filters are fabricated for the experimental verification of electromagnetic interference in wind turbines.The experimental results show that electromagnetic interference is effectively suppressed by the addition of EMI filters.The amplitude of voltage conduction interference decreased by 25 d BμV on average.The current conduction interference decreased by 15 d BμA in the frequency band 0.0005～0.01 MHz.The radiated emission amplitude is reduced by at least 10 d BμV/m at a frequency of 0.5～10 MHz.And the experimental result is in general agreement with the model simulation results.The principle of shielding wire to suppress radiation emission is investigated.Model simulation results show that the shielded wire has a stronger shielding effect on the radiated electric field than a single core wire. |
