Study Of EDFND AC Speed Regulating System And Its Parametric Robustness

AC speed regulation has been greatly valued,and widely applied,because of its excellent speed-regulating performance,big power factor and high energy efficiency.In this thesis,the method Equivalent Drift Feedforward Non-linear Decoupling(EDFND)is applied to variable-frequency speed control system.And a comparative study is undertaken between this system and the traditional vector control system(output current controlled inverter is oriented by rotor flux linkage).On one hand,the research status of mainstream frequency conversion schemes,such as vector control technology,direct torque control technology and so on,is analyzed in this thesis.On the other hand,the background and significance of studying EDFND frequency control system are elaborated.Further more,the ideas and characteristics of EDFND method and its research courses while been applied to frequency conversion are also introduced.Particularly,the thesis introduces the theory of how output current controlled inverter is oriented by rotor flux,derivates the system control equation and accomplishes system dynamic design.Also,by adopting the bilinear transformation method,the vector control system is processed with the discrete way.Then,the recursive expression for the system control is derivated.This thesis introduces the principle of EDFND method,and applies it to control system of frequency conversion and dynamic decoupling.The design process of this system is explained in detail and the bilinear transformation method is adopted to discrete the system.In view of the existed system problem of inefficient decoupling in the intense dynamic progress,feedforward compensation scheme is put forward.After that,a comparative robustness research is made between above mentioned system and the rotor flux oriented control system for output current controlled inverter.The hardware platform of variable frequency speed regulation system is introduced,the controller's internal resources is allocated and the software structure including system function layout,the flow chart of the main function and interrupt service program flow chart is designed in this thesis.Detection and processing algorithms of several key parameters in the software system is introduced detailed,Including the line voltage line-to-line current sampling and sampling value filtering algorithm and three-phase coordinate system(different from in two-phase coordinate system)SVPWM algorithm,speed detecting algorithm and flux detection algorithm.To accomplish such a comparative study,firstly undertake the open-loop experiment and observe the waveform of key physical parameter,so that preparation is well made for close-loop experiment.Secondly,finish no-load and load closed loop experiments for the two systems respectively.The experiment verifies that the control effect of EDFND frequency conversion system is as remarkable as that of the vector control system.However,the former is easier than the latter,as it does not need accurate mathematical model of the controlled system as well as the coordinate transformation.The EDFND method,independent of accurate mathematical model of AC motor and coordinate transformation,facilitates the project implementation and provides a new train of thought for AC speed regulation,This study has the precious research value and broad application prospects.