The Theory And Experimental Research On A Novel Method Of Variable Frequency Speed Control System

AC induction motor has coupled parameters and strong non-linear characteristics. Thecurrent high-performance induction motor speed control methods are vector control anddirect torque control. Vector control decouples the induction motor through the coordinatetransformation method; direct torque control directs control the motor torque by switchingtracking.This paper presents a linear control method of nonlinear system. This methodachieved decoupling control of the nonlinear coupling object by equivalent to analternative model through the establishment of the state observer compensation technology.This method does not need to know the exact mathematical model of controlled object. Thesystem design is completely within linear system theory, avoiding the complex non-linearsystem design. For specific types of nonlinear systems, simulation models are designed,simulation results is obtained.Combining linear control method of nonlinear system and variable frequency controltechnology produce a new AC drive solution. This solution achieved the torque and fluxdecoupling within the linear range. It does not need coordinate transformation, because ofthat, a new method for the flux and torque detection algorithm is designed.In order to compare with the new method speed control, vector control is alsodesigned. To use of voltage source inverter vector control system, the torque voltage iscoupling with the excitation voltage. This paper gives a decoupling scheme, and designedspeed, torque and flux regulator with integral separation algorithm. SVPWM technique isalso used to control inverter, because of its high utilization of output DC voltage.This paper designed a voltage source AC-DC-AC speed control system hardware,including the main circuit and a high-speed drive module. To prevent damage of the maincircuit, over-current protection using hardware, through experiments the protective effecthas been verified. The voltage, current, speed and other peripheral circuits based on DSP isalso designed. And program modules of vector control are written with CCS compiler.Before the experiment, the new method control and vector control simulationplatforms are seted up based on MATLAB/Simulink. All the parameters of the two systemsand modules are simulated, and simulation results are given. Simulation and experimentalresults show that using rotor flux oriented vector control system with voltage-type invertercan achieve good static and dynamic performance. The new method of frequency controlsystem can also achieves a decoupling of torque and flux, having ideal performance. So thenew method control provides a new solution with valuable research value and broadapplication prospects.