STABILITY OF NONLINEAR CLOSED-LOOP CONTROL SYSTEMS FOR ELECTRIC DRIVE FREQUENCY CONVERTER-INDUCTION MOTOR

This paper presents possibility of research of stability of motion of the "Frequency converter - Induction motor" nonlinear feedback system in the MATLAB software. In the intended nonlinear system entering of the nonlinear link of limiting which entered into the linear system "Frequency converter - Induction motor", allows to reduce influence of disturbance on dynamics of system and possibility of changing form of frequency characteristics depending on the size of amplitude of a signal. Dynamics of the "Frequency converter - Induction motor" nonlinear feedback system is described and equivalent to system of the ordinary differential equations, on the basis of which the program was created, on MATLAB algorithmic language, provides visualization of solution of these equations on the phase plane. In the program the characteristic of the nonlinear link is described by two equations, taking into account the conditional operator of "if". Numerical integration of the differential equations is performed by Runge-Kutta method. Standard function of MATLAB algorithmic language odephas2 of the program of the solution of the differential equations is intended for plotting decision component in phase coordinates for two-dimensional process. By resulting data it is possible to determine stability of the "Frequency converter - Induction motor" nonlinear feedback system on the phase plane.