Dynamics of an electric drive with a double-fed asynchronous machine under vector control

Abstract

The dynamic behavior of an electric drive with a double-fed asynchronous machine under vector control is considered. The functional diagram of an electric-drive vector-control system, a mathematical model of the power part, the algorithms of the controllers, and the results of mathematical simulation of the electric drive are given. The simulation was carried out under the following conditions. The model of the induction motor takes into account the electromagnetic and electromechanical transient processes and the main magnetic-circuit saturation. The models of the frequency converters are assumed to be ideal elements. The mathematical description of the model of the power part is based on the presentation of variables (voltages, currents, and flux linkages) in the form of algebraic vectors components of which are given in a rotating rectangular coordinate system. The algorithms of the control-system controllers were synthesized using the method of nonlinear multivariable systems of subordinate control with the possibility of minimization of the total power losses of the saturated motor at a variable magnetic flux. The determination of the electric-drive dynamic responses is given based on the results of the simulation of transient processes in the evolution of the torque and speed during the starting and speed-up of the motor and upon the application of a mechanical load and upon unloading. During this simulation, the behavior of the electric and electromagnetic variables of the motor was controlled. The results of the mathematical simulation that were obtained under the above-formulated conditions allowed us to draw the conclusion that an electric drive with a double-fed asynchronous machine with vector control makes it possible to obtain transients close to those typical of the systems with a subordinate regulation in direct-current electric drives and optimize the total losses under the conditions of a variable magnetic flux.