Stability Analysis of a Three-Phase Converter Controlled DC Motor Drive

Abstract

The design of the speed controller is important from the point of view of imparting desired transient and steady-state characteristic to the two quadrant converter controlled separately excited dc motor drive system. The poor design of the controller causes in losses and inefficient operation of the drive. Although many improved PI/PID design methods are proposed, such as root locus, Ziegler-Nichols (Z-N) methods etc., but they have shortcomings such as long testing time and limited control performance. To overcome this difficulty, we make use the theory of D-partition technique. Based on analytically characterizing the D-partition boundaries of the controller parameter space, necessary conditions of the maximum degree of stability are derived. The design of the controller and analysis of a converter controlled closed-loop dc motor drive is presented in this paper work. The effect of different factors like the time constant of proportional speed controller and the motor time constant on drive performance is analyzed. The D-partition technique is used to investigate the interaction of proportional speed time constant, amplifier gain and armature time constant on the stability of two quadrant converter-controlled closed loop separately excited dc motor drive. In this paper work, a procedure has been suggested to find the optimum value of the amplifier gain to give minimum settling time, which is the most important requirement of high performance drives or high fidelity drives. Using the D-partition technique, a comprehensive performance analysis of system design is carried out in this paper, using MATLAB environment.