Fuzzy logic based Analysis of Steady State Stability of a CSI Fed Synchronous Motor Drive System with Damper Windings Included

Abstract

Steady state stability criteria of A.C. drives play a dominant role for making the drive system practically successful. Generally such steady state stability analysis (SSSA) is done using small perturbation model. This study presents a detailed steady state stability analysis (SSSA) criterion based on small perturbation model of a fuzzy based current source inverter fed synchronous motor (CSIFSM) drive system taking d-axis and q-axis damper winding into account using fuzzy set theory. The modeling also clearly shows that even at no load the system satisfies steady state stability analysis (SSSA) criterion. The current source inverter fed synchronous motor (CSIFSM) has been treated as a five coil primitive machine model using the concept of generalized theory of electrical machines. Using the concept of Park"s transformation the armature current in d-q model has been represented by suitable equations as a function of armature current magnitude in phase model (I S ) and the field angle (β). As the system under consideration is basically a current source inverter fed system, I S has been considered as a constant and as a consequence the field angle (β) finally appears as a control variable. Finally the transfer function Δβ (s)/ΔT L (s) have been formulated; where Δβ (s) and ΔT L (s) represent small change in transformed field angle and load torque, respectively. A fuzzy logic system is developed for steady state stability study of CSI fed Synchronous Motor (CSIFSM) and discussed for its better performance. The analysis concludes that the absence of damper winding leads to instability of the machine system.