Deadbeat-Direct Torque and Flux Control for Wound Field Synchronous Machines

Abstract

This paper presents a deadbeat-direct torque and flux controller for wound field synchronous machines (WFSMs) without damper/amortisseur windings. Compared to induction machines (IMs) or interior permanent magnet synchronous machines (IPMSMs), WFSMs have an additional degree of freedom through variable field excitation. Discrete time current and flux linkage observers are derived, which model the dynamics and cross coupling introduced by the variable field excitation. The variable field excitation also allows the torque line for the desired change in torque to be shifted on a sample by sample basis compared to IMs or IPMSMs where the torque line is static. This provides the opportunity to actively distribute the transient torque between the rotor and stator windings. A field flux linkage command is derived to achieve unity displacement power factor in the steady state. Experimental results are presented to demonstrate decoupled torque and flux linkage control.