Low Switching Frequency Deadbeat-Direct Torque and Flux Control of Wound Field Synchronous Machines

Enhancements to the deadbeat-direct torque and flux control (DB-DTFC) of wound field synchronous machines (WFSMs) are proposed allowing for operation at low switching frequency to fundamental frequency ratios. Discrete time current and flux linkage observers which properly model WFSM d-q and d-f cross-coupling are formed using a Taylor series approximated sampled Laplace approach. The affect of the Taylor series order on the discretization error and model accuracy is examined. The torque curve to determine the inverter voltage commands is derived from the flux linkage model coefficients. Experimental comparison of the WFSM torque response is made between the classical DB-DTFC with current and flux observers formed using a z-transform approach and the torque line derived from a forward Euler method and the newly proposed observers and torque curve.