Integrated Field and Armature Current Control Strategy for Variable Flux Reluctance Machine Using Open Winding

This paper proposes an integrated field and armature current control strategy for a variable flux reluctance machine (VFRM) with an open-winding topology. By using an open-winding inverter, the field and armature currents can be injected into a single coil as a sinusoidal current biased by the dc offset rather than the separated field and armature windings. The integrated current control can reduce the copper loss to half and extend the operating speed range owing to the reduction in the winding resistance. In order to utilize the zero-sequence current as a field current, a zero-vector modification technique is proposed, in which the switching-on time of the zero vectors is modified to generate the constant zero-sequence voltage between two inverters. The proposed scheme is implemented in a synchronous dq0-axis frame with space vector modulation. For the validation of the proposed method, a machine model of the VFRM is developed and implemented in MATLAB/Simulink. The simulation and experimental results verify that the proposed strategy can effectively reduce the copper loss and extend the operating speed range.