Deadbeat-Direct Torque and Flux Control of a Brushless Axial-Flux Magnetic-Geared Double-Rotor Machine for Power-Splitting HEVs

A deadbeat-direct torque and flux control (DB-DTFC) for brushless axial-flux magnetic-geared double-rotor machines (AMGDRMs) is presented in this article. The AMGDRM is employed as a power-splitting component in hybrid electric vehicles to enable speed decoupling between the internal combustion engine (ICE) and load. Since the rigid connection between the ICE and the drive train is replaced by the AMGDRM, fast torque control of the AMGDRM is required for the ICE speed regulation. Furthermore, the ICE torque contains abundant harmonics, inevitable sinusoidal components are introduced to the modulating rotor torque for torque balance, and further to the PM rotor torque owing to the magnetic-gear effect. Since both the PM rotor of the AMGDRM and the traction motor contribute to the hybrid electric system total torque output (i.e., torque coupling), the cascaded traction motor should compensate the PM rotor torque ripple actively to guarantee smooth total output torque. However, proportional-integral (PI) regulator suffers from limited bandwidth and thus could not realize accurate torque decoupling. Therefore, DB-DTFC, where torque and flux linkage are decoupled and respectively achieve their reference commands within two sampling periods, i.e., deadbeat responses, is proposed to enable a faster and more robust ICE speed control and accurate torque decoupling. The DB-DTFC law is derived and discrete-time close-loop current and flux linkage observers of the AMGDRM are developed. The proposed scheme and its superiorities are experimentally validated on an AMGDRM prototype test bench.