Abstract-An electrical variable transmission (EVT) can be used as a power splitting device in hybrid electrical vehicles. The EVT analyzed in this paper is a rotating field electrical machine having two concentric rotors. On the outer rotor, permanent magnets (PMs) are combined with a dcfield winding, being the first implementation of its kind. The magnetic field in the machine as well as the electromagnetic torque on both rotors are a function of the q-and d-axis currents of the stator and inner rotor, as well as the dc-field current. To describe and fully understand this multiple-input multiple-output machine, this paper gives an overview of the influence of the different current inputs on the flux linkage and torque on both rotors. Focus is given to the hybrid excitation in the d-axis by combining the dc-field current and the alternating currents. This has the advantage compared to other EVT topologies that unwanted stator torque can be avoided without stator d-axis current flux weakening. Results of the analysis are presented by means of the torque to current characteristics of a double rotor PM-assisted EVT, as well as the torque to current ratios. The machine characteristics are finally experimentally verified on a prototype machine.Index Terms-Electrical variable transmission (EVT), hybrid excitation, torque analysis.

Model based predictive control is a powerful control strategy to drive electrical machines. Conventional cascade PI(D)controllers are often used to control speed, torque and current. However, for low inertia machines, achieving a high performance and a wide speed range is far beyond the application conditions for which these controllers are designed for. Using two cascaded PI(D) controllers for speed/current control of a low inertia machine, changes in the speed set-point should be applied slowly in order to avoid stability problems. In this paper a model predictive control algorithm is proposed able to control the speed of a low inertia brushless DC machine with a high bandwidth and good disturbance rejection properties. The algorithm is implemented on a SPARTAN 3E 1600 FPGA board and experimental results verify the performance of the proposed algorithm.Index Terms-Model predictive control (MPC), permanent magnet brushless DC machine (BLDC machine), speed control, dynamic stiffness, field programmable gate arrays (FPGA). 0278-0046 (c)

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