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As an enhancement of a predictive direct torque control (PDTC) scheme for synchronous reluctance machines (SynRMs), an encoderless PDTC scheme that is able to operate at very low and zero speeds is introduced in this paper. At very low speeds, the angular position of the rotor can be estimated by injecting test voltage signals (TVSs) to detect the spatial orientations of existing position-dependent rotor anisotropies. The TVS produces transient stator current changes, so that stator current derivatives can be estimated in a digital way. In a SynRM, the stator current derivatives contain useful information that can be used to estimate the angular position of the rotor. The obtained information is processed by means of a quadrature phase-locked loop observer to extract the angular position of the rotor without detriments in phase and frequency. Following this strategy, no extra hardware, special current transducers, or connections are needed in comparison with a standard drive with an encoder. Based on the proposed strategy, an encoderless PDTC scheme for SynRMs is implemented. Experimental results using a digital signal processor and a field-programmable gate array embedded in the same board verify the effectiveness of the proposed control scheme. Index Terms--Digital signal processor, magnetic cross saturation, predictive control, sensorless control, synchronous reluctance machine (SynRM), torque control.

A predictive torque and flux control algorithm for the synchronous reluctance machine is presented in this paper. The algorithm realizes a voltage space phasor preselection, followed by the computation of the switching instants for the optimum switching space phasor, with the advantages of inherently constant switching frequency and time equidistant implementation on a DSP-based system. The criteria on how to choose the appropriate voltage space phasor depend on the state of the machine and the deviations of torque and flux at the end of the cycle. In order to obtain an appropriate model of the machine, it has been developed on a d-q frame of coordinates attached to the rotor and takes into account the magnetic saturation in both d-q axes and the cross-saturation phenomenon between both axes. Therefore, high-performance torque control is achieved, and the torque ripple is reduced. Simulated and experimental results using a DSP/field-programmable-gate-array-based control and a commercially available machine show the validity of the proposed control scheme. Index Terms--Magnetic cross saturation, predictive control, synchronous reluctance machine (SyncRel), torque control.

This paper presents an improved model predictive torque control (MPTC) scheme for a permanent magnet synchronous machine (PMSM). In conventional finite set model predictive control (FS-MPC), the optimal voltage space vector (VSV) is selected for application in the voltage source inverter (VSI) by the evaluation and minimisation of a cost function; however, the application of a single VSV in the whole control cycle leads to a relatively high torque ripple and a high sampling time is necessary to overcome this issue. In order to reduce these shortcomings without sacrificing torque reaction performance, a modified MPTC is proposed. First, in order to reduce the computational burden, a switching table is introduced for a reduction in the selection of the possible VSVs; further, to reduce the torque ripple, the duty cycle optimisation of a subset of VSVs available from the VSI is performed. The conventional FS-MPC and the proposed control scheme are implemented using a field programmable gate array, and are experimentally compared in terms of torque and flux ripple, current harmonics, and computational effort. [ABSTRACT FROM AUTHOR]