Predictive torque control for voltage source inverter‐permanent magnet synchronous motor based on equal torque effect

Abstract

In this paper, equal torque effect (ET-effect) is discovered, which means that the same torque can be obtained by applying different voltage vectors whose terminals locate on a special curve called the equal torque curve (ET-curve). By means of ET-effect, an improved predictive torque control (PTC) without weighting factor is proposed. First, to obtain the volt-sec vectors whose terminals locate on the ET-curve, the proposed PTC calculates the duty cycles of all the voltage vectors intersected with the ET-curve, and then establishes finite control set by accumulating those volt-sec vectors. Second, a cost function that includes only the flux error is defined to select the optimal volt-sec vector, and thus to avoid weighting factor adjustment since the torque error no longer exists in the cost function. Because of the two-step optimisation of torque and flux, the proposed PTC can avoid the problem that the duty cycle cannot be fully utilised in standard PTC. As a result, the proposed PTC achieves better performance of torque and flux than standard PTC and PTC with duty cycle. Finally, experiments have been carried out to validate the proposed PTC strategy.