Stator current harmonic elimination control for the high-power synchronous motors with online implementation

摘要

In order to reduce the switching losses and improve the converter efficiency, the switching frequency of the semiconductor devices is usually kept low. However, the low switching frequency operation could lead to a severe harmonic distortion in the stator current and an undesirable modulation delay, which also affect the current control performance. Here, a stator current harmonic elimination control scheme has been studied for the electrically excited synchronous motor (EESM). First, extracting the stator current amplitudes of the fundamental and harmonic components by the sliding discrete Fourier transform (SDFT) algorithm. Then, these obtained current amplitudes will be taken as a part of the cost function for the current model predictive control strategy along with the switching losses and neutral point potential issues. For the further algorithm simplification and performance improvement, a reduced-order processing has been also introduced to realise a simple digital implementation. Finally, simulation and experiments demonstrate that this kind of stator current control could realise a similar characteristic with the selective harmonic elimination along with an online implementation and nice dynamic performance.