Abstract: A voltage control method. A train traveling speed can be acquired; a target transformation ratio corresponding to the train traveling speed is determined according to correspondences between train traveling speeds and transformation ratios, the transformation ratio being a ratio of an input voltage to an output voltage; an input voltage is then transformed according to the target transformation ratio to obtain an output voltage, the output voltage being used for driving a train to travel. The correspondences between train traveling speeds and transformation ratios are obtained according to correspondences between train traveling speeds and train traction forces at different transformation ratios. By means of the method, the most suitable transformation ratio can be provided according to a traveling speed of a maglev train, thereby increasing the traction force of the maglev train and improving running efficiency.

Abstract: The present invention relates to a method and a system for detecting the harmonic current in synchronous motors. The method includes the following steps: (1) extracting the total stator current harmonics based on the control error between the reference value of fundamental stator current and the feedback value of stator current in the d, q coordinate; (2) using a plurality of synchronous coordinate transformations and low-pass filters to extract each harmonic to be detected from the total harmonic current.