A novel method to improve voltage sag rid-through for battery powered PM electric drive system

This paper presents a novel DC link voltage feedforward control to improve the electric drive system tolerance capability to the dc link voltage sag. A uniform mathematic model, comprising the battery packs, voltage source inverter (VSI), permanent magnet synchronous motor (PMSM) is built up in the d-q rotating coordinates rather in three-phase stationary coordinates. In order to study the influence of supply voltage fluctuation to the transient characteristic of the electric drives system, the small signal model is derived and the transformation matrix between the DC link voltage disturbance and the electric machine rotation speed is set up. Aiming to overcome the disadvantage caused by the dc link voltage disturbance, a novel DC link voltage feedforward vector control strategy is proposed, which utilizes the sampled real time DC link voltage rather the constant value in the SVPWM generator. Finally, the simulation study in Matlab/Simulation and the experiment based on dSPACE laboratory prototype conform the proposed controller could improve the dc link voltage sag rid-through capability of the electric drive system.