A LFO Suppression Approach for PET-TNCS Based on the Cascaded Nonlinear PI Controller

摘要

The voltage low-frequency oscillation (LFO) occurs between the traction network and electric multiple units in high-speed railway system, which significantly deteriorates the stability and reliability of the railway transportation system. In view of this, a transient direct current control strategy based on the cascaded nonlinear PI controller is proposed for the single-phase power electronic transformer (PET)-based railway traction system. The control strategy is not only simple in design, but also can realize the self-adaptive adjustment of PI parameters through nonlinear functions, which enhances the robust performance of the system. The simulation and test results show that the LFO of power electronic transformer-traction network coupling system (PET-TNCS) occurs with the increase of the number of PETs accessed to the traction network under the traditional linear PI controller and the control strategy proposed in this paper can effectively suppress the LFO.