An Approach to Improve System Performance in the Vehicle-Grid System Using Sliding Mode Control Under Multiple Operation Conditions

To improve the performance of vehicle-grid system under multiple operation conditions and suppress the low-frequency oscillation (LFO) in electrified railways, this paper proposed a control strategy of electric multiple units (EMUs) traction line-side converter (LSC) based on sliding mode control (SMC). First, the accurate model of EMUs is established and then the mathematical model of it in the d-q frame is derived. Then, the application of sliding mode variable structure control strategy in the LSC of EMUs is presented in detail, which includes the design of outer loop voltage sliding mode surface and inner loop current control law. Moreover, the control performance for EMUs based on SMC and traditional linear proportional integral (PI) control is compared under multiple operation conditions in the case of one traction drive unit of EMUs and multi-EMUs, respectively. Finally, experiments are implemented on the hardware in the loop simulation platform based on software StarSim. The experiments results show that, compared with PI control, SMC owns better control performance, such as the lower total harmonic distortion of traction line-side current under multiple conditions, lower voltage fluctuation when braking occurs, better anti-interference ability with the change of system parameters, and can effectively suppress the LFO occurs under operation mode.