Compensation of DC-Link Voltage Fluctuation for Railway Traction PMSM in Multiple Low-Switching-Frequency Synchronous Space Vector Modulation Modes

DC-link voltage fluctuation, originated from the single-phase power supply, has a significant impact on the railway traction drive system. Instead of employing a large LC filter to suppress the fluctuation, software solutions are of more interests, since they do not add additional components to the system. A state-of-the-art feedforward strategy predicts the dc-link voltage pattern based on its repetitive nature and directly modifies the duty cycle fed to the inverter to eliminate the impact of the fluctuation. Yet this strategy requires a symmetrical and consistent pulse pattern. In this paper, a compensation approach for synchronous space vector modulation with multiple pulse patterns is proposed. It utilizes the prediction of the dc-link voltage pattern and, based on the volt-second balancing principle, modifies the switching instants corresponding to different pulse patterns. Simulation and experimental results show that the proposed method can significantly eliminate the impact of the fluctuation.