Instantaneous power coordinated control strategy for high-speed train traction converters

Abstract To address the issues of excessive weight in Direct Current (DC)-link capacitors for high-speed train traction converters, which reduce overall power density and increase maintenance costs, an optimized control strategy is proposed. Conventional rectifier-inverter independent control proves inadequate under high-voltage/high-power, low-switching-frequency and limited control bandwidth conditions. The proposed DC voltage-based instantaneous power collaborative control strategy selects the intermediate DC voltage as an indicator of power imbalance, reflecting the relationship between rectifier-side and inverter-side power. During power mismatch events, the intermediate DC voltage fluctuates accordingly. By real-time monitoring of DC voltage variations and dynamic compensation current adjustment, this approach reduces voltage overshoot during load transients and mitigates adverse effects of power imbalance. Using the CR400AF traction converter as a case study, a hardware-in-the-loop experimental platform is established. Experimental verification demonstrates that, at steady state, the coordinated instantaneous power control strategy based on DC voltage achieves similar performance to independent control and power feed-forward control. During transients, compensation current is calculated based on instantaneous power mismatch. Under the same support capacitance value, this method exhibits significantly faster dynamic response speed compared to independent control and power feed-forward control. It effectively suppresses DC voltage spikes during transients, allowing the DC bus voltage to quickly recover to near the reference value. After reducing the support capacitance value, this method can still maintain good dynamic response performance. The findings provide a reference for optimizing control strategies to achieve lightweight support capacitors in the DC-link of traction converters.