A bipolar-DC-bus EV fast charging station with intrinsic DC-bus voltages equalization and minimized voltage ripples

This paper proposes a bipolar-dc-bus Electric Vehicle (EV) charging station without a line-frequency transformer at the medium-voltage grid side. It is mainly composed of the Neutral Point Clamped (NPC) converter based central ac-dc station and the parallel isolated three-level dc-dc converter based fast chargers. Due to the elimination of the line-frequency transformer, the volume and cost of the system are reduced. Meanwhile, the isolation and step-down between high dc-bus voltages and low load voltages are performed through the high-frequency transformers, leading to increased voltage utilization of switching devices. In order to guarantee the bipolar dc buses balance and minimize the dc-bus voltage ripples, the 180°-interleaved operation for the two parallel isolated three-level dc-dc converters is proposed to make the total neutral-point current zero so that all fast chargers do not bring any unbalance problems. The proposed 180°-interleaved operating principle has been analyzed in detail, then simulation results are presented to verify its performance.

[1]  J. R. Pinheiro,et al.  The three-level ZVS PWM converter-a new concept in high voltage DC-to-DC conversion , 1992, Proceedings of the 1992 International Conference on Industrial Electronics, Control, Instrumentation, and Automation.

[2]  Sanzhong Bai,et al.  Unified Active Filter and Energy Storage System for an MW Electric Vehicle Charging Station , 2013, IEEE Transactions on Power Electronics.

[3]  Yongsug Suh,et al.  A design and control of bi-directional non-isolated DC-DC converter for rapid electric vehicle charging system , 2012, 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[4]  Fred C. Lee,et al.  A zero-voltage and zero-current switching three-level DC/DC converter , 2002 .

[5]  Bin Wu,et al.  Comprehensive DC Power Balance Management in High-Power Three-Level DC–DC Converter for Electric Vehicle Fast Charging , 2016, IEEE Transactions on Power Electronics.

[6]  Philippe Delarue,et al.  A Bidirectional Three-Level DC–DC Converter for the Ultracapacitor Applications , 2010, IEEE Transactions on Industrial Electronics.

[7]  Jih-Sheng Lai,et al.  An active current reconstruction and balancing strategy with DC-link current sensing for a multi-phase coupled-inductor converter , 2012, 2010 IEEE Energy Conversion Congress and Exposition.

[8]  Xinbo Ruan,et al.  Fundamental Considerations of Three-Level DC–DC Converters: Topologies, Analyses, and Control , 2008, IEEE Transactions on Circuits and Systems I: Regular Papers.

[9]  Bin Wu,et al.  Electric Vehicle Charging Station Using a Neutral Point Clamped Converter With Bipolar DC Bus , 2015, IEEE Transactions on Industrial Electronics.

[10]  P. T. Krein,et al.  Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles , 2013, IEEE Transactions on Power Electronics.