Architecture and Control of An Interleaved 6-Level Bidirectional Converter With an Active Energy Buffer for Level-II Electric Vehicle Charging

Abstract

On-board electric vehicle (EV) chargers convert grid ac voltage to dc voltage to charge a high-voltage battery pack. High efficiency and high power density single-phase acdc converters are desirable in such applications to reduce the heat loss, volume and weight of these chargers. Moreover, the capability of bidirectional conversion is preferred for potential vehicle-to-grid applications. This paper presents the system architecture and embedded digital control implementation of a 7 kW, universal ac (120-240 V AC ) to 400 V DC single-phase acdc bidirectional converter. The converter features an interleaved 6-level flying capacitor multilevel (FCML) ac-dc stage and a series-stacked buffer for buffering twice-line frequency pulsating power to achieve high efficiency and power density. Test results that demonstrate both ac-dc power factor correction (PFC) and inverter operation at kilowatt levels are provided.

Review of Electric Vehicle Charging Technologies, Standards, Architectures, and Converter Configurations

“…17(f). The flying capacitor with closed-loop control techniques is presented in [248] and six levels interleaved flying capacitor converter is proposed in [249] to achieve high power density and efficiency.…”

A Comprehensive Review of Power Converter Topologies and Control Methods for Electric Vehicle Fast Charging Applications

“…In [103] and [104], a seven-level FCMLC have been demonstrated. Further, in study [105] and [106], authors have presented an interleaved six-level FCMLC for the purpose of achieving high efficiency and high-power density. In [107], a three-phase FCMLC has been designed in which each input phase is connected to six-level FCMLC as shown in Fig.…”

“…To deal with the issue of double line frequency pulsation, active buffer is adopted as a power decoupling stage [103], [106]. Since FCMLC scales down the filter size significantly with high frequency operation, utilization of smaller inductor causes current phase leading and bring challenges for PFC control.…”

“…Finally, the feedforward control term is added to the duty ratio to predict the disturbance from the rectified sine wave and thus, its impact is neutralized. Moreover, in [106], similar PFC control is adopted for the interleaved FCMLC converter that performs additional control tasks considering equal current sharing between the interleaved stages.…”

On the Role of Switch Output Capacitance on Passive Balancing within the Flying Capacitor Multilevel Converter

“…Power converters in applications such as traction and propulsion drives, and data center power delivery require high power density and efficiency. In pursuit of maximizing these objectives, the Flying Capacitor Multi-Level (FCML) converter has emerged as a promising topology for these cutting edge applications [1], [2]. Although the topology was initially developed to remedy the lack of high voltage switches rated for the input voltage in high voltage power conversion applications [3], it is able to outperform conventional topologies in lower voltage applications where even though a monolithic switch may be available, the series combination of multiple lower voltage switches is found to be higher performance [4].…”