Current-balancing strategy for multileg interleaved DC/DC converters of electric-vehicle chargers
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ORIGINAL ARTICLE
Current‑balancing strategy for multileg interleaved DC/DC converters of electric‑vehicle chargers Hye‑Won Choi1 · Seok‑Min Kim1 · Jinwoo Kim2 · Younghoon Cho2 · Kyo‑Beum Lee1 Received: 4 September 2020 / Revised: 13 October 2020 / Accepted: 14 October 2020 © The Korean Institute of Power Electronics 2020
Abstract A current-balancing strategy for a multileg interleaved DC/DC converter with a reduced number of current sensors for electric-vehicle chargers is proposed in this paper. There are imbalances between the leg currents of multileg DC/DC converters, which are caused by the difference between the leg impedances and the driver delay. Each of the leg current sensors must achieve current balancing. However, the conventional strategy is burdensome due to its high cost and volume. To mitigate these issues, the proposed balancing strategy effectively balances leg currents using fewer current sensors than the number of legs. The proposed strategy was verified by various simulation and experimental results. Keywords Current-balancing strategy · Multileg interleaved converter · Reducing current ripple · Electric vehicle charger
1 Introduction Multileg DC/DC converters are generally used for highpower applications in electric vehicles (EVs), power factor compensation devices, uninterruptible power systems, etc. [1–7]. The interleaving scheme is used in high-current applications, and the main advantage of using this scheme is the reduction of output current/voltage ripple [8–13]. Figure 1 shows a buck converter with six parallel legs for using the interleaving scheme. All six legs consist of the same switching devices, including metal–oxide–semiconductor fieldeffect transistors (MOSFETs), diodes, and filter inductors. The frequencies of the leg currents have equivalent values since each of the legs operates at the same switching frequency, and the frequency of the output current is increased due to the interleaving scheme [14–20]. In addition, the output ripple current is reduced since each of the leg triangular carrier waves has a delay of 2π over the number of legs between any adjacent waves for the interleaved operation of each leg current.
* Kyo‑Beum Lee [email protected] 1
Department of Electrical and Computer Engineering, Ajou University, Suwon, South Korea
Department of Electrical and Electronics Engineering, Konkuk University, Seoul, South Korea
2
Leg current imbalance is a well-known issue for multileg DC/DC converters. It is caused by the nonideal characteristics of each leg component and driver, such as MOSFET conduction resistance, driver delay, and passive circuits. Each leg current imbalance results in inductor saturation and switching transistor damage, which lead to deteriorations of the efficiency, stability, and reliability of multileg converters. Balancing of the inductor currents in the legs is a crucial issue for multileg structures to alleviate these drawbacks. To address this issue, several techniques have been proposed, including sensor-based and sensorless methods [21
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