The dual-active bridge (DAB) topology is commonly preferred in bidirectional applications due to several attractive features, including auto-adjust of power flow, galvanic insulation, wide voltage gain, and zero voltage switching (ZVS) capability over some power ranges. However, the efficiency of the converter drops at light loads because the ZVS range is directly dependent on the circulating current. Assuming that the processed power is variable, the DAB converter's design must find a compromise between extending ZVS ranges and reducing the reactive power processing to ensure higher efficiency. Aiming this compromise, many papers propose hybrid approaches in which the modulation strategy is selected according to the processed power. However, this is not a simple solution because it demands multivariable control and offline optimizations. This paper proposes a modulation strategy to ensure ZVS and reduce the circulating current for the DAB converters. While the usual phase-shift modulation provides ZVS operation in a range of 40% to 100% of rated power, the proposed asymmetrical pulse-width modulation can obtain ZVS operation in a range of 2% to 100% of rated power. Experimental results demonstrated that the proposed strategy improves the converter efficiency for all power ranges, especially at light loads.

中文翻译：

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具有扩展 ZVS/ZCS 范围和减少循环电流的非对称 PWM DAB 转换器，适用于 ESS 应用

双有源电桥 (DAB) 拓扑在双向应用中通常是首选，因为它具有多种吸引人的特性，包括功率流的自动调整、电流绝缘、宽电压增益以及某些功率范围内的零电压开关 (ZVS) 能力。然而，转换器的效率在轻负载时会下降，因为 ZVS 范围直接取决于循环电流。假设处理的功率是可变的，DAB 转换器的设计必须在扩展 ZVS 范围和减少无功功率处理之间找到折衷，以确保更高的效率。针对这种折衷，许多论文提出了根据处理功率选择调制策略的混合方法。然而，这不是一个简单的解决方案，因为它需要多变量控制和离线优化。本文提出了一种调制策略，以确保 ZVS 并减少 DAB 转换器的循环电流。虽然通常的相移调制提供额定功率的 40% 至 100% 范围内的 ZVS 操作，但所提出的非对称脉宽调制可以获得额定功率的 2% 至 100% 范围内的 ZVS 操作。实验结果表明，所提出的策略提高了所有功率范围的转换器效率，尤其是在轻负载下。