The modular multilevel converter (MMC) is the most preferred choice for high-voltage direct current (HVdc) applications. In this article, a new hybrid-legs bridge converter (HLBC) is presented as an alternative to the MMC. This converter is a hybrid of a two-level converter and an MMC. For a three-phase system, three single-phase HLBCs are connected either in series [series-connected HLBC (SHLBC)] or in parallel [parallel-connected HLBC (PHLBC)] across the dc-link. Compared to the MMC and the series-connected MMC, the SHLBC requires only one-third and half the submodules (SMs), respectively. Besides, the SHLBC eliminates the requirement of any arm inductor or dc-side filter. The structure and operating principle of the HLBC are described. Moreover, the minimum SM capacitance required to limit its voltage fluctuation is calculated. The dc fault-tolerant capability of the SHLBC and PHLBC is achieved by replacing some of the unipolar SMs with bipolar SMs. The operation, applicability for HVdc systems, ac fault ride through and dc fault-tolerant capability of the proposed converter are verified using PSCAD simulations. Furthermore, the feasibility of the proposed converter under normal and dc fault conditions is revalidated experimentally by using a three-phase grid-connected HLBC laboratory prototype. A comparative analysis is carried out to highlight the benefits of the proposed HLBC over the existing converter topologies.

中文翻译：

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Hybrid-Legs 桥式转换器：灵活且紧凑的 VSC-HVDC 拓扑

模块化多电平转换器 (MMC) 是高压直流 (HVdc) 应用的最佳选择。在本文中，提出了一种新的混合腿桥式转换器 (HLBC) 作为 MMC 的替代方案。该转换器是两电平转换器和 MMC 的混合体。对于三相系统，三个单相 HLBC 通过直流链路串联 [串联 HLBC (SHLBC)] 或并联 [并联 HLBC (PHLBC)]。与 MMC 和串联 MMC 相比，SHLBC 分别只需要三分之一和一半的子模块 (SM)。此外，SHLBC 消除了对任何臂电感器或直流侧滤波器的要求。描述了 HLBC 的结构和工作原理。此外，还计算了限制其电压波动所需的最小 SM 电容。SHLBC 和 PHLBC 的直流容错能力是通过用双极 SM 替换一些单极 SM 来实现的。使用 PSCAD 模拟验证了所提出转换器的操作、HVdc 系统的适用性、交流故障穿越和直流容错能力。此外，通过使用三相并网 HLBC 实验室原型，通过实验重新验证了所提出的转换器在正常和直流故障条件下的可行性。进行了比较分析以突出所提议的 HLBC 相对于现有转换器拓扑的优势。使用 PSCAD 模拟验证了所提出的转换器的交流故障穿越和直流容错能力。此外，通过使用三相并网 HLBC 实验室原型，通过实验重新验证了所提出的转换器在正常和直流故障条件下的可行性。进行了比较分析以突出所提议的 HLBC 相对于现有转换器拓扑的优势。使用 PSCAD 模拟验证了所提出的转换器的交流故障穿越和直流容错能力。此外，通过使用三相并网 HLBC 实验室原型，通过实验重新验证了所提出的转换器在正常和直流故障条件下的可行性。进行了比较分析以突出所提议的 HLBC 相对于现有转换器拓扑的优势。