Collaborative Research: Modular Multilevel Converter With Parallel Connectivity-Novel Topology, Control, and Applications

合作研究：具有并行连接的模块化多电平转换器——新颖的拓扑、控制和应用

• 批准号: 1608929
• 负责人: Angel Peterchev
• 金额: $ 23.96万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1608929&HistoricalAwards=false
• 关键词: Collaborative; Research; Modular; Multilevel; Converter

Rechargeable-battery systems are critical to two technologies that will help reduce the consumption of fossil fuels: electrically-powered transportation systems and energy storage systems for the grid. Despite great improvements in battery cell performance, battery integration into systems still faces significant challenges. Existing solutions are typically highly integrated with the target application, and cannot be repurposed. The systems are often not scalable, and the failure of a single battery cell can cause the entire system to fail. In addition, the power electronics of such systems is optimized for the nominal load, not for partial load, where the system typically operates. This work explores a radically new approach to designing energy storage and energy conversion systems by modularizing and integrating the battery with the power electronics to provide multiple functions using the same semiconductor chip area. The proposed battery technology will use a new multilevel inverter topology that allows dynamically reconfigurable series and parallel connectivity: the modular multilevel series-parallel converter (MMSPC). Modular design of identical sub-systems will enable the same modules to be used in multiple applications, making use of economies of scale to reduce system cost. In electric vehicles, the proposed system can replace hard-wired battery packs with a flexible, dynamically reconfigurable AC battery and replace multiple power electronics units, such as the drive inverter, battery charger, and battery balancing circuits, to provide the output directly from the AC battery. For grid energy storage, the proposed technology enables repurposing modules from various applications, such as electric vehicles, incorporation of cells of different capacity or age into one system, high output quality with substantially reduced or eliminated magnetic components, rapid dynamic response, and easy scaling of the storage and power converter systems by simple addition of AC battery modules.To leverage the advantages of MMSPC, efficient control strategies have to be developed to optimize performance while minimizing system complexity and cost. The control of modular multilevel converters (MMCs) presents both challenges and opportunities associated with the large number of possible switch states. The MMSPC degrees of freedom are even more due to the additional parallel state, which allows widely flexible series-parallel configuration of the circuit, amplifying the need for a coherent control strategy. For instance, in both MMC and MMSPC the same output voltage can be achieved with a multitude of module configurations, providing the opportunity to optimize the switch states based on various additional constraints and objectives such as module balancing, efficiency, output quality, electromagnetic emissions, and switch and storage-element stress. Existing control approaches, however, do not fully exploit this opportunity as they typically reduce the number of objectives and treat the various constraints and objectives independently. Critically, established strategies are not designed to utilize parallel connectivity, precluding exploitation of the MMSPC advantages. Addressing these limitations, we propose to develop a real-time predictive multi-objective optimization framework that systematically unifies the treatment of multiple system constraints and objectives, and overcomes the exponential growth of degrees of freedom with system size and prediction horizon. This control framework will be applicable to both MMC and MMSPC, and will consider additional topology variations within each of these converter families. The advantages of the novel MMSPC topology and control strategy will be demonstrated with the development of a modular AC battery that incorporates multiple battery units, battery management, and inverter functionality for applications such as energy storage systems and electric vehicle drive trains. This innovative concept will improve lifetime, efficiency, and cost of battery systems, and is practical only when the capabilities of the MMSPC and the associated control are leveraged.

可充电电池系统对两项有助于减少化石燃料消耗的技术至关重要：电力运输系统和电网储能系统。尽管电池性能有了很大的改进，但将电池集成到系统中仍然面临着重大挑战。现有的解决方案通常与目标应用程序高度集成，并且不能重新调整用途。这些系统通常不可扩展，单个电池单元的故障可能导致整个系统出现故障。此外，这种系统的电力电子器件针对标称负载而不是系统通常操作的部分负载进行优化。这项工作探索了一种全新的方法来设计能量存储和能量转换系统，通过模块化和集成电池与电力电子设备，使用相同的半导体芯片面积提供多种功能。拟议的电池技术将使用一种新的多电平逆变器拓扑结构，允许动态可重构的串联和并联连接：模块化多电平串并联转换器（MMSPC）。相同子系统的模块化设计将使相同的模块能够用于多种应用，利用规模经济降低系统成本。在电动汽车中，所提出的系统可以用灵活的、动态可重构的AC电池来代替硬接线的电池组，并且代替多个电力电子单元，例如驱动逆变器、电池充电器和电池平衡电路，以直接从AC电池提供输出。对于电网能量存储，所提出的技术使得能够重新利用来自各种应用（诸如电动车辆）的模块，将不同容量或年龄的电池合并到一个系统中，具有显著减少或消除的磁性组件的高输出质量，快速动态响应，以及通过简单地添加AC电池模块来容易地缩放存储和功率转换器系统。必须开发有效的控制策略来优化性能，同时最小化系统复杂性和成本。模块化多电平变换器（MMC）的控制提出了与大量可能的开关状态相关联的挑战和机遇。由于附加的并联状态，MMSPC的自由度甚至更多，这允许电路的广泛灵活的串并联配置，放大了对相干控制策略的需求。例如，在MMC和MMSPC两者中，可以利用多种模块配置来实现相同的输出电压，从而提供了基于各种附加约束和目标（诸如模块平衡、效率、输出质量、电磁发射以及开关和存储元件应力）来优化开关状态的机会。然而，现有的控制方法，不充分利用这个机会，因为它们通常减少目标的数量和处理的各种约束和目标独立。关键的是，既定的战略并不是为了利用并行连接，排除利用MMSPC的优势。针对这些限制，我们建议开发一个实时预测多目标优化框架，系统地统一处理多个系统约束和目标，并克服了指数增长的自由度与系统规模和预测范围。该控制框架将适用于MMC和MMSPC，并将考虑每个转换器系列中的其他拓扑变化。新型MMSPC拓扑结构和控制策略的优势将通过模块化交流电池的开发得到证明，该电池集成了多个电池单元、电池管理和逆变器功能，适用于储能系统和电动汽车传动系等应用。这一创新概念将提高电池系统的寿命、效率和成本，并且只有在利用MMSPC和相关控制的能力时才实用。