Collaborative Research: Novel Modular High-density High-efficiency medium voltage power converter

新型模块化高密度高效中压电源转换器高功率固态电源转换器是许多应用中的关键组件，例如从电网获取可再生能源和储能，例如太阳能，风能和电池以及驱动大功率电机。传统上，大多数这种功率转换器的额定电压低于1千伏或在更低的电压等级内，因为它的简单性。最近，为了进一步降低系统成本和提高效率，工业界正朝着中压解决方案发展，这种方案可以直接接入中压电网，以节省笨重的变压器、电缆和转换器的成本。为了实现这一目标，需要开发一种高效、高功率密度/小体积、交流输出波形接近理想正弦波形的中压大功率固态电源变换器。为了解决这一问题，研究人员提出了一种新型的模块化高密度中压功率变换器拓扑结构，即三电平混合模块化多电平变换器，它将分支级联模块单元与传统的三电平结构相结合。所提出的概念导致中压应用的各种拓扑变化。特别是，与经典的模块化多电平变换器解决方案相比，以二极管作为三电平结构的整流器变体可以提供显着的成本和总体系统尺寸节省以及效率提高。与目前的解决方案相比，该方案可以在达到相同电压和电流额定值的情况下，将转换器的体积/重量减少多达50%，将转换器的效率提高多达30%。此外，由于模块化设计，所提出的解决方案还可以实现高保真交流输出，并且可以扩展到更高的额定电压，以满足未来的应用，而无需密集的工程设计重做。低压和中压碳化硅器件可用于所提出的拓扑系列中，以利用其开关损耗节省来合成高保真交流输出。这种模块化设计也意味着内置系统冗余，可以大大提高系统可靠性。因此，该解决方案的智能优势将对广泛的中压电源转换应用产生重大影响，如可再生能源电网集成、海底和海上直流输电、海军中压直流电源系统、工业变速驱动和交通高速电力推进系统。对于这种拓扑及其变体，存在许多基本的控制挑战和操作分析。通过所提出的程序，将在单位功率因数和非单位功率因数条件下对所提出的转换器拓扑进行详细的拓扑和运行分析。相臂和相位能量平衡策略将在仿真中进行探索和验证。并通过对下选实例系统的详细工程设计，分析其优点，包括故障处理能力。最后，将开发出规模原型，以展示其创新和工业效益。由大学提供的独特的行业联盟和海军合作将促进行业成员、海军研发社区和学术研究人员之间的合作关系，从而通过NSF的研究计划产生强大的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Novel Modular High-density High-efficiency Medium-voltage Power ConverterHigh power solid-state power converter is a critical component in many applications, such as accessing renewables energy and energy storages from grid, e.g. solar, wind, and batteries and driving high power motors. Traditionally, most of such power converter are rated below 1 kilovolt or within lower voltage class for its simplicity. Recently, for further system cost reduction and efficiency improvement, industry is moving toward medium-voltage solutions, which can directly access the medium voltage grid, to save bulky transformer, cables and cost of the converter. To achieve such goal, it is desirable to develop a medium voltage high-power solid-state power converter, which is high-efficient, high power density/low volume and with ac output waveform close to an ideal sinusoidal waveform. To address such desire, the principle investigators proposed a novel modular high density medium-voltage power converter topology, namely three-level hybrid modular multilevel converter, which combines branches with cascaded modular cells and traditional three-level structure. The proposed concept leads to various topology variations for medium voltage application. In particular, the rectifier variation with diode as the three level structure can provide a significant cost and total system size saving and efficiency improvement compared to classic modular multilevel converter solution. Compared with the state of art solution, this proposed solution can reduce the converter volume/weight by up to 50% and the improve the converter efficiency by up to 30% while achieve the same voltage and current rating. In addition, thanks to the modular design, the proposed solution can also achieve high-fidelity ac output and can be scaled up to higher voltage rating for future applications without intensive engineering design rework. The low voltage and medium voltage silicon carbide devices can be used in the proposed family of topologies to leverage its switching-loss savings to synthesize high-fidelity ac output. Such modular design also means built-in system redundancy which can substantially improve system reliability. Thus, the intellectual merits of the proposed solution will make a strong impact on a broad range of medium voltage power conversion applications, like renewable energy grid-integration, subsea and offshore dc power delivery, naval medium voltage direct current power system, industrial variable speed drives, and transportation high-speed electric propulsion system. There are many fundamental control challenges and operation analysis for this topology and its variations. Through the proposed program, the detailed topology and operation analysis of the family of proposal converter topology will be performed for both unity power factor and non-unity power factor conditions. The phase-arm and phase energy balancing strategies will be explored and verified in simulation. And its benefits will be analyzed through detailed engineering design for down-selected example systems, including fault handling capability. In the end, scaled prototypes will be developed to demonstrate its innovation and benefit to industry. The unique industry consortium and Navy collaboration provided by the universities will foster a collaborative relationship among industry members, Navy R&D community, and academic researchers, which will consequently make a strong impact through this NSF research program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.