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

新型模块化高密度高效率中压功率变换器大功率固态功率变换器是许多应用中的关键部件，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，为了简单起见，大多数这样的功率转换器的额定值低于1千伏或在较低的电压等级内。近来，为了进一步降低系统成本和提高效率，工业正转向中压解决方案，其可以直接接入中压电网，以节省笨重的Transformer、电缆和转换器的成本。为了实现这一目标，需要开发一种高效率、高功率密度/小体积并且具有接近理想正弦波形的交流输出波形的中压大功率固态功率转换器。为了解决这一问题，原理研究者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，它将级联模块单元的支路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。特别地，与经典的模块化多电平转换器解决方案相比，具有二极管作为三电平结构的整流器变化可以提供显著的成本和总系统尺寸节省以及效率提高。与现有技术的解决方案相比，所提出的解决方案可以将转换器的体积/重量减少多达50%，并且将转换器效率提高多达30%，同时实现相同的电压和电流额定值。此外，由于采用模块化设计，该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，以适应未来的应用，而无需进行大量的工程设计返工。低压和中压碳化硅器件可用于所提出的拓扑家族中，以利用其开关损耗节省来合成高保真交流输出。这种模块化设计还意味着内置的系统冗余，这可以大大提高系统的可靠性。因此，所提出的解决方案的智力优势将对广泛的中压功率转换应用产生强烈影响，如可再生能源电网集成、海底和海上直流电力输送、海军中压直流电力系统、工业变速驱动器和运输高速电力推进系统。对于这种拓扑结构及其变体，存在许多基本的控制挑战和操作分析。通过所提出的程序，详细的拓扑结构和操作分析的建议转换器拓扑的家庭将执行单位功率因数和非单位功率因数条件。相臂和相能量平衡策略将在仿真中进行探索和验证。并通过详细的工程设计分析其优势，包括故障处理能力。最后，将开发缩放的原型，以展示其创新性和对行业的好处。由大学提供的独特的工业联盟和海军合作将促进工业成员、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研究计划产生强大的影响。该奖项反映了NSF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.