A high performance Si&SiC based hybrid asymmetrical multilevel cascaded H-bridge converter and its advanced control

中压和大功率驱动器广泛应用于各种应用中，例如石油化工或过程工业等，但大多数安装的中压电机都以恒速运行。因此，迫切需要引入具有更高功率质量的更高效的变速驱动器。受控MV驱动器的设计面临着与变换器的拓扑结构和控制以及功率半导体器件相关的许多挑战。通过从多个电平的DC电压合成期望的电压，多电平变换器可以容易地提供中等电压电平和高功率要求。目前，三种拓扑结构的多电平变换器可作为商业工业产品。它们是中性点箝位（NPC），飞跨电容（FC）和级联H桥（CHB）。在这些变换器拓扑中，CHB变换器由于其多个单相变换器的串联结构，可以容易地通过标准的成熟技术组件来达到更高的电压等级和更大的额定功率。与传统的CHB变换器级联相同的单相逆变器具有相等的直流链电压不同，混合不对称CHB变换器联合收割机组合了具有不等直流源电压的各种不同逆变器拓扑。通过这样做，转换器可以联合收割机结合不同拓扑结构的优点，并且以较少的电路和控制实现更高的电压电平。建议的项目是致力于研究混合不对称CHB转换器系统的MV应用。系统的每一相由一个Si基5电平NPC H桥（HV单元）和一个SiC基3电平H桥（LV单元）组成。通过以6：1的比例配置两个电池的直流总线电压，将合成15电平相输出电压波形。近年来发展迅速的SiC开关被认为是快速开关应用的理想选择。然而由于制造的复杂性，基于SiC的功率器件的成本仍然很高。提出的混合拓扑结构取代了只有低电压和快速开关单元使用SiC功率开关，这提高了整个系统的性能与合理的价格。该项目旨在研究混合变换器系统及其先进控制方法的实施。

Medium voltage and high power drives are widely used in various applications, such as in petrochemical or process industries etc. However most of the installed MV motors are running with a constant speed. Thus introducing more efficient variable-speed drives with higher power quality is highly demanded. The design of controlled MV drives is faced with a number of challenges that relate to the topologies and control of converters, as well as power semiconductor devices. By synthesizing a desired voltage from several levels of DC voltages, multilevel converters can easily provide the medium voltage level and high power requirements. Nowadays, three topologies of the multilevel converter are available as commercial industrial products. They are neutral point clamped (NPC), flying capacitors (FCs) and cascaded H-bridge (CHB). Among these converter topologies, CHB converters can easily reach higher voltage level and lager power rating by standard mature technology components because of its series connection structure of several single phase converters. Unlike the conventional CHB converters cascading identical single phase inverters with equal dc-link voltage, the hybrid asymmetrical CHB converters combine various different topologies of inverters with unequal DC source voltages. By doing this, the converter can combine the advantages of different topologies, and achieve higher voltage levels with less circuit and control. The proposed project is devoted to investigate a hybrid asymmetrical CHB converter system for MV applications. Each phase of the system is composed of one Si-based 5-level NPC H-bridge (HV cell) and one SiC-based 3-level H-bridge (LV cell). A 15-level phase output voltage waveform will be synthesized by configuring the dc-bus voltages of two cells in the ratio of 6:1. The resent fast developed SiC switches are considered as ideal candidates for fast switching applications. However due to the complexity of manufacturing, the cost of SiC-based power devices is still high. The proposed hybrid topology replaces only the low voltage and fast switching cells by using SiC power switches, which increases the performance of the whole system with a reasonable price. The project aims at investigating hybrid converter systems and implementation of their advanced control methodologies.