Predictive Reliability Modelling and Characterization of Silicon Carbide Power MOS-Transistors in Grid-Connected Voltage Source Converters

现代社会对电能的依赖几乎与对食物和水的依赖一样重要。在英国，大部分电能是由化石燃料驱动的电机产生的。可持续性原则要求改变能源消费模式，因为燃料储备是有限的。此外，摆脱化石燃料是经济去碳化不可或缺的一部分，而去碳化是应对全球变暖的关键。为此，在利用风能、太阳能和其他可再生能源方面取得了实质性进展。然而，电力通过电网传输和分配的方式也需要改变。可再生能源通常是间歇性的和不可预测的，这使得它不适合与电网直接连接。风能和太阳能等可再生能源只能通过电力电子与电网连接。电力电子需要对电能进行处理和调节，以使其与电网相适应。在电力电子的核心，我们有电力半导体器件，传统上是用硅双极技术制造的。然而，就能量密度而言，硅正在达到其基本极限，因此，转向先进的电力材料，如碳化硅，可以为电力电子领域带来额外的动力。碳化硅是一种宽禁带半导体，具有较高的临界电场和热导率。本课题对采用碳化硅MOS晶体管技术实现的功率转换器的可靠性进行了研究。这些功率变流器通常用于海上风电场，用于高压直流输电(HVDC)系统中的功率转换。该变流器还可用于灵活的交流输电系统，如STATCOMS(静止补偿器)。总体目标是表征在碳化硅MOS晶体管中实现的功率转换器的可靠性。

Modern society's reliance on electrical energy is almost as critical as its reliance on food and water. In the UK, majority of the electrical energy is generated by electrical machines powered by fossil fuels. The principles of sustainability require that the energy consumption pattern changes since fuel reserves are finite. Furthermore, shifting away from fossil fuels is integral to the de-carbonisation of the economy which is critical for tackling global warming. To this end, substantial progress has been made on harnessing wind, solar and other renewable energy sources. However, change is also required in the manner in which electricity is transmitted and distributed through the grid. Renewable energy is usually intermittent and unpredictable, characteristics which make it unsuitable for direct connection with the electric grid. Renewable sources like wind and solar energy can only interface with the electrical grid through power electronics. Power electronics is required for the processing and conditioning of electrical energy so as to make it complaint with the grid. At the heart of power electronics, we have power semiconductor devices which have traditionally been fabricated out of silicon bipolar technology. However, silicon is reaching its fundamental limits in terms of energy density, hence, moving to advanced power materials like silicon carbide can give added impetus to the field of power electronics. Silicon carbide is a wide bandgap semiconductor with a higher critical electric field and higher thermal conductivity. In this project, the reliability of power converters implemented in Silicon-Carbide MOS-Transistor technology is investigated. These power converters will typically be used in off-shore wind-farms for power conversion in high voltage DC transmission (HVDC) systems. The converters can also be used in flexible AC transmission systems like STATCOMS (Static Compensators). The overall objective is to characterize the reliability of power converters implemented in silicon-carbide MOS transistors.