‌Fault Management

IGBT/Diode pairs used at the heart of MMC-VSC converters are very vulnerable to high current transients and faults. So, it is critical that all the necessary protections are in place to ensure a cascade failure will not happen, which could be catastrophic from both technical and financial perspectives. To this end, we are working on fault management technologies and novel circuit breaker architectures that will enable a safe operation of converters. For example, we evaluate the impact of recent emergence of Silicon Carbide (SiC) power devices, i.e. thyristors, as protection units for MMC converters and to address the opportunities and challenges introduced by application of these devices.

‌Reliability Analysis

The newly emerged wide bandgap semiconductor devices, especially SiC power devices, have advantages which come mainly due to unipolar structure of these devices, enabling high switching rates. However, the combination of such fast switching transients with parasitic inductances in wirebonds and interconnecting passives are the source of electromagnetic strees, i.e. oscillations, in the output terminals of the device. This can have serious implications on reliability and control of the wide-bandgap-enabled power converters. We investigate main roots of such reliability concerns in SiC power modules. Some of these can be categorized as:

Investigation of risk mitigation techniques and their effectiveness along with potential impact on the performance are also amongst our interests.

Converter Topologies

We investigate design of different converter topologies that could be used in grid-level application to enhance performance and reliability of converters. Half-bridge, full-bridge and hybrid converter architectures such as Alternate Arm Converter (AAC) and Series Bridge Converter (SBC) are amongst the topologies under research. These topologies can enable features such as fault blocking capability which would enhance reliability at a low expense compared with installation of DC circuit breakers. Design challenges of bespoke topologies for specialist applications, such as LVDC converters in distribution networks is another area of interest.