Exploration of Multilevel Current Source Converters

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Power electronic conversion is a central element of energy conversion systems, acting as the interface between different forms of electrical energy and is an enabling technology for low-carbon economy. By 2030, it is expected that as much as 80% of all electric power will use Power Electronics somewhere within the energy supply chain between generation and consumption. Multilevel converter is one type of power electronics converter and can offer substantial benefits over the established two-level converter counterparts. These include reduced harmonic distortion, less voltage/current stress (dv/dt, di/dt), and mitigated electro-magnetic interference (EMI). Multilevel converters can be classified into multilevel voltage source converters (MVSCs) and multilevel current source converters (MCSCs). The MCSC exhibits several unique advantageous characteristics that may favour its adoption in the low voltage converters used in aircraft, hybrid/electric vehicles and micro renewable power generation. For example, inductors are used as the main energy storage elements in MCSCs, which are more reliable than capacitors in MVSCs. The MCSC has intrinsic current limiting capability, which can be used to constrain fault currents as well as leaving more time for device over-current protection. It may prevent further damage or failure of other components and avoid fire due to over-current. The research into MCSCs is at its infancy. The project therefore will explore the MCSCs through converter topology derivation, modulation techniques, inductor current balancing, loss and efficiency evaluation, etc. The successful investigations of these challenges will reveal the benefits of the MCSCs and facilitate the wide application of the converter. The research will be carried out through modelling, control, simulation and experimental verification. The study of power converter topologies is valued as enabling research in power electronic systems. A breakthrough in MCSCs will benefit the UK world-leading aerospace industry and renewable energy OEMs. Successful development of MCSCs will also feed into the component or sub-system supply chain, in exploiting new power semiconductor technologies (reverse blocking IGBT, wide-bandgap devices) and in requiring new power module configurations and new wound components.