Modelling and Optimisation of Power Electronics using Fast Switching Devices and Compact Passive Filters

The number of power electronic applications have increased over the recent years while simultaneously the demands on existing applications, such as size and efficiency, become more stringent. With DC microgrids being developed and used in homes and vehicles, more room for optimisation is available for converters, as typical AC conversion steps can be omitted. Together with this increased interest, research into new power electronic switches has lead to the productization of Si superjunction MOSFETs, SiC MOSFETs and GaN HEMTs which allow for design of power converters with smaller volume and/or higher efficiency. While the application space for classic power devices such as Si IGBTs and Si MOSFETs, is relatively clear, this is not yet the case for the new devices. Another sizeable part of a typical converter are the passive filter components. Many topologies and magnetic materials are available, but quantifying the possible gains of a particular design choice for an application, remains a challenge.In this work, the optimisation of the passive filter of a DC-DC converter by means of integrating three inductors is investigated. In this topology, the size of the converter can be decreased by coupling the magnetic storage of multiple converter half-bridge legs. The challenge here lies in quantifying how much can be gained by using this topology. To this end, an extensive magnetic and electric model is created to be able to simulate the magnetic field and current distribution in the core and windings of the inductive component. The model is used in an automated optimisation algorithm which finds optimal designs according to multiple given objectives. This is required in most practical applications were typical trade-offs are possible regarding cost, weight, efficiency, volume, ... . The approach for simulation in this work vastly improves both in accuracy and applicability compared to existing approximative simulation methods, while still providing orders of magnitude less simulation time than traditionally used finite element methods.Optimisation of power electronic converters can also be achieved by incorporating the new power electronic switching devices allowing operation with less generated losses or at higher switching frequencies, which allows for the use of smaller filters. Therefore, in this work, a method is presented to be able to quickly quantify the differences of using the new switching devices in a specific application for converters based on hard-switching half bridge topologies. The derivation of the method shows how some important device characteristics are missing from typical datasheets. Furthermore, the method also provides a means to evaluate the quality of provided simulation models.In a following step, a method for generating a much more detailed simulation model for these power electronic switching devices is proposed. The model can be used in SPICE simulators and is aimed towards the detailed design of a converter. Such models are crucial for developing power electronic converters, but they are not always provided by manufacturers for the new components, and their accuracy is not always sufficient for detailed designs. This work improves on the accuracy, while also detailing what impact the differences between model and reality can have on the behaviour of the component in a real converter. The usage of the simulation model in the evaluation of a converter is demonstrated on a prototype DC-DC converter using SiC MOSFETs. Here, the identification of model parameters, not provided by the component datasheets, is performed, while the effect of modelling errors on the simulated circuit behaviour is demonstrated. The automated creation of SPICE models is an important step into finding the application space of these new switching components.

Jaar van publicatie:2021

Toegankelijkheid:Open