Computer aided electromagnetic design of power electronic networks

D.Ing. (Electrical and Electronics Engineering)This thesis treats aspects of the modelling techniques required for Computer Aided Design (CAD) of electromagnetically integrated structures for use in power electronic networks. The concept of structural impedance is introduced and developed, building on transmission line theory. Computer based methods for calculating the distributed parameters of a given structure are investigated. These methods are the Finite Element Method and the Incremental Method. Based on the structural impedance lumped element equivalent circuit models for interconnections are developed for modelling of the distributed energy storage effects associated with a physical circuit as part of a lumped element network that can be submitted to circuit simulation programs like SPICE. The models are used in SPICE circuit simulations of power circuits and the simulated results are verified experimentally. Circuit level simulation models for switches are investigated in order to determine the complexity and detail of models suitable for CAD of complete converter topologies. A classification scheme for circuit models of switches is developed as an aid in selection of suitable models for particular simulation purposes. A DC circuit model for power BJT's is developed as a theoretical exercise to determine the requirements, with regard to development time and computational resources, for application of a particular switch model. It is based on new ideas in an attempt to model the effects of power BJT operation of interest to power electronic circuit designers while decreasing the calculation requirements in comparison with sophisticated device physics based models normally used or over simplified models. Finally suggestions are made with regard to a new way of approaching the optimization of power conditioning circuits by using power flow as the basis. This includes the novel use of specially manufactured high permittivity dielectric materials to adjust the characteristic impedance of connections to obtain optimal operation under particular operating conditions