Abstract-In multi-winding transformers, different geometry of the individual windings leads to unbalanced leakage flux paths. The unbalance affects the behaviour of the power electronic converters, where these transformers are used. This work proposes an approach to model the leakage flux path of transformer with repetitive multi-winding structure using permeance magnetic circuit. The model is composed of lumped components, it can be seamlessly integrated into system-level simulation of power electronic circuits and achieve good accuracy in time-domain simulation. Taking advantage of the repetitive structure, the model requires very limited number of parameters, which can be easily obtained from the geometry information together with only a few experimental tests. The fidelity of the model is experimentally confirmed on a multi-winding transformer prototype connected to power electronic devices.
Ferrite materials are widely used for magnetic cores in power electronic converters. The hysteresis effect of the material leads to power loss and harmonic distortion. In order to predict the behaviour of the magnetic component in the system environment during the design phase, accurate system-level timedomain simulation is desired. This work proposes an approach to model the frequency-independent magnetic hysteresis effect of ferrite core materials in magnetic circuits based on the permeance-capacitance analogy. The model is able to accurately reproduce the per-cycle energy loss and equivalent permeability of the hysteresis loops under excitation in a wide range of amplitudes.
Magnetic components using soft core materials are widely used in power electronic converters. The hysteresis effect of the material leads to power loss and harmonic distortion. If this effect can be modeled in system-level time-domain simulation, the performance of the magnetic component in combination with power converters can be predicted more accurately during the design phase. This work proposes an approach to model the hysteresis effect of soft magnetic materials in magnetic circuits based on the permeance-capacitance analogy.
Cascaded H-Bridge converters in medium voltage applications have all the DC link capacitors supplied from external source through a multi-winding phase-shift transformer. This type of transformers has a complex winding geometry, which leads to unbalanced leakage flux paths. The unbalance affects the dynamic behaviour of the converters. This work proposes a modeling approach which realistically captures the unbalance in the leakage flux path of phase-shift transformers, using permeance magnetic circuit. The model can be seamlessly integrated into system-level simulation of power electronic circuits. Taking advantage of the repetitive structure of the windings, the model requires very limited number of parameters, which can be easily obtained from the geometry data together with only a few experimental tests. The fidelity of the model is experimentally confirmed on a phase-shift transformer from a commercial medium-voltage drive system.
Abstract-Lumped magnetic circuit provides possibility for fast transient simulation of magnetic component together with power electronics circuit. The simplified geometry representation however is not able to completely reflect the real field distribution, especially when material nonlinearity is included. To model electrical characteristic of the magnetic components closer to the reality, special treatment is needed to determine geometrical parameters of the lumped representation. In this paper, modeling of the curved areas (e.g. core corners) based on permeances is presented and compared with FEM simulations.
Abstract-The size and position difference of the windings determine the leakage flux path and give rise to unbalance of the short-circuit impedances, which strongly affects the transient behaviour of the transformer. This work proposes a new approach of modelling with magnetic equivalent circuit, making use of the transformer geometry and permeance magnetic equivalent circuit, which is suitable for system-level simulation in terms of complexity. Equivalent model requires limited number of parameters and for verification purposes, FEM simulations as well as measurement on the experimental prototype have been performed.
Hysteresis effect of core materials contributes significantly to the power loss and nonlinearity of the transformers and filter inductors in power electronic applications. For design or modeling of the magnetic components, information of the magnetic material's characteristic under the desired operation condition is usually required. In many common types of power converters the magnetic components undertake biased excitation, which leads to hysteresis loop with DC-offset on both magnetic field strength and flux density. This work proposes a test setup combining both linear amplifier and switching cells, which is able to conveniently generate magnetic hysteresis loops at arbitrary biased levels.
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