Generalized Terminal Modeling of Electro-Magnetic Interference

Abstract

Terminal models have been used for various power electronic applications. In this work a two- and three-terminal black box model is proposed for electro-magnetic interference (EMI) characterization. The modeling procedure starts with a time-variant system at a particular operating condition, which can be a converter, set of converters, sub-system or collection of components. A unique, linear equivalent circuit is created for applications in the frequency domain. Impedances and current / voltage sources define the noise throughout the entire EMI frequency spectrum. All parameters needed to create the model are clearly defined to ensure convergence and maximize accuracy. The model is then used to predict the attenuation caused by a filter with increased accuracy over small signal insertion gain measurements performed with network analyzers. Knowledge of EMI filters interactions with the converter allows for advanced techniques and design constraints to optimize the filter for size, weight, and cost. Additionally, the model is also demonstrated when the operating point of the system does not remain constant, as with AC power systems. Modeling of a varying operating point requires information of all the operating conditions for a complete and accurate model. However, the data collection and processing quickly become unmanageable due to the large amounts of data needed. Therefore, simplification techniques are used to reduce the complexity of the model while maintaining accuracy throughout the frequency spectrum. The modeling approach is verified for linear and power electronic networks including: a dc-dc boost converter, phase-leg module, and a simulated dc-ac inverter. The accuracy of the model is confirmed up to 100 MHz in simulation and at least 50 MHz for experimental validation.