On the Modeling and Suppression of Electromagnetic Interference Emissions of Power Converters

Abstract

Electromagnetic interference (EMI) issues are associated with high-speed switching of power converters. EMI modeling is an essential tool to study and control the EMI emission, enabling more efficient solutions. A comprehensive review and comparison of different modeling approaches for conducted emissions are provided in this paper, which can be used as a design guideline for engineers. Electromagnetic compatibility (EMC) measurement devices and testing procedures are also reviewed for power converter applications. This overview would help the reader to obtain a better understanding of the EMC testing procedure, requirements, and the EMC measurement devices. Afterwards, conducted emissions in a three-phase inverter fed motor drive is studied. A physics-based model is derived for each part of the system using a device characterization tool, a finite element analysis tool, and impedance curve fitting tools. An improved universal equivalent circuit is proposed to model the induction motor in the entire frequency range. A balanced approach regarding the accuracy and simplicity of the model is considered through the model extraction. Furthermore, common mode and differential mode emissions are studied, and two equivalent circuits are extracted.

Spread spectrum modulation techniques have been proven to be an effective solution to suppress the conducted electromagnetic emissions of power converters. Various modulation methods are investigated for an active neutral point clamped (ANPC) inverter. The effect of EMI receiver and intermediate filter bandwidth is also considered in the modeling. Furthermore, a new unified model is proposed for an active neutral point clamped inverter based on the existing equivalent circuit models for common mode (CM) EMI and the developed DM model. In another approach to reduce the EMI emissions, a new hybrid CBPWM strategy is proposed that not only eliminates the neutral point voltage oscillations but also reduces the common mode voltage (CMV) by half. Furthermore, the harmonic content of the output voltage is reduced by adjusting the modulation waves based on the location of the reference vector in the space vector diagram. An active neutral point voltage controller is also presented and applied in order to maintain the performance of the modulation strategy under the NPV perturbations. Modeling and simulation results are validated by experimental results.