Non-linear Power System Modeling, Simulation and Analysis in the Frequency Domain using Behavioral Modeling Approaches

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Robert Uhl


Robert Uhl

Team Leader Real Time Simulation and HiL


+49 241 80 49727



In modern power systems, more and more power electronics devices are present. Such components exhibit a non-linear behavior and lead to voltage and current harmonics. Present frequency domain methods assume linear small-signal models, which are no longer valid in the presence of more and more power electronics devices.

This project aims at developing a new power system theory based in the frequency domain. The models of non-linear components are based on measurements and are inspired by the X-Parameters behavioral modeling approach. This approach is currently used solely in microwave engineering and introduces a concept of measurement-based non-linear black-box modeling. This new theory will allow an effective and more accurate study of the operation of power systems without assuming linear behavior of the non-linear components. One exemplary application is the stability analysis of power systems under distorted operating conditions.

In a first step, the measurement-based frequency domain model of a single-phase four diode bridge rectifier was identified. Such a rectifier is a common non-linear passive power system component. The power-level measurements of the component were performed in the ACS lab by using the Flexible Power Simulator (FlePS) as a power amplifier. A FPGA in combination with LabVIEW performs the voltage and current measurements, the post-processing and model identification is done using Matlab.

As a next step, a similar measurement-based model for an active component like an AC/DC converter will be identified. Furthermore, system-level simulations in the frequency domain using such non-linear models will be performed to validate the proposed approach.

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We would like to thank Keysight Technologies for the financial support through the Applications and Core Technology University Research award.