Some of the most remarkable issues related to interharmonic theory and modeling are presented. Starting from the basic definitions and concepts, attention is first devoted to interharmonic sources. Then, the interharmonic assessment is considered with particular attention to the problem of the frequency resolution and of the computational burden associated with the analysis of periodic steady-state waveforms. Finally, modeling of different kinds of interharmonic sources and the extension of the classical models developed for power system harmonic analysis to include interharmonics are discussed. Numerical results for the issues presented are given with references to case studies constituted by popular schemes of adjustable speed drives.

Interharmonics: Theory and Modeling

This paper proposes a new method to model the harmonic generating characteristics of AC/DC converters. The model transforms the time domain nonlinear characteristic of the converter into a frequency domain linear admittance matrix. The matrix represents the coupling among the converter AC side harmonic voltages and currents accurately and it does not vary with the harmonic conditions of the system. The proposed model opens up a new way to conduct harmonic power flow studies. This paper presents the theoretical foundation and analytical derivation of the admittance model for both single-phase and three-phase bridge rectifiers. Potential applications of the model are discussed.

http://www.ece.ualberta.ca/~apic/papers/Power_Quality/PQ-2007-%20Harmonic%20Matrix%20Model%20for%20Converter.pdf

A Harmonically Coupled Admittance Matrix Model for AC/DC Converters

Harmonic transfer from DC-side to AC-side and vice-versa through a three-phase bridge power converter is treated by using space vectors. The dependency of the relative frequency of a harmonic and its sequence (positive/negative) is illustrated. It is shown that the derived relationships are valid for both voltage-source and current-source power converters. Thereby, the relationships for the frequency transformation through power converters are also valid for both voltage and current harmonics. This analytical method is validated by digital simulations with EMTP software.

General analysis of harmonic transfer through converters

This paper presents a review of characteristics and modeling of major power electronic types of harmonic sources for the power system harmonic analysis. The power electronic switching types of harmonic sources to be reviewed include static power converters, static var compensators (SVCs), and cycloconverters. Discussions and comtnents for applications of these harmonic sources in harmonic modeling and simulation also will be described.

Characteristics and Modeling of Harmonic Sources-Power Electronic Devices

The problem of modeling multi-power converter systems in presence of harmonic and interharmonic distortion is considered. Specifically, current source rectifiers are considered as distortion sources, some supplying DC motors and the remaining supplying inverters feeding AC machines. The classical analogue, frequency domain and time domain models proposed in the literature to study harmonic distortion in a multi-power converter system are considered and, for each model, suitable extensions to include the interharmonic distortion are presented and critically analysed. The results of several experiments are reported to show the usefulness and to compare the accuracy of the different extensions considered. >

Harmonic and interharmonic distortion modeling in multiconverter systems

Power converters are known to be generators of harmonics on both their AC and DC sides. They also transfer existing harmonics from one side to the other side with an associated change of frequency. Analysis techniques that can be used to calculate these transferred harmonics using amplitude modulation (AM) theory are proposed. The authors also show how, in a high-voltage direct-current (HVDC) link, the converters can intercouple the AC and DC systems and can thus act as a transfer medium for harmonics. Examples that show how to calculate these harmonics are given and comparisons are made with a computer-aided design (CAD) model as a check on the accuracy of the method. >

R. Yacamini

Papers

Harmonic transfer through converters and HVDC links