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.

This paper documents the modeling of harmonic sources with nonlinear voltage-current characteristics such as transformers, iron-core reactors, rotating machines, arc furnaces, energy efficient lightings, and some household electronic appliances. The harmonic generating characteristics of these apparatus are reviewed. Different modeling techniques are summarized and suggestions for the use of different models are also provided whenever possible.

This paper reviews the common practice and analytical models for the representation of aggregate linear load in harmonic propagation and distortion studies. Simulation results in this paper demonstrate the high sensitivity of harmonic propagation and distortion to the model type used to represent the load. Comparison of the several load models in the literature shows a significant difference on the system impedance around the dominant resonance. The paper recommends a comprehensive modeling approach that accounts for all major components of the modern load including electronic load and background distortion.

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 comments for applications of these harmonic sources in harmonic modeling and simulation also will be described.

This paper presents three harmonic simulation test systems. The purpose is to demonstrate guidelines for the preparation and analysis of harmonic problems through case studies and simulation examples. The systems can also be used as benchmark systems for the development of new harmonic simulation methods and for the evaluation of existing harmonic analysis software.

Some of the most remarkable issues related to inter- harmonic theory and modeling are presented. Starting from the basic definitions and concepts, attention is first devoted to interhar- monic sources. Then, the interharmonic assessment is considered with particular attention to the problem of the frequency resolu- tion 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 pre- sented are given with references to case studies constituted by pop- ular schemes of adjustable speed drives. Index Terms—Discrete Fourier transform (DFT), frequency res- olution, harmonic analysis, interharmonics.