A.E. Emanuel

Bio: A.E. Emanuel is an academic researcher from Worcester Polytechnic Institute. The author has contributed to research in topics: Current transformer & Total harmonic distortion. The author has an hindex of 12, co-authored 15 publications receiving 1177 citations.

Practical definitions for powers in systems with nonsinusoidal waveforms and unbalanced loads: a discussion

Abstract: Existing definitions for power terms in alternating current systems work well for single-phase and three-phase systems where both voltages and currents are sinusoidal with respect to time. This paper clarifies and proposes definitions for power terms that are practical and effective when voltage and/or currents are distorted and/or unbalanced. It also suggests definitions for measurable values that may be used to indicate the level of distortion and unbalance.

Guide for assessing the network harmonic impedance

Abstract: The objective of this report is to provide practical guidance for assessing power system harmonic impedance, taking into account the considered network voltage (LV, MV or HV), the disturbing load importance (small or great contribution to the power network pollution) and the analytical and computational tools available.

Induction motor thermal aging caused by voltage distortion and imbalance: loss of useful life and its estimated cost

Abstract: This paper reports the effect of voltage distortion and imbalance (VDI), on the thermal aging of the insulation of low voltage induction motors. The study is based on a detailed thermal modeling of actual motors in the 2 to 200 HP range. The dollar value of the useful life lost was estimated for different VDI conditions. Two important conclusions were reached: First; voltage subharmonics have a dramatic effect on motor thermal aging. Second; the overall cost of motor loss of life due to harmonic pollution and voltage imbalance, in the US today, is estimated to be in the range of 1 to 2 billion dollars per year.

A Novel Approach to Current Transformer Characterization in the Presence of Harmonic Distortion

Abstract: The current transformer (CT) performance under distorted waveform conditions is usually characterized by means of the frequency-response test. In this paper, a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase-angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency-response approach for the evaluation of CT performance under distorted waveform conditions is not a reliable method.

A review of active filters for power quality improvement

Abstract: Active filtering of electric power has now become a mature technology for harmonic and reactive power compensation in two-wire (single phase), three-wire (three phase without neutral), and four-wire (three phase with neutral) AC power networks with nonlinear loads. This paper presents a comprehensive review of active filter (AF) configurations, control strategies, selection of components, other related economic and technical considerations, and their selection for specific applications. It is aimed at providing a broad perspective on the status of AF technology to researchers and application engineers dealing with power quality issues. A list of more than 200 research publications on the subject is also appended for a quick reference.

Comparison of Control Strategies for Shunt Active Power Filters in Three-Phase Four-Wire Systems

Abstract: Strategies for extracting the three-phase reference currents for shunt active power filters are compared, evaluating their performance under different source and load conditions with the new IEEE Standard 1459 power definitions. The study was applied to a three-phase four-wire system in order to include imbalance. Under balanced and sinusoidal voltages, harmonic cancellation and reactive power compensation can be attained in all the methods. However, when the voltages are distorted and/or unbalanced, the compensation capabilities are not equivalent, with some strategies unable to yield an adequate solution when the mains voltages are not ideal. Simulation and experimental results are included

Interharmonics: Theory and Modeling

Abstract: 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.

A digital controlled PV-inverter with grid impedance estimation for ENS detection

Abstract: The steady increase in photovoltaic (PV) installations calls for new and better control methods in respect to the utility grid connection Limiting the harmonic distortion is essential to the power quality, but other requirements also contribute to a more safe grid-operation, especially in dispersed power generation networks For instance, the knowledge of the utility impedance at the fundamental frequency can be used to detect a utility failure A PV-inverter with this feature can anticipate a possible network problem and decouple it in time This paper describes the digital implementation of a PV-inverter with different advanced, robust control strategies and an embedded online technique to determine the utility grid impedance By injecting an interharmonic current and measuring the voltage response it is possible to estimate the grid impedance at the fundamental frequency The presented technique, which is implemented with the existing sensors and the CPU of the PV-inverter, provides a fast and low cost approach for online impedance measurement, which may be used for detection of islanding operation Practical tests on an existing PV-inverter validate the control methods, the impedance measurement, and the islanding detection

Hybrid filters for power quality improvement

Abstract: Solid-state controllers are widely used to convert AC power for feeding number of electrical loads such as adjustable speed drives, furnaces, power supplies etc. Some of these controllers behave as nonlinear loads because they draw nonsinusoidal current from the AC mains. Filter technology for improving power quality of such loads has matured to a reasonable level. Moreover, hybrid filters are considered one of best options for improving power quality for a number of considerations. A comprehensive review of hybrid filters configurations is given: their control approaches, state of art, design considerations, selection criteria, potential applications, latest trends, future developments and their comparative features. A broad review of the status of hybrid filters to researchers, design and practice engineers dealing with power quality improvements is presented. A classified list of more than 150 research publications on the hybrid filters is also given for quick reference.