Alejandro Pérez Vallés

New Distortion and Unbalance Indices Based on Power Quality Analyzer Measurements

Voltage and current waveform distortion are more prevalent on power systems today related to nonlinear loads. The proliferation of loads of this kind and their interaction with the power supply system is increasing the need to use power monitoring equipment to evaluate electric power quality. Measurements show that waveform harmonics and unbalance are variable over time due to changes in load conditions and in the system configuration. Thus, the electrical engineer has a large amount of data available from each phase, acquired using commercial Analyzers. Therefore, it is necessary to find ways to characterize this group of recorded data, to allow proper evaluation of the situation. Two indices, which can be calculated with these measurements, are proposed in this work: a three-phase total demand distortion index and a total unbalance index. In addition, this paper proposes an easy way to characterize the time-varying data to simplify their representation. The exposed procedures are applied to the data registered from an electrical power system, to show the performance of the proposed methods.

Assessment on apparent power indices with hybrid active power filters

This paper presents a method for assessing the quality improvement of the electric power, when compensation equipment based on hybrid active power filters is applied. Power quality indicators that allow to separate the contribution to unbalance of each harmonic and interharmonic of voltages and currents are introduced, calculated with an enhanced procedure. To characterize the behavior of these indices, a hybrid series - active parallel - passive filter, SAPPF, is used for the compensation of a load in a system with unbalance and distortion. The results obtained with the practical cases have allowed to verify the validity of the proposed procedure, and to clarify the interpretation of the unbalance and harmonic distortion indices with this kind of compensation.

Comparative analysis of compensation strategies for series APF based on the electric power dual formulation

Different electrical power formulations have been developed to improve the quality of electrical power. These developments have served to establish different strategies for the control of active power filters (APF). However, most strategies have been applied to APF of parallel connection. These type of compensators are only effective in compensating loads of the harmonic current source type (HCS). In the case of loads called harmonic voltage source (HVS) a series APF is required. The strategies proposed for parallel APFs must be reformulated so that they can be applied to the series APF topologies. In this paper, different compensation strategies based on the dual electrical power formulations are proposed for APF of series connection. A simulation platform designed for this purpose has allowed the evaluation of each strategy under different load conditions. The results obtained let to establish a comparative analysis for different load condition.

Evaluation of the Distortion and Unbalance Emission Levels in Electric Networks

Electrical disturbances have important economic consequences for the consumer and the utilities, a fact which increases from the new electricity regulatory framework. Thus, Electric Power Quality, EPQ, has now become a priority within the field of electrical engineering. Power-quality deterioration is due to transient disturbances (voltage sags, voltage swells, impulses, etc.) and steady state disturbances (harmonic distortion, unbalance, and flicker). Among these are the so-called periodic disturbances such as distortion of the voltage and current waveforms, or unbalanced three-phase systems, [1-2]. This chapter is focused specif‐ ically on harmonic and unbalance phenomena.

ANALISIS DE LAS DEFINICIONES DE DESEQUILIBRIO DE TENSION EN LOS SISTEMAS DE POTENCIA

Documents recently published by IEC and IEEE standard have adopted as a measure of voltage unbalance the relationship between negative and positive sequence components. However, other imbalance indices are usual in practice, such as voltage unbalance defined by the National Electrical Manufacturers Association, NEMA, in USA, or those based on the maximum deviations of average voltages proposed by IEEE in its publications. This article analyzes the different definitions of voltage unbalance introduced in several standards over the last decades. Thus, a comparative assessment of different definitions versus the imbalance factor adopted by IEC has been carried out. This index is considered the true imbalance in this text. To do this, several simulation and experimental setups have been designed. The results obtained have allowed the importance of adopting a definition to achieve a correct imbalance measure in the characterization of voltage asymmetry in electricity networks to be highlighted.