Contribution of a power multivector to distorting load identification

The identification of harmonic generating loads and the assignation of responsibility for harmonic pollution is an important first step for harmonic control in modern power systems. In this paper, a previously introduced power multivector is examined as a possible tool for the identification of such loads. This representation of power is based on the mathematical framework of Geometric Algebra (GA). Components of the power multivector derived at the point of connection of a load are grouped into a single quantity, which is a bivector in GA and is characterized by a magnitude, direction and sense. The magnitude of this bivector can serve as an indicator of the distortion at the terminals of the load. Furthermore, in contrast to indices based solely on magnitude, such as components derived from any apparent power equation, the proposed bivectorial representation can differentiate between loads that enhance distortion and those with a mitigating effect. Its conservative nature permits an association between the distortion at specific load terminals and the common point of connection. When several loads connected along a distribution line are considered, then an evaluation of the impact of each one of these loads on the distortion at a specific point is possible. Simulation results confirm that information included in the proposed bivector can provide helpful guidance when quantities derived from apparent power equations deliver ambiguous results

Comparison of Nonactive Powers for the Detection of Dominant Harmonic Sources in Power Systems

This paper deals with an innovative technique for the detection of disturbing loads in distorted power systems. The technique is a single-point strategy based on a comparison among different "nonactive"power quantities already proposed in the literature, which are measured at the same metering section. In this paper, the effectiveness of the strategy is discussed, which also considered the errors of the measurement transducers; the analysis is supported by simulation tests, which were carried out on both a simple single-phase system and an IEEE standard three-phase test power system. The latter was used by other authors as a benchmark system for the analysis of multipoint measurement techniques for harmonic pollution monitoring

Locating Harmonic Sources In Electrical Power Systems

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2010Elektrik güç sistemlerine bağlı doğrusal olmayan cihazların çok hızlı artışı nedeniyle, harmonik bozulma seviyesinin ve yerinin belirlenmesine olan ilgi gün geçtikçe artmaktadır. Elektrik güç sistemlerinde harmonik bozulmaya neden olan etkenlerin yerinin saptanması, harmonik bozulmanın seviyesinin düşürülmesi çalışmalarının etkinliğini arttırabilir. Bununla birlikte, besleme gerilimini bozarak elektrik güç sisteminin verimliliğini azaltan sorumlu tüketiciler cezalandırılabilir. Bu tezde, öncelikle iletim sistemlerinde iki-uçlu empedans-tabanlı arıza yeri tespit etme metoduna örnekseme yapılarak, farklı frekanslı harmonik kaynakların yerini tespit etmek için yeni bir yaklaşım geliştirilmiştir. Bu yaklaşımda, ilk olarak harmonik kaynağı ile ölçüm alınan noktalardan biri arasındaki mesafe bir ölçüt olarak kullanılarak harmonik kaynağın yeri tespit edilmektedir. Bu çalışmada ayrıca empedans devreleri yaklaşımına dayanan harmonik kaynağı yerini saptama yöntemi ve ölçü aletlerinin optimum bir şekilde yerleştirilmesi için özgün bir algoritma geliştirilmiştir. Son olarak 30-baralı IEEE test sistemi ile yapılan Monte Carlo benzetimleri, geliştirilen yaklaşımın doğruluğunu ve performansını onaylamaktadır.The level of harmonic distortion and location of harmonic sources is a concern due to the increase in non-linear devices in electric power systems. Harmonic mitigation techniques would be most effective when the location of the harmonic distortion source is known. In addition, responsible parties may be penalized for causing distortion in the supplied power that result in the loss of efficiency in power systems. In this thesis, firstly an approach in analogy to the two-end impedance-based fault location technique of transmission lines is proposed to locate harmonic sources with different harmonic orders. In this approach, the distance from the harmonic source to the one of the metering points is used as a measure to locate the harmonic source in the network. Furthermore, in this thesis a harmonic source location method and an original optimal meter placement algorithm based on impedance network approach are developed. Finally, the Monte Carlo simulation results of the IEEE 30-bus test system verify the performance and accuracy of the new approach.DoktoraPh

Localización y valoración de fuentes de distorsión armónica y/o desequilibrio en redes eléctricas

En la actualidad, los consumos de potencia eléctrica se caracterizan por una amplia variedad de cargas en sus procesos productivos, en muchos de los casos cargas trifásicas/monofásicas constituidas por convertidores electrónicos de potencia. Por otro lado, los sistemas eléctricos están hoy día evolucionando hacia sistemas de generación descentralizados donde las unidades de generación, principalmente de energía renovable, se conectan mediante convertidores electrónicos directamente a las redes de distribución. Los consumos referidos y la generación distribuida, contribuye al crecimiento de las corrientes armónicas y desequilibradas que conllevan, entre otros, a un aumento de las pérdidas de la red, y mal funcionamiento de los equipos. Desafortunadamente, la identificación de estas fuentes de perturbación no puede lograrse por medio de medidas individuales en una sección determinada de un sistema eléctrico. La solución efectiva del problema requiere tener que conocer las medidas simultáneas de los parámetros eléctricos de calidad de todas las acometidas donde estén conectados los consumidores. En efecto, los índices empleados usualmente para valorar la calidad, principalmente la tasa de distorsión armónica, no son apropiados para evaluar la calidad de la energía eléctrica cuando está presente una fuerte distorsión, y especialmente en aquellos casos donde existen múltiples fuentes de perturbación conectadas a la red. Por otra parte, se ha demostrado que las medidas de la calidad de la energía eléctrica llevadas a cabo en una sección de medida determinada de la red, no pueden suministrar la información suficiente al menos sin recurrir a mecanismos de medida invasivos. Así, en la bibliografía se encuentran diferentes enfoques para abordar este tipo de cuestión. Estos pueden clasificarse en dos grupos: métodos de medidas en una sección localizada, y métodos de medida distribuidos multipunto (medidas efectuadas simultáneamente en diferentes secciones de la red). Los métodos basados en medidas realizadas en un punto de la red tienen como ventajas principales su bajo coste y su fácil implementación en las instalaciones, pero en algunas condiciones pueden registrar una información inexacta respecto del estado de perturbación de la red. Por otra parte, los métodos de medidas distribuidas multipunto registran una información más precisa respecto del estado de distorsión y desequilibrio del sistema de potencia completo, aunque en la práctica hasta ahora sean difíciles de realizar y requiera una instrumentación más compleja tanto desde el punto de vista de hardware como de software. Además, este enfoque exige la definición de nuevos índices y los correspondientes métodos de medidas asociados para la evaluación de los niveles de las perturbaciones periódicas en la sección de medida. Este enfoque es el que se considera que puede resolver de forma definitiva la cuestión y el que se plantea en esta tesis. En esta tesis se propone un nuevo índice basado en medidas distribuidas multipunto para la identificación de distorsión armónica y/o desequilibrio. El índice propuesto está construido a partir de términos de potencia dentro del marco del estándar IEEE 1459. El estándar presenta un modelo de descomposición de la potencia aparente en condiciones de distorsión y asimetría, sin embargo, éste carece de una evaluación práctica del desequilibrio causado por la carga. El algoritmo propuesto se define usando un nuevo método de descomposición de potencia aparente que lo separa en cuatro componentes, así el nuevo índice introduce dos novedades significativas. En primer lugar, se define en función de términos de potencia desarrollados según la misma filosofía de trabajo que el estándar IEEE 1459. Y en segundo lugar, los términos de potencias utilizados representan una evolución de los términos del estándar, ya que separan de forma más completa la distorsión y el desequilibrio. La nueva propuesta de índice se valida a partir de dos plataformas: una de simulación en el entorno de MATLAB/Simulink y otra experimental desarrollada en el laboratorio de potencia del grupo de investigación. La tesis se ha organizado de la siguiente manera: en el capítulo I se estudia el problema de la distorsión armónica y el desequilibrio en los sistemas eléctricos de potencia de forma conceptual, además se plantea una clasificación de los métodos de localización de fuentes de perturbación. En el capítulo II se realiza un estudio de los métodos basados en medidas realizadas en un único punto de la red. El capítulo III tiene un doble objetivo, por un lado se presentan los índices distribuidos multipunto más representativos recogidos en la literatura técnica, y por otro, se desarrolla la nueva propuesta de índice de medidas distribuidas para la identificación de fuente de distorsión armónica y/o desequilibrio en la red, basado en términos de potencia en el marco del estándar IEEE 1459. En el capítulo IV, con el objetivo de contrastar y validar la nueva propuesta, se realiza un análisis comparativo de los índices distribuidos multipunto a través de una plataforma experimental. Por último, en el capítulo V se presentan las conclusiones de este trabajo.At present, electric power distribution is characterized by a wide variety of loads at its points of production, with, in most cases, electronic power converters comprising singlephase or three-phase loads. As power networks develop towards decentralized generation systems, more units, largely from renewable sources, are being directly connected to the distribution network through electronic converters. Irregular patterns of consumption alongside this distributed generation, contribute to an increase in harmonic distortion and current unbalance that together lead to an increase in network failure and equipment malfunction. At the same time, the very elements that have allowed the development and modernization of electric power distribution networks are those that display greater sensitivity to the disturbances (that they cause) in the network, endangering the system. Consequently, identification of harmonic distortion and/or unbalanced sources in the system is essential, both to demand responsibility from the originator/s (the electrical supply system and/or customer installation), and to take the necessary measures to solve the problem. The different approaches to tackling this problem can be classified into two groups. The first approach concerns measurements taken from a localized section (single-point), while the second concerns multi-point distributed measurement methods (that is, measurements taken simultaneously at different sections on the distribution network). Single-point measurements offer the advantages of low cost and ease of implementation, but in some conditions the information recorded with regard to the state of network disturbances can be inaccurate. The multi-point methods enables the recording of accurate information regarding the state of distortion and unbalance of the complete power system, and is consequently considered capable of definitively resolving the issue. In practice, however, approaches of this nature have to date proved difficult to perform and require the use of expensive and more complex instrumentation from both a hardware and software perspective. What is required is the definition of new indices and corresponding methods for evaluating of the levels of periodic disturbances in the measurement section. Currently, advances in digital signal processing techniques and the interconnection of equipment allowing real-time communication over communication networks make it feasible to address the practical development of a distributed measurement system aimed at quality power in electrical networks. However, it is necessary to define a distributed index that computes the information received from the different locations. These indices are formed from the combination of three indices that have been extensively used to assess distortion and unbalance by single-point methods. The combination of these presupposes greater success in the identification of periodic disturbances. Tests in different conditions have demonstrated that they cannot always clearly identify the source of disturbance, for which reason new proposals would be welcome. This thesis proposes a new multi-point distributed measurement index for the identification of the sources of harmonic distortion and/or unbalance, based in power terms on the IEEE Std. 1459 framework. The Std. 1459 presents a model of apparent power decomposition terms in conditions of distortion and asymmetry. However, this model lacks a practical assessment of the unbalance caused by the load. The new index algorithm is defined using a new method of apparent power decomposition which separates it into four components. The new index introduces two significant developments. First, it is defined as a function of power terms in the Std. 1459 framework, although it retains a fourth perturbation term. And second, the power terms used represent an evolution of the Std terms that most clearly separate distortion and unbalance. The index is applied and validated by means of an experimental platform connected to a real, low-voltage network. The thesis is organized as follows: in chapter I we study the problem of harmonic distortion and imbalance in electrical power systems in a conceptual way, in addition to a classification of the methods of locating sources of disturbance. In Chapter II a study of the methods based on measurements carried out at a single point in the network is carried out. Chapter III has a double objective, on the one hand the most representative multipoint distributed indices of the technical literature are presented, and on the other, the new proposal for the index of distributed measures for the identification of harmonic distortion source and/or unbalance is presented in the network, based on terms of power within the framework of the IEEE 1459 standard. In Chapter IV, in order to contrast and validate the new proposal, a comparative analysis of the multipoint distributed indices is carried out through an experimental platform . Finally, chapter V develops the conclusions