Three-phase Network Research Articles

Recommendation in an Evolving Service Ecosystem Based on Network Prediction

Service computing plays a critical role in business automation and we can observe a rapid increase of web services and their compositions nowadays. Web services, their compositions, providers, consumers, and other entities such as context information, collectively form an evolving service ecosystem. Many service recommendation methods have been proposed to facilitate the use of services. However, existing approaches are mostly based on all-time statistics of usage patterns, and overlook the temporal aspect, i.e., the evolution of the ecosystem. As a result, recommendation may consist of obsolete services and also does not reflect the latest trend in the ecosystem. In order to overcome this limitation, we propose an innovative three-phase network prediction approach (NPA) for evolution-aware recommendation. First, we introduce a network series model to formalize the evolution of the service ecosystem and then develop a network analysis method to study the usage pattern with a special focus on its temporal evolution. Afterward a novel service network prediction method based on rank aggregation is proposed to predict the evolution of the network. Finally, using the network prediction model, we present how to recommend potential compositions, top services and service chains, respectively. Experiments on the real-world ProgrammableWeb data set show that our method achieves a superior performance in service recommendation, compared with those that are agnostic to the evolution of a service ecosystem.

A New Optimization Model for Distribution Siting and Sizing in Unbalanced Three-phase Networks for Loss and Cost Minimization

Since distribution substations connect transmission lines and distribution system, planning these substations is a very important step in scheduling process of power system and optimal placement of distribution transformers for reducing the involved loss is of concern. In this paper a new model is (proposed for solving optimal substation planning of distribution networks. In the objective function, we have included both capital and operation (loss) costs. The optimization problem is solved by genetic algorithm (GA). In order to evaluate the effects of load imbalance in low-voltage system, a group of balanced one-phase and three-phase and imbalanced three-phase in 4-wire system are used. As a case study, the optimization model is tested on the 33-bus system. Simulation results show that the total cost is reduced by balancing the load of different phases. Also, the results confirm a 48 % reduction in loss and an 11 % reduction in costs of the network planning. Moreover influence of energy cost change and load change on distribution network planning is evaluated by investigating on 33-bus system.

On Determination of Arc Currents in Three-Phase Single-Chamber Plasma Generators

Two methods of determining the arc currents in three-phase single-chamber alternating-current generators are presented. In the first method, the current traversing one of the electrode spacings in a three-phase network is disregarded. The second method is based on the consideration of the general mechanisms of the gas flows around arcs. In this method, the volt-ampere characteristic of an arc discharge is constructed from the calculated values of the voltage drop across the arc that are closest to the measured values of this drop.

Harmonic Penetration Method for Radial Distribution Networks

Abstract This work presents a method for calculating harmonic voltages and currents in radial distribution networks. The proposed method is an extension of the backward/forward sweep method for load flow studies in distribution systems and as such preserves its good convergence characteristics besides of not requiring of any network matrix. The method was tested on an eight-node one-phase radial test feeder and results were similar to those that were obtained by the well-known current injection method. Also it was tested on a 2000-node network, showing this way that this is a more suitable method for large three-phase radial distribution networks.

High Performances of Five–Phase Induction Machine Feeding by A [3 × 5] Matrix Converter

Abstract In this paper, we study an analytic technique to control matrix converter for a four-quadrant five-phase induction machine drive with use PWM five intervals modulation strategy. The multiphase induction machine is feeding by a matrix converter using a three-phase network. Special emphasis is given to the sinusoidal five phase voltage in the output and five phase voltage input current modulation. Simulation results are presented.

Two-Wire Distribution System for Power Supply to Three-Phase Rural Facilities

Nowadays, the electric power supply to rural facilities is commonly composed by single-phase medium voltage grids. Eventually, some of these rural facilities require the use of more significant driving loads, making necessary the replacing of the single-phase networks by a new medium voltage three-phase network. Thus, despite the fact it is a new or an existing facility, the construction costs related to a new medium voltage three-phase grid, which may have some miles long, could cripple investment to be made by the farmer as well as increase utility tariffs due to higher costs of the three-phase distribution networks in rural areas. In this context, this paper presents an innovative and low cost power supply to attend three-phase rural facilities through a new two-wire distribution system.

Performance of Three-Phase Analog Network Coding with Relay Selection in Nakagami-m Fading

In this letter, we investigate the performance of a two-way multi-relay system employing three-phase analog network coding (ANC) with best relay selection over independent and non-identically distributed Nakagami-m fading channels. Specifically, we derive a tight closed-form expression for the overall system outage probability. We also derive an asymptotic outage expression in high signal-to-noise ratio (SNR) regime, from which the diversity order and diversity-multiplexing tradeoff are examined. In addition, we present an optimal relay power allocation to minimize the overall system outage. Numerical and simulation results validate the theoretical analysis and demonstrate the advantages offered by the considered scheme.

Neutral conductor current in three-phase networks with compact fluorescent lamps

In this paper, expressions of the neutral conductor current in three-phase networks with compact fluorescent lamps (CFLs) are obtained from a CFL “black-box” model proposed in the literature. These expressions allow studying and performing a sensitivity analysis of the impact of CFLs on neutral current. The influence of CFL model parameters, as well as supply voltage unbalance, number of CFLs per phase and different types of CFLs per phase, on the neutral current is also investigated. The obtained results are validated with measurements and PSCAD/EMTDC simulations.

Development of a rule selection mechanism by using neuro-fuzzy methodology for structural vibration suppression

The development of neuro-fuzzy systems by integrating neural networks and fuzzy systems is desired because such systems can adjust fuzzy membership functions and produce fuzzy inference rules by case-learning without the need for experts or experiments. It has been applied to various fields, but there has been no detailed study of the various neuro-fuzzy models applicable to rule generation. In this paper, an experimentally verified five-layer and three-phase network is presented, which shows the effectiveness with which the neuro-fuzzy system automatically determines membership functions and selects activation fuzzy rules using both system identification and vibration control examples in engineering applications.

Diode–capacitor voltage multipliers combined with boost-converters: topologies and characteristics

Various topological modifications of diode–capacitor voltage multipliers are considered. All the topologies are based on two known schemes: Cockcroft–Walton and Dickson. These topologies are built combined with a boost-converter, operating at a high switching frequency. Such a solution allows reducing the values of the capacitors. The proposed topologies can also be used by feeding them directly from a three-phase network through the regular rectifier; in this case the influence of such circuits on a supply network is reduced. A number of novel modifications of multipliers, having their specific features, are obtained. The procedure of calculating the output voltage, depending on the capacitor values and load parameters is proposed and the design formulas for the output voltage of some of the schemes are developed. It is shown that a decrease in the output voltage is caused by some sort of internal resistance. The essentially similar operating modes of different topologies are characterised by a different value of such a resistance, and accordingly by a different internal voltage drop. Dynamic models for some of the proposed topologies are also developed. The computer simulation and the experimental results proved the theoretical expectations.

Enhancing Electric Power Quality Using UPQC: A Comprehensive Overview

This paper presents a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels. This is intended to present a broad overview on the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. It is noticed that several researchers have used different names for the UPQC based on the unique function, task, application, or topology under consideration. Therefore, an acronymic list is developed and presented to highlight the distinguishing feature offered by a particular UPQC. In all 12 acronyms are listed, namely, UPQC-D, UPQC-DG, UPQC-I, UPQC-L, UPQC-MC, UPQC-MD, UPQC-ML, UPQC-P, UPQC-Q, UPQC-R, UPQC-S, and UPQC-VA. More than 150 papers on the topic are rigorously studied and meticulously classified to form these acronyms and are discussed in the paper.

Direct control of 4-Leg 4-Level Flying Capacitor Converter for an Active Filtering Application

The quality of electrical energy in the distribution systems is a priority, from the producer of energy to the consumer. The increased consumption pushed both sides to seek solutions incorporating the cost of energy. Therefore, more and more 4-leg converters appears in order to control the neutral current appearing during unbalanced load operation on three-phase network connections. This structure of conversion is controlled by pulse width modulation techniques and more specifically by SVM (Space Vector Modulation). This work is therefore interested in the control of a 4-leg flying capacitor multilevel structure, using a direct control, with a geometrical approach to define adequate duty cycles for each calculation period. The control algorithm determines the status of switches providing balancing voltage capacitors and control of absorbed currents, with a large dynamic range adjustment from a SVM - 3D. The qualities of the algorithm are shown through simulation tests.

Steady-State Model and Power-Flow Analysis of Single-Phase Electronically Coupled Distributed Energy Resources

This paper develops and presents the steady-state, fundamental-frequency model of the single-phase distributed energy resource (DER) unit which utilizes a single-phase voltage-sourced converter (VSC) as the interface medium. The model represents: 1) different operating and control modes and 2) the operational constraints and limits of the VSC and the host grid. The model is included in a sequential power-flow analysis method using: 1) a backward-forward sweep algorithm for single-phase laterals and 2) a sequence-components frame solver for three-phase networks. The interface-VSC operating limits are accommodated in the power-flow algorithm as an interleaved step to increase computational efficiency of the power-flow analysis tool. Case studies are conducted to evaluate and verify 1) the accuracy of the proposed model and 2) the computational efficiency of the power-flow algorithm.

A robust 18-pulse diode rectifier with coupled reactors

A robust 18-pulse diode rectifier with coupled reactorsThe article presents the principle of operation and selected results of simulation and laboratory tests of the 18-pulse rectifier system with coupled reactors and small series active power filter. The presented system makes it possible to reduce, especially in distribution supply networks, undesired higher current harmonics. The 18-pulse nature of operation of the rectifier is reached using a set of coupled three-phase network reactors (CDT and CTR). The simultaneous use of the coupled reactors and the small active power filter provides opportunities for reduction of the supply current distortion, especially in case of voltage harmonic distortion and voltage unbalance.

Generalized Modeling of Three-phase Overhead Distribution Networks for Steady State Analysis

This paper presents a generalized approach for three-phase networks with ground return, from which Single wire earth return and conventional three-phase networks are obtained. The resulting model allows a more accuracte analyses based on ground resistivity, losses and high-impedance faults location. The modeling starts based on the Single wire earth return leading to the three-phase one. The general three-phase network with ground return model is presented and can be seen as three single wire earth return with different geografic routes. Analysis and discussions about the model related to ground resisistivity, feeders lenght, and distribution systems aplication are included.

Compensation for reactive and distortion powers in four-wire three-phase network using active filter

A circuit of a compensator of reactive and distortion powers is developed for a four-wire, three-phase network constructed based on the active filter and studied.

DSTATCOM topologies for three-phase high power applications

This paper proposes distribution static compensator topologies for application in three-phase high power distribution systems. These topologies overcome both the voltage and current rating constraints imposed by the semiconductor switches by the use of three single-phase multi-secondary transformers. Five topologies, namely, four leg-group, three leg-group split-capacitor, H bridge-group, three leg-group and two leg-group are suggested. These can effectively compensate unbalance, harmonics and low power factor of the load currents. Apart from the use of minimum number of current sensors and a single capacitor, the control circuit is very simple. It provides the electrical isolation and security deemed essential for high voltage systems. A detailed comparison is made for these topologies. Based on the hardware requirement and compensation quality, the four leg-group and three leg-group topologies are shown to be superior than the other structures for application in three phase four-wire and three-wire systems respectively. They are validated through extensive simulation studies using PSCAD in a three-phase four-wire power network with non-linear unbalanced load. Experimental verification is conducted for H bridge-group topology on a single phase system using a DSP-based prototype laboratory model.

Exploiting the Radial Distribution Structure in Developing a Fast and Flexible Radial Power Flow for Unbalanced Three-Phase Networks

The radial distribution network structure is exploited in developing a fast and flexible radial power flow (FFRPF) solution technique. The cornerstone of this technique is constructing one single building block matrix, called the radial configuration matrix (RCM), which is utilized in carrying out the radial power flow backward/forward iterative steps. The RCM is designed to have a small condition number with a determinant and all of its eigenvalues be equal to one to ensure its invertibility. By incorporating this matrix and its direct descendant matrices in solving the power flow problem, the CPU execution time is decreased compared with other methods. The FFRPF method is flexible in accommodating any changes that may take place in an existing radial distribution system since these changes can be exclusively incorporated within this matrix. The FFRPF is tested by using several balanced and unbalanced three-phase radial distribution systems.

High-voltage power inverter of the generator “Energy-2” for electromagnetic soundings and monitoring of the earthquake source zones

Development of powerful generators of the alternating current working from an industrial network in a wide spectrum of ULF-ELF frequencies range (0.1–200 Hz) is a prospective direction of researches in the field of creation of effective means for electromagnetic monitoring of earthquakes focuses. The present article is devoted to description of the successive stage of works on creation of generator “Energy-2” with capacity up to 200 kW, operating from an industrial three-phase network of 380 V voltage and frequency of 50 Hz. The schematic concept, element base and parameters of the output high-voltage power inverter of up to 1100 V voltage and 400 A current are described. In the course of designing the design documentation was developed, the drawings and circuits were made, the accessories were got, bearing structures were manufactured in skilled-industrial workshops, as well as heat-protective units radiators and ventilators, settlement-theoretical works and computer modeling was carried out. The main basic element of novelty was development of the system providing the programmed (arbitrary) form of current signals in a wide spectrum of frequencies from 0.1 to 200 Hz at power consumption of up to 200 kW. The created unit of the high-voltage inverter is designed for installation in the car body of motor vehicle ZIL-131 in the set with other units of multipurpose generator “Enerrgy-2” with the capacity of up to 200 kW. The important feature of the inverter is its multifunctionality. It permits to use the generating complex Energy-2 for monitoring of earthquake focuses in one of three modes frequency sounding, formation of the field or induced polarization. Selection of on of three monitoring modes depends on the characteristics of seismically active environment and purposes of the Earth crust sounding.

Rotor Failures Diagnosis of Squirrel Cage Induction Motors with Different Supplying Sources

The growing application and the numerous qualities of induction motors (IM) in industrial processes that require high security and reliability levels has led to the development of multiple methods for early fault detection. However, various faults can occur, such as stator short-circuits and rotor failures. Traditionally the diagnosis machine is done through a sinusoidal power supply, in the present paper we study experimentally the effects of the rotor failures, such as broken rotor bars in function of the ac supplying, the load and show the impact of the converter from diagnosis of the machine. The technique diagnosis used is based on the spectral analysis of stator currents or stator voltages respectively according to the types of induction motor ac supplying. So, four different ac supplying are considered: ? the IM is directly by the balanced three-phase network voltage source, ? the IM is fed by a sinusoidal current source given the controlled by hysteresis, ? the IM is fed (in open loop) by a scalar control imposing through ratio V/f=constant, ? the IM is controlled through a vector control using space vector pulse width modulation (SVPWM) technique inverter with an outer speed loop.