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The wound rotor induction machine (WRIM) presents characteristics that make it attractive as an energy storage system where the energy is stored as kinetic energy in the rotor moving parts. When operating in the doubly fed mode (DFIM), with the rotor fed by a variable frequency power converter, the WRIM behaves as a synchronous machine, differing from the latter in the variable speed operation and larger dumping effect when subjected to disturbances. As the converter only needs to be designed to handle a fraction of the total power, the system can be used at a high level of power. This paper presents the analysis of a Doubly Fed Induction Machine (DFIM) used as a controlled active and reactive power compensator. The simulation and experimental results obtained show that this system can be used for voltage control in a power system as well as load-leveling device. A máquina de indução de rotor bobinado (MIRB) apresenta características que a tornam atrativa para aplicação em sistemas de armazenamento cinético de energia. Quando operando no modo de dupla alimentação, com o rotor sendo alimentado por um conversor eletrônico de potência, a MIRB se comoprta como uma máquina síncrona, com a diferença de poder operar com velocidade variável e apresentar um maior amortecimento quando submetida a distúrbios. O fato do conversor precisar processar apenas parte da potência total do sistema favorece sua aplicação em níveis de potência mais elevados. Este artigo analisa a aplicação da Máquina de Indução Duplamente Alimentada como um compensador controlável de potências ativa e reativa. Os resultados, experimentais e de simulação, apresentados, indicam que este sistema pode ser usado no controle de tensão e no balanço de potência em um sistema elétrico.

2004 11th International Conference on Harmonics and Quality of Power -- 12 September 2004 through 15 September 2004 -- Lake Placid, NY -- 64929, A novel ride-through compensation scheme for an industrial mixer motor/drive system is presented during voltage sags. Experimental results of an industrial mixer motor/drive system have been presented during voltage sags. A ride-through compensation scheme which exploits the surplus energy stored in the dc-link capacitor is introduced. An open-loop control Volts per Hertz boost strategy is used in order to compensate the speed loss during the three-phase balanced voltage sags. Both compensated and uncompensated experimental results are given. Experimental and simulation results shows reasonably good agreement. © 2004 IEEE.

2004 11th International Conference on Harmonics and Quality of Power -- 12 September 2004 through 15 September 2004 -- Lake Placid, NY -- 64929, Modeling and Simnon simulation analysis of an industrial mixer motor/drive system has been done during voltage sags. A novel ride-through compensation scheme for an industrial mixer motor/drive system is presented during voltage sags. From d-q dynamic model of the electrical and mechanical processes, Simnon simulation equations are derived. A ride-through compensation scheme which exploits the surplus energy stored in the de-link capacitor is introduced. Both compensated and uncompensated cases have been simulated. © 2004 IEEE.

The present PhD thesis deals with distribution grid-connected power electronic devices. The main focus has been power quality improvement with power electronic devices. The theoretical aspects and the power quality improvement techniques are presented and discussed. Power electronic devices are then presented, modelled and controlled. Original disturbance identification, power management and current/voltage control methods have been proposed, tested and analysed. A flexible test-bench, composed of a series and a shunt compensator, has been designed and built in order to test the studied control algorithms. These tests have permitted to experimentally evaluate and validate the proposed control algorithms and to make evident several problems that are not always visible on the theory. The conclusions outline the main short and mid term objectives and challenges in the field of power quality improvement devices., La thèse a trait aux systèmes de l'électronique de puissance dédiés aux applications distribution électrique. Une attention particulière a été portée sur l'amélioration de la qualité de l'énergie. A cet effet, les aspects théoriques et les techniques d'amélioration sont décrits et discutés. Les convertisseurs de l'électronique de puissance à même de répondre à la problématique qualité sont ensuite introduits, modélisés et commandés. Des techniques originales d'identification de perturbations, de gestion des puissances actives et réactives ainsi que des commandes éloignées sont conçues, testées en simulation et analysées. Les applications retenues sont le compensateur série à base d'onduleur de tension et le filtrage actif shunt. Ces résultats sont ensuite confrontés à l'expérimental sur un banc conçu et réalisé à cet effet. L'expérience, si elle a conforté la théorie, a permis également de mettre en exergue les problèmes souvent occultés par la théorie. La conclusion reprend ces constatations et trace les objectifs à court et moyen terme.

Voltage sags are one of major concerns in power quality, as they cause serious malfunction of a large number of apparatuses. There are a number of reasons for voltage sags in distribution networks: there is some evidence, however, that in electrical systems located in regions with high value of isokeraunic level, lightning can cause the majority of voltage sags. Data from lightning location systems, which provide an estimation of both lightning flash location and return-stroke current amplitude, can then be used to understand whether lightning is indeed the real cause of circuit breaker operation during thunderstorms-which means, in turn, of voltage sags-or not. Due to the complexity of the problem, the information coming from LLS (lighting location and estimate of lighting current amplitude) are, in general, not enough to infer the origin for voltage sags. It is necessary to suitably integrate them with data from system monitoring, e.g. relevant to the intervention of circuit breakers in primary substations, and with simulation results from of accurate models for computing lighting-induced voltages on complex power networks.

This paper discusses the sensitivity of personal computers and PWM drives to voltage sags and short interruptions on the basis of extensive test results. The results of the following tests are presented in the paper: testing against various types of single-phase, two-phase and three-phase voltage sags and short interruptions, as well as testing with the ideal and non-ideal supply characteristics. Presented test results show that behavior of both equipment types in the general case cannot be described with only one voltage-tolerance curve. Instead, families of voltage-tolerance curves should be used for description of the PCs and PWM drives sensitivity to voltage sags and short interruptions. Special attention is given to similarities in responses between these two equipment types, what is discussed in detail.

The ability of an electrical drive to continue operation without tripping in spite of short duration voltage sags or power supply interruptions is known as Power Failure Ridethrough capability. Critical production processes in industries require the drives to smoothly ride-through during momentary power interruptions. The reliability of the drive is dependent on the maximum duration for which a total power supply failure can be tolerated without process interruption. This paper presents a method to extend the duration of the ride-through in voltage source inverter fed vector controlled induction motor drives with a front end diode bridge rectifier. The proposed method minimises the losses in the system during the ridethrough, thereby enabling a longer ride-through duration. The method only requires a modification of the control software and hence is easy to implement. The paper also briefly describes two conventional methods used for ride-through, and compares the proposed method with the conventional methods to clearly bring out its advantage. Simulation study using MATLAB/PLECS verifies the effectiveness of the proposed method. Hardware implementation of the method on a 30 kW induction machine indicates an extension of up to 34% in the ride-through duration with the proposed method, as compared to the conventional method. � 2015 IEEE.

Voltage sags and interruptions originating on primary and secondary sides of facilities are among the most concerning issues for industrial customers. In the paper a classification approach to costs involved by the mentioned power quality (PQ) disturbances in industrial end-use segment is illustrated. To this aim some of the most diffuse mitigation techniques have been considered. Finally, a case study concerning a novel approach adopted for solving PQ problems in a semiconductor factory has been illustrated and discussed.

The thesis deals with the application of compensators andswitches based on power electronics in AC transmission anddistribution systems. The objective of the studieddevices/equipment is the power flow and voltage control intransmission systems and the mitigation of voltage sags andmomentary interruptions to critical loads in distributionsystems. For validating the power electronics based devices/equipmentdescribed in the thesis, scaled models at a real-time simulatorhave been built. Simulation results of these models arepresented and discussed in the thesis. The equipment studied in the thesis exploit the fast controlactions that can be taken by power electronics devices, whichare much faster than the speed of conventional equipment andprotection systems, based on electromechanical devices. In thisway, the power quality of distribution systems is improved,regarding duration and magnitude of voltage sags (dips) andmomentary interruptions, which are the most relevant types ofdisturbances in distribution systems. The thesis presents some compensators based onforced-commutation voltage-source converters for correctingvoltage sags and swells to critical loads. The seriesconverter, usually denoted Dynamic Voltage Restorer (DVR), hasbeen proved suitable for the task of compensating voltage sagsin the supply network. The use of solid-state devices ascircuit breakers in distribution systems has also been studiedwith the objective of achieving fast interruption or limitationof fault currents. The location and practical aspects for theinstallation of these solid-state breakers are presented. Ithas beenshown that a configuration based on shunt and seriesconnected solid-state devices with controllable turn-offcapability can also provide voltage sag mitigation, without theneed of transformers and large energy storage elements. The operation and control of two Flexible AC TransmissionSystem (FACTS) devices for voltage and power flow control intransmission systems, namely the Static Synchronous Compensator(STATCOM) and the Unified Power Flow Controller (UPFC),respectively, are also studied. A faster response compared totraditional equipment consisting of mechanically based/switchedelements is then achieved. This allows a more flexible controlof power flow and a secure loading of transmission lines tolevels nearer to their thermal limits. The behaviour of thesedevices during faults in the transmission system is alsopresented. Keywords: power electronics, power quality, voltagesags, voltage-source converters, Custom Power, FACTS, real-timesimulations, solid-state devices. NR 20140805

Unified power quality conditioner (UPQC) is a combination of series and shunt active power filters with a common DC link. This device is used to enhance power quality by injecting required amount of Volt-Ampere (VA) into the system. In view of the cost effectiveness, it is desirable to have VA loading of UPQC without compromising the compensation capability. This paper presents a methodology to minimise VA loading of UPQC, considering the effects of unbalance in load and distortions in both load current and source voltage during the compensation of voltage sag with phase jumps in adistribution system. The minimum VA loading of the UPQC is achieved by injecting a series voltage at an optimum angle using series active power filter with respect to the voltage sag. In this paper, a particle swarm optimization (PSO)-based technique is used to minimise the VA loading of UPQC. The proposed method has been validated through detailed simulation studies and the results are presented Copyright � 2012 Inderscience Enterprises Ltd.

Several control schemes specifically designed to operate inverter-based industrial microgrids during voltage sags have been recently proposed. This paper first classifies these control schemes in three categories and then performs a comparative analysis of them. Representative control schemes of each category are selected, described and used to identify the main features and performance of the considered category. The comparison is based on the evaluation of several indexes, which measure the power quality of the installation and utility grid during voltage sags, including voltage regulation, reactive current injection and transient response. The paper includes selected simulation results from a 500 kVA industrial microgrid to validate the expected features of the considered control schemes. Finally, in view of the obtained results, the paper proposes an alternative solution to cope with voltage sags, which includes the use of a static compensator in parallel with the microgrid. The novelty of this proposal is the suitable selection of the control schemes for both the microgrid and the static compensator. The superior performance of the proposal is confirmed by the analysis of the quality indexes. Its practical limitations are also revealed, showing that the topic studied in this paper is still open for further research. Fil: Camacho, Antonio. Universidad Politécnica de Catalunya; España Fil: Castilla, Miguel. Universidad Politécnica de Catalunya; España Fil: Canziani, Franco. Waira Energia SAC; Perú Fil: Moreira, Carlos Javier. INESC Technology and Science; Portugal Fil: Coelho, Paulo. Instituto Politécnico de Tomar; Portugal Fil: Gomes, Mario. Instituto Politécnico de Tomar; Portugal Fil: Mercado, Pedro Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina

©2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The aim of this paper is to study the behavior of a three-phase inverter with an RL filter powered by a renewable energy source and connected to a grid under fault conditions. The novelty of the work lies in proposing a mathematical model which can be solved analytically. So, a comprehensive analytical solution is given, which can be used to describe the behavior of a three-phase inverter under both symmetrical and unsymmetrical faults. Firstly, a complete mathematical model of the system is given. Secondly, a control is applied for both symmetrical (three-phase faults) and unsymmetrical (one-phase and two-phase faults) conditions, making use of the positive- and negative-sequence components for the latter. Finally, a mathematical model for the whole system Is developed. The analytical approach is valid for any fault conditions, either symmetrical or unsymmetrical, which helps in the understanding of the behavior of three-phase inverters connected to a faulty grid and simplifies its study. The analytical model is validated through simulations carried out in Matlab-simulink™.

Power quality problems like voltage dips and sags are presently important issues in the utilities. Major economic losses might appear at the customers due to those failures. This paper presents a power electronic device, which keeps voltage sags away from sensitive loads. It is a dynamic voltage restorer (DVR), which creates a series injection of voltage into the medium voltage grid. Energy storage is keeping the sensitive load running in a limited time. The design and a new control method of a DVR are explained in this paper. The DVR is also tested at medium voltage level (10 kV) and methods to initiate voltage dips are described and implemented. Different test results at 10 kV level show that the DVR keep the voltage to a sensitive load fixed in the case of voltage dips. Furthermore, it is also demonstrated that in the case of a transformer failure the system also works very fine.

The paper deals with the analysis of the possible correlation between cloud-to-ground lightning discharges and relay operations inferred by using the experimental data obtained means of a measurement set-up, installed on an Italian MV distribution network, and a statistical procedure based on the coordinated use of the Italian Lightning Location System (LLS) CESI-SIRF, the monitoring systems of protection manoeuvres and an advanced simulation tool for the calculation of lightning-induced overvoltages. The procedure takes into account the uncertainties related to the estimation of lightning stroke location and current amplitude provided by the LLS. The experimental set-up, composed by a distributed monitoring system, is able to measure a-periodic voltage transients characterized by a frequency content up to 4 MHz. Three of these units have been installed in the feeder of a three-phase overhead distribution network with a total length of 21 km. The same feeder is protected with overcurrent and zero-sequence relays whose operations are recorded by a monitoring system with a 10-ms sampling time. The data collected during one year of operation of the experimental set-up have been analyzed together with the data collected by the LLS for a 144 km2 area covering the equipped feeder and its surrounding area, in order to account for all direct and indirect lightning events that may have caused a relay intervention. The data have been also used to test the calculation model. The paper eventually reports the results of the correlation analysis carried out using the mentioned procedure, which is used to evaluate the probability that a specific event, detected by the LLS and time-correlated to relay operation, may have been the cause of a flashover in the network.