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Electric Power Quality and Supply Reliability Conference (PQ), 2012

Date 11-13 June 2012

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  • The 8th International Conference 2012 Electric Power Quality and Supply Reliability [front and back cover]

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  • 2012 electric power quality and supply reliability [front matter]

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  • Contents

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  • Authors index

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  • The comparison of active and reactive magnetic couplers

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    In this paper there are researched and compared three types of cylindrical magnetic couplers (MC): active MC, reactive MC with yoke and reactive MC without yoke. The comparison is made by the couplers' maximal mechanical torque, which is their main characteristic. The torque is calculated applying software QuickField by designing the magnetic field. The QuickField is based on the finite elements method. It is researched and recommended a new type of reactive MC. View full abstract»

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  • Modeling and classical control of unidirectional Vienna rectifiers

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (143 KB) |  | HTML iconHTML  

    Operation of a unidirectional Vienna rectifier is described in the paper using basic electrical circuit laws only without referring to the space vector theory, typically employed in the literature. An average model is derived for a general unbalanced load and classical control theory is employed to construct the control laws for a three-loop control structure. Simulation results are given to validate the presented approach. View full abstract»

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  • Analysis and prototyping of a low-speed small scale permanent magnet generator for wind power applications

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (446 KB) |  | HTML iconHTML  

    Many companies engaged in wind generator development are investigating permanent magnet generators (PMG) mainly because of higher efficiency over a broad range of wind speed and reduced costs of maintenance. One important parameter of PM generators is the primary magnetic flux that has certain influence to no load voltage of the machine. Thus, needs for efficient calculation methods for primary magnetic field is required. Finite element method is one of the most common and efficient way to analyze the magnetic flux of the machine. But on the other hand it is relatively complicated calculation method and it might be incomprehensible. Analytic calculation or calculations based on reluctance network are comprehensive and suitable for engineers-designers. This paper deals with the primary magnetic field analysis and basic winding calculations by an example of 54 slots and 20 poles PM synchronous generator. Modeling of the primary magnetic field distribution by the finite element method in software FEMM is described. Results from the analytic calculations and the finite element method are compared with experimental data of PM prototype generator study. View full abstract»

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  • Testing results of slow speed electrical machine, that can operate as a synchronous or double fed induction generator

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (637 KB) |  | HTML iconHTML  

    This paper posses the construction of the electrical machine, which has the ability to operate as a synchronous generator with electromagnetic excitation or double fed induction generator. This generator can be applied for slow speed applications without using the gearbox e.g. wind turbine. The generator is multi pole with all of the windings placed on the stator. Rotor is tooth-like and has no windings on it. Primary winding is three phase, secondary winding is one phase. The testing results and practical research are also presented in the paper. View full abstract»

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  • Investigation of molten metal mixing in a DC electric arc furnace with added AC component on different frequencies

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    This paper describes flowing of molten metal in a novel electric arc furnace. Combined AC and DC components are used in the supply system for the furnace. Finite element method is used to investigate the impact of AC component frequency on the flowing of molten metal. View full abstract»

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  • Dual scheme based mathematical modeling of Magnetically Controlled Shunt Reactors 6–500 kV

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB) |  | HTML iconHTML  

    Topicality of mathematic modeling of Magnetically Controlled Shunt Reactors (MCSR) as a network element using common existing software elements is shown in the article. Principles of the MCSR dual scheme creation as a thyristor controlled reactor or a static var compensator (in case of modeling of Source of Reactive Power, including a MCSR and a capacitor bank) are explained. Principles of development the mathematic model of the MCSR dual scheme are demonstrated. Example of development and application of MCSR dual mathematical model for calculating steady-state modes of high-voltage electric grid is shown. The potential of the MCSR dual mathematic model application for development of the algorithm of MCSR (SRP) automatic control at the point of connection to electrical grid is assessed. View full abstract»

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  • Study and verification of a slow speed PM generator with outer rotor for small scale wind turbines

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB) |  | HTML iconHTML  

    This paper considers the study of a directly driven low-speed permanent magnet synchronous generator specially constructed for a vertical axis wind turbine. The studied PM generator with outer rotor construction offers an alternative to fix the wind turbine directly to the end-disk of rotor. As an advantage of the outer rotor PM generator construction it is easier and more reliable to fix the magnets on the rotor active surface. An analysis to optimize the active length of both stator magnetic core and air-gap has been presented. Cogging torque has been analyzed to reduce it by slot skewing. Electromagnetic simulations of the PM generator were performed by using finite element analysis and the SPEED software. A 5 kVA PM generator was designed, manufactured and tested. The test results of the prototype PM generator have been analyzed and compared with the calculated characteristics and data. View full abstract»

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  • Analysis of the eccentricity in a low-speed slotless permanent-magnet wind generator

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    This paper presents the analytical analysis of different eccentricities in the rotor of a novel slotless wind power generator. The analytical expressions for the air gap eccentricity have been derived and the effects of these eccentricities on the air gap flux density, the resultant unbalanced magnetic pull and the induced emf are investigated. The analysis shows a strong pull in the case of static eccentricity, which is not seen when the case of elliptic eccentricity for example. The analysis shows also that the induced emf per coil can vary very much but due to the series connection of the coil per phase emf is uniform but has higher rms value than in the case of healthy machine. The analytical equations are verified for the case of healthy machine on a constructed laboratory prototype. View full abstract»

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  • Detection of broken bars in frequency converter fed induction motor using Park's vector approach

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (105 KB) |  | HTML iconHTML  

    This paper presents the experimental study of induction motor broken rotor bars diagnostics. Fault tests are performed on a machine with 3 broken bars, driven through a frequency converter. Park's vector approach is used as an analyzing tool to detect the broken rotor bars. Park's vector patterns in case of stator current and voltage are investigated. Results of the tests and discussion are presented. Necessity for further study is pointed out. View full abstract»

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  • Three-phase multilevel converter voltage quality bounds

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    Multilevel converters synthesize a staircase voltage waveform, resulting in a high voltage quality. Using a practical time domain approach, lower and upper bounds for voltage quality of three-phase multilevel converters are derived. The voltage quality bounds are introduced as closed-form analytical expressions for an arbitrary number of voltage levels and different modulation indices. They allow an analytical description of the behavior of multilevel converters. In comparison with PWM voltage quality, the lower and upper bounds may be useful for a fair classification of different switching methods and a first layout of multilevel converters. View full abstract»

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  • The self-extinguishing current limit and the arc-burning time of compensated 20-kV-power-grids

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6085 KB) |  | HTML iconHTML  

    The actual valid self-extinguishing current limit of 20-kV-compensated power grids, written in the VDE 0228 is 60 A. This limit is based on trials from the years 1963 done by M. Erich und H. Heinze. In the year 1981 K. H. Koch presented results of new earth-fault trials. He concluded that the self-extinguishing current increases for larger power grids. An afresh scientific interpretation of both experiments leads to a novel proposal for a self-extinguishing current limit for compensated 20-kV-power-grids. This novel self-extinguishing current limit would allow the extension of current compensated power grids. Further the medium arc-burning time for compensated power grids is discussed. View full abstract»

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  • Power quality of supply characterization in the Portuguese Electricity Transmission Grid

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (537 KB) |  | HTML iconHTML  

    REN - Rede Eléctrica Nacional S.A., as the concessionaire of the Portuguese National Electricity Transmission Grid (RNT), has an important role in electrical energy quality to the final customer. Continuity of supply general/individual indicators and parameters are defined in accordance to the regulatory legislation stated in the Regulamento da Qualidade de Serviço de Portugal (RQS). Voltage quality assessment is done by REN and is based on a monitoring plan that includes voltage characteristics measurement at selected delivery and internal points. A study was conducted in order to characterize all the bus bars that were monitored between 2008 and 2010. It was used a simple methodology based on labeling the power quality. On this paper, it will be shown this methodology and the results obtained in characterizing the delivery points of the Portuguese Electricity Transmission Grid for the period 2008-2010, as well as other RENs quality of supply results in the last years. View full abstract»

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  • Contemporary and future aspects of cost effective power quality monitoring — Position paper of CIGRE WG C4.112

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB) |  | HTML iconHTML  

    During the last decade the performance of power quality monitoring equipment has increased, while prices of monitors have continuously decreased. Due this trend network operators have more and more intensified their power quality measurement activities. The number of measured parameters and sites is growing continuously. At the same time these new opportunities cause power quality data management and analysis to become an increasing complex challenge. These new challenges will be addressed by the CIGRE working group C4.112 “Guidelines for Power quality monitoring — measurement locations, processing and presentation of data”, which was established in January 2011. The main intention of its work is the development of a coherent set of guidelines for power quality monitoring in existing and future power networks. Based on a clear identification of different objectives all design aspects for an efficient and cost effective power quality monitoring will be covered by the working group in a holistic way. The paper presents first results of the working group and is especially focused on the cost/benefit aspects of the design process of power quality monitoring systems. After a brief introduction the paper gives an overview of the objectives for power quality monitoring and the different aspects that has to be considered while designing a power quality monitoring system. Next the design aspects of larger monitoring systems are discussed in more detail. Some practical recommendations as well as first ideas of new approaches for future monitoring systems are given. View full abstract»

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  • Harmonic analysis with Symmetrical Space Phasor Components

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    The Symmetrical Space Phasor Components are a second transformation following the well-known transformation of the phase quantities into space phasor and zero sequence. With them it is possible to immediately indicate an occurring voltage or current unbalance in an electrical power network. Furthermore the unbalance can be assigned to a specific harmonic group. View full abstract»

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  • Comparison of wavelet and Fourier analysis in power quality

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1965 KB) |  | HTML iconHTML  

    To guarantee high power quality the monitoring of the power grid is essential part of the process. The secure the best possible supervision of the power quality novel methods for the detection of power quality disturbances have to be considered. State of the art of power quality monitoring in the case of harmonics is the Fourier Transform. This kind of transform is basically used for stationary signals. During the last years the wavelet analysis has found some acceptation in the power quality community. This kind of transform is especially used for transient signals. It has the advantage that the transformation allows information about the time and the frequency of the power quality disturbance. The aim of this paper is the comparison of different Fourier and wavelet algorithm. Especially the application on inter-harmonics, transient harmonics and high frequency harmonics in the range above 2 kHz is investigated. The advantages of the different algorithms shall be discussed. The paper will be a help for power quality experts to find the best algorithm out of a set of well-established and novel algorithms for their problems. View full abstract»

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  • Influences on safety issues for inverter supplied grid structures

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    In the field of low voltage systems protection devices like fuses and residual current devices (RCDs) are generally implemented. Because of their high sensitivity residual current devices are very commonly used for protection against electric shock. A part for the fact that inverters may produce voltages with considerable harmonic content also RCDs deserves special attentions. Due to the increasing number of electrical equipment in the low voltage grid producing disturbing currents different RCD types (type AC, A and B) are investigated under certain conditions. For example the influence of disturbing non-sinusoidal, pulse-shaped currents or harmonics in the fault current regarding on the tripping current or on the tripping time of the RCD is analyzed. View full abstract»

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  • Electricity consumption analysis and power quality monitoring in commercial buildings

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB) |  | HTML iconHTML  

    The results of the analysis of the electricity consumption and power quality indicators in two office buildings are presented. It comprises electricity consumption and power quality during work days and weekends. The consumption data analysed is from a one year period and the power quality analysis is based on a one week measuring period. The aim of this analysis is to determine the current situation in these buildings in order to study the possibilities and limitations to implement different energy efficiency measures. In addition to the energy efficiency point of view, the problem is also addressed together with the power quality aspects. View full abstract»

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  • Flicker source identification in meshed high voltage grids

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (119 KB) |  | HTML iconHTML  

    This paper describes a method to calculate the individual flicker emission of specific disturbers by means of simultaneous flicker level measurements in different bus bars of a meshed grid. The method is based on former investigations regarding the flicker propagation in meshed networks. With adequate flicker level measurements, the cubic flicker summation law and the specific flicker transfer factors which result out of the grid's impedance matrix, a detailed analysis of the flicker emission situation in a grid can be done. A case study with electric arc furnaces in a 110 kV grid is presented as application example, including a sensitivity analysis. View full abstract»

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  • Optimal selection of voltage sag mitigation solution based on event tree method

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    Modern commercial operations consist of critical equipments that are more susceptible to voltage sag events. The consistent and smooth running of these operations is often disrupted by voltage sags. Diverse range of solutions exist which can enhance the ride through capability of sensitive devices. This paper presents various voltage dip mitigation solutions and a methodology for analyzing the effectiveness and practical viability of these solutions. The proposed approach is based on event tree method which gives an indication about the extent of process interruption in the event of voltage sags. A case study is conducted in the paper with different combinations of practical mitigation solutions against voltage sags, in order to illustrate the applicability of the proposed approach. View full abstract»

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  • A novel approach for assessing the impacts of voltage sag events on customer operations

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    The business activities of the majority of industrial and commercial customers are dependent on some critical equipments that are susceptible to voltage sag events. This paper aims to propose a novel approach to estimate the financial impacts of voltage sag events on customer operations. The proposed technique is based on the event tree method. Using this approach, it is possible to consider the impacts of operational failure of various sensitive equipments, involved in the customer operations, on the financial losses expected from voltage sag events. A quantitative case study is conducted in the paper to illustrate the applicability of the proposed approach. View full abstract»

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  • Estimation of small scale HPP affect on distribution network reliability under market conditions

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    Mathematical model of small scale HPP was developed for simulation of HPP electricity production in market conditions. Paper also presents approach for evaluation of power supply reservation possibility in distribution network using small scale HPP that operates in liberalized market conditions. Proposed approach allows evaluate theoretical possibility of HPP to improve reliability of power supply of distribution network in case of HV substation outage. Calculations for example with real HPP and distribution network were performed using proposed approach. Results of calculations showed that amount of possible reserved energy using small scale HPP is strongly dependant on type of generator installed at HPP and usage of smart grid technologies in distribution network. View full abstract»

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