Monthly Archives: December 2018

Disturbance Analysis for Power Systems Based on LabVIEW Real-Time and Reconfigurable FPGA Modules Using Wavelet Transform

30 December 2018Fără categoriecburada

Abstract

This paper present a disturbance analysis moni-toring system for the purpose of detection of disturbance analysis using Wavelet Transform (WT). The proposed sys-tem is based on the real-time capabilities of the Real-Time LabVIEW operating system and on a CompactRIO type real-time computer which contains a network of FPGA (Field Programmable Gate Array). The WT is used to ana-lyze the quality of energy and to detect the transient phe-nomena characteristic of the quasi-periodic signals. The system achieves the storage of entries as TDMS (Technical Data Management Streaming) files and Word/Excel type automatic reports automatically sent by email at predefined addresses, contains an OPC UA (Open Platform Communi-cations Unified Architecture) type server for communication with a hierarchically superior SCADA (Supervisory Control And Data Acquisition) type system, performs selective entry of the characteristic parameters into a database, contains a Webserver for Intranet/Internet access, for viewing the measured data, and for system management from any-where, the application is connected to a Cloud-type plat-form. The disturbance analysis monitoring system has been tested using both simulated signals and real signals from a practical experiment.

Simulation of Idle Running Operating Characteristics for Low-Power Asynchronous Motors

30 December 2018Fără categoriecburada

Abstract

The opportunity of this work is backed by the possibility to predetermine the operating characteristics of an asynchronous motor in idle running. This contributes to the realization of a high performance electric drive. An analysis is aimed for low power asynchronous motors used in different types of applications, such as robots, medical equipment and home appliances, transportation systems a.s.o. It is insisted on an advanced mathematical model that provides the best results in simulations and applications [1]. The simulations are important for their quality and preci-sion because they allow us to anticipate the motor behavior and also to establish the errors between the simulation and experimental results. The mathematical model used consid-ered the equations written in the two-axes theory, the rotor quantities being expressed in the fixed stator reference frame. The need for knowledge of qualitative and quantita-tive dynamic behavior related to the field of use determined major investments and extensive research in large laborato-ries. Research on an asynchronous motor with a power of 1.1 kW with variable parameters proved that, between the idle running simulated and experimentally determined val-ues, the errors do not exceed 3.97%. These results authorize the conducted research, providing qualitative and quantita-tive correct simulations for the rated regime.

Current Aspects in the Conception and Performance of Dispatching Manoeuvres in the National Electric Power Transmission System

30 December 2018Fără categoriecburada

Abstract

In this paper, the authors have structured a com-plete algorithm for calculating the self-excitement of the generating groups in the NPS power plants, a phenomenon that can occur in the operative manoeuvres performed in 220 kV, 400 kV and 750 kV electrical networks. This shows how with simple parameter calculations can be evaluated parameter approximate values for long lines switching re-gimes, the safety measures to be taken when manoeuvres are appropriately performed and their sequence in order to avoid dangerous overvoltages that would lead to non-admissible stresses of the energetic equipments. In order to increase the degree of generality of these calculations, the relative size method was used, for which a computational program developed in the Mathcad programming environ-ment was designed. This calculation algorithm was custom-ized for a double-circuit overhead electric line LEA 220 kV case study. Also are presented the practical algorithms for calculating the voltage jump that occurs when connecting and disconnecting the long electric transmission lines from the power system. The overvoltages caused by the switching of these lines are also evaluated. These values must be taken into account by the managerial and operational staff to properly perform and coordinate manoeuvres. For the con-sidered double-circuit overhead power line 220 kV LEA, the calculation algorithms for both no load and under load switching were customized, and two scenarios were studied, namely when the line is not compensated and when the line is compensated by a compensation coil.

The Resistive Tubular Heater - Mathematical and Simulation Model

30 December 2018Fără categoriecburada

Abstract

It is essential to achieve the mathematical model and the simulation when designing complex installations. This allows the analysis of different operating modes and the behavior of the existing system. It enables notification of possible errors and their correction, avoiding additional costs involved for achieving and testing facility in real condi-tions. Some operating modes could be degraded modes. This would be very difficult to replicate or would give rise to a faulty installation. In order to model and simulate a com-plex installation it is, however, need that the components are modeled correctly and to be interpreted correctly the inter-actions between them and the dependency of the parameters on the operating conditions. Because many complex systems incorporate electrical heating tube elements, this paper pro-poses an original mathematical model for a resistive tubular heater. Based on this model it was developed a Matlab-Simulink simulation model. The model has been designed so that it can be easily adapted to various situations, where the heating elements in tube are immersed in liquids or embed-ded in solid materials. The proposed model allows a fast simulation and evaluation of the function of the resistive tubular heater in transient regime or under steady state regime. One challenge was to minimize the parameters which need to be pre-calculated based on physical and con-structive data, in order to enroll them in the prescription blocks of the model. The viability of the presented modeling system was verified both by comparison with a real heating element and by drawing the temperature curves. These curves highlight the fitting in the admitted temperature domain for such an element.

Implementation of Virtual Instrumentation for Testing of Induction Motors

30 December 2018Fără categoriecburada

Abstract

This paper presents an implementation of an ad-vanced system that uses virtual instrumentation as the main component in the process of measurement and testing of three phase asynchronous motors. This approach permits the replacement of the old analog measurement techniques – which are still in use in the industry applications at some electrical motor testing benches, with the new advanced measurement system bench. This system bench is capable of data acquisition, storage on different media, visualization of relevant graphs, printing or distribution of technical reports or analysis on-line or off-line in an automated manner. The general architecture of the proposed system is focused on the hardware components (transducers, conditioning, data acquisition, calculator) and software components (driver for the acquisition and manipulation-calculation of data, graphical presentation, other auxiliary programs and the ones to bring all the components together, virtual instru-ments). The proposed system allows the application of methods for determining losses and efficiency from tests. Some of the most important requirements of the interna-tional standards for induction motors testing are used: gen-eral technical verification, determination of the windings resistance in DC, no-load testing and running characteristics testing. This system would be very useful in industry appli-cations in the domains of electrical machines for testing workbenches and design laboratories.

Graphical User Interface to Extrapolate the Ideal Covering Factor of the Polar Step

30 December 2018Fără categoriecburada

Abstract

This paper treats some aspects of the geometrical design of salient synchronous generator, used in railway traction. It focus on the transformation of given experimen-tal data curves into polynomial based regression model which could be use easier in a Computer Aided Design. The final aim of this work is to summarize many detailed by literature recommendations regarding the fabrication ex-perience and to use these to design a Graphical User Inter-face with which, the user perform a specific task in area of designing a salient synchronous generator. For this paper, the proposed task is to interpolate and to plot the depend-ence between ideal covering factor of the polar step and the real one, based on the curves offered by the literature. Using this representation, the user/the designer could choose the appropriate value of the ideal covering factor of the polar step for its case study in a short time and, also, could send this data to the main program. The added value of this work is to create a tool which could be used easier, in different situations. This tool is completely original and is a part of a collection of graphical user interfaces created by the authors to be used in a computer aided design of a salient pole syn-chronous generator calculation.

Controller for BLDC Motors

30 December 2018Fără categoriecburada

Abstract

In this paper it is presented a comprehensive design of a dedicated controller for BLDC motor with maximal electric power around 1000W. That controller is a new product in testing stage and it uses high-end components to provide high performance and more flexibility of the implemented algorithms at a low-level cost. The controller can drive a BLDC motor providing the possibility of rotating in both directions, it creates an electromagnetic brake and kinetic energy recovery system. The controller has equipped a 500W electric scooter, and a 1000W electric motor cart and it proved to be reliable, performance and especially flexible. All software routines make the code very fast portable by parameterizing all the implemented software functions.

Application of Direct Optimization Method by Zooms to Improve the Performances of AC Electromagnet

30 December 2018Fără categoriecburada

Abstract

The paper seeks to improve the force developed by an AC electromagnet at maximum air-gap, using the direct optimization method by zooms, based on numerical experiments performed by finite element method (FEM) in ANSYS software. In a previous work, a 5.68% improvement in the static force characteristic of the same device was achieved and particularly, a 12.63% improvement in the force at maximum air-gap, taking into account three very influential geometrical parameters: the rate of bottom core thickness, rate of ring width and the rate of lateral core thickness. The optimization problem was subject to con-straints of maintaining the overall dimensions of the device. The research continues in this paper with the search for the optimal geometrical configuration to provide a maximum developed force in the “open” position, replacing the pa-rameter rate of ring width, having the least influence, with the parameter rate of winding thickness and adding the constraint of maintaining the cross-section of the winding. A device screening ensures that all the new three parameters are worth considering with a confidence level greater than 99%. The solution of the optimization problem brings an improvement of 25.67% of the acting force and of 7.09% of the static characteristic. The magnetic force was determined based on the principle of virtual work, available in ANSYS software.

How to Design a Passive Damped LCL Coupling Filter for an Active DC-Traction Substation

30 December 2018Fără categoriecburada

Abstract

The attention in this paper is directed to the de-sign of a passive damped LCL filter intended to connect the voltage source inverter of an active DC-traction substation to the AC-power supply. Based on the tasks to be fulfilled by the passive connecting filter related to the current filtering and its dynamics, the mathematical foundation of the LCL filter design consists in taking into consideration the trans-fer function of the currents, the switching frequency, the resonance frequency and the compensated harmonics by active filtering. A design algorithms is formulated, by con-sidering the imposition of the attenuation corresponding to the switching frequency. Besides this, the position of the resonance frequency relative to the frequency of the highest order harmonic to be compensated is imposed. The design algorithm is fully formulated, and specific indicators are defined and used to evaluate the performance of the whole active filtering system. The case study taken into considera-tion is of the active DC-traction substation, where the un-controlled traction rectifier is of 12-pulse parallel type. Based on Matlab-Simulink modeling, the simulation of the whole active DC-traction substation operating in both active filtering and regeneration regimes illustrates the proper behavior of the system and the influence of the LCL filter parameters on the power quality performance.

Analytical Study, Numerical Modelling and Experimental Results of the Forces which Act in the Magnetic Liquid Placed between the Poles of an Electromagnet

30 December 2018Fără categoriecburada

Abstract

This paper makes an analytical study, a numerical and an experimental analysis of the magnetic forces which act in magnetic liquids during the experiment called Quincke’s effect. Quincke’s effect consists in the rise of the magnetic liquid between the poles of an electromagnet. In ferrohydrodynamics theory, the forces acting in the magnetic liquid are not always treated in a uniform manner. The main goal of this paper is to give a consistent macroscopic view, pointing out the importance of the magne-tostriction in the force localization understanding. If the absence of the magnetostrictive term in the forces expres-sion leads to an exclusively superficial localization of the forces, the presence of this term leads both to a superficial localization of forces as well as their presence in the mag-netic liquid volume. Moreover, in the magnetic liquid rise, the volume forces have a significant contribution than the surface forces, so the magnetostrictive term shall not be neglected. In this analysis, the magnetic liquid will be considered as a linear and nonconducting medium placed in a stationary (or quasistationary) field. In order to support the analytical study, a numerical analysis of the magnetic forces and some qualitative experiments were made. The value of the magnetic field forces which act in the magnetic liquid were established in Matlab using the magnetic field strength established by FEM analysis. Analyzing the numerical results and the magnetic liquid deformation obtained by ex-periments, the main conclusion consists in the fact that the magnetostrictive term has an important contribution in the localization of the forces, so it shall be taken into consideration.