A Novel Thermal Network Model Used for Temperature Calculation and Analysis on Brushless Doubly-Fed Generator With Winding Encapsulating Structure

© 1972-2012 IEEE. In recent years, magnetic-barrier rotor has been put forward for brushless doubly-fed generator (BDFG) application owing to its desirable performance, such as high power density and strong magnetic coupling ability. However, it also causes significant losses induced by harmonics and high temperature problem. Hence, it is a major challenge to evaluate Bref-DFG temperature rise fast and accurately. So far, aiming at magnetic-barrier rotor, there has been no accurate thermal network model established achieving this goal. In addition, wingding end encapsulating technology has been used for a few years and its heat dissipation potential is determined by the materials. Therefore, the application of novel material in winding encapsulating structure is desirable to improve the heat dissipation potential. In this paper, an equivalent thermal network model, thermal resistance models of magnetic-barrier rotor, and a winding encapsulating structure with novel materials are further established for thermal analysis. Subsequently, temperature distributions for BDFG components are also calculated by finite element method, while the results are compared with those by analytical method. The BDFG prototype is manufactured with experimental tests performed. The correctness of the equivalent thermal network models proposed in this paper is verified by the test results

Brushless Doubly-Fed Reluctance Machines for Aerospace Electrical Power Generation Systems

This thesis describes a programme of research encompassing the design, optimisation and experimental testing of a brushless doubly fed reluctance machine (BDFRM) for use as an aerospace electrical generator, specifically a direct line connected generator, to widen the input shaft speed beyond the normal constraints imposed by the 360-800Hz specification for a variable-frequency AC aerospace network. BDFRMs offer the functionality of frequency correction, via a control winding, and have the advantage of using a robust reluctance rotor. A partially-rated control winding converter can, in principle, be used to provide the slip power required. A further advantage of the BDFRM is the inherent fail-safe nature of these machines, with the output voltage collapsing as soon as the control winding current has been removed. A synchronous reluctance machine was studied as a means of providing a baseline for the BDFRM performance, including a comparison of the effect of scaling on power density. A large number of time-stepped finite element simulations were undertaken to explore BDFRM performance, in particular, the influence of magnetic saturation in limiting the achievable power density and in compromising power quality. Detailed optimisation of a BDFRM was undertaken, including systematic mechanical design of the rotor for high speed operation. This analysis illustrates the significant compromises in machine electromagnetic performance which result from the need to accommodate mechanical stress. The scope for employing small amounts of permanent magnet material in the rotors of both synchronous reluctance machines and BDFRMs, to improve the machine performance at the lower end of the current density range, was investigated. Following detailed optimisation, a demonstrator machine was manufactured, which includes a skewed rotor. The performance of this machine was measured at a number of test points to verify predictions of output power, voltage and voltage harmonics

Comparison of doubly-fed induction generator and brushless doubly-fed reluctance generator for wind energy applications

Phd ThesisThe Doubly-fed Induction Generator (DFIG) is the dominant technology for variable-speed wind power generation due in part to its cost-effective partially-rated power converter. However, the maintenance requirements and potential failure of brushes and slip rings is a significant disadvantage of DFIG. This has led to increased interest in brushless doubly-fed generators. In this thesis a Brushless Doubly-Fed Reluctance Generator (BDFRG) is compared with DFIG from a control performance point of view. To compare the performance of the two generators a flexible 7.5kW test facility has been constructed. Initially, a classical cascade vector controller is applied to both generators. This controller is based on the stator voltage field orientation method with an inner rotor (secondary stator) current control loop and an outer active and reactive power control loop. The dynamic and steady state performance of two generators are examined experimentally. The results confirm that the BDFRG has a slower dynamic response when compared to the DFIG due to the larger and variable inductance. Finally a sensorless Direct Power Control (DPC) scheme is applied to both the DFIG and BDFRG. The performance of this scheme is demonstrated with both simulation and experimental results.Engineering and Physical Sciences Research Council (EPSRC) and Overseas Researcher Scholarship (ORS

Brushless doubly-fed reluctance machine modeling, desing and optimization

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2015.Esta tese aborda a modelagem, o projeto e a otimização, com validação experimental, de máquinas de relutância duplamente alimentadas sem escovas (BDFRM) para sistemas de geração de energia eólica. O objetivo principal dela é de contribuir para o domínio de técnicas de projeto otimizado para a BDFRM através da proposição de uma metodologia baseada em diferentes níveis de modelagem e em otimização. Discute-se como técnicas de otimização podem ser aplicadas em todas as fases de desenvolvimento com objetivos distintos. Especificamente, a metodologia proposta se concentra na definição e na solução iterativa de problemas de otimização com restrições nas saídas utilizando um algoritmo determinístico acoplado a modelos semi-analíticos de diferentes níveis. Como conclusão geral, pode-se afirmar que a BDFRM é potencialmente uma boa candidata para ser utilizada em sistemas de geração de energia eólica. Contudo, aspectos técnicos e econômicos sobre essa escolha devem ainda ser avaliados, comparando-se as diferentes topologias existentes sob o mesmo enfoque metodológico.Abstract : This thesis addresses the modeling, design and optimization with experimental validation of the Brushless Doubly-Fed Reluctance Machine (BDFRM) for wind power systems. Its main goal is to contribute on mastering the BDFRM optimized design by proposing a methodological approach based on different modeling levels and on optimization. More precisely, it draws its attention on setting the optimization problem and on the iterative solution of a constrained inputs/outputs problem by using a deterministic algorithm. As a general conclusion, the results show that the BDFRM is potentially a good candidate to be used in wind power systems. However, the technical and economic aspects on this choice must be still assessed, analyzing and comparing the overall system solution of distinct topologies within the same framework

Sensorless MRAS control of emerging doubly‐fed reluctance wind generators

A new model reference adaptive system based estimation technique for vector control of real and reactive power of a brushless doubly fed reluctance generator without a shaft position sensor is proposed. The rotor speed is being precisely observed in a closed‐loop manner by eliminating the error between the measured and estimated inverter‐fed (secondary) winding current angles in a stationary frame. Contrary to the existing model reference adaptive system observer designs reported in the brushless doubly fed reluctance generator literature, the reference model is entirely parameter‐free and only utilises direct measurements of the secondary currents. Furthermore, the current estimates coming from the adaptive model are obtained using the measured voltages and currents of the grid‐connected (primary) winding, which has provided prospects for much higher accuracy and superior overall performance. The realistic simulations, preliminary experimental results, and the accompanying parameter sensitivity studies have shown the great controller potential for typical operating conditions of variable speed wind turbines with maximum power point tracking

Studies in Electrical Machines & Wind Turbines associated with developing Reliable Power Generation

The publications listed in date order in this document are offered for the Degree of Doctor of Science in Durham University and have been selected from the author’s full publication list. The papers in this thesis constitute a continuum of original work in fundamental and applied electrical science, spanning 30 years, deployed on real industrial problems, making a significant contribution to conventional and renewable energy power generation. This is the basis of a claim of high distinction, constituting an original and substantial contribution to engineering science

Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine

Optimal performance of the electric machine/drive system is mandatory to improve the energy consumption and reliability. To achieve this goal, mathematical models of the electric machine/drive system are necessary. Hence, this motivated the editors to instigate the Special Issue “Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine”, aiming to collect novel publications that push the state-of-the art towards optimal performance for the electric machine/drive system. Seventeen papers have been published in this Special Issue. The published papers focus on several aspects of the electric machine/drive system with respect to the mathematical modelling. Novel optimization methods, control approaches, and comparative analysis for electric drive system based on various electric machines were discussed in the published papers

Milestones, hotspots and trends in the development of electric machines

As one of the greatest inventions of human beings, the electric machine (EM) has realized the mutual conversion between electrical energy and mechanical energy, which has essentially led humanity into the age of electrification and greatly promoted the progress and development of human society. This paper will briefly review the development of EMs in the past two centuries, highlighting the historical milestones and investigating the driving force behind it. With the innovation of theory, the progress of materials and the breakthrough of computer science and power electronic devices, the mainstream EM types has been continuously changing since its appearance. This paper will not only summarize the basic operation principle and performance characteristics of traditional EMs, but also that of the emerging types of EMs. Meanwhile, control and drive system, as a non-negligible part of EM system, will be complementarily introduced. Finally, due to the background of global emission reduction, industrial intelligentization and transportation electrification, EM industry will usher again in a golden period of development. Accordingly, several foreseeable future developing trends will be analyzed and summarized

High-speed single-phase permanent magnet brushless DC motor.

Due to high efficiency, high power density and low cost, single-phase permanent magnet brushless DC motor has increasingly been used in industrial and domestic applications. This thesis focuses on the design and analysis of high-speed, single-phase, conventional and flux-switching permanent magnet brush less DC motors. This thesis presents a comparative study of conventional three-phase and single-phase permanent magnet brush less DC motors, which operate at 45,OOOrpm with I.lkW output power for the pump application, in terms of their machine design, drive system and electromagnetic performance. It is found that the single-phase permanent magnet brush less DC motor has a relatively lower drive system cost without significantly compromising the electromagnetic performance. Further, significant rotor eddy current loss exists in both motors. Hence, the analytical models are developed to predict the rotor eddy current loss which is resulted from the armature reaction field. By comparing with the 2D finite element method (FEM) predicted results, good agreement is obtained over the full speed range if the eddy current reaction field is taken into account. FEM is further employed to investigate open-circuit, armature and on-load rotor eddy current losses of the permanent magnet brushless DC motors. Particular emphasis is placed on the single-phase motor having an eccentric airgap with consideration for degree of airgap eccentricity, excitation current waveform, magnet segmentation, thickness and electrical conductivity of the retaining sleeve. The single-phase flux switching permanent magnet motor, which operates at 100,000rpm with 1.2kW output power for the automotive electrical turbo-charger application, is also investigated. Its operational principle is introduced and winding topologies are investigated. In addition, the chamfered rotor pole is optimised to improve the starting capability. In order to investigate the influence of significant end leakage-flux, a 3D lumped circuit magnetic model is developed to predict the back-EMF and the inductance and validated through experiment. This model is also employed to optimise the rotor pole width for increasing the motor power density and to investigate the relationship between the magnet dimensions and the motor end effect. Finally, the dynamic simulation models are developed to predict the dynamic electromagnetic performance and experimentally validated for a three-phase and a single-phase permanent magnet brush less DC motor, and a single-phase flux switching permanent magnet motor