An MRAS Speed Observer Based on dq-axis Power Winding Flux for Sensorless Control of Standalone BDFIGs

This paper addresses a new mechanical rotor speed observer for sensorless control of standalone Brushless Doubly-Fed Induction Generators (BDFIGs) based on the dq axis power winding flux model reference adaptive system (MRAS) observer. The observer is integrated in the control method for control the terminal frequency and voltage magnitude under various work conditions. The efficiency of the proposed observer and control strategy is proved by overall simulation results and confirmed by experiments. As illustrated without using physical rotor speed sensors, the sensorless control strategy integrating the proposed speed observer can keep effectively the frequency and amplitude of power winding voltage fixed at various rotor speeds and under various conditions of machine parameter and load changes

Fractional kVA Rating PWM Converter Doubly Fed Variable Speed Electric Generator Systems:An Overview in 2020

Variable speed generator systems (VSGs) are at work in the now 600 GW installed wind power plants (parks). Also, they are used as vehicular and on ground stand-alone generators. VSGs imply full kVA rating PWM converters in permanent magnet (PM) or in electrically excited synchronous or in cage rotor inductance generators. But, to reduce cost in absence of PMs at a reasonable initial cost (weight) and efficiency, the fractional kVA PWM converter doubly fed induction generators (DFIG) cover now about 50% of all installed power in wind generators. The present paper reviews recent progress in DFIG and various forms of brushless DFGs (doubly fed generators) characterized in terms of topology, design, performance and advanced control for healthy and faulty load conditions in the hope of inspiring new, hopefully ground breakings, progress for wind and hydro energy conversion and in vehicular and on the ground stand-alone generator applications

A comprehensive review on brushless doubly-fed reluctance machine

The Brushless Doubly-Fed Reluctance Machine (BDFRM) has been widely investigated in numerous research studies since it is brushless and cageless and there is no winding on the rotor of this emerging machine. This feature leads to several advantages for this machine in comparison with its induction counterpart, i.e., Brushless Doubly-Fed Induction Machine (BDFIM). Less maintenance, less power losses, and also more reliability are the major advantages of BDFRM compared to BDFIM. The design complexity of its reluctance rotor, as well as flux patterns for indirect connection between the two windings mounted on the stator including power winding and control winding, have restricted the development of this machine technology. In the literature, there is not a comprehensive review of the research studies related to BDFRM. In this paper, the previous research studies are reviewed from different points of view, such as operation, design, control, transient model, dynamic model, power factor, Maximum Power Point Tracking (MPPT), and losses. It is revealed that the BDFRM is still evolving since the theoretical results have shown that this machine operates efficiently if it is well-designed

A comprehensive review on brushless doubly-fed reluctance machine

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. The Brushless Doubly-Fed Reluctance Machine (BDFRM) has been widely investigated in numerous research studies since it is brushless and cageless and there is no winding on the rotor of this emerging machine. This feature leads to several advantages for this machine in comparison with its induction counterpart, i.e., Brushless Doubly-Fed Induction Machine (BDFIM). Less maintenance, less power losses, and also more reliability are the major advantages of BDFRM compared to BDFIM. The design complexity of its reluctance rotor, as well as flux patterns for indirect connection between the two windings mounted on the stator including power winding and control winding, have restricted the development of this machine technology. In the literature, there is not a comprehensive review of the research studies related to BDFRM. In this paper, the previous research studies are reviewed from different points of view, such as operation, design, control, transient model, dynamic model, power factor, Maximum Power Point Tracking (MPPT), and losses. It is revealed that the BDFRM is still evolving since the theoretical results have shown that this machine operates efficiently if it is well-designed

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

Sensorless adaptive control of brushless doubly-fed reluctance generators for wind power applications

A novel model reference adaptive system for the rotor position/speed estimation and sensorless operation of a brushless doubly fed reluctance generator with maximum power point tracking is presented. Its main advantage over the existing designs are the inherent robustness and stability afforded by the complete parameter independence of the reference model using only the measured currents of the converter-fed (secondary) winding. In addition, the respective stationary frame current components are estimated by the adaptive model using the voltage and current measurements of the grid-connected (primary) winding at line frequency, offering higher accuracy. The simulation and experimental results have demonstrated the excellent real and reactive power controller performance for typical operating characteristics of wind turbines

Performance comparisons of doubly-fed machines

This research project aims at evaluating a conversion system based on the emerging Brushless Doubly Fed Reluctance Machine (BDFRM) through a comparative experimental study with a traditional and well established slip-ring counterpart, the Doubly Fed Induction Machine (DFIM). One of the main objectives is to establish whether this alternative machine is worthy of industrial consideration in variable speed applications with limited speed ranges (e.g. wind turbines, pump-like drives etc.) in terms of control, reliability, efficiency and power factor performance as major criteria. Such kind of work has not been reported in the open-literature to date and represents the main contribution of the project being undertaken. A conventional and widely used parameter-independent vector control (VC) scheme has been selected for the operation of both the machines using a shaft-position sensor. The VC algorithm has been simulated and implemented in real-time on state-of-the-art eZdsp development platform based on the TMS320F28335 Digital Signal Controller (DSC). The control code has been derived from a programme written in C++ using the corresponding compiler, the Code Composer Studio (CCS). Comprehensive computer simulations have been done in Matlab/Simulink using the parameters obtained by off-line testing of the DFIM and BDFRM prototypes, which have been built in the same stator frame for comparison purposes. The simulation results have been experimentally verified on two identical test rigs where a commercial 4-quadrant cage induction machine V/f drive has been used as a prime mover or load for either the DFIM or the BDFRM subject to their operating mode. The preliminary experimental results on two small-scale prototypes have shown that the BDFRM can achieve competitive performance to the similarly rated DFIM and as such should warrant further investigation and increasing interests of both academic and industrial communities as a potential large-scale wind generator or a pump drive

Dynamic Modeling and Control of BDFRG under Unbalanced Grid Conditions

The Brushless Doubly-Fed Reluctance Generator (BDFRG) is a potential alternative to the Doubly Fed Induction Generator (DFIG) in wind power applications owing to its reasonable cost, competitive performance, and high reliability. In comparison with the Brushless Doubly-Fed Induction Generator (BDFIG), the BDFRG is more efficient and easier to control owing to the cage-less rotor. One of the most preferable advantages of BDFRG over DFIG is the inherently better performance under unbalanced grid conditions. The study conducted in this paper showed that conventional vector control of the BDFRG results in excessive oscillations of the primary active/reactive power, electromagnetic torque, and primary/secondary currents in this case. In order to address such limitations, this paper presented a new control strategy for the unbalanced operation of BDFRG-based wind generation systems. A modified vector control scheme was proposed with the capability to control the positive and the negative sequences of the secondary currents independently, thus greatly reducing the adverse implications of the unbalanced supply. The controller performance has been validated by simulations using a 1.5 MW BDFRG dynamical model built upon the positive and negative sequence equations. The main benefits of the new control strategy are quantified in comparison with conventional PI current control design

Performance analysis of doubly-fed induction generator (DFIG)- based wind turbine with sensored and sensorless vector control

PhD ThesisConventional energy sources are limited and pollute the environment. Therefore more attention has been paid to utilizing renewable energy resources. Wind energy is the fastest growing and most promising renewable energy source due to its economically viability. Wind turbine generator systems (WTGSs) are being widely manufactured and their number is rising dramatically day by day. There are different generator technologies adopted in wind turbine generator systems, but the most promising type of wind turbine for the future market is investigated in the present study, namely the doubly-fed induction generator wind turbine (DFIG). This has distinct advantages, such as cost effectiveness, efficiency, less acoustic noise, and reliability and in addition this machine can operate either in grid-connected or standalone mode. This investigation considers the analysis, modeling, control, rotor position estimation and impact of grid disturbances in DFIG systems in order to optimally extract power from wind and to accurately predict performance. In this study, the dynamic performance evaluation of the DFIG system is depicted the power quantities (active and reactive power) are succeed to track its command signals. This means that the decouple controllers able to regulating the impact of coupling effect in the tracking of command signals that verify the robust of the PI rotor active power even in disturbance condition. One of the main objectives of this study is to investigate the comparative estimation analysis of DFIG-based wind turbines with two types of PI vector control using PWM. The first is indirect sensor vector control and the other type includes two schemes using model reference adaptive system (MRAS) estimators to validate the ability to detect rotor position when the generator is connected to the grid. The results for the DFIG-based on reactive power MRAS (QRMRAS) are compared with those of the rotor current-based MRAS (RCMRAS) and the former scheme proved to be better and less sensitive to parameter deviations, its required few mathematical computations and was more accurate. During the set of tests using MATLAB®/SMULINK® in adjusting the error between the reference and adaptive models, the estimated rotor position can be obtained with the objective of achieving accurate rotor position information, which is usually measured by rotary encoders or resolvers. The use of these encoders will conventionally lead to increased cost, size, weight, and wiring ii complexity and reduced the mechanical robustness and reliability of the overall DFIG drive systems. However the use of rotor position estimation represents a backup function in sensor vector control systems when sensor failure occurs. The behavioral response of the DFIG-based wind turbine system to grid disturbances is analyzed and simulated with the proposed control strategies and protection scheme in order to maintain the connection to the network during grid faults. Moreover, the use of the null active and reactive reference set scheme control strategy, which modifies the vector control in the rotor side converter (RSC) contributes to limiting the over-current in the rotor windings and over-voltage in the DC bus during voltage dips, which can improve the Low Voltage Ride-through (LVRT) ability of the DFIG-based wind turbine system.my home country of Iraq and its Ministry of Planning for providing a scholarship for my study

Comparative study between sliding mode control and the vector control of a brushless doubly fed reluctance generator based on wind energy conversion systems

Introduction. Nowadays, global investment in renewable energy sources has been growing intensely. In particular, we mention here that wind source of energy has grown recently. Purpose. Comparative study between sliding mode control and vector control of a brushless doubly fed reluctance generator based on wind energy conversion systems. Methods. This paper deals with conceptual analysis and comparative study of two control techniques of a promising low-cost brushless doubly-fed reluctance generator for variable-speed wind turbine considering maximum power point tracking. This machine's growing interest because of the partially rated power electronics and the high reliability of the brushless design while offering performance competitive to its famous spring counterpart, the doubly-fed induction generator. We are particularly interested in comparing two kinds of control methods. We indicate here the direct vector control based on Proportional-Integral controller and sliding mode controller. Results. Simulation results show the optimized performances of the vector control strategy based on a sliding mode controller. We observe high performances in terms of response time and reference tracking without overshoots through the response characteristics. The decoupling, the stability, and the convergence towards the equilibrium are assured.Вступ. Нині глобальні інвестиції у відновлювані джерела енергії стрімко зростають. Зокрема, звернемо увагу, що останнім часом має місце зростання  вітряних джерел енергії. Мета. Порівняльне дослідження між управлінням ковзним режимом та векторним управлінням безщіткового реактивного генератора з подвійним живленням на основі систем перетворення енергії вітру. Методи. Стаття присвячена концептуальному аналізу та порівняльному дослідженню двох методів управління перспективним недорогим безщітковим реактивним генератором з подвійним живленням для вітряної турбіни зі змінною швидкістю з урахуванням відстеження точки максимальної потужності. Інтерес до цієї машини зростає частково завдяки силовій електроніці, а також високій надійності безщіткової конструкції, яка при цьому пропонує характеристики, порівняні з його загальновідомим пружинним аналогом, індукційним генератором з подвійним живленням. Автори особливо зацікавлені у порівнянні двох видів методів управління. Автори вказують тут на пряме векторне управління на основі пропорційно-інтегрального регулятора та регулятора ковзного режиму. Результати. Результати моделювання показують оптимізовані характеристики векторної стратегії управління на основі контролера ковзного режиму. Спостерігаються високі показники з точки зору часу відгуку та відстеження еталонних значень без перевищення показників відгуку. Розв'язка, стабільність та прагнення до рівноваги гарантуються