Doubly-fed Reluctance Machine Research Articles

Modeling and Design Optimization of Rotor Flux-Barriers in a Brushless Doubly-Fed Reluctance Machine

Modeling and Design Optimization of Rotor Flux-Barriers in a Brushless Doubly-Fed Reluctance Machine

Impact of Rotor Flux-Barriers on Coupling Coefficient in a Brushless Doubly-Fed Reluctance Machine

A brushless doubly-fed reluctance machine offers several advantages over a single-port machine since it requires a partially-rated power converter, provides reduced maintenance, and operates without permanent magnets. The complexity of the air-gap magnetic fields due to differing winding-pole numbers interacting with a reluctance rotor have precluded the use of an analytical framework to optimize the rotor. Instead, researchers have relied upon time-consuming finite element analysis (FEA). This paper presents an analytical method to compute closed-form solutions for the mean torque, captured by the coupling coefficient, using a practical circular ducted rotor. The method also accounts for the potential drop across the flux-barriers, leading to a better estimation of mean torque. The model is validated using both FEA and experimental tests.

Modified active power-MRAS for limited range variable speed sensorless brushless doubly-fed reluctance machine drive

PurposeThis paper aims to suggest a parameter independent and simple speed estimator for primary field-oriented control of a promising electro-mechanical energy conversion device in the form of brushless doubly-fed reluctance machine (BDFRM) drive.Design/methodology/approachThe speed estimation algorithm, in this context, is formulated using a modified secondary winding active power (mPs)-based model reference adaptive system (MRAS). The performance of the proposed estimator is verified through computer aided MATLAB simulation study, compared with conventional active power-based MRAS and further supported with experimental validation using a 1.6 kW BDFRM prototype run by a dSPACE-1103 controller.FindingsThe formulation of mPs-MRAS is insensitive to any machine parameters and does not involve any integration/differentiation terms. Thus, any deviation therein does not hinder the performance of the mPs-MRAS-based speed estimator. The proposed speed estimator shows stable behavior for variable speed-constant load torque operation in all the four quadrants.Originality/valueThe formulation of mPs-MRAS is insensitive to any machine parameter and does not involve any integration/differentiation terms.

Analytical Calculation of Air-Gap Magnetic Field in Brushless Doubly-Fed Reluctance Machine With Flux Barriers

This paper presents an analytical approach to determine the air-gap magnetic field and the winding inductance in the brushless doubly-fed reluctance machine (BDFRM) with flux barriers. By dividing one flux guide layer into several segments, a calculus method based on magnetic circuit analysis is developed and specific analytical expression of the air-gap flux density is rigorously derived. Then, the included angle between fundamental components with the same pole pairs is also discussed. Based on the air-gap flux density distribution, the inductance expressions between different windings are also presented. Three kinds of finite element analysis models are established and studied. As a result, the accuracy of the analytical model can be verified by simulations and experimental data from an existing BDFRM prototype.

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.

Prototype of Implementation SVPWM Inverter in RTI with V/F Control Based Reluctance Machines Application

The paper proposes and investigates a suitable voltage time model implemented in real-time interface. In order to evaluate and compare performance of the emerging brushless doubly-fed reluctance machine (BDFRM) in conjunction with the response to software based architecture a scalar control is integrated into real-time dSPACE platform. The necessary algorithm was integrated and uploaded into dSPACE platform requiring the configuration arrangements of voltage and time vectors. Moreover, machine dynamics and mathematic model were identified, interlinked and synchronised with space vector pulse width modulator (SVPWM). In doing so the time vectors were aligned with RTI microprocessor and/or hardware-in-the-loop (HIL). The RTI library blocks were utilized to enable and substitute the actual machine parameter and match reference data accordingly. Consequently, the controller SVPWM coupled together with the proposed V/f control for the prominent BDFRM have been simulated and experimentally verified under the variable speed operating conditions. The feasibility, correctness and robustness of the proposed controller is validated and corroborated against the qualitative and quantitative data.

Sensorless Speed Control of Brushless Doubly-Fed Reluctance Motor Drive using Secondary Flux based MRAS

Different MRAS based approaches are gaining ample importance for the speed estimation of AC machine drives because of their simplicity and direct physical interpretation. In this work, MRAS is introduced for the sensorless control of promising low-cost brushless doubly-fed reluctance motor drive under primary field orientation and maximum torque per inverter ampere (MTPIA) conditions. In this regard, secondary flux vectors are employed as the control quantity in the formulation of the proposed MRAS. All the analytical studies, in this context, are carried out in MATLAB/Simulink. The scheme is further validated by a real-time experimentation using dSPACE-1103 based brushless doubly-fed reluctance machine (BDFRM) prototype. The simulation study and test results confirm the robust performance of the proposed controller around the synchronous speed. The investigation decisively affirms the feasibility of MRAS based approach for sensorless speed control of BDFRM drive as well.

Modeling and sizing by optimization of a Brushless Doubly-Fed Reluctance Machine

Modeling and sizing by optimization of a Brushless Doubly-Fed Reluctance Machine

An H-infinity approach to optimal control of doubly-fed reluctance machines

Abstract: An H-infinity approach is developed for the problem of nonlinear optimal control of doubly-fed reluctance machines. The dynamic model of the machines is subjected to linearization round local operating points, through Taylor series expansion and the computation of Jacobian matrices. For the linearized model an H-infinity feedback controller is designed, capable of compensating for the modelling error of the approximate linearization as well as for external perturbations affecting the machine. The computation of the feedback control gain is based on the solution of an algebraic Riccati equation that is performed at each iteration of the control algorithm. Lyapunov stability analysis for the control loop of the reluctance machine arrives at an H-infinity tracking performance criterion, and finally the asymptotic stability of the control loop is demonstrated. The excellent tracking performance of the H-infinity control method is confirmed through simulation experiments.

High-efficiency control of brushless doubly-fed machines for wind turbines and pump drives

The paper is concerned with vector control of a promising brushless doubly-fed reluctance machine (BDFRM) technology for generator and drive systems with limited adjustable speed ranges such as wind turbines or pump-alike installations. The BDFRM has been receiving increasing attention because of the low capital and operation and maintenance costs afforded by the partially-rated power electronics and the high reliability of brushless construction, while offering performance competitive to its well-known slip-ring counterpart, a doubly-fed induction machine. The comprehensive comparative studies have evaluated the performance of two robust control algorithms by computer simulations and experimentally on a custom-made BDFRM under the maximum torque per inverter ampere conditions for improved efficiency of electro-mechanical energy conversion.

Saturation and Ducting Effects in a Brushless Doubly-Fed Reluctance Machine

The brushless doubly-fed reluctance machine has two sets of stator windings of different pole number linked by a reluctance type of rotor. The rotor modulates the stator MMF from one winding so that flux links the other winding creating mutual coupling. This is still a research machine and the design methodology is under development. Past works indicates that a ducted rotor with radial laminations is best suited to be the reluctance rotor. In this paper the geometry of the rotor is investigated. If the ducts are too thin then the reluctance ratio is low and the coupling is affected. If they are too wide then the reluctance path for the coupling flux is high and the machine will saturate quickly. It is found, using finite element analysis, that the duct ratio should be about 38% from the results in the paper. This is in line with previous work on synchronous reluctance machines that can also use ducted rotors (although they use axial lamination which are inappropriate for this application).

Power control of brushless doubly-fed reluctance drive and generator systems

A new algorithm for shaft position sensor-less independent control of real and reactive power of the Brushless Doubly-Fed Reluctance Machine (BDFRM), an emerging competitive for applications with limited variable speed ranges (e.g. pumps or wind turbines), is proposed and experimentally verified in this paper. The algorithm is inspired by the fundamental operating principles of the machine and does not depend on any parameters. Therefore, it is more robust than model-based control approaches which often suffer from sensitivity issues and performance trade-offs associated with machine parameter variations or their inaccurate identification. In turn, the considered control method merely relies on the grid-connected winding voltage and current signals. Practical studies including speed tracking, power factor regulation and load response have demonstrated high performance of the scheme on a custom designed 1.5 kW prototype.

Brushless Doubly Fed Reluctance Machines: An Emerging Technology

Brushless doubly-fed machines (BDFMs) allow the use of a partially rated inverter and therefore offer reliable, maintenance-free operation at low cost, especially in large power variable speed applications with limited speed ranges such as off-shore wind turbines, pumps etc. However, with a special cage rotor design, the machine has substantial rotor losses, poor efficiency and complicated control being difficult to implement.The BDFM reluctance type, the brushless doubly-fed reluctance machine (BDFRM), can overcome most of the above BDFM deficiencies while retaining all its merits. It has a "cold" reluctance rotor, which makes it more efficient and much easier to model/control than the BDFM.A theoretical study of the BDFRM is very important to gain proper understanding of its unusual operation, the main control features and compromises between optimal performance and the size of the inverter and machine required. This paper will attempt to develop, and provide a comprehensive comparative analysis of, different control strategies for the machine that are suitable for digital implementation.

Assessment of Losses in a Brushless Doubly-Fed Reluctance Machine

This paper investigates the iron losses that occur in a brushless doubly-fed reluctance machine. This is a novel machine that is still being researched. It is found that the iron losses are quite high when using an axially-laminated rotor (as often used in a synchronous reluctance machine) in this application. Simulations are carried out using finite element analysis and the level of rotor eddy-current loss verified with experimental tests

Analysis of a polyphase synchronous reluctance motor with two identical stator windings

This paper presents the performance analysis of a cageless two-stator-winding reluctance motor which is capable of developing reluctance torque at good power factors in the absence of inverter control. The machine stator has two separate identical polyphase windings whose pole numbers are the same as that of the cageless rotor. The machine performance is investigated using the traditional circle diagrams, and the d– q rotor reference frame equations derived in space-vector form by applying the concept of winding functions. Core loss and saturation are accounted for in the developed dynamic model. It is shown that if one winding is connected directly to the supply and the other fed with a balanced capacitor, the developed torque is superior to a brushless doubly-fed reluctance machine (BDFRM) of similar size. Other motor characteristics, its line-start behaviour and torque ripples are also presented and discussed. Experimental results corroborate the simulations.

Performance Analysis and Control of a Brushless Doubly Fed Reluctance Machine

In this article, performance analysis and control technique for a brushless doubly-fed reluctance machine (BDFRM) with extensive simulation and experimental results is presented. The transient and steady-state governing equations are presented with appropriate assumptions. A speed control scheme based on field orientation control strategy is presented, and start-up behavior of the machine are studied extensively via digital simulation and experiments. Moreover, effects of both voltage and frequency of the control winding on the machine performance are studied. Digital simulation studies have been carried out using the proposed method of analysis and the results are compared to those obtained from an experimental machine.

Stator flux oriented control of a cascaded doubly-fed induction machine

A cascaded doubly-fed induction machine (CDFM) is a connection of two wound rotor induction machines. In comparison to a single doubly-fed induction machine (SDFM) brushes are obsolete. Due to recent developments in brushless doubly-fed machine design, there is a renewed interest in associated control. Theoretical and experimental studies of a stator flux oriented control method for a CDFM are presented. The use of vector control principles to control torque, speed, active and reactive power is investigated. It is found that the additional closed rotor circuit of the CDFM introduces a cross coupling between the d-axis and the q-axis. Nevertheless, the cross coupling effect remains small in relation to the overall control concept so that the control of the CDFM resembles that of the SDFM. List of symbols Abbreviations: SDFM - CDFM - SF-CDFM = - single doubly-fed induction machine cascaded doubly-fed induction machine single frame cascaded doubly-fed induc- tion machine brushless doubly-fed induction machine doubly-fed reluctance machine microcontroller pulse width modulation

D-q ANALYSIS OF A VARIABLE SPEED DOUBLY AC EXCITED RELUCTANCE MOTOR

ABSTRACT The paper describes a new type of variable speed doubly-fed reluctance machine and presents the model for the analysis of the machine. The stator of the machine is equipped with two sets of sinusoidally distributed windings having pole numbers P1 and P2. The rotor consists of simple saliencies of pole number Pr, which is shown to be constrained to particular values by P1 and P2. A d-q-n model and equivalent circuit is developed for this machine. Simulation results using the new model show that this machine can have the advantages of doubly-fed wound-rotor machine while eliminating the complicated wound rotor, brushes and slip rings normally associated with doubly fed machines.