Derivation of Equivalent Circuit Rotor Current From Rotor Bar Current Measurements in Brushless Doubly-Fed Machine

This paper studies the effects of magnetic wedges on the equivalent circuit parameters of the Brushless Doubly-Fed Machine (BDFM). Magnetic wedges are used in slot openings of large electrical machines to reduce magnetizing currents, but the study of their effects on the BDFM performance is not straightforward due to the complex magnetic fields in the BDFM. Equivalent circuit and FE models have been developed for a 250 kW BDFM taking into account the effects of wedges and verified experimentally.

In order to make brushless doubly-fed machines (BDFM) cost effective to manufacture, diecasting must be employed to produce the specialized rotor. Since BDFM rotors require insulation between the bars and stack (also a concern for high efficiency induction machines), an investigation was undertaken assessing different stack treatments to provide insulation. Ten rotors were cast, using several pre and post casting treatments. The performance of some rotors compared favorably to an existing noncast manufactured BDFM rotor with close to ideal insulation. These results indicate that diecasting of BDFM rotors is feasible.

Brushless doubly fed machine (BDFM) shows promising results for wind power and adjustable-speed drive applications. Due to poor rotor magnetic coupling and relatively high value of slip, core loss is more emphasized in this machine than the conventional machines. By now, there are few comprehensive researches on core loss effect on performance characteristics of BDFM in the literature. In this paper, based on the derived relations and by applying suitable rules for transformation of parameters from one winding to another one, the steady state equivalent circuit model of BDFM referred to power winding stator side is obtained. Comparison between simulation and experimental results verifies the accuracy and effectiveness of the proposed model.

The brushless doubly-fed machine (BDFM) is a new type of induction machine with good application in wind power generation. In this paper, the design method for the stator winding and rotor winding of BDFM in detail on the basis of operation principle of the machine is introduced. As an example, The performance simulation for a 480kW cage rotor BDFM with 8-pole stator power winding and 4-pole control winding can be considered under the condition of no-load, rated load and variable speed constant frequency operation based on field-circuit coupled finite element analysis. Simulation results show that the design method has good performance and is feasible in variable speed constant frequency wind generation systems.

This paper studies the unbalanced magnetic pull (UMP) in the Brushless Doubly-Fed Machine (BDFM). Analytical study is performed to derive the UMP, then, Finite element (FE) analysis, which has been verified experimentally, is used to verify the analytical method. The BDFM with different types of rotor eccentricities including static and dynamic eccentricities, are also modeled in FE method and their resultant UMPs are obtained. The results are compared with the case at which a perfectly constructed rotor is considered. The study has been carried out on a prototype D400 250 kW BDFM.

The brushless doubly-fed machine is a machine which incorporates the robustness of the squirrel cage induction machine and the speed and power factor control of a synchronous machine. The electromagnetic environment within the brushless doubly-fed machine is investigated using simple formulae in order to develop an intuitive feel for the mechanism which enables precise speed control of the machine. The concept of cross-coupling from one stator winding to the other via the rotor is described and verified by experiment.

In this study, the steady-state operation of the brushless doubly-fed machine (BDFM) in various modes is physically elaborated and the active power flow and torque analysis are presented for each operating mode alongside confirmatory experimental results on a 4/8 pole D160 size machine. The machine behaviour in asynchronous operating modes is described similar to the conventional induction machines with corresponding pole numbers. Moreover, its performance in synchronous mode is shown to be similar to synchronous machines. On the basis of the above, the BDFM performance is further analysed under two possible fault conditions: first, a controller or converter fault leading to loss of synchronism is considered, where the asynchronous, double-cascade mode must be introduced to describe the machine performance. Second, a voltage dip at the mains terminal is considered. The simplistic behaviour of the BDFM during this fault, including the operation of a converter protective crowbar, is investigated using steady-state torque–speed curves to obtain a general view of the machine performance.

This article discusses a high-speed brushless doubly-fed machine (BDFM) for aviation turboelectric distributed propulsion application. After a brief overview of the machine fundamentals and propulsion architecture, the electromagnetic properties of the newly designed BDFM are analyzed. An innovative rotor mechanical design is introduced, which allows for a significant increase of speed compared to legacy rotor designs. Experiments were conducted to verify the 12 000-r/min high-speed operation. The findings in this article will give prominence to the feasibility of applying BDFMs for aviation applications.

Doubly-fed induction machines (DFIMs) have been widely used in wind power generation and high power drives. The brushless versions further improve the reliability and reduce the maintenance cost by eliminating brushes and slip rings, showing great potential in replacing the traditional DFIMs. The successful model-based control development of doubly-fed machines relies heavily on the high fidelity of the plant model, which most of the existing DFIM models lack. This paper proposes a generalized high-fidelity modeling approach by extracting lookup tables from parametric finite element analysis (FEA) sweeps for brushed and brushless doubly-fed machines. It can be applied directly to induction machines by shorting the rotor circuits. The developed model covers the magnetic saturation of machine cores and spatial harmonics introduced by the winding layout and slotting effect. It is suitable for system-level simulations and controller development of doubly-fed machines and induction machines, either in motoring or generating modes, with pure sinusoidal or pulse-width-modulation (PWM) voltages. Detailed modeling implementations and simulation results of a slip-ring DFIM are provided to validate the modeling workflow and showcase the fidelity level compared to time-consuming electromagnetic transient FEA.

Recent developments in power electronic converters have renewed interest in the doubly fed connection of the self-cascaded or concatenated induction machine. These brushless doubly fed machines (BDFMs) utilize die-cast cage rotors and have the potential to provide economical alternatives to regular induction machines in the areas of variable-speed generation, pumped storage, and adjustable-speed drives. Working laboratory prototypes have been constructed to provide both a proof-of-concept and a baseline for design development. Improvements in machine design, based on alternatives for the stator winding, are discussed. Working within the framework set by stator geometry and the cage-rotor design of the proof-of-concept machine, the authors investigate the effects of various design strategies, such as varying the coil span, unconventional winding distribution, providing alternative connections, of incorporating two electrically isolated stator windings. The results derived from a detailed design model are presented. >

This paper presents a mathematical model for Brushless Doubly-Fed Machine (BDFM) based on Stator Flux Orientation (SFO) in positive and negative reference frames under unbalanced grid voltage conditions. A negative controller is designed to eliminate the effects of unbalanced conditions on electrical torque. The model and controller performance during unbalanced conditions is validated by time domain simulation in MATLAB/Simulink.

Brushless doubly-fed machine (BDFM) is a new type of AC induction motor.It has a good applicable prospect as the variable frequency motors or the variable speed constant frequency generators. Although the advantage of the three-level inverter, there are also some problems of neutral point voltage balance in this method such as the unbalance of neutral point voltage. And the traditional principle of Three-level inverter space vector pulse width modulation method is to estimate the sectors and calculating a lot of trigonometric functions. To solve these problems, a novel method for the virtual space vector concept in G-H coordinate system is presented in this paper. The method proposed can omit the judging process of the sectors, reduce the calculating burden, and maintain the balance of neutral-point voltage between capacitances within a certain index modulation. The results of simulation are given to validate the improved virtual space vector modulation.

This paper establishes four kinds of Brushless Doubly-Fed Machine (BDFM) models with radial laminated magnetic-barrier rotor using ANSOFT finite element software, calculates the electromagnetic field of these four kinds of models, comparatively analyzes the magnetic field distribution, the torque capability, the end winding characteristics ,the rotor’s radial magnetic forces, the core losses and the motor operating performance of motor with different rotor structures, and thus provides theoretical guidance for optimization design of radial laminated magnetic-barrier rotor structure.

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.

In this paper, an attempt is made to eradicate the tediousness involved in tuning of brushless doubly-fed reluctance motor (BDFRM) drive for adequate speed tracking. A modified particle swarm optimization is adopted considering the intricacies of a BDFRM drive so that a faster convergence on the Proportional-Integral controller gain parameters can be achieved to obtain desirable speed tracking characteristics. This technique is applied on two different BDFRM drives and is proved to be successful in both the attempts.