Dual Stator Winding Research Articles

An Isolated Three-Phase Induction Generator System With Dual Stator Winding Sets Under Unbalanced Load Condition

This paper presents a stand-alone wind-based dual-stator-winding induction generation (DWIG) system under unbalanced load conditions. The DWIG consists of a cage-rotor and a stator with two sets of three-phase windings with the same number of pole-pairs. The first winding is fed by a three-phase STATCOM and is used to excite the machine. The STATCOM main frequency is chosen to be equal to generator load frequency. Since two stator windings share the same working frequency, the output frequency is independent of the generator load power demand, and its prime mover speed. The second stator winding is connected to the load. Assuming a three-phase unbalanced load, the main aim of this paper is to use conventional proportional-integral (PI) controllers for three different control targets. In the first target, the PI controllers are used to regulate the load positive-sequence-voltage while simultaneously removing the load negative-sequence-voltage. In the second and third control targets, the positive-sequence-voltage is regulated while simultaneously removing either the load negative-sequence-current or the load active power double-frequency-component. A separate PI regulator is used to regulate the STATCOM dc-link voltage by obtaining the rotor reference speed. Some simulation and experimental results are presented to prove the validity and effectiveness of the proposed system.

Dual Stator Winding Induction Machine: Problems, Progress, and Future Scope

This paper gives an overview of the topological variations of multi-winding induction machines (IMs) and drives. The study is restricted to IMs having two distributed windings on the stator and a brushless rotor. The mathematical modeling techniques and control algorithms available in the literature are highlighted. Being magnetless and brushless, a Dual Stator Winding IM is highly reliable, maintenance free, and economic. Thus, it possesses the necessary potential to become a part of ac and dc microgrids. Recent research trend shows growth in the application of such generators for off-grid and grid-connected systems.

A New Dual-Stator Bidirectional-Modulated PM Machine and Its Optimization

A novel dual-stator bidirectional-flux modulated permanent magnet (PM) machine is presented in this paper. The key of the design is to locate consequent PM poles in both stator and rotor sides and the merit is that the magnetic flux produced by either the rotating or stationary PMs and dual-stator windings can be modulated by the stator teeth and rotor iron segments. It is shown that with this flux modulation effect and improved reluctance torque effect, the torque density of the machine can be increased. The bidirectional flux modulation theory and operation principle of the machine are explained and analyzed using time-stepping finite element method.

A Research on the DC-Link Current and Capacitance of the Static Excitation Regulator on a 12/3-Phase Dual Stator-Winding Induction Generator

By proper simplifications, the static excitation regulator on the 12/3 phase dual stator winding induction generator is described by the switch-function model. On this basis, the switch-function expression of the DC-link capacitor current is obtained and the physical meanings are discussed, and the detailed exchange procedures between the generator and capacitor are analyzed. Considering the voltage endurance capability of the capacitor and IGBT, and the current endurance capability of the capacitor, the limitation capacitance equation of the DC-link capacitor is proposed.

Analysis and control of dual stator winding induction motor

Analysis and control of dual stator winding induction motor The paper presents the mathematical models of dual stator squirrel-cage induction motor, formulated in phase coordinate system and in general transformed space vector form. The two types of models of dual stator induction motor are considered. The control systems of field-oriented control (IFOC and DFOC) and direct torque control (DTC) of the dual stator induction motor have been described and discussed.

Performance Analysis of Doubly Excited Brushless Machine with Radially Laminated Magnetic Barrier Rotor

The performance of a doubly excited brushless machine (DEBM) with radially laminated magnetic barrier rotor (RLMB-rotor) is investigated by using the 2D transient finite element analysis model and the experimental method. The magnetic fields, the mutual coupling of the dual stator windings, the no-load characteristics and the electromagnetic torque characteristics of the sample machine are presented. The results of the experiment validate the theoretical analysis and simulation results.

Evaluation of magnetic forces in an induction machine with dual stator winding taking into account hysteresis model

PurposeDesigners of electrical machines need a clear understanding of the mechanism of noise generation, in order to be able to reduce the noises which are produced under the influence of forces due to the magnetic field. The purpose of this paper is to develop a new approach to give a best estimation of these forces.Design/methodology/approachA model is developed to calculate the distribution of local forces using the virtual work principle in finite element context including ferromagnetic hysteresis. The forces are calculated using a formulation based on the energy derivation. The nonlinear behaviour of ferromagnetic material is considered by combining a Jiles‐Atherton model and finite element method through the fixed‐point iterative technique.FindingsThe effects of accurate behaviour of magnetic material are not always taken into account when calculating the local forces in electromagnetic devices. The introduction of hysteresis phenomenon in the analysed device gives a good prediction of magnetic induction. The expression used to compute the force includes an integral which is estimated numerically and not a constant term.Originality/valueThe developed approach is more accurate than the classical methods using constant magnetic permeability or a first magnetization curve.

Total Airgap Flux Minimization in Dual Stator Winding Induction Machines

Multiphase machines are gaining attention in specific applications due to their increased reliability and the possibility to split the power between more than one inverter. Dual stator winding machines can be seen under certain conditions as two independent induction machines coupled by the rotor. To ensure control independence of both windings, airgap flux saturation must be avoided. Proper flux synchronization of both windings is required to achieve this goal while maximizing the torque per ampere ratio of the machine. The conditions to obtain proper orientation of the fluxes are discussed in this paper, and the inverter control scheme to perform such orientation is developed.

Total Airgap Flux Minimization in Dual Stator Winding Induction Machines

Multiphase machines are gaining attention in specific applications due to their increased reliability and the possibility to split the power between more than one inverter. Dual stator winding machines can be seen under certain conditions as two independent induction machines coupled by the rotor. To ensure control independence of both windings, airgap flux saturation must be avoided. Proper flux synchronization of both windings is required to achieve this goal while maximizing the torque per ampere ratio of the machine. The conditions to obtain proper orientation of the fluxes are discussed in this paper, and the inverter control scheme to perform such orientation is developed.

Flux level selection in vector-controlled dual stator winding induction machines

The dual stator winding induction machine has two three-phase stator windings with dissimilar number of poles. This machine can be regarded from the point of view of control as two different induction machines coupled by a rotor. To improve the machine's performance, the total flux generation must be correctly distributed between the two windings. This study focuses on the flux distribution necessary to achieve a nearly maximum torque per stator ampere operation, which is indicated in applications requiring high dynamics. In addition, efficiency and voltage utilisation will be also considered.

Optimal design of a self-excited capacitor in a dual-stator winding induction generator

The design requirement of the self-excited capacitor in a dual-stator winding induction generator (DSWIG) is different from that of the conventional induction generator, because there are numerous combinations between the reactive capacitance of two windings. The efficiency optimisation is taken as the design aim for a self-excited capacitor in this paper. Based on the equivalent circuit model of the induction generator-rectifier system, the characteristic analysis of a three-phase bridge rectifier with an AC capacitor is presented, especially the comprehensive analysis on the condition with neglecting commutation angle. Moreover, the relation between self-excited capacitor and corresponding stator loss is derived, and the value of self-excited capacitor at maximum efficiency is obtained. The coincidence between the experimental results and analytical results verifies the validity of the analytical method. The results obtained herein are of importance to the optimal design of the self-excited capacitor in DSWIG.

Eccentricity Fault Diagnosis of a Dual-Stator Winding Induction Machine Drive Considering the Slotting Effects

To point out the effects of eccentricity within a dual-stator winding induction machine, one needs to detect the high frequency corresponding to the interaction of both eccentricity and slotting effects. In this paper, a model of this kind of machine, whose rotor is mixed-eccentric, has been suggested. One considers slotting effects. This induction machine has two sets of stator three-phase windings electrically shifted by an angle alpha. This model will be used to analyze the impact of the defect on the machine. It will be seen that the analytical expression of inductances can be directly exploited to predict the eccentricity-related frequencies. First, the impact of the defect will be investigated under an open-loop condition, i.e., the motor will be supplied by the volt-per-hertz control mode. Second, the motors will be supplied by using the indirect rotor field-oriented control. One will see the fault propagation on the control variables, which can be used as a tool for diagnosis under closed-loop conditions. Comparisons between simulation and experimental results will be performed to evaluate the effectiveness of this experiment.

Research on dual-stator winding multi-phase high-speed induction generator with rectifier load

Based on analysis and calculation of the relation between current harmonics and MMF harmonics in the dual-stator winding multi-phase high-speed induction generator with a rectifier load, a new idea, which divides the generator system into two sub-systems to be analyzed individually, is presented. For the sub-system of the 12-phase power winding with a rectifier load, the loop current method is used to establish network equation set in terms of the network graph theory. The numerical stability problem is solved by alternating use of fixed time-step and varied time-step, and the voltage and current with their fundamental components of the power winding are obtained. For the other sub-system of the induction generator with dual-stator winding and solid cage rotor, the electromagnetic field analysis method and the multi-variable optimization approach are combined to get the control winding current and stator frequency. Calculated results well match experiment results, indicating that the new proposed method is of effectiveness and high accuracy.

High-Performance Control of a Dual Stator Winding DC Power Induction Generator

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper investigates the use of a dual stator winding squirrel-cage induction machine for generating dc power using series- or parallel-connected ac–dc pulse width modulation rectifiers. The operating principles and constraints when generating under minimum total copper-loss condition are explored using the machine steady-state model considering magnetizing flux saturation effects. Regulation of the dc voltage using concepts of the nonlinear input-output linearization method including the design of the controllers is set forth and confirmed to be effective by computer simulation results. Some experimental waveforms of the generator under load are also included in this paper. </para>

On the Modeling and Design of Dual-Stator Windings to Minimize Circulating Harmonic Currents for VSI Fed AC Machines

The major drawback of usual dual-stator ac machines, when supplied by a voltage-source inverter (VSI), is the occurrence of extra harmonic currents. These extra currents circulate only in the stator windings and cause additional losses. This paper deals with the modeling and design of dual-stator winding ac machines for safe operation with a VSI. A new reference frame model for a dual-stator induction machine (DSIM), including mutual leakage coupling, is proposed. This model allows us to highlight the previously mentioned circulating harmonic currents. The leakage inductance associated with these harmonics is shown to have quite a small value, highly depending on the coil pitch. It is also shown that full pitch is required, and that special slot shape designs should be investigated, to limit the magnitude of circulating currents. Experimental results on a prototype of a DSIM are presented and they show a very good correlation with theoretical curves.

PWM-VSI inverter-assisted stand-alone dual stator winding induction generator

This paper presents a novel usage of a dual stator winding three-phase induction machine as a stand-alone generator with both controlled output load voltage magnitude and frequency. This generator, with both three-phase power and control windings housed in the stator structure, has the load connected to the power winding and a three-phase pulsewidth modulation (PWM) voltage-source inverter sourcing the control winding. The input to the PWM inverter is either a battery source or a charged DC capacitor. The operational characteristics of these generator schemes with either of the two inverter sources are investigated and shown to have desirable performance. How the load voltage magnitude depends on the various control and design parameters such as rotor speed, compensating capacitance, and load impedance is determined using a detailed mathematical model of the system.

Dual stator winding induction machine drive

A new dual stator winding induction machine drive is described in this paper. The proposed induction machine consists of a standard squirrel-cage rotor and a stator with two separate windings wound for a dissimilar number of poles. Each stator winding is fed from an independent variable-frequency variable-voltage inverter. The proposed drive offers such advantages as speed sensorless operation, better reliability, and more flexibility to manipulate the resultant torque-speed curve of the motor. In the proposed drive, zero-speed operation is achieved by independently controlling the two sets of stator currents, hence, maintaining a minimum electrical frequency independent of the mechanical speed. This feature is especially important to minimize the negative impact of the stator resistance influence at low-speed operation and it greatly simplifies the implementation of speed sensorless control schemes. The drive is well suited for either constant volts per hertz or field-oriented (FO) operation. Circulating harmonic currents, common to most dual stator machines, are eliminated by the dissimilar pole number in each stator winding.

Analysis of a Novel Stator Winding Structure Minimizing Harmonic Current and Torque Ripple for Dual Six-Step Converter-Fed High Power AC Machines

Many attempts have been made to expand the application of ac drives to high-power levels. One way to use ac drives at high-power levels is to use multiple power converters together to supply power to a large machine. For a multiple converter combination scheme, the six-step converter is competitive due to its robust structure and simplicity of control. In our previous study, an ac drive with dual stator windings fed by dual six-step converters was proposed. Two sets of electrically isolated windings are placed in the stator slots, and one set is shifted from the other by 30° in space. Two converters are used to power the dual windings, and the phase voltages from the two converters are also shifted 30° from each other in time. The 5th and 7th harmonics of the airgap flux and rotor currents are reduced dramatically, and the output torque from the drive is superior to that of the drive which is singly fed from a six-step converter. However, for each individual six-step converter, the 5th and 7th harmonic currents are found to be substantial and the functioning of the power converter evidently is deteriorated. In this paper, we propose a novel stator winding structure and control strategy to solve the converter problem. Principles associated with the new stator winding are discussed and a practical implementation presented.

Comparison study of rotor structures of doubly excited brushless reluctance machine by finite element analysis

Doubly excited brushless reluctance machine (DEBRM) has gained much attention in the area of variable-speed constant-frequency generating systems and adjustable speed drives. Two types of reluctance rotor structure, axially laminated and simple salient rotors, are suggested in the DEBRM development. Due to the unconventional pole number combination of the stator and rotor, performance evaluation of the DEBRM with different rotor structures is difficult. A comparison study of two rotor structures of the DEBRM is presented in this paper by finite element analysis. It is shown that by calculating selfand mutual-flux linkage of the dual stator windings as the function of rotor positions, performance of the complicated DEBRM can be evaluated conveniently. Various advantages and disadvantages of the DEBRM associated with the two rotor structures are also discussed. >