Sets Of Three-phase Stator Windings Research Articles

A Low-Cost Wind Generator System with a Permanent Magnet Synchronous Generator and Diode Rectifiers

A low-cost wind generator systemfor small- or medium-scale wind generator is pro-posed. The system consists of a permanent mag-net synchronous generator (PMSG) with two sets ofthe three-phase stator windings, i.e. six-phase sta-tor winding, two three-phase diode rectifiers, a boostchopper, and a three-phase pulse-width modulation(PWM) inverter. Since two sets of three-phase statorwindings are spatially shifted by 30 electrical degrees,the system can cancel out the dominant harmonicmagnetomotive forces (MMF) produced by the har-monic currents of diode rectifiers. The simulation andexperimental results show that the proposed systemcan significantly reduce the pulsation of the devel-oped torque and the DC current by more than 60 %in comparison with the conventional system consist-ing of a three-phase PMSG and a three-phase dioderectifier. Therefore, the proposed system can use asmaller smoothing reactor in the boost chopper, sothat the lower initial cost can be realized, and it issuitable for small- or medium-scale wind generatorsystems.

Predictive current control based pseudo six-phase induction motor drive

Asymmetrical six-phase induction machines are widely used in high-power safety-critical applications. The so-called pseudo six-phase winding layout has recently been proposed as a promising contender for high power medium voltage applications in terms of torque density, phase current quality, simple single-layer-based stator winding design, and fault-tolerant capability. This winding layout employs quadruple three-phase stator winding sets connected to provide only six terminals, while being fed from two three-phase inverters. Therefore, the same conventional six-phase-based control structure can still be employed. Among the different control techniques, model predictive current control is considered as one of the cutting-edge technologies for multiphase drive systems, thanks to its simplicity and flexibility in defining new control objectives. This paper investigates how the available 64 voltage vectors of a six-phase inverter are classified among different subspaces when employing a pseudo six-phase stator winding. Moreover, the required modifications to classical predictive current control (PCC) are introduced in order to properly control the machine in a manner similar to conventional asymmetrical six-phase machines while ensuring minimum circulating xy current components. The concept of virtual voltage vectors (VVVs) has also been employed to further enhance the stator current quality. The proposed controller is validated using a 2Hp prototype pseudo six-phase machine under different operating conditions. An experimental comparative study with an asymmetrical six-phase machines is also carried out to verify the claimed equivalence.

Direct Torque Control of Dual Three-Phase Permanent Magnet Synchronous Motor

In this paper a direct torque control strategy for dual three-phase permanent magnet synchronous motor (DTP-PMSM) is presented, the machine has two sets of three-phase stator windings spatially phase shifted by 30 electric degrees. In order to reduce the stator harmonic current, torque and flux are controlled based on regulators and Vector Space Decomposition technique. The proposed approach has the benefits of low stator current distortion and low torque ripple. The validity and the efficiency of the selected technique are confirmed by simulation results.

A New Control Strategy of Dual Stator Induction Generator with Power Regulation

In this paper modelling and analysis of stand-alone dual stator induction generator (DSIG) with non-identical parameters under a new method has been done. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. One supplied power to the DC load via a rectifier bridge and AC capacitors, and the other was connected to the battery banks by an inverter to store energy and restore it to regulate the power of the first stator in weak wind. We develop the steady state model and show the performances of different configurations by the simulation results.

An Improved Torque Density Pseudo Six-Phase Induction Machine Using a Quadruple Three-Phase Stator Winding

The nine-phase six-terminal induction machine has recently been proposed as a promising contender to the conventional six-phase asymmetrical winding machine in terms of torque density, phase current quality, stator winding simplicity, and fault-tolerant capability. However, the relatively lower dc-link voltage utilization of a single neutral arrangement in multiphase machines with multiple three-phase windings represents, in general, a technical challenge when compared to windings with isolated star points. Therefore, this paper proposes a new pseudo six-phase winding layout suitable for medium-voltage high-power induction machines, which employs quadruple three-phase stator winding sets, while providing the same terminal behavior of a nine-phase six-terminal winding. Additionally, like the traditional six-phase winding, two possible neutral arrangements can be configured. The proposed winding configuration provides the same dc-link voltage utilization as in conventional dual three-phase winding machines with isolated neutrals. The effect of the circulating zero-sequence current component experienced with a single neutral arrangement can also be avoided. A 1.5 Hp prototype induction machine is used to experimentally validate the proposed six-phase winding layout under both healthy and fault conditions.

Double Three-phase Induction Machine Modeling for Internal Faults Simulation

Multi-phase induction motors present excellent characteristics for faulty tolerant operation. Among them, six-phase induction motors, which are among the most used, exhibit two types of configuration: the double three-phase and the six-phase with single neutral. The double three-phase presents the advantage of reducing harmonics with its symmetric winding. This article presents a new modeling of the double three-phase induction machine for internal faults simulation. The developed model is composed by two sets of three-phase stator windings forming two stars. The model considers an arbitrary displacement (α) between stator stars, allowing the simulation of this type induction machines with different configurations, with 60° displacement used herein. The simulations of internal faults, such as stator windings or rotor faults, are both considered in the proposed model, allowing the machine study under abnormal conditions. The double three-phase induction machine model was fully implemented in real coordinates, making it possible to simulate stator and rotor faults without being necessary to change system equations coordinate. Several examples allow verifying the characteristics of the proposed model and its application for internal fault analysis. Experimental results are also presented to validate the obtained simulation results.

Sensorless control of a dual‐airgap axial flux permanent magnet machine for flywheel energy storage system

This study presents the sensorless vector control of a dual-airgap axial flux permanent magnet (AFPM) machine optimised for use in flywheel energy storage system (FESS) applications. The proposed AFPM machine has two sets of three-phase stator windings but only requires a single power converter to control both electromagnetic torque and axial levitation force. The proper controllability of the latter is crucial as it can be utilised to minimise the vertical bearing stress to improve the efficiency of the FESS. The method for controlling the speed and axial displacement of the machine is discussed. An inherent speed sensorless observer is also proposed for speed estimation. The proposed observer eliminates the rotary encoder, which in turn reduces the overall weight and cost of the system while improving its reliability. The effectiveness of the proposed control scheme has been verified by simulations and experiments on a prototype machine.

Modeling and Position-Sensorless Control of a Dual-Airgap Axial Flux Permanent Magnet Machine for Flywheel Energy Storage Systems

This paper presents the modeling and position-sensorless vector control of a dual-airgap axial flux permanent magnet (AFPM) machine optimized for use in flywheel energy storage system (FESS) applications. The proposed AFPM machine has two sets of three-phase stator windings but requires only a single power converter to control both the electromagnetic torque and the axial levitation force. The proper controllability of the latter is crucial as it can be utilized to minimize the vertical bearing stress to improve the efficiency of the FESS. The method for controlling both the speed and axial displacement of the machine is discussed. An inherent speed sensorless observer is also proposed for speed estimation. The proposed observer eliminates the rotary encoder, which in turn reduces the overall weight and cost of the system while improving its reliability. The effectiveness of the proposed control scheme has been verified by simulations and experiments on a prototype machine.

Sliding mode control of a dual-stator induction generator for wind energy conversion systems

This paper presents a sliding mode control (SMC) associated to the field oriented control (FOC) of a dual-stator induction generator (DSIG) based wind energy conversion systems (WECSs). The DSIG has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The study of operation of the wind turbine leads us to two essential cases: optimization of the power for wind speeds lower than the nominal speed of the turbine and limitation of the power for higher speeds. Conventional electrical grid connected WECS present interesting control demands, due to the intrinsic nonlinear characteristic of wind mills and electric generators. The SMC is a robust nonlinear algorithm which uses discontinuous control to force the system states trajectories to join some specified sliding surface, it has been widely used for its robustness to model parameter uncertainties and external disturbances, is studied. In order to verify the validity of the proposed method, a dynamic model of the proposed system has been simulated, to demonstrate its performance.

Direct Torque Control Based Three Level Inverter-fed Double Star Permanent Magnet Synchronous Machine

In this paper, direct torque control (DTC) algorithms for double star permanent magnet synchronous machine alimented by two inverters is described. The double star permanent magnet synchronous machine has two sets of three-phase stator windings spatially shifted up by an angle γ=300. The double star permanent magnet synchronous is used in areas of high power industrial applications such as traction and naval propulsion. Because constitute an advantageous choice compared to classical synchronous machine, because of the relatively low torque produced. This machine is controlled by tree level direct torque with speed regulator PI, replaced by the sliding mode regulator to improve the results obtained. The implementation of the DTC multi-level applied to a double star permanent magnet synchronous machine is validated with simulated results. In this paper a method for modeling and simulation of double star permanent magnet synchronous motor drive MATLAB/Simulink.

A General Model for Describing the Performance of Brushless Doubly-Fed Induction Machines

This paper presents a generalized model, by which the dynamic and steady-state behaviour of the Brushless Doubly-Fed Induction Machine (BDFIM) can be precisely predicted. The investigated doubly-fed machine has two sets of three-phase stator windings with different pole numbers. The rotor is a squirrel-cage type with a simple modification in order to support the two air-gap rotating fields that are produced by the stator windings and have different pole numbers. The machine model is derived in the qdo-axis variables. The qdoaxes are attached to rotor and hence, it rotates at the rotor speed (

A Proof of Concept Study of Predictive Current Control for VSI-Driven Asymmetrical Dual Three-Phase AC Machines

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Multiphase (more than three phases) drives possess interesting advantages over conventional three-phase drives. Over the last years, various topics related to the extension of the classical control schemes to these specifics drives have been covered in depth in literature, such as vector control of a six-phase induction machine with two sets of three-phase stator windings spatially shifted by 30 electrical degrees (also called asymmetrical dual three-phase ac machine). In this paper, a model-based predictive control (MBPC) for the current regulation of asymmetrical dual three-phase ac machines is analyzed. MBPC overcomes the difficulties of multiphase current control, avoiding complex controllers and modulation techniques, but at the expense of an increased computational cost. Simulation results are provided to examine the potential of the control method. The influence of the number of voltage vectors considered to evaluate the predictive model is studied, and different cost functions are analyzed. The computation time needed for the implementation of the control method is discussed to prove its real-time feasibility. Finally, experimental results are given to illustrate the capability of the control method. </para>

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.

A New PWM Strategy Based on a 24-Sector Vector Space Decomposition for a Six-Phase VSI-Fed Dual Stator Induction Motor

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a new space vector pulsewidth modulation (SVPWM) technique for the control of a six-phase voltage source inverter (VSI)-fed dual stator induction machines (DSIM). A DSIM is an induction machine which has two sets of three-phase stator windings spatially shifted by 30 electrical degrees and fed by two three-phase VSIs. Despite their advantage of power segmentation, these machines are characterized by large zero sequence harmonic currents, and in particular those of order <formula formulatype="inline"> <tex>$6k\pm 1$</tex></formula>, which are due to the mutual cancellation between the two stator windings. The proposed SVPWM scheme, while easy to implement digitally, reduces significantly these extra stator harmonic currents. Experimental results, collected from a 15 kW prototype machine controlled by a digital signal processor, are presented and discussed. </para>

Efficiency Analysis of PWM Inverter Fed Three-Phase and Dual Three-Phase High Frequency Induction Machines for Low/Medium Power Applications

A performance analysis of three-phase and dual three-phase (DTP) induction pulsewidth modulation (PWM) inverter-fed motor drives is conducted in this paper. The focus is on the efficiency performance of high-frequency DTP machines compared to their three-phase counterparts in low/medium power applications. For this purpose, a DTP machine, having two sets of stator three-phase windings spatially shifted by 30 electrical degrees (asymmetrical six-phase winding configuration), was tested for both six-phase and three-phase winding configurations under the same magnetic conditions. Simulation and experimental results are presented to evaluate the efficiency performance of three-phase and dual-three induction motor drives employing PWM voltage source inverters.

Vector Control of Dual-Three-Phase Induction-Motor Drives Using Two Current Sensors

A rotor field-oriented control (RFOC) scheme, employing only two current sensors, is presented in this paper for a dual-three-phase induction-machine drive. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The reduction of the current sensor count, which is possible due to the particular machine structure, does not affect significantly the performance of the vector-control scheme. Experimental results are presented for a 10-kW RFOC dual-three-phase induction-motor-drive prototype to demonstrate the feasibility of the proposed solutions

Dual three-phase induction motor drive with digital current control in the stationary reference frame

Vector control of a dual three-phase induction machine, with two sets of three-phase stator windings spatially shifted by 30 electrical degrees, is elaborated in the paper. The stator windings are fed from a current-controlled PWM six-phase IGBT voltage source inverter (VSI). The main problem in realisation of such a drive is an adequate current control algorithm, which has to cope with the inherent asymmetries of the drive. Furthermore, the digital implementation has to ensure zero steady state current error for the whole frequency range of the drive. After reviewing the existing solutions, the paper proposes a current control scheme that is based on four digital current controllers in the stationary reference frame. A design procedure for the current controllers is presented and current controllers are implemented in a laboratory test rig, in conjunction with a previously developed PWM scheme that provides operation with low values of low-order output voltage harmonics. Experimental tests are conducted and the results are given for a direct rotor field oriented control (DRFOC) of a 10 kW dual three-phase induction motor drive prototype. The results confirm the validity of the control scheme.

Direct Torque Control with Full Order Stator Flux Observer for Dual-Three Phase Induction Motor Drives

A Direct Torque Control (DTC) strategy for dual-three phase induction motor drives is discussed in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees with isolated neutral points. The proposed control strategy is based on Proportional Integral (PI) regulators implemented in the stator flux synchronous reference frame. To improve the flux estimation, an Adaptive Stator Flux Observer (ASFO) has been used. Doing so, besides a better flux estimation in contrast to open-loop flux estimators, it is possible to use the observed currents to compensate the inverter non-linear behavior (such as dead-time effects), improving the drive performance at low speed. This is particularly important for low voltage/high current applications, as the drive considered in this paper.The advantages of the discussed control strategy are: constant inverter switching frequency, good transient and steady-state performance and less distorted machine currents in contrast to DTC schemes with variable switching frequency. Experimental results are presented for a 10kW dual three-phase induction motor drive prototype.

Direct Torque Control for Dual Three-Phase Induction Motor Drives

A direct torque control (DTC) strategy for dual three-phase induction motor drives is discussed in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The DTC strategy is based on a predictive algorithm and is implemented in a synchronous reference frame aligned with the machine stator flux vector. The advantages of the discussed control strategy are constant inverter switching frequency, good transient and steady-state performance, and low distortion of machine currents with respect to direct self-control (DSC) and other DTC schemes with variable switching frequency. Experimental results are presented for a 10-kW DTC dual three-phase induction motor drive prototype.

Direct Torque Control Schemes for Split-Phase Induction Machine

In this paper, direct torque control (DTC) algorithms for a split-phase induction machine (SPIM) are established. An SPIM has two sets of three-phase stator windings, with a shift of thirty electrical degrees between them. The significant contributions of this paper are: 1) two new methods of DTC technique for an SPIM are developed, called Resultant Flux Control Method and Individual Flux Control Method and 2) advantages and disadvantages of both methods are discussed. High torque ripple is a disadvantage for three-phase DTC. It is found that torque ripple in an SPIM can be significantly reduced without increasing the switching frequency.