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

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 6 k plusmn 1, 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.     

A harmonic elimination and suppression scheme for an open-end winding induction motor drive

In this paper, a harmonic elimination and suppression scheme for a dual-inverter-fed open-end winding induction motor drive is presented. Two isolated dc-link sources with voltage ratio of approximately 1 : 0.366 are required for the present drive. These two isolated do links feeding two inverters to drive the open-end winding induction motor eliminate the triplen harmonic currents from the motor phase. The pulsewidth-modulation scheme proposed enables the cancellation of all the 5th- and 7th-order (6n /spl plusmn/ 1, where n = 1, 3, 5, 7, etc.) harmonic voltages and suppresses the 11th- and 13th-order harmonic voltage amplitudes in the motor phase voltage, in all modulation ranges. The next higher order harmonics present in the motor phase voltages are 23rd, 25th, 35th, 37th etc. (6n /spl plusmn/ 1, n = 4, 6, etc.). By using triangular carrier wave and proper modulating waves for each inverter, the open-end winding induction motor can be operated in the entire modulation range, eliminating all the 6n /spl plusmn/ 1 harmonics (n = 1, 3, 5, 7, etc.) coupled with 11th and 13th harmonic suppression. The proposed scheme also gives a smooth transition to the overmodulation region.     

六相异步电机的ANSOFT有限元分析

使用最为广泛的交流电机是三相电机,但是由于多相电机可靠性高、谐波成分小、性能好,多相电机将被广泛的应用。利用ANSOFT软件对相同定转子结构的三相电机和六相电机进行有限元分析,得到了三相电机和六相电机的空载磁力线、气息磁密分布曲线及其谐波含量、电机启动时的速度曲线及转矩曲线。分析结果表明,相同结构的三相电机和六相电机的性能基本相同;与三相电机相比,六相电机的5次、7次谐波基本消除,有利于电机效率的提高。     

Sensorless control of induction Machines at zero and low frequency using zero sequence currents

This paper considers both flux and rotor position estimations for sensorless control of delta-connected cage induction machines (IMs) at low and zero frequency operation. The variation of leakage inductance due to either saturation or rotor slotting is tracked by measuring the derivative of the zero sequence current in response to the application of appropriate voltage test vectors. The method requires only a single extra sensor. It requires access to machine phase windings and is appropriate for integrated-type induction motor drives. Both a closed-slot and an open-slot machine is used to demonstrate rotor flux and rotor position tracking, respectively. Experimental results are presented showing sensorless torque control and sensorless speed and position control at low and zero frequencies.     

Direct self control with minimum torque ripple and high dynamics for a double three-level GTO inverter drive

A highly dynamic control scheme with very low torque ripple-direct self control (DSC) with torque hysteresis control-for very high-power medium-voltage induction motor drives fed by a double three-level inverter (D3LI) is presented. In this arrangement, two three-level inverters that are connected in parallel at their DC sides are feeding the open motor windings. The DSC, well known from two- and three-level inverters, is adapted to the D3LI and optimized for a minimum torque ripple. An 18-corner trajectory is chosen for the stator flux of the induction machine since it is approaching the ideal circle much better than the hexagon known from DSC for two-level inverters, without any detriment to the torque ripple. The machine and inverter control are explained and the proposed torque quality and dynamics are verified by measurements on a 180-kW laboratory drive.     

An innovative direct self-control scheme for induction motor drives

The paper presents a new direct self-control (DSC) scheme for induction motor drives using the stator voltage third harmonic component in order to estimate the air-gap flux and the torque as well as to synchronize the supply voltage vector. Compared to previous DSC schemes the new one is independent from any motor parameter variation, specifically on stator resistance thus showing better performances at low speeds. The paper starts with a quick review on standard DSC main features pointing out the influence of stator resistance variations on the flux and torque control. The new DSC scheme is then introduced and evaluated by simulations and experimental tests on a 1.5 kW induction motor drive     

直接转矩控制全阶磁链观测器的设计及离散仿真

在交流异步机数学模型的基础上,建立异步电机直接转矩控制系统。对电机状态值和测量值之间偏差进行反馈校正,并把反馈校正项与估计磁链的电机数学模型结合起来,建立含有闭环状态估计的误差补偿器的全阶磁链观测器;利用Matlab／Simulink构建全阶磁链观测器,对构建的模型进行离散仿真,得到定子磁链的仿真波形,验证了全阶磁链观测器的正确性。     

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.     

Winding distribution effects on induction motor rotor fault diagnosis

The sidebands around stator currents harmonics as a potential tool for supporting the diagnosis of rotor faults in induction motors are analyzed in this paper. The presence of broken bars introduces high frequency components in the machine currents spectrum in addition to the characteristic sidebands around the fundamental component. These additional components are due to the interaction between, rotor asymmetry and either the voltage harmonics, or winding distribution, or rotor slots. In particular, the components at frequencies near to fifth and seventh harmonics, produced by the interaction between the rotor faults and the harmonics of the spatial distribution of stator windings, are analyzed in this work. A multiple coupled circuit model of the induction motor is used to evaluate the sensitivity of these components for different stator winding configurations, load level, supply voltage conditions, and different number of broken bars. Simulation results showed that a particular analyzed component near to fifth harmonic depends mainly on fifth harmonic of winding distribution, which remains almost constant for most common distributions. Therefore, it is expected that this component should be found in most motors with broken bars. Finally, experimental laboratory results and two industrial cases that validate the analysis are presented.     

Speed-sensorless sliding-mode torque control of an induction motor

Novel induction motor control optimizing both torque response and efficiency is proposed in the paper. The main contribution of the paper is a new structure of rotor flux observer aimed at the speed-sensorless operation of an induction machine servo drive at both low and high speed, where rapid speed changes can occur. The control differs from the conventional field-oriented control. Stator and rotor flux in stator fixed coordinates are controlled instead of the stator current components in rotor field coordinates i_sd and i_sq. In principle, the proposed method is based on driving the stator flux toward the reference stator flux vector defined by the input command, which are the reference torque and the reference rotor flux. The magnitude and orientation angle of the rotor flux of the induction motor are determined by the output of the closed-loop rotor flux observer based on sliding-mode control and Lyapunov theory. Simulations and experimental tests are provided to evaluate the consistency and performance of the proposed control technique     

一种新颖的双三相感应电机缺相运行矢量控制

双三相感应电机的绕组开路后,运用传统的旋转坐标变换,不能实现转子磁场定向矢量控制。本文推导出不对称绕组结构的解耦旋转坐标变换,并提出了一种基于不对称绕组结构的转子磁场定向矢量控制新颖策略,运用PI调节器,使得定子侧谐波电流最小化,降低定子侧谐波损耗。在MATLAB MATLAB/Simulink仿真软件下,建立相应的仿真模型,仿真结果验证本文所提出控制策略的正确性和有效性。     

Experimental nonlinear torque control of a permanent-magnetsynchronous motor using saliency

In this paper, a new nonlinear control strategy is proposed for a permanent-magnet salient-pole synchronous motor. This control strategy simultaneously achieves accurate torque control and copper losses minimization without recurring to an internal current loop nor to any feedforward compensation. It takes advantage of the rotor saliency by allowing the current (i_d) to have nonzero values. This, in turn, allows us to increase the power factor of the machine and to raise the maximum admissible torque. We apply input-output linearization techniques where the inputs are the stator voltages and the outputs are the torque and a judiciously chosen new output. This new output insures a well-defined relative degree and is linked to the copper losses in such a way that, when forced to zero, it leads to maximum machine efficiency. The performance of our nonlinear controller is demonstrated by a real-time implementation using a digital signal processor (DSP) chip on a permanent-magnet salient-pole synchronous motor with sinusoidal flux distribution. The results are compared to the ones obtained with a scheme which forces the i_d current to zero     

Flux observer with online tuning of stator and rotor resistancesfor induction motors

This paper proposes an adaptive flux observer for induction motors, where stator and rotor resistances are estimated in online environments. The variation of motor parameters during operation degrades the performance of the controller and the flux observer. Among the parameters of induction motors, rotor resistance is a crucial one for flux estimation, and stator resistance also becomes critical in the low-speed region. Under the persistent excitation condition, the proposed method estimates the actual values of stator and rotor resistances simultaneously, which guarantees the exact estimation of the rotor flux. The persistent excitation condition is not satisfied when the electric torque of an induction motor is absent due to the lack of rotor currents. Even in this case, the proposed method achieves the correct estimation of the rotor flux. Simulations and actual experiments show that the rotor flux is estimated in all operating conditions and that both resistances converge to their actual values when the electrical motor torque exists     

Decoupling control of induction motor drives

The decoupling control of induction machines is investigated. Three different schemes for decoupling-control methods based on stator flux, airgap flux, and rotor flux field regulation are developed. The control dynamics of each scheme are outlined and studied. Simulation results are presented to verify that these schemes provide decoupling control with excellent dynamic behavior. The transient and steady-state relationships between slip frequency and torque, under constant stator flux, airgap flux, and rotor flux operations, are simulated and compared. The sensitivity characteristics of the three methods of flux-control, machine fed by impressed currents and voltages, are also compared and studied. A prototype torque-drive system is implemented to demonstrate the decoupling control of a squirrel-cage induction machine     

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.     

A self-tuning closed-loop flux observer for sensorless torquecontrol of standard induction machines

This paper proposes a self-tuning closed-loop flux observer, which provides field-oriented torque control for induction machines without a tachometer. The proposed algorithm combines the best features of harmonic detection and stator voltage integration through the use of a new tuning scheme. The observer accuracy and robustness is augmented by a parameter-independent accurate-speed detector, which analyzes magnetic saliency harmonics in the stator current. The harmonic-detection scheme provides accurate rotor-speed updates during steady-state operation down to 1-Hz source frequency. This additional speed information is used to tune the rotor-resistance parameter of the observer. The tuned observer exhibits improved dynamic performance, accurate steady-state speed control and an extended range of control near zero speed. The algorithm requires no special machine modifications and can be implemented on most existing low- and medium-performance drives. The closed-loop nature of the flux observer, combined with the harmonic-detection scheme, provides flux and speed error feedback, which significantly increases the robustness of sensorless control across the entire speed range     

A Study of Influence of Configurations of the Windings on the Performance of Single Phase Induction Motor with Capacitor Start

The single phase induction motors needs two stator windings to produce rotating magnetic field : one main winding and the other auxiliary winding. The aim of the auxiliary winding is to create the rotating electromagnetic field when the machine is started-up and is afterwards turned off, generally through the centrifugal switch coupled together with the shaft of the machine rotor. The main purpose of this document is to evaluate the influence that the two windings have on the external characteristics of the single phase induction motor . For this purpose , two different kinds of windings were carried out and simulated, with the proposal to obtain some benefits. The main winding and the auxiliary winding were prepared and mounted on a prototype. The simulation was done via software based FEM , to make the extraction and results analysis possible. This results are shown at the end this document.     

Independent Control of Average Torque and Radial Force in Bearingless Switched-Reluctance Motors With Hybrid Excitations

Radial force and torque are the control objectives that determine the machine performance of levitation and rotation in a bearingless switched reluctance motor (BSRM). This paper proposes a control scheme for rotating and levitating a 12/8 BSRM. The motor average torque and radial force are independently controlled with hybrid excitations in main windings and levitation windings. First, the mathematical relationship between radial force and currents, which is utilized in this paper, is derived by using the Maxwell stress tensor method. Then, the proposed control scheme is analyzed. The average torque of each phase generated in the levitation region equals zero for its symmetry of the aligned position. Accordingly, the current calculating algorithm is deduced to minimize the magnitude of instantaneous torque in the levitation region. The principle and realization of the proposed scheme are demonstrated with finite-element (FE) analysis. Experimental results show that the proposed scheme is effective for a stable levitation.      

Characteristics and control of a bidirectional axial gap combinedmotor-bearing

Introduces the design characteristics of a bidirectional axial gap combined motor-bearing where the flat disc motor has both rotation and axial position control capability. This motor consists of a disc rotor with a stator on each side of the rotor. The axial motion of the rotor is actively controlled while the other axes are constrained by additional passive or active radial magnetic bearings. Each stator produces a rotating magnetic flux in the air gap, to generate the motor torque. The axial force is controlled by changing the amplitude of the rotating flux. Both permanent-magnet motor and induction motor versions were analyzed theoretically and tested experimentally. The results demonstrated the capability of providing both the functions of a motor and a magnetic bearing