感应励磁式无刷同步电机设计与仿真分析

文中采用了一种感应励磁方式实现径向/切向混合励磁交流发电机的无刷励磁方案,依靠定子绕组磁场在转子励磁绕组内感应出的交流电流整流来获得同步电机的电励磁电流。文中详细介绍了该电机的结构特点和工作原理,借助有限元仿真的分析,得到了电机的空载特性和外特性曲线。仿真结果分析表明：该电机集成了永磁电机效率高和电励磁电机调磁方便等优点。此外,相比于传统两级式励磁方式,该交流发电机的无刷励磁方案使得电机具有结构简单等特点。     

Analysis of synchronous machine modeling for simulation and industrial applications

This paper analyses the synchronous machine modeling by taken into account the machine parameters usually used in industry and those used in researcher’s domains. Two models are presented. The first one is developed in the (d, q) natural reference frames and the other one is referred to the (d, q) stator reference frame. To do this, two methods are proposed to compute the reduction factor of the field winding without any input from design information. It is shown that the reduction factors of the (d, q) damper windings do not influence on the terminal behavior of the machine. This means that it is possible to know the terminal behavior of the machine without knowing the real inductances and resistances of the damper windings. The accuracy of these models is validated by experimental tests.     

不同铁心模型对绕组累积效应影响的仿真对比

铁芯是变压器主磁通的传输路径,在变压器磁场相关仿真建模中铁芯模型是不可缺少的部分。采用有限元法建立片状仿实型、矩形均匀化、圆柱型三种不同铁芯模型,通过施加短路电流激励获得了不同模型下漏磁通密度、电磁力密度变化规律和分布对比。最后以实际片状仿实型铁芯模型作参考,对绕组累积效应变形量进行仿真对比,仿真结果为矩形和圆柱型铁芯的误差均在10%以内,表明在提高变压器相关仿真效率问题时,矩形和圆柱型铁芯可提供建模方法参考。     

Self-sensing for electromagnetic actuators. Part II: Position estimation

The second paper in a two part series presents the position estimation scheme for an 8-pole heteropolar active magnetic bearing (AMB). The integrated self-sensing assembly comprises a nonlinear MIMO parameter estimator together with a coupled reluctance network model (Part I), by which problems associated with magnetic cross-coupling and saturation are collectively addressed. The parameter estimator utilizes the first harmonic components of the current and voltage waveforms to determine estimates for the x and y rotor positions. Magnetic saturation is accounted for using a saturation factor, which scales the demodulated coil currents to ensure that the actuator with the lowest flux density contributes the most to the position estimate. Basic functionality and feasibility of the proposed self-sensing scheme are demonstrated via an experimentally validated transient simulation model (TSM). The TSM incorporates magnetic effects such as eddy currents, cross-coupling, and hysteresis. In the second part of this work, the static and dynamic performance of the self-sensing sensor is evaluated. The influence of magnetic cross-coupling, saturation, and duty cycle variation on the position estimate is documented. The results demonstrate the importance of including a mutual coupling term in the position estimation model in order to stably suspend the rotor. Furthermore, stability margin analyses indicate that the robustness of the magnetic bearing control is satisfactory for unrestricted long-term operation.     

Hybrid genetic algorithm for the identification of high-order synchronous machine two-axis equivalent circuits

A hybrid genetic algorithm is used to find high-order equivalent circuits (ECs) of synchronous machines using standstill frequency response (SSFR) data. The algorithm performs satisfactorily despite the great deal of local minima surrounding the optimal solution of high-order ECs. It gives circuit parameters that simultaneously fit the three independent transfer functions given by the d-axis two-port network of the synchronous machine. It is found that as the order of the EC is increased, the optimization index used in the identification procedure is enhanced in a clear fashion. This leads to a new way for determining the right number of rotor branches required to correctly reproduce the SSFR data. The q-axis network is also analyzed with the hybrid algorithm. The so-called Canay's inductances are included in this one-port network to test if the fitting properties of the q-axis EC can be improved. The SSFR data used in this work is generated by a finite element model of a turbine generator, but actual data can also be readily handled.     

An adaptive communications protocol for network computers

We study the performance of a new network communication protocol designed specifically for network computers-collections of memory-disjoint computer nodes intended to function as single machines. Staged circuit switching is intended to combine the benefits of circuit switching at low traffic loads with the benefits of message switching at heavy loads, and to serve, in addition, as the basis for communication systems that continually reconfigure the network at runtime of optimize for observed traffic patterns. Our simulation results support our favorable conjectures about the behavior of staged circuit switching. These results, and a saturation analysis, are presented.     

Analysis of the impact of space vector modulation techniques on the operation of ultrahigh speed induction machines

The paper investigates the impact of different space vector modulation (SVM) techniques on the operation of ultrahigh speed induction machines (USIMs), where the m_f frequency ratio is low owing to the necessarily high fundamental frequency f₁. Three different sampling techniques, the Regular Sampled, Naturally Sampled and the Oversampled are studied by simulation. It is found that the SVM is proned to generate DC current in the stator windings. Furthermore subharmonic flux and current components with considerable amplitudes can also be generated in USIM. In the paper it is revealed that both the DC and the subharmonic components could lead to extremely large additional losses in the USIM enhanced by its special parameters.     

Transition submatrices in regular homing experiments and identification of sequential machines of known class using direct-sum transition matrices

In connection with the measurement and control of synchronous sequential machines, Das et al. recently proposed an approach to the solution of the problems using the transition matrix representation of the machine and its higher-order forms. In the present paper, by extending the transition matrix approach of Das et al., an approach based on transition submatrix is developed to solve the regular homing problem in synchronous sequential machines. In addition, the problem of identifying a machine of a known class is also considered. Since the proposed transition submatrix approach can simplify the matrix computations, and can reduce the amount of storage required by significantly reducing both the dimension and the order of the matrix being used, it not only retains all the advantages of the approach by Das et al., but it lends itself to even easier computer implementations as well.     

Adaptive control strategy with flux reference optimization for sensorless induction motors

Avoiding mechanical (speed, torque) sensors in electric motor control entails cost reduction and reliability improvement. Furthermore, sensorless controllers (also referred to output-feedback) are useful, even in the presence of mechanical sensors, to implement fault tolerant control strategies. In this paper, we deal with the problem of output-feedback control for induction motors. The solutions proposed so far have been developed based on the assumption that the machine magnetic circuit characteristic is linear. Ignoring magnetic saturation makes it not possible to meet optimal operation conditions in the presence of wide range speed and load torque variations. Presently, an output-feedback control strategy is developed on the basis of a motor model that accounts for magnetic saturation. The control strategy includes an optimal flux reference generator, designed in order to optimize energy consumption, and an output-feedback designed using the backstepping technique to meet tight speed regulation in the presence of wide range changes in speed reference and load torque. The controller sensorless feature is achieved using an adaptive observer providing the controller with online estimates of the mechanical variables. Adaptation is resorted to cope with the system parameter uncertainty. The controller performances are theoretically analyzed and illustrated by simulation.     

State feedback tracking control for indirect field-oriented induction motor using fuzzy approach

This paper deals with the synthesis of fuzzy controller applied to the induction motor with a guaranteed model reference tracking performance. First, the Takagi-Sugeno (T-S) fuzzy model is used to approximate the nonlinear system in the synchronous d-q frame rotating with field-oriented control strategy. Then, a fuzzy state feedback controller is designed to reduce the tracking error by minimizing the disturbance level. The proposed controller is based on a T-S reference model in which the desired trajectory has been specified. The inaccessible rotor flux is estimated by a T-S fuzzy observer. The developed approach for the controller design is based on the synthesis of an augmented fuzzy model which regroups the model of induction machine, fuzzy observer, and reference model. The gains of the observer and controller are obtained by solving a set of linear matrix inequalities (LMIs). Finally, simulation and experimental results are given to show the performance of the observer-based tracking controller.     

A resilient adaptive sliding mode observer for sensorless AC salient pole machine drives based on an improved HF injection method

In high frequency (HF) injection methods, classical tracking algorithms are used to estimate the rotor position for sensorless alternating current (AC) salient pole machines. These algorithms were dependent on AC machine inductances which are characterized by their large variations. To overcome this dependency, a new approach based on using only the sign of the rotor position estimation error (instead of using rotor position estimation error) is proposed. This approach has also the advantage of removing the low-pass filter (LPF) used to separate the HF component from the rotor position information. Consequently, only the first order sliding mode observer can be employed to estimate the rotor position, as only the sign of the rotor position estimation error is known. To avoid the well known chattering phenomena of this observer, an adaptive step-by-step sliding mode observer is proposed as an alternative solution to estimate the rotor position of the machine. The stability study of the proposed observer is analyzed both in transient/steady state ranges and a procedure for gains tuning is then given. The performance of the proposed algorithm is tested on simulation and experimentally in the framework of a representative small-scale electric propulsion benchmark, used in automotive applications. Moreover, a comparison study is conducted with respect to some existing tracking algorithms in order to illustrate the well-founded of the designed algorithm.     

基于SVPWM的异步电机矢量控制系统的仿真

首先阐述了空间矢量脉宽调制技术应用于交流感应电机矢量控制系统的基本原理,在此基础上讨论了间接转子磁场定向电压注入型矢量控制系统的实现方案,基于MATLAB/SIMULINK构建了这种矢量控制系统的仿真模型并进行了深入的仿真研究.仿真结果表明了模型的正确性,并验证了该文所建立的调速系统可以实现感应电机产生转矩的电流分量和产生磁通的电流分量之间的解耦控制,使感应电机获得与他励直流电机一致的瞬态响应特性,实现了对负载扰动和参考值变化的快速响应.     

Bi-criteria optimization design of an interior permanent magnet synchronous machine for a hybrid electric vehicle application

The main focus of this study is to provide a new calculation method of power losses in electrical machine, including copper losses and iron losses at load. This calculation is applied not only for an operating point of the machine but also for thousands of operating points during a driving cycle for a hybrid electric vehicle (HEV) application. The calculation is made taking into account flux-weakening, magnetic material non-linearity and losses at-load. Therefore, we have proposed a design approach using Non-dominated Sorting Genetic Algorithm, version II (NSGA-II). This approach respects two criteria namely the minimization of average losses during the cycle and the minimization of the RMS current at the rated point. The result is represented by a Pareto curve.     

A minimum-cost network flow approach to preemptive parallel-machine scheduling

We model and solve the problems of preemptive scheduling of n independent jobs with release dates on m parallel machines with machine availability and eligibility constraints to minimize the makespan and maximum lateness as the minimum-cost network flow problem. We show that the approach can be extended to solve the corresponding scheduling problems on two uniform parallel machines.     

Induction machine speed control with flux optimization

A new speed control strategy is developed, based on a machine model that accounts for the magnetic characteristic saturation. The control strategy includes a flux reference generator, designed to meet optimal operational conditions, and a speed controller designed using nonlinear techniques. Both flux generation and speed control laws involve the machine state variables. The performances of the proposed control strategy are formally analyzed and its supremacy with respect to standard control solutions is illustrated through simulation.     

Initial position estimation strategy for a surface permanent magnet synchronous motor used in hybrid electric vehicles

A novel nonlinear model for surface permanent magnet synchronous motors (SPMSMs) is adopted to estimate the initial rotor position for hybrid electric vehicles (HEVs). Usually, the accuracy of initial rotor position estimation for SPMSMs relies on magnetic saturation. To verify the saturation effect, the transient finite element analysis (FEA) model is presented first. Hybrid injection of a static voltage vector (SVV) superimposed with a high-frequency rotating voltage is proposed. The magnetic polarity is roughly identified with the aid of the saturation evaluation function, based on which an estimation of the position is performed. During this procedure, a special demodulation is suggested to extract signals of iron core saturation and rotor position. A Simulink/MATLAB platform for SPMSMs at standstill is constituted, and the effectiveness of the proposed strategy is verified. The proposed method is also validated by experimental results of an SPMSM drive.     

Microwave frequency small‐signal equivalent circuit parameter extraction for AlInN/GaN MOSHEMT

This article presents an accurate and efficient extraction procedure for microwave frequency small‐signal equivalent circuit parameters of AlInN/GaN metal‐oxide‐semiconductor high electron mobility transistor (MOSHEMT). The parameter extraction technique is based on the combination of conventional and optimization methods using the computer‐aided modeling approach. The S‐, Y‐, and Z‐ parameters of the model are extracted from extensive dynamic AC simulation of the proposed device. From the extracted Y‐ and Z‐ parameters the pad capacitances, parasitic inductances and resistances are extracted by operating the device at low and high frequency pinch‐off condition depending upon requirement. Then, the intrinsic elements are extracted quasi analytically by de‐embedding the extrinsic parameters. S‐parameter simulation of the developed small‐signal equivalent circuit model is carried out and is compared with TCAD device simulation results to validate the model. The gradient based optimization approach is used to optimize the small‐signal parameters to minimize the error between developed SSEC model and device simulation based s‐parameters. The microwave characteristics of optimized SSEC model is carried out (f_T = 169 GHz and f_max = 182 GHz) and compared with experimental data available from literature to validate the model.     

The cascade multivariable control system of poloidal magnetic fluxes in a tokamak

This paper presents the model of Globus-M active spherical tokamak without plasma in the vacuum vessel. The tokamak passive structures are taken into account in the model. The authors develop the multivariable control system of poloidal magnetic fluxes in the tokamak vacuum vessel of the external cascade based on the internal current control cascade in the poloidal windings. The numerical simulation results of the control system in Matlab are given.     

Dynamic reduction of unbalanced magnetic force and vibration in switched reluctance motor by the parallel paths in windings

The influence of winding method counteracting unbalance forces on the rotor vibration behavior is investigated in this paper. Unbalanced magnetic force caused by rotor eccentricity may degrade the performance of motor, increasing vibration, acoustic noise, excessive wear of bearing and degree of eccentricity. This paper proposed a method to reduce the unbalanced magnetic force and vibration by introducing parallel paths in windings. The motor was simulated by using 2D transient magnetic FE analysis coupled with external circuits. Serial connection and various parallel connections of windings were modeled in the external circuit. It was found from the simulation results that the currents could be balanced in parallel paths and unbalanced magnetic forces could be reduced. Experiment results also reveal that the acceleration of stator surface is minimum with the proposed method.