Long-stator Linear Synchronous Motor Research Articles

Adaptive-SMO-Based Traction Force Fluctuation Suppression Strategy Considering Suspension System for High-Speed Maglev Train

The excitation pole of the long stator linear synchronous motor (LSLSM) used to drive the high-speed maglev train is also used as the suspension electro-magnet, which makes the adjustment of the suspension system affect the excitation flux linkage of the motor when the train is running at high speed, resulting in significant non-periodic traction force fluctuations. This paper proposes a traction force fluctuation suppression strategy based on the flux linkage observation. First, based on the mathematical model of the LSLSM in double feed (DF) mode, the voltage equation based on the new extended back-EMF (NEEMF) is derived, which is less sensitive to the changes of parameters, load current, and speed, so that the flux linkage can be estimated more accurately. Then, to meet the high dynamic requirements of flux linkage observation at high speed, a sliding mode flux linkage observer (SMFO) is designed and a design method of the adaptive sliding mode gain is proposed to achieve fast convergence of the system. Finally, the stator reference current required to suppress the traction force fluctuation is calculated. Hardware-in-the-loop (HIL) expe-riments verify the effectiveness of the strategy.

Periodic Traction Force Fluctuations Suppression Strategy of Maglev Train Based on Flux Linkage Observation and Harmonic Current Injection

To suppress the periodic traction force fluctuations of maglev train caused by the current harmonics and the excitation flux linkage harmonics of long stator linear synchronous motor (LSLSM), a strategy based on flux linkage observation and harmonic current injection is proposed in this paper. First, the mathematical models of the LSLSM in single feed (SF) and double feed (DF) modes are established and simplified. Then, considering the characteristics of variable frequency and phase lag of the LSLSM, an improved discrete resonant controller (RSC) with pole correction and whole frequency domain phase compensation is designed to suppress the traction force fluctuation caused by current harmonics. To suppress the traction force fluctuations caused by the flux linkage harmonics, a sliding mode flux linkage observer (SMFO) is designed and combined with an adaptive notch filter (ANF) to estimate specific flux linkage harmonics in real-time. By analyzing the flux linkage component in the traction force equation, appropriate harmonic currents are injected and tracked by the RSC. Hardware-in-the-loop (HIL) experiments verify the effectiveness of the proposed strategy.

Quasi-Synchronous Operation Principle of a Variable Air-Gap Doubly Fed Linear Motor for High-Speed Maglev Application

Compared to a long-stator linear synchronous motor (LLSM), a long-stator doubly-fed linear motor (DFLM) exhibits two distinct advantages for high-speed maglev application: 1) It has two additional degrees of freedom with both the frequency and the phase angle of the mover to improve its control accuracy and dynamic responses; 2) It can use the slip power to feed the mover contactlessly and directly. In order to achieve the propulsion, the levitation, and the contactless power transfer through the common air-gap magnetic field, the “quasi-synchronous operation (QSO)” principle of the DFLM is proposed for high-speed maglev train. Based on the DFLM modeling and distinctive constraint analysis for high-speed maglev application, the performance evaluation of the DFLM is further investigated. To validate the feasibility of the DFLM application for high-speed maglev train, a unit DFLM prototype is designed and tested, and the corresponding simulation studies of the QSO control structure are provided with the comparison to the LLSM system.

Improved Sliding Mode Traction Control Combined Sliding Mode Disturbance Observer Strategy for High-Speed Maglev Train

To improve the robustness and dynamic tracking performance of the stator current control for the long stator linear synchronous motor (LSLSM) used in high-speed maglev train traction system, a composite current control strategy combining a sliding mode current controller (SMCC) and a sliding mode disturbance observer (SMDO) is proposed in this article. First, the LSLSM mathematical model in double feed mode is optimized. Then, an SMCC is designed based on the model. An improved stability criterion is proposed and the SMCC switching gain is obtained quantitatively to meet the current following speed required for the stator changeover process. As disturbance factors, parameter perturbation of the LSLSM and the stator changeover will bring about transient current fluctuations and chattering. Therefore, an SMDO is designed to estimate the disturbances and perform feed-forward compensation for the SMCC, thereby improving the robustness and suppressing the current chattering. Finally, the hardware-in-the-loop experiments verify the effectiveness of this strategy and compare it with the traditional current control strategy.

Performance Simulation of Long-Stator Linear Synchronous Motor for High-Speed Maglev Train under Three-Phase Short-Circuit Fault

The high-speed Maglev train is driven by long-stator linear synchronous motors (LLSM). During the long-time outdoor operation, the insulation material of the armature winding may be damaged, either due to aging or the movement of the windings. This may result in the three-phase short-circuit fault, which affects the traction performance and the operation of the train. In this paper, a simulation model of the high-speed Maglev train traction system with a three-phase short-circuit fault LLSM is established, including the converters at two ends, feeder cables, segmented LLSM and traction control system. The system adopts a double-end power supply mode. The model divides the fault segment LLSM into two parts. One part is connected to the converter, which is equivalent to a normal operating segment with shortened long-stator. The other part is equivalent to a three-phase short-circuit linear generator. Based on this model, the influence of running speed and fault segment length on the traction performance of the train is simulated. In addition, the stator current, acceleration and traction force of the Maglev train during fault segment are investigated in the acceleration phase, deceleration phase and constant speed phase, respectively. The results can provide a reference for three-phase short-circuit fault diagnosis.

Modeling and Simulation of Traction Power Supply System for High-Speed Maglev Train

The electromagnetic suspension high-speed maglev train system uses long-stator linear synchronous motors (LLSMs) as levitation and traction mechanisms. In this paper, the modeling and simulation of the traction power supply system for the maglev train are performed. The simulation models include transformers, converters, variable-length cables and LLSMs of both two sides and two ends; meanwhile, the corresponding control and segmented power supply strategies, including the two-step method and three-step method, are implemented. Based on the system model, the operational performance of the high-speed maglev power supply control system is verified, and the fault performances under open circuit and short circuit are also analyzed. The whole simulation modeling and results have important reference significance for the research of high-speed maglev technology.

Improved EL Model of Long Stator Linear Synchronous Motor Via Analytical Magnetic Coenergy Reconstruction Method

Electromagnetic-suspension (EMS)-type maglev, based on long stator linear synchronous motor (LSLSM), suffers from the flux linkage and thrust ripple. This is due to the non-sinusoidal airgap magnetic field distribution caused by the slot effect and end effect. In this article, it is intended to address this issue by establishing a nonlinear mathematical model of LSLSM for real-time simulation and controller design, considering the spatial harmonics and core saturation. The Euler-Lagrange (EL) model is improved by means of coenergy and then applied to obtain the general equations of LSLSM. At first, the variation in coenergy in LSLSM regarding the mover position and stator current are analyzed, in the presence of spatial harmonics and core saturation. Afterward, an analytical model of coenergy is constructed by two Fourier basis vectors of mover position and torque angle, and a coefficient matrix polynomial of stator current magnitude. Then, a new model of LSLSM is derived based on the coenergy model and EL method. The parameters of the model can be obtained from the numerical data of coenergy in all operation ranges via finite-element analysis (FEA). Finally, the new model of LSLSM and its propulsion system are integrated in MATLAB/Simulink setup. The simulation results show that the improved EL model can achieve satisfactory accuracy compared with the FEA results well, whereas the computational efficiency is improved largely.

Method to Control Multiple Segmented LLSM without Position Encoder

<span lang="EN-GB">In recent years long stator linear synchronous motors (LLSM) started to replace the typical rotating to linear converters like belts, chains, screw systems, pulleys, disks and so on. With LLSM a lot of drawbacks in the machine concepts and design can be prevented. For long tracks, reducing reactive power and individual control of numerous moveable units, the track is segmented in several fed stator units. Because of the LLSM construction an operation with a physical position encoder is not desirable. For that reason position observers should be used instead. In this paper a method to control the multiple segmented LLSM without position encoder is proposed. The special behaviour during entrance and exit of one moveable unit in an active stator segment is described and the control concept via a master slave relationship is proposed. Experimental results are presented to demonstrate the performance and feasibility of the proposed method.</span>

A Position Estimator Using Kalman Filter With a Data Rejection Filter for a Long-Stator Linear Synchronous Motor of Maglev

As a maglev levitates with a small air gap and runs very fast, securing the levitation system's stability is crucial. Thus, the high-performance decoupling control between the propulsion control system and the levitation system is of critical importance. The study described in this paper focuses on a high-performance position estimator that minimizes the dynamic coupling between the levitation system and propulsion system in a maglev's propulsion control system using a long-stator linear synchronous motor. To that end, a position estimator using a Kalman filter was designed. Then the stability of the designed filter and its characteristics and problems that result from the change in the measurement covariance value were identified through a stability analysis of the Kalman filter. Moreover, in an attempt to improve it, a Kalman filter with a data rejection filter was proposed. Afterward, to verify the performance of the proposed position estimator, a maglev train model was fabricated and for each Kalman filter measurement covariance value, the dynamic coupling between the propulsion control system and the levitation system was identified through the test. For the Kalman filter using a data rejection filter, it was confirmed that the propulsion control system could minimize the influence on the levitation system when an inaccurate position of the vehicle is renewed.

A special excitation system for analysis of coupling characteristics of thrust and levitation force of maglev train

Background: In the maglev train propelled by long stator linear synchronous motor (LSLSM), the thrust characteristics are one of important points to evaluate the performance of the system. However, coupling effect exists between the propulsion and levitation system. Therefore, the interference from the levitation system must be considered when the propulsion system is designed.
 Aim: The article focus on the analysis of coupling characteristics of thrust and levitation force of maglev train, and a special excitation system is designed for the study.
 Methods: In order to study the thrust performance under the fluctuating air gap field under laboratory conditions, a rotating synchronous motor has been designed to imitate the long stator linear synchronous motor applied in high speed maglev train. And a special excitation system is designed for the rotating synchronous motor, which can simulate the fluctuation of the exciting current during the actual operation of maglev train. The air gap of the rotating synchronous motor is kept as constant, and the fluctuating excitation current is added to the excitation winding of the rotating synchronous motor, thus the simulation of air gap magnetic field variation is achieved.
 Results: The special excitation system of the experimental motor is introduced in detail.
 Conclusion: The relationship between thrust and levitation force of long stator linear synchronous motor (LSLSM) in maglev train is strong coupling, non-linear, and dynamic. Complete decoupling of thrust and levitation force is not easy to be achieved. The experimental platform has been built to study the coupling characteristics of thrust and levitation force of maglev train.

A method of thrust ripple suppression for long stator linear synchronous motor

With the advantages of high speed, low noise and high efficiency, the electromagnetic suspension (EMS) type maglev train has a good prospect in railway transportation. It is based on the long stator linear synchronous motor (LSLSM). However, due to cogging effect, end effect and the harmonics in the stator current and flux density distribution around the air-gap, the thrust generated by the LSLSM fluctuates. The thrust ripple brings noise, drop of control accuracy, even causes the resonance of train. In this paper, the thrust ripple produced by the cogging effect and flux linkage harmonics is analyzed. Then a method of harmonic current injection is proposed to compensate cogging force and reduce the thrust ripple, without influence the decoupling control of traction and suspension system. The injected current harmonics are controlled under multiple rotating reference frames independently. Finally, based on voltage equations of harmonics, the decoupled harmonic current controllers with harmonic voltage feedforward are designed, which improve the performance of current harmonics response and thrust ripple suppression. Simulation results on Simulink verify the effectiveness of proposed thrust ripple suppression method for LSLSM.

Hardware-in-the-loop simulation of high-speed maglev transportation five-segment propulsion system based on dSPACE

Aim: For exploring and testing the key technology of high-speed maglev transportation propulsion control system, this paper designs and establishes a hardware-in-the-loop (HIL) real-time simulation system of the high-speed maglev transportation five-segment propulsion system.
 Materials and methods of the studies: According to the route conditions and propulsion segment division of Shanghai maglev demonstration and operation line, the real-time simulation platform based on dSPACE multiprocessor systems is implemented. The simulation system can achieve the functional simulation of all the high-power related equipment in the 5-segment area, including 8 sets of high-power converter units, 2 sets of medium-power converter units, 2 sets of low-power converter units, five-segment trackside switch stations and long-stator linear synchronous motors. The mathematical models of linear motors and converters are built in MATLAB/Simulink and System Generator, after compiling, they can be downloaded and executed in Field Programmable Logic Array (FPGA). All the interfaces connecting the simulation system to the propulsion control system physical equipment use real physical components as in the field, such as analog I/O, digital I/O, optical signals and Profibus.
 Results: By using CPU+FPGA hardware configuration, the simulation steps are greatly shortened and the response speed and accuracy of real-time simulation system are improved. The simulation system can simulate multiple operating modes such as multi-segment, multi-vehicle, double-track, double-feeding, step-by-step stator section changeover, and so on. The simulation results show that the maximum speed of the simulation system can reach 500 km/h.
 Conclusion: This HIL system can provide detailed real-time on-line test and verification of high speed maglev propulsion control system.

Development of Propulsion Inverter Control System for High-Speed Maglev based on Long Stator Linear Synchronous Motor

In the case of a long-stator linear drive, unlike rotative drives for which speed or position sensors are a single unit attached to the shaft, these sensors extend along the guideway. The position signals transmitted from a maglev vehicle cannot meet the need of the real-time propulsion control in the on-ground inverter power substations. In this paper the design of the propulsion inverter control system with a position estimator for driving a long-stator synchronous motor in a high-speed maglev train is proposed. The experiments have been carried out at the 150 m long guideway at the O-song test track. To investigate the performance of the position estimator, the propulsion control system with, and without, the position estimator are compared. The result confirms that the proposed strategy can meet the dynamic property needs of the propulsion inverter control system for driving long-stator linear synchronous motors.

The Reseach on Model Predictive Control for Linear Synchronous Motor of Maglev Train

The PID controller with an advantage of simple structure and easy extension is difficult to meet the requirements of the speed control system during the parameters variation and load disturbance. This paper presents a model predictive control(MPC) strategy for motor speed control based on analysis of the mathematical model of long stator linear synchronous motor(LSLSM), which utilizes move-blocking strategy to reduce the degrees of freedom of the controller by fixing the system input to keep it constant over several time. Then a low-computation MPC controller is designed for the sake of controller implementation in practice. Finally, the simulation experiments are conducted to verify the effectiveness of the proposed controller by using Matlab. Results show that the MPC controller effectively improved the dynamic performance and steady state accuracy of the system and the low-computation MPC reduced the computational complexity with a decline in accuracy.

Design of Position Estimator for Propulsion Inverter Driving Long Stator LSM in High Speed Maglev

Abstract – In the case of long-stator linear drives, unlike rotative drives for which speed or position sensors are a single unit attached to the shaft, these sensors extend along the guideway. The position signal transmitted from maglev vehicle can ’ t meet the need of the real-time propulsion control. In this paper the position estimator for propulsion inverter driving long stator linear synchronous motor (LSLSM) in high speed maglev train is proposed. In order to get the higher resolution of the position information transmitted from vehicle, Full order state observer is proposed for position estimator. Keywords: Long Stator Linear Synchronous Motor, Position estimator, Propulsion Control, Full Order State Observer, Maglev 1. Introduction state observer is used forDuring past years, high speed maglev train based on Long Stator Linear Synchronous Motor (LS-LSM) is commercialized in Shanghai, China. The position signal of Transrapid train is key to drive propulsion inverter with LS-LSM. In MLX maglev system, it lays cross-induction coil in the middle of rail, which radiates high-frequency signals. When the train passes through the coil, it leads to the change of magnetic flux in the coil, from which we can obtain the accurate and precise position of train. Moreover, in TR maglev system the measuring method of the incremental vehicle location system INKREFA) provides the basic information for the location-related train control. The contactless determination of the absolute position of the vehicle on the guideway occurs redundantly, so that individual errors do not impose any operating restriction [1]. The detected position signals are transmitted to the propulsion inverter installed in ground by communication through radio using the RS-485 communication protocol with the cycle of 20ms and the transmission rate of 512kbps. However, the transmitted signal to propulsion control system can’t meet the need of the real-time propulsion control [2]. In this paper, the position estimator with Full order state observer is proposed in order to get the higher resolution of the position information transmitted from vehicle. Simulation results show the proposed strategy can meet the dynamic property need of propulsion control system with long state linear synchronous motor. Full order the position estimator.

Design and Characteristic Analysis of Hybrid-Type Levitation and Propulsion Device for High-Speed Maglev Vehicle

This paper deals with the design and characteristic analysis of electro-magnet/permanent-magnet (EM-PM) hybrid levitation and propulsion device for high-speed magnetically levitated (maglev) vehicle. The machine requires PMs with high coercive force in order to levitate the vehicle by only PMs, and propulsion force is supplied by long-stator linear synchronous motor (LSM). The advantages of this configuration are an increasing levitation airgap length and decreasing total weight of the vehicle, because of the zero-power levitation control. Several design considerations such as machine structure, manufacturing, and control strategy are described. Moreover, the levitation and propulsion device for high-speed maglev vehicle has been designed and analyzed usign the electromagnetic circuit and FE analysis. In order to verify the design scheme and feasibility of maglev application, 3-DOF static force test set is implemented and tested. The obtained experimental data using the static tester shows the validity of the design and analysis approaches.

Design Considerations of EM-PM Hybrid Levitation and Propulsion Device for Magnetically Levitated Vehicle

This paper deals with the design considerations of electromagnet/permanent magnet (EM-PM) hybrid levitation and propulsion device for magnetically levitated (maglev) vehicle. The machine requires PMs with high coercive force in order to levitate the vehicle by only PMs, and propulsion force is supplied by long-stator linear synchronous motor (LSM). The advantages of this configuration are an increasing levitation airgap length and decreasing total weight of the vehicle, because of the zero-power levitation control. Several design considerations such as machine structure, manufacturing, and control strategy are described. Moreover, this paper proposes the novel translator structure with segmented U-shape magnets for easy manufacturing. In order to verify the design scheme and feasibility of control strategy, dynamic test set is implemented and tested.

Speed Sensorless Control of a Long-Stator Linear Synchronous Motor Arranged in Multiple Segments

In the case of long-stator linear drives, unlike rotative drives for which speed or position sensors are a single unit attached to the shaft, these sensors extend along the carriage way, becoming a costly part of the system. Therefore, sensorless methods are of higher concern in linear motors than in rotative ones. For long carriage ways, the stator is usually divided in several independently fed segments in order to reduce the reactive power and to allow more than one vehicle to move on the same carriage way. This arrangement presents additional challenges in the implementation of sensorless methods because the position-dependent variables [as the electromotive force (EMF)] of each segment are nonperiodic signals. Moreover, the acquired speed and position information from one segment must be synchronized with the adjacent one when the mover passes over a segment transition. In this paper, a method to get a continuous estimation of the speed and position, even during the transition between segments, is proposed. This method uses an EMF observer for each active segment (i.e., where the mover is currently located, and the subsequent segment). Then, based on the addition of the observed EMF, a single speed and position observer is implemented for the mover. Using an experimental setup, validation results are attained and presented.

The computation of mechanical dynamic characteristic in EMS-Maglev system by electro-mechanical equations coupled finite element analysis

The paper describes a fast solving technique for the mechanical dynamic characteristic of electro-mechanical motional systems. Based on a sequence of finite element analysis, and a set of equivalent electrical circuit parameters extracted, the method incorporates electrical equation and vehicle's movement equation into state equations. Through test of an EMS-Maglev system, it reveals that the method gives reasonable results at very low computational costs comparing with transient finite element analysis. In electromagnetically levitated transport systems (EMS-Maglev), such as the German Transrapid, the propulsion is supplied by a Long-stator linear synchronous motor (LSM) of which the stator (armature) is fixed at all along the guide way and the moving poles with the excitation (levitation magnets) are on the vehicle. The dc exciting windings create main field and levitation forces. The armature windings of the LSM are energized by three-phase alternating voltage over a power supply section. And linear generator supplies the on-board electric power. Figure 1 shows the overall view of the EMS-Maglev transport system and the configuration of LSM longitudinal section together with the on-board linear generating system. The analysis of its mechanical dynamic characteristics is very important for the design of the configuration and the control system. Due to the complexity of the time-varying magnetic configuration, the external power supply of the LSM and the working status of linear generator, field-circuit coupled transient analysis is required. Conventionally, the time-stepping method is employed to analyze the dynamic characteristics of moving systems (1-3). Therefore, the determination of the instantaneous values requires the recurrent utilization of a FE solution. However this directly coupled FE method to analyze the dynamic characteristics is very time-consuming because the system matrix should be solved at each incremental time. In order to overcome this problem, a fast solving technique is presented for the analysis of mechanical dynamic characteristics of electromechanical motional system. Based on a

General expressions of propulsion force in EDS-MAGLEY transport systems with superconducting coils

The propulsion force produced by air-cored long-stator linear synchronous motors with superconducting coils propelling magnetically levitated vehicles with electrodynamic suspension (EDS-MAGLEV) is determined by means of an analytical three-dimensional method which takes into account different coil arrangements and the harmonic spectrum of the armature currents. The resulting analytical expressions take into account the actual coil thicknesses as well as the approximation of filiform coils and armature coils arranged both in a single layer and in two overlapped layers. The expressions have been utilized to calculate the propulsion force acting on an EDS-MAGLEV vehicle. >