New advanced power conversion systems play an essential role in the extension of range and life of batteries. This paper proposes a new modular multilevel converter with embedded electrochemical cells that achieves very low cell unbalancing without traditional balancing circuits and a negligible harmonic content of the output currents. In this new topology, the cells are connected in series by means of half-bridge converters, allowing high flexibility for the discharge and recharge of the battery. The converter features a cell balancing control that operates on each individual arm of the converter to equalize the state of charge of the cells. The paper shows that the proposed control does not affect the symmetry of the three-phase voltage output, even for significantly unbalanced cells. The viability of the proposed converter for battery electric vehicles and the effectiveness of the cell balancing control are confirmed by numerical simulations and experiments on a kilowatt-size prototype.

Design and Control of Modular Multilevel Converters for Battery Electric Vehicles

Real-time (RT) simulation is a highly reliable simulation method that is mostly based on electromagnetic transient simulation of complex systems comprising many domains. It is increasingly used in power and energy systems for both academic research and industrial applications. Due to the evolution of the computing power of RT simulators in recent years, new classes of applications and expanded fields of practice could now be addressed with RT simulation. This increase in computation power implies that models can be built more accurately and the whole simulation system gets closer to reality. This Task Force paper summarizes various applications of digital RT simulation technologies in the design, analysis, and testing of power and energy systems.

Applications of Real-Time Simulation Technologies in Power and Energy Systems

In this paper, a complementary and modular linear flux-switching permanent magnet (MLFSPM) motor is investigated, in which both the magnets and armature windings are placed in the short mover, while the long stator consists of iron core only. The proposed MLFSPM motor incorporates the high power density of a linear permanent magnet synchronous motor and the simple structure of a linear induction motor. It is especially suitable for long stator applications such as urban rail transit. The objective of this paper is to build the mathematical model for the purpose of control of this motor. The simulation results by means of finite-element analysis (FEA) verified the theoretical analysis and the effectiveness of this model. Both the analytical model and the FEA results are validated by experiments based on a prototype motor.

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Modeling of a Complementary and Modular Linear Flux-Switching Permanent Magnet Motor for Urban Rail Transit Applications

Commutation torque ripple of brushless DC motor (BLDCM) is caused by the different current slew rates between switching-in phase and switching-out phase. If the slew rates were equal, commutation torque ripple could be eliminated. A simple full speed range method was presented in this paper to eliminate commutation torque ripple by dividing each pulsewidth modulation (PWM) period into three segments during commutation time. By selecting proper proportions of these three segments, the average current slew rate of switching-in phase can be kept equal with the average rate of switching-out phase in each PWM period. Because the commutation time is controllable in the presented method, commutation process which is bad for the operation of BLDCM can be finished in its highest speed. The theoretical derivation is given, the experimental results show that the commutation torque ripple can be eliminated in the minimum commutation time, and output power of BLDCM under rated load can be improved.

New Method to Eliminate Commutation Torque Ripple of Brushless DC Motor With Minimum Commutation Time

Real-time (RT) simulation is a highly reliable simulation method that is mostly based on electromagnetic transient simulation of complex systems comprising many domains. It is increasingly used in power and energy systems for both academic research and industrial applications. Due to the evolution of the computing power of RT simulators in recent years, new classes of applications and expanded elds of practice could now be addressed with RT simulation. This increase in computation power implies that models can be built more accurately and the whole simulation system gets closer to reality. This Task Force paper summarizes various applications of digital RT simulation technologies in the design, analysis, and testing of power and energy systems.

Applications of Real-Time Simulation Technologies in Power and Energy Systems IEEE PES Task Force 1 on Real-Time Simulation of Power and Energy Systems

As a direct electromagnetic driving device without adhesion, the urban transit with single-sided linear induction motor (SLIM) propulsion and wheel on rail support and guidance has many advantages, and has been a part of new type transit. In this paper, a SLIM for urban transit was designed and its characteristics were calculated with improving T-type equivalent circuit model. The specific structure problems of a SLIM such as end effects, half-filled slots for the end windings, skin effect have been taken into account in the design. The prototype has been tested, and the accuracy of the calculation is verified by experimental results.

Research on characteristics of single-sided linear induction motors for urban transit

This paper describes the operation of modular multilevel converter (MMC). A control method of adding the feed-forward current is introduced. Another strategy of removing the second harmonic current is also described in order to improve the arm currents. Simulation results based on a detailed PSIM model prove the effectiveness of the two methods. The paper presents principle of parameters selection of MMC especially the arm inductance.

The control of arm currents and the parameters for modular multilevel converters

This paper investigates factors influencing coupling ability of ironless flat winding separable transformer which could work for the contactless power supply system of the high speed maglev train. Basing on 3D finite element method (FEM), the coupling ability to geometrical sizes such as coil length and width, height of air gap and the horizontal displacement of the secondary coils is given. Effect of high frequency on the contactless power supply system is also taken into consideration. The work of this paper provides foundation for the optimized design of high coupling ability ironless flat winding separable transformer.

Study and optimized design of contactless power transformer for high speed maglev train

This paper analyzes the long-stator linear synchronous motor (LLSM) which is powered by two parallel converters. When LLSM is applied in high speed rail traffic, the long distance feeder cable has to be considered. Real time simulation is introduced to test the controller of the LLSM by using dSPACE real-time simulation platform. A real dynamic mathematical model utilizing MATLAB/SEVIULINK is built. The C code of the models is generated from RTW toolbox in MATLAB, and downloaded to the dSPACE. The models in dSPACE computer communicate with actual controller of LLSM by peripheral interface circuit such A/D, D/A, digital I/O. Real time control results show that the HTL simulation for the LLSM perform effectively.

Real-time simulation of linear synchronous motor in hardware-in-loop test system

This paper proposed a novel dual closed loop control of speed and torque method in brushless DC motor (BLDCM) drivers based on genetic algorithm. By defining speed error and torque error as optimum objective functions, using genetic algorithm, the PID parameters can be optimized. In addition, the torque ripple during commutation has been analyzed, and a variable switch conduction mode has been introduced to reduce torque ripple during commutation. The simulation results show that the torque ripple of BLDCM can be eliminated effectively during the commutation period and non-commutation period.

Yumei Du

Papers

Research on characteristics of single-sided linear induction motors for urban transit

The control of arm currents and the parameters for modular multilevel converters

Study and optimized design of contactless power transformer for high speed maglev train

Real-time simulation of linear synchronous motor in hardware-in-loop test system

Torque ripple reduction in brushless DC motor drives