The modular multilevel converter (MMC) is currently one of the power converter topologies which has attracted more research and development worldwide. Its features, such as high quality of voltages and currents, high modularity and high voltage rating, have made the MMC a very good option for several applications including high-voltage dc (HVdc) transmission, static compensators (STATCOMs), and motor drives. However, its unique features such as the large number of submodules, floating capacitor voltages, and circulating currents require a dedicated control system able to manage the terminal variables, as well as the internal variables with high dynamical performance. In this paper, a review of the research and development achieved during the last years on MMCs is shown, focusing on the challenges and proposed solutions for this power converter still faces in terms of modeling, control, reliability, power topologies, and new applications.

Modular Multilevel Converters: Recent Achievements and Challenges

This paper proposes a comprehensive framework for multiobjective design optimization of switched reluctance motors (SRMs) based on a combination of the design of experiments and particle swarm optimization (PSO) approaches. First, the definitive screening design was employed to perform sensitivity analyses to identify significant design variables without bias of interaction effects between design variables. Next, optimal third-order response surface (RS) models were constructed based on the Audze-Eglais Latin hypercube design using the selected significant design variables. The constructed optimal RS models consist of only significant regression terms, which were selected by using PSO. Then, a PSO-based multiobjective optimization coupled with the constructed RS models, instead of the finite-element analysis, was performed to generate the Pareto front with a significantly reduced computational cost. A sample SRM design with multiple optimization objectives, i.e., maximizing torque per active mass, maximizing efficiency, and minimizing torque ripple, was conducted to verify the effectiveness of the proposed optimal design framework.

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Multiobjective Optimization of Switched ReluctanceMotors Based on Design of Experiments and ParticleSwarm Optimization

In this article, an improved direct instantaneous torque control (DITC) based on adaptive terminal sliding mode control (ATSMC) is proposed to suppress torque ripple and enhance the anti-interference ability for switched reluctance motors (SRMs). The proposed speed controller used in the outer loop of DITC is based on the rate of change in load torque. The state of the system converges quickly to the equilibrium point and realizes fast output of the given torque without known disturbance upper bound. Moreover, a novel reaching law is proposed to reduce torque ripple and startup time. The stability of the adaptive terminal sliding mode motion is verified by using the Lyapunov function. The improved DITC system is implemented on a 16/10 segmented-rotor SRM. Compared with sliding mode control and terminal sliding mode control, the proposed ATSMC in the DITC system behave with better performances in aspects of the speed and torque response, antiinterference ability, robustness, and torque ripple suppression. Simulation and experimental results are given to verify the effectiveness of the improved DITC.

An Improved Direct Instantaneous Torque Control Based on Adaptive Terminal Sliding Mode for a Segmented-Rotor SRM

This paper presents a detailed literature review on switched reluctance motor (SRM) and drive systems in electric vehicle (EV) powertrains. SRMs have received increasing attention for EV applications owing to their reliable structure, fault tolerance ability and magnet free design. The main drawbacks of the SRM are torque ripple, low power density, low power factor and small extended speed range. Recent research shows that multi-stack conventional switched reluctance motors (MSCSRM) and multi-stack switched reluctance motors with a segmental rotor (MSSRM-SR) are promising alternative solutions to reduce torque ripples, increase torque density and increase power factor. Different winding configurations such as single-layer concentrated winding (SLC), single layer mutually coupled winding (SLMC), double layer concentrated winding (DLC), double layer mutually coupled winding (DLMC) and fully-pitched winding (FP) are introduced in the literature in recent years to increase average torque and to decrease torque ripples. This research analyzes winding methods and structure of the SRMs, including conventional and segmental rotors. They have been compared and assessed in detail evaluation of torque ripple reduction, torque/power density increase, noise/vibration characteristics and mechanical structure. In addition, various drive systems are fully addressed for the SRMs, including conventional drives, soft-switching drives, drives with standard inverters and drives with an integrated battery charger. In this paper, the SRM control methods are also reviewed and classified. These control methods include strategies of torque ripple reduction, fault-diagnosis, fault-tolerance techniques and sensorless control. The key contributions of this paper provide a useful basis for detailed analysis of modeling and electromechanical design, drive systems, and control techniques of the SRMs for EV applications.

/pdf/switched-reluctance-motors-and-drive-systems-for-electric-zj0y9ce1l5.pdf

Switched Reluctance Motors and Drive Systems for Electric Vehicle Powertrains: State of the Art Analysis and Future Trends

This paper presents a technical overview for fault diagnosis and fault-tolerant strategies of switched reluctance machine (SRM) systems. With the widespread utilization of electrical motors, stability and reliability become the most important considerations for safety. SRMs are famous for their great robustness, wide speed range, and high fault-tolerant capability, which are much suitable for high-speed and safety-critical applications. Although the SRM drive have some fault tolerance ability, the fault still seriously affects the system performance. The faults happening in different parts, such as converter, motor winding, sensors, and rotor, may lead to low torque, large torque ripple, overcurrent, insulation damage, and even system broken-down, without any fault-tolerant consideration. Therefore, it is important and urgent to improve the motor system reliability and robustness for SRM drives. Aiming at offering novel solutions to the faults in SRM drives, this paper begins with mathematical modeling of the SRM, and then concentrates on the state-of-art fault diagnosis and fault tolerance techniques to enhance the fault ride-through ability. Two categories, containing fault diagnosis and fault tolerance technologies are emphasized for fast faults locating and stable post-fault operation. Advanced technologies are reviewed, classified, and compared comprehensively. Besides, several fault diagnosis and tolerance schemes that have been developed by authors are presented and discussed as well. Finally, the research status and outlooks on this topic are put forward. It is our target to offer a global vision on fault-related strategies and bring out promising ideas about fault-related techniques in SRM drives.

/pdf/an-overview-of-fault-diagnosis-and-fault-tolerance-35g5khy7bx.pdf

An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems

This paper proposes a modular multilevel converter (MMC) based switched reluctance motor (SRM) drive with decentralized battery energy storage system for hybrid electric vehicle applications. In the proposed drive, a battery cell and a half-bridge converter is connected as a submodule (SM), and multiple SMs are connected together for the MMC. The modular full-bridge converter is employed to drive the motor. Flexible charging and discharging functions for each SM are obtained by controlling switches in SMs. Multiple working modes and functions are achieved. Compared to conventional and existing SRM drives, there are several advantages for the proposed topology. A lower dc-bus voltage can be flexibly achieved by selecting SM operation states, which can dramatically reduce the voltage stress on the switches. Multilevel phase voltage is obtained to improve the torque capability. Battery state-of-charge balance can be achieved by independently controlling each SM. Flexible fault-tolerance ability for battery cells is equipped. The battery can be flexibly charged under both running and standstill conditions. Furthermore, a completely modular structure is achieved by using standard half-bridge modules, which is beneficial for market mass production. Experiments carried out on a three-phase 12/8 SRM confirm the effectiveness of the proposed SRM drive.

MMC-Based SRM Drives With Decentralized Battery Energy Storage System for Hybrid Electric Vehicles

Double-stator switched reluctance motors (DSSRMs) are gaining much attention due to advantages of higher power/torque density and lower acoustic noise compared to conventional SRMs. In this paper, a novel three-phase 12/8/12-pole DSSRM design method is proposed by multiple pole arcs optimization for higher torque and lower torque ripple applications. A constrained quadrilateral is first presented to restrict the combinations of pole arcs according to motor operation conditions. Then, multiple parametric analysis processes are employed to analyze the effects of pole arcs on static torque in 3-D finite-element modeling environment. In order to select the optimal combinations of pole arcs generating higher torque, an effective torque evaluation principle is presented. Instead of the conventional 22.5° rotor position range, 15° range is adopted to calculate the average torque according to the static torque profiles, which is more effective to evaluate the torque capability. The selected torque range considers not only the excitation and demagnetization processes of phase currents but also the optimal range for torque generation. Finally, in order to achieve a lower torque ripple, the transient simulation is further carried out to identify the optimal pole arcs by comparing the torque ripple, average torque, and efficiency.

DSSRM Design With Multiple Pole Arcs Optimization for High Torque and Low Torque Ripple Applications

The present invention discloses a multi-port bi-directional switched reluctance motor driving system used for a solar power hybrid electric vehicle. The system can realize multi-port flexible operation under an electric mode and a charging mode. The system can choose connected power supplies flexibly according to light intensity and operation road conditions, so that high-performance multi-port electric operation is realized. Multi-level working mode can be realized under the condition that a generator supplies power alone and a battery pack supplies power alone, so that the output torque of amotor is effectively improved. The battery pack can recover energy via a converter to realize trickle charging in an electric process and a brake process. The battery pack can perform fast self-charging via photovoltaic panels or the generator under the condition that the vehicle is motionless, and battery pack can realize heavy-current fast charging by connecting to an alternating current powergrid directly. According to the multi-port bi-directional switched reluctance motor driving system, multi-port flexible electro-mechanical energy conversion is realized, the operation performance of the motor is improved, and the dependence on fuels, batteries and charging stations, of the hybrid electric vehicle is greatly reduced.

Multi-port bi-directional switched reluctance motor driving system used for solar power hybrid electric vehicle

The invention discloses a switch reluctance motor system based on double-bus split current sampling. On the basis of a traditional asymmetric half-bridge converter, an upper bus and a lower bus are split and connected, and two current sensors are adopted to respectively detect the current information of the upper bus and the current information of the lower bus. One bus current comprises current information of two phases, and the other bus current comprises current information of the other two phases. By combining the turn-on interval information of each phase winding, the excitation current in each phase conduction interval can be effectively obtained, and therefore current control is carried out. The excitation current of each phase winding in the turn-on interval can be detected by onlytwo current sensors, and the number of current sensors traditionally used is reduced by one half. According to the scheme, pulse injection is not needed for each phase and extra hardware equipment isnot needed. The excitation current of each phase can be obtained directly according to the double-bus sampling current and the turn-on information of each phase. The method is simple and reliable andis easy to implement.

Switch reluctance motor system based on double-bus split current sampling

This paper proposes an maximum torque per ampere (MTPA) control method based on online calculation of inductance increment for interior permanent magnet synchronous motor (IPMSM) for electric vehicles. In this method, the disturbance caused by inductance variation is extended to state variables for observation. The inductance increment is updated rollingly according to the observation value, and the inductance parameters are corrected in real time. The accurate MTPA current reference is directly calculated by using the corrected inductance parameters. Compared with the traditional virtual sinusoidal signal injection method considering the change of inductance parameters, the proposed MTPA control method reduces the use of filters and has a fast dynamic response. The proposed method is tested on a 60 kW IPMSM, and the experimental results verify its feasibility and effectiveness.

Maximum Torque Per Ampere (MTPA) Control Based on Online Calculation of Inductance Increment

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