Jianing Liang

A Simple Nonlinear Logical Torque Sharing Function for Low-Torque Ripple SR Drive

A novel and simple nonlinear logical torque-sharing function (TSF) for a switched reluctance motor (SRM) drive is proposed. This novel scheme using nonlinear TSF manipulates currents in two adjacent phases during commutation, so that efficiency and torque ripple in an SRM drive can be considerably improved. For constant torque generation, the switching of one-phase windings is regulated, and torque reference for the other phase stays at the previous state under the condition of a certain current limit given by the overall drive power rating. Every torque state monitored by the nonlinear logical condition determines a regulated or nonregulated torque control among two phases overlapped in commutation region, where one phase is incoming to produce the majority of torque and the outgoing current in the other phase is decreasingly controlled by the logical condition. Due to the same switching state in a nonregulated phase and the reduction of commutation period by the proposed control method, the switching number can be significantly reduced, and hence, the switching loss can be reduced. In case that one-phase regulation cannot satisfy a proper torque reference required for minimum torque ripple operation, a two-phase regulation mode is employed in the novel nonlinear TSF. In order to include magnetic nonlinearity in torque control and decrease a current tail at the end of commutation, the current of the incoming phase needs to be controlled in an increasing manner, and at the same time, the outgoing phase current tracks on an opposite direction so that torque sharing between two phases can be smoothly achieved with a minimum current crossover. The proposed control scheme is verified by some computer simulations and experimental results.

ELECTROMAGNETIC DESIGN AND ANALYSIS OF A NOVEL MAGNETIC-GEAR-INTEGRATED WIND POWER GENERATOR USING TIME-STEPPING FINITE ELEMENT METHOD

This paper presents a novel permanent-magnet (PM) machine for wind power generation. In order to achieve high power/torque density as well as get rid of the nuisances aroused by the mechanical gearbox, a coaxial magnetic gear (CMG) is engaged. Difierent from the existing integrated machine in which armature windings are deployed in the inner bore of the CMG as an individual part, stator windings are directly inserted among the slots between the ferromagnetic segments in this proposed machine. Thus, it can ofier several merits, such as simpler mechanical structure, better utilization of PM materials and lower manufacturing cost. Moreover, by artfully designing the connection of the armature windings, the electromagnetic coupling between the windings and the outer rotor PMs can be dramatically decreased, and the electromechanical energy conversion can be achieved by the fleld interaction between the inner rotor PMs and the armature windings.

Analysis of Passive Boost Power Converter for Three-Phase SR Drive

This paper presents a novel passive boost power converter and its analysis for a three-phase switched reluctance (SR) drive. The proposed simple passive circuit adds three diodes and one capacitor to the front end of a conventional asymmetric converter in order to obtain a high negative bias. Based on this passive power network, the terminal voltage of the converter side is at general dc-link voltage level in parallel mode and is up to a double dc-link voltage level in series mode. As a result, it can suppress the negative torque generation from the tail current and improve the output power. Combining a passive circuit with a three-phase asymmetric converter without phase-current overlap, the phase winding obtains the dc-link voltage in the excitation mode and the negative double dc-link voltage in the demagnetization mode. With the phase-current overlap, the dc-link voltage or the double dc-link voltage is dependent on the overlap current. The operation modes of the proposed converter are analyzed with a three-phase SR motor. The selection of the boost capacitor is considered, and a detailed analysis of current-overlap modes is presented. The compared simulation and experiments are done. The results verify the performance of the proposed converter.

OPTIMUM DESIGN FOR IMPROVING MODULATING- EFFECT OF COAXIAL MAGNETIC GEAR USING RESPONSE SURFACE METHODOLOGY AND GENETIC ALGORITHM

Coaxial magnetic gear (CMG) is a non-contact device for torque transmission and speed variation which exhibits promising potential in several industrial applications, such as electric vehicles, wind power generation and vessel propulsion. CMG works lying on the modulating-efiect aroused by the ferromagnetic segments. This paper investigates the optimum design for improving the modulating-efiect. Firstly, the operating principle and the modulating-efiect is analyzed by using 1-D fleld model, which demonstrates that the modulating- efiect is essential for the torque transmission capacity of CMGs, and the shape of the ferromagnetic segments have impact on the modulating- efiect. Secondly, the fltted model of the relationship between the maximum pull-out torque and the shape factors including radial height, outer-edge width-angle and inner-edge width-angle is built up by using surface response methodology. Moreover, FEM is engaged to evaluate its accuracy. Thirdly, the optimum shape of the ferromagnetic segment is obtained by using genetical algorithm.

Integrated Magnetic-Geared Machine With Sandwiched Armature Stator for Low-Speed Large-Torque Applications

This paper proposes a novel integrated magnetic-geared machine for low-speed large-torque applications. By embedding the armature windings into the air slots adjacent to the modulating segments, a complex component which can serve as the armature stator and the modulating stator simultaneously is achieved. Therefore, the proposed integrated machine is with simpler mechanical structure than the existing integrated machine. Since the permanent magnets on the two rotors are all effectively involved in the energy conversion process, high torque density can be achieved. Moreover, the proposed machine exhibits high power factor due to the week armature-excited field.

Classification and Analysis of Switched Reluctance Converters

This paper reviews and analyzes converters for SRM(Switched Reluctance Motor) drive. Conventional classification focuses on the number of power switches and diodes. It is easy to find the number of semiconductors and the cost by counting the number of active components, but it does not show the important characteristics of a power converter. The voltage ratings for the power switches and diodes are also difficult to identify. This paper proposes a switched reluctance (SR) converter configuration that is classified based on the commutation type and magnetic energy path. The converter has three parts: utility interface, front-end circuit, and power converter. Based on the overview on the conventional SR drive, the most important characteristic of the converter is determined by the topology of front-end in conjunction with the power converter. An SR converter has two parts: front-end and power converter. Inasmuch as the capacitive front-end is widely used for voltage source converters, this paper focuses on topologies for the front-end.

A compact integrated switched reluctance motor drive with bridgeless PFC converter

This paper presents a compact integrated switched reluctance motor(SRM) drive with bridgeless PFC converter. A novel SRM converter topology which integrated a battery charger in the SRM drive is proposed. The motor drive is rebuilt as a battery charger in the charging function. In order to obtain the balance force, the two freewheeling diodes are instead of two thyristors to inject the same magnitude current in two phases. For the driving function, the proposed SRM drive operates as an asymmetric converter. In the charging mode, all phase winding are used as inductances. The two phase windings are used to a bridgeless boost converter to satisfy the power quality requirement. The other winding is constructed be a buck-boost converter to charging the battery. The operation modes are introduced in detail. Due to ac and dc current will flow into the phase winding of SRM, the magnetic field and torque will be analyzed by FEM. Also, the charging position which is proved by mathematical method is found to keep the rotor at still and improve the charging efficiency. The control strategy of the proposed system is presented. Some simulation results are done to verify performance of proposed converter.

A Novel Targeted Magnetic Fluid Hyperthermia System Using HTS Coil Array for Tumor Treatment

This paper presents a concept of a novel targeted magnetic fluid hyperthermia system for tumor treatment. A copper solenoid is engaged to generate an oscillating high-frequency magnetic field in the tumor area to heat the injected nano-particles to kill the tumor cells. In addition, a high temperature superconductor (HTS) coil array consisting of six HTS coils deployed symmetrically in the space surrounding the patient, is used to excite a static magnetic field in the area around the tumor cells to protect the healthy tissues from thermal damage. The design considerations on the HTS coil array and the copper solenoid are introduced. Their performances are quantitatively analyzed by using 3-D finite-element method.

Analysis parking position of integrated switched reluctance motor drive system with on-board charger for EV

Analysis parking position of integrated switched reluctance motor drive with on-board charger for EV is proposed in this paper. The switched reluctance motor drive and battery charger are integrated in the EV application. A novel topology converter is proposed. The operation modes are introduced in detail. Due to the charging current is injected to phase windings, the rotor will produce the torque to rotate or rock, so the mechanical loss is increased in charging mode. The parking position can be controlled to reduce the mechanical loss. The special parking positions are found from different charging modes. And the magnetic field and torque are analyzed by FEM when the sine-wave current flows in the winding. Some simulation results are done to verify the performance of proposed converter.

Analysis of Electromagnetic Behavior in Switched Reluctance Motor For The Application of Integrated Air Conditioner On-board Charger System

In order to achieve low cost and compact design, it becomes more and more popular to integrate the circuit of the on-board charger into other power electronic circuits existing in EVs. In this paper an integrated air conditioner on-board charger system based on switched reluctance motor (SRM) was proposed, and the electromagnetic behavior occurring in the SRM when working in the charging mode was investigated. Three charging patterns, viz. single-phase charging, double-phase charging and triple-phase charging were analyzed. The specific rotor positions for which the rotor can be kept still when injecting charging currents to the armature windings were identified. The optimal design for maximizing the keeping-still capability was conducted. The power losses occurring in the SRM when working in charging mode were estimated.