Yukinori Inoue

Performance Evaluation of a High-Power-Density PMASynRM With Ferrite Magnets

Although motors that use rare-earth permanent magnets (PMs) typically exhibit high performance, high costs and concerns about the stability of raw material supplies are leading to their decreased production. However, the performance of such motors is not easily matched without the use of rare-earth PMs. This paper proposes and examines a PM-assisted synchronous reluctance motor with ferrite magnets that has the same power density as rare-earth PM synchronous motors. A suitable rotor structure for high torque and high power is discussed with respect to the demagnetization of ferrite magnets and the mechanical strength.

Experimental Evaluation of a Rare-Earth-Free PMASynRM With Ferrite Magnets for Automotive Applications

Permanent-magnet (PM) synchronous motor (PMSM) with rare-earth PMs is most popular for automotive applications because of its excellent performance such as high power density, high torque density, and high efficiency. However, the rare-earth PMs have problems such as high cost and limited supply of rare-earth material. Therefore, the electric motors with less or no rare-earth PMs are required in electric vehicle (EV) and hybrid electric vehicle (HEV) applications. This paper proposes and examines a PM-assisted synchronous reluctance motor (PMASynRM) with ferrite magnets that has competitive power density and efficiency of the rare-earth PMSM employed in HEV. The PMASynRM for automotive applications is designed taking into account the irreversible demagnetization of ferrite magnets and the mechanical strength. The prototype PMASynRM has been manufactured, and several performances such as torque, output power, losses, and efficiency are evaluated. Furthermore, the performances of the high-power PMASynRM are estimated based on the experimental results of the prototype PMASynRM, and the possibility of the application of the proposed PMASynRM to EV and HEV is discussed.

Comparative Study of PMSM Drive Systems Based on Current Control and Direct Torque Control in Flux-Weakening Control Region

This paper examines the control performance of permanent magnet synchronous motor (PMSM) drive systems based on current control and direct torque control (DTC) when flux-weakening control is applied. The control law in the M-T frame, which is used in the DTC, requires only armature resistance, whereas the control law in the d-q frame, which is used in current control, requires many motor parameters for flux-weakening control. The experimental results clarify the influence of parameter variation on the control characteristics of flux-weakening and torque limiting. The DTC-based motor drive system combined with the control laws in the M-T frame has several advantages, including insensitivity to parameter variation, simplicity of calculation, and stable control.

Performance Improvement of Sensorless IPMSM Drives in a Low-Speed Region Using Online Parameter Identification

This paper describes an approach in improving the performance of the position sensorless control of an interior permanent-magnet synchronous motor using parameter identification. The model-based sensorless method requires accurate motor parameters. At low speed, the resistance variation degrades the accuracy of position estimation. The identified parameter is used in the sensorless drive system to improve the accuracy of position estimation. In this paper, the resistance is identified online, but the offline identified value of the q-axis inductance is used. The experimental results reveal the effectiveness of applying parameter identification to the sensorless drive system.

Effectiveness of Voltage Error Compensation and Parameter Identification for Model-Based Sensorless Control of IPMSM

A sensorless-control technique for improving the performance of interior permanent-magnet synchronous-motor control such as the operating speed range and position estimation accuracy is proposed herein. The method presented is based on the estimation of an extended electromotive force in a rotating reference frame. The difference between the reference voltage and the actual voltage of the inverter is modeled and compensated for in order to improve the accuracy and the stability of the sensorless drive system. Moreover, an online parameter-identification technique is applied in order to improve the accuracy of position estimation. The effects of the proposed scheme are evaluated by the experimental results.

Control Method Suitable for Direct-Torque-Control-Based Motor Drive System Satisfying Voltage and Current Limitations

This paper proposes a control method suitable for limited armature voltage and current in a permanent-magnet synchronous motor drive system based on direct torque control (DTC). First, this paper proposes torque-limiting and flux-weakening controls that are suitable for a DTC-based motor drive system. The proposed method utilizes a mathematical model in a rotating reference frame synchronized to the stator flux linkage. Second, this paper proposes an antiwindup scheme for the torque controller of the DTC system. Windup of the controller degrades the performances of torque-limiting (current-limiting) control and of torque control. Applying the antiwindup results improves the performance of the proposed torque-limiting method in the transient state. This paper presents a DTC-based drive system combined with a speed controller. The proposed system can achieve stable control, and its effectiveness is confirmed experimentally.

A Novel Control Scheme for Maximum Power Operation of Synchronous Reluctance Motors Including Maximum Torque Per Flux Control

This paper proposes a novel control scheme for maximum power operation of synchronous reluctance motors. The proposed scheme consists of a combination of maximum torque per ampere control, maximum torque per flux control, flux-weakening control and torque limiting. The first three control methods are based on a mathematical model in a rotating reference frame that is synchronized with the stator flux-linkage. The final method utilizes a reactive torque calculated as the inner product of the flux and current vectors. The proposed control scheme is suitable for direct torque control or flux-oriented control. In this paper, the scheme is applied to a direct-torque-control-based motor drive system. The validity of the control scheme is verified by simulation and experimental results.

Examination and Linearization of Torque Control System for Direct Torque Controlled IPMSM

This paper examines the torque response based on direct torque control (DTC) for an interior permanent magnet synchronous motor. DTC with a PI controller for torque control is used in this paper. The relationship between the gains of the PI controller and the torque response is derived based on the transfer function of the torque control loop. In addition, this paper discusses the influence of the nonlinearity of the torque control loop on the torque response. It also proposes a linearization method for the torque control loop based on gain scheduling, and improvement of torque response is achieved. The effectiveness of the proposed method is verified by both simulation and experimental results.

Control method for direct torque controlled PMSG in wind power generation system

This paper proposes a generator control method for a variable-speed wind power generation system using an interior permanent magnet synchronous generator controlled by a direct torque control scheme. The proposed system has neither a wind speed sensor nor a generator position sensor, and is expected to have cost and reliability advantages for small power generation systems. It also offers several advantages over conventional current control systems: (1) ease of maximum power point tracking; (2) ease of flux-weakening control in high speed winds; (3) a novel method of torque limiting, which makes it easy to maintain the armature current at the limiting value. The experimental results demonstrate the effectiveness of the proposed system including its performance at the cut-in wind speed, and also show the influence of parameter variation.

Performance of PMASynRM With Ferrite Magnets for EV/HEV Applications Considering Productivity

Although motors that use rare-earth permanent magnets typically exhibit high performance, their cost is high, and there are concerns about the stability of the raw material supply. This paper proposes a permanent-magnet-assisted synchronous reluctance motor (PMASynRM) with a ferrite magnet that does not use rare-earth materials considering productivity. The performance of the proposed PMASynRM is evaluated based on the finite-element method and an experiment using a prototype machine. The analysis results reveal that the proposed PMASynRM has the same power density and an equivalent efficiency as rare-earth permanent-magnet synchronous motors for hybrid electric vehicles (2003 Toyota Prius). Furthermore, some experimental results are presented in order to validate the analytical results. As a result, the proposed PMASynRM was found to achieve high-power-density and high-efficiency performance.