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A robust field-weakening method for direct-torque-controlled (DTC) synchronous reluctance motors is presented in this paper. The proposed algorithm achieves smooth transition between the constant torque and field-weakening regions. Maximum torque per ampere is utilized below base speed, while both the current and voltage limits of the drive system are satisfied in the field-weakening region. The proposed method is robust to the variations in the machine dq -axis inductances. This ensures the system stability during field-weakening operation, especially along the maximum torque per flux trajectory. The proposed algorithm is incorporated into the duty ratio regulation-based DTC to achieve high-performance torque and flux control in the field-weakening region. Experimental results included in this paper confirm the veracity of the proposed method. [ABSTRACT FROM AUTHOR]

The major drawbacks of classical direct torque control (DTC) are large torque ripples and variable switching frequency. Torque ripples in DTC drives can be attenuated if a three-level inverter is employed instead of a two-level inverter. Nevertheless, torque ripples can still be large if low switching frequencies are used. To alleviate these problems, a constant-switching-frequency-based three-level DTC (3L-DTC) algorithm is presented in this paper. Operating at low, constant switching frequency, the proposed algorithm is effective in reducing torque ripples under all operating conditions. Detailed analysis and design guidelines for the proposed 3L-DTC algorithm are presented. In addition, typical issues associated with the three-level inverter, such as neutral-point voltage fluctuations and smooth voltage vector switching, are addressed. Experimental results are presented to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The conventional direct torque control (DTC) features control structure simplicity, fast dynamic response, and parameter robustness. Nevertheless, it suffers from the problems of variable switching frequency and large torque ripples. This paper presents a modified DTC algorithm for interior permanent magnet synchronous motor drives with fast torque dynamics and constant switching frequency. The aforementioned problems are alleviated by adding a PI torque regulator to autonomously alter the effective duty cycle of the applied voltage vector. As a result, a constant switching frequency and also reduced torque ripples are obtained while retaining the benefits of the classical DTC. In addition, the torque dynamic response is further improved by introducing a modified switching table during transient conditions. By incorporating the modified switching table, the torque dynamic response is superior to that of the classical DTC. Simulation and experiment results included confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Direct torque control (DTC) is known to be a promising candidate for interior permanent-magnet synchronous motor drives. It provides fast dynamic response and good immunity to parameter variations. However, except for its merits, DTC also suffers from two major problems of variable switching frequency and large torque ripples. Research proposals have been published to solve these problems. Nonetheless, most of the proposals present very complex control algorithms. This paper proposes a constant switching frequency-based DTC algorithm for IPMSM drives. It consists of only one PI regulator and one triangular-wave carrier. The proposed algorithm reduces the torque ripples to a noticeable extent. In-depth analysis and design guidelines of the proposed controller are given. Simulation and experiment results are provided to verify the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper presents a robust field weakening method for the direct torque controlled (DTC) synchronous reluctance motors (RSMs). The proposed method ensures a smooth and stable transition between the maximum torque per ampere and field weakening including the maximum torque per flux regions. In addition, it is also robust to the variation in the machine dq-axes inductances in the field weakening region. The proposed algorithm is amalgamated with a duty ratio regulation based DTC to achieve high performance torque and flux control in the field weakening region. The effectiveness of the RSM drive is verified by both simulations and experiments. [ABSTRACT FROM PUBLISHER]

This paper presents an improved field weakening (FW) algorithm for synchronous-reluctance-motor drives. The proposed algorithm is robust to the variations in the machine $d$- and $q$-axis inductances. The transition between the maximum torque per ampere, current and voltage limits, and the maximum torque per flux trajectories is smooth. The proposed technique is combined with the direct-torque-control method to attain a high performance drive in the FW region. Simulation and experimental results are supplemented to verify the effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]