Robust Direct Torque Control with Super-Twisting Sliding Mode Control for an Induction Motor Drive

Saber Krim,Soufien Gdaim,Mohamed Faouzi Mimouni

doi:10.1155/2019/7274353

Abstract

A field-programmable gate array- (FPGA-) based nonlinear Direct Torque Control (DTC) associated with Space Vector Modulation (SVM), Input-Output Feedback Linearization (IOFL), and second-order super-twisting speed controller is proposed to control an induction motor drive. First, the nonlinear IOFL is proposed to achieve a decoupled flux and torque control and the SVM technique is used to control the inverter switching frequency which reduces the torque ripples and noise. Next, to enhance the speed regulation, a super-twisting speed controller is added to an SVM-DTC-IOFL scheme. The nonlinear SVM-DTC-IOFL ensures a high dynamic response, good robustness under the external load disturbances. The Lyapunov theory is used to analyze the system stability. Then, this paper presents the interest of implementing the suggested SVM-DTC-IOFL using a Field-Programmable Gate Array (FPGA) circuit. The main interest of the FPGA-implementation is the reduction of the control loop delay, which is evaluated to a few microseconds, thanks to the parallel processing offered by the FPGA. The performances of the proposed control algorithm are investigated by digital simulation using the Xilinx system generator tool and an experimental implementation utilizing an FPGA-Virtex-5-ML507.

Highlights

The Direct Torque Control (DTC) of AC machines was proposed by Takahashi and Noguchi in 1986 [1] and by Depenbrock in 1988 [2]
In the Space Vector Modulation (SVM)-DTC the two hysteresis controllers are replaced by two Proportional Integral (PI) controllers to calculate the reference voltage vector components, which will be modulated by the SVM unit to generate the inverter switching states [6]
We propose firstly a combination between SVM-DTC, the Input-Output Feedback Linearization (IOFL), and the Super-Twisting Speed Controller (STSC) to form a new robust control scheme

Summary

Introduction

The Direct Torque Control (DTC) of AC machines was proposed by Takahashi and Noguchi in 1986 [1] and by Depenbrock in 1988 [2]. The Space Vector Modulation (SVM) strategy has been proposed and developed by several researchers to reduce the torque and the flux ripples by an operation with a constant switching frequency of the inverter. In the SVM-DTC the two hysteresis controllers are replaced by two Proportional Integral (PI) controllers to calculate the reference voltage vector components, which will be modulated by the SVM unit to generate the inverter switching states [6] This control scheme improves the DTC performances in terms of ripples. The IOFL utilizes an inverse mathematical transformation to obtain an appropriate control law to control the original nonlinear system This control strategy has been associated with the SVM-DTC in various research works to improve the AC drive performances [11, 12]

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Conclusion