A Simplified SVM-DTC Algorithm Based on Integral Derivative Sliding Mode Control for Electrical Machines

This paper presents a novel approach for achieving high-speed processing of Integral Derivative Sliding Mode Speed Controller (IDSMSC) based Space Vector Modulation Direct Torque Control (SVM-DTC) algorithm using a Field-Programmable Gate Arrays (FPGA) for controlling an Induction Motor (IM). As a first contribution in this work, the proposed IDSMSC aims to enhance the dynamic response and robustness of IM drive through the utilization of IDSMSC technique, known for its superior performance in tracking reference signals and rejecting disturbances. The second contribution consists in implementing the proposed SVM-DTC-IDSMSC algorithm on an FPGA platform. Indeed, significant improvements in processing speed and real-time responsiveness will be attained, enabling efficient execution of complex control strategies. In fact, the integration of FPGA technology ensures precise timing synchronization and parallel processing capabilities, facilitating rapid computation of control actions with minimal latency, which consequently reduce the ripples in the torque and the harmonics in the current. Through simulation studies using Xilinx System Generator toolbox under Matlab environment and performance analysis, the effectiveness and feasibility of the proposed approach are demonstrated, highlighting its potential for high-performance control applications in industrial settings.

I. Introduction

Induction motors (IM) offer numerous advantages over other types of electric motors, making them widely utilized in various industrial and commercial applications. One of the primary benefits lies in their simple and robust design, characterized by a lack of brushes or commutators, which minimizes maintenance requirements and enhances reliability. However, achieving the desired control performance for IM remains highly challenging due to fluctuating load parameters, system nonlinearities, and inaccuracies in modeling. These factors contribute to steadystate torque ripples, which pose a risk of eventual damage to the drive system. To address these challenges, Direct Torque Control (DTC) and Field-Oriented Control (FOC) are commonly utilized. An IM's DTC method has various benefits over the FOC technique, such as quick torque response, a simple control structure, low sensitivity to mismatched parameters, ease of implementation, and stable performance across a broad range of loads and speeds. It is appropriate for applications with a range of operating situations since it continues to operate well even at low speeds and in transient settings [1]. However, large torque ripples, variable switching frequency, and current harmonics are produced by traditional DTC [2]. This will have an impact on the machine's performance and worsen the power quality, particularly at low speeds. One potential option to overcome the limitations of standard DTC performance is to combine the Space Vector Modulation (SVM) technique with DTC, a combination known as SVM-DTC [3]. SVMDTC, in contrast to conventional DTC, guarantees a stable switching frequency operation while reducing ripples and harmonic distortions. Generally, speed regulation is achieved using a basic Proportional Integral (PI] controller. However, employing this controller often results in prolonged response times, sensitivity against torque disturbance and notable steady-state errors [4]. These reasons have led researchers to focus heavily on Sliding Mode Control (SMC) technique in an effort to improve speed regulation and system performance. This entails obtaining quick torque and speed responses as well as strong resistance to load torque disturbances. There has been presented a conventional SMC with a basic sliding surface [5]. Nevertheless, SMC has a recognized issue known as the chattering phenomenon in the controlled quantities. A prevalent approach to alleviate this chattering involves the utilization of a saturation function to substitute the switching function. Despite the reduction in chattering achieved through the saturation function, it introduces a steady-state error. To address the suppression of steady-state error, an Integral SMC (ISMC) approach has been devised. This entails augmenting the sliding surface with an extra integral term of the state variable. The ISMC scheme demonstrates superior control performance when contrasted with the traditional SMC technique [6]. Like the conventional SMC, when the saturation function is utilized in ISMC, determining the uncertainty bound in advance for practical applications poses considerable challenges, subsequently impacting control accuracy [7]. In [8], the authors proposed a Double ISMC (DISMC) for voltage regulation. Like the conventional SMC, when the saturation function is utilized in ISMC, determining the uncertainty bound in advance for practical applications poses considerable challenges, subsequently impacting control accuracy.