scholarly journals Comparison of Hysteresis Based PWM Schemes ΔΣ-PWM and Direct Torque Control

2021 ◽  
Vol 11 (5) ◽  
pp. 2293
Author(s):  
Kevin Klarmann ◽  
Malte Thielmann ◽  
Walter Schumacher
Keyword(s):  
Direct Torque Control ◽  
Simulation Models ◽  
Torque Ripple ◽  
Design Criterion ◽  
Torque Control ◽  
Switching Frequency ◽  
Instantaneous Switching ◽  
Lower Variation ◽  
Instantaneous Values ◽  
Equal Maximum

This paper presents the differences and similarities of ΔΣ-PWM as a hysteresis-based PWM scheme with direct torque control (DTC) using simulation models. The variable switching frequency caused by the hysteresis element is examined with regard to its instantaneous values. The comparison is based on an equal maximum switching frequency as a design criterion. With this first assumption, the variation of the instantaneous switching frequency is higher when using DTC because of the temporary prioritization of one inverter leg. Besides the lower variation, ΔΣ-PWM shows a higher average switching frequency. Because the switching frequency is related to the torque ripple, the usage of ΔΣ-PWM results in a smaller torque ripple. Due to the dependence of torque ripple on switching frequency, a second comparison is carried out based on the same average switching frequency. In this comparison the ΔΣ-PWM shows higher torque ripple than DTC.

Study on speed sensorless system of permanent magnet synchronous motor based on improved direct torque control

2021 ◽  
pp. 014233122110629
Author(s):  
Xiaoxin Hou ◽  
Mingqian Wang ◽  
Guodong You ◽  
Jinming Pan ◽  
Xiating Xu ◽  
...  
Keyword(s):  
Control System ◽  
Permanent Magnet ◽  
Permanent Magnet Synchronous Motor ◽  
Direct Torque Control ◽  
Torque Ripple ◽  
Synchronous Motor ◽  
Torque Control ◽  
Switching Frequency ◽  
Speed Sensorless ◽  
Stator Resistance

The traditional direct torque control system of permanent magnet synchronous motor has many problems, such as large torque ripple and variable switching frequency. In order to improve the dynamic and static performance of the control system, a new torque control idea and speed sensorless control scheme are proposed in this paper. First, by deriving the equation of torque change rate, an improved torque controller is designed to replace the torque hysteresis controller of the traditional direct torque control. The improved direct torque control strategy can significantly reduce the torque ripple and keep the switching frequency constant. Then, based on the improved direct torque control and considering the sensitivity of the stator resistance to temperature change, a speed estimator based on the model reference adaptive method is designed. This method realizes the stator resistance on-line identification and further improves the control precision of the system. The performance of the traditional direct torque control and the improved direct torque control are compared by simulation and experiment under different operating conditions. The simulation and experimental results are presented to support the validity and effectiveness of the proposed method.

Constant Switching Frequency and Torque Ripple Minimization of DTC of Induction Motor Drives with Three-level NPC Inverter

2017 ◽  
Vol 8 (3) ◽  
pp. 1035
Author(s):  
Huzainirah Ismail ◽  
Fazlli Patkar ◽  
Auzani Jidin ◽  
Aiman Zakwan Jidin ◽  
Noor Azida Noor Azlan ◽  
...  
Keyword(s):  
Induction Motor ◽  
High Performance ◽  
Direct Torque Control ◽  
Torque Ripple ◽  
Motor Drives ◽  
Torque Control ◽  
Switching Frequency ◽  
Ac Motor ◽  
Hysteresis Controller ◽  
Selection Of

<p>Direct Torque Control (DTC) is widely applied for ac motor drives as it offers high performance torque control with a simple control strategy. However, conventional DTC poses some disadvantages especially in term of variable switching frequency and large torque ripple due to the utilization of torque hysteresis controller. Other than that, performance of conventional DTC fed by two-level inverter is also restricted by the limited numbers of voltage vectors which lead to inappropriate selection of voltage vectors for different speed operations. This research aims to propose a Constant Switching Frequency (CSF) torque controller for DTC of induction motor (IM) fed by three-level Neutral-Point Clamped (NPC) inverter. The proposed torque controller utilizes PI controller which apply different gain for different speed operation. Besides, the utilization of NPC inverter provides greater number of voltage vectors which allow appropriate selection of voltage vectors for different operating condition. Using the proposed method, the improvement of DTC drives in term of producing a constant switching operation and minimizing torque ripple are achieved and validated via experimental results.</p>

scholarly journals Minimization of Torque Ripple in DTC of Induction Motor Using Fuzzy Mode Duty Cycle Controller

2011 ◽  
Vol 7 (1) ◽  
pp. 42-49
Author(s):  
Turki Abdalla ◽  
Haroution Hairik ◽  
Adel Dakhil
Keyword(s):  
Induction Motor ◽  
Duty Cycle ◽  
Direct Torque Control ◽  
Torque Ripple ◽  
Operating Conditions ◽  
Torque Control ◽  
Voltage Source ◽  
Ratio Method ◽  
Duty Ratio ◽  
Switching Frequency

Among all control methods for induction motor drives, Direct Torque Control (DTC) seems to be particularly interesting being independent of machine rotor parameters and requiring no speed or position sensors. The DTC scheme is characterized by the absence of PI regulators, coordinate transformations, current regulators and PWM signals generators. In spite of its simplicity, DTC allows a good torque control in steady state and transient operating conditions to be obtained. However, the presence of hysterics controllers for flux and torque could determine torque and current ripple and variable switching frequency operation for the voltage source inverter. This paper is aimed to analyze DTC principles, and the problems related to its implementation, especially the torque ripple and the possible improvements to reduce this torque ripple by using a proposed fuzzy based duty cycle controller. The effectiveness of the duty ratio method was verified by simulation using Matlab/Simulink software package. The results are compared with that of the traditional DTC models.

Improved Torque Control Performance in Direct Torque Control using Optimal Switching Vectors

2015 ◽  
Vol 5 (3) ◽  
pp. 441 ◽  
Author(s):  
Muhd Zharif Rifqi Zuber Ahmadi ◽  
Auzani Jidin ◽  
Maaspaliza Azri ◽  
Khairi Rahim ◽  
Tole Sutikno
Keyword(s):  
Induction Motor ◽  
Direct Torque Control ◽  
Induction Machine ◽  
Torque Ripple ◽  
Torque Control ◽  
Multilevel Inverter ◽  
Switching Frequency ◽  
Optimal Switching ◽  
Steady State Condition ◽  
Selection Of

This paper presents the significant improvement of Direct Torque Control (DTC) of 3-phases induction machine using a Cascaded H-Bidge Multilevel Inverter (CHMI). The largest torque ripple and variable switching frequency are known as the major problem founded in DTC of induction motor. As a result, it can diminish the performance induction motor control. Therefore, the conventional 2-level inverter has been replaced with CHMI the in order to increase the performance of the motor either in dynamic or steady-state condition. By using the multilevel inverter, it can produce a more selection of the voltage vectors. Besides that, it can minimize the torque ripple output as well as increase the efficiency by reducing the switching frequency of the inverter. The simulation model of the proposed method has been developed and tested by using Matlab software. Its improvements were also verified via experimental results.

A Novel Optimal PI Parameter Tuning Strategy to Improve Constant Switching Performance of Direct Torque Control

2016 ◽  
Vol 7 (2) ◽  
pp. 422
Author(s):  
Sundram Ramahlingam ◽  
Auzani Jidin ◽  
Tole Sutikno
Keyword(s):  
Control Structure ◽  
Direct Torque Control ◽  
Parameter Tuning ◽  
Torque Ripple ◽  
Torque Control ◽  
Switching Frequency ◽  
Switching Performance ◽  
Output Torque ◽  
Stator Flux ◽  
Tuning Strategy

<p>This paper presents a novel method of optimal Propotional-Intergral (PI) controller’s parameter tuning strategy in-order to improve the Constant Switching Performance of 3-phase DTC shceme. The Direct Torque Control (DTC) sheme is acknowledged to provide fast decoupled control over the torque output and stator flux via a simple control structure. However, DTC sheme has two major downsides, which are the inconsistent inverter switching frequency and high torque output ripple. The main reason that contributes to these tribulations is the usage of hysteresis comparators in order to control the output torque. The realization of PI based controller method as replacement of hyterisis controller in DTC system able to provide significant solutions to over come the fall back while retaining the simple control structure of conventional DTC. The combination usage of higher sampling controller DS1004 and also 3-level CHMI in this system can further minimize the output torque ripple by providing higher resolution with lower digital error and greater number of vectors. This paper presents detail explanation and calculation of optimal PI parameter tuning strategy consecutively to enhance the performance of 3-level DTC system. In order to verify the feasibility of the proposed method experimentation, the proposed method is compared with convention DTC system via simulation and experiment results.</p>

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