Torque Ripple In Steady State Research Articles

Direct torque tolerant control of five-phase permanent magnet synchronous motor based on super-twisting sliding mode tuned by ISSA

ABSTRACT This paper proposes a fault-tolerant direct torque control strategy based on an improved sparrow search algorithm (ISSA) and super-twisting sliding mode control to address torque ripple and speed response issues in direct torque control (DTC) of five-phase permanent magnet synchronous motor (PMSM). By minimising torque ripple and optimising speed response under load conditions, the traditional dual-hysteresis DTC method is improved, reducing steady-state torque ripple and overshoot in transient speed response. To handle complete rotor position sensor failures, a fault-tolerant control scheme is proposed. A super-twisting sliding mode controller is designed for the flux and torque loops of the DTC, and the improved sparrow search algorithm optimises three controller parameters for the inner and outer loops. The impact of controller complexity on the computational burden is discussed. This ensures that both speed and torque can quickly recover to normal operation after significant disturbances, effectively eliminating chattering. Simulation results demonstrate that the proposed method significantly reduces steady-state torque ripple, achieves rapid speed response, and provides fault tolerance in the event of rotor position sensor failure.

Sustainable power management in light electric vehicles with hybrid energy storage and machine learning control

This paper presents a cutting-edge Sustainable Power Management System for Light Electric Vehicles (LEVs) using a Hybrid Energy Storage Solution (HESS) integrated with Machine Learning (ML)-enhanced control. The system's central feature is its ability to harness renewable energy sources, such as Photovoltaic (PV) panels and supercapacitors, which overcome traditional battery-dependent constraints. The proposed control algorithm orchestrates power sharing among the battery, supercapacitor, and PV sources, optimizing the utilization of available renewable energy and ensuring stringent voltage regulation of the DC bus. Notably, the ML-based control ensures precise torque and speed regulation, resulting in significantly reduced torque ripple and transient response times. In practical terms, the system maintains the DC bus voltage within a mere 2.7% deviation from the nominal value under various operating conditions, a substantial improvement over existing systems. Furthermore, the supercapacitor excels at managing rapid variations in load power, while the battery adjusts smoothly to meet the demands. Simulation results confirm the system's robust performance. The HESS effectively maintains voltage stability, even under the most challenging conditions. Additionally, its torque response is exceptionally robust, with negligible steady-state torque ripple and fast transient response times. The system also handles speed reversal commands efficiently, a vital feature for real-world applications. By showcasing these capabilities, the paper lays the groundwork for a more sustainable and efficient future for LEVs, suggesting pathways for scalable and advanced electric mobility solutions.

A Simplified Voltage Vector Preselection-Based Multivector Predictive Current Control for Improved Torque Performance of PMSM Drive

Predictive Current Control (PCC) is a pioneering approach for constrained non-linear systems demanding dynamic performance in industrial and transportation applications. This article proposes a multivector PCC scheme based on a simplified voltage vector (VV) preselection for improved torque performance of PMSM drives. The prediction and optimization operations in the basic PCC (BPCC) scheme increase the computational burden of the processor. The proposed method aims to reduce the complexity of the control scheme with a VV-preselection based on an effective position estimation using the gradient concept. This helps to directly determine the optimal VV without evaluating cost-function using all the VVs. However, the application of a single VV in BPCC leads to large undulations in the torque and flux responses. This necessitates the application of multiple VVs in each control period to ensure improved torque response. To achieve this, the duration of application of the VVs is determined using the cost-function ratio of the different VVs chosen in the proposed scheme. This effectively reduces the steady-state torque ripples of the drive while retaining its dynamic response. The performance of the proposed scheme is evaluated through experimentation and compared comprehensively with BPCC and recent literature.

Transient and Steady-State Performance Improvement of IM Drives Based on Dual-Torque Model

Transient response performance and steady-state operation performance are the two most important performance indicators of a motor drive system. In order to solve these two problems, this study proposes a new induction motor (IM) model, and then designs a new simplified linearization controller method. First, the tangential force that determines the transient process of the motor is represented by electromagnetic torque, and the radial force is represented by reactive torque. Then, the dual-torque model of IM is derived, which not only accurately shows the rotating air-gap magnetic field through the amplitude and rotating angular frequency, but also visually demonstrates the physical essence of the transient process of IM. Then, this study proposes a simplified feedback linearization method without the analysis of zero dynamic. In addition, a time-scale hierarchical control system is designed to reduce the ripple caused by the coupling of different time-scale variables. The experimental results show that the steady-state torque ripple of the proposed method is 65% lower than that of RFOC, and the torque response speed is 10% higher than that of DTC.

MTPA Associated DTC Methodologies for Enhanced Performance and Energy Savings in Electric Vehicle Mobility With Induction Motor Drive

This article presents two new energy-saving control methodologies for induction motor (IM)-based electric vehicles (EVs) that exploit advantages from both direct torque control (DTC) and maximum torque per ampere (MTPA) control. While the first variant implements IM control through hysteresis controllers, the second variant employs a modulator to achieve constant switching frequency. For both variants, a flux observer is carefully designed to minimize the effects of IM parameter variations. Detailed torque ripple and power loss characteristics of IM drive controlled with the envisaged MTPA-DTC variants are also presented. The proposed techniques clearly show a reduction in current drawn by the EV system in comparison with the existing techniques. The IM drive is tested for fast acceleration and also the European Union (EU) Urban Drive Cycle to assess the advantages offered by the proposed control techniques. Advantages obtained, such as simple and fast implementation, high dynamic performance, reduced stator current, power loss leading to improved IM efficiency, and reduced steady-state torque ripple followed by energy savings obtained in the EV, are presented in the article, which can greatly benefit EV applications.

A Low-Complexity Three-Vector-Based Model Predictive Torque Control for SPMSM

In conventional model predictive torque control (MPTC), only one voltage vector (VV) is applied during a whole control period, thus causing a large torque ripple. To improve the steady-state performance, some two-vector-based control schemes have been proposed. However, the selection of the optimal VV pair is complex as well as has a large computational burden, and the improvement of performance is still limited by the direction and amplitude of the output VV. This article proposes a low-complexity three-vector-based MPTC for SPMSM drives, which can precisely determine the appropriate active voltage vectors (AVVs) with the predicted torque error. Then, a modified switching table is developed to directly select the AVVs, thus greatly reducing the complexity and computational burden of the algorithm. To obtain a better steady-state performance, a duty cycle calculation method based on torque and stator flux difference parameters is newly proposed to achieve the deadbeat control of torque and stator flux. And then, the experimental comparisons with the double-vector-based MPTC are conducted. The results show that the proposed MPTC can effectively reduce the steady-state torque ripple while maintaining a good dynamic performance as well as almost a fixed switching frequency for all speed ranges.

A Sequential Direct Torque Control Scheme for Seven-Phase Induction Machines Based on Virtual Voltage Vectors

The traditional direct torque control (DTC) strategy utilizes the largest 14 voltage vectors for a seven-phase induction machine (7PIM), which is directly extended from the three-phase counterparts. This method suffers from the issues of severe harmonic currents and torque ripple for multiphase ones. This article first puts forward the concept of virtual vectors for a 7PIM. This can efficiently eliminate the third- and fifth-order harmonic currents. However, the DTC strategy based on the virtual voltage vector has insignificant effect on reducing the torque ripple. Then, the torque ripple caused by these virtual vectors in different torque and speed conditions is investigated. Analysis shows that there are some additional degrees of freedom while choosing the applied voltage vector. A novel sequential strategy integrated with duty ratio optimization algorithm is proposed to select the optimal voltage vector that can significantly alleviate the torque ripple. Experimental results verified that the proposed method can effectively reduce the dynamic and steady-state torque ripple as well as the harmonic current.This article utilizes a 7PIM for an illustration, but it should be mentioned here that the proposed strategy is applicable for multiphase machines with any number of phases.

Model Predictive Direct Duty-Cycle Control for PMSM Drive Systems With Variable Control Set

Finite control set model predictive control has received extensive attention because of its excellent dynamic performance; however, it still needs to be studied in terms of torque ripples reduction and parameter robustness. To reduce the steady-state torque ripples and maintain the appropriate antiparameter perturbation ability, in this article, we propose a model predictive direct duty-cycle control (MPD2C) strategy based on “variable control set (VCS).” In the proposed strategy, the direct mapping relations between the electromagnetic torque, flux, and three-phase duty cycles have been established by exploring the dual relationship of vector synthesis and duty cycles. On this basis, the novel predictive model and VCS that uses the three-phase duty cycles as the key variable are constructed. Finally, the proposed strategy determines the three-phase duty cycles from VCS by employing a two-stage optimization mechanism, which means the proposed strategy can generate virtual vectors with multiple insulated gate bipolar transistor (IGBT) switching patterns. Then, the high-precision torque and flux adjustment would be achieved. The experimental results show that VCS-MPD2C has excellent static and dynamic control performance, acceptable execution efficiency, and relatively good parameter robustness.

Towards the optimal ‘slot combination’ for steady-state torque ripple minimization: an eight-pole cage rotor induction motor case study

This paper analyses the impact of the number of stator slots to rotor bars, i.e. the slot combination, in a cage rotor induction motor (IM) on its electromagnetic torque ripple during steady-state conditions. The study is focused on a conventional low voltage, eight-pole, three-phase, mains-fed IM design. To adequately evaluate the torque ripple magnitude, a ‘torque ripple factor’ is introduced and numerically calculated. To this end, IM behaviour in two common eight-pole stator slot number geometries is examined using numerical models, where, for each examined stator geometry, operation with a range of different rotor bar numbers used in practical IM designs is evaluated. For the sake of completeness and cross-validation, two different modelling approaches are used: a recently reported low-computational intensity winding function-based model and a commercial finite element analysis electromagnetic modelling software package. The paper findings deliver a detailed insight into the impact of rotor bar number, whether skewed or otherwise, on the motor steady-state torque ripple level. The presented results are indicative of the fact that the number of rotor bars only, and not the slot combination, is the dominant factor that influences the electromagnetic torque ripple in IMs with skewed rotor bars.

A New Control Method Based on DTC and MPC to Reduce Torque Ripple in SRM

This paper proposes a new control strategy to reduce torque ripple in a switched reluctance motor (SRM). The flux linkage in this paper is related to model predictive flux control (MPFC). In addition, the torque hysteresis remained in the system is similar to direct torque control (DTC) and direct instantaneous torque control (DITC). The candidate voltage vectors (VVs) are selected from the torque hysteresis and the cost function is designed for the flux linkage minimization to select the best VV from candidate VVs. The advantages, as well as the improvement prospects for these methods, are discussed in details. Performance for torque ripple in steady state and the robustness in the transient state are evaluated in this paper under the simulation and experimental results, and also the possibility and some advice for model predictive control (MPC) applied to an SRM are indicated. The experimental result for the new method is carried out on a three-phase 12/8 poles SRM with the analysis of torque ripple compared to a DTC and DITC.

Online Torque-Flux Estimation-Based Nonlinear Torque and Flux Control Scheme of IPMSM Drive for Reduced Torque Ripples

In order to have direct and better control of reducing the torque/flux ripples of interior permanent magnet synchronous motor (IPMSM), this paper presents an online torque and flux estimation-based nonlinear torque and flux control (NTFC) scheme of IPMSM drive considering motor electromagnetic developed torque and stator air-gap flux linkage as virtual state variables. For conventional nonlinear controller, the d-q-axis currents (id, iq) are considered as state variables that indirectly controls the torque/flux which may not be suitable for high-performance drives. On the other hand, conventional direct torque and flux control (DTFC) scheme suffers from significant torque ripples. The proposed work overcomes the major drawback of both the conventional nonlinear and DTFC schemes through the significant reduction in torque ripples. Stability of the proposed drive is also demonstrated through Lyapunov's stability criterion and global asymptotic stability is assured through the application of criterion supported by Barbalat's lemma. Reduced torque ripples and robustness of the proposed NTFC scheme is validated through comparative simulation and experimental results with classical nonlinear controller and DTFC-based IPMSM drive. The proposed NTFC scheme achieves the lowest possible torque ripples in steady state at different operating conditions.

Constant switching frequency model predictive control for permanent magnet linear synchronous motor

Aim: This paper proposes constant switching frequency model predictive control (CSF-MPC) for a permanent magnet linear synchronous motor (PMLSM) to improve the steady state and dynamic performance of the drive system.
 Methods: The conventional finite control set model predictive control (FCS-MPC) can be combined with a pulse width modulation (PWM) modulator due to an effective cost function optimization algorithm which is from the idea of dichotomy. In the algorithm, all the voltage vectors in the constrained vector plane are dynamically selected and calculated through iteration. The whole system including control algorithm and mathematical model of PMLSM is built and tested by simulation using MATLAB/Simulink. Besides, the control algorithm is tested in the FPGA controller through FPGA-in-the-Loop test.
 Results: With the modern digital processors or control hardware such as digital signal processors (DSPs) or field programmable gate arrays (FPGAs), the algorithm can be easily executed in less than 10-micro second. This is very proper for industrial applications. The proposed control algorithm is implemented on FPGA and tested by FPGA-in-the-Loop method. The proposed control algorithm can improve the performance of drive system greatly.
 Conclusion: The proposed CSF-MPC for PMLSM not only keeps the same dynamic transient performance as FCS-MPC but also greatly decreases the torque ripple in steady state. Furthermore, CSF-MPC is also robust to parameter variations. Simulation and FPGA-in-the-Loop results illustrate that CSF-MPC has an attractive performance for PMLSM drives.

Torque Ripple Minimization of Predictive Torque Control for PMSM With Extended Control Set

To reduce the steady-state torque ripples for permanent-magnet synchronous motor drives with predictive torque control (PTC), this paper proposes a modified PTC algorithm based on the extended control set (ECS-PTC). In the proposed algorithm, more candidate voltage vectors are extended to the control set, which forms the ECS, and then, the torque control precision could be improved and the torque ripples will be reduced. More attractive thing is that a new voltage vector synthesis method is deigned in ECS-PTC, and the corresponding predictive model and cascaded predictive algorithm are set up on the basis of this method. With the help of them, the optimal vector can be selected from ECS in a shorter control period of time, and its amplitude is also optimized at the same time to achieve high-precision control effects for torque and flux. In addition, the three-phase duty ratios of the output vector can be determined in ECS-PTC directly, without the help of space vector pulse width modulation. The experimental results show that ECS-PTC has excellent dynamic torque performance, and it also has more stable torque control performance and better execution efficiency at the same time.

Torque Ripple Reduction in Three-Level Inverter-Fed Permanent Magnet Synchronous Motor Drives by Duty-Cycle Direct Torque Control Using an Evaluation Table

In this paper, a direct torque control algorithm with novel duty cycle-based modulation is proposed for permanent magnet synchronous motor drives fed by neutral-point clamped three-level inverters. Compared with the standard DTC, the proposed algorithm can suppress steady-state torque ripples as well as ensure neutral-point potential balance and smooth vector switching. A unified torque/flux evaluation table with multiple voltage vectors and precise control levels is established and used in this method. This table can be used to evaluate the effects of duty-cycle vectors on torque and flux directly, and the elements of the table are independent of the motor parameters. Consequently, a high number of appropriate voltage vectors and their corresponding duty cycles can be selected as candidate vectors to reduce torque ripples by looking up the table. Furthermore, small vectors are incorporated into the table to ensure the neutral-point potential balance with the numerous candidate vectors. The feasibility and effectiveness of the proposed algorithm are verified by both simulations and experiments.

Active torque ripple reduction based on an analytical model of torque

The vibration caused by torque ripple may degrade the performance of drivetrain, thus the reduction of torque ripple are necessary for hybrid electrical vehicle/electrical vehicle application, while an analytical description of torque will be the basis. In this study, two-dimensional Fourier series supplemented by polynomial fitting is introduced to reconstruct the numerical solution of magnetic coenergy (MCE) from finite element analysis. An analytical torque model, which can describe torque ripple precisely at all working points, is derived from the reconstructed MCE. On the basis of the torque model, the expressions of harmonic currents used to reduce torque ripple are obtained. The proposed expression also satisfies the principle of maximum torque per ampere. Then, a feedforward torque controller based on the expression of harmonic currents is introduced. Meanwhile, a feedback torque controller based on a torque observer is developed as a comparison. The results of simulation and experiments show that both two controllers can reduce the torque ripple in steady state, but the feedforward torque controller has obviously better effects when motor speed increases. Furthermore, the feedforward torque controller is also beneficial to decline torque ripple during transient process of torque response.

Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter

The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this contribution, a six-phase double-star outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A high speed response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high-power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents was possible, improving the transient behavior of the synchronous generator. In this paper, we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage, and reduce the steady-state torque ripple. Experimental results are given for validating the models implemented for the analysis.

Torque ripple reduction of induction motor based on a hybrid method of model predictive torque control and particle swarm optimization

The quality of torque of induction motors plays an important role in many electrical drive systems. Model predictive torque control has been a good alternative to conventional direct torque control for improving the torque qualities. Recently, some researchers tried to modify the model predictive torque control with other principles such as minimize torque ripple, optimize duty cycle, in an effort to get smaller torque ripples. However, according to the reported results the torque ripples are still significant. In this article, model predictive torque control based on particle swarm optimization is proposed to modify the model predictive torque control in order to improve the control qualities, especially the steady-state torque ripples. The key idea of this approach is using particle swarm optimization to minimize the cost function. The optimal voltage vector is implemented by space vector modulation technique. In addition, the control performance of model predictive torque control–particle swarm optimization combination is also compared with that of model predictive torque control–genetic algorithm to justify the effectiveness of our method. The presented simulations prove the better torque and phase currents quality at steady state of this approach.

Modified Direct Torque Control of Induction Motor Using Three-Level Inverter

This paper study the modified direct torque control strategy of squirrel-cage induction motor using three-level inverter is presented. By using this method we can control the torque of induction motor.Look up table give the variable voltage to the inverter. It is observed that the torque ripples are much in two-level inverter as compared to three level ineverter. This is because of the high dv/dt ratio of the output voltage of inverter. These produces torque ripples in steady state. Transient and steady state are used to show the performance of machine.MATLAB/Simulink software is used. The control strategy is simulated on a 5 hp SQIM drive with three-level insulated-gate bipolar transistor (IGBT) inverter in MATLAB/Simulink software.

Direct Torque Control of Induction Motor Using Three-Level Neutral Point Clamped Inverter

The direct torque control strategy of squirrel-cage induction motor using three-level neutral point clamped inverter is presented. The strategy used for controlling the torque of induction motor includes the change in applied voltage to the squirrel-cage induction motor .The variable voltage is provided with the help of look up table to the inverter. It is observed that the torque ripples are much in three-level inverter as compared to three level ineverter. This is because of the high dv/dt ratio of the output voltage of inverter. The current ripple produces torque ripples in steady state. The performance of motor in transient state and steady state are shown. The parameters of machine are given and the controlling strategy is performed using MATLAB/Simulink software. The control strategy is simulated on a 5 hp SQIM drive with three-level insulated-gate bipolar transistor (IGBT) inverter in MATLAB/Simulink software.

Self-Tuned NFC and Adaptive Torque Hysteresis-Based DTC Scheme for IM Drive

This paper presents a simplified self-tuned Sugeno-type neuro-fuzzy controller (NFC)-based direct torque control (DTC) scheme for induction motor (IM) drive. A simple tuning algorithm is developed based on the reference and actual acceleration of the motor. The online tuning strategy adjusts the parameters of the consequent layer of the NFC in order to minimize the square of the error between the actual and the reference acceleration of the motor. In a conventional DTC scheme, the band limits of flux and torque hysteresis controllers remain fixed, and hence, the torque and flux ripples are high. In order to minimize the torque ripples of the IM, the hysteresis band limits are adjusted online for the torque hysteresis controller. Thus, the proposed NFC is used to achieve high dynamic performance of the drive, and the variable hysteresis controller is used to reduce the steady-state torque ripple. The proposed NFC-based DTC scheme is successfully implemented in real time using the DSP board DS1104 for a prototype 1-hp squirrel-cage IM. The performance of the proposed drive is tested at different operating conditions in both simulation and experiment. The proposed NFC-based DTC scheme is found superior to the conventional DTC scheme in both steady-state and transient conditions.