High Performance Direct Torque Control of a PMSM using Fuzzy Logic and Genetic Algorithm

This paper proposes a novel direct torque control (DTC) scheme to reduce the torque and stator flux ripples for permanent-magnet synchronous motor (PMSM) drives using a relatively low sampling frequency. Unlike the conventional DTC in which the voltage vectors are determined by hysteresis controllers, the proposed DTC uses nonlinear saturation comparators and a duty ratio modulation scheme for switch selection and switching duration determination. Compared to the conventional DTC, the proposed DTC scheme significantly reduces the steady-state torque and flux ripples of PMSMs while preserving most of the intrinsic properties of the conventional DTC, e.g. fast dynamic, robust to disturbances, no coordinate transformation, etc. The effectiveness of the proposed DTC scheme is verified by simulation and experimental results on a 200W PMSM drive system.

Permanent magnet synchronous motor (PMSM) is the most widely used motor in electric vehicles (EV) due to its high power density and high efficiency. Conventional direct torque control (DTC) is developed to improve the performance of speed response of the PMSM drive but it suffers from higher torque ripples. Therefore a space vector modulation (SVM) based DTC has been developed to enhance the speed response. Due to the use of flux comparator and torque comparator conventional DTC has disadvantages such as higher torque and current ripples at steady state. To improve the performance of PMSM drive a space vector pulse width modulation is used with 3 level NPCI. To improve the performance of 2 level inverter in the PMSM drive is replaced with a neutral point clamped inverter (NPCI). Also, the switching selection strategy of SVM is modified using nearest three space vector pulse width modulation to reduce the total harmonic distortion (THD) in the inverter output. The simulation outcome proves that the SVM technique implementation in DTC for 3 level NPCI yields good performance for PMSM.KeywordsElectric vehicles (EV),voltage source inverter (VSI)Direct torque control (DTC)Neutral point clamped inverter (NPCI)Permanent magnet synchronous motor (PMSM)Space vector modulation (SVM)Total harmonic distortion (THD)

The objective of this paper is to design and study of duty ratio modulated modified Direct Torque Control drive, especially for Permanent Magnet Synchronous Motor (PMSM). Conventional Direct Torque Control (DTC) is typically associated with torque ripple and stator flux ripple. Duty ratio modulated direct torque control (DDTC) reduces torque ripple and stator flux ripple. For high performance applications the conventional DDTC is again modified to obtain comparatively less torque and flux ripple. In this paper the DDTC is associated with MTPA approach to obtain duty ratio calculation more effectively.

This article investigates an observer-based optimal direct torque control (DTC) strategy for improving the transient and steady-state performance of surface-mounted permanent magnet synchronous motor (SPMSM) drives. Unlike conventional DTC techniques, the proposed method simultaneously controls speed, torque, and flux variables by employing the optimal control theory in the stationary reference frame. This helps achieving a simple structure along with good low-speed operation as the stator flux angle need not be estimated. Further, the feedforward control terms are designed to compensate for system uncertainties. Additionally, an in-depth stability analysis is presented through the Lyapunov theory. Comparative results via a real-time prototype SPMSM test-bed with TI-TMS320F28335 DSP indicate improved performance of the proposed optimal DTC compared to conventional PI DTC, nonlinear optimal DTC, and adaptive DTC, including less computational burden, less torque and flux ripples, more robustness to parameter uncertainty, and improved transient response under very low speed/load step-changes and speed reversal.

A fuzzy direct torque control (DTC) algorithm to permanent magnet synchronous motor (PMSM) with a novel space vector modulation (SVM) defuzzification is proposed. The defuzzification unit outputs a vector contains two voltage vectors as well as the duty of each vector instead of a single vector. And more voltage vectors can be obtained. A simulation model is built up, basic DTC and conventional fuzzy DTC and proposed fuzzy DTC are carried out respectively. Torque ripple, flux ripple and current distortion are compared and analyzed. The proposed fuzzy controller makes the torque and flux ripples lower and current smoother compared with basic DTC and conventional fuzzy DTC.

In conventional direct torque controlled (DTC) permanent magnet synchronous motor drive, there is usually undesired torque and flux ripple. The existing literature have proposed some methods to reduce torque and flux ripple by optimizing the duty ratio of the active vector. However, these methods are usually complicated and parameter dependent. This paper first compares the performances of three duty determination methods in detail and then proposes a very simple but effective method to obtain the duty ratio. The novel method is superior to the existing methods in terms of simplicity and robustness. By appropriately arranging the sequence of the vectors, the commutation frequency is reduced effectively without performance degradation. To further improve the performance of system, a low-pass filter-based voltage model with compensations of amplitude and phase is employed to acquire accurate stator flux estimation. The proposed scheme is able to reduce the torque and flux ripple significantly while maintaining the simplicity and robustness of conventional DTC at the most. Simulations and presented experimental results validate the effectiveness of the proposed schemes in this paper.

A direct torque control (DTC) based on voltage space vector modulation (SVM) strategy for permanent magnet synchronous motor (PMSM) is proposed. PI controller is used in this strategy, instead of hysteresis controller and switching table in conventional direct torque control. The error between the estimated and the reference for stator flux linkage and torque will be compensated by synthesized voltage space vector accurately. The experiments verified that DTC-SVM of PMSM is capable of keeping the excellent dynamic performance, evidently reducing the torque ripple and effectively improving the steady performance

The direct torque control (DTC) is widely used in motion control of electric drives, especially for the switching table based direct torque control (ST-DTC) and the space vector modulation (SVM) based DTC (SVM-DTC). The classical ST-DTC schemes can achieve fast dynamic response but may suffer from distinct torque and flux ripples in steady-state operation. On the other hand, the classical SVM-DTC schemes have lower ripples in torque and flux, but the methods slow down dynamic response of DTC. Different from them, a novel hybrid DTC scheme is proposed for dual three-phase permanent-magnet synchronous motor (PMSM) drives in this paper, which can achieve fast dynamic response of classical ST-DTC scheme and good steady-state performance of classical SVM-DTC scheme simultaneously. The key of the proposed scheme is to implement different torque control methods under dynamic operation mode and steady-state operation mode, respectively. A switching method has been designed to guarantee smooth transition between the two operation modes. Besides, the decoupling control of torque and stator flux is maintained with the proposed control scheme, and the stator flux is controlled stably all along. By experiments on a laboratory prototype, it has been verified that the proposed scheme can achieve both good steady-state and transient performance compared to other control methods for dual three-phase PMSM drives.

Efficient feedback linearization control for an IPMSM of EVs based on improved firefly algorithm

• Modeling and design of an intelligent control system for electric vehicle applications. • Improvement of direct torque control of DFIM for electric vehicle applications through the use of fuzzy controllers. • Comparative analysis between classical DTC control and DTC based on fuzzy logic of the doubly feed induction motor for electric vehicle applications. Conventional Direct Torque Control (DTC) presents challenges such as significant torque ripples and limited adaptability to load variations. These challenges are exacerbated when applied to electric vehicles (EVs) due to changes in driving speed and the load torque that depends on road conditions. In this context, this work aims to improve the DTC of a Doubly Fed Induction Motor (DFIM) used for electric propulsion. Hysteresis comparators and the control table, responsible for the ripples in conventional DTC, have been replaced by fuzzy logic controllers. Additionally, a fuzzy logic speed controller has been designed to ensure better speed tracking across different ranges (low, medium, and high speed). Simulations performed using Matlab/Simulink allowed for a comparison of the proposed control strategy with conventional DTC. The results show a reduction of 42 % in torque ripples. Furthermore, the proposed control strategy does not show any overshoot compared to the conventional DTC strategy, which shows an overshoot of 1.5 km/h. This improves adaptability to load variations and the precision of dynamic response, optimizing the overall vehicle performance. These improvements result in smoother driving and increased overall efficiency of EVs, demonstrating the practicality and effectiveness of the fuzzy logic control strategy for electric propulsion applications.

This paper presents a sliding mode controller for an interior permanent magnet (IPM) synchronous motor, in which direct torque control (DTC) concept, variable structure control and space vector modulation (SVM) are integrated to achieve high performance. In comparison with conventional DTC, the inverter switching frequency is constant and controllable by using SVM, the torque and flux ripple are significantly reduced. The fast response and robustness merits of DTC are preserved. Position and angular speed of the rotor are obtained through an extended Kalman filter (EKF).

Direct Torque Control (DTC) of Permanent Magnet Synchronous Motor (PMSM) has quick response and simple structure, but it has the disadvantages of large torque ripples and inconstant switching frequency. An improved DTC method of PMSM based on backstepping control is proposed in this paper. For direct torque control, speed, torque and flux linkage are selected as virtual state variables and then a backstepping controller is designed to produce reference stator voltage components. Then according to those voltage components, space vector modulation (SVM) is used to produce switching states of inverters. Simulation results show that the performance of the proposed DTC system has been dramatically improved. Compared to the traditional DTC, the proposed DTC based on backstepping control could effectively decrease flux and torque ripples, make inverters have constant switching frequency. Compared to the DTC based on PI control, the backstepping DTC has fewer adjusted parameters and has good dynamic performance and good robustness.

This paper presents a new adaptive hysteresis band control approach used in direct torque control (DTC) of the induction motor (IM) drives with the switching tables for the generation of PWM signals. Constant Hysteresis Direct torque control (CHB-DTC) method used the torque and stator flux errors to generate the stator voltage reference and frequency vectors for controlling the three-phase induction motor. The CHB-DTC gives better torque transient performance but it has large steady state ripples. To reduce torque and stator current ripples in CHB-DTC controlled induction motor drives a new adaptive hysteresis band control (AHB) approach is proposed, where the hysteresis band is adapted in real time with the stator flux and torque errors variation, instead of fixed bandwidth. Both classical CHB-DTC method and the proposed adaptive hysteresis band DTC (AHB-DTC) fed three induction motor have been simulated using Matlab/Simulink. The simulation results at different operating conditions over a wide speed range demonstrate the validity, effectiveness, and feasibility of the proposed scheme. The measurements showed that torque ripples were significantly decrease with the new AHB-DTC technique and better speed response in step up or down compared to the CHB-DTC.

Direct torque control (DTC) has become a widely acceptable alternative to field-oriented control in permanent magnet synchronous motor (PMSM) drives. Deadbeat direct torque and flux control (DB-DTFC) is a significant improvement over the classical DTC. However, there are some aspects that can be improved, such as insufficiently small electromagnetic torque ripple, unsmooth dynamic response, heavy computation burden, and relatively weak robustness to motor parameters variation. To improve the operation performance, an advanced DB-DTFC strategy is proposed in this article. First, the algorithm model based on stator flux oriented coordinate system is deduced. On this basis, the basic principle of proposed DB-DTFC is presented. Second, a novel graphical analysis method is proposed to help illustrate the proposed strategy. Third, a general solution method is proposed to solve the reference stator voltage, which is a key variable for the DB-DTFC. Finally, the stability of system is analyzed. Theoretical and experimental comparisons between the proposed DB-DTFC and the conventional DB-DTFC are done. The results show that the performance in the aspects of electromagnetic torque and stator current ripples reduction, dynamic response, computation burden, and robustness to motor parameters variation are all improved in the proposed DB-DTFC.

A novel hybrid control strategy for reducing torque ripple in permanent magnet brushless direct current motors has been developed by combining the deterministic nature of direct torque control and the adaptive nature of fuzzy logic control. Direct torque control using space vector pulse width modulation has been developed. This technique ensures the near-sinusoidal nature of the stator and rotor current. The impact of commutation ripple corresponding to the sinusoidal current is reduced compared to square wave current in conventional direct torque control. Further, the fuzzy logic controller provides adaptive modulation in space vector to mitigate the torque ripple. The response of the proposed method has been analyzed in the time domain as well as in the frequency domain. Experimental results establish a significant reduction in torque ripple and minimization of high-frequency components. A comparative study with conventional direct torque control methods has also been presented.