No abstract

The performance of electric drive propulsion systems is often degraded by the high torque and flux ripples of an electric drive. Traditional control methods, such as proportional plus integral (PI) controllers and classical sliding mode controllers (SMCs), have shown good response and reduced torque ripple, but even lower ripple content at low voltage levels is required for its effective use in electric vehicle (EV) applications. In this paper, a new direct torque control (DTC) technique with space vector pulse width modulation (SVPWM) using fractional-order sliding mode control (FOSMC) for a two-level inverter (2LI) at constant switching frequency is proposed. The effectiveness of this proposed controller is compared with a conventional proportional-integral controller and a conventional sliding mode controller (SMC). Simulink models are developed using MATLAB version R2018a to analyze the robustness of the proposed control strategy. Simulation results demonstrate the advantage of the proposed controller in reducing the torque ripples at steady state with less settling time during sudden load change conditions. The proposed control technique also demonstrates better utilization of the stator flux through flux trajectory waveforms.

Facilitating instantaneous torque and smooth speed of Electric vehicle (EV) largely relies on modulation scheme employed and type of controller used for motor drive system. The DTC-SVM (Space Vector Modulation) approach with two PI controllers has an excellent steady state and transient response. However, there is still a need to reduce stator current and torque ripples in induction motor for application in Electric vehicle. This paper presents a new approach to minimize stator current harmonics, torque ripple of an induction motor drive with appropriate gain value for torque PI controller. Good performance of the induction motor drive is achieved using a single PI controller. Both flux and torque are controlled effectively with less torque ripple. In this study, torque and current ripples are obtained at full, one-half and one-fourth of the rated speeds at rated torque value. This work analyzes the transient operation of the drive for unit step change in command torque at various rotor speeds. Space Vector Pulse Width Modulation (SVPWM) of the drive at constant switching frequency is presented. Modeling and Simulation is performed in the stationary reference frame theory. The performance is observed during steady state and transient operations. The settling time of torque responses and stator currents are obtained during transient conditions. Torque ripples are obtained during steady state. A comparison with DTC-SVM with two PI controllers for the same Torque commands is well understood. Total Harmonic Distortion (THD) in the motor input current at different reference fluxes are tabulated for classical, two PI controllers and a single PI controller. The proposed DTC-SVM scheme with single PI controller is found to be robust with good steady state and transient characteristics with less settling time and is validated with flux vector trajectories.