Model Predictive Based Direct Torque Control for Induction Motor Drives by Sole-Evaluation of Two Parameter Independence Duty Ratios for Each Voltage Vector

Abstract

Abstract Due to importance of duty cycle based model predictive torque control (MPTC), it has been accepted as an effective and common alternative control strategy for industry. Since its major drawback is great dependency on duty ratio parameter, the robustness and the complexity of control system has been respectively decreased and increased. A duty-ratio set considering limited members can be replaced with continuous and dependent parameters form duty cycle relationship. Hence, this paper proposes a new and applicable discrete duty cycle control strategy to reduce both the torque and flux ripples appeared in MPTC method. In the proposed method, after preselecting around half of all admissible voltage vectors based on the torque sign or speed variation and the stator flux position, two duty ratios have just been selected for the preselected active voltage vectors. These two duty ratios are achieved based on the equivalent voltage concept with independent motor parameter. Then, the model predictive control method is employed to select the optimum active voltage vector and its relevant duty ratio among the reduced feasible voltage vectors which reduces both the flux and torque ripples, especially in low speed ranges. The simulation results have confirmed the performance of the proposed method in order to reduce the torque and flux ripples, and the experimental results have accordingly validated its performance. Since the number of voltage vectors and duty ratios is significantly decreased, the execution time of the proposed method is further reduced, and virtually worked with a constant switching frequency for all speed ranges.