Electrical Machines
H. Afsharirad; S. Misaghi
Abstract
Background and Objectives: Due to the high torque ripple and stator current harmonics in direct torque control using a two-level inverter, the use of multi-level inverters has become common to reduce these two factors. Among the multilevel inverters, the Neutral-point-Clamped Inverter has been given ...
Read More
Background and Objectives: Due to the high torque ripple and stator current harmonics in direct torque control using a two-level inverter, the use of multi-level inverters has become common to reduce these two factors. Among the multilevel inverters, the Neutral-point-Clamped Inverter has been given more attention in the industry due to its advantages. This inverter has 27 voltage vectors by which torque and flux are controlled. In order to reduce torque ripple and current harmonic as much as possible, methods such as space vector modulation methods or the use of multi-level inverters with higher levels have been considered. But the main drawback of these methods is the increase of complexity and cost.Methods: In this article, virtual voltage vectors are used to increase the number of hysteresis controller levels. These vectors are obtained from the sum of two voltage vectors. In this way, we will have 12 voltage vectors in addition to the diode clamped inverter’s voltage vectors. Therefore, we can increase the number of torque hysteresis levels from 7 levels to 11 levels.Results: Considering that the proposed method uses virtual vectors and voltage vectors, it does not increase the cost and computational complexity. Also, one of the requirements of using this method is the use of fixed switching frequency, which solves the variable switching frequency problem of conventional methods. Therefore, the proposed control reaches an overall optimization.Conclusion: To verify the feasibility of the proposed method and compare it with the conventional method, both of these methods are simulated in the MATLAB /Simulink environment and the simulation results represent the efficiency of the proposed control method. This method achieves less torque ripple and harmonic current without increasing the cost and computational complexity.
M.R. Alizadeh Pahlavani; H. Damroodi
Abstract
This paper deals with the modeling, analysis, design and simulation of a robust control method for a permanent magnet synchronous machine (PMSM) supplied with a PWM inverter based on a LPV (Linear Parameter Variation) standard controller. Under the influence of uncertainties and external disturbances, ...
Read More
This paper deals with the modeling, analysis, design and simulation of a robust control method for a permanent magnet synchronous machine (PMSM) supplied with a PWM inverter based on a LPV (Linear Parameter Variation) standard controller. Under the influence of uncertainties and external disturbances, by a variation of ±150% of motor parameters from the nominal values, the robust performance control problem is formulated as a LPV standard scheme and solved by a suboptimal LMI (Linear Inequality Matrices) iterative strategy. This new design method is able to ensure the stabilization of the augmented system formed of the perturbed system with improved performance in face of parameter variation and external disturbances. A Simulation study was carried out to illustrate the effectiveness of the proposed method. The results obtained are compared with a simple conventional PI controller.
