Sharif Digital Repository

Switched reluctance motors (SRM) are one of the most reliable and cost effective motors and their applications are increasing in industry. However, it suffers from high level of torque ripple. In this paper, a new configuration for stator and rotor of SRM is presented. In the proposed method, a new saliency is developed to remove negative torque and therefore decrease torque ripple and acoustic noise, increase efficiency and as a result, expand speed range. The simulation results demonstrate that the new motor structure has a smooth torque profile with possibility to work at higher speed lower acoustic noise  

A space vector modulation (SVM) approach is proposed to control a four-switch rectifier with power factor correction and compensating the effect of capacitors voltage ripple. The theory and performance of this method are presented, and the method effectiveness is demonstrated by extensive simulations. The simulation results show that the capacitor voltage ripple effects in the output voltage and current shaping can be omitted and the rectifier can work agreeably under high power factor condition although capacitors voltage is not balance. The allowable amount of this unbalanced value of filter capacitors is determined  

The main purpose of this paper is to minimize the loss while reducing the flux and torque ripples in permanent magnet synchronous motors (PMSMs) under direct torque control (DTC). Offline method is used to minimize the loss and obtain the optimal flux. To reduce the amount of computation, the optimal flux table is produced according to the conditions in which the machine works. To reduce the flux and torque ripples and to control the switching frequency, SVM-DTC method is applied. Simulation results depict a noticeable increase in efficiency of the motor and a reduction in flux and torque ripples  

Voltage unbalance and short circuits in distribution networks adversely affect the performance of grid-tied voltage source inverters (VSIs). Consequently, the dc-link voltage ripple may significantly increase leading to operation of VSI in an unsatisfactory manner. Conventionally in order to maintain the negative sequence current under unbalanced conditions, low-pass/trap filter in the current control loop are required which significantly reduce the controller bandwidth. In order to minimize the dc-link voltage ripple without impairing the controller bandwidth, this paper investigates the design and performance of Proportional-Integral-Resonant (PIR) controller in improving the performance... 

A side coupled integrated spaced sequence (SCISSOR) of Silicon or Chalcogenide glass microrings of different diameter are considered as a wide-band Raman amplifier. Because the two-photon absorption (TPA) losses in Chalcogenide glass are less than that of Silicon, it is shown that Chalcogenide microrings are suitable for wide-band Raman amplifier in the telecommunication bandwidth (1.5 μm). The Lagrange unknown multiplier method is employed to minimize the gain ripple of the amplifier versus the pump and system parameters. Crown Copyright © 2008  

We propose a perturbation method for time division multiplexed (TDM) pumping fiber Raman amplifier (FRA). The method is based on the solution of Raman partial differential equations (PDEs) by a closed integral form. Taking the signals and pumps power as the interim solution and updating their values in an iterative process, Raman gain and pump/signal evolution can be calculated in any order of accuracy. In the first order of perturbation, some analytical formulas for the FRA dynamic control are obtained. Analytical formulas are employed for gain ripple minimization and also the gain clamping problem under channel reconfiguration. © 2009 Elsevier Inc. All rights reserved  

In a motor-drive system, there are many factors which can be considered as a figure of merit in drive control algorithm. All of these factors should be evaluated simultaneously to achieve the reliable performance of drive. In this paper, an optimization problem is constructed on a direct torque controlled induction motor drive using a candidate from different parts of drive system: inverter loss from section of solid state converter, motor loss from section of electromechanical converter and torque ripple from mechanical section. Minimization of this cost function leads to the optimum values of drive control parameters. © 2008 IEEE  

In this paper, the axiomatic design is introduced for controlling a power electronic converter. The main idea of axiomatic design is to introduce variables affecting the desired performances of the system most independently possible. The control process is presented for a Buck converter to achieve constant efficiency and output voltage ripple. ©2008 IEEE  

This paper presents a single-phase phase-locked loop (PLL) system which is primarily free from the double-frequency ripples from which the conventional PLL system suffers. The proposed PLL is then extended to reject the harmonic components from the input signal and to estimate the phase-angle and frequency of the distorted input signal with no error. Three units of the proposed PLL can be used in three-phase power systems, such as FACTS and HVDC converters, to estimate the phase-angles of the individual phases with no double-frequency ripples and without sensitivity to the presence of harmonics and inter-harmonics. This makes the proposed PLL unique and desirable for applications which... 

A new switching table is proposed for decreasing the torque ripple in DTC especially in low speed. Each sector is divided to two half sector and a proper vector set is defined for each. Through this new switching table, the torque response is smooth even in the beginning of each sector and it leads to the reduction of torque ripple. None of motor parameters are used in this switching strategy and there is no need to shorten the sampling period. Simulation and experimental results confirm the ability of this method in reducing the torque ripple. ©2004 IEEE  

Torque ripple is a major difficulty in direct torque controlled induction motors. The reference value of the motor flux greatly influences the torque ripple. On the other hand, many motors work in an operating cycle, which includes load intervals of less than their nominal power. In these situations, it is not necessary to set their flux value as the nominal value. In this paper, the effect of the reference value of the motor flux on the motor torque ripple is investigated. A new control algorithm is proposed to determine the reference value of the flux according to the value of the motor torque. Simulation and experimental results justify the validity of the proposed method to reduce the...