Sharif Digital Repository

Simplified equations are used for the analysis of a dual active bridge converter leading to a conservative estimation of the zero voltage switching (ZVS) region. The ZVS is directly affected by the inserted deadband in each leg of the converter. In this paper the impact of the ZVS capacitor and deadband on soft switching region for this converter is analyzed. Also, the sufficient constraints for ZVS condition in the input and output bridges are determined by analyzing the circuit behavior during the bridges deadband. Simulation results of a 700V-350V, 50-kW DC-DC converter validate the analysis. © 2017 IEEE  

The notable effeets of time delay aid time discretization on the torque and current ripple amplitude of the direct torque controlled induction motor scheme are investigated. A simply modified torque hysteresis comparator structure is proposed. It minimizes the undesirable effects of the time delay and time discretization on the torque ripple and allows a sensible reduction of torque and current ripple amplitudes and switching frequency in the whole rotor speed range. Numerical simulations and experimental tests have been carried out to validate the proposed torque comparator effect. © 2004 IEEE  

A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In order to reach the high power density, the volume of the converter must be decreased. The basic idea to reduce the component size is to increase the switching frequency which causes the higher switching loss and reduces the efficiency of the converter. In this paper, the power losses of the three-phase DAB dc/dc converter are formulated and the variation of the efficiency as a function of switching frequency is investigated. In this analysis, the switching loss of the... 

The efficiency of induction motors decreases at light loads. Efficiency optimizer control systems adjust the motor flux value to achieve the best efficiency in a wide range of load variations. Reduced flux operation has some other benefits such as power factor improvement and torque ripple reduction. The latter is an important issue in a direct torque controlled induction motor drive. In this paper, the effect of flux reference value on the torque ripple of a direct torque controlled induction motor is analyzed. The effect of flux value on torque ripple in a wide range of speed variations is investigated. Simulation and the experimental results presented justify the validity of the... 

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... 

Torque ripple is a major difficulty in direct torque control of 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. The effect of the flux reference variation on the motor power factor as well as torque dynamics is also presented. Simulation results as well as experimental results justify the validity of the proposed method on the... 

A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In this paper, the three-phase DAB dc/dc converter is analyzed during its deadband. Moreover, the influence of the zero-voltage-switching (ZVS) capacitor and deadband on ZVS region are investigated by utilizing an accurate circuit analysis during the deadband. The theoretical results are verified in simulation and in a50 kW experimental setup. © 2017 IEEE