Showing 4 results for Rostami
D. Arab Khaburi, H. Rostami,
Volume 7, Issue 1 (March 2011)
Abstract
This paper presents a method to control both the dc boost and the ac output voltage of Z-source inverter using neural network controllers. The capacitor voltage of Z-source network has been controlled linearly in order to improve the transient response of the dc boost control of the Z-source inverter. The peak value of the line to line ac output voltage is used to control and keep the ac output at its desired value. A modified space vector pulse-width-modulation method is also applied to control the shoot-through duty ratio for boosting dc voltage. This modified method lets the dc voltage stress across the inverter switches be minimized. The neural network control technique is verified by simulation results. The results are compared with that of the traditional PI controller.
H. Radmanesh, M. Rostami,
Volume 7, Issue 4 (December 2011)
Abstract
this work studies the effect of neutral earth resistance on the controlling ferroresonance oscillation in the power transformer including MOV surge arrester. A simple case of ferroresonance circuit in a three phase transformer is used to show this phenomenon and the three-phase transformer core structures including nonlinear core losses are discussed. The effect of MOV surge arrester and neutral earth resistance on the onset of chaotic ferroresonance and controlling chaotic transient in a power transformer including nonlinear core losses has been studied. It is expected that these resistances generally cause into ferroresonance control. Simulation has been done on a power transformer rated 50 MVA, 635.1 kV with one open phase. The magnetization characteristic of the transformer is modelled by a single-value two-term polynomial with q=7, 11. The core losses are modelled by third order in terms of voltage. The simulation results reveal that connecting the MOV arrester and neutral resistance to the transformer, exhibits a great impact on ferroresonance over voltages.
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B. Mamipour Matanag, N. Rostami, S. Tohidi,
Volume 17, Issue 2 (June 2021)
Abstract
This paper proposes a new method for direct control of active power and stator flux of permanent magnet synchronous generator (PMSG) used in the wind power generation system. Active power and stator flux are controlled by the proposed discrete time algorithm. Despite the commonly used vector control methods, there is no need for inner current control loops. To decrease the errors between reference and measured values of active power and stator flux, the space vector modulation (SVM) is used, which results in a constant switching frequency. Compared to vector control, the proposed direct control method has advantages such as higher dynamic response due to elimination of inner current control loops and no need to coordinate system transformation blocks as well as the PI controllers and their adjustment. Moreover, permanent magnet flux vector and several machine parameters such as stator inductances are not required which can improve the robustness of the control system. The proposed method can be used in both types of surface-mounted and interior PMSGs. The effectiveness of the proposed method in comparison to the vector control method with optimized PI coefficients by the particle swarm algorithm is evaluated. Simulation results performed in MATLAB/Simulink software show that higher dynamic response with lower active power and the stator flux ripple are achieved with the proposed method.
J. Sepaseh, N. Rostami, M. R. Feyzi,
Volume 17, Issue 4 (December 2021)
Abstract
A new axial magnetic gear (AMG) with enhanced torque density and reduced cogging torque is proposed in this paper. In the new structure, the direction and width of permanent magnets in high-speed rotor are changed and permanent magnets are removed from the modulator while the low-speed rotor remains unchanged. The torque density of the proposed magnetic gear is enhanced by using an appropriate direction and pole pitch for permanent magnets of high-speed rotor. The proposed AMG is compared with recent structures in the literature with the highest torque density. Three-dimensional (3D) finite element analyses are employed to obtain the cogging torque and torque density. The results of the analysis indicate that not only torque density increases but also cogging torque decreases dramatically.
