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Showing 4 results for Rastegar
DFIG Based Wind Turbines Behavior Improvement during Wind Variations using Fractional Order Control Systems
M. Hosseinabadi, H. Rastegar,
Volume 10, Issue 4 (December 2014)
Abstract
This paper is concerned with behavior analysis and improvement of wind turbines with Doubly Fed Induction Generator (DFIG) when using a new fractional-order control strategy during wind variations. A doubly fed induction generator, two types of variable frequency power electronic converters and two input wind waveforms are considered. A fractional-order control strategy is proposed for the wind turbine control unit. Output parameters of the wind turbine are drawn by simulations using MATLAB/Simulink for both fractional-order and integer-order (classic) control systems and a complete comparison between these two strategies has been presented. Results show a better operation when using fractional-order control system.
Space Vector Modulation Technique to Reduce Leakage Current of a Transformerless Three-Phase Four-Leg Photovoltaic System
F. Hasanzad, H. Rastegar, G. B. Gharehpetian, M. Pichan,
Volume 13, Issue 2 (June 2017)
Abstract

Photovoltaic systems integrated to the grid have received considerable attention around the world. They can be connected to the electrical grid via galvanic isolation (transformer) or without it (transformerless). Despite making galvanic isolation, low frequency transformer increases size, cost and losses. On the other hand, transformerless PV systems increase the leakage current (common-mode current, (CMC)) through the parasitic capacitors of the PV array. Inverter topology and switching technique are the most important parameters the leakage current depends on. As there is no need to extra hardware for switching scheme modification, it's an economical method for reducing leakage current. This paper evaluates the effect of different space vector modulation techniques on leakage current for a two-level three-phase four-leg inverter used in PV system. It proposes an efficient space vector modulation method which decreases the leakage current to below the quantity specified in VDE-0126-1-1 standard. furthermore, some other characteristics of the space vector modulation schemes that have not been significantly discussed for four-leg inverter, are considered, such as, modulation index, switching actions per period, common-mode voltage (CMV), and total harmonic distortion (THD). An extend software simulation using MATLAB/Simulink is performed to verify the effectiveness of the modulation technique.


A New Non-linear Control of the Four-Leg Inverter with Decoupled Model and Fast Dynamic Response for PV Generation Systems
M. Pichan, E. Heydari, H. Rastegar,
Volume 13, Issue 4 (December 2017)
Abstract
Distributed generation (DG) will play an important role in future power generation systems, especially in stand-alone applications. Three phase four-leg inverter is a well-known topology which can be used as an interface power converter for DGs. Thanks to the fourth leg to provide the neutral path, the four-leg inverter is able to supply balanced loads as well as unbalanced loads. In this paper, the model of a three phase four-leg inverter with the fourth leg inductor in the αβγ reference frame is investigated thoroughly. Afterward, a decoupled model of the four-leg inverter is adopted to establish the proposed control method. Among non-linear control methods, pole-placement method is a famous solution to ensure fast transient response. Hence, in this paper, a pole-placement method via state feedback is proposed to control the output voltage of the four-leg inverter. Using this method, the transient performance of the system can be adjusted well. On the other hand, to guarantee good performance of the control system under steady state condition, a lead compensator is proposed to be used with the pole-placement method. Therefore, the proposed control system not only can provide fast dynamic response but also, it ensures very low steady state error. To validate the superior performance of the proposed control method, simulation and experimental results under various loading condition are provided based on a DSP-based digital control system.

A New Pulsating Power Elimination Method for Single-Phase PWM AC/DC Converters with Minimum Voltage and Current Stress
H. Rezaie, H. Rastegar, M. Pichan,
Volume 14, Issue 1 (March 2018)
Abstract
An inherent problem of single-phase rectifiers is the existence of a pulsating portion in the input power, which pulsates at twice the grid frequency. If this pulsating power is transferred to the DC-link, it causes a significant amount of second-order harmonic at the output voltage. Since in many applications, such a high level of DC oscillation is not acceptable, so the pulsating power must be effectively filtered. A convenient solution to eliminate the output voltage oscillations is to use a capacitor with a relatively high capacity at the rectifier output. Due to the fact that the high capacity capacitors for this application usually have a short lifetime and occupy a lot of space, this solution cannot be considered as a proper one. In this paper, a new active method with the minimum of current and voltage stress is proposed to effectively eliminate the pulsating power and significantly reduce the required capacitance of the output filter. The proposed method is able to reduce the volume of the converter and increase its reliability and power density. The validity and effectiveness of the proposed method are confirmed by extensive simulations in the MATLAB/Simulink.

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© 2022 by the authors. Licensee IUST, Tehran, Iran. This is an open access journal distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.