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1

Multi-machine power system fuzzy stabilizer design using Cuckoo search algorithm

Koochaki A., Skandarnezhad A., Mohammadmoradi Y., Salimi S.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 3

1--5

EN

Nowadays, fuzzy controllers have achieved an important role in different systems and their superiority over the classical control methods has been proved. In this study, the power system stabilizer is used to damp the power system oscillations based on the fuzzy logic controller. A three-phase to ground-fault test is done during a period of 10 ms to evaluate power system behaviour between the area of two distinct points. Simulation results show that the system is unstable without a stabilizer. It has also been determined that the fuzzy stabilizers have high ability to damp the system oscillations in comparison with classical stabilizers so that system oscillations are damped with higher speed and lower amplitude. Also in this study, the Cuckoo search algorithm is used to optimize the fuzzy stabilizer inputs and improve its performance. The results show that the optimizations of stabilizer parameters improve their damping performance.

PL

W artykule opisano algorytm typu Fuzzy logic wykorzystany do tłłumirnia oscylacji w systemie zasilania.Wykoyowany jest test systemu między dwoma odległymi punktami. W porównaniu z klasycznymi sterownikami zaproponowany sterownik oscylacje tłumione sa szybciej i skuteczniej.

2

Lagrangian modelling of a synchronous step-down converter by considering the parasitic elements

Skandarnezhad A., Koochaki A., Mohammadmoradi Y., Kalteh A.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 3

6--10

EN

This paper introduces a new technique to model a synchronous buck converter in the closed loop compensated conditions by Lagrange equation. In the design process of converters it is desirable to assess as many critical design parameters and parasitic effects by simulation as possible, since the control is hard to tune after fabrication. The main advantage of this method is its versatility and simple implementation. In this work, switch conduction loss of an integrated, synchronous buck converter is identified to have significant influence on control loop dynamics. Thus, an equivalent small-signal model for the close loop frequency response accounting for switch conduction loss is developed. Finally, the model is validated against the frequency response obtained by periodic stability analysis which can account for parasitic effects and loading. Very good agreement between the extended model and the simulation results obtained.

PL

W artykule opisano modelowania z wykorzystaniem równań Lagrange synchronicznego przekształtnika typu buck. Straty przełączania są identyfikowane jako wpływające na dynamikę. Analizowano okresową stabilność z uwzględnieniem efektów pasożytniczych.

3

Critical Current Control (C3) and Modelling of a Buck Based LED Driver with Power Factor Correction

Skandarnezhad A., Rahmati A., Abrishamifar A., Shahmohammadi S.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 10

134-138

EN

Buck converter has a good aptitude for LED driver application. Here a new technique introduced to control and model a buck converter in the closed loop condition using Lagrange equation. To improve the final model accuracy, parasitic elements of the converter are taken into account. The main advantage of this method is its novelty and simple implementation. Also, the converter power factor has improved under critical current control (C3) technique. Frequency response and step response of the small signal model are derived and analysed. The theoretical predictions are tested and validated by means of PSIM software. Finally, precise agreement between the proposed model and the simulation results has obtained.

PL

W artykule analizowano zastosowanie przekształtnika typu buck do zasilania diod LED. Zaproponowano nowy układ z uwzględnieniem elementów zakłócających pracę. Zastosowano sterowanie prądem krytycznym dla poprawy jakości pracy przekształtnika. Analizowano właściwości dynamiczne układu.

4

A New Technique to Suppress the Common Mode Conduction Noise of the Boost Converter

Rahmati A., Abrishamifar A., Skandarnezhad A.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 10

144-147

EN

EMI filter is an essential part of the modern switching power supplies contributing to significant price and size. This paper presents a new method to reduce the common mode (CM) electromagnetic interference (EMI) of the boost converter. Conventional methods rely on impedance mismatch or active noise cancellation, but the proposed method uses a passive branch with matched impedance to suppress the CM current. An external inductor is connected between the transistor drain and middle of input dc bus before EMI filter. A Wheatstone bridge is then identified in the CM equivalent circuit of the converter with these additional components. By selecting the inductor value properly the Wheatstone bridge will be balanced and results in suppression of the input CM current. The analysis shows that the presented method can guarantee the required attenuation for CM conduction noise. Finally, a comparison between the balanced and unbalanced structure is presented using computer simulation by Pspice.

PL

W artykule zaprezentowano nową metodę redukcji składowej wspólnej elektromagnetycznych interferencji w przekształtniku typu boost. W metodzie zastosowano pasywny układ do dopasowania impedancji w celu zmniejszenia składowej wspólnej prądu. Wstawiony w układ mostka dławik umożliwia zrównoważenie tego mostka.

5

A New Input Clamped Bi-directional Boost Converter for Electric Vehicle Charging with Unity Power Factor

Amirkhan S., Skandarnezhad A., Koochaki A., Mokhtari R.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 10

139-143

EN

This paper presents a new synchronous boost converter without input diode bridge. Also its source voltage is clamped using a capacitor. This converter employed as an electric vehicle (EV) charger. Its control circuit designed so that the converter input current is sinusoidal and in-phase with the main voltage, then its power factor (PF) reaches unity. It is able to bi-directional power flow capability. A bias capacitor connected in series with the ac source provides a dc voltage clamp at the input, thus input voltage remains always positive. This converter may be controlled to draw sinusoidal average current at the ac side that is either in-phase or any phase difference from the ac source. Hence, it can provide either unity power factor rectification or inversion. Mosfet devices with anti-parallel diodes are used as switches. The efficiency achieved was over 90% and the THD of the input current is under 3%. High frequency noise filter where is placed in the input side guarantees the electro-magnetic compatibility. This topology is superior to conventional rectifier followed by a dc/dc boost converter because of diode bridge elimination and removal of crossover distortions that are inevitable in conventional Active Power Factor Correction (APFC) circuits. Finally, the proposed converter is simulated using Psim software under the hysteresis control method. Very good agreement between the theatrical and simulation results are obtained.

PL

W artykule opisano przekształtnik typu boost bez wejściowego mostka diodowego. Przekształtnik zastosowano jako układ ładujący w pojazdach elektrycznych. Układ zaprojektowano w ten sposób że sinusoidalny prąd wejściowy jest w fazie z napięciem a więc spółczynnik mocy jest równy jedności. Kondensator na wejściu separuje składową stałą napięcia ładującego.