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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

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.