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1

A novel modified AC/AC Z-Source converter for starting current reduction for three-phase induction motor

Ngamkong Phurich, Photong Chonlatee

Przegląd Elektrotechniczny

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2023

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R. 99, nr 5

133--138

EN

Induction motors inherently have very high current in order to provide sufficient power and torque for the loads when started. This very high current can cause the damage for the motors and other components. Therefore, an additional electronic soft starter such an AC/AC converter is commonly used to reduce this current but the reduced current is still high and relatively has high harmonics. This paper proposes a novel electronic soft starter, a modified AC/AC Z-Source converter for the three-phase induction motor. The proposed soft starter could directly convert AC voltage from a three-phase power supply with constant voltage and frequency by adjusting voltage together with the additional impedance source. The performance in terms of starting current reduction capacity and harmonic reduction capacity of the proposed starter with/without the overlap switching state implementation was examined and evaluated in comparison to the conventional starter with an AC/AC converter. These starter circuits were simulated via the computer program by operating at 3 load torque conditions: without load, half load and full load. The test results showed that the proposed starter with overlap switching state implementation provided the lowest starting current and lowest current harmonic distortion at the full load, following by the proposed starter without the overlap switching state implementation and a conventional starter, respectively. In turn, the proposed starter without the overlap switching state implementation provided the fastest settling times.

PL

Silniki indukcyjne z natury miały bardzo wysoki prąd rozruchowy, aby zapewnić wystarczającą moc i moment obrotowy dla obciążeń, co może spowodować uszkodzenie silników i innych komponentów. Dlatego do zmniejszenia tego prądu stosuje się softstarter elektroniczny, taki jak konwerter AC/AC, ale prąd zredukowany jest nadal wysoki i ma stosunkowo wysokie harmoniczne. W artykule zaproponowano nowatorski elektroniczny softstart, zmodyfikowany konwerter AC/AC Z-Source, do trójfazowego silnika indukcyjnego. Proponowany softstarter mógłby bezpośrednio przekształcać napięcie prądu przemiennego z trójfazowego źródła zasilania o stałym napięciu i częstotliwości poprzez regulację napięcia wraz z dodatkowym źródłem impedancji. Zbadano i oceniono wydajność w zakresie zdolności redukcji prądu rozruchowego i zdolności redukcji harmonicznych proponowanego rozrusznika z/bez implementacji stanu przełączania nakładkowego w porównaniu z konwencjonalnym rozrusznikiem z przekształtnikiem AC/AC. Te obwody rozruchowe symulowano za pomocą programu komputerowego, pracując w 3 warunkach obciążenia momentem obrotowym: bez obciążenia, połowicznego obciążenia i pełnego obciążenia. Wyniki testów pokazały, że proponowany rozrusznik z implementacją stanu przełączania nakładkowego zapewniał najniższy prąd rozruchowy i najniższe zniekształcenia harmoniczne prądu przy pełnym obciążeniu, zastępując odpowiednio rozrusznik bez implementacji stanu przełączania nakładkowego i rozrusznik konwencjonalny. Z kolei proponowany starter bez implementacji stanu przełączania nakładania zapewniał najszybsze czasy rozliczania.

2

Generalized state space model and small signal stability analysis of Z-source converter

Kouhanjani Masoud Jokar, Soltani Sina, Mardaneh Mohammad

Archives of Electrical Engineering

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2023

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Vol. 72, nr 1

173--188

EN

This paper proposes two nonlinear exact and simple state space models of a Z-source converter (ZSC) connected to an ac grid. A generic model of a ZSC accompanied with proper controllers are proposed and a dynamic model of the whole system is derived; as a result, based on a simple one, an equivalent block diagram of the current-controlled ZSC system is proposed. The ac small signal stability method is applied and the impact of controller parameters on network’s stability is discussed. Besides, overall system dynamic performance has been assessed in the event of perturbations. Time-domain simulations have been implemented in PSCAD/EMTDC to validate the accuracy of the models and effectiveness of the proposed controllers. The results of the exact model are compared with the response of the equations which are applied in MATLAB.

3

Analysis of loss distribution of conventional boost, Z-source and Y-source converters for wide power and voltage range

Gadalla B. S., Schaltz E., Siwakoti Y., Blaabjerg F.

Transactions on Environment and Electrical Engineering

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2017

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Vol. 2, No. 1

1--9

EN

Boost converters are needed in many applications which require the output voltage to be higher than the input voltage. Recently, boost type converters have been applied for industrial applications, and hence it has become an interesting topic of research. Many researchers proposed different impedance source converters with their unique advantages as having a high voltage gain in a small range of duty cycle ratio. However, the thermal behaviour of the semiconductor devices and passive elements in the impedance source converter is an important issue from a reliability point of view and it has not been investigated yet. Therefore, this paper presents a comparison between the conventional boost, the Z-source, and the Y-source converters based on a thermal evaluation of the semiconductors. In addition, the three topologies are also compared with respect to their efficiency. In this study the results show that the boost converter has higher efficiency than the Z-source and Y-source converter for these specific voltage gain of 2 and 4. The operational principle, mathematical derivations, simulation results and final comparisons are presented in this paper.