Murat Erhan Balci

This study aims to investigate the performance of wireless power transfer (WPT) circuits with S–S and S–P compensation topologies under unbalanced grid voltages. The studied WPT systems, fed by a three-phase uncontrolled six-pulse rectifier and a high-frequency inverter, are modelled in the time-domain using Matlab/SIMULINK. Voltage unbalance scenarios are generated considering two voltage unbalance factor (VUF) levels (2.5% and 5%), three positive-sequence voltage magnitudes (Vₚ = 0.90, 1.00, and 1.10 pu), and phase angle (θₙₚ) variations of the complex VUF from 0° to 315°. The performances of the systems are comparatively evaluated regarding efficiency (η), rectifier power factor (PF₆p), DC load voltage (Vo), voltage ripple ratio (ΔVo), current total harmonic distortion (THDI), and current unbalance factor (CUF). Results show that increasing VUF leads to higher THDI, CUF, and ΔVo levels while reducing PF₆p. An increase in Vₚ raises ΔVo in the system with S–S topology but reduces it in the system with S–P topology. Although higher Vₚ improves efficiency under unbalanced conditions, it worsens CUF and THDI. Performance indices exhibit oscillatory variations with respect to θₙₚ. Overall, the system with S–P topology shows lower sensitivity to voltage unbalance than the system with S–S topology.

In this study, firstly, the harmonic distortions of terminal voltage and current of a three-phase 1,5 kVA, 150V, 50 Hz, and four poles permanent magnet excited Claw Pole Synchronous Generator (CPSG) supplying a 6-pulse rectifier load are simulated using its 3D Finite Element Model (FEM) in Ansys Maxwell software environment. Then, various low-pass passive filters are designed with a practical approach to reduce the terminal voltage and winding current harmonics in the analysis system. Finally, the terminal voltage and current harmonic distortions, losses, torque oscillations, and efficiency of the modelled CPSG are evaluated when the designed filter is connected to the system. According to the numerical results obtained, the best-performing filter among the designed ones is determined. It is also concluded that with the help of this best-performing filter, the terminal voltage harmonic distortion, losses, torque oscillations, and efficiency of the CPSG are considerably improved.

Bu çalışmada, çeşitli konut tipi yüklerin sinüzoidal ve çok sayıda rastgele bozulmaya sahip besleme gerilimleri altında çektikleri akımların harmonik bileşenleri, toplam harmonik bozulma ve akım tepe faktörü ile güç faktörü indislerinin istatistiksel analizi amaçlanmıştır. Çalışmada, rezistif yük besleyen tam köprü doğrultucu (Yük 1), rezistif yük besleyen yarım dalga doğrultucu (Yük 2), rezistif yük besleyen dimmer devresi (Yük 3), batarya şarj eden tam köprü doğrultucu (Yük 4), daimi kondansatörlü tek fazlı asenkron motor (Yük 5) ve ısıtıcı (Yük 6) olmak üzere altı farklı yük tipi Matlab/SIMULINK ortamında modellenmiştir. İstatistiksel analizde, sinüzoidal anma gerilimi ile farklı harmonik bileşenlere sahip ve toplam harmonik bozulma değeri %3.99 ile %7.36 arasında değişen 1000 adet bozulmuş gerilim senaryosu dikkate alınmıştır. Analiz sonuçları modellenen yüklerin güç kalitesi indislerinin şebeke gerilimi harmonik bozulmasından ihmal edilemeyecek derecede etkilendiğini, ancak bu etkinin özellikle ilk iki yükte diğerlerine nazaran daha yüksek olduğunu göstermiştir.

The synchronous generators (SGs) supplying non-linear loads have harmonically distorted terminal voltages. Hence, these distorted terminal voltages adversely affect the performance parameters of the supplied loads such as the power factor, current distortion, losses, and efficiency. To mitigate the harmonic voltages and currents, passive and active filters are generally employed. However, passive filters cause resonance problems, while active filters can cause high costs. On the other hand, in several recent studies to reduce the SG’s terminal voltage harmonic distortion, which depends on the constructional design under the no-loading condition, the conventional DC excitation current has been modulated with AC harmonic components. These field current modulation methods have high computational complexity, and require extra hardware for their implementation. In the present paper, firstly, for the reduction of the terminal voltage harmonic distortion of the SG under non-linear loading conditions, the validity of the field current modulation technique is investigated. The numerical results show that by using the field current modulation method, under rated loading conditions, the total harmonic distortion of the terminal voltage can be reduced from 18% to 11%. Secondly, to provide a computational efficient and low-cost tool for optimal field current modulation, which minimizes the terminal voltage harmonic distortion, an Artificial Neural Network (ANN)-based model is proposed. Finally, with the integration of ANSYS Maxwell, ANSYS Simplorer, and MATLAB/Simulink software, the implementation of the developed model is demonstrated for the construction of the optimally modulated field current.

This paper presents a reluctance‐based model considering the frequency‐dependent loss nature of the windings for the analysis of three‐phase five‐leg transformers under grid voltages with direct current (DC) bias. This is very important especially for proper determination of their harmonic current distortion and maximum loading capability (MLC) under DC‐biased grid voltage conditions. To figure out the developed model's validity under sinusoidal and DC‐biased grid voltage cases, it is comparatively analyzed with the model based on 2D finite element method (FEM). Thus, for the considered transformer type operated under DC bias, the excitation current's harmonic pollution, losses, and reactive power demand parameters are analyzed by using the developed model. Additionally, by regarding these performance parameters, the DC susceptibilities of the considered‐type transformer and the single‐phase shell‐type transformer are comparatively evaluated. Finally, for the studied grid voltage conditions, the effects of two important design considerations as (i) magnetic core material selection and (ii) legs’ cross‐sectional area sizing on the MLC are investigated. It is concluded from these investigations that under saturation conditions, the transformers, which have the core material with higher permeability or lower reluctance, draw higher excitation current, and have lower MLC ratio when compared to ones having the core material with lower permeability or higher reluctance. However, for unsaturated transformers, which work under DC bias, the case is the opposite to that in saturation conditions. On the other hand, under DC bias conditions, the effect of cross‐sectional area sizing on the MLC ratio is much more for the transformer with high permeable magnetic core material with regards to ones with low permeable magnetic core material.

Bu makalede, küçük güçlü düşük hızlı rüzgar türbinleri için radyal akılı kalıcı mıknatıslı senkron generatörlerin (KMSG’lerin) tasarımı ile Ansys Maxwell yazılım ortamında modellenmesi ve performans analizi üzerine örnek bir çalışma sunulmuştur. Bu örnek çalışmada, öncelikle analitik ifadeler kullanılarak; hedeflenen anma değerlerine sahip bir KMSG tasarımı yapılmıştır. Devamında, Ansys Maxwell yazılım ortamında iki boyutlu modelleme yaklaşımıyla, tasarımın, yüklenme oranı değişimine bağlı olarak gerilim etkin değeri, gerilim toplam harmonik bozulma değeri, akım etkin değeri ve verim performans parametrelerinin değişimi, ayrıca milin dönme hızının değişimine bağlı olarak bu dört performans parametresinin yanı sıra üretilen azami aktif güç değerinin değişimi analiz edilmiştir.

In this paper, a reluctance-based model is developed for time-efficient analysis of shell type single-phase power transformers under the direct current (DC) bias conditions. Unlike other reluctance-based transformer models in the literature, the developed one considers frequency dependent nature of the winding resistances. This is important especially for accurate determination of losses and maximum loading capability (MLC) of the transformers under DC bias and non-sinusoidal conditions. In addition to that, by using the developed model, three different MLC determination approaches, which are based on the rated primary side current, rated total loss and rated primary winding loss, are examined for DC bias conditions. These novel examination results clearly point out that among three approaches the rated primary winding loss-based one should be preferred for the safe operation of the transformers in the systems with DC bias.