다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Thyristor-Based FACTS Controllers for Electrical Transmission Systems

This paper discusses the power quality issues for distributed generation systems based on renewable energy sources, such as solar and wind energy. A thorough discussion about the power quality issues is conducted here. This paper starts with the power quality issues, followed by discussions of basic standards. A comprehensive study of power quality in power systems, including the systems with dc and renewable sources is done in this paper. Power quality monitoring techniques and possible solutions of the power quality issues for the power systems are elaborately studied. Then, we analyze the methods of mitigation of these problems using custom power devices, such as D-STATCOM, UPQC, UPS, TVSS, DVR, etc., for micro grid systems. For renewable energy systems, STATCOM can be a potential choice due to its several advantages, whereas spinning reserve can enhance the power quality in traditional systems. At Last, we study the power quality in dc systems. Simpler arrangement and higher reliability are two main advantages of the dc systems though it faces other power quality issues, such as instability and poor detection of faults.

https://vbn.aau.dk/ws/files/294611667/08314672.pdf

Analysis and Mitigation of Power Quality Issues in Distributed Generation Systems Using Custom Power Devices

An improved residual-based convolutional neural network for very short-term wind power forecasting

Photovoltaic panels are semi-conductor structures that can convert solar energy directly to direct current (DC) electricity power depending on the solar irradiance and ambient temperature. They have a non-linear current-voltage (I-V) characteristic due to their structure. The maximum power obtained from a photovoltaic panel is directly related to solar irradiance and panel temperature. Photovoltaic panels offers a single maximum power point under certain atmospheric conditions (solar irradiance and ambient temperature). Therefore, it is of vital importance to use photovoltaic panels along with maximum power point tracking systems for a more efficient solar power system. Since constantly changing atmospheric conditions (solar irradiance and temperature) and variable load cause changes in maximum power point, the maximum amount of power generated by a photovoltaic panel needs to be tracked continuously. There are various tracking methods such as classical and modern methods for maximum power point tracking. Perturb and observe (P&O), hill climbing (HC), incremental conductance (INC) are among conventional methods, while modern methods include artificial neural networks, fuzzy logic and optimization algorithms. Modern control structures such as fuzzy logic and artificial neural networks are widely used to perform many applications. Using fuzzy logic and artificial neural networks together creates an adaptive control structure, which adjusts changes in the operating point of the control system in a better way. In the present study, a two-loop tracking system consisting of incremental conductance and neuro-fuzzy control is proposed for maximum power point tracking of a photovoltaic system under variable load and solar irradiance. The dynamic performance of the proposed two-loop tracking system was compared with the single-loop incremental conductance method under variable load and solar irradiance. It was observed that the proposed tracking structure better adapted to the changes in the maximum power operating point of the photovoltaic system compared to the incremental conductance method in both cases.

/pdf/fotovoltaik-sistemlerde-degisken-yuk-ve-gunes-isinimi-3io2vg22xf.pdf

Fotovoltaik Sistemlerde Değişken Yük ve Güneş Işınımı Altında Sinirsel-Bulanık Denetleyici ile Maksimum Güç Noktası Takibi

In recent years, adaptive and intelligent control schemes have begun to take the place of conventional control methods. In this study, a model reference adaptive control (MRAC) scheme based on genetic algorithm (GA) and Fuzzy Logic (FL) has been used by the help of Vector Control type driving method based on Space Vector Pulse Width Modulation (SVPWM). In this control technique, the conventional PI controller and the proposed control strategy has been applied to induction motor in real conditions by using an appropriate digital signal processor and peripheral units. As digital processor, DSPIC 30F6010 which is produced by Microchip Co. has been used. Experimental studies have been implemented for both of the control techniques under the same conditions. The results obtained from conventional PI controller and the proposed control strategy have been analysed and compared.

Speed control of induction motor based on model reference adaptive control

Enerji kalitesi gunumuzde hem ureticiyi hem de son tuketiciyi cok ilgilendirir hale gelmistir. Kaliteli elektrik enerjisi kisaca, sureklilik (kesintisiz enerji), sabit frekans ve sabit genlige sahip sinuzoidal gerilim ile aciklanabilir. Elektrik enerjisinin sinuzoidal formdan uzaklasmasi harmonik olarak tanimlanir. Harmonikler enerji kalitesinde cok onemli bir yer tutarlar. Endustriyel tesislerde ozellikle harmoniklerin ve gerilim dusumlerinin sikca rastlanmasi, hem tesiste hem de sebekede onemli sorunlara yol acmaktadir. Bu sorunlar maliyetleri etkilemektedir. Bu calismada bir Tas kirma tesisinde guc kalitesi olcumleri gerceklestirilmistir. Guc analizoru ile harmonikler ve gerilim dusmeleri olculmustur. Yapilan olcumlerde tesisin guc kalitesi seviyesinin cok kotu olmadigi gorulmustur. Bununla beraber tesise, harmonik filtreli kompanzasyon sistemi kurulmasi onerilmektedir.

/pdf/bir-tas-kirma-tesisinde-guc-kalitesi-seviyesinin-olcumu-ve-4wkj7h5qik.pdf

Bir Taş Kırma Tesisinde Güç Kalitesi Seviyesinin Ölçümü ve Değerlendirilmesi

Ruzgâr enerjisi santrali (RES) kurulumunda turbinlerin mikro yerlesimi en onemli konulardan biridir. Turbinlerin uygun sekilde yerlestirilmesi RES’in uretim miktarinin artmasini saglamaktadir. Bu calismada RES kurulumu icin bir optimizasyon modeli gelistirilmistir. Ilk olarak RES’in kurulacagi bolge karesel alanlara bolunmustur. Bu alanlardaki ruzgâr hizi olasilik yogunluk fonksiyonu Weibull egrisi kullanilarak modellenmistir. Bu egrinin A ve k parametreleri WAsP (Ruzgâr Atlasi Analiz ve Uygulama Programi) yazilimindan elde edilmistir. Daha sonra bu alanlara turbin yerlestirilmesi durumunda uretilecek enerji, olasilik yogunluk fonksiyonu ve turbin guc egrisi kullanilarak hesaplanmistir. Modelin cozumunde Genetik Algoritma (GA) kullanilmistir. Turbin koordinatlari, RES'in enerji uretimini en ust duzeye cikarmaya yardimci olan GA tarafindan belirlenmistir. Modelin uygulamasindaki RES Danimarka Roskilde bolgesine kurulmustur. Bolge 20×20 adet karesel alanlara bolunmustur. RES her birinin gucu 2 MW olan 10 adet Bonus turbinden olusmaktadir. Son olarak ise WAsP yazilimindan guc yogunlugu haritasi elde edilmistir. Model cozumunde bulunan koordinatlara turbinler yerlestirildiginde, koordinatlarin en yuksek guc yogunluguna sahip alanlar oldugu gorulmustur. Bu sonuc, onerilen modelin RES kurulumunda etkili bir sekilde turbin yerlesimi yaptigini gostermistir.

/pdf/ruzgar-enerji-santrali-kurulumunda-ruzgar-turbinlerinin-3j3bpvwikl.pdf

Mustafa Şekkeli

Papers

Fotovoltaik Sistemlerde Değişken Yük ve Güneş Işınımı Altında Sinirsel-Bulanık Denetleyici ile Maksimum Güç Noktası Takibi

Speed control of induction motor based on model reference adaptive control

Bir Taş Kırma Tesisinde Güç Kalitesi Seviyesinin Ölçümü ve Değerlendirilmesi

Rüzgâr Enerji Santrali kurulumunda rüzgâr türbinlerinin mikro yerleşimi için bir optimizasyon modeli

Modeling and analysis of three-phase space vector pulse width modulation based rectifiers using fuzzy-pi controller