Control Architecture for Parallel Inverter in Uninterruptible Power Systems Chi Zhang, Student Member, IEEE, Josep M. Guerrero, Fellow, IEEE, Juan C. Vasquez, Senior Member, IEEE, Ernane A.A. Coelho, Member, IEEE

 

Abstract— In this paper, a control strategy for the parallel operation of three-phase inverters forming an online uninterruptible power system (UPS) is presented. The UPS system consists of a cluster of paralleled inverters with LC filters directly connected to an AC critical bus and an AC/DC forming a DC bus. The proposed control scheme comprises two layers: (i) a local layer that contains a “reactive power-to-phase droop” in order to synchronize the phase angle of each inverter and a virtual resistance loop that guarantees equal power sharing among inverters; and (ii) a central controller that guarantees synchronization with an external real/fictitious utility, and critical bus voltage amplitude restoration. Improved transient and steady-state frequency, active, reactive and harmonic power sharing, and global phase-locked loop resynchronization capability are achieved. Detailed system topology and control architecture are presented in this paper. Further, a mathematical model was derived in order to analyze critical parameters effects on system stability. The proposed control approach has been validated by means of experimental results obtained for several case-study scenarios. Index Terms— UPS system; parallel inverters; voltage restoration; droop control; virtual impedance

LINK:https://vbn.aau.dk/files/219215517/Zhang_Chi_trans_manu_doublecol.pdf

Updating and Customizing an industrial UPS HMI-A Master's Thesis Submitted to the Faculty of the Escola Tècnica d'Enginyeria de Telecomunicació de Barcelona Universitat Politècnica de Catalunya by Ali Ahmadi

 Abstract 

Uninterruptable Power Supply or UPS is one of the key parts of industries nowadays. Importance of it has risen because of the increasing demand for more stable power supply for Electronics and Electrical systems each year, especially in the field of IT and Data Servers. During these years, with improving Electrical products, Human Machine Interface became part of most electrical products and UPS is no exception. These days, UPS has a graphical display which according to the application of UPS, its design and abilities is different. HMI design for UPS has challenges, as instance: design according to the application, efficiency of design, preventing bugs, graphical design and etc. During this project, our plan is designing a new generation of Salicru HMI with the capability of adopting with old version Industrial UPS which manufactured by partner companies and also this HMI use for Salicru new generation UPS, Cube 4.

LINK: https://upcommons.upc.edu/bitstream/handle/2117/165610/TFM_Ali Ahmadi-Final Version.pdf

Optimal Design Method of the LLC resonant converter using the hybrid current balancing circuit for LED lighting -Author Jin-Gu Kim Department of Electrical & Medical Convergent Engineering Graduate School, Kangwon National University South Korea.

 

Optimal Design Method of the LLC resonant converter using the hybrid current balancing circuit for LED lighting  Author Jin-Gu Kim

 Department of Electrical & Medical Convergent Engineering Graduate School, Kangwon National University South Korea.

Abstract 

In this thesis, a novel hybrid current balancing circuit and an optimum design of LLC resonant converter for driving a current balancing circuit are proposed. 

First of all, the hybrid current balancing circuit was proposed for compensating current deviation among LED strings. LEDs have been widely used in lighting, automobiles, and airplanes owing to their excellent light output characteristics and long lifespan. Though LEDs are manufactured under the same process, variations in impurity concentrations cause electrical deviation among LEDs. This electrical deviation results in current unbalance of LED strings. The resulting current unbalance does not only reduce the life time of the LED but also cause non-uniform luminance of LEDs connected in parallel. The LED driving circuit is researched to solve the above problems. In this thesis, a novel hybrid current balancing circuit with a Y-type current balancing transformer and a voltage doubler rectifier circuit was proposed for the compensation of 6 LED strings with a simple structure.

 Secondly, the Optimal design method of LLC resonant converter for driving hybrid current balancing circuit was proposed. The difference between the proposed optimal design method of LLC resonant converter and conventional design method can be divided into three categories.

 First of all, when designing transformer with leakage inductance(Lr ) and magnetizing inductance(Lm), unwanted leakage inductance of secondary side (Lr2) which cause error in the process of measuring the leakage inductance (Lr ) with instrument occurs. This design error could be reduced by taking into account the leakage inductance of secondary side(Lr2). 

Secondly, in general, the voltage gain characteristic curve is applied to design LLC resonant converter. in this thesis, the current gain characteristic curve was applied to the design process which is suitable for LED that is non-linear load and necessary to be controlled to a constant current. 

Lastly, the equivalent circuit of LED was applied to the design process. Normally, a resistive load which has linear load characteristic is used for designing the LLC resonant converter. However, in this thesis, the equivalent circuit of LED which includes a voltage source, a resistor and a diode could be obtained by using the linear approximation method. This circuit was then applied to the design process for reducing design error. 

Experimental results are presented to verify the performance of the proposed hybrid current balancing circuit and the optimal design method of the LLC resonant converter. The LED maximum current error rate which was 19.57% was reduced to 4.5% by Y-type current balancing transformer. Also, the validity of the proposed optimal design method of the LLC resonant converter was verified by comparing it with the conventional design method. An 150W prototype was implemented and used for the performance verification of the hybrid current balancing circuit and the LLC resonant converter.

LINK: http://www.mediafire.com/file/sfzdhsuo3y91zod/file

Master's Thesis Design, Control, and Implementation of High Frequency LLC Resonant Converter-Author- Hwa-Pyeong Park Department of Electrical and Computer Engineering -ULSANG NATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY

 Master's Thesis

 Design, Control, and Implementation of High Frequency LLC Resonant Converter Hwa-Pyeong Park Department of Electrical and Computer Engineering 

 Abstract

 A high switching frequency operation has been introduced with much interest in research and industrial areas to improve the power density of power converters. However, its implementation is difficult for an elaborate switch mode power supply which has high efficiency and stable operation. In this paper, a power stage and a feedback controller design will be considered for proper operation, stability, and high power conversion efficiency of the high frequency LLC resonant converter. The power density can be improved by adopting high switching frequency which allows small sized passive components. At the high switching frequency, the size reduction of the passive components such as transformer, and output capacitor will be estimated to obtain the high power density design. In addition, the design method of the magnetizing inductance design method will be derived to achieve the zero voltage switching (ZVS) at the high switching frequency operation. In aspect of frequency domain, the smaller output capacitor which has small capacitance and low effective series resistance (ESR) changes the small-signal behavior of the converter’s power stage. It can make the converter unstable by increasing the crossover frequency in the loop gain of the smallsignal model. The effect of the smaller output capacitance should be analyzed for stability analysis using a proper small-signal model of the LLC resonant converter. Therefore, the proper design methods of the feedback compensator are derived to obtain sufficient phase margin in the bode plot of the converter’s loop gain for its stable operation. The design considerations of the power stage and the feedback loop will be verified with the performance comparison of 100 kHz and 500 kHz switching frequency LLC resonant converters. Since the switching performance of state-of-art power switches has been improved, the power converter can operate over a 1 MHz switching frequency. In this paper, GaN E-HEMTs are used to achieve the high switching frequency operation due to its small channel resistance and small output capacitance. However, the GaN E-HEMTs also have different switching operation characteristics to other conventional silicon-based MOSFETs. Therefore, the high speed switching characteristics of the GaN E-HEMT should be analyzed to obtain proper operation for a half-bridge type LLC resonant converter using a boostrap gate drive circuit. Moreover, a soft start algorithm for the high switching frequency is analyzed to suppress inrush currents at the cold start operation of the converter. All the design considerations using the GaN E-HEMT are verified with a 240 W prototype LLC resonant converter operating at 1 MHz switching frequency.

LINK:http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=eee4031de5dfc95effe0bdc3ef48d419

LINK: https://www.mediafire.com/file/48ryayn4gvu1ckz/file

Méthodologie de conception numérique d’un module de puissance dédié à l’automobile en vue de l’optimisation des surtensions, des pertes et des émissions conduites Hocine Dao--Thèse de doctorat de l'Université Paris-Saclay préparée à L’École Normale Supérieure de Cachan (École normale supérieure Paris-Saclay)-

 

Méthodologie de conception numérique d’un module de puissance dédié à l’automobile en vue de l’optimisation des surtensions, des pertes et des émissions conduites 

Hocine Dao

Thèse de doctorat de l'Université Paris-Saclay préparée à L’École Normale Supérieure de Cachan (École normale supérieure Paris-Saclay)

 Résumé : 

Le véhicule électrique (VE) s'inscrit actuellement dans un contexte industriel fortement corrélé aux contraintes environnementales. Un tel contexte où la minimisation des coûts est également vitale impose par conséquent des contraintes de développement et de réalisation. Les modules de puissance constituent un coût conséquent dans un système de conversion pour l'automobile. Nous nous plaçons dans le contexte des modules de puissance à IGBT en technologie silicium qui assurent les fonctions de conversion d’énergie (AC/DC ou DC/AC) pour des applications moyennes et fortes puissances. L’un des points les plus limitant de ces modules est l’aspect inductif de la maille de commutation. L’intégration de condensateurs de découplage (Ceq) au sein du module permet de réduire les effets des inductances parasites car ils offrent un chemin à basse impédance au courant commuté et augmentent la vitesse de commutation du composant. C’est cette solution que nous avons étudiée. Le but est de démontrer la faisabilité d’une telle solution couplée avec le choix optimal de la résistance de grille (Rg) des puces IGBT. Nous avons établi des règles de conception permettant la construction de modèles circuit d’un bras d’onduleur permettant l’intégration de fonction de découplage. Ce dernier nous a permis dans un premier temps de réduire les surtensions aux bornes des composants mais les pertes par commutation n’ont pas pu être améliorées significativement en comparaison à un module conventionnel. La démarche suivie pour aller plus loin a consisté à chercher un compromis entre les valeurs des condensateurs distribués dans le module et le choix des résistances de grille des puces IGBT. L’optimisation par algorithmes génétiques est la solution qui a été trouvée pour contourner les problèmes bloquants et améliorer significativement les performances du module.

LINK: https://tel.archives-ouvertes.fr/tel-01769661

LINK DIRETO: https://tel.archives-ouvertes.fr/tel-01769661/document