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Original scientific paperThis paper presents a grid-tied cascade H-bridge inverter with predictive current control technique. The proposed 15-level cascade inverter consists of three H-bridge inverters with separated DC sources. At the output of the cascade inverter an L filter is used as a grid filter. The cascade inverter is controlled by the mean of RT-Lab. The predictive current regulator and one-phase synchronous reference frame PLL are designed with help of Rapid Control Prototyping. The proposed control method uses a discrete model of the system to predict behavior of the system for each of 15 voltage levels of inverter output voltage. Verification by simulation and on a laboratory model is described.Key words: Cascade inverter, Predictive current control, RT-Lab, Synchronous frame PLL Strujno prediktivno upravljanje mrežnim H-mosnim izmjenjivačem. U ovom radu prikazan je kaskadni mrežni izmjenjivač u H-mostu sa strujnim prediktivnim upravljanjem. Predloženi 15-razinski kaskadni izmjenjivač sadrži tri H-mosna izmjenjivača s odvojenim DC izvorima. Na izlazu kaskadnog izmjenjivača dodan je induktivni mrežni filter. Kaskadni izmjenjivač upravlja se korištenjem RT-Lab programskog okruženja. Strujni prediktivni regulator i jednofazni PLL poravnat sa sinkronim koordinatnim sustavom dizajnirani su uz pomoć Rapid Control Prototyping metode. Predložena metoda upravljanja koristi diskretni model sustava za predikciju ponašanja sustava u svakom od 15 naponskih razina izlaznog napona izmjenjivača. Upravljanje je provjereno na simulacijskom modelu sustava i laboratorijskom postavu.Ključne riječi: kaskadni izmjenjivač, strujno prediktivno upravljanje, RT-Lab, PLL u sinkronom koordinatnom sustavu

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This paper presents the design procedure for the output LCL filter used in grid connected one-phase 15-level cascade voltage source inverter for photovoltaic application. Output power of a system is in kilowatt range due to one-phase connection. The filter design is based on detailed analysis as it is a multifold problem. Design is adopted for predictive current control technique with finite control set. Because of lack of modulation technique there is no detailed higher-order harmonic analysis. Key parameters that define filter performance are described. Step-by-step design of LCL filter is presented. The design procedure is done in pre-unit base so results can be used for wider range of power levels. No passive damping is considered as active damping is preferable with regard to high efficiency of photovoltaic inverter.

The paper presents a novel control technique for a phase-shifted PWM (PS-PWM) soft-switching dc-dc converter. The converter is a full bridge dc-dc converter with controlled output rectifier and an active snubber on the secondary side. To solve the problems with nonlinear nature of the dc-dc converter a fuzzy logic control is used. The fuzzy logic controller design and simulation is presented. The performance of the designed fuzzy logic controller is compared to classical PI controller.