Modulation methods for multi-level inverters with flying capacitors

U radu „Modulacijske metode za višerazinske izmjenjivače s plivajućim kondenzatorima“ razmatrana su ponašanja modela izmjenjivača upravljanog impulsno širinskim modulacijskim metodama. Višerazinski pretvarači s područjem primjene na visokim snagama danas se smatraju „state-of-the-art“ tehnologijama. U radu je ponajprije prikazan povijesni pregled izmjenjivačkih topologija, dok je potom razrađena i teorijska pozadina modela višerazinskog trofaznog izmjenjivača s plivajućim kondenzatorima. Predstavljeni model modeliran je unutar Matlab/Simulink okruženja. Osim modela izmjenjivača u radu je predstavljen te modeliran i kontrolni modulacijski dio, kao i RL trošilo te DC-link napajanje za izmjenjivač. Unutar kontrolnog dijela izrađen je mehanizam upravljanja izmjenjivačem pomoću impulsno širinske modulacije. Sa stajališta modulacijskih metoda, tako su u model implementirani mehanizmi za razmatranje modulacije s vertikalno pomaknutim nosiocima (engl. Level Shifted - LS) tj. modulacija s vertikalno pomaknutim nosiocima u fazi (engl. Phase Disposition – PD) i modulacija s vertikalno i alternirajuće fazno pomaknutim nosiocima (engl. Alternate Phase Opposition Disposition - APOD) te modulacije s fazno pomaknutim nosiocima (engl. Phase Shifted - PS). Kao jedan od glavnih problema ove vrste izmjenjivačkih topologija navodi se balansiranje napona na plivajućim kondenzatorima. U radu je stoga također teorijski predstavljen te modeliran i balansni algoritam kojim se navedeni problem disbalansa ispravlja. Navedeni algoritam zasnivan je na logičkim jednadžbama. Implementirani model balansnog algoritma univerzalan je za sve razmatrane modulacijske strategije kao i za broj faza. Na kraju rada predstavljeni su dobiveni rezultati u obliku simulacijskih odziva te zaključak.Research work „Modulation methods for multilevel inverters with flying capacitors“ deals with consideration of inverter model behavior witch is controlled by pulse-width modulation techniques. In this highly active area, different converters topologies have found their applications and are considered today as the „state-of-the-art“ systems. This work covers high-power voltage-source flying capacitor inverter, including theoretical consideration and Matlab model. First, historical overview of most common inverter topologies is represented. After short historical overview, theoretical background of the flying capacitor inverters is shown and full implementation of model is presented in Matlab/Simulink software tool. Beside flying capacitor inverter, model of DC-link voltage source (on input) and RL-load (on output) are also implemented in model. At the input of the inverter model (on IGBT switches), control signal is brought from control block with pulse-width modulation generator. Pulse-width modulations methods considered in this research work are Level Shifted (LS PWM) modulations, ie. Phase Disposition (PD PWM) and Alternate Phase Disposition (APOD PWM) modulations. Also, Phase Shifted modulation is considered and implemented in control part of model. As the one of the main problem of phase level modulation techniques in cooperation with flying capacitors, voltage disbalance is named. For this reason, addition to first, second model is implemented with voltage balancing algorithm which is fully implemented using logic-form equations. Implemented balancing algorithm is universal for all considered modulations techniques in this research work, as also for any number of phases. At the and of the work, results are represented in a way of simulations and conclusion