Medium Voltage Modular Multi-Level Inverter
Authors
Sandu, Cristian ; Carnu, Nicoleta ; Costea, Valentin
Term
4. term
Education
Publication year
2009
Abstract
Denne afhandling beskriver design, opbygning og styring af en trefaset modulær multiniveau-vekselretter—en effektelektronisk enhed, der omdanner jævnstrøm til vekselstrøm med fint opdelte spændingstrin. Topologien er en kaskaderet fuld H-bro, hvor identiske moduler stables for at skabe flere spændingstrin: ni niveauer for fase-fase-spændinger og fem niveauer for fase-nul-spændinger. Projektet sammenligner tre hovedmodulationsmetoder og tre under-modulationsvarianter—måder at tidsstyre koblingerne på—for at vurdere ydeevne i simulering og i en hardwareorienteret opsætning. Modulationsstrategierne implementeres både i softwaremodeller og på en FPGA (field-programmable gate array) for at vise, hvordan de omsættes til realtidsstyring. Styring og effektdelens opførsel simuleres i Matlab ved hjælp af Simulink- og PLECS-værktøjskasserne, og FPGA-koden valideres også gennem simulering. Fokus er at bygge og afprøve en fungerende vekselretterplatform, der kan bruges som grundlag for motorstyring eller nettilsluttede applikationer, med tydelige forbindelser mellem kredsløbsdesign, modulernes sammenkobling og de tilsigtede funktioner.
This thesis describes the design, construction, and control of a three-phase modular multilevel inverter—a power-electronics device that converts DC to AC with finely stepped voltage levels. We use a cascaded full H-bridge topology, which stacks identical modules to produce multiple voltage steps: nine levels for line-to-line voltages and five levels for line-to-neutral. The project compares three main modulation methods and three sub-modulation variants—ways of timing the switches—to assess performance in simulation and in a hardware-oriented setup. Modulation strategies are implemented both in software models and on an FPGA (field-programmable gate array) to show how they translate to real-time control. Control and power-stage behavior are simulated in Matlab using the Simulink and PLECS toolboxes, and the FPGA code is also validated through simulation. The emphasis is on building and testing a working inverter platform that can serve as a basis for motor drives or grid-connected applications, with clear links between the circuit design, module interconnections, and the intended functions.
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