Cascaded H-Bridges Multielvel Inverters: grid connected advanced applications

Power electronics is going to increase in the modern electrical systems. It is well known that the use of power electronics allows the management and the control of the energy flow, obtaining voltage and current waveforms suitable for electrical loads. In this scenario, multilevel power converters are finding increased attention in industry and academia as one of the promising choices of electronic conversion thanks to their features and many different application fields with high power and medium voltage. Moreover, they are fundamental in interfacing electric grid to high power renewable energy systems (i.e. PV, Wind farm, Biomass, Fuel Cell etc.). Nowadays, the research is focused on the study of new converter topologies and on the development of new modulation techniques. Notably, the development of the especially designed control strategy to reduce main problem of the grid connected systems is another interesting topic where there are many studies reported in literature. Another interesting topic is the development of the electronic systems to control the power converters. Actually, there are innovative high performance integrated programmable systems with such as microcontroller, field programmable gate array (FPGA) and digital signal processor (DSP) that allow to increase the performances of power converter systems. The purpose of this PhD thesis consists in the development of innovative control algorithms for conversion system DC/AC, based on a multilevel structure converter for grid connected applications. Main goal is to design and implement the control algorithms by means of a FPGA based prototype of control board. Moreover, part of the research was carried out in order to study and identify an innovative topology structure of multilevel converter, in all its software and hardware components, for renewable energy grid connected systems. In particular, different aspect were taken into account: simulation and experimental evaluation of the performance of a three-phase Cascaded H-Bridge inverter by means of FPGA-based control board for grid connected applications; development and experimental tests of innovative modulation techniques B-spline based as carrier signals for multilevel inverters; novel computational method for Selective Harmonic Mitigation for Five-level Cascaded H-Bridge inverters and development of Modulation Schemes and control strategy for innovative Quasi-Z-Source Cascaded H-Bridge Inverter for PV grid-connected systems.