Single-phase Single-stage Buck-boost Multilevel Inverter

Because of the significant advantages such as high output power and low harmonics,multilevel inverters have been widely used in large power occasions. While in the largepower occasions like Solar power. the input voltage varies widely with the environmentand the output voltage must be relatively stable at the same time. The existing multilevelinverter topologies can hardly meet the requirements. In order to meet the special needs, aseries of single-stage non-isolation buck-boost multilevel inverter topologies are putforward in this paper. Then the working principle and possibility of the topology areanalyzed. At last, by comparing the superiority of the topologies,an optimal topology isfound. The theory, along with the simulaition and experiments of the basic unit of theoptimal topology, namely polarity reverse buck-boost multilevel inverter are studied indetail.The basic multilevel topology is constituted by buck-boost converter, so it can realizethe capacity of both buck and boost voltage. As the energy storage components of this newtopology is big inductance, and the different circuit units share the total current by bigbalance inductors, the new topology can easily achieve autonomous current sharing.POD-PWM modulation and SVM modulation have been applied in this topology. Anbalance algorithm to improve the ability and speed of autonomous current sharing is alsopresented The correctness of the above conclusions are verified by simulation.According to theoretical analysis and the simulation results, a prototype is designedand built. The experiments on the control strategy, the ability to buck and boost voltageand the capacity of autonomous current sharing are accomplished. The experimentalresults are the same with the theoretical analysis and the simulation results, and in this way,the feasibility of the topology is verified.