Main Topologies of Multilevel Cascade Voltage Inverters Overview

An overview of the main topologies of multi-level cascade voltage inverters was given, their main advantages and disadvantages was determined. Classification based on the type of modulation, structure of the power unit and control system was proposed. As a result of this review were identified two main control methods of the cascaded multilevel inverters, based on PWM and PWAM signal processing, three main types of topology, two types of modules structure and three methods of formation of the output load voltage waveform. Based on these data, was made a classification of the cascade multilevel voltage inverters. In more details were considered principles of constructionand the operation of schemes built on topologies based on the connection of the H-modules with the same transformation coefficients , the connection of the H-modules with the voltage sources which amplitude is determined by the steps of m , the connection of the H-modules with coefficients of transformation (voltage sources), determined by the expansion of the stepfunctions in orthogonal rows and a multi-level inverter based on the connection of the B-H type modules that has a phase transformer in the input circle.As a result of the review, the advantages and disadvantages of each of the topology and field of their application were determined.Summing up the results of the review it can be defined that the process of finding the effective circuit solution for multilevel cascade (modular) type inverters continues. This process consists of optimization of the algorithms of the control systems improvement of the utilization rate of the valves, reducing the THD rate, solving the problem of the excessive load of the valves and achievement of the maximum output power rate.Ref. 31, fig. 5