Influence of voltage levels and angles of the multilevel inverter level switching on the structure of its output voltage spectrum

Multilevel voltage inverters are currently widely used in various power systems, as they are an efficient method to form the output voltage harmonic composition. The implemented multilevel concept allows controlling the composition and magnitude of output harmonics, which is relevant for the power supply systems feeding technological processes, quality-sensitive to the spectrum of the supply voltage. The paper proposes an approach to determine the influence of parameter changes in a multilevel inverter on the spectrum of its output voltage. It allows solving the problem of synthesizing of a multilevel curve with the desired harmonic composition. The authors obtain the formulas instrumental to calculate the sensitivity of harmonic voltage components coefficients and the total coefficient of harmonic voltage components to changes in input voltage levels and electrical angles of their switching in the inverter. The paper presents an algorithm, developed to synthesize a multilevel output voltage curve with a given harmonic composition that is most appropriates for the realized technological process. The results of computer simulation of the synthesis of a multilevel curve with the desired harmonic composition due to changes in voltage levels at various values of selected harmonics show its universality, clarity and information content. The presented approach to the design of the considered type of converting devices significantly expands the functionality of multilevel voltage inverters, which contributes to their application in modern industrial technologies, the quality of which is largely determined by the supply voltage spectrum, for example, in systems of multi-frequency induction heating.