Comparative analysis of switching angle calculation methods for multilevel inverters

摘要

A multilevel inverter produces an output to approximate a desired sine wave. The closeness of the output waveform to the sine wave depends on the logic applied for switching angle calculation, resulting in different switching angle calculation methods. In this paper, various switching angle calculation methods are compared based on of the parameters quantifying the quality of the output waveform. The main focus of this work is on the study of convergence of the output waveform to a smooth waveform as number of levels increases theoretically. The convergence is analytically proved and validated numerically by computing up to 201 levels. Also, a parameter quantifying the deviation of the output waveform from the sine wave is defined, and its closed form expression is derived. This parameter is strongly correlated to and computationally less expensive than the total harmonic distortion. Hence, the deviation is proposed as a better measure of the quality of the output wave form. The convergence and the deviation of the output waveform are also used as the basis of the comparison of different switching angle calculation methods. These two give a better insight into the switching angle calculation methods. The analysis presented in this paper provides a good understanding of various switching angle computation methods and helps in choosing an appropriate method for a given application.