Comparative analysis of switching angle calculation methods for multilevel inverters

Abstract

Summary 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.

Harmonics Minimization of Symmetric Five-Level Inverter Using Improved LSF Modulation Scheme

“…It is favorable for low-power applications where power quality is more important than converter efficiency. For medium-voltage and high-power applications, low switching frequency techniques are preferred to minimize thermal stress on switches due to large switching losses [9], [10]. But low switching frequency produces output voltage or current of higher distortion [11].…”

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“…This research paper compares three, five and thirteen level MLIs using the Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) switching technique. SHE-PWM is a modulation technique that switches at low frequency and provides tailored control of low-order harmonics and reduces switching losses [24], [25], [26], [27], [28]. In each case, MLIs will use SHE-PWM control scheme and the output voltage waveform of each has six notch angles (using quarter waveform symmetry).…”

An Improved Artificial Neural Network-Based Approach for Total Harmonic Distortion Reduction in Cascaded H-Bridge Multilevel Inverters

“…In order to reduce the THD levels the switching angles are adjusted. Most common switching angle calculation methods are equal phase (EP), half equal phase (EHP), half height (HH), and feed forward (FF) [32]. None of these methods guarantees the lowest THD levels hence we need the optimization techniques.…”