arXiv subjects

Milad Sadoughi

Publications and source records attributed to Milad Sadoughi.

3 recordsLinked to original sources

arXiv2021

Selective Harmonic Elimination in a Cascaded H-Bridge Multilevel Inverter fed by High-Frequency Isolated DC-DC Converter

In recent years, the use of multilevel inverter has become popular due to its many advantages. Due to the popularity of multilevel inverters in industries and in applications that require a wide range of voltages, there have been many challenges to achieve high-quality voltage. Many pieces of research have been done to solve the problem of annoying harmonics in multilevel inverters. In this study, pulse width modulation (PWM) has been proposed as a switching method. Using the Selective Harmonic Elimination (SHE) technique, the inverter switching can be carried out in low frequency, and also, this method can reduce the annoying harmonics significantly. However, in the lower modulation index, eliminating such harmonics is challenging, resulting in a considerable increase in output voltage distortion. This study suggests a way to solve the problem. In this research, eliminating selected harmonics in a multilevel inverter with variable DC links is proposed. The DC-link variable method in this study is to use a high-frequency isolated DC-DC converter. The proposed method is verified on a 5-level Cascaded H-Bridge (CHB) inverter using the SHE-PWM method solved by particle swarm optimization (PSO) algorithm.

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arXiv2021

Reducing Harmonic Distortion in a 5-Level Cascaded H-bridge Inverter Fed by a 12-Pulse Thyristor Rectifier

This paper investigates a multilevel inverter with a capability that produces a wide voltage range with high quality. The selective harmonic elimination (SHE) method is considered for a single-phase 5-level cascaded H-bridge (CHB) inverter, in which the particle swarm optimization (PSO) algorithm solves the nonlinear equations. However, eliminating the low-order harmonics has been challenging when a low range of output voltage is required. To surmount such challenges and access to a wide range of output voltage, an adjustable dc-link is introduced that allows the inverter to increase the modulation index, resulting in a significant decrease in total harmonic distortion (THD). In this paper, to regulate the dc-link voltage amount, a 12-pulse rectifier is employed to allow the inverter to produce the output voltage requirements with less distortion. To prove such claims, the PSO algorithm is modified to calculate the optimal angles, as a result, the switching angles are applied in SIMULINK MATLAB to generate a 5-level output voltage.

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arXiv2021

Staircase Selective Harmonic Elimination in Multilevel Inverters to Achieve Wide Output Voltage Range

Multilevel inverters (MLIs) are popular because of their advantages such as improved output voltage quality, lower switching losses, low EMI, and ability to handle higher voltage and power levels. To generate the desired output voltage in the MLIs, there are different switching methods including multicarrier pulse-width modulation (PWM), selective harmonic elimination (SHE), and multilevel space-vector PWM (SVPWM) methods. The SHE method minimizes the number of switching and hence the switching losses. Also, the method eliminates or attenuates specified low-order harmonics and adjusts the fundamental output voltage to the desired value. However, problems arise in the low modulation indexes where the harmonic distortion of the output voltage increases considerably. To solve the problem, this paper proposes a method to adjust the DC voltage when the low output voltage is required. Therefore, the modulation index will increase and the output voltage quality will be improved. The proposed method is verified on a 7-level Cascaded H-Bridge (CHB) inverter using the SHE method solved by particle swarm optimization (PSO) algorithm.

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