An analysis of the method for ensuring the sinusoidality of the output voltage in power generation systems with self-commutated voltage inverters under the requirements of the international standard IEEE-519 is presented.
In a number of programs, especially low-power generation systems, a low-cost solution is needed to provide the sinusoidal waveform of the output voltage with the total harmonic distortion of 5 %. This solution is to use two-level voltage inverters with an output sine LC filter. However, the feature of the sine filter with the frequency converter is that the PWM frequency affects the spectrum of higher harmonics of the output voltage. In addition, there is the starting current of the filter capacitor, which can disable the power switches of the voltage inverter.
The developed method for calculating the values of the LC filter with the two-level voltage inverter in the PWM mode is presented meeting the requirements of the international standard IEEE-519, taking into account the modulation frequency and limitation of the starting current of the filter capacitor.
To confirm the required quality of the output voltage of the two-level voltage inverter with the sine filter, an appropriate simulation model was created in the Matlab/Simulink computer simulation environment. The oscillograms and harmonic analysis of the input and output voltages of the sine filter, which showed the total harmonic distortion of 1.88 %, are presented.
A physical prototype of the investigated system was created on the basis of a 5.5 kW OVEN PChV203-5K5-V frequency converter (Ukraine). Using the SIGLENT SDS1104X-E oscilloscope (China), the real waveform and the results of the harmonic analysis of the sine filter output voltage, confirming the implementation of the necessary sinusoidality criteria, were obtained

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A method for calculating the parameters of the sine filter of the frequency converter, taking into account the criterion of starting current limitation and pulse-width modulation frequency

Due to multilevel inverters' diverse applications in many contexts such as electric vehicles as well as motor drives, a wide output voltage range with low total harmonic distortion is significantly important. There are different methods to reduce harmonic distortion, like selective harmonic elimination (SHE). In this method, by some evolutionary algorithms, the low-order harmonics can be eliminated or minimized. However, in a low modulation index (for example 0.1 to 0.5), the mentioned harmonics have a considerable amplitude and are not eliminated, which increases the harmonic distortion in the output voltage and current. In order to solve the mentioned problem, a method is proposed in this paper. The proposed method is based on reducing the dc-link voltage of the cascaded H-bridge (CHB) multilevel inverter when a low output voltage is required. Therefore, even when the output voltage is low, the modulation index will be high enough which leads to a decrease in the harmonic distortion. The proposed method is examined on a PSO-based SHE-PWM seven-level CHB inverter using simulation in MATLAB software. The results indicate a considerable improvement of the output waveform quality in the case of low output voltage values.

Selective Harmonic Elimination PWM for Cascaded H-bridge Multilevel Inverter with Wide Output Voltage Range Using PSO Algorithm

In this paper, a brief review of the multilevel inverter (MLI) topologies is presented. The two-level Voltage Source Inverter (VSI) requires a suitable filter to produce sinusoidal output waveforms. The high-frequency switching and the PWM method are used to create output waveforms with the least amount of ripples. Due to the switching losses, the traditional two-level inverter has some restrictions when running at high frequencies. For addressing this problem, multilevel inverters (MLI) with lower switching frequencies and reduced total harmonic distortion (THD) are employed, eliminating the requirement for filters and bulky transformers. Furthermore, improved performance at the high switching frequency, higher power quality (near to pure sinusoidal), and fewer switching losses are just a few of the benefits of MLI inverters. However, each switch has to have its own gate driver for implementing MLI, which adds to the system's complexity. Therefore, reducing the number of switches of MLI is necessary. This paper presents a review of some of the different current topologies using a lower number of switches. Doi: 10.28991/ESJ-2022-06-01-014 Full Text: PDF

https://www.ijournalse.org/index.php/ESJ/article/download/731/pdf

A Review on Multilevel Inverter Topologies

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.

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

Multilevel inverter technology has been known recently in renewable and industrial applications for high-power and high-voltage energy control. Basically, an inverter is an electronic device that converts a direct current (DC) to alternating current (AC) but not suitable for high voltage and high power application. There are a few types of multilevel inverter (MLI) such as a cascaded H-bridge multilevel inverter, a capacitor clamped multilevel inverter and a diode clamped multilevel inverter. The purpose of the project is to study a single phase cascaded H-bridge multilevel inverter. By using MOSFET as the switching component and using pulse width modulation (PWM) control method to produce the desired output that is 5-level output. The coding control and simulation is done by using MATLAB. Multilevel inverter are widely used in, photovoltaic and others renewable energy.

Single-phase cascaded h-bridge multilevel inverter

In the recent years the multilevel inverters were widely discussed topic for researchers. Because of few merits of having good power quality. Basically inverter is a converter, which is capable in converting the DC power into AC power at desired level. The two level output, zero or positive or negative V dc can be obtained by voltage source inverter(VSI). The multilevel inverter is capable to produce sinusoidal output voltage and to reduce Total Harmonic Distortion at desired voltage level. As we increase the level of voltage, the output power quality gets improved, i.e. THD gets reduced. This paper proposes the implementation and analysis of cascaded multilevel inverter with reduce THD. The implemented Cascaded H-bridge Multilevel Inverter topology is a practical topology; it provides the generalized path to increase the level of multilevel inverter as we want. In the represented model of eleven level single phase Cascaded H-bridge Multilevel Inverter has been designed using IGBT in order to generate the different output voltage levels at proper intervals, the conduction angle of IGBTs have been controlled by varying the pulse width of getting signals. Simulation models is developed in MATLAB-SIMULINK of eleven levels inverters and THD analysis is performed.

Shivam Maurya

Papers

An Efficient Technique to reduce Total Harmonics Distortion in Cascaded H- Bridge Multilevel Inverter