Nine-level Cascaded H-Bridge Multilevel Inverter for Photovoltaic Sources Based on Hybrid Active Filter
Adli Ikhwan1, Tze-Zhang Ang1* and Mohamed Salem1
1School of Electrical and Electronic Engineering, Universiti Sains Malaysia (USM), Nibong Tebal, 14300, Penang, Malaysia; *Correspondence: email@example.com;
Received: 12/1/2022, First revision: 1/2/2022, Accepted: 7/2/2022, Published: 8/2/2022
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Nowadays, a multilevel inverter is one of the important devices that provides a practical approach device in power system industries because of its features which are less switching losses, lower electromagnetic interference, reduced harmonic distortion, higher DC link voltages, and improved output voltage and current waveforms. Among all existed multilevel inverter, cascaded H-bridge multilevel inverter is the most attractive because of the technology development with megawatt power level. So, the cascaded H-bridge multilevel inverter has been tested and proven as a suitable DC/AC device for medium and high power applications such as renewable energy systems, electric vehicles, and motor drive applications. In this paper, the project is focusing on the combination of a nine-level cascaded H-bridge multilevel inverter connected to photovoltaic (PV) sources and a hybrid powerfilter. This project aims to study and to analyze the results of the proposed system. Thebehaviour and the performance of the designed system have shown that the system offered330V peak output AC voltage with an efficiency of 93.96% and a 5% reduction of THD.This project will be carried out only in Matlab/Simulink software.
High power device has been employed in industrial applications in recent years due to megawatt power level for many medium and high voltage applications. Multilevel power converters are being used as an alternative solution in these applications as a result of this situation . Akagi and Nabae have introduced the basic topology of the multilevel inverter from a three-level inverter in 1981 and the converters known as multilevel inverters (MLIs) have been recoregnised as the most suitable topology for high power applications . AC voltage synthesis of the DC bus from several different voltage levels is the basis of multilevel inverter technology. More steps are applied to the synthesized output waveform, generating a staircase wave that approaches the sinusoidal wave with minimum harmonic distortion as the number of voltage levels on the DC side increases. Among all existing MLIs, cascaded H-bridge MLIs are the simplest to operate and a modular configuration. The number of voltage levels can be increased without altering the inverter’s structure by connecting additional H-bridge modules in sequence .
These inverter topologies are particularly ideal for Photovoltaic (PV) applications since different DC voltage levels can easily be provided due to the modular structure of PV arrays. This type of inverter not only achieves low power ratings but also enables the use of renewable energy sources such as photovoltaic cells can be easily interfaced with the system for a high power application . PV inverter is considered the heart of the PV system. A power inverter has to be used to interface photovoltaic modules with the electricity grid system which must perform two tasks, inject a sinusoidal current into the grid and ensure that the PV modules operate at the maximum power point (MPP) . The basic topology of PV systems using a cascaded H-bridge multilevel inverter is shown in Figure 1. A DC-DC boost converter to step up the output voltages.
Power electronic converters for high power control have drastically popular today that lead to non-linear loads in nature that draw non-sinusoidal currents from the utility, resulting in voltage distortion, unwanted currents, extra losses, and device heating in the power system. Due to these situations, various harmonic mitigation techniques have been introduced such as passive power filters (PPFs), active power filters (APFs), and hybrid power filters (HPFs) . HPFs are the combination of PPFs and APFs and they can provide an effective harmonic and reactive power compensation overcoming the technical disadvantages of the other two filters which made them the best choice. The shunt connection of HPF is used to reduce the filter bandwidth requirement of the active filter .
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