Multilevel inverter (MLI) topologies play a crucial role in the dc–ac power conversion due to their high-quality performance and efficiency. This article aims to propose a new switched-capacitor-based boost multilevel inverter topology (SCMLI). The proposed topology consists of nine power semiconductor switches with one dc voltage source and two capacitors, capable of generating a nine-level output voltage waveform with twice voltage gain. With the addition of two switches, the proposed topology can be used for higher voltage-gain applications. Other features of the proposed topology include the self-voltage balancing of the capacitors, parallel operation of the capacitors, lower voltage stress across the switches, along with the inherent polarity changing capability. To obtain the high-quality output waveform, a selective harmonic elimination pulsewidth modulation technique is applied. In this technique, the detrimental low-order harmonics can easily be regulated and eliminated from the output voltage of MLI. The proposed topology is compared with the recently introduced SCMLI topologies considering various parameters to set the benchmark of the proposed topology. The performance of the proposed MLI is investigated through various experimental results using a laboratory prototype setup.

Single-Phase Step-Up Switched-Capacitor-Based Multilevel Inverter Topology With SHEPWM

An efficient and cost-effective power converter is a pre-requisite for the modern power applications. With the evolvement of matured medium power self-commutated switching devices, multilevel inverters (MLIs) are emerged as a promising solution for high-power medium-voltage applications. Though, MLIs are performing a promising role in industrial applications, their high device count, size, cost and control complexities have restricted their market penetration. To address the disadvantages of MLIs, researchers are continuously contributing to new generation topologies under the name of reduced switch count (RSC) MLIs. From the past decade, numerous RSC-MLIs topologies have been reported for various applications. Therefore, this paper presents a comprehensive review and classification of RSC-MLI topologies, in terms of their structure, features, limitations, suitability and selection for specific applications.

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A Survey on Reduced Switch Count Multilevel Inverters

This article presents a novel switched capacitor (SC) based (2 n  + 1)-level single-phase inverter with a reduced number of components and input dc voltage supply. This inverter is designed in a way that just one dc source is required to generate different voltage levels. The circuit consists of three major parts, i.e., front-end boost stage, active SC cell(s) in the middle, and H-bridge inverter at the end. The total number of output voltage levels is up to (2 n  + 1) levels, where n ≥ 2 is the number of switching cells, which consists of three active switches and two capacitors. Compared with conventional SC-based multilevel inverter topologies, the proposed topology features many advantages, such as low number of semiconductor devices, quasi-resonant charging of capacitors that reduce the inrush current and current stress on the devices, self-balancing of capacitor, and reduced voltage stress on the switches. Moreover, a simple sinusoidal pulsewidth modulation technique is employed here to generate the modulation signals for the proposed inverter. The operating principle is presented in detail followed by comparative analysis, thermal modeling, and design guidelines. Finally, computer simulation and laboratory test results are carried out for a five-level inverter with one SC cells as well as a seven-level inverter with two SC cells as two examples to verify the performance of the proposed (2 n  + 1)-level inverter. Measurement results show that the proposed inverter has the 96.5 ± 1% efficiency over a wide range of load with a peak efficiency of 98.56%.

Switched Capacitor Integrated (2 n + 1)-Level Step-Up Single-Phase Inverter

This paper presents a new boost inverter topology with nine level output voltage waveform using a single dc source and two switched capacitors. The capacitor voltages are self-balancing and thus is devoid of any sensors and auxiliary circuitry. The output voltage is twice higher than the input voltage, which eliminates the need for an input dc boost converter especially when the inverter is powered from a renewable source. The merits of the proposed topology in terms of the number of devices and cost are highlighted by comparing the recent and conventional inverter topologies. In addition to this, the total voltage stress of the proposed topology is lower and have a maximum efficiency of 98.25%. The operation and dynamic performance of the proposed topology have been simulated using PLECS software and are validated using an experimental setup considering a different dynamic operation.

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A Single DC Source Nine-Level Switched-Capacitor Boost Inverter Topology With Reduced Switch Count

In this brief, a new cross-connected compact switched capacitor (C3SC) cell is introduced for multilevel inverter applications. The proposed CCS cell uses four switches and two diodes for interconnecting the input dc source and floating capacitors (FCs). A nine-level inverter is derived with the proposed C2SC cell requiring only ten switches and two FCs. The proposed C3SC cell-based MLI is self-balancing and has a voltage gain of two. All the switches of the proposed topology have a maximum blocking voltage within the input dc voltage ( v $_{in}$ ) value. The operating principle is detailed, and a simple logic gate based gate pulse generation scheme is presented. Detailed simulations and experimental results obtained from an 850 W prototype with several test cases are presented to validate the operation of the proposed topology. Finally, a detailed comparative assessment is performed with other recent SCMLIs to demonstrate the merits and superiority of the proposed topology.

Cross Connected Compact Switched-Capacitor Multilevel Inverter (C 3 -SCMLI) Topology With Reduced Switch Count

This study proposes a new topology for multilevel inverters based on switched-capacitor structure. The proposed topology uses capacitor charged/discharged characteristic to boost the output voltage without employing magnetic elements. The proposed circuit configuration has fewer components, including switches, voltage sources, and capacitors comparing with the conventional similar topologies. A phase disposition pulse-width modulation method is used to enhance the output waveform quality of the proposed inverter. Nine-level and 17-level configurations are simulated. To verify the operating principle, the experimental results for a nine-level inverter topology are presented.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2017.0857

Single-phase multilevel inverter based on switched-capacitor structure

This paper proposes an online learning platform with a Vietnamese Virtual Assistant (VVA) that is utilized to help instructors in presenting lessons as well as testing and assessing learners. Currently, in online learning platforms, the lesson content is recorded in videos. In the proposed approach, the lesson content is delivered through slides (PDF format) combined with the instructor's voice and face that are synthesized from the text (TTS: Text-to-Speech and SDF: Speech-driven-Face). In addition, our approach ensures the highest quality in displaying the lesson content and allows us to edit the lesson content directly from text without recording video again as the current way.

Design of Online Learning Platform with Vietnamese Virtual Assistant

This research article highlights the potential of AI-powered chatbots in education and presents the results of using ChatGPT, a large language model, to complete the Vietnamese National High School Graduation Examination (VNHSGE). The study dataset included 30 essays in the literature test case and 1,700 multiple-choice questions designed for other subjects. The results showed that ChatGPT was able to pass the examination with an average score of 6-7, demonstrating the technology's potential to revolutionize the educational landscape. The analysis of ChatGPT performance revealed its proficiency in a range of subjects, including mathematics, English, physics, chemistry, biology, history, geography, civic education, and literature, which suggests its potential to provide effective support for learners. However, further research is needed to assess ChatGPT performance on more complex exam questions and its potential to support learners in different contexts. As technology continues to evolve and improve, we can expect to see the use of AI tools like ChatGPT become increasingly common in educational settings, ultimately enhancing the educational experience for both students and educators.

Bac Bien Ngo

Papers

Single-phase multilevel inverter based on switched-capacitor structure

Design of Online Learning Platform with Vietnamese Virtual Assistant

Can ChatGPT pass the Vietnamese National High School Graduation Examination?