Enhanced Trapezoidal Modulation in MMC: Comparative Analysis with Traditional Modulation Methods

HVDC transmission and renewable energy systems extensively use Modular Multilevel Converters (MMC) because they provide outstanding scalability and modular architectural features. The performance quality of MMCs depends predominantly on which modulation technique engineers implement. This work studies Nearest Level Modulation (NLM) and conventional Trapezoidal Modulation alongside an enhanced Trapezoidal Modulation method to identify the top choice for high-voltage power implementations. The main goal of this research is to optimize modulation techniques for improving MMC harmonic performance and switching efficiency. Each modulation strategy is simulated through MATLAB/Simulink-based testing under identical operating situations. Product testing indicates NLM shows lower switching losses as well as superior power distribution efficiency but the updated Trapezoidal Modulation design combines reduced THD performance with simple implementation methods. The method\u27s innovative aspect depends on the modified trapezoidal waveform synthesis from a fundamental-frequency triangular signal enabling simplified implementation as well as lower THD and avoiding the need for high switching frequencies used in conventional approaches.  The research delivers critical knowledge about MMC modulation selection which systems designers and manufacturers can use to optimize converter operation based on specific applications

Enhanced Trapezoidal Modulation in MMC: Comparative Analysis with Traditional Modulation Methods

HVDC transmission and renewable energy systems extensively use Modular Multilevel Converters (MMC) because they provide outstanding scalability and modular architectural features. The performance quality of MMCs depends predominantly on which modulation technique engineers implement. This work studies Nearest Level Modulation (NLM) and conventional Trapezoidal Modulation alongside an enhanced Trapezoidal Modulation method to identify the top choice for high-voltage power implementations. The main goal of this research is to optimize modulation techniques for improving MMC harmonic performance and switching efficiency. Each modulation strategy is simulated through MATLAB/Simulink-based testing under identical operating situations. Product testing indicates NLM shows lower switching losses as well as superior power distribution efficiency but the updated Trapezoidal Modulation design combines reduced THD performance with simple implementation methods. The method\u27s innovative aspect depends on the modified trapezoidal waveform synthesis from a fundamental-frequency triangular signal enabling simplified implementation as well as lower THD and avoiding the need for high switching frequencies used in conventional approaches.  The research delivers critical knowledge about MMC modulation selection which systems designers and manufacturers can use to optimize converter operation based on specific applications

Assessing the Efficacy of AI-Driven Corrective Feedback via WhatsApp Application to Improve ESL Learners’ Writing Skills: An Experimental Study

Writing in English poses challenges due to the intricacy of its grammatical rules; however, these challenges may be effectively overcome through artificial intelligence (AI)-driven technologies. As there is insufficient research on AI-enabled WhatsApp for English language learning and instruction, this study examines how WhatsApp’s AI system enhances ESL learners’ writing skills. To deal with these gaps, the study aims to assess how AI-driven corrective feedback through the WhatsApp application enhances ESL learners’ writing skills by reducing grammatical errors within the framework of the interactionist theory of second language learning. The present research study utilized a quasi-experimental design involving two groups—an experimental group and a control group—to experiment. The experimental group was subjected to treatment involving AI-driven corrective feedback via WhatsApp application, whereas the control group did not receive such feedback. Data were collected from 112 undergraduate participants in India at two intervals: a pre-test and a post-test. The participants’ written submissions were assessed and scored using ChatGPT 4.0. The method of statistical analysis, repeated measures analysis of variance (RM-ANOVA), was applied to analyze the score. The results of the study showed that ESL learners who received AI-driven corrective feedback via WhatsApp performed better than those who received traditional feedback, particularly in correcting complex grammatical errors related to subject-verb agreement errors, tense errors, pronoun errors, fragment errors run-on sentences, comma splices, misplaced modifiers, apostrophe errors, capitalization errors, word choice errors/lexical errors, and preposition errors in their writing. The study found that augmented feedback systems and AI-driven corrective comments in ESL classrooms could enhance writing skills

Effect of Shorting Wall on Compact 2×4 MSA Array Using Artificial Neural Network

In this paper, a compact 2×4 microstrip antenna (MSA) array is presented and the effect of inserting shorting wall is optimized with the help of artificial neural network (ANN). An ANN model has been developed for predicting the resonant frequencies with the variation of the height of substrate and shorting wall position. For validation of ANN output, a prototype of 2×4 MSA array is physically fabricated and tested. This validation verifies the proposed antenna for which simulated and ANN results are approximately similar. DOI: http://dx.doi.org/10.11591/telkomnika.v13i3.708

Co-occurrence of sleeping difficulties with urbanization and food choice in female university students.

Introduction: Sleep is a basic and essential need of human beings, large number of sleep related problems are demonstrated in all age groups with different pro-moting factor( s), these may be biological, social, economical or environmental. Literature is scanty to identify co factors of sleep disturbances in apparently healthy females.Objective: To analyze association of sleep disorders in females with rural/ urban settings of living and certain dietary habits.Methodology: A cross sectional /survey-based study was performed in University of Sindh Jamshoro. The sample size (n) was 520.The data comprised of females aged between 18 -26 years. Pittsburgh Sleep Quality Index (PSQI) was employed to assess sleep quality among the participants along with self-structured question-naire which was used for other variables such as consumption of junk food and its frequency of intake and breakfast intake.Results: Out of 520 participants, 310 (60%) were living in urban areas shows com-paratively higher frequency of poor sleep (n=262,50.5%; p=0.01-odd ratio=2.18) than those who were living in rural setups. Poor sleep was also observed in junk food eaters (n=304, 58%) however no association was observed in pattern of breakfast with sleep.Conclusion: The study concluded the prevalence of poor sleep was found more in urban female dwellers.Keywords: sleep, rural, urban, junk food, breakfast, Pittsburgh Sleep Quality Index (PSQI)

Control and Protection of MMC-Based HVDC Systems: A Review

The voltage source converter (VSC) based HVDC (high voltage direct current system) offers the possibility to integrate other renewable energy sources (RES) into the electrical grid, and allows power flow reversal capability. These appealing features of VSC technology led to the further development of multi-terminal direct current (MTDC) systems. MTDC grids provide the possibility of interconnection between conventional power systems and other large-scale offshore sources like wind and solar systems. The modular multilevel converter (MMC) has become a popular technology in the development of the VSC-MTDC system due to its salient features such as modularity and scalability. Although, the employment of MMC converter in the MTDC system improves the overall system performance. However, there are some technical challenges related to its operation, control, modeling and protection that need to be addressed. This paper mainly provides a comprehensive review and investigation of the control and protection of the MMC-based MTDC system. In addition, the issues and challenges associated with the development of the MMC-MTDC system have been discussed in this paper. It majorly covers the control schemes that provide the AC system support and state-of-the-art relaying algorithm/ dc fault detection and location algorithms. Different types of dc fault detection and location algorithms presented in the literature have been reviewed, such as local measurement-based, communication-based, traveling wave-based and artificial intelligence-based. Characteristics of the protection techniques are compared and analyzed in terms of various scenarios such as implementation in CBs, system configuration, selectivity, and robustness. Finally, future challenges and issues regarding the development of the MTDC system have been discussed in detail

Assessment of Parents’ Perceptions of Childhood Immunization: A Cross-Sectional Study from Pakistan

Immunization is one of the most cost-effective public health interventions, with considerable impacts on people’s health. Parents’ perception of their knowledge, attitude, and satisfaction is an important factor, as they may be targeted by interventions for better immunization coverage. Therefore, this study aimed to assess parents’ perceptions in terms of their knowledge, attitude, and satisfaction of the immunization of their children aged less than two years of age, in two cities of Pakistan. A descriptive cross-sectional study was conducted in the vicinity of Rawalpindi and Islamabad from March to August 2019. A semi-structured questionnaire was used for the data collection on a convenient sample of parents. The questionnaire was hand-delivered to the parents by data collectors. Descriptive and inferential statistics were used for data analysis via SPSS version 22. A total of n = 382 respondents were included in the data analysis. Statistically significant differences were found between the parents’ knowledge scores and their education levels and monthly incomes (p < 0.05). Parents with master’s education degrees and low monthly incomes had significantly better knowledge (p < 0.05). Additionally, 96.85% of the respondents believed that child immunization was important. In addition, more than half of the respondents (57.58%) thought that the affordability of vaccines was a principal factor for delays in immunization. Although the parents’ knowledge regarding the immunization of their children was not adequate, they had positive perceptions toward it