Customer-end inverter in an LVDC distribution network

An AC-based low-voltage distribution network can in some cases be replaced with a low-voltage direct current (LVDC) network. With a higher DC voltage, the transmission capacity increases compared with the AC system with the same cable cross-sectional area. The DC link feeds an inverter that converts the DC voltage to a 230 V single-phase or 400 V three-phase AC voltage. Because the three-phase voltage is not necessarily needed in most residential applications, this paper presents two single-phase inverter topologies. Inverter modulation and its suitability for this kind of an application is discussed. The inverter efficiency and its requirements are also discussed in brief, yet more precise analyses are left for future studies. The conclusion is that a half-bridge topology is not suitable for this application, and therefore, a full-bridge inverter should be used instead.reviewe

Continuous assessment with self-checking tasks

This paper discusses the applicability and benefits of self-checking tasks in continuous assessment in an electrical engineering course. The method was implemented in the first-year online graduate course of Advanced Power Electronics. The method uses a two-week cycle, where during the first week a task is accomplished on the topic of that week. The tasks include working with data from component datasheets, reading and employing application notes, calculations, and simulations. During the second week, the students self-check their tasks using a rubric provided for them and then turn in a corrected version of the task. To keep the cycle going, during the second week, a new topic is also introduced, and a new task is given. The method was assessed based on a student questionnaire and teacher experiences. The method was new to all students. One of the main findings from the questionnaire was that correcting the original task submission supported student learning more than any other form of teaching on the course. However, there were different interpretations of how this support actually worked. The study also showed that there was significant variation between different types of tasks in how the students assessed the relevance of tasks and their difficulty level. Furthermore, students found that some tasks or their outcomes were more suitable for selfchecking than others. This was confirmed by the teacher’s insights on the course

Improving Energy Expenditure Estimation in Wrist-Worn Wearables by Augmenting Heart Rate Data With Heat Flux Measurement

Wearable electronics are often used for estimating the energy expenditure of the user based on heart rate measurement. While heart rate is a good predictor of calorie consumption at high intensities, it is less precise at low intensity levels, which translates into inaccurate results when estimating daily net energy expenditure. In this study, heart rate measurement was augmented with heat flux (HF) measurement, a form of direct calorimetry. A physical exercise test on a group of 15 people showed that HF measurement can improve the accuracy of calorie consumption estimates especially during rest and low-intensity activity when used in conjunction with heart rate information and vital background parameters of the user.peerReviewe