Varying the energisation condition to mitigate sympathetic inrush current

Transformers are generally easy to access and can contribute significantly to entire power system. When a transformer is turned on for the first time, it produces a magnetising inrush current which acts as a starting current. Energisation of transformer has a substantial impact on inrush current and transformer that are connected in parallel. Sympathetic inrush current is a phenomenon that appears when a transformer is switched-on in network whereas the other transformers that was earlier energised. Besides, when sympathetic inrush phenomena occur, the peak and period fluctuate significantly. In this paper, the transformers will be energised in three different ways and each condition will be explored in depth. The operation time of the transformer’s energisation whether it is energised simultaneously or at different times are tested and analysed in terms of their characteristics. It is performed using power system computer aided design (PSCAD) software, starting with a develop model of the energisation and then generate the outcomes. The results of the simulation demonstrate that energising the transformer in different ways can give different effect on the sympathetic inrush current, as well as the variables that affect it and methods for reducing it

Efficiency Improvement Techniques for Isolated Flyback and Forward Bidirectional DC-DC Converters

The information age introduced myriad means for individuals and organisations to stay connected and feel informed. Among those means, email arose as one of the most successful and ubiquitous communication technologies to be enabled via internet access. Today it continues to grow in both the volume of traffic and users each year. We now know that this has resulted in an overabundance of information, which is proving difficult for people to mentally process and productively manage. This is known as “Information overload” and email’s part in this has been termed “email overload”. Among this surplus of communication, important time-related information (temporal information) can easily become buried. This makes information recognition and retrieval an issue and it can cause late appointments, incomplete tasks and missed deadlines, the result of which is increasing stress and cognitive burden. Email applications and related technologies struggle to provide their users with adequate means for identifying and managing temporal information, which arrives embedded within email messages. Despite the sequential nature of time and task obligations received in email messages, email applications offer little to no native support for organising temporal information. It is assumed that users will utilise calendar and task-list applications to manage their time instead. In this research we conducted seven mixed method studies ranging from interviews through to A/B testing to understand the obstacles and opportunities that exist in facilitating temporal information management in email. Among our findings, we observed that the reliance on calendaring was creating distraction, dissuasion and a flawed mental representation of time. We combined our initial results with our background readings to devise solutions to these problems. We tested these solutions by creating a series of increasing-fidelity prototypes that were evaluated by users. The results informed the recommendations we arrived at for improving temporal information awareness and management in email and similar technologies. As a result of conducting a prolonged research project utilising the Research Through Design (RTD) framework, we also contribute a synthesised model of the Design process that articulates lateral thinking by Designers. Finally we contribute a functional prototype that demonstrates the phenomenological advantage in applied research methodologies. In doing so we contribute further knowledge and offer practical recommendations for the Design of temporal information in User Interfaces. We also further discourse on the diverse mental faculties employed during an iterative Design process and the value of prototypes as a conduit for Design knowledge generation

Mathematical Derivation of Switching Angles of Multilevel Voltage Source Inverter based on Alternative Phase Opposition Disposition (APOD)

Modular structured multilevel inverter is very useful for electrical application especially in high voltage and high power applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a newmathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM) by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Alternative Phase opposition disposition (APOD). A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result

Mathematical Derivation of Switching Angles of Multilevel Voltage Source Inverter based on Alternative Phase Opposition Disposition (APOD)

Modular structured multilevel inverter is very useful for electrical application especially in high voltage and high power applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a newmathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM) by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Alternative Phase opposition disposition (APOD). A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result