Power Generation of Pure Sine Wave in Batteryless Solar System using Advanced Control

A novel technique for conversion of DC power to AC power is introduced using solar powered sine wave generation system is presented. DC power extracted from solar system is made utilitarian for driving the BLDC (brushless DC) motor with constant speed constraints. The back EMF signals of each phase of the BLDC motor facilitated the development of technique for the sine wave generation from solar system without battery backup. This motor is coupled with AC generator, which yields the AC power on demand. The constant speed constraint indispensable for fixed electrical frequency at the output of generator. A new control technique is rendered for reference tracking speed control of BLDC motor using Lyapunov theory by changing switching frequency, and also maintaining the voltage level at the output of converter driving BLDC by regulating the switching frequency of the zeta converter. The proposed methodology for generation of AC power from solar power system is also tested on prototype. The comparison of conventional technique for generation of sine wave power and proposed scheme is mentioned at later section of this paper for describing the efficacy of newly presented scheme.

Understanding How Selected Data Analysis Skills are Used by Grade Viii Science Students Engaged in Inquiry in Science

The demand of 21st century is to develop the learner’s potential to become critical thinkers, effective problem solvers and decision makers. This is possible when a teacher provides learning opportunities to the students to develop their data analysis skills. My study aimed to understand the data analysis skills of the science students who are engaged in inquiry in science. For this purpose, three inquiry activities were designed to teach three science concepts on the topic ‘Effects of Heat Energy”. A qualitative research design was used to respond to my research question in this study. Six student of Grade VIII from Leading Stars Private Secondary School (Pseudonym) Karachi participated in this study, among them two were girls and four were boys. The data was obtained through field notes and videos recordings. Later the data was analyzed by breaking videos into segments to find the themes and their meanings. After that video transcription of selected segments of the lesson was done by listening and writing every sentence or phrase of each individual student. Then the summary of the videotaped lesson was made. After transcribing the segments of the video and writing the summary of lessons, identified some themes that were emerged from the lessons and explained those themes in detail. The findings of my study reveal that majority of the students demonstrated analysis skills such as (identifying relevant science concepts from the activity being demonstrated, applying previously learnt concepts, identifying the procedure that is being followed and giving a reason for the phenomena at hand) well in all three inquiry activities. However, analysis skills such as (suggesting a solution for the problem at hand and articulating a conclusion) were less used in three inquiry activities and poorly developed in majority of the students. This study also indicates that students improve their analysis skills more in an interactive learning environment and the skills which are normally used by the students in their daily science classroom are found to be improved. So, it becomes very essential to improve data analysis skills of the students by employing creative teaching strategies to bring innovation in teaching and learning science.