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.

Teacher Leadership Practices and Opportunities in Pakistani Context: A Mixed Methods Study

The purpose of this study was exploring teachers' views about their practices as leaders and opportunities available to them for their leadership practices in the schools. Moreover, the study also explored the process of development of teachers as leaders in the schools of a private organization in Karachi, Pakistan. This study employed explanatory sequential mixed methods research which was completed in two phases. In the first phase, it explored teachers' practices as leaders along with the available opportunities through cross sectional survey administering questionnaires among the teachers of three schools functioning under the same organization. In the second phase, qualitative case study was employed to explore the process of teacher leadership development through conducting interviews of the school principal, primary section in-charge and four teachers selected based on certain criteria. The analysis of the quantitative data occurred in two level-main analyses followed by the additional analysis. The main analysis of teachers' views about their practices as leaders and opportunities available to them revealed that teachers performed both formal and informal leadership. As an informal leader teachers were reported to be making sure learning for all students in their classes using innovative students-centered strategies. Similarly, teachers were reported to be seeking to enhance their knowledge and skills, help colleagues in their professional development through sharing ideas and best practice and providing support to the novice teachers in the school. The school management was also reported to be encouraging teacher leadership and providing professional development opportunities to the teachers. The additional analysis revealed the existence of correlation between the available opportunities and leadership practices in the selected school. Furthermore, the qualitative case analysis revealed that teacher can be developed as leaders by providing opportunities of collaboration to the teachers parallel to the professional development opportunities. The school principal can play a fundamental role in teacher leadership development by facilitating need based intervention, providing leadership opportunities based on teachers' capacities and appreciating teacher leadership practices. However, the study findings suggest a need for the shift in the organizational structure of the school by involving teachers in decision making process and developing rules and polices related to teachers' professional development and students' learning.