Faisal Amir

A Novel Model of HVDC Hybrid-Type Superconducting Circuit Breaker and Its Performance Analysis for Limiting and Breaking DC Fault Currents

The key obstacle in integrating high-voltage direct current (HVDC) point-to-point networks into meshed multiterminal HVDC networks (MTDC) is the absence of dc circuit breakers (DCCBs), which can timely and reliably isolate the faulty HVDC network from the MTDC. In this paper, a novel hybrid-type superconducting DCCB model (SDCCB) is proposed. The SDCCB has a superconducting fault current limiter (SFCL) located in the main line, to limit the fault current until the final trip signal to the SDCCB is given. After the trip signal, insulated-gate bipolar transistor (IGBT) switches located in the main line will commutate the fault current into a parallel line, where dc current is forced to zero by combination of IGBTs and surge arresters. DC fault current behavior in MTDC and fundamental requirements of DCCB for MTDC were described, followed by an explanation of the working principles of the SDCCB. To prove the viability of the SDCCB, a simulation analysis demonstrating SDCCB current interruption performance was done for changing the intensity of dc fault current. It was observed that the passive current limiting by SFCL caused significant reduction in fault current interruption stress for SDCCB. Furthermore, fundamental design requirements for SFCL, including the effect of SFCL quenching impedance on SFCL voltage rating and energy dissipation capacity, were investigated. Finally, advantages and limitations of the SDCCB were highlighted.

Effectiveness of cyber-learning

This paper presents the technologies, infrastructure and implementation of an interactive campus as well as distance teaching techniques. Special emphasis is on third world countries where economic constraint is the major hindrance in adopting technology. The online distance learning techniques, now in use worldwide, are presented together with a summary of their evaluation. The concept of ubiquitous computing on-campus and off-campus in the future, is the motif of this paper. This concept is established by collecting real time statistical data of students, studying in different grades. The said concept involves more of the faculty contribution and setting up online and interactive lectures with the presence of mentors, providing infrastructure to support the idea with emphasis on the supremacy of off-line mentors and updated FAQs. The paper gives an overview of basic parameters and limitation of typical higher-education distance learning and teaching schemes. The benefits and limits of distance learning approach for the basic services, lessons, seminars and tutoring are discussed. Finally, a new concept of learning is discussed as to how a student can learn interactively by being a student and a teacher.

pHEMT LNA design and characterization for 4G applications

This paper presents a novel implementation of a wideband Low Noise Amplifier (LNA) for wireless communication, 4G Long Term Evolution (LTE) and wireless communication systems. Traditionally, CMOS based designs are fabricated for 4G applications. The proposed LNA design is based on a balanced configuration using ultra low noise Pseudo morphic High Electron Mobility Transistor (pHEMT) which has a fast switching response. The LNA exhibits a wideband frequency response from 1.9 to 2.4 GHz which makes it suitable for variety of wireless and mobile communication applications. The designed LNA has a NF of 0.588 dB with unconditional stability along with available gain of 12.850 dB. The LNA exhibits 20 dBm output power at 1dB gain compression and 28.5 dBm output at 3rd order intercept.

PC based Eddy Current non-destructive testing (NDT) system

A cost effective PC based Eddy Current Testing System is designed and developed to detect surface cracks in non-magnetic metals. The developed system is composed of Constant Current AC Source for excitation of the probe; and demodulation circuitry for acquisition of the signal from the crack. Eddy Current Testing Probe is also designed using the Analytical Approach. Surface cracks were successfully detected through developed system. The flaw signal is also plotted in real time on PC. Data logging feature and position sensing is also incorporated.

Hot-spot reduction and shade loss minimization in crystalline-silicon solar panels

The use of solar energy to produce electricity through photovoltaic (PV) systems has significantly increased in the past decade due to (a) reduction in solar panel costs, (b) climate concerns, and (c) advances in power electronics for grid-tied applications. In conventional rooftop PV deployments, solar panels are connected in series with bypass diode(s) across each panel to reduce the effect of shading. Shading results in hot-spots which affect both short-term (power output reduction) and long-term performance (reliability) of a PV system. This paper presents a new technique to reduce hot-spots in shaded cells along with minimizing power dissipation in an overall PV system. The proposed topology is evaluated and compared with various existing topologies with the proposed technique showing superior performance in reducing hot-spots (by 17%) along with lower losses under shading conditions.The use of solar energy to produce electricity through photovoltaic (PV) systems has significantly increased in the past decade due to (a) reduction in solar panel costs, (b) climate concerns, and (c) advances in power electronics for grid-tied applications. In conventional rooftop PV deployments, solar panels are connected in series with bypass diode(s) across each panel to reduce the effect of shading. Shading results in hot-spots which affect both short-term (power output reduction) and long-term performance (reliability) of a PV system. This paper presents a new technique to reduce hot-spots in shaded cells along with minimizing power dissipation in an overall PV system. The proposed topology is evaluated and compared with various existing topologies with the proposed technique showing superior performance in reducing hot-spots (by 17%) along with lower losses under shading conditions.