Babar Hussain

Impact studies of distributed generation on power quality and protection setup of an existing distribution network

The increasing amount of distributed generation (DG) in distribution networks (DNs) is giving rise to power quality and protection coordination problems. Issues like voltage regulation, flicker, harmonics and loss of coordination between circuit breaker and fuse need to be addressed for integration of DG into DN. This paper discusses these issues with a special emphasis on protection coordination problems. A typical DN with DG is modeled and simulation results for impact of DG on protection system coordination are presented and discussed here. Some solutions are proposed to cope with these problems.

An Adaptive Relaying Scheme for Fuse Saving in Distribution Networks With Distributed Generation

In some situations, utilities may try to “save” the fuse of a circuit following temporary faults by de-energizing the line with the fast operation of an upstream recloser before the fuse is damaged. This fuse-saving practice is accomplished through proper time coordination between a recloser and a fuse. However, the installation of distributed generation (DG) into distribution networks may affect this coordination due to additional fault current contributions from the distributed resources. This phenomenon of recloser-fuse miscoordination is investigated in this paper with the help of a typical network that employs fuse saving. The limitations of a recloser equipped with time and instantaneous overcurrent elements with respect to fuse savings, in the presence of DG, are discussed. An adaptive relaying strategy is proposed to ensure fuse savings in the new scenario even in the worst fault conditions. The simulation results obtained by adaptively changing relay settings in response to changing DG configurations confirm that the settings selected theoretically in accordance with the proposed strategy hold well in operation.

7. Design and Control of a Grid-Connected Interleaved Inverter

This paper is concerned with the design and control of a three-phase voltage source grid-connected interleaved inverter. This topology enables the use of low-current devices capable of switching at high frequency, which together with the ripple cancelation feature reduces the size of the output filter and the inverter considerably compared to an equivalent classical two-level voltage source inverter with an LCL output filter using high-current devices with considerably lower switching frequency. Due to its higher switching frequency and low-filter component values, the interleaved inverter also has a much higher bandwidth than the classical inverter, which improves grid voltage harmonics disturbance rejection and increases the speed of response of the inverter and its capability to ride through grid disturbance (e.g., voltage sags and swells). The paper discusses the selection of the number of channels and the filter component values of the interleaved inverter. The design of the digital control system is then discussed in detail. Simulation and practical results are presented to validate the design and demonstrate its capabilities.

Identification of Dynamic Systems & Selection of Suitable Model

Process Industry is growing very rapidly. To tackle this fast growth, current control methods need to be replaced to produce product with compatible quality & price. Normally the systems are described by suitable mathematical models. These models are replaced by actual process later on. Actually controllers are designed on behalf of suitable models to control the process effectively. So suitable models are very crucial. Different purposes demand for different types of models where the objective could be: (Bjorn Sohlberg, 2005) • Construction of controllers to control the process. • Simulation of control system to analyze the effect of changing reference • Simulate the behaviour of system during different production situations. • Supervise different parts of process which properties change due subjected to wear or changing product quality. The exact model of any system will reflect detailed description. A simple feedback controller demands a simple process description than a process description which is going to be used for supervision of wear. Often a more advanced application, demand for a more complex model. The relation between the purpose of the model and its complexity is shown below.