The growth in the occurrence of nonlinear and time varying loads such as computers, switched mode power supplies and television sets, variable speed drive systems and rectifiers in power networks has increased the amount of current harmonics. The result is the increase in losses, interference with power equipment and communication networks and voltage distortion beyond acceptable levels in many situations. The impact of computer loads in commercial buildings is causing particular concern and this in turn reflects into distribution and transmission networks. Therefore the need to solve this problem has led to a plethora of circuits and ideas in recent years; particularly in situations where passive-filters can not cope with the majority of nonlinear and time-varying loads.
Alternative methods including
active power filters have been introduced. The main power circuit
configuration used in active power filtering relies on the standard inverter
configuration, which however suffers from several problems. The power
electronics group at Brunel University has introduced several novel circuit
configurations (Switched capacitor circuits, lattice structures and power
regulator active filters). The design and implementation of these
circuits are being investigated in the group.
Uninterruptible Power Supply (UPS) Systems
UPS systems have gained considerable importance in systems
ranging from a few watts to megawatts. This project is aimed at solving
some of the serious limitations such as large sizes, heavy weights, poor
power factor and high level of harmonics fed into power system by UPSs.
New techniques of high-frequency link and resonant link to improve UPS
system efficiencies and to improve the power to weight ratios are being
investigated.
High-Frequency Transformers
The choice of the link frequency of power supplies depends
on a compromise between size and efficiency. The size of power supply transformers,
inductors and filter capacitors can be greatly reduced by operating them
at higher frequencies. However switching losses and iron losses increase
reducing overall circuit efficiency. This project is aimed at designing
high frequency transformers using ferrites and Amorphous materials in order
to reduce the transformer’s weight and size and also to improve its efficiency.
Artificial Neural Network Application in PWM Inverters
Research into applications of artificial neural networks
(ANNs) in optimised PWM inverters is being undertaken. This technique combines
low switching losses, successful voltage control of the fundamental component
as well as suppression of a selected set of harmonics. Among the main advantages
of this technique is that it does not require high computing power.
Applications of Fuzzy Logic Controller in Intelligent Battery Chargers
Portable consumer products such as notebook computers,
camcorders and cellular phones rely on rechargeable batteries for their
power. The popularity of these products and the fact that they are used
continuously over long periods highlights the need for safe, rapid battery
charging. This project deals with the use of the fuzzy logic controller
which can provide an adaptable battery charging algorithms.
High Efficient Photovoltaic (PV) PWM-Inverter
Small scale PV applications such as water pumping or refrigeration
systems require intelligent power conditioning hardware to adapt PV array
output to load. In this project a Photovoltaic PWM inverter system is investigated
in order to improve its overall efficiency.
Applications of CAD tools in Power Electronics
There is no doubt that computer analysis and simulation
are very important steps in the design and production of power electronic
circuits and systems. At present there exist several powerful computer
simulators for these purposes such as SPICE, SABER, ECAP, NAP, etc., among
which the best known is the SPICE simulator. Most of the above power electronic
projects are initially investigated using the full version of Pspice with
Schematics capture. The simulation are either aimed at devices/subcircuits
level or at circuits/systems level.
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Mohamed.Darwish@brunel.ac.uk