The group focuses on the following main activities:
High energy efficiency converters for applications in DC distribution systems. DC distribution systems have been proposed for use in a number of applications that include but not limited to the following: electric vehicles, renewable energy systems,distributed generation systems, naval ships and aircrafts. They have a number of advantages to offer over AC distribution systems but there are also challenges that still need to be overcome.
High energy efficiency converters for electronic lighting systems. Lighting loads consume close to 20% of all the electrical power generated. Until recently, lighting systems made use of either incadescent lamps or fluorescent lamps employing magnetic ballasts. However, these lighting systems have a high energy consumption for a given level of light output. Recent advances in technology have seen compact fluorescent lamps employing electronic ballasts replace both incadescent and fluorescent lamps with magnetic ballasts, with very significant reduction in power demand for a given level of light output. Further reductions in lighting system's power demand will be achieved with the adoption of LED lighting systems. Design of energy efficient converters for LED lighting systems will go a long way in making this possible.
High energy efficiency converters for renewable energy applications. Concerns over harmful emissions from power stations using fossil fuels have seen a growing interest in the development of alternative non-polluting enery sources. Chief among these have been renewable energy sources that include PV Solar and wind. However, due to their intermittent nature, it is almost always necessary to employ some form of power electronic interfaces between them and the loads or the AC grid. For maximum utilisation of these resources, it is important to employ interfaces with high energy efficiency.
Loss and thermal modelling in converters and electric drive systems. In order to improve thermal management in converters and motors, it is important to understand the loss mechanisms present in both motors and converters. There is a need to investigate the influence of converter switching schemes on losses in both converters and motors.
Modelling of EMI noise generation and propagation in converters. Switchmode converters have been known to generate electromagnetic noise that in some cases interferes with the operation of the converters themselves or other sensitive equipment. It is therefore important to understand how the noise is generated and also propgation mechanisms as this crucial in devising ways and means of minimising noise generation and propagation.
Converting existing HVAC lines into HVDC transmission lines. HVDC transmission systems are suited for electric power transmission over long distances as they do not suffer from stability problems associated with AC transmission systems. Studies have also shown that it is possible to improve the stability of an AC transmission line by connecting it in parallel with a HVDC line. However, not many studies have been carried out to determine the viability of converting some of the existing HVAC lines to DC.
Active Rectifiers. These are used as front-end converters in applications that include wind energy generation, electronic lighting systems, battery chargers and interfacing inverters to the AC grid. Passive diode rectifiers tend to inject high levels of low-order harmonics into the grid contributing to the deterioration of power quality. In wind generators operating with wide speed range, active rectifiers capable of operating with wide voltage range and still meeting output voltage and power factor requirement are called for.
RESEARCH GROUP PROFILE
Group Head- Prof. MN Gitau
PhD Research Students
Inus Grobler (EMI Modelling in DC-DC Converters)
MEng Research Students
CL Kala Konga (Quasi Z-Source Rectifier Modelling and Control)
F Mwaniki (High Energy Efficiency Small Photovoltaic Array with High Gain Boost and Reactive Power Control)
AA Sayyid (High Energy Efficiency High Power LED Driver)
POSTGRADUATE MODULES PRESENTED BY THE GROUP
EED780 POWER ELECTRONICS
ETE780 ELECTRIC DRIVES
INTERNATIONAL RESEARCH COLLABORATION
PUBLICATIONS
MN Gitau,”Compact Energy Efficient Switched-Capacitor Multilevel DC-DC Converters for Interfacing DC-Buses with Separate Ground,” to be presented at the IEEE IECON 2011 Conference, Melbourne, Australia, 7-10th November, 2011.
MN Gitau and CL Kala-Konga,”Compact Energy Efficient Switched-Capacitor Multilevel DC-DC Converters for Interfacing DC-Buses with Common Ground,” IEEE ISIE 2011 Conference Proceedings, Gdansk, Poland, 27-30th June, 2011, pp 1845-1850
MN Gitau and G Ebersohn,”Effects of Charging Algorithm and Converter Topology on Energy Efficiency,” IEEE AFRICON 2009 Conference Proceedings, Nairobi, Kenya, 23-25th September, 2009,
MN Gitau G Ebersohn and JG Kettleborough,”Power Processor for Interfacing Battery Storage to a 725 V DC-Bus,” Energy Conversion and Management Journal, Vol 48, Issue 3, March 2007, pp 871-881
RESEARCH FUNDING
The group receives some financial support from the Energy Efficiency Hub in the Department of Electrical, Electronics and Computer Engineering, University of Pretoria to support students pursuing postgraduate studies. In 2010 and 2011, the group had three MEng bursaries from the Hub.
The research group focuses on quality of supply, power generation and system
operation. With the increasing demand for power in South Africa, utilities are
running at close to their capacity on its networks. As a result, it becomes
more difficult to manage the networks based on standard methods. This group
develops expertise in these fields where students can understand the network
and propose solutions to existing problems.
Naidoo R.M, Visser J, Pillay P, “An adaptive method of symmetrical component estimation”, in review, IEEE Transactions on Power Delivery, TPWRD-00744-2009
Naidoo R.M, Dlamini V, Manyage M, “A non-intrusive method for estimating motor efficiency using vibration signature analysis” in review, International Journal of Electrical Power and Energy Systems
Leuschner F.W, Naidoo R.M, Practical wiring training for power engineering students, 3rd African Regional Conference on Engineering Education (ARCEE 2006), Pretoria, September 26-27, 2006
Naidoo R.M, Barendse P, Douglas H, Pillay P, A new algorithm for improved dip/sag detection with application to improved performance of wind turbine generators, IEEE IAS 2006 Annual Meeting, Tampa Florida, October 8-12, 2006
Grobler M, Naidoo R.M, Determining Transmission Line Parameters from GPS Time-Stamped Data, IEEE IECON, Paris, November 2006
Naidoo R.M, Pillay P, An online method of extracting single-event sag indices, IEEE PES Africa 2007, Johannesburg, South Africa, July 16-20, 2007
Smit P, Naidoo R.M, A generation reserve optimization model incorporating demand market participation, IEEE PES Africa 2007, Johannesburg, South Africa, July 16-20, 2007
Kala Konga L, Naidoo R.M, A design model for a fuel cell compression system, Industrial and Commercial Use of Energy Conference (ICUE 2009), Cape Town, June 10-12, 2009
Dlamini V, Manyage M, Naidoo R.M, A Non-Intrusive Compensated Slip Method for Motor Efficiency Estimation using Vibration Signature Analysis, accepted for publication, IEEE Africon, September 13-15, 2011
Naidoo R, Naidoo R, Multi-Period Co-optimisation of Energy and Reserves using an Optimal Power Flow Formulation, accepted for presentation, IASTED International Conference on Power and Energy Systems, which will be held Apr 02, 2012 to Apr 04, 2012, in Phuket, Thailand
