Research Report - 2001
Energy Systems
Academic Staff
Dr Tapan Kumar Saha
Dr Geoff Walker
Dr Zhao-Yang Dong
Dr Allan Walton
Research Staff
Emeritus Prof. Mat Darveniza
Research Students
Mr. Craig Aumuller
Mr. Justin Bray
Mr. Brad Byrne
Mr. David Finn
Mr. John Edwards
Mr. Matthew Greaves
Mr. Karl Mardira
Mr. John McDonald
Mr. Damien Sansom
Mr. Paul Sernia
Mr. Andrew Simpson
Mr Kenneth Siu
Mr. Zheng Tong Yao
Technical Staff
Mr Steve Wright
Mr Graeme Saunders
Contact Details
Dr Tapan Kumar Saha
Email: saha@csee.uq.edu.au
Tel: 3365 3962
Dr Geoff Walker
Email: walkerg@csee.uq.edu.au
Tel: 3365 3573
Dr Zhao-Yang Dong
Email: zdong@csee.uq.edu.au
Tel: 3346 9052
Dr Allan Walton
Email: walton@csee.uq.edu.au
Tel: 3365 2363
Emeritus Prof Matt Darveniza
Email: matt@csee.uq.edu.au
Tel: 3365 3775
The key areas of research in the energy systems area include:
Power systems analysis
Power systems deregulation
Reliability of electrical equipment and power quality
Power electronics
Systems engineering
The activities in electric power systems cover development and application of methods for analysis, simulation and control of integrated energy systems. This includes generation, transmission and distribution of electric energy in addition to operation and planning of electric power systems. Electricity industries in Australia and in other parts of the world are going through the process of deregulation for several years. A number of new challenges are being confronted by the electricity industry. Our research in this area includes pool price forecasting, loss allocation, nodal pricing and security assessment. The school also has expertise in the area of the analysis of the stability and control system requirements of power systems.
Reliability of power systems equipment is a topic that has been studied for many years in this school. Work in this area has recently turned to a very important problem confronting all power authorities and other industries, viz. the assessment of ageing and remaining life of the aged power system equipment (with particular attention to transformers and underground cable systems). Most modern electrical and electronic devices such as computers, process controllers and communication equipment are sensitive to power quality problems. Our research focus has been on monitoring the quality of power supply and on theoretical analysis of the impact of power quality on electrical and electronic equipment using wavelets and other signal processing tools.
Power system equipment can be made less costly and more reliable if transients in the system can be reduced or eliminated. In recent time, studies of the reliability of metal oxide arresters and search for new diagnostics are the new directions of research. These include investigation of modern electrical and innovative material characterisation techniques.
Power electronic converters can be found in all current consumer and industrial electronic equipment. Power electronics research is application oriented, finding novel solutions to problems presented in the fields of robotics, audio and servo amplification, electric and hybrid vehicles, photo-voltaic (solar) power generation, power quality, energy metering, and electrostatic precipitation.
Electric and hybrid electric vehicles (EVs, HEVs) have now been the subject of research for decades, and many of the technologies are demonstrated. Similar issues exist in the emerging fields of renewable and micro power generation using grid connected or stand alone photovoltaic, micro-turbine and fuel cell based systems. The Energy Systems group is focusing on the whole- system engineering problems of component selection, optimisation, control, integration, cost reduction and design for manufacture which will be required to achieve commercialisation of these vehicles and systems. The group draws on the experience gained through the University's Solar racing car "Sunshark", which has already demonstrated the use of composites, advanced battery and motor technologies, photo-voltaic modules, efficient power electronics, and control and telemetry systems, all of which were developed in-house.
In designing automatic voltage regulators for generators it is necessary to know the parameters of the machines. Whilst parameters can be easily found for simple generator models, the parameters for more comprehensive models can only be determined by carrying out frequency response tests. The choice of generator model to use and the extraction of the parameters from the results of frequency response tests is not straightforward. Procedures have been developed by which the order of model required for a given set of results and the parameters for that model can be obtained.
The laboratory facilities in energy systems area include (i) computer- controlled transformer condition monitoring facilities (ii) facilities for on-line monitoring of a wide variety of power quality disturbances and equipment for simulating power quality disturbances (iii) extremely well equipped insulation diagnostics laboratory, which is very actively used for insulation degradation and over-stress measurements. We joined the Queensland Electrical Testing and Research Consortium (QETRC), which offer a wide range of electrical testing and problem-solving research services. The other members of QETRC are Energex, Powerlink Queensland, Queensland University of Technology and Simtars. The school has a rotating machines laboratory equipped with computer controlled data acquisition and a power electronics laboratory equipped with machine drive control facilities to enable convenient studies of the performance of rotating machines and their controllers. Software support in power systems laboratories is very strong. These include: PSS/E, PowerWorld Simulator, ATP and other transient simulation packages.
Investigations into the Impact of Electricity System Requirements on the Design of Powerformer
Chief investigator: Dr T K Saha
For over fifty years, electricity has been produced by generators that conventionally operate at medium voltages, typically up to 25,000 volts. In 1998, ASEA-Brown Boveri (ABB), developed a new type of generator capable of producing electricity directly at transmission voltages as high as 400 kV. ABB has named the new high voltage generator the PowerformerTM. The main aim of the project is to carry out technical studies of the interaction between the Powerformer and electricity systems, with particular reference to Queensland and national systems. The project has been funded by the ARC Strategic Partnership with Industry Research and Training Scheme for 2000-2002. Collaborators: ABB Corporate Research, Sweden, Powerlink, Queensland, Tarong Energy, CS Energy, Stanwell Corporation and Alstom Power. The project has provided two APAI scholarships for two PhD students. One of the aims of this research project is to investigate the unique power system attributes of the Powerformer and to determine how the Powerformer’s parameters may be designed and chosen to assist system reliability and security, especially in the area of voltage stability. Voltage stability studies will be performed in attempt to see if and how, the Powerformer may aid in the reinforcement of voltage stability in large interconnected power system. The other main aim of this research project is to investigate how the introduction of “Powerformer will affect the performance of the whole system under fault conditions. Particular focus will be placed on accurately determining fault behaviour of the modified system to allow verification of the effectiveness of aspects such as existing network grounding methods and protective settings. The influence of the machine parameters of Powerformer on fault performance will also be explored using both analytical and stochastic techniques with the ultimate goal being the selection of optimal design characteristics for application of Powerformer in the Queensland transmission system.
Aumuller, C., Saha, T. K., “Investigating The Influence Of The Generator Step-Up Transformer On Power System Voltage Stability And Loadability”. Paper accepted for the Proceedings of the International Power Engineering Conference, to be held in 17-19 May 2001
Reliability of Aged Power Transformer
Chief investigator: Dr T K Saha, Research Fellow: Dr Abbas Zargari
We have developed a variety of modern electrical and chemical techniques to investigate the state of electrical insulation in aged power transformers. Accurate interpretation of measurement data and their usefulness for predicting remaining life are the most important questions to be resolved. Our success in this research recently led to the development of a three-year research program, supported by TransGrid, the organization responsible for bulk electricity transmission in New South Wales. We are now in progress with this collaborative research project with TransGrid. This project is jointly funded by the University and TransGrid estimated to a cost almost $750,000.
Saha, T.K., Darveniza, M., Yao, Z. T., Hill, D.J.T., Yeung, G., "Investigating the Effects of Oxidation and Thermal Degradation on Electrical and Chemical Properties of Power Transformers Insulation", IEEE Transactions on Power Delivery, Vol.14, No.4, October 1999, pp. 1359-1367.
Saha, T.K., Yao, Z. T., Le, T.T., Darveniza, M., Hill, D.J.T., “Investigation Of Interfacial Polarization Parameters For Accelerated Aged Oil-Paper Insulation Samples And Its Correlation With Molecular Weights And Furan Compounds”, Proceedings of the CIGRE 2000 Paris Session, Paper No. 15-201, Paris, France, 27 August-2 September 2000.
Theoretical Simulation of Power Quality Impact on Sensitive Electronic Equipment
Chief investigators: Dr T K Saha, Dr. Z Y Dong
Most modern electronic devices such as computers, process control and communication equipment are extremely sensitive to power supply disturbances. A considerable loss of productivity is caused by power quality problems. In 1997 a research project was funded from the University of Queensland. Research findings from this project demonstrated frequencies of power disturbances as being experienced by the customers in a selected system and type of equipment mostly affected. In this project, we aim to use available data to develop a power quality identification method based on wavelet and neural network models. Then we aim to study significant power quality problems using these methods. This study will provide a much needed comprehensive software tool for the analysis of the impact of power quality on electronic equipment and also provide practical solutions for protection of equipment against the anticipated problems.
Jun, W., Saha, T.K., “Simulation of Power Quality on a University Distribution System”, Proceedings of the IEEE 2000 Power Engineering Society Summer Meeting, 16-20 July 2000, Seattle, USA, pp 2326-2331.
Pool Price Forecasting
Chief investigators: Dr T K Saha, Prof. T Downs, Dr. Z Y Dong
Electricity industry around the world is changing from state owned and controlled monopolies to private and corporatised government participants in a competitive market. In this competitive cost driven environment both electricity producers and retailers need accurate prediction of load demand and the price of energy supply in the pool. The concept of pool price in electricity market is completely new and very little information has yet been published. Artificial neural networks (ANN) have recently been widely and successfully applied to forecasting and real-time allocation problems. We have investigated neural network models for forecasting the electricity pool price and the forecasting accuracy is not sufficient to fully satisfy industry requirements. To produce a satisfactory forecasting tool for electricity pool price other modern and challenging forecasting techniques need to be investigated. Some of the modern methods that show promise in forecasting is support vector machines, boosting learning machines, time series support vector regression and recurrent neural Networks. The objective of this study is to investigate these and other possible forecasting methods and select the best method for electricity pool price forecasting tool, which satisfies the requirements of electricity supply retailers.
Sansom, D., Saha, T.K., "Neural Networks for Forecasting Electricity Pool Price in a Deregulated Electricity Supply Industry", Proceedings of the 1999 Australasian Universities Power Engineering Conference, Darwin, Australia, September 1999,pp. 214-219.
Z. Y. Dong, B. Zhang and et al, “Adaptive Neural Network Short Term Load Forecasting with Wavelet Decompositions”, Paper No. 77, accepted by IEEE Porto PowerTech'2001, Porto, Portugal, Sep. 2001.
Electricity Market Security Assessment and Management
Chief investigator: Dr. Z Y Dong
The electric power industry restructuring and deregulation resulted in vertically integrated power companies being separated into smaller, competing and functionally separate entities, and introduced the competitive markets for electricity. Like other markets, attention shall be paid to such as market structure and rules; however, security of the electricity market shall also be considered based on its special feature defined by the characteristics of electricity. Regardless of the market model chosen, it is still essential to carefully balance the power requirements of the supply side and demand side in the presence of disturbances. It is well known that this balance is required to maintain system voltage, frequency and angle stability of the network. This project investigates methods to achieve system security via planning and management. Optimization techniques from both traditional and artificial intelligence based ones are employed for security assessment. The objective of the project to establish a security assessment and management framework, which can assist the electricity market managers in decision making aimed at maximizing their profits as well as maintaining the system security.
Z. Y. Dong, D. J. Hill and M.A.B. Zammit, "Deregulated Power System Security Assessment and Management", Proc. CIGRE 2000.
Z. Y. Dong and D. J. Hill, "Power System Reactive Planning within Electricity Market", Proc. APSCOM 2000, Hong Kong
Power Delivery in a Deregulated Environment
Chief investigator: Dr T K Saha, Prof. T Downs
The recent deregulation of the power industry has opened up new technical challenges that must be addressed in order to ensure fair and equitable market operation. Significant among these is the availability of alternative routes for the delivery of power, between and across different ownerships. In this scenario, a major challenge is to determine the minimum cost contractual arrangement for the delivery of required power. To achieve this, new techniques for the analysis of power systems are required. This research project aims to provide solutions to these analysis problems and hence to provide software to assist with market operation.
Reliability of Metal Oxide Surge Arresters
Chief investigator: Dr T K Saha
The energy systems research group has been involved in surge arrester research for over thirty years. The most recent study examined the service reliability of metal-oxide arresters, namely their capacity to function normally in service without (themselves) being the cause of faults. During this time we have conducted laboratory research into the effects of multiple pulse lightning currents and very high temporary overvoltage on metal oxide arresters and on varistor blocks. A new diagnostic technique called "return voltage measurement" was found to be sensitive to monitor the degradation process of varistor blocks. Further investigations are in progress to monitor the degradation of surge arrester blocks with this new technique under different controlled ageing conditions. Investigations are also in progress to look at changes of microstructures due to degradation of blocks with collaboration from the colleagues of mining engineering department. The Australian Research Council recently funded this project.
Mardira, K. P., Saha, T. K., Sutton, B., “The Effects of Electrical Degradation on the Microstructure of Metal Oxide Varistor”, Paper accepted for the proceedings of the 2001 Transmission and Distribution Conference, 28 October - 2 November 2001, Atlanta, Georgia USA.
Measurement of Machine Parameters using Frequency Response Methods
Chief investigator: Dr A Walton
The results of standstill frequency response (SSFR) tests are now accepted as an alternative means to the time-honoured sudden short circuit test for the determination of the parameters of synchronous machines. Whilst the sudden short circuit test can only provide information on the parameters of second order models in the direct axis, SSFR tests provide information on both the direct and quadrature axis parameters. The need for the introduction of frequency response testing is therefore three-fold; to obviate the need for the onerous sudden short circuit test, to enable parameters for the quadrature axis to be measured and to enable the parameters for higher order models to be determined. Analytical processes have been developed which are based on the characteristics of the equivalent circuits, which are then immune from the uncertainties of wholly numerical methods of analysis. The work provides time constants to enable the designers of the control systems to make suitable design decisions. Machine parameters are also produced which give the machine designers feedback on machine design features and insights into their effects on design factors. There are two distinct aspects of the work being done. Excitation systems incorporating pseudo random sequences are being designed which enable the frequency response measurements to be made most effectively. Procedures for the analysis of the results obtained are being refined and extended to take account of the different equivalent circuit models, which can be used.
Walton A, A Systematic Method for the Determination of the Parameters of Synchronous Machines from the Results of Frequency Response Tests. IEEE Transactions on Energy Conversion, Paper No PE-166-EC (12-99).
System Analysis and Integration in Hybrid Vehicle Drivetrains
Chief investigator: Dr G Walker
Hybrid vehicle drivetrain technologies account for a large and rapidly growing sector of current automotive research and development. However, numerous examples may be found where these various technological improvements have been isolated and/or applied separately, and increases in vehicle performance have been less than what might be achieved through the combined, systematic application of these technologies. This research topic intends to address this problem. Through a detailed program of hybrid drivetrain computer modelling, simulation and analysis, this research seeks to identify the combined performance potential of existing and future hybrid drivetrain technologies. The analysis will utilise a systems approach, with a focus being placed upon integration of hybrid drivetrain components in accordance with their differing performance characteristics. This research should produce a number of optimum hybrid drivetrain configuration designs, and will predict levels of optimum performance for each. It is hoped that this process can identify a number of universal guiding principles for hybrid drivetrain design that may be utilised in future hybrid vehicle development worldwide. To facilitate realistic case studies, the group plans to construct one or more working hybrid drivetrain platforms. These will allow a demonstration of the hybrid drivetrain design principles developed in the modelling and analysis phase.
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