Electrical Machines & Power Electronics
The work on electrical machines and power electronics has concentrated on the design of novel machines for power take off systems in renewable energy converters, such as direct drive wave, wind and tidal current systems. Power electronic converters are being developed for interfacing these renewable energy systems to the grid and for control to optimise the energy converted. In addition there has also been some work on electronic power
supplies, including switched mode power supplies (SMPS), resonant mode and uninterruptible power supplies (UPS). Summaries of current research projects are given below and completed
power electronics research projects can be found here
Current Research
Research Fellow TBA
Supervisor: Dr Markus Mueller
In direct drive wave, wind and marine current energy converters the electrical generator is directly coupled to the slow moving prime mover, which either rotates (wind and marine current) or reciprocates (wave). In the latter case linear generators have been developed. It has been convention to use iron-cored machines, that is a machine have iron on both the stationary and moving parts, but the magnetic field between the two results in a large undesirable magnetic attraction force, which requires a significant mechanical structure to maintain the physical airgap between the two. Removal of the iron from one component eliminates the magnetic attraction force completely. Such machines are termed "air-cored". In this project the main objective is to investigate a novel form of air-cored permanent magnet (PM) machine which makes effective use of the magnetic circuit, but without the magnetic attraction forces present in iron-cored machines. Prototype machines will be design and built to demonstrate the concept: a 20kW, 100rpm rotary machine and 3kW linear machine. Both prototypes will be tested at the University of Edinburgh. This project is funded by Scottish Enterprise under the Proof of Concept Fund.
Paul Stott
Supervisors: Dr Markus Mueller, Dr Ewen Macpherson
There is increasing interest in domestic renewable power systems, such as domestic CHP, PV, and roof mounted wind turbines. Such systems could be used to offset the power supplied by the grid, but could equally be used to generate power back into the grid. However, any power conversion or power management system would need to comply with Grid Codes laid down by the Distribution Network Operator. The system needs to be intelligent, so that it can optimise the power flows from (or to) the grid and from the small-scale energy converters. Power converters must be able to generate voltage and frequency within the current regulations for use by existing domestic and industrial loads.In this project we will focus on the development of power converters and controllers for low power wind systems connected to domestic or industrial units. In addition fully variable speed hybrid wind-diesel systems will be included in the study.
Alasdair McDonald
Supervisors: Dr Markus Mueller, Dr Ewen Macpherson
Direct drive systems offer better reliability compared to gearbox drive trains. However, because of the low speed the generators have a large outside diameter and are very heavy. There have been a number of design studies comparing different machine topologies, but in these studies only the active mass is included and the structural mass (or so-called inactive mass) required to maintain the airgap is excluded. In this project we are developing analyitcal tools for estimating the inactive mass, which will then be used in a more comprehensive comparison of electrical machine topologies for direct drive power take off systems. Modular concepts of permanent magnet machines and switched reluctance machines are also being addressed to simplify assembly and construction. This research is closely linked to the previous project on a novel air-cored permanent magnet machine.
Jonathan Shek
Supervisors: Dr Ewen Macpherson, Dr Markus Mueller
This project aims to develop control strategies for optimising the energy absorbed from a wave energy device, such as heaving buoy, using a directly coupled linear electrical generator. The energy captured by a wave energy device is a function of the frequency of the incoming waves and their amplitude. Maximum energy is captured when the incoming wave frequency matches the resonant frequency of the device, but this condition can never be guaranteed. Waves are random, and hence some form of control is required to optimise the energy captured. Phase control ensures the wave excitation force and the velocity are in phase, which is always the case at resonance. This is achieved at off resonant frequencies by applying an additional spring force by mechanical means. However, in a previous project it has been shown by simulation that a directly coupled linear electrical generator can be used to provide this additional spring force. The aim of this project is to develop control strategies for direct phase and amplitude control using a linear electrical generator. An electromechanical test rig for emulating wave energy devices has been installed in the machines lab at Edinburgh so that the system can be demonstrated.
Kostas Papastergiou (in collaboration with BAE Systems Ltd.)
Supervisors: Dr Ewen Macpherson, Dr Brian Flynn
This project aims to investigate the Contact-less Rotating Transformer as a means of transferring energy from the stationary to the rotating frame of a device. The well established slip-ring technology suffers wear, can cause unwanted arcing and is prone to damage from dirt in field conditions. Also, its performance relies on the regular maintenance checks. On the other hand, the rotating transformer provides only magnetic coupling between the moving parts. A radar application will be considered in this project where there is need for high power and low voltage energy transfer. The rotating transformer will be developed in conjunction with the Phase-Shifted Bridge Converter incorporating zero-voltage transitions. The operation of the circuit will be analyzed and modelled theoretically and a prototype will be designed. The overall efficiency will be measured and optimization of both power electronics and the transformer layout will follow.
[more...]
Kostas Papastergiou, Dr Ewen Macpherson, Dr Brian Flynn
The project aims for a high efficiency dc/dc power converter design for IT Servers and Telecommunications Equipment. The (hardware) simulation of fractional turns allows the designer to use the exact number of turns needed to regulate the output(s) of a converter without the use of post-regulation circuits. This design results in a compact transformer with high efficiency. The overall design is also simpler and has reduced manufacturing cost. The theoretical analysis is completed and the experimental evaluation of the technique is now being scheduled. [more...]
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Completed Research Projects
Descriptions of previous research projects.
Industrial Short Courses / Continuing Professional Development
IES has held approximately 10 one-week continuing education courses on the design of SMPS. These have included both open courses and courses tailored to a company's individual needs, usually held on the company premises.
An 8-hour continuing education video course on the design of SMPS has been produced (sponsored by the UK Department of Trade and Industry under the video courses in industry programme). The course notes were published by Research Studies Press, with
the second edition published in 1997.
In addition, one week courses have been held on UPS systems.
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