SAgE Singapore
Scholarships
High Performance Converter for Future Offshore Windfarm
Electricity Networks
Theme: Electrical Power and Sustainability
School of EEE, Newcastle University International Singapore
School of EEE, Newcastle University, UK
School of Computing Science, Newcastle University, UK
Energy Research Institute – Nanyang Technological University, Singapore
Supervisory Team 
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Key Words
Dr Naayagi Ramasamy, School of EEE, NUIS, Singapore
http://www.ncl.ac.uk/eee/staff/profile/naayagi.ramasamy
Dr Mohamed Dahidah, School of EEE (EP Research Group), NU, UK
http://www.ncl.ac.uk/eee/staff/profile/mohamed.dahidah
Dr Mathew Forshaw, School of Computing Science, NU, UK
http://www.ncl.ac.uk/computing/people/profile/matthew.forshaw
Dr N Srikanth, Energy Research Institute, NTU, Singapore
http://erian.ntu.edu.sg/aboutus/organisation/ManagementTeam/Pages/Naras
Srikanth.aspx
The Lead Supervisor is Early Career or newly hired Staff ☒
Offshore wind energy, DC network, DC-DC converter, Centralised
controller, Dual-active bridge.
Overview
Recent environmental constraints and new secure
technologies have enforced the development of
comprehensive programs for renewable energy around the
globe. Wind energy is one of the most promising solutions;
in particular, off-shore wind energy is a key element in the
UK's vision to achieve 15% of renewable energy by 2020 and
to cut 80% of greenhouse gas emission by 2050.The electrical
collection network is an important aspect of offshore
windfarm that has created several opportunity for
improvement. Windfarms built more than 70km from the
sea shore are shifting towards HVDC transmission as losses
involved in transmitting large amounts of power via HVAC
cables become uneconomic over such distances [1]. HVDC
transmission essentially decouples a windfarm from the AC
onshore grid, removing the requirement for inter-windfarm
collection network to comply with the grid codes. Wind
speed forecasting is challenging due to its intermittent nature
[2]. Hence it is vital to model the offshore windfarms.
Offshore windfarms present several new challenges including
the electrical power system which provides the internal
collection system and the connection to the on-shore power
network. Alternatives to conventional collection networks
are being explored with the aim of increasing the power flow,
reliability and preventing increased per unit costs. The
transmission of electrical energy with DC is a promising
alternative to AC systems for future windfarm electricity
networks. The use of a DC collection network helps to
improve the efficiency and reduce component sizes in the
offshore power network. DC-DC converters can also
eliminate the large line-frequency transformer and increase
the efficiency.
This project focuses on the use of a DC collection system
for offshore windfarms, with particular emphasis of DC-DC
converter requirements and control. This work aims to
model an offshore windfarm using a DC offshore grid based
on modular high performance DC-DC converter to step up
the voltage from wind turbine clusters for onshore grid
integration through HVDC transmission cables as shown in
Figure 1(a) and (b).
(a)
Modular
DAB DC-DC
Converter
DC-AC
Converter
on Land
HVDC Cable
Transmission
design of the DC-DC converter. Intitial simulation
studies are expected at this stage to enhance and
optimize the power converter against different
operating conditions. A modular DAB DC-DC
converter that can accommodate the requirements
should then be designed. The performance of the
overall system will then be analysed and investigated
with different aspects in order to optimise its
parameters against various system changes.
3. Experimental validation
A scaled down laboratory prototype will be developed
to verify and validate the simulation and theoretical
findings. The prototype development concerns an
advanced power electronic block that is scalable to
meet different power requirements and might address
and resolve more than a single issue, with modular
design, lower cost, and improved reliability, and
durability of offshore wind energy generation systems.
4. Communication of results
The research results will be disseminated through topquality refereed journal articles and paper
presentations
in
prestigious
peer-reviewed
international conferences.
AC Grid
Shore
(b)
Fig.1 (a) & (b) Offshore generation for future electricity network
The main objectives of the proposed project are:
 To understand the characteristics and the
requirements of offshore windfarms and review the
current/developed
modular
power
electronic
converter topologies.
 To develop an efficient and modular high performance
DC-DC converter that can be suitable for future
electricity network of offshore windfarms.
 To design the proposed modular DC-DC power
converter and develop suitable control strategies.
 To demonstrate the effectiveness and the functionality
of the proposed power converter through both
simulation and experimental studies using wind
emulator.
Considering the types of generator, permanent magnet
synchronous generators (PMSG) are considered due to their
increased power density, improved reliability, higher
efficiency, and wide operating range than other types of
generators. A diode rectifier can be directly connected to
the stator of the PMSG machine thus resulting in a DC
generator. The power flow from such a generator can be
controlled by regulating the voltage of the adjoining DC
network. Parallel connection of multiple PMSG is also
possible where several turbines form a cluster, as shown in
Fig.1, and the DC voltage and power flow are controlled by
a high performance modular DC-DC converter. Dual-active
bridge (DAB) DC-DC converter is considered due to its high
power density, high efficiency, and soft-switching capability
over a wide operating range, galvanic isolation, and higher
switching frequency [3]. For a higher power system, the DCDC converter is better to be achieved by using several DAB
DC-DC modular converters in series-parallel connection
due to the power handling capability limitations of the
semiconductor technologies. The transmitted DC is
converted into suitable AC voltage using advanced multilevel
inverters for grid integration [4].
Methodology
This project proposal deals with high performance DC-DC
converter for future windfarm electricity network. This can
be achieved through the following stages:
1. Offshore windfarm technologies
Critical review of literature is necessary for exploring
offshore windfarm technologies in order to understand
the characteristics and the requirements of each type.
The proposed PhD project emulates practical offshore
windfarm systems which will assist in designing and/or
deciding on the type of the modular DC-DC power
converter and its required function.
2. Design and development of high performance
DC-DC converter for future electricity
networks
A thourogh literature review will lead to the
development requirements for the intended modular
Timeline
Year 1: Review and study the characteristics and
requirements of offshore windfarms. Explore the various
power converter topologies suitable for integration of wind
turbine clusters and devise an appropriate DC-DC
converter topology. Preliminary simulation studies are
expected at this stage.
Year 2: Develop control techniques that will facilitate the
integration of wind turbine clusters together with the DCDC converter. Investigate a key technology that provides
lower cost and modular design of the power converter to
network owners. Design and develop an efficient modular
high performance DC-DC converter that facilitates the
interconnection of wind turbine clusters with HVDC
transmission cables.
Year 3: Develop an experimental rig and evaluate the
effectiveness and functionality of the proposed converter
through experimentation using the wind turbine emulator.
Write-up of conference paper based on the obtained results.
Year 4: Analyse the measurements from the prototype
system and write-up the thesis.
Training & Skills
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The student will be based in the electrical power
research group and work in the state of the art electrical
power research laboratory within the School of Electrical
and Electronic Engineering at Newcastle University.
Skype/Teleconferencing facilities will be used for regular
supervisory meetings with NUIS and NTU Singapore.
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The student will be trained to design advanced power
converter circuits using Synopsys tools (Saber) and will
be encouraged to develop hardware skills through
prototype design and implementation.
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The student will also be encouraged to undertake various
training courses offered by the university throughout
his/her postgraduate study to develop himself/herself to
become an independent researcher. Student will be
encouraged to present his/her work in top-notch
conferences.
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The project will significantly contribute to building up of
research capacity in the field of renewable energy from
an electrical engineering perspective, both at national and
international levels.
References & Further Reading
[1] . T. Burton, N. Jenkins, D. Sharpe, E. Bossanyi, “Wind
Energy Handbook”, May 2011, Wiley.
[2] . Y. Ren, P.N. Suganthan, N. Srikanth, “A Comparative
Study of Empirical Mode Decomposition-Based ShortTerm Wind Speed Forecasting Methods”, IEEE
Transactions on Sustainable Energy, vol.6, no.1, pp. 236244, 2015.
[3] . R.T. Naayagi, A.J. Forsyth, R. Shuttleworth, “Highpower bidirectional DC-DC converter for aerospace
applications,” IEEE Transactions on Power Electronics, vol.
27, no. 11, pp. 4366-4379, November 2012.
[4] . M. S. A. Dahidah, G. Konstantinou, V. G. Agelidis, “A
Review of Multilevel Selective Harmonic Elimination
PWM:
Formulations,
Solving
Algorithms,
Implementation and Applications”, IEEE Transactions on
Power Electronics, vol. 30, no. 8, pp. 4091-4106, 2015.
Further Information
Dr Mohamed Dahidah
Lecturer
School of Electrical and Electronic Engineering
Merz court
Newcastle University
NE1 7RU
Work: +44 (0)191 208 7310
Email: mohamed.dahidah@ncl.ac.uk
Web:
http://www.ncl.ac.uk/eee/staff/profile/mohamed.dahidah