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Projects: Projects for Investigator
Reference Number	NIA_NGET0188
Title	WI-POD- Wind turbine control Interaction with Power Oscillation Damping control approaches.
Status	Completed
Energy Categories	Renewable Energy Sources(Wind Energy) 50%; Other Power and Storage Technologies(Electricity transmission and distribution) 45%; Other Power and Storage Technologies(Energy storage) 5%;
Research Types	Applied Research and Development 100%
Science and Technology Fields	ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering) 100%
UKERC Cross Cutting Characterisation	Not Cross-cutting 100%
Principal Investigator	Project Contact No email address given National Grid Electricity Transmission
Award Type	Network Innovation Allowance
Funding Source	Ofgem
Start Date	01 June 2016
End Date	01 June 2018
Duration	24 months
Total Grant Value	£350,000
Industrial Sectors	Power
Region	London
Programme	Network Innovation Allowance
Investigators	Principal Investigator	Project Contact , National Grid Electricity Transmission (100.000%)
Web Site	http://www.smarternetworks.org/project/NIA_NGET0188
Objectives	The main objective of the project is to investigate if there are unfavourable interactions between the POD power modulation actions on offshore wind turbine control performance. Should such interactions exist, this project will further detail and suggest where available suitable mitigations to these issues. A final report comprising these findings will be made available to inform further developers in meeting the requirements as recorded within their bilateral agreements. In a longer term, the developed model for wind turbine-gird interactions could be applied to explore control strategy options including their integration with HVDC and energy storage connections and their broader ranges of interaction with power systems. Successful development of an offshore wind turbine model based upon the NREL 5 MW wind turbine representation and an equivalent grid model including offshore connections. Successful integration of the above 2 models to enable simulation studies for identifications of oscillation modes. Complete sensitivity studies to assess the implications of oscillation modes under various scenarios (different structural parameters of the turbines, various turbulence/wave situations and system fault etc). Successful incorporation of a POD to the wind turbine-grid model in (2) to improve damping of power oscillation. Successful evaluation of POD’s impact on the control systems and mech. performance of offshore wind turbines. Biannual milestone progress reporting with interim and final reports delivered at the end of the 1st and 2nd year. Successful dissemination of acquired knowledge to the relevant industry sectors, including the way via the National Grid System Operability Framework (SOF) Workshop. Publication of relevant papers at leading journals and presentations at major international conferences.
Abstract	Increasing penetration of offshore wind farms Wind power has and will continue to become an important source of power generation and the proportion of global wind power capacity is expected to increase from 2. 5% in 2010 to 9. 1% by 2020 (World Wind Energy Association, World wind energy report 2010). In order to capture the highest quality wind resource, much larger wind turbines are being further deployed offshore. The UK has over 4GW offshore and 6. 7GW onshore wind capacities in 2013/14 and is projected to increase to 12. 5GW and 13. 6GW respectively by 2020 with a combined wind capacity potential of over 50GW by 2030 (National Grid, UK, "UK Future Energy Scenarios", July 2014). This is in line with the UK Government target of cutting greenhouse gas emissions by at least 80% below an agreed 1990 baseline by 2050. Uncertainties on power oscillation damping capability of offshore wind turbines As the penetration of offshore wind increases, more displacement of conventional non-low carbon synchronous generation in future years is expected, particularly during system minimum demand conditions. At these times certain boundary transfers of power-flow (eg the Anglo-Scottish transfer) is expected to remain high. The stability of these boundary flows will be largely dependent upon the control response performance of connected renewables both on and offshore. The inter-area characteristic frequency of the Anglo-Scottish transfer oscillation has known to be around 0. 5 Hz. Any oscillation near this frequency could excite the system into this mode of oscillation and the increase of system operating cost in managing this could be significant. This is one of the major reasons for the Grid Code mandatory requirements of Power System Stabilizer (PSS) on major synchronous generators. The PSS are tuned to dampen any power oscillations around 0. 2 to 3 Hz. This approach is known as Power Oscillation Damping (POD). Within the GB Grid Code under CC. A. 7. 2. 4. National Grid has the right as GBSO to specify a requirement for any generator (including offshore wind) to be fitted with a power system stabiliser if such an arrangement is required for system reasons such as POD. This is further required under cc. 6. 3. 16 c) where the offshore wind farm is connected wholly via a HVDC converter connection to the GB transmission system. These arrangements will be specified within the bilateral agreement of that connecting project. In its discussions with developers surrounding the delivery of such arrangements, National Grid has noted significant concern being expressed within some areas of the offshore wind community relating to the practical impact active power oscillation could have in inducing interaction with the mechanical frequencies of oscillation the wind farm turbines themselves, which may inhibit or invalidate such control options. To date however no detailed investigation of this potential phenomenon has been undertaken. The fundamental research questions for this project are; is there a plausible risk to wind turbines (operation life, performance, structural integrity) from interaction with PSS requirements that may be imposed by National Grid, and if so, is the risk negligible or potentially material. Risk In addition to the 0. 5 Hz characteristic frequency identified there were other modes of oscillation recently reported as potentially present in the GB system (J. Turunen, H. Renner, W. W. Hung, A. M. Carter, P. M. Ashton, L. C. Haarla, Simulated and measured inter-area mode shapes and frequencies in the electrical power system of Great Britain, IET Resilience of Trans. and Distribution Network Conf. , Sept 2015). The stability of the GB system will face more significant challenges in the coming years as more synchronous generators with well-established PSS damping capability are to be replaced by wind farms which may potentially have issues in providing full POD capability. This when coupled with the more sparsely connected generation (ie weaker electrical connections) in particular large offshore wind farms and degradation of system inertia could pose significant risks to future system stability arising from insufficient capability or flexibility to damp the range of inter-area modes present at those times. Given the future levels of penetration of offshore windfarms, there is a need to clarify the uncertainties of POD and wind turbine control interaction and seek early resolution ahead of design and control solutions being fixed by the developer community. It is also known that certain oscillation modes may not be detected at all times depending on the system configurations and operating conditions. This implies that certain oscillation modes may not be detected during the commissioning of an offshore wind farm but could be problematic in the subsequent years. This will increase system security and operational cost risks. The retrofitting of POD on offshore wind farms could also be very costly and possibly impractical if the initial design considerations associated with wind turbines operating subject to POD are not fully understood. We propose to develop an offshore wind turbine model based on the widely accepted NREL (National Renewable Energy Laboratory) offshore 5MW baseline wind turbine model (J. Jonkman, S. Butterfield, W. Musial and G. Scott, Definition of a 5-MW reference wind turbine for offshore system development, National Renewable Energy Laboratory (NREL) Report, 2009. ), which represents the current typical offshore wind turbines to investigate the impact of POD control actions on offshore wind turbine control performance. NREL is government-owned and funded through the United States Department of Energy. The NREL model has been used as a reference by researchers throughout the world to standardize baseline offshore wind turbine specifications. Our research results could easily be adapted to cover onshore wind turbines. This will include where available sensitivities to the data assumptions within the NREL model to reflect particular developer technology selections of wind turbine. The model development and simulation studies will be conducted on Matlab Simulink which could potentially be adapted by National Grid for inclusion in its processes for system stability investigations in DigSilent Power Factory. The NREL 5MW wind turbine model represents a three-bladed upwind variable-speed variable blade-pitch-to-feather-controlled turbine. It has a generator-torque controller and a collective blade pitch controller to regulate power generation. It can be simulated within the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code (5), which allows for tower bending, blade bending, nacelle yaw and rotor speed torsional oscillations etc. Full-field turbulence and stochastic inflow turbulence effects can also be simulated. We have successfully applied the NREL model (within FAST) and own-developed wind turbine model (which agrees very well with the NREL one) for various wind turbine control studies ( J. Jonkman, L. Marshall and J. Buhl, FAST user’s guide, National Renewable Energy Laboratory (NREL) Report, 2005. X. Tong, X. Zhao, and S. Zhao, Load reduction of monopile wind turbine towers using optimal tuned mass dampers, 2016. X. Zhao and G. Weiss, Well-posedness and controllability of a wind turbine tower model, IMA J. Math. Control Inf. 28 (2011). As such interactions between electrical oscillations and mechanical oscillatory behaviours whether induced upon or produced by the turbines may be considered by these models. Under this project, The NREL model will be reviewed and refined for the current application. A grid model and its interconnection with the refined NREL model will then be developed to allow simulation studies of power oscillation phenomena. An appropriate POD will be incorporated to increase the damping of such an oscillation and assess its impact on the existing wind turbine control functions, mechanical performance and tolerances. The following stages of work will be followed Develop a wind turbine model based on the NREL model to enable the study of wind turbine-grid interaction. Develop a simplified grid model with its offshore interconnections with the above wind turbine model. Integrate the turbine model in (1) with the grid model in (2); carry out model validation and verification. Conduct simulation studies to identify oscillation modes between the wind turbine and the system. Incorporate a POD to the wind turbine-grid model in (3) to increase the damping on the above oscillations. Conduct sensitivity studies using the model in (5) which contains a POD, under various scenarios (different structural parameters of the turbines, various turbulence/wave situations and system fault etc); analyse the results mainly including the impact of the POD on existing wind turbine control functions and mechanical performance.Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above
Publications	(none)
Final Report	(none)
Added to Database	17/12/18