• Energy Research

A Wind Diesel Hybrid System (WDHS) is an isolated power system that combines Diesel Generators (DGs) and Wind Turbines (WTGs). The WDHS has three operation modes: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The latter mode is the only one resulting in substantial savings, as the DG consumes fuel even with no load. Moreover, adding an energy storage system (ESS) can significantly reduce the start/stop cycles in the DG. The FESS is robust, immune to deep discharges and its state of charge (SOC) is simple to monitor. The WDHS considered in this article uses a friction clutch to disengage the diesel engine (DE) from the synchronous generator (SG) in WO mode. The AVR regulates the voltage amplitude and the frequency regulation results from balancing the power produced by the DG and WT with the power consumed by the load and dump load along with the FESS utilisation. The control algorithms of the different elements present in the WHDS are explained, as well as the general control. The FESS always has priority over the DL for the maximum harnessing of the wind power. Simulations assess the proposed solutions for the different operation modes in the WDHS.

In this paper, a novel concept to integrate High Voltage Direct Current (HVDC)-connected offshore wind power plants with the onshore grid is presented. The concept makes use of a holistic wind farm controller along with a fully instrumented conventional synchronous generator at the point of common coupling. In our approach, the wind farm is able to replicate the natural response of the generator to a system, even enabling the wind farm to reproduce, in a scaled up manner, a range of ancillary services without having to rely on indirect frequency measurements which are prone to noise and delays. Simulation results are presented to validate the proposed solution.

This paper presents a critical review, from a wind farm control perspective, of different methodologies in the open literature that enable wind farms to participate in ancillary service provision. Firstly, it considers the services currently provided in power systems with high levels of wind generation (specifically, Denmark, Ireland, and Great Britain), reviewing current regulatory frameworks and recommendations. Secondly, it reviews the ancillary service markets that wind farms do not currently participate in, considering the barriers to entry and discussing potential solutions using a proper control-enabled framework. Thirdly, it also considers the future perspective for wind farm participation in ancillary service provision, including a review of the body of published academic research on wind farm participation in ancillary service provision. Finally, this review concludes by suggesting where the gaps are in the academic literature, and subsequently suggests future work. Two examples are the disconnect between the mechanical and farm side approaches with power-system-based modelling, and how much wind farm modelling is very-low-fidelity-omittedkey aspects such as wake effects and component fatigue analysis.

Green hydrogen is likely to play an important role in meeting the net-zero targets of countries around the globe. One potential option for green hydrogen production is to run electrolysers directly from offshore wind turbines, with no grid connection and hence no expensive cabling to shore. In this work, an innovative proof of concept of a wind farm control methodology designed to reduce variability in wind farm active power output is presented. Smoothing the power supplied by the wind farm to the battery reduces the size and number of battery charge cycles and helps to increase battery lifetime. This work quantifies the impact of the wind farm control method on battery lifetime for wind farms of 1, 4, 9 and 16 wind turbines using suitable wind farm, battery and electrolyser models. The work presented shows that wind farm control for smoothing wind farm power output could play a critical role in reducing the levelised cost of green hydrogen produced from wind farms with no grid connection by reducing the damaging load cycles on batteries in the system. Hence, this work paves the way for the design and testing of a full implementation of the wind farm controller.

The rapid development and growth of battery storage have heightened an interest in the co-location of battery energy storage systems (BESS) with renewable energy projects which enables the stacking of multiple revenue streams while reducing connection charges of BESS. To help wind energy industries better understand the coordinated operation of BESS and wind farms and its associated profits, this paper develops a simulation model to implement a number of coordination strategies where the BESS supplies enhanced frequency response (EFR) service and enables the time shift of wind generation based on the UK perspective. The proposed model also simulates the degradation of Lithium-Ion battery and incorporates a state of charge (SOC) dependent limit on the charge rate derived from a constant current-constant voltage charging profile. In addition, a particle swarm optimisation-based battery sizing algorithm is developed here on the basis of the simulation model to determine the optimal size of the co-located BESS along with SOC-related strategy variables that maximise the net present value of the wind + BESS system at the end of the EFR contract.

This report presents the design of a rotary transformer configuration (i.e. a wireless power transfer system) capable to handle the MW power transfer requirement of the XROTOR system. The deliverable includes a detailed specification of the rotatory transformer including parameters such as operating frequencies, current density, windings area, air-gap length, and others. The efficiency is quantified using finite element simulation and numerical calculations. Furthermore, its thermal performance at rated power levels is analysed and quantified using finite element simulation. The simulation results show that high level of efficiency (around 98.5%) can be obtained with a proper design methodology and suitable compensation network for the transformer system. The second section of the report provides the design and analysis of a suitable power electronic topology for the rotary transformer to manipulate the wireless power flow at the levels of efficiency required by the XROTOR project. The analysis includes electrical operation and energy conversion losses simulation of a three-phase dual active bridge configuration suitable for high-power wireless power applications. The simulation demonstrates the suitability of the topology to drive MW level power through a rotary transformer system at efficiencies of around 98%. This efficiency is calculated via electrical and thermal analysis and simulations. Results indicate that the combined efficiency of the rotary transformer with its associated power electronic converter turned to be 96.53% for a 1MW system. The methodologies presented in this deliverable can be utilized to design multi-MW level rotary transformer system and associated power electronic drivers. The designed parameters utilize the standard DC voltage levels of commercial back-to-Back converter for wind generators. As such, the designs presented in this report can be incorporated as another energy conversion stage in the DC bus of a commercial Back-to-Back power electronic system. File will be made available once approved

Battery energy storage systems (BESSs) co-located with wind farms (WFs) can provide frequency response (FR) services to AC grids exploiting the existing connection points. The UK FR market reforms introduce the Dynamic Low High (DLH) product that is procured by 4-hourly blocks in weekly auctions. This paper develops a modelling framework to optimise the BESS size along with bidding and operating strategies of a co-location system for the DLH provision based on the UK perspective. Power flows across the system are dispatched by the designed strategies, and employed to estimate the system’s net present value which is then maximised to suggest the best BESS size, state of charge levels for the DLH delivery and WF-BESS interaction, as well as the DLH capacity and 4-hourly blocks to be bid for in weekly auctions. The optimisation results are compared between different strategies and discussed around the feasibility of co-location projects under new circumstances.