Hybrid Auxiliary Power Supply System for Offshore Wind Farm

Abstract

Diesel Generators (DG) are commonly adopted to supply the critical auxiliary loads for Offshore Wind Farm (OWF) during islanding operation. To reduce fuel consumption, avoid over-sizing of DG, and further enable a smooth resynchronization to main grid, a hybrid Auxiliary Power Supply (APS) system is designed with a combination of DGs, Wind Turbine Generators (WTGs), and battery Energy Storage System (ESS). Different from the typical industrial solution, this hybrid APS system uses not only DGs, but also WTGs to supply part of the auxiliary load when there is wind blowing for reducing fuel consumption and the corresponding refuelling works; moreover, the wind turbine converters can provide reactive power for balancing the charging power from the cable array inside the OWF, so as to avoid the oversizing of DG itself. ESS are also introduced to further reduce the dependence on the DGs. With enough capacity of ESS, it is even possible to remove DGs while still be able to fulfil the requirement on auxiliary load supply during islanding mode. In this paper: firstly, the cost effectiveness of such hybrid APS is discussed via techno-economic analysis; secondly, two types of hybrid APSs with coordinated hierarchical control architectures are introduced, as well as the control strategy design for both centralized and distributed controllers; thirdly, simulation models are developed in MATLAB/Simulink, where two types of models are included. They are phasor-type model for centralized control strategy verification, and average-type model for distributed control strategy verification. The performance of hybrid APS models is validated under typical working scenarios, and the simulation results show that the control strategy has no high requirement on the communication speed between central controller and distributed controllers.