Operation of a wind turbine permanent magnet synchronous generator (PMSG) for ancillary frequency support services

Abstract

Wind turbines (WT) have the potential to provide active power to participate in ancillary system service markets. Most existing research on wind farm provision of ancillary system services addresses kinetic energy recovery. However, controlled WT over-rating could also be used to deliver additional power in high wind conditions, but remains as of yet unexplored in the context of ancillary service provision. This paper proposes a new enhanced power recovery through overload (EPRO) strategy, combining pitch angle and field weakening controllers for overspeed/overload operation while considering the thermal state of the generator to exploit its thermal rating margin for increased power flow. The EPRO method is first examined using a WT electro-thermally coupled model developed in Matlab/Simulink and MotorCAD. Then, the integrated model is experimentally validated on an academic scale laboratory test rig embedded with an advanced fibre optic Fibre Bragg Grating (FBG) sensing scheme for thermal hotspot measurements. A field-measured wind speed profile is applied to the integrated model and the test rig where the primary (30 s) and secondary (30 min) ancillary service responses are introduced in line with the current UK market regulation. The simulation and experimental results show consistent trends. For a tested ≈40 % increase above rated active power delivery, a minor increase in temperature was observed for a primary 30 s overload. The temperature increased for the 30 min overload, however, the peak winding hotspot measured in this work remained comfortably within the generator thermal rating. Both these findings indicate a promising potential of the proposed EPRO strategy for provision of ancillary frequency support service.