Located near Ballyshannon, County Donegal, there are six 2.85MW Wind Turbine Generators (WTGs) and associated infrastructure at Acres Wind Farm.
The project is unusual in that the infrastructure also includes various grid support services including a GE Power Conversion synchronous compensation unit and GE Renewables windinertia units. The GE synchronous compensation unit consists of high inertia (20MWs, 11kV, 20MVA) and power converter (3.4MW) equipment located at the wind farm substation and connected to the 20kV busbar of Acres Wind Farm. This unit provides the grid with inertia during Rate of Change of Frequency (ROCOF). During a ROCOF event the rotating stabiliser creates a short ‘surge’ of power for a few seconds as the grid frequency is falling, in direction proportion to the ROCOF.
A GE WindInertia unit is also provided for each WTG. They provide inertial response to help stabilize grid frequency. There is no direct control interaction between the GE Wind Turbines, or the GE WindInertia product and the sync-comp and power converters. However, the sync-comp and power converter has been configured to complement and prolong the WindInertia response shape. It may also be configured to fill in the energy gap created when the WindInertia product operates. The GE WindInertia feature supports the grid during under frequency events; it provides a temporary increase in power production (6-7%) increase in kW for a approx. 10 sec., contributing towards frequency recovery. This is achieved by translating the transferring the mechanical inertia of the wind turbine rotor into a temporary increase of electrical power to assist in reducing the frequency nadir during the under frequency event. Once the temporary increase in power is applied, the wind turbine rotor recovers the generator speed and normal operation is resumed. By default, the response is tuned to be equivalent to that of a synchronous generator with an inertia constant of 3.5 sec., and may be further tuned within design limits.