Modelling of a wind-pumped hydro scheme within the Irish liberalised electricity market

Due to the rapidly increasing wind energy penetration in Ireland, concerns that the electricity system will be unable to cope with large amounts of wind powered generation (WPG) have arisen. Adverse impacts on operating reserve requirements and conventional plant operation are possible due to inaccuracies in wind forecasts and WPG variability. Pumped hydro energy storage (PHES) can improve wind farm out put in the following areas: dispatchability, variability and predictability. This in turn will also allow a greater level of market participation and ancillary service provision by wind generators. The model outlined in this paper is constructed using Matlab-Simulink software with a time series of measured wind speed data to simulate the real time operation of a combined wind/PHES system supplying energy to the Irish electricity grid. The operation of the hybrid system is controlled using a generated output schedule. The scheduled power is compared to the wind farm output to determine how much power should be stored or taken from storage at each half-hourly time step. For the operating schedule discussed, the variability of the wind farm output over the half-hourly time steps can be significantly reduced using PHES. There is a steady decrease in average dP/dt (change in output over 1/2 hour) as the storage capacity increases, until a saturation point is reached. The flexibility of the model allows the user to investigate the effects of different operating regimes for a range of wind farm sizes given any specific site.