Reduced order WECC modeling for frequency response and energy storage integration

This paper presents a simple reduced order model of the western grid interconnect (WECC) that includes interconnect inertia, load frequency response, and generation primary frequency response. The model is validated against detailed power flow and transient response studies and recreates the WECC frequency response to a large generator outage to within 0.01 Hz RMSE, with the same frequency nadir and settling frequency. To properly capture the generation primary response, three classes of generation are used: slow, medium, and fast. The slow group responds with a time constant of 27 seconds, the medium group with a time constant of 19 seconds, and the fast group with a time constant of 0.5 seconds. The model is used to investigate the usage of domestic water heaters to assist in primary frequency response and reduce the impact of sudden load or generation changes. It is shown that even a very small-scale implementation of demand response via domestic hot water heaters (about 1 %) can improve the frequency nadir by 10 %, from 59.666 Hz to 59.697 Hz. The settling frequency is improved from 59.768 Hz to 59.789 Hz.