Fig. 4 shows the simulation results of Model-1 for a ‘Service2’ EFR with a target SOC band of 45-55%. On the frequency plot, the DB (±0.015 Hz) is shown by the green lines. It is clear that the SOC sharply drops, reaching 0% at 11:00, and stays there for ~30mins due to the grid frequency demands at that time. As the frequency stabilises, the EFR algorithm charges the battery when it is permissible (frequency in DB) and returns the SOC to within the specified band of 45-55%. The power response versus frequency plot of EFR Model-1 for 21st October 2015 is shown in Fig. 7(a). The red lines represent the upper, reference and lower EFR power lines. It can be seen that the EFR power (blue circles) does not remain within the required zones of ‘A’ and ‘B’. As outlined in Fig. 1, this is
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