CPS SCA25KTL-DO/US-208 - Page 100

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Power vs Grid Frequency：The active power output shall be as defined by
the relevant formula below, plus any inertial response to the rate of change of
frequency, until frequency returns to within the dead band.(See Figure 6-4)
P/W(%)
100%
FreDroop_DbOf(Hz)
FreDroop_DbUf(Hz)
Freq(Hz)
SysFre
q
Figure 6-14 Curve of frequency derating
Formula for over frequency :
P=P
pre
+( F
n
+FreqDroop_DbOf- F
pre
) / F
n
/ FreqDroop_KOf
Formula for under frequency:
P = P
pre
+ (F
n
- FreqDroop_DbUf - F
pre
)/ F
n
/ FreqDroop_KUf
where
P is the active power output, in p.u. of the DER nameplate active power
rating;
P
pre
is the pre-disturbance active power output at the point of time, in p.u.
of the DER nameplate active power rating;
F
n
is the grid rated frequency
F
pre
is the disturbed system frequency in Hz