User Manual
99
Response to a decrease in grid frequency:
When there is a decrease in grid frequency which
falls below the Start value (
49.75 Hz
), the inverter
will reduce the sinking power from the grid linearly
with a decrease of frequency until the End value
(
49.00 Hz
) is reached.
When the frequency falls below the End value, the
inverter should have ceased sinking power from the
grid (i.e. 0 W).
UnderFrq Start
UnderFrq End
49.75 Hz
49.00 Hz
The import power for charging the storage system will remain at or below the
lowest charge rate reached in response to a low-frequency event between
49 Hz and 49.75 Hz. This is to provide hysteresis in the control of the
inverter.
When the grid frequency has increased back to 49.85 Hz or more for at least
60 s, the charge rate of the storage system may be increased at a rate no
greater than the power ramp rate limit, which can be set according to “10.4.7
Setting the Protective Parameters
”.
Input Power
Grid Frequency, Hz
46.5
47.0 47.5
48.0
48.5
49.0
49.5 50.0
50.5
51.0
51.5
52.0 52.5
Max. charge rate of energy storage
Charge rate prior to
frequency disturbance
Required reduction in charge
change rate of inverter in
response to frequency falling
below 49.75 Hz
Max. charge rate of inverter in
response to frequency returning
to 50 Hz after a disturbance
Allowed ramp up rate once
frequency has returned to
49.85 Hz for at least 60 s
Fig. 12-6
Frq-Watt Mode for Under-frequency Conditions
