48 FDUL/VFXR/FDUG/VFXG/AFR/AFG Main features CG Drives & Automation, 01-7318-01r1
7.17.3.1.4 Over frequency ride through (OFRT)
The AFG dynamic frequency support for OFRT is implemented according to the specifications for LFSM-O (Limited
Frequency Sensitivity Mode - Overfrequency) in EN 50549-2 (2019, section 4.6.1), as shown in Fig. 45. The active power
response is activated (if enabled via [G341]) when the grid frequency is greater than the defined start frequency (Fstart) [G342]
for the intentional start delay time (tstart) [G343]. The amount of active power reduction is calculated based on the droop (D)
[G344] and the pre-disturbance active power (Pref ) according to below given equation.
Fig. 45 Active power response during OFRT (source IEC 50549-2).
Left: Fig. 45 - Example of Active power frequency response to over frequency.
Right: Fig. 45 - Example of active power frequency response to over frequency with configured deactivation threshold.
If the deactivation threshold feature is enabled, then there should be no response according to the droop for decreasing
frequency. Instead, the active power should remain constant until the frequency falls below the deactivation threshold (Fstop)
[G345] including an additional deactivation delay time (tstop) [G346].
7.17.3.1.5 Under frequency ride through (UFRT)
Active response to frequency deviations typically sets requirement for increasing the AC output power during low frequency
conditions. Therefore, active response during UFRT needs to be handled by the plant energy management control system.
7.17.3.2 Anti - Islanding detection (AID)
Two different methods for detecting the anti-islanding are implemented in AFG. These are:
- Passive anti-islanding detection (AID) method
- Active anti-islanding detection (AID) method
7.17.3.2.1 Passive AID method
This method detects islanding based on sudden voltage phase jumps or frequency jumps. Passive AID can be turned on or off in
menu [G331].
7.17.3.2.2 Active AID method
This method detects islanding based on active injection of detection signals. Active AID can be turned on or off in menu
[G332].
100% P
M
P =P
s=5%
ref
f =50,2Hz
1
f =deactivated
stop
M
[% P =%P ]
ref M
60% P
50,2 50,5 51,551,0 52,0
M
100% P
M
P =P
s=5%
ref
f =50,2Hz
1
f =deactivated
stop
M
[% P =%P ]
ref M
60% P
50,2 50,5 51,551,0 52,0
M
Active Power
Rate limited power increase after
deactivation of response
Frquency
[Hz]
Frquency
[Hz]
Active Power
Rate limited power increase after
deactivation of response
NOTE: Contact local supplier or authorized Emotron
service personal if further assistance is required with
AID detection.
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