This block is used to detect abnormal conditions in the grid’s frequency. For this purpose, a set of regions can be specified by the user as per [1]. A maximum of 8 different regions can be specified for over and under-frequency events, respectively. Also, this block detects when the average Rate of Change of Frequency (ROCOF) is above a specific threshold.

Mask and Parameters

Configuration

Name	Description	Unit
Sample Time (s)	Computational time step	s

Over-Frequency Range

Name	Description	Unit
Number of Over-Frequency Points	Number of over-frequency regions delimited by a set of frequency points	-
Frequency Points [Point1,…, Point 8]	Limit frequency values before reaching the respective over-frequency trip region	Hz
Time Points [Point1,…, Point 8]	Amount of time that the converter must operate in a frequency region before tripping	s

Under-Frequency Range

Name	Description	Unit
Number of Under-Frequency Points	Number of under-frequency regions delimited by a set of frequency points	-
Frequency Points [Point1,…, Point 8]	Limit frequency values before reaching the respective under-frequency trip region	Hz
Time Points [Point1,…, Point 8]	Amount of time that the converter must operate in a frequency region before tripping	s

ROCOF

Name	Description	Unit
ROCOF Threshold	Maximum allowed Rate of Change of Frequency (ROCOF) value before activating trip signal	Hz/s
Averaging Time Window	The time constant for the first-order average filter block for the Rate of Change of Frequency (ROCOF) estimation.	s

Inputs, Outputs, and Signals Available for Monitoring

Inputs

Name	Description	Unit
Freq	Grid frequency	Hz

Outputs

Name	Description	Unit
U/O F	Trip signal for under or over-frequency events	-
ROCOF	Trip signal for Rate of Change of Frequency (ROCOF) events	-

References

[1]	IEEE, "IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces," IEEE Std 1547-2018 (Revision of IEEE Std 1547-2003), no. doi: 10.1109/IEEESTD.2018.8332112, pp. 1-138, 2018.
[2]	IEEE, "IEEE Standard Conformance Test Procedures for Equipment Interconnecting Distributed Energy Resources with Electric Power Systems and Associated Interfaces," IEEE Std 1547.1-2020, pp. 1-282, 2020.

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