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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

NameDescriptionUnit

Sample Time (s)

Computational time step

s

Over-Frequency Range

NameDescriptionUnit

Number of Over-Frequency Points

Number of over-frequency regions delimited by a set of frequency points

-

Frequency Points

(Hz)

[Point1,…, Point 8]

Limit frequency values before reaching the respective over-frequency trip region

Hz

Frequency

Time Points

(s)

[Point1,…, Point 8]

Amount of time that the converter must operate in a frequency region before tripping

s

Under-Frequency Range

NameDescriptionUnit

Number of Under-Frequency Points

Number of under-frequency regions delimited by a set of frequency points

-

Frequency Points

(Hz)

[Point1,…, Point 8]

Limit frequency values before reaching the respective under-frequency trip region

Hz

Frequency

Time Points

(s)

[Point1,…, Point 8]

Amount of time that the converter must operate in a frequency region before tripping

s

ROCOF

 Image Modified 

NameDescriptionUnit

ROCOF Threshold

Maximum allowed Rate of Change of Frequency (ROCOF) value before activating trip signal

Hz/s

Averaging Time

Window (sec)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

NameDescriptionUnit

Freq

Grid frequency

Hz

Outputs

NameDescriptionUnit

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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