A Quantitative Method to Determine ICT Delay

Requirements for Wide-Area Power System Damping

Controllers

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Paper No: 15PESGMXXX

Nguyen Tuan Anha, Luigi Vanfrettib, Johan Driesena, and Dirk Van Hertema

aKU Leuven, BelgiumbKTH Royal Institute of Technology, Sweden

Background (What ?) A quantitative method to determine delay

requirements of the information and communication technology (ICT) system supporting wide-area power oscillation damping (WAPOD) controllers has been proposed. Equivalent time delay (ETD) is defined as an allowable

time delay for the ICT infrastructure. It is a time value for which Remote Input (RI)-based controller presents the same damping as Local Input (LI)-based controller.

(Why ?) The use of a WAPOD is only justified when its response outperforms that of a controller using local inputs. The total time delay in the control loop must be below the

calculated ETD. (Expected outcome?) ETD serves as a design criteria

to determine ICT latency requirements. The selection of an effective RI signal can be carried out by

considering the maximum delays (ETDs) of different wide-area measurements.

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Equivalent Time Delay (ETD)

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• ETDx% : allowable time delay at which the RI signals have a damping ratio which is x% higher than when using the LI signals

• ETD presents the maximum time delay of a wide-area measurement to provide the same damping as a LI signal

• ETDm : allowable time delay up to the stability margin, i.e. delay margin

A: Maximum damping level at zero delay

B: is defined as the improved damping required to provide x% of damping enhancement compared to the local signal

C: where RI-based controller yields the same damping as LI-based controller

D: delay margin ETDm (maximum allowable delay)

Methodology Demonstration: TCSC Design

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Inter-Area

Modes

Frequency (Hz)

Damping

(%)

Without TCSC

0.54 3.10

RI-based TCSC

0.57 16.9

LI-based TCSC

0.55 11.2

ETD 194 ms

ICT delays required for damping improvement

ETDs for different wide-area signals

Input Signal:

Conclusions

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• ICT delay requirements for WACS are defined by ETD.

• ETD provides the lower bound for the design of WAPOD (which the wide-area controller performs equally as the local-based controller).

• Thus, it is only beneficial to employ wide-area signals when the ICT delays are less than the ETD.

• Capital and operational expenditure costs of the ICT network have to be considered in practice.

• Laboratory tests for validation of the proposed methodology are needed.