Deployment and Operational Experience of an Adaptive Wide-Area Damping Controller at the Italian Power Grid to Mitigate Continental Europe North-South Mode Oscillations

Retirement of conventional synchronous generators and their Power System Stabilizers (PSSs) may lead to additional major oscillation events due to insufficient damping control capability.

In the recent Iberian blackout incident, the well-known 0.2 Hz West-East mode of the CESAS and an atypical 0.6 Hz oscillation mode were observed, and they are considered a contributing factor to the incident.

To mitigate the North-South mode in the CESAS, a measurement-driven adaptive wide-area oscillations damping controller (WADC) has been developed and field deployed at the Italian

Transmission System Operator - Terna. The WADC is implemented as adaptors on Grid

Protection Alliance (GPA) openHistorian and a separate graphic user interface based on

Grafana. The WADC is field deployed at Terna’s control center and substations, employing a centralized control structure. Frequency measurements of two selected PMUs in south Italy are selected as the primary and backup input signals, and two synchronous condensers in south

Italy are selected as the actuators. The WADC can 1) Receive real-time frequency measurements from the primary and backup PMUs using the IEEE C37.118 over TCP/IP, 2)

Detect oscillations and calculate control commands, and 3) Send control commands to the actuators at remote substations using the IEEE C37.118 over UDP/IP.

The WADC includes advanced operational features. In particular, first, a ‘Modal Analyzer’ module is developed to determine whether to activate the WADC, together with the oscillation detector. The ‘Modal Analyzer’ is invoked every 25 seconds to perform modal analysis with the received frequency measurements. The length of the moving data window for the modal analysis is 20 minutes, refreshing at the rate of every 25 seconds. The WADC under normal operating conditions is in standby mode, and it is activated only when the targeted mode is identified as the dominant mode and an actual oscillation is detected. Second, a ‘System

Identification’ module injects a pre-defined probing signal to the grid via the actuator, identifies a transfer function using the system identification algorithm, and decides whether WADC’s control parameters need to be updated to accommodate grid operating condition variations.

Lastly, the software architecture has been improved to handle multiple actuators with flexibility and scalability.

After three years of field tests and trial operations, the WADC is presently operational as an automated wide-area monitoring protection and control (WAMPAC) tool that mitigates natural oscillations and enhances secure operation of power grids. The hands-on experience and lessons learned can be leveraged by system operators who plan to deploy a similar WAMPAC tool at their control centres. Currently, the WADC is being upgraded to use FACTS devices (e.g.,

STATCOM) as actuators, and the associated simulation verification and field testing are ongoing.