Examenspresentation av Mahantha Ampavatina Kambagiri

Conducted at RISE supervised by Mattias Persson

Opponent: Børge Lund

Abstract
The rise in integration of renewable energy sources is reducing the power system inertia, which may worsen the frequency stability of the system. Low inertia makes the system fragile, where even small disturbances lead to large frequency deviations which can go outside the acceptable frequency band. As the frequency regulation is becoming more and more important and prices for it in the Nordic region reaches
higher levels, there is a need for ancillary services to mitigate the problem. The project investigated the potential of providing ancillary services using the Vehicle-to-Grid (V2G) technology in a low-inertia power system, dominated with renewable energy sources.

In this thesis, a preliminary power system model was developed in Simulink, consisting of a hydro generating unit and an aggregated EV model, which can provide ancillary services such as Frequency Containment Reserve for disturbances, upregulation (FCR-D up) and Fast Frequency Reserve (FFR) according to the technical requirements laid out by ENTSO-E. The delays pertaining to communication and hardware response were considered. Taking the Simulink EV model as a reference, an aggregated user-written EV model was built in PSS®E. The user-written EV model was introduced in the PSS®E Nordic 44 test network to study its impact on the frequency stability.

Prequalification testing of the aggregated EV model in both Simulink and PSS®E for the provision of FCR-D up and FFR indicated that they fulfilled the technical requirements to provide 100% of their capacity. However, when the communication and hardware response delays were introduced for FCR-D up, the prequalified capacity reduced as the delays increased. No delays were considered for the provision of FFR as fixed activation times are stated in the requirements. The frequency response of the power system model in Simulink to a disturbance, when the EV model provided FCR-D up service, showed that as the system inertia reduced, increasing the delays led the system to instability. The impact was observed to be less severe in the PSS®E Nordic 44 network and none of the selected delays destabilized the system. The FFR service on the other hand performed as intended in both Simulink and PSS®E in all scenarios and all activation frequencies. In low-inertia power system, it was observed that the FFR activated roughly at the same instant for all activation frequencies due to high RoCoF.

Welcome!

Mahantha, Mattias & Peiyuan