The rise of variable renewable energy sources like wind and solar power and the gradual decommissioning of conventional power plants driven by fossil fuels or nuclear energy result in the decline of the system inertia in power networks. The development of modern power networks leads to an increasing complexity in the power systems studies and more particularly to new challenges in power system stability analysis and control. The lack of inertia will make increasingly difficult to maintain a constant frequency in the system with damping of inter-area oscillations which will become more critical. The main challenge which will be addressed in the RITSE project is to contribute to increase the power system flexibility with the development of new stability resources and their associated integrated controls as new tools for the power system operators.
RITSE aims to enhance the electricity system’s transient stability and small signal stability via innovative controls to i) improve the behaviour of the HVDC-VSC link (DVAC), ii) for battery storage systems (BATTERTIA) and iii) for a correct coordination of both (DVAC + BATTERTIA).
DVAC consists of an innovative control to improve the behaviour of the HVDC-VSC links, thus contributing to the transient and small signal stability improvement of the connected AC power networks.
BATTERTIA proposes a development and experimental validation of a novel control system for distributed storage systems with batteries, offering an improved behaviour compared to the battery systems which are currently installed.
The two solutions are complementary as DVAC acts on the global scale while the BATTERTIA solution acts locally. Their coordination will yield in increased margins of the transient stability in the AC power system and will support future stability of the networks with high share of renewable energy and reduced system inertia.
Impact for the TSO
The combination of control strategies for distributed storage systems with batteries and for HVDC-VSC links is of prime interest for TSOs. In practice, the BATTERTIA solution allows the creation of strong zones within the power systems that respond predictably and in a conventional way to system perturbations. DVAC manage the interaction between those zones and guarantee any potential oscillations to evolve in a safe and predictable way. Both controls will be tuned in a coordinated way in order to increase the damping produced by each of them separately.
TSOs and DSOs will benefit from an integrated and coordinated solution for improving the transient stability of future power networks. Such solution will facilitate TSOs to address the possible interarea stability issues caused by imminent integration of European electricity markets, among other reasons.
Grid2030 is a two-years collaborative innovation programmed focusing on innovation development with the objective of demonstrating that technology, basic products, services or processes can work in a business set up. Through the “Reduced Inertia Transient Stability Enhancement” (RITSE) project, SuperGrid Institute and IMDEA created a partnership to improve the transient stability of the AC networks by coordinating the local use of batteries equipped with BATTERTIA control and more global action by the use of HVDC links equipped with supplementary control action trough DVAC.
IMDEA Energy Institute proposed a novel control system BATTERTIA for battery-supported power electronics converters that offers the enhanced voltage support and inertial functionalities to electricity network operators. Unlike the existing power battery interfaces offering only active and reactive power controls, BATTERTIA has the same inertial and voltage support characteristics as a synchronous generator. In this way it helps the network retain and improve its transient and voltage stability properties during the on-going process of power systemdescarbonization. BATTERTIA represents the enabling technology for the batteries to enter ancillary service market and compete with existing inertia reserves provided by rotating machines. As such, it has a direct impact on DSO and TSO capacity to operate MV and HV networks, secure the power system stability and allow a massive and safe connection of Renewable Energy Sources.
BATTERTIA overview – power stage and the measured quantities
Matlab/Simulink model of BATTERTIA deployment in a Canary Islands test network
By taking into account the fast response capabilities of the HVDC, the so-called DVAC (for Dynamic Virtual Admittance Control) that calculates a supplementary active power reference of an embedded HVDC link is proposed by SuperGrid Institute with the aim to enhance the rotor angle stability of the surrounding AC system. The DVAC technology could be designed and integrated within an HVDC link to respond to the TSO requirements in one hand and to enable new ancillary services related markets in other hand. More specifically, DVAC solution can play a key role in operational management of power networks as well as in frequency and voltage control and system restoration, with its inherent properties for instantaneous reserve sharing and islanding/synchronization capabilities.
Proposed supplementary (DVAC) control of HVDC link
The proposed controller and its improvements, were implemented on the industrial software PSSE where the European Network is simulated including the INELFE HVDC link