Implmented technologies enabled greater integration of RES in the transmission and distribution grids and lead to more efficient use of existing infrastructure.

Compensation devices for reactive power control

ELES and HOPS installed six compensation devices. In Slovenia, they installed a stationary compensation device with STATCOM technology of +/- 150 Mvar at the Beričevo substation, variable shunt reactor of -150 Mvar and the mechanically switched capacitor with a damping network of +100 Mvar at the Divača substation. In Croatia, three devices were installed – variable shunt reactor of -100 Mvar at the Mraclin substation, variable shunt reactor of -200 Mvar at the Melina substation and stationary compensation device with an SVC technology of - 250 Mvar at the Konjsko substation.

With the installation of those devices, they achieved the goals of voltage profile control and the possibility of voltage regulation in the electricity systems of both Slovenia and Croatia. Furthermore, this innovation by ELES and HOPS also introduces the completely new possibility of joint regulation of both systems. As a result, compensation devices will contribute to better network stability in emergencies. Moreover, the effects of their operation will also positively impact the networks of neighbouring countries.

Battery Energy Storage Systems

The battery energy storage systems were installed in Slovenia at the Pekre and Okroglo substations. They are based on lithium-ion cells and have a total active power of 10 MW and a nominal capacity of 50 MWh (each 10 MW / 25 MWh). When the project was designed, it was one of the most significant battery storage projects in the wider European area.

Battery energy storage systems operate in the newly developed smart automatic elimination of rapid system deviation service. Compared to classical generation units, the key advantage of BESS is the ability to quickly change the power, while the deficiency is limited energy capacity.

These systems are a solution for today and a key to the future. They will play a crucial role in the transition to future electricity systems, where electricity production from dispersed renewables and the active participation of prosumers in the energy market will be the norm.  

 

Dynamic Thermal Rating System

In the scope of the project, the dynamic line rating (DLR) algorithms and models for the DLR system, which calculates the dynamic thermal limits of transmission lines for operation in real-time and short-term forecasts, were improved. In addition, innovative weather stations were installed on twelve transmission lines in Slovenia and Croatia. Data from those weather stations improve the mesoscale weather data obtained from the Slovenian Environment Agency, thus reducing any uncertainties in calculations. 

ELES and HOPS use the results to improve the safety of operation and the transmission capacity of the network. This way, the existing infrastructure is used more efficiently. Furthermore, with the increase of cross-border transmission capacities, it is also possible to transfer larger quantities of energy from renewable sources in the south of Croatia to the markets in the region.

Virtual Cross-border Control Centre

ELES – HOPS Virtual Cross-border Control Centre (VCBCC) was set up for coordinated and controlled centralised representation of RES production and system variables of Slovenian and Croatian HV and MV networks to allow power system optimisation in the whole control area. The VCBCC consists of numerous IT and TC solutions that enable data acquisition from RES, improving energy network observability and more accurate forecasting of renewable energy sources production. 

The Centre provides for the reliable exchange of operational data between project partners, as well as the option of including new balancing service providers, thereby increasing grid flexibility, enabling exchange of operational data under modern standards, and optimising the network voltage to ensure voltage conditions within permitted operating limits. This is the first case in Europe where neighbouring transmission system operators have joined forces in regulating and optimising the voltage in their networks.

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