A- Background and objectives
The European Transmission Network (ETN) has been evolving significantly in the ways that network operators work and cooperate with each other, in particularly by setting up common operating procedures and tools such as network simulation tools . In the domain of power system state estimation and transmission network time simulation, very few innovations have emerged over the past decade (2000-2010) in Europe. Breakthroughs are therefore expected in power system simulation along four directions to serve the ETN: state estimation, optimization algorithms, time domain simulation and power system component modelling.
The PEGASE project aimed to remove several algorithmic barriers related to the monitoring, simulation and optimization of very large power systems, therefore paving the way for improved network operation.
B- Description of the result
A new Two-Step State Estimation (TSSE) algorithm has been developed, dividing the Pan European Transmission System into TSO areas, for which decoupled State Estimation are locally run. Then, boundary coupling among areas is taken care of by means of a coordination process. Compared to existing tools, the proposed TSSE makes use of the minimum area overlapping that allows all raw measurements to be processed during the first stage, which means that the coordination stage becomes linear. Furthermore, sparse weighting matrices are handled throughout the process, reducing the computational effort without sacrificing accuracy.
Tests have demonstrated that the proposed scheme involves a very modest amount of data exchange , while retaining essentially the same accuracy and capability for bad data identification as the conventional estimation of the entire Pan European Transmission System. The TSSE prototype is capable of solving any number of TSOs, arbitrarily interconnected, for any type of available measurements, including those provided by Phasor measurement unit (PMU) and current measurements. In addition to conventional network models, it considers advanced components, such as Phase-shifting Transformer (PST) and HVDCs. The TSSE prototype has been extensively tested to ensure the quality of results provided by this kind of algorithms, while minimizing data exchange between TSOs. The following scenarios have been tested: the France-Spain-Portugal TSO subsystem, the Russian, Turkish and UCTE systems, including point to point DC links.
The above results confirm the feasibility of a Pan-European State Estimator based on a hierarchical approach. There is no technical barrier to offer a full and coherent picture of the pan-European grid.
According to the PEGASE Consortium Agreement, the prototype software is owned 100% by RED ELECTRICA. It will transfer these rights to Red Eléctrica Internacional, S.A.U., the company within the REE group responsible for developing non-regulated activities, which in turn must reach an agreement with AICIA to provide the appropriate technical support and develop improvements to the existing prototype. This agreement would include joint commercialization efforts.