Increasing Transmission Grid Flexibility by TSO Coordination to Integrate More Wind Energy Sources While Maintaining System Security

Abstract

The transmission grid in Europe is interconnected to guarantee the security of supply and to facilitate the competition among different market players, thereby making the system highly meshed. It is a challenging task for the transmission system operators (TSOs) to manage the power flows in their system, especially in the light of integration of renewable energy generation sources into the transmission system. The intermittent nature of such generation sources creates variable power flows and loop flows, in turn, questing for installation of controllable devices to manage these flows. The TSOs are currently installing such devices to cope with the situation. A proper coordination is needed for the operation of these devices, since they can lead to adverse effects on power flows in a meshed system. Coordination among TSOs in Central Western Europe (CWE) is performed, however, not towards a full system-wide objective, since there is no regulatory framework that exists for such coordination. This paper focuses on the potential of coordination among TSOs with respect to operation of the controllable devices. Two aspects are investigated: management of constraints in the system in the dayahead scheduling process and wind in-feed optimization. Both approaches are implemented at the Regional Security Center and tested on a high-stress situation in the CWE region. Furthermore, a case study at the coordination center is performed using actual data for the month of January 2013 to assess the usefulness on a longer time period. Index Terms-Coordination, high-voltage direct current (HVDC), phase-shifting transformer (PST), transmission system operations, uncertainty management. NOMENCLATURE l Line index. t Time index. b Node index. N h Number of hours. c Contingency index. j PST index. N P ST Number of PSTs. N b Number of nodes.

Towards Flexibility Trading at TSO-DSO-Customer Levels: A Review

“…Cooperation among TSOs is also needed in the operation of transmission networks. For instance, it has been proven that optimal cooperation between TSOs would lead to enhanced flexibility in transmission networks and could simultaneously enable higher penetration of renewables into the power system [22]. In addition, the cooperation between 34 European countries has been presented with the aim to increase the security and sustainability of the interconnected European power system as well as to develop the European energy markets [23].…”

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“…Thyristor controlled series capacitor (TCSC) has been applied to make a better utilization of wind power generation in [68,69]. Phase-shifting transformer has shown excellent capability in mitigating congestion due to the forecast error of renewable generation [70].…”

“…Coordinating the different resources of flexibility may help to improve power system security and economics under uncertainty, facilitating the integration of renewable energy generation with less investment. Some contributions have been made in the coordination of generation-side and grid-side flexibility in economic dispatch [68,69,70,86,94] system expansion planning [131,132,133,134,135,136,137], transmission-generation-demand response co-optimization [138], transmission expansion planning with demand response resources [92].…”

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“…Providing sufficient transmission capacity and interconnections (AC lines or HVDC (high-voltage direct current) cables) between market areas or regions enhance the transmission flexibility, reliability and improve power-sharing control [8]. Deployment of power flow controlling devices (PFCs), such as PSTs (phase shifting-transformers) and HVDC enhances flexibility in for instance European transmission system [15]. The flexibility in the transmission system to integrate large-scale renewable energy resources is determined according to adequacy and security evaluations of the grid infrastructure [16].…”