Future active distribution grids (ADGs) will incorporate a plethora of Distributed Generators (DGs) and other Distributed Energy Resources (DERs), allowing them to provide ancillary services in grid-connected mode and, if necessary, operate in an islanded mode to increase reliability and resilience. In this paper, we investigate the ability of an ADG to provide frequency control (FC) in grid-connected mode and ensure reliable islanded operation for a pre-specified time period. First, we formulate the operation of the grid participating in Europeantype FC markets as a centralized multi-period optimal power flow problem with a rolling horizon of 24 hours. Then, we include constraints to the grid-connected operational problem to guarantee the ability to switch to islanded operation at every time instant. Finally, we explore the technical and economic feasibility of offering these services on a balanced low-voltage distribution network. The results show that the proposed scheme is able to offer and respond to different FC products, while ensuring that there is adequate energy capacity at every time step to satisfy critical load in the islanded mode.

Advanced optimization techniques for voltage support planning in self-dispatch systems present several opportunities for transmission system operators. Before an initial implementation of such techniques in daily operation, the expected benefits are usually assessed. However, such an assessment is subject to high uncertainties related to the expected participants' behavior. A proper assessment of consequences of applying optimization for voltage support planning requires an ex-post analysis with several years of operational data. This paper contains a breakdown of relevant impacts based on five years of operational data from the Swiss transmission system. It discusses the challenges of increasing penetration of renewable energy sources on the transmission system voltages and identifies drawbacks of the voltage support planning applied in Switzerland. Finally, it quantifies potential improvements, such as moving the voltage planning closer to real-time in order to account for intraday market activity.

No abstract

No abstract