Grid-Aware Provision and Activation of Fast and Slow Flexibilities from Distributed Resources in Low and Medium Voltage Grids

As more and more renewable intermittent generations are being connected to the distribution grid, the grid operators require more flexibility to maintain the balance between supply and demand. The intermittencies give rise to situations which require not only slow-ramping flexibility capability but also, fast-ramping flexibility capability from a variety of resources connected at the MV and LV distribution grids. Moreover, the intermittencies may increase the costs of grid reinforcement. Therefore, to defer the reinforcement of the grid assets, the grid needs to be operated optimally. This paper proposes - a) such an optimal operational methodology for the MV and LV grids; and b) an aggregated flexibility estimation methodology estimated separately for fast and slow services at the primary substation (TSO interface). The methodologies based on model-based MV grids and a sensitivity coefficients-based model-less LV grids are suitable for LV grids where an up-to-date and accurate model and topology are not always available. The approaches of the paper use the synchronised and accurate measurements from grid monitoring devices located at the LV distribution grids. It is assumed that the implementation of the methodology is centralised, where a grid monitoring device or a central platform is capable to host grid aware algorithms and to communicate control setpoints to DERs. The approaches have been validated on a real MV and LV networks of a Swiss DSO equipped with grid monitoring devices. The results, in terms of technical losses, grid violation costs and flexibility capability curve, show the efficacy of the optimal operation and flexibility estimation methodologies and therefore, can be easily deployed.