The volume of services procured by transmission system operators (TSOs) through distribution-connected resources, aka distributed energy resources (DER), has been increasing in recent years. Currently, distribution networks are assumed to be fully capable of dealing with the resulting power flows. However, this assumption will no longer be valid as the volume of DER services become significant. Therefore, distribution system operators (DSOs) need to have a more active role to ensure the integrity of the distribution network while facilitating DER services. To achieve this, adequate coordination between TSOs and DSOs is required. To help stakeholders understand the implications of different coordination models so they can be adopted or tailored to their needs, this paper identifies three core TSO-DSO coordination models from the many proposed in the literature, discussing the corresponding advantages, disadvantages and challenges. Furthermore, a mapping of the proposed solution techniques is carried out to identify research trends and gaps.

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The growing adoption of residential photovoltaic (PV) systems around the world is presenting distribution network operators (DNOs) with technical challenges, particularly on low voltage (LV) networks. The need to mitigate these issues with simple yet effective measures in countries with high PV penetrations is likely to drive the adoption of limits on the very exports that affect this infrastructure. Defining the most adequate limit, however, requires understanding the tradeoffs between the technical benefits and the effects on PV owners. This paper proposes two methodologies: an optimal power flow (OPF) based technique to define the export limit that solves technical problems with minimal curtailment, and a Monte Carlo based analysis to investigate the spectrum of such tradeoffs considering different PV penetrations and export limits. A real U.K. residential LV network with 180 customers is analyzed using realistic 1-min resolution daily load and PV generation profiles across seasons. Results demonstrate that, for DNOs, the OPFbased approach is effective in determining the most technically adequate export limit. However, for policy makers, the spectrum of tradeoffs provided by the Monte Carlo approach can help defining export limits that reduce curtailment at the expense of partially mitigating technical issues. Index Terms-Low voltage networks, optimal power flow, photovoltaics, PV management. I. INTRODUCTION T HE need to reduce CO 2 emissions combined with attractive incentive mechanisms such as feed-in tariffs (FIT) or net metering schemes have encouraged in the last few years the growth of the global photovoltaic (PV) generation capacity,

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The number of residential consumers with solar PV and batteries, aka prosumers, has been increasing in recent years. Incentives now exist for prosumers to operate their batteries in more profitable ways than self-consumption mode. However, this can increase prosumer exports or imports, resulting in power flows that can lead to voltage and thermal limit violations in distribution networks. This work proposes a framework for Distribution Network Operators (DNOs) to ensure the integrity of MV-LV networks by using dynamic operating limits for prosumers. Periodically, individual prosumers send their intended operation (net exports/imports) as determined by their local control to the DNO who then assesses network integrity using smart meter data and a power flow engine. If a potential violation is detected, their maximum operating limits are determined based on a three-phase optimal power flow that incorporates network constraints and fairness aspects. A real Australian MV feeder with realistically modelled LV networks and 4,500+ households is studied, where prosumers' local controls operate based on energy prices. Time-series results demonstrate that the proposed framework can help DNOs ensure network integrity and fairness across prosumers. Furthermore, it unlocks larger profitability for prosumers compared with the use the 5kW fixed export limit adopted in Australia.