This article proposes two strategies for the mitigation of power imbalances and related costs resulting from increasing PV penetration onto the Italian grid. New "state of the art" solar and netload day ahead forecast models were developed and applied to real data. These strategies consist of: (1) Improving the accuracy of PV and net load power forecast and enlarging the footprint of the controlled grid area; (2) Transforming unconstrained PV plants into "flexible PV plants": remotely controlled PV plants that can be proactively curtailed and work with cost-optimized Battery Energy Storage Systems. We demonstrate that the first strategy can effectively limit the imbalance impact when integrating a large share of PV generation, reducing imbalance volumes and costs, both at current and future solar penetration levels. We further demonstrate that the second strategy can entirely eliminate the imbalance impact of PV penetration, hence providing operational certainty to the TSO. Indeed, we show how flexible PV plants can be cost-optimally sized to set the imbalance volume at a desired target value regardless of PV installed capacity, hence allowing massive solar penetration. Finally, we show that the cost of implementing these strategies is less than the current cost of handling such imbalance impacts. (C) 2020 Elsevier Ltd. All rights reserved.