This paper presents a centralized and a distributed voltage control strategies for a low voltage (LV) grid-connected microgrid with high penetration of photovoltaic (PV) systems. Both strategies are formulated as an optimal power flow (OPF) problem to minimize line losses and PV curtailments. Second-Order Conic Programming (SOCP) relaxation is formulated to "convexify" the OPF problem. Alternating direction method of multipliers (ADMM) is implemented for the distributed voltage control strategy. Moreover, weighting parameters for both controllers are introduced to have more flexibility in the controller operating mode. A sensitivity analysis on those weighting parameters allows to identify different operating regions, with priority given to loss reduction or curtailment minimization. In particular, we identify an infeasible region in cases where the considered SOCP relaxation is not valid, which highlights the need for fine parameter tuning of the controllers. The effectiveness of both voltage control strategies is validated in a LV radial microgrid.Index Terms-alternating direction method of multiplier (ADMM), optimal power flow (OPF), photovoltaic (PV) system, second order cone relaxation, voltage control

This paper focuses on a local energy market where a group of households in a low voltage (LV) grid is organized as an energy community. A three-stage management strategy is proposed under the French collective self-consumption framework. In the first day-ahead stage, households coordinate with the community manager to minimize the overall energy bills for the next day. Then, real-time operation (second stage) focuses on the mitigation of forecast uncertainties and voltage violation, by utilizing the reserve of the local production/storage assets. Finally, the third stage contractually allocates the community energy among the households on 30 min basis (based on the French regulation), in order to ensure fair individual cost reduction and possibly create economic surplus in the community. The proposed community management strategy is evaluated on a LV grid with 55 households, and the results show the proposed strategy achieve an average of 30 % individual cost reduction among the users compared to the base scenarios. Furthermore, different pricing scenarios are compared through sensitivity studies and scalability tests are run on larger systems.

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