In this paper we evaluate the potential of distributed photovoltaic (PV) plants for providing primary voltage control to the local distribution grid. Compared to the existing literature, we design an algorithm that schedules the nodal active and reactive powers of the controllable resources using a fair objective given by the active power injected by the distributed PV plants. Additionally, we propose both a centralized and a distributed version of the control algorithm. The latter is based on a dual decomposition framework and allows each controllable resource to schedule its power production independently of the others. We evaluate the proposed algorithms using the CIGRE LV benchmark grid and we show that (i) both algorithms are able to maintain a voltage profile within acceptable limits for safe operation and (ii) the distributed version of the algorithm converges to the same solution as the centralized one.