The increasing penetration of renewable energy sources in power systems has increased the amount of generating units employing power electronics as their grid interface, instead of synchronous generators. Their different dynamics have brought new challenges for power system operators; in particular, the reduction of the total inertia of power systems, which leads to larger frequency disturbances. Different methods have been proposed to address this issue, with virtual synchronous machines as a promising solution; however, the start-up process of these controllers has not received much attention. This paper proposes a start-up strategy for the synchronous power controller, explaining its working principle in detail, and assessing its performance through time-domain simulation.