In distribution power systems, feeder voltages can be very sensitive to changes in load and/or distributed generation. This paper introduces a solid-state-transformer-based local voltage-control strategy to reduce variability distribution system bus voltages. An online dynamic volt-var control (VVC) algorithm is proposed to regulate bus voltages by injecting or absorbing reactive power through a solid-state transformer (SST). The proposed algorithm does not require any communication between the SST and the substation and makes control decisions locally. The main goal of the voltage-control algorithm is to enforce strict voltage constraints on the system voltages. The proposed control algorithm is validated in a radial and meshed distribution system using PSCAD.