This paper presents an investigation on the performance of voltage regulators (VRs) in mitigating overvoltage problems caused by distributed energy resources (DERs) in medium-voltage (MV) distribution systems. The control method of VRs is found to be a crucial factor. Studies reveal that even advanced control modes of commercial VRs cannot be relied upon as effective solutions to manage every scenario. The main problems associated with local control methods are identified. A supplementary voltage control scheme is proposed to enhance the capability of VRs as a solution option. The proposed scheme addresses the problems due to local control methods with a minimal investment. The studies are accompanied by several simulations on IEEE 123 nodes system as well as an actual feeder facing such overvoltage problems. Merits of the proposed supplementary control scheme are also demonstrated through simulation results.