A Simplified Algorithm for OLTC Control in Active Distribution MV Networks

The increasing penetration of Distributed Generation (DG) in distribution electrical systems may cause alteration of voltage profiles on the lines. Traditionally, distribution networks with radial configuration are designed as a passive top-down architecture where voltage regulation is mainly performed by an On-Load Tap Changer (OLTC) transformer located at the Primary Substation. Therefore it becomes rather difficult to compensate lines radiating out from the same bus-bar where some of these are subject to overvoltages due to the power injection by DGs connected whereas others are subject to voltage drops due to the presence of passive loads only. A first step in regulation and managing the voltage levels, in order to be consistent with the contingent needs of the network, may be a decentralized local control strategy performed by the DG units, however better results will be obtained with a coordinated OLTC intervention. In this paper an OLTC control strategy, based on only few remote measurements, is proposed. This procedure allows the tap changer controller to infer the state of network node voltages and to act accordingly. The performance of the proposed control method is demonstrated through simulations on a realistic MV distribution network.