A Method for Voltage Regulation in Distribution Network Equipped With OLTC Transformers and DG Units

This paper analyzes the possibility of an under-voltage caused by installing a DG (Distributed Generation) unit on a feeder where voltage regulation is controlled by the substation OLTC (On Load Tap Changing) transformer that is equipped with LDC (Line Drop Compensator) controls. In this a case, the introduction of the DG may confuse the regulator in setting a lower substation transformer secondary voltage than necessary, thus causing excessively low voltages towards the feeder end. The section that follows derives approximate voltage drops along uniformly distributed feeders under the presence of a single DG unit, in this paper a method for maximum DG size at a given location, and minimum distance from the substation a given DG size can be installed, that result in acceptable voltage are derived. The proposed method is tested on distribution system, IEEE 11 node with slightly modified parameters. The results demonstrate the validity of the proposed method for impact of DG on voltage regulation feeders equipped with OLTC transformer.