Impact of Distributed Generation on Distribution Systems with Cascaded Bidirectional Step Voltage Regulators

Distribution grids with high penetration rate of distributed generation (DG) are often subjected to undesired reverse active power flow scenarios. Depending on the interactions between the DG's control modes and the feeder's step voltage regulators (SVRs), abnormal situations such as the phenomenon known as reverse power tap changer runaway condition may occur. This paper investigates the impact of DG on a distribution network with two cascaded SVRs, both operating in bidirectional mode. Tests were performed using two different control modes of the DG: unity power factor control, which is typically employed, and voltage control. The results obtained from time series power flow simulations show the behaviour of the cascaded SVRs and their effects on the feeder voltage profile. Special focus is placed on scenarios where the penetration level of the DG, located at the far end of the feeder, exceeds the total load demand.