Voltage regulation system for OLTC in distribution power systems with high penetration level of embedded generation

In this paper, a voltage regulation system is proposed that improves the voltage regulation process in power distribution networks with a high penetration of embedded generation. The principle of the proposed system is to alter the existing and conventional substation busbar monitoring technique of the on-load tap changer (OLTC) commonly implemented in medium voltage power distribution networks. The system alternatively uses measured multiple voltage magnitudes on different vital locations on the power distribution network, it thereafter isolates the uppermost and the lowermost measured voltage magnitudes from all voltage inputs received. The sampled uppermost and lowermost voltage magnitudes are compared with predetermined set voltage limits, and the OLTC will change its tap settings to keep the uppermost and lowermost voltage magnitudes within the set voltage limits. To avoid tap hunting when set voltage limits cannot be maintained, the system will reduce the active power generated by the embedded generator to a predetermined value. On the other hand, the system will monitor the load on the feeder in which the embedded generator is connected and then increase the embedded generator active power generation again when the load start increasing. The proposed voltage regulation system was tested on a typical South African power distribution network consisting of a substation with an OLTC equipped power transformer that is simultaneously regulating voltage of three medium voltage feeders. The voltage regulation system managed successfully to keep feeder's voltages within the acceptable limits.