Voltage control of distribution network with distributed/embedded generation using fuzzy logic-based AVC relay

Voltage control is considered one of the basic operational requirements of electrical power systems both at distribution and transmission levels. It continues to attract the attention of workers to improve and/or develop new voltage control techniques particularly to accommodate distributed generation. The most popular voltage control equipment includes on- load tap changer (OLTC) transformer controlled by automatic voltage control (AVC) relay, which is mostly used in 11 kV networks. In recent years, a growing number of distributed/embedded generators are connected to distribution networks. Conventional AVC relay usually equipped with compounding whose setting are chosen to compensate for the voltage drop along the feeder(s) emanating from source substation. However, the integration of distributed/embedded generators (DG/EGs) including wind farms into distribution systems causes voltage regulation problems due to the interference with the performance of AVC relay. It has been found that the presence of DGs causes the voltage measured by conventional AVC relay to be shifted upwards or downwards compared depending on the power factor of the current through OLTC transformer. It also depends on the power factor of DG and system load. As a result, a proper voltage control of distribution network can not be achieved. Therefore, a new voltage control scheme of supply system with DG will be developed. This paper presents an attempt to design an AVC relay based on fuzzy logic (FL). In this paper the structure of the proposed FL based AVC relay is presented and the results that show its performance with and without embedded generation in distribution network are also presented and discussed.