Automatic compensation voltage control strategy for on-load tap changer transformers with distributed generations

Nowadays, more and more distributed generations (DGs) are being connected to local distribution networks due to the variety of advantages they offer. Without any DG, the direction of power flow is always from the power grid towards the loads. Therefore, the voltages decrease along the feeder and the voltage control has to compensate for the resultant voltage drops. When DG is connected to the network, the direction of power flow can be reversed whenever the DG output power exceeds the local load. This bi-directional power flow complicates the voltage profile along the feeder and simple compensation is no longer effective. Furthermore, the voltage profile resulting from the power in-feed from the DG may be exceed the statutory limits. In these conditions, conventional on-load tap-changer (OLTC) voltage control methods will prove to be inappropriate. This paper presents a new OLTC voltage control strategy for use on networks where DG is connected that the level of bi-directional power flowing is considered in the control scheme. The paper describes the new OLTC voltage control strategy and demonstrates its improved performance using a selection of simulation studies. In addition to providing an automatic voltage setting point change for existing OLTC transformers with AVC relays, the new voltage control strategy facilitates the maximization of the power output from the connected DG. Techniques to develop the new OLTC voltage control scheme to accommodate the potential use of Smart Grids are discussed in this paper. The challenges and benefits of Smart Grids for OLTC voltage control are investigated. Data communication systems are considered to coordinate with the OLTC voltage control as one of the approaches to take full advantage of future Smart Grids.