Automatic Voltage Regulation for Substation in Smart Grid

Abstract

The recent developments of smart grids and their Advanced Metering Infrastructures have brought new possibilities of enhancing the system performance and quality of power delivery to diverse consumers. For instance, with the existence of smart meters that measure, in real time, the voltage, current and power factor at the consumer side, it is possible to automatically control the voltage at the load side in order to improve the efficiency of the power delivery and to avoid voltage drop or rise beyond the acceptable limits set by the relevant standards. This research is intended to develop a new and simple technique for voltage regulation at the low-voltage side of power distribution network. The proposed technique uses the smart meters readings to regulate the minimum/maximum voltages within the standard limits. Meanwhile, it assures that all load voltages are set to their minimum possible values which reduce the energy consumption to the desired amount. This voltage control technique is implemented on a distribution transformer equipped with an On-Load Tap Changer (OLTC). The selection of the appropriate OLTC tap position is decided by a voltage control algorithm. The proposed OLTC uses Solid-State Relays (SSR) instead of the conventional mechanical relays. One of the advantages of the SSR is that it allows the OLTC to change more than one tap at a time. The proposed control technique is applied on an actual residential compound electric system. Several scenarios are considered testing the power quality and determining the energy saving. The scenarios investigated on power quality include over-voltage, under-voltage and voltage unbalance. The energy saving is due to two reasons; the proposed voltage control method and the choice of the tap controller. The results show that we can obtain a fast response of the OLTC while maintaining the voltage profiles for all nodes at desired levels. In addition, the results ensure that significant amount of energy can be saved without compromising power quality. It has been proved that DG in radial network configuration has less impact on the system using the proposed voltage control method compared to the tree network.