The currently deployed volt-var infrastructure for voltage optimization in distribution networks would be unable to meet the stringent technological requirements of the electric power grid of the 21st century. If not handled correctly, conventional voltage control systems could inhibit the ubiquitous deployment of renewable energy resources into the future smart grid. For example, the incorporation of renewable energy sources and the new types of energy storage systems in the distribution system provides a threat for the seamless voltage control. In order to overcome such barriers, smart volt-var control methods are needed to be studied and implemented. However, achieving such goals requires a complete background of the contemporary strategies and developments of the volt-var technologies. So far, various techniques have been developed to accommodate the large penetration of renewable energy sources into the distribution networks. This paper provides a comprehensive review on the curre
The emergence of distributed generation such as solar systems has introduced new challenges in distribution networks that are becoming more apparent with increasing penetration levels. The time mismatch between peak load and peak generation can make voltage levels in distribution networks swing towards extreme limits during a day. Distribution network service providers are struggling to cater for new distributed generation installations while ensuring that the quality of steady state supply voltage meets stipulated requirements. The segregation between medium and low voltage networks in control strategies may result in unnecessary or worse, opposing control actions leading to voltage issues and control on one side of the distribution network influencing the other. By developing an efficient volt/var control method, the steady state voltage level and voltage unbalance in a comprehensive distribution network can be controlled simultaneously. This paper analyses voltage issues and volt/va