A review of voltage control techniques of networks with distributed generations using on-load tap changer transformers

Voltage is an important parameter for the control of electrical power systems. The Distribution Network Operators (DNO) have the responsibility to regulate the voltage supplied to consumer within statutory limits. Traditionally, the On-Load Tap Changer (OLTC) transformer equipped with automatic voltage control (AVC) relays is the most popular and effective voltage control device. Connecting Distributed Generation (DG) to the network inherently affects the feeder voltage profiles and influences the voltage control in distribution systems. In recent years, the number of DGs connected to the distribution networks is continuing to grow. Their impact on the network is therefore demanding proper attention and is affecting the design of new automatic voltage control schemes for OLTCs. The potential for using Smart Grids also promises to have a major influence on schemes for voltage control in the power systems. This paper presents an overview of existing OLTC control schemes which are used to control the voltage in distribution networks. It includes a discussion of new techniques which have been introduced and those being proposed to improve voltage control for networks containing various levels of DG. It also examines the potential opportunities for OLTC voltage control schemes offered by the use of Smart Grids.