REVIEW OF AUTOMATIC VOLTAGE REGULATOR CONTROL SCHEMES FOR IMPROVING TERMINAL VOLTAGE OF SYNCHRONOUS GENERATOR

Fluctuations in voltage in electrical power systems can cause events like voltage drops, spikes, or surges, which pose significant risks to electrical equipment and general system stability. The use of Automatic Voltage Regulators, AVR in power generation units has considerably helped the stability of the power systems. A good and effective controller or a control scheme applied in the closed control system of the AVR unit will ensure the generating sets operating at conditions that are stable and safe for smooth operations, with a fast response over all kinds of disturbances, this is essential in stability of a power system. This study presents a clear survey via various implemented control schemes for the performance enhancement of AVR systems and the need for control frameworks that address performance against system uncertainties and efficiency between 2014 and 2025, in order to enhance power system stability management. In the survey, it has been revealed that among the proposed and implemented control mechanisms, PID is the most implemented, whereby the majority of the current studies are focused on optimizing its gain parameters. The optimization methods are usually performed by either bio-inspired or intelligent algorithms like artificial bee colony (ABC), particle swarm optimization (PSO), teaching-learning-based optimization (TLBO), bacteria foraging optimization (BFO), genetic algorithm (GA), and other variants of these techniques. This paper discussed the trends, gaps, and the future of AVR control scheme design for enhanced voltage regulation in power systems.