A novel compensation scheme based on a virtual air gap variable reactor for AC voltage control

Voltage control based on reactive power compensation is a fundamental aspect of the operation of ac electric power systems. This paper presents a novel shunt compensation scheme based on a virtual air gap variable reactor. The scheme is fully developed, from the adaptation of the virtual air gap principle to high-voltage applications and the determination of its expected performance, to the proposal of a digital cascade control using internal model and proportional-integral controllers. The suitability and flexibility of the device, and the voltage control and reactive power compensation scheme are verified by means of laboratory tests performed in a small-scale prototype. Measured results show that the proposed device and its control provide a robust load compensation scheme for ac systems