Suppressing ferroresonance in potential transformers using a model-free active-resistance controller

Ferroresonance, excited by saturated electromagnetic voltage transformers, can severely damage power systems because it produces long duration large overvoltages. In this paper, a method is developed to eliminate potential transformer (PT) ferroresonance through a model-free method. First, a structural diagram of the ferroresonance eliminating device is established based on a practical ferroresonant circuit. The effect of the adjustable parameters of the device is investigated, including resistance, pulse frequency, and pulse duty cycle. Then, Iterative control strategies are developed to adjust the gate signal duty cycle of the controller for limiting the ferroresonance to a normal status and then switching off the elimination device. Finally, simulations are conducted demonstrating that the method proposed was effective.