Coordinated Control of Load Tap Changer Transformers for Voltage Regulation and Voltage Hunting Prevention: A Switched Systems Approach

We propose a coordinated control strategy for load tap changer (LTC) transformers in high voltage radial transmission systems that are connected to higher voltage grids and active distribution networks. We utilize switched systems modeling tools to capture the non-smooth characteristics of the LTCs. Our approach employs a state- and time-dependent switching logic to regulate the voltage at a specific node while preventing stability issues produced by the voltage hunting phenomenon. Then, we derive sufficient tuning conditions for the LTC control parameters, namely, deadband widths and time delays, as a function of the tap magnitude of the LTCs. These conditions ensure the existence of an exponentially stable equilibrium point of the closed-loop switched system and the exponential convergence of its output, i.e., the regulated voltage, to a desired set. Finally, a numerical example shows the proposed strategy's superior performance over an uncoordinated scenario.