  This paper proposes a novel online measurement-based Wide-Area Voltage
Control (WAVC) method using Phasor Measurement Unit (PMU) data in power systems
with Flexible AC Transmission System (FACTS) devices. As opposed to previous
WAVC methods, the proposed WAVC does not require any model knowledge or the
participation of all buses and considers both active and reactive power
perturbations. Specifically, the proposed WAVC method exploits the regression
theorem of the Ornstein-Uhlenbeck process to estimate the sensitivity matrices
through PMU data online, which are further used to design and apply the voltage
regulation by updating the reference points of FACTS devices. Numerical results
on the IEEE 39- Bus and IEEE 68-Bus systems demonstrate that the proposed
model-free WAVC can provide effective voltage control in various network
topologies, different combinations of voltage-controlled and
voltage-uncontrolled buses, under measurement noise, and in case of missing
PMUs. Particularly, the proposed WAVC algorithm may outperform the model-based
WAVC when an undetected topology change happens.
