New Optical Voltage Sensor Based on Closed-Loop Pockels Cell and Sliding Mode Observer: Theory and Experiments

Area of Science:

• Electrical Engineering
• Sensor Technology
• Control Systems

Background:

• Substation power demand and smart grid advancements necessitate advanced voltage measurement solutions.
• Optical voltage sensors (OVSs) using the Pockels effect offer advantages over traditional transformers, including lower cost, smaller size, and no explosion risk.
• Existing OVSs require efficient demodulation techniques to overcome limitations like signal fading.

Purpose of the Study:

• To demonstrate the efficacy of a nonlinear digital controller for optical phase demodulation in OVSs.
• To validate the controller's performance using sliding mode theory for enhanced measurement accuracy.
• To assess the OVS with the new controller for power quality measurement applications.

Main Methods:

• Development of a versatile nonlinear digital controller based on sliding mode theory.
• Implementation of a proportional-integral feedback control for signal stabilization and quadrature signal generation.
• Experimental validation using sinusoidal voltages and comparison with a commercial high-voltage probe.

Main Results:

• The OVS exhibits excellent linearity, a 3 kHz bandwidth, and high input impedance.
• The nonlinear digital controller successfully demodulates optical phase signals, achieving peak-to-peak relative errors below 0.8%.
• Total harmonic distortion (THD) relative errors were under 1.5%, meeting Class 1.0 of the UNE-EN 60044-7 standard.

Conclusions:

• The proposed nonlinear digital controller is highly efficient for OVSs, enabling precise voltage measurements.
• The system demonstrates strong potential for accurate power quality measurements in smart grid environments.
• This technology offers a viable, high-performance alternative to traditional voltage measurement instruments.