A Non-Invasive Voltage Measurement Method for Power Grid Converter Valve Scenarios

Accurate non-invasive voltage measurement is critical for the stable operation of ultra-high-voltage direct-current (UHVDC) grids. In practical converter valve environments, voltage inversion based on the charge simulation method (CSM) may be affected by nearby charged conductors. To address this problem, this paper proposes a non-invasive voltage measurement method combining radially aligned near-conductor two-sensor differential electric-field measurement with three-dimensional electrostatic finite-element modelling. The differential electric field between two radial sensing positions is used for voltage inversion, which suppresses distant common-mode interference. When a nearby interference conductor exists, a weighted differential correction coefficient k is introduced to compensate for the residual radial interference component. Theoretical and simulation results show that k is a scenario-dependent coefficient affected by the measured voltage, sensor spacing, interference voltage, and geometric configuration. In an ultra-high-voltage (UHV) converter valve bridge-arm scenario with a 400 kV interference conductor, the absolute voltage inversion error is reduced from 0.50–1.57% FS before correction to below 0.20% FS after correction. Experiments on a 30 kV-scaled platform further verify the method under different measured voltages, sensor spacings, and interference-voltage levels, with the best-tested case reducing the maximum error from 0.93% FS to 0.16% FS.