Search

In this paper, a model of the Kelvin probe is established in COMSOL Multiphysics based on electrostatic field theory, and it is verified by measuring the surface potentials. The influence of the probe is also investigated. An improved charge inversion method based on surface potentials measured online is proposed. The surface charge density is directly obtained by the Gauss's theorem to avoid the calculation of the inversion matrix. The improved method is verified by comparing the surface charge density calculated by the analytical method. When considering the effect of the probe, the maximum difference in surface charge density is 0.3 µC/m2 comparing to that when ignoring its effect, and the percentage of the difference is as high as 41%. The results indicate that the effects of the voltage of the probe under online measurement conditions must be considered.

The conversion system is a major contributor to failure rates. These faults lead to time and cost consuming. Fault diagnosis capabilities pay as a solver to achieve a steady system. This paper presents a full analysis of permanent magnet synchronous generator wind system (PMSGWS) and proposes a special RMS voltage-based fault diagnosis method. The full analysis presents a comprehensive knowledge of faulty behaviors especially under arm current flowing or cutting off. Due to enough knowledge of faulty behaviors, the implementation of the detection method without threshold setting is contributed by the special RMS voltage. Its sample period is set longer than the time of the maximum pulse width ratio (MPR) and shorter than the fault show time of lower tube voltage. Due to this, the detection speed and robustness are achieved. By these simple settings for the fault diagnosis method, the faulty switch is detected in less than 1/4 of the period. Simulation and experimental results confirm the validity and feasibility of the new proposed fault detection method.