No abstract

Membrane is the most important element of extrinsic Fabry-Perot interferometer sensors. Studying the relationship between working medium viscosity and membrane vibration characteristics are critical to the sensor design because the transformer oil viscosity will cause viscous loss during membrane vibration. The numerical investigation of membrane vibration characteristics in transformer oil is performed based on the finite element method. Besides, the effect of energy loss caused by viscosity is examined. It is firstly showed that the membrane has the highest sensitivity for the first-order vibration mode, and the transformer oil reduces the fundamental frequency by 60%. Subsequently, when viscosity and heat loss are considered, the amplitude is less than one-fifth of that without energy loss. The viscosity has a more significant effect on the velocity and temperature fields when the vibration frequency is close to the natural frequency. Finally, viscosity has a remarkable impact on the time domain response. Mechanical energy is converted into thermal energy during the vibration and the amplitude will gradually decrease with time. The effect of energy loss caused by viscosity on the membrane vibration characteristics is revealed, which would be important for an oil-immersed membrane design.

No abstract

With the increasing connecting of photovoltaic systems, the harmonic pollution in power grid is deteriorated. The evaluation of the harmonic emission levels for photovoltaic system is significant for harmonic mitigation. However, when the background harmonics are unstable, traditional evaluation methods have large calculation errors. To solve this problem, a method based on the relevant vector machine is proposed in this paper. Compared with the traditional vector machine based method, the novel one can reach a high calculation accuracy, even when the background harmonics is relatively unstable. The validity for our proposed method is verified by simulation analysis.

No abstract