A two-stage algorithm is proposed for the estimation of the fundamental frequency of asynchronously sampled signals in power systems. In the first stage, time-domain interpolation reconstructs the power system signal at a new sampling time and the reconstructed signal passes through a tuned sine filter to eliminate harmonics. In the second stage, the fundamental frequency is estimated using a modified curve fitting, which is robust to noise. The evaluation results confirm the efficiency and validity of the two-stage algorithm for accurate estimation of the fundamental frequency even for asynchronously sampled signals contaminated with noise, harmonics, and an inter-harmonic component.

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The present study has been conducted to verify and enhance the MTBF of the diaphragm gas meter. The goals of this study were the development of acceleration test method for the diaphragm gas meter and the guarantee of B10 lifetime of 3000 h in normal operation condition. To develop the acceleration test method, the flow rate and the operation temperature were chosen as acceleration factors and experiments of 1000 h in four conditions are conducted. The results showed that the log-normal life distribution conforms to the diaphragm gas meter life distribution and the combination of the temperature and the flow rate can have the acceleration factor of up to 3.48. The uncertainty of the flow rate accuracy verification is 0.20% and the log-normal life distribution is used.