Because traditional electronics cannot directly use the alternating output voltage and current provided by electric field energy harvesters, harvesting systems require additional regulating and conditioning circuits. In this field, this work presents a conditioning circuit, called serial switch-only rectifier (SSOR) for low-voltage electric field energy harvesting (EFEH) applications. The proposed approach consists of a tubular topology harvester mounted on the outer jacket of a 230 V three-wires electrical cable (neutral, ground, and phase), in which terminals are connected to SSOR. We compare SSOR performance with classic electronic approaches, such as a full-bridge rectifier and voltage doubler. Experimental findings showed that the gathered energy by a 1 m cylindrical harvester increased in approximately 73.3% using the SSOR as a power management circuit. Experimental findings showed that the gathered energy by a 1 m cylindrical harvester increase in approximately 73.3% using the SSOR as a power management circuit. This increase is principally due to the fact that a serial bidirectional switch disconnects the harvester from the rest of the management circuit, enhancing the charge collection process. Although simulated results disclosed that SSOR increased collected energy for smaller-scale harvesters (experimental tests obtained using a 10 cm cylindrical harvester), additional losses in bidirectional switch reduced its performance. In addition, we introduce a comprehensive analysis of EFEH systems based on SSOR according to the mains frequency for future power systems.
The use of phase cross correlation is proposed to estimate the frequency shift of the Rayleigh intensity spectral response in frequency-scanned phase-sensitive optical time-domain reflectometry (φ-OTDR). Compared with the standard cross correlation, the proposed approach is an amplitude-unbiased technique that evenly weights all spectral samples in the cross correlation, making the frequency-shift estimation less sensitive to high-intensity Rayleigh spectral samples and reducing large estimation errors. Using a 5.63-km sensing fiber with 1-m spatial resolution, experimental results demonstrate that the proposed method highly reduces the presence of large errors in the frequency shift estimation, increasing the reliability of the distributed measurements while keeping the frequency uncertainty as low as approximately 1.0 MHz. The technique can be also used to reduce large errors in any distributed Rayleigh sensor that evaluates spectral shifts, such as polarization-resolved φ-OTDR sensors and optical frequency-domain reflectometers.
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