An improved zero-voltage-switching (ZVS) phase-shift full-bridge converter with self-regulating auxiliary current is proposed. ZVS of lagging-leg switches can be achieved in whole conversion range because of the introduced active auxiliary circuit. Meanwhile, the auxiliary circuit that features simple control of the auxiliary switches has no effect on the main power transferring path and the auxiliary energy stored for ZVS of lagging-leg can be regulated by the load current without significantly increasing conduction loss over the entire load range. The operation principle of the proposed converter is discussed in detail and further simplification of the proposed topology is suggested. The design method of key parameters is carefully depicted. Finally, the operation and performance of the proposed converter are verified on a 1 kW/54 V, 100 kHz prototype.
Accurate underwater gas pipeline leak localization requires particular attention due to the sensitivity of environmental conditions. Experiments were performed to analyze the localization performance of a distributed optical fiber sensing system based on the hybrid Sagnac and Mach-Zehnder interferometer. The traditional null frequency location method does not easily allow accurate location of the leakage points. To improve the positioning accuracy, the particle swarm optimization algorithm (PSO) tuning of the support vector machine (SVM) was used to predict the leakage points based on gathered leakage data. The PSO is able to optimize the SVM parameters. For the 10 km range chosen, the results show the PSO-SVM average absolute error of the leakage points predicted is 66 m. The prediction accuracy of leakage points is 98.25% by PSO tuning of the SVM processing. For 20 leakage test data points, the average absolute error of leakage point location is 124.8 m. The leakage position predicted by the PSO algorithm after optimization of the parameters is more accurate.
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