Along with environmental consciousness enhancement, conventional energy depletion, wind energy exploitation is expanding gradually due to the renewable merit, clean without any pollution and vast reserve features. Therefore, wind power generation (WPG) system equipped with Doubly Fed Induction Generators is emerging as mushroom. Larger rated capacity of power unit, the higher tower and the variable pitch are the main scope in WPG system. However, latent trouble will bring about likewise. If a fault occurred, it will be catastrophic for WPG system. Consequently, the technology of fault detection will play a more important role in WPG system. Based on the present status, a novel method is proposed in this paper after summarizing and analyzing the lack of previous methods. Then an example for detecting the inverter fault is studied using PSCAD software. Results indicated that the proposed method is effective and feasible.
The compensation current of the arc-suppressing coil makes the phase and amplitude of zero-sequence measurement current of the earthed fault feeder to vary. It is very hard to detect the fault feeder by using existing detectors based on single method. In this paper, integrative feeder selection strategy-zero sequence current increment method and the direction of transient current-is put forward. Based on the integrative feeder selection strategy, the design of fault-feeder selection device for one-phase-to ground fault on resonance grounding system is presented. For the purpose of testing and validating the operating principle of the device, the experiment of single-phase-to-ground fault has been carried out on the simulation of 1.2 kV power network. The results from many repeat experiments show that stability of the fault selection device is satisfactory.
In this study, the performance of AlN (0001)/Hf (0001) interface, such as occupation characteristics and combined energy, were studied by using the first principles calculation package. In the AlN/Hf interface, the Al- and N-terminated interfaces have three stacking sites each (outermost top site, sub-outer top site, and hexagonal close-packed hollow site), comprising six different models. The most adhesion work occupies the N-terminal interface of the hcp-hollow site, and the interface energy was also the smallest and most stable, as well as a lower fracture work than the AlN/Ti interface. Moreover, the differential charge density were calculated, the partial density of states were plotted, and the bonding properties were discussed. Compared with other interfaces, the N-terminated interface with the hcp-hollow site exhibited more covalent characteristics; on the Al-terminated interface with the sub-outer top site, the Hf-Al metallic bond was formed. The most stable atomic occupation type in AlN/Hf interface is the hcp-hollow site of N atomic terminal.
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