Xu Zhirong

Offshore wind resouce assessment based on WRF model

In order to avoid investment risks of offshore wind farms, offshore wind resources is necessary to conduct a detailed assessment. At the current lack of offshore wind resource assessment data and formulas in the sea applicability is not clear, this paper discusses a numerical weather WRF model for offshore wind resource assessment methodology. The assessment summarized here consists of three steps:(1)through the WRF data get wind speed sequence and wind speed probability distribution, (2) through the measured data get from the wind tower correct formula used for onshore wind resource assessment, then extrapolated to sea, (3)a detailed assessment include the wind power density and annual generation capacity. In this paper, a practical example with the use of new methods and evaluation methods based on wind tower data were compared and found that the results of the evaluation are given no significant difference. Finally, the conclusion are: In the absence of measured data in the case, based on the WRF model for offshore wind resources can be effectively evaluated.

Research on nonlinear phenomena of single-phase H-bridge inverter

In this paper, the bifurcation and chaos in the operation of H-bridge inverter modulated by bipolar SPWM is studied. The one-dimensional discrete iterated mapping model under proportional control is established. Effects of the input voltage E on the system performance are analyzed by using bifurcation diagram, folded diagram. The time-domain waveforms with different proportional coefficients are obtained by Mat-lab/Simulink, which verify the correctness of theoretical analysis. Finally, the nonlinear behavior in the inverter caused by the variation of other circuit parameters like proportional coefficient k, load resistance R, and inductance L is investigated through bifurcation diagrams. The results have important guiding significance and application value for designing and debugging the single-phase H-bridge inverter.