分析了单相光伏并网发电系统的工作原理,对比了被动式和主动式孤岛检测方法的优缺点,同时为了有效地抑制电网波动对输出电流的影响,研究了带电压前馈的主动频率扰动法孤岛效应检测方法.在MATLAB/SIMULINK下进行了系统的建模与仿真,基于S函数编写控制算法.仿真结果表明输出并网电流波形良好,与电网电压同频同相,在三个周期内有效地检测出了系统的孤岛效应,满足孤岛检测标准要求.%A novel license plate character segmentation algorithm based on wavelet transformation and feedback is proposed in this paper. Firstly, image preprocessing is used for the license plate. Secondly, vertical projection is applied to rough segmentation of the plate characters. Finally, two - level feedback is used for fine segmentation of the plate characters. The first level feedback is the feedback of the character count and single character width, and the second level feedback is the character recognition feedback. In the stage of character recognition feedback, wavelet transformation of the vertical projection of each character region image is performed; and then the vertical projections are reconstructed by the low frequency coefficients. Finally, the character recognition based on the texture feature is implemented. The experimental results show that the proposed algorithm has good character segmentation performance for degraded number plates.
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