并网逆变器网侧谐振信息的小波包提取方法
首发时间:2014-11-12
摘要:规模化并网逆变器在电网公共端并联易引起复杂的谐振现象,为了有效抑制该谐振,论文介绍了一种基于"检测-反馈-补偿"思路的系统控制结构。为了实现上述目标,首先需要实时准确地提取该谐振信息来为抑制措施提供基准。本文研究基于小波包变换的最大谐振信息实时提取技术,提出一种基于db4小波包的小波树优化分解与重构算法,在每一层分解后采用阈值判据判定小波频段、保持频段和置零频段,下一层分解时忽略保持频段的信息,仅对小波段分解。相比小波包完全分解算法,该优化算法可大幅降低分解重构过程的运算量且不损失谐振信息量,集合了小波分解运算量小和小波包分解精度高的优点,为小波包算法的实用化奠定了基础。最后,为了验证小波树优化算法的有效性,论文基于DSP+FPGA控制平台在含不同谐振信息情况下对算法进行了验证,实验表明优化算法可有效提取出最大谐振成分。
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Resonant Current Extraction Using Wavelet Packet Transform for Mass Grid-connected Inverters
Abstract:Mass grid-connected inverter paralleling with Point of Common Coupling will incur resonant. In order to restrict the resonant current, a control strategy based on "Extraction - Feedback - Compensation" is presented in this paper. For accomplishing this target, the resonant information has been timely and accurately extracted to provide the reference for compensation. An optimized resonant current extraction method is proposed in this paper which is an improved wavelet tree decomposition and reconstruction based on db4 wavelet packet. According to the characteristics of the resonant current, a criterion is determined to type wavelet band, hold-on band, and zeroing band, respectively, in each decomposition layer; then the hold-on bands are ignored in the next decomposition layer, and until the resonant component is decomposed out. Compare with all decomposing algorithm, the optimized algorithm can significantly reduce the computation without the loss of the resonant information. Finally, the validity of the proposed optimized method is verified by a DSP+FPGA controller in different resonant conditions.
Keywords: Mass grid-connected Resonant Wavelet packet Optimization
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