Harmonics and conducted electromagnetic interference (EMI) are two main issues in grid-connected inverter system. In this article, a modified LCL-LC harmonic filter is structured to strengthen its EMI suppression ability. Considering the common mode and differential mode EMI propagation paths, the traditional LCL-LC filter is split into a symmetrical topology, and with the midpoint of the split filtering capacitors connected to the midpoint of the dc-link capacitor. Compared to the traditional LCL-LC filter, the modified one can maintain the satisfied harmonic attenuation ability and strengthen the EMI suppression. Also, a double closed-loop control strategy is employed to solve the severe resonance problem caused by the harmonic filter. Moreover, a system calibration method is proposed and introduced to design the controller parameters to improve the high-order grid-connected system's stability. A comprehensive analysis and discussions concerning the traditional and modified LCL-LC filters are conducted in simulation and experiment on a 2 kW/220 V/50 Hz single-phase grid-connected inverter. The results have verified the feasibility of the proposed design method, and shown the superiority of the modified LCL-LC filter and active damping strategy in EMI mitigation. Besides, the weight and volume of the harmonic filter can be significantly reduced through this strategy.

中文翻译：

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使用改进的谐波滤波器设计降低单相并网逆变器的 EMI 噪声

谐波和传导电磁干扰 (EMI) 是并网逆变器系统中的两个主要问题。在本文中，修改了拼箱谐波滤波器的结构增强了其 EMI 抑制能力。考虑共模和差模 EMI 传播路径，传统的拼箱滤波器被分成对称拓扑，并且分裂滤波电容器的中点连接到直流母线电容器的中点。与传统相比拼箱滤波器，改进后的滤波器可以保持满意的谐波衰减能力并加强EMI抑制。此外，采用双闭环控制策略来解决谐波滤波器引起的严重谐振问题。此外，提出并引入了一种系统标定方法来设计控制器参数，以提高高阶并网系统的稳定性。传统与改良的综合分析与探讨拼箱滤波器在 2 kW/220 V/50 Hz 单相并网逆变器上进行仿真和实验。结果验证了所提设计方法的可行性，并展示了改进方案的优越性。拼箱EMI 缓解中的滤波器和有源阻尼策略。此外，通过这种策略可以显着减少谐波滤波器的重量和体积。