Impedance Shaping of the Grid-Connected Inverter with LCL Filter to Improve Its Adaptability to the Weak Grid Condition
Impedance Shaping of the Grid-Connected Inverter with LCL Filter to Improve Its Adaptability to the Weak Grid Condition
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DOI：
10.1109/tpel.2014.2300235
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发表时间：
2014-01
影响因子：
6.7
通讯作者：
Dongsheng Yang;X. Ruan;Heng Wu
中科院分区：
文献类型：
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作者：
Dongsheng Yang;X. Ruan;Heng Wu
带LCL滤波器的电流控制并网逆变器由于其动态响应快、电能质量好等特点，在分布式发电系统中得到了广泛的应用。然而，随着电网注入功率的增加，非理想电网条件会对逆变器的控制性能产生显著影响。具体来说，电网阻抗可能的大变化对系统的稳定性提出了挑战。同时，电网的背景谐波会极大地扭曲注入电流。因此，逆变器的控制设计应具有较强的稳定鲁棒性和较高的抗谐波能力，这两者与逆变器的输出阻抗密切相关。然而，仅通过调整电流环路增益很难将输出阻抗塑造成具有理想特性的输出阻抗。本文提出了一种基于虚拟阻抗的阻抗整形方法，该方法可以独立设计电流控制回路。从实际出发，研究了虚拟阻抗的实现和参数设计。采用该方法，并网逆变器可以在较宽的典型电网电感电阻阻抗范围内稳定工作，并具有较强的抗电网电压谐波能力。在一台6kw单相并网逆变器上的实验结果证实了该方法的有效性。
The current-controlled grid-connected inverter with LCL filter is widely used in the distributed generation system (DGS), due to its fast dynamic response and better power quality features. However, with the increase of power injected into the grid, control performances of the inverter will be significantly influenced by the nonideal grid conditions. Specifically, the possible wide variation of the grid impedance challenges the system stability. Meanwhile, background harmonics of the grid can greatly distort the injected current. Therefore, the control of the inverter should be designed with strong stability-robustness and high harmonic-rejection-ability, both of which correlate closely with the inverter output impedance. However, it is difficult to shape the output impedance into the one with a desirable characteristic simply by adjusting the current loop gain. In this paper, an impedance shaping method is proposed with virtual impedances, and the current control loop can be designed independently. The implementation and parameter design of the virtual impedances are studied under the practical considerations. With this proposed method, the grid-connected inverter can work stably over a wide range of the typical inductive-resistive grid impedance and exhibit strong rejection ability of grid-voltage harmonics. Experimental results from a 6-kW single-phase grid-connected inverter confirm the effectiveness of the proposed method.