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Improved Control of Grid-connected Converter with LCL Filter Based on Phase Compensation and Virtual Impedance Optimization
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Affiliation:

1.National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China;2.Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing 100044, China;3.State Key Laboratory of Control and Operation of Renewable Energy & Storage Systems;(China Electric Power Research Institute), Beijing 100192, China

Fund Project:

This work is supported by National Key R&D Program of China (No. 2018YFB0905200).

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    Abstract:

    The grid-connected control based on inductor current on the side of converter in synchronous rotating coordinate system is widely applied in the grid-connected converter with LCL-filter. However, the axe-cross-coupling exist in the dq models of LCL filter and digital delay, which constrains the grid-connected performance and becomes worse as the switching frequency decreases. To address this issue, based on the complex vector modeling of grid-connected converter with LCL-filter, this paper analyzes the coupling characteristics of the grid-connected converter and the conventional decoupling scheme. Aiming at the shortcomings of the existing control strategies, this paper proposes an improved control strategy of the grid-connected converter with LCL-filter based on phase compensation and virtual impedance optimization. Then, the effect of virtual impedance on system coupling and system damping characteristics is analyzed in detail through the zero-pole plots. And the method for determining optimization values of three parameters are given. Finally, the simulation and experimental results show that the proposed strategy can achieve independent control of system coupling degree and damping characteristics, while effectively realize decoupling and improve system dynamic performance.

    表 2 Table 2
    表 3 Table 3
    图1 LCL型并网变流器拓扑Fig.1 Topology of grid-connected converter with LCL filter
    图2 同步旋转坐标系下的控制框图Fig.2 Control block diagram in synchronous rotating coordinate system
    图3 系统复矢量模型图Fig.3 Diagram of complex vector model of the system
    图4 改进并网控制Fig.4 Improved grid-connected control
    图5 R和X变化时的零极点图Fig.5 Pole-zero plot with the variation of R and X
    图6 实验波形图Fig.6 Experimental waveforms
    图 θ B+θ C 相位补偿控制框图Fig. Control diagram of phase compensation by θ B+θ C
    图 实验平台图Fig. Diagram of prototype
    图1 LCL型并网变流器拓扑Fig.1 Topology of grid-connected converter with LCL filter
    图2 同步旋转坐标系下的控制框图Fig.2 Control block diagram in synchronous rotating frame
    图3 系统复矢量模型图Fig.3 Diagram of complex vector model of the system
    图4 改进并网控制Fig.4 Improved grid-connected control
    图5 R和X变化时的零极点图Fig.5 Pole-zero plot with changed R and X
    图6 实验波形图Fig.6 Experimental waveforms
    表 1 不同情况下的系统带宽及相位裕度Table 1 System bandwidths and phase margins in different scenarios
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GAO Yinghan,TANG Fen,LIU Jingdou,et al.Improved Control of Grid-connected Converter with LCL Filter Based on Phase Compensation and Virtual Impedance Optimization[J].Automation of Electric Power Systems,2020,44(3):167-175.DOI:10.7500/AEPS20190330002

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History
  • Received:March 30,2019
  • Revised:July 17,2019
  • Adopted:
  • Online: February 14,2020
  • Published: