ROBUST DELAY COMPENSATION STATEGY FOR LCL SINGLE-PHASE GRID-CONNECTED INVERTER UNDER WEAK GRID

Ding Xin; Shi Ruiqing; Xue Ruinan; Zheng Tianzhi; Kong Fannie; Chen Yanming

doi:10.19912/j.0254-0096.tynxb.2021-1595

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Acta Energiae Solaris Sinica ›› 2023, Vol. 44 ›› Issue (5) : 162-170. DOI: 10.19912/j.0254-0096.tynxb.2021-1595

ROBUST DELAY COMPENSATION STATEGY FOR LCL SINGLE-PHASE GRID-CONNECTED INVERTER UNDER WEAK GRID

Ding Xin^1,2, Shi Ruiqing³, Xue Ruinan¹, Zheng Tianzhi¹, Kong Fannie¹, Chen Yanming¹

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Abstract

Considering the digital control delay, the boundary frequency of the equivalent positive and negative damping zone of the traditional capacitor current feedback active damping （CCFAD） of LCL-type photovoltaic grid-connected inverter is f_s/6 （f_s, is the sampling frequency）. Under weak grid, the variation of grid impedance will cause the actual resonance frequency f_r shift, and if f_r>f_s/6, the robustness of the system will be threatened. In order to solve the above problem, an improved compensation strategy is proposed, the phase lag caused by digital control delay was compensated by adding a cascade lead phase compensator into the capacitor-current-feedback path, so the effective positive damping region was broadened to （0,f_s/3）. In addition, the grid connected current tracking performance was improved due to the proportional complex integral （PCI） controller in the current control loop. Simulation and experiment verify the feasibility of the proposed strategy. Compared with the traditional CCFAD, the proposed delay compensation strategy expands the effective damping region and enhances the robustness of the system.

Key words

PV power / grid-connected inverter / delay compensation / active damping / robustness / weak grid

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Ding Xin, Shi Ruiqing, Xue Ruinan, Zheng Tianzhi, Kong Fannie, Chen Yanming. ROBUST DELAY COMPENSATION STATEGY FOR LCL SINGLE-PHASE GRID-CONNECTED INVERTER UNDER WEAK GRID[J]. Acta Energiae Solaris Sinica. 2023, 44(5): 162-170 https://doi.org/10.19912/j.0254-0096.tynxb.2021-1595

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