Harmonic Current and Inrush Fault Current Coordinated Suppression Method for VSG Under Non-ideal Grid Condition

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Abstract
For VSG, the voltage-controlled harmonic-suppression-method will seriously deteriorate the magnitude of inrush fault current in the moment of grid symmetrical fault, because the suppression effects of harmonic current and inrush fault current are mutually constrained from the perspective of its output impedance. For this issue, a harmonic current and inrush fault current coordinated suppression method is proposed to achieve both good results of harmonic current suppression in normal grid and inrush fault current limitation in fault grid, which mainly includes a passive branch, an active branch and an improved VSG control. The passive branch is installed between PCC and grid to introduce an additional voltage variable. Meanwhile, with the proper feed-forward of PCC voltage and additional voltage, the active branch increases the mid/high frequency impedance viewed from grid fault point to VSG, and decreases harmonic impedance viewed from PCC to VSG. Then, not only transient inrush fault current is limited, but also harmonic current introduced from nonlinear load is mostly absorbed. Moreover, the improved VSG control is used to limit steady-state fundamental frequency fault current. Therefore, the contradictory between harmonic current and inrush fault current suppression for VSG is well solved. Finally, the experiment results validate the proposed control method.
Funding Information
  • Fundamental Research Funds for the National Natural Science Foundation of China (51707061)
  • Central Universities (531118010260)
  • Hunan Natural Science Foundation Funded (2018JJ3048)
  • Postdoctoral Innovative Talent Support Program of China (BX20190109)

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