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| Decoupled VSG frequency support method considering voltage control in flexible HVDC systems |
| DOI：10.19783/j.cnki.pspc.240785 |
| Key Words:VSC auxiliary frequency regulation VSG decoupling control voltage closed-loop regulation |
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| Abstract:Utilizing the potential frequency regulation capability of flexible HVDC systems can effectively support grid frequency stability. However, conventional frequency regulation methods reduce the tracking speed of reference power changes because of increased virtual inertia, and decrease voltage control stability margins, thereby weakening the system’s frequency support capability. To address this issue, a parameter decoupled virtual synchronous generator (VSG) strategy based on voltage control is proposed. First, the auxiliary frequency control of the converter station and conventional VSG control method are analyzed. A DC bus voltage is introduced, and a droop-based PI controller is used to regulate voltage deviations. Then, an improved active power loop (APL) control is proposed. It incorporates a low-pass filter and a feedforward loop to eliminate the inherent oscillation poles of the VSG, thereby decoupling the reference power tracking speed of the APL from the virtual inertia support capability provided by the VSG. Finally, the proposed strategy is simulated and validated using Matlab/Simulink. The results show that the proposed strategy enables independent control of virtual inertia and reference power tracking through two separate parameters, rendering the control approach more flexible. Additionally, it effectively enhances the frequency support capability of the converter station while ensuring excellent voltage control performance. |
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