基于功角限制的虚拟同步调相机励磁方案以增强暂态惯性支撑能力

The AC-excitation Synchronous Condenser (AC SynCon), which combines the advantages of doubly-fed machines and flywheel energy storage, has recently attracted attention as a solution to provide both frequency and voltage support to weak grids. The deployment of emerging grid-forming control strategies allows the AC SynCon to provide a swift reactive power response and a strong inertia support comparable to conventional SynCon. Nevertheless, the active power instability risk associated with the AC SynCon in conjunction with a conventional overcurrent protection may potentially degrade the performance of the AC SynCon during significant grid disturbances. This paper presents a virtual synchronous condenser (VSC) excitation scheme for the AC SynCon and addresses the aforementioned instability mechanism. By introducing Virtual Power Angle (VPA) limitation, the proposed excitation scheme enables the AC SynCon to provide enhanced transient inertia support and avoids the instability risk. Furthermore, a discussion of the combined effect of reactive power support and the proposed method, as well as a detailed calculation of the VPA limitation under different grid conditions, is presented. The effectiveness of the proposed method is validated through case studies conducted on the MATLAB simulation platform, with further support provided by experimental results on a 5.5 kVA prototype. The results demonstrate that with the proposed control method, the AC SynCon could provide a strong and stable inertia support during grid frequency drop occasions.