【目的】针对双高电力系统下电网强弱交替导致传统单一跟网型(GFL)或构网型(GFM)控制难以适配的问题,提出一种基于电网阻抗辨识的GFL/GFM切换控制策略。【方法】采用基于特定频次谐波提取的电网阻抗辨识技术监测电网强度并确定短路比(SCR);设置迟滞切换环节,当SCR<2时采用GFM控制,当SCR>3时采用GFL控制,当2≤SCR≤3时保持原控制模式运行,避免临界区间频繁切换。通过稳态工作点预匹配策略补偿功率参考值与虚拟励磁初值,消除模式切换时的瞬态冲击,并通过Matlab/Simulink进行仿真验证。【结果】在强弱电网交替变化过程中,所提策略能够根据在线辨识结果完成GFM与GFL控制的双向切换,切换瞬间公共耦合点电压无明显阶跃,电流仅出现短时扰动并能快速恢复稳态,有功、无功功率无持续振荡。与不同切换方法的对比结果进一步表明,稳态工作点预匹配能够减小切换过程中的电流冲击,使模式过渡更加平滑。【结论】该策略融合了GFL与GFM控制的技术优势,其能够根据电网强度变化实现GFL/GFM切换控制,并通过稳态工作点预匹配降低模式切换过程中的电压、电流和功率冲击,提高储能变流器在强弱电网动态变化条件下的运行适应性和切换稳定性。

[Objective] To address the problem that traditional single grid-following (GFL) or grid-forming (GFM) control is difficult to adapt to under alternating strong and weak grid conditions in doubly-high power systems, a grid impedance identification-based GFL/GFM switching control strategy is proposed. [Methods] Grid strength was monitored and the short-circuit ratio (SCR) was determined by using a grid impedance identification technique based on specific harmonic extraction. A hysteresis switching loop was set up: GFM control was adopted when SCR was less than 2, GFL control was adopted when SCR was greater than 3, and the original control mode was maintained within 2≤SCR≤3 to avoid frequent switching in the critical interval. Transient impacts during mode switching were eliminated through a steady-state operating point pre-matching strategy, which compensated the power reference values and initial virtual excitation values. Finally, simulation verification was carried out using Matlab/Simulink. [Results] During the alternating variation of strong and weak grid conditions, the proposed strategy accomplished bidirectional switching between GFM and GFL control based on online identification results. At the switching instant, no significant step occurred in the point of common coupling voltage, and the current only exhibited short-term disturbance before rapidly recovering to steady state, with no sustained oscillation in active and reactive power. Comparison results with different switching methods further indicated that steady-state operating point pre-matching mitigated current impacts during the switching process and rendered the mode transition smoother. [Conclusion] This strategy integrates the technical advantages of GFL and GFM control. It can realize GFL/GFM switching control according to changes in grid strength, and reduces the voltage, current, and power impacts during mode switching through steady-state operating point pre-matching, thereby improving the operational adaptability and switching stability of the power conversion system under dynamically varying strong and weak grid conditions.

国家自然科学基金(52377191);湖北省自然科学基金(2024AFB584)