【目的】为提升电网中高比例电力电子设备条件下的次同步振荡抑制能力，推进连续可调式移相器在电网潮流调节与振荡抑制方面的应用，明确其振荡抑制机理并提升其振荡抑制性能。【方法】首先解析了连续可调式移相器所在线路中次同步振荡、线路电流及移相器各参数间的量化关系，并利用这一关系刻画了其振荡抑制性能边界，揭示了移相器自身振荡抑制能力的局限性。然后，提出了一种计及次同步调制信号的增强型多频调制策略。为进一步拓宽移相器的振荡抑制性能边界，并避免谐波污染，提出了电容串补型移相器，同时给出了串补电容的设计方法；最后，为解决其伴生的潮流反转问题，提出了一种开-闭环融合的潮流调节策略。【结果】增强型多频调制策略可将次同步振荡降低至10%左右，但同时会造成一定的谐波污染，降低电能质量；基于传统、增强型多频调制策略及串补电容的可调移相器振荡抑制能力对比验证了传统移相器抑制能力的局限性和电容串补型移相器在提升抑制性能方面的优越性。【结论】所提增强型多频调制策略有效提升了振荡抑制能力，但存在谐波污染问题；电容串补型移相器不仅能够通过控制串联电压调节电网潮流，而且可以提供与振荡源反相的同频电压来抑制次同步振荡，在拓宽振荡抑制性能边界的同时避免了谐波污染，为电网次同步振荡抑制提供了新的技术路径。

[Objective] To enhance the sub-synchronous oscillation suppression capability under high proportion of power electronic equipment conditions in power grids， promote the application of continuous tunable phase shifters in power flow regulation and oscillation suppression， clarify their oscillation suppression mechanism and improve their oscillation suppression performance. [Methods] This paper first analyzes the quantitative relationship among sub-synchronous oscillation， line current and phase shifter parameters in the line where the continuous tunable phase shifter is located， and uses this relationship to characterize its oscillation suppression performance boundary， revealing the limitations of the continuous tunable phase shifter's own oscillation suppression capability. Subsequently， an enhanced multi-frequency modulation strategy considering sub-synchronous modulation signals is proposed. To further broaden the oscillation suppression performance boundary of the continuous tunable phase shifter while avoiding harmonic pollution， a series capacitor compensated continuous tunable phase shifter is proposed， and the design method for series compensation capacitor is provided； additionally， to solve the accompanying power flow reversal problem， an open-closed loop integrated power flow regulation strategy is proposed. [Results] Simulation results show that the enhanced multi-frequency modulation strategy can reduce sub-synchronous oscillation to approximately 10%， but simultaneously causes certain harmonic pollution and reduces power quality； the comparison of oscillation suppression capabilities of tunable phase shifters based on traditional， enhanced multi-frequency modulation strategies and series compensation capacitor verifies the limitations of suppression capability of traditional continuous tunable phase shifter and the superiority of series capacitor compensated continuous tunable phase shifters in improving suppression performance. [Conclusions] The proposed enhanced multi-frequency modulation strategy effectively improves oscillation suppression capability but has harmonic pollution issues； the series capacitor compensated continuous tunable phase shifter can not only regulate grid power flow by controlling series voltage， but also provide same-frequency voltage with opposite phase to the oscillation source to suppress sub-synchronous oscillation. This broadens the oscillation suppression performance boundary while avoiding harmonic pollution， providing a new technical approach for power grid sub-synchronous oscillation suppression.