采用SVC抑制次同步谐振的机理分析

针对采用静止无功补偿器（SVC）抑制次同步谐振（SSR）的核心问题，即如何提供与扭振模态频率互补的电流分量问题，提出了SVC基波电纳次同步调制的控制机理和数学模型。分析表明:对SVC基波电纳参考值进行次同步频率调制，可控制其输出大小和相位适当的模态互补频率电流，进而在机组中产生对应模态的阻尼扭矩，达到抑制SSR的目的。这一控制机理同时会导致SVC输出超同步和复杂分数次谐波分量。基于详细电力电子电路的非线性电磁仿真和实际SVC设备试验均验证了控制机理和数学模型的有效性和正确性，进一步将所提出的控制机理应用于锦界电厂串补输电系统的SSR问题，数值仿真结果证实了其有效性。

Mechanism Study on the Mitigation of SSR with SVC

The core issue of depressing subsynchronous resonance(SSR) with static var compensator(SVC) is to make its current output contain components of complementary frequencies to torsional modes of the turbine-generator shaft.For this purpose,the control principle and mathematical model of subsynchronous modulation of fundamental admittance for SVC are proposed.Theoretical analysis shows that by subsynchronously modulating the reference value of SVC's fundamental admittance with appropriate amplitude and phase,the generated current components of the complementary frequencies can be controlled to generate damping torque and realize the SSR-damping objective.The proposed control scheme meanwhile results in supersynchronous as well as other fractional harmonic currents.Both nonlinear electromagnetic simulations with the detailed power-electronic circuit and field tests on the actual SVC equipment validate the proposed control scheme and mathematical model.The subsynchronous damping control system is further applied to a practical system threatened by SSR,i.e.,the Jinjie series-compensated transmission project.Extensive digital simulations have demonstrated its effectiveness in mitigating multi-modal SSR.