改进的静态阻塞滤波器LC失谐故障保护原理

Improved principle of LC detuning protection for static blocking filter

静态阻塞滤波器（SBF）LC失谐保护采用计算电抗器与电容器电流比率（CR）作为判据,当电流中包含非周期性分量或次同步振荡分量时,CR的计算结果会出现波动。对波动原因进行了分析,分析结果表明由于电抗器与电容器电流幅值波动的程度不同,导致电流比率波动。提出电流比率的改进算法,通过差分运算将电抗器电流折算成等效的电容器电流代入电流比率计算公式。仿真结果表明,采用改进算法计算的电流比率受次同步振荡电流和非周期分量的影响较小,这提高了LC失谐保护的灵敏度,使得保护的延时定值可以由10-20 s缩短至0.5-2.0 s范围内。

The CR（Current Ratio） of reactor current to capacitor current is adopted as the criterion of LC detuning protection for static blocking filter,which may fluctuate when the currents contains SSO（Sub Synchronous Oscillation） or non-periodic components. Analysis shows that,the difference between reactor current fluctuation and capacitor current fluctuation causes CR fluctuation. An improved algorithm is proposed for CR calculation,which applies the difference operation to convert the reactor current to the equivalent capacitor current and then calculates CR. Simulative results show that the CR calculated by the improved algorithm is lightly influenced by SSO or non-periodic components,which improves the sensitivity of LC detuning protection and makes the time delay setting reduced from 10-20 s to 0.5-2.0 s.