并联电容投切对孤立系统低频减载设计的影响

EFFECT OF SHUNT CAPACITOR SWITCHING ON UFLS DESIGN FOR ISOLATED SYSTEM

进行系统低频减载方案设计时 ,简单的频率响应模型由于未考虑系统电压对频率过程的影响而导致不少情况下无法适用。文中针对孤立小受端系统 ,通过仿真表明在大有功缺额扰动下此类系统极易出现低电压问题 ,从而很大程度上影响了频率行为 ,并影响了低频减载装置的动作。通过比较不同的并联电容投切模式对频率过程的影响 ,提出了合理抑制电压升高基础上的更为合理的减载方案 ,以更有效地恢复系统频率和电压。

During the design of under frequency load shedding (UFLS) schemes, some simple models for frequency dynamics analysis are obviously inadequate since they do not take system voltage into account. Especially for the small isolated receiving power systems, simulation results have shown that such systems will suffer from voltage problems which will affect the frequency behavior and furthermore the action of UFLS utilities. After the comparison between different capacitor switching modes following the load shedding, a more reasonable scheme, which will depress the increased voltage by suitable capacitor switching, is derived to restore system frequency and voltage more effectively. Some practical problems are also presented for implementation.