全国电网互联系统频率特性及低频减载方案

Study on Dynamic Frequency Characteristics and Coordinative Under-Frequency Load Shedding Scheme for Nationwide Interconnected Power Grid of China

目前我国已形成东北-华北（含山东）-华中（含川渝）跨区同步互联电网。采用电力系统暂态稳定时域仿真程序和自动低频减负荷方案设计了单机计算模型，全面分析和评价了各种联网或孤网运行模式下发生大功率缺额时，电网频率暂态稳定特性及各电网现有低频减载方案对2005-2007年电网频率安全运行的适应性。在此基础上提出了我国东北-华北-华中跨区互联电网统一协调的低频自动减负荷方案，该方案不但适用于各种联网模式，也适用于各种孤网模式。当受到5％-45％的不同功率缺额扰动时，互联电网能够相应地协调减负荷，保证了最小频率不低于48．0Hz，满足频率恢复速度10S左右恢复到49．5Hz，达到了统一协调减载，保证系统频率稳定和联络线及大机组安全。

At present an interareal synchronization interconnected power grid that consists of Northeast China power grid, North China power grid involving Shandong power system and Central China power grid involving Shichuan-Chongqing power grid is formed. By use of time-domain power system transient stability simulation program and automatic under-frequency load shedding （UFLS） scheme, a single-machine calculation model is designed, by which the transient stability characteristics of power system frequency under various interconnected operation modes or isolated operation mode as well as the adaptability of existing UFLS schemes adopted in various power grids to secure operation of power grid frequency from 2005 to 2007 are overall analyzed and evaluated while large amount of power shortage occurs. On this basis a coordinative UFLS scheme for above-mentioned interareal synchronization interconnected power grid is proposed, this scheme is not only suitable to different interconnection modes, but also to various isolated operation modes. When the disturbances of power shortages from 5% to 45% happen, the interconnected power grid can perform coordinative load shedding correspondingly to ensure that the lowest power frequency is not lower than 48.0Hz and power frequency can be recovered to 49.5 Hz within 10 seconds. Thus, the unified coordinative load shedding can be implemented, and system frequency stability as well as the security of tie-lines and large capacity units can be ensured.