电网的分散负荷安全域及其应用(一):电网静态安全的线路负荷安全域

Distributed Load Security Domain and Its Application(Ⅰ):Line Load Security Domain for Grid Static Security

维持多电压等级(简称多级)电网全局电压安全与静态功-角稳定的分散线路功率约束问题,分析困难、现有理论依据不足。研究发现,多级电网的电压幅值呈"锯齿分布"特征,维持全网电压安全水平的关键是限制各线路的压差;前期研究得到的线路负荷安全域,对线路压差约束起主导作用。进一步研究发现,线路的允许压差、负荷安全域大小和域内最大功角,三者对应且近似呈正比关系;无论何种拓扑形式,各级电网中的有功路径最大功角取决于该级电网内的允许压差;但维持允许压差的线路负荷安全域约束,可能导致多级电网有功路径的功角超限,不满足静态功-角稳定的充要条件。故提出了线路负荷安全域的修正方法:如考虑负荷功率因数、采用串联阻抗或分配线路限制压差等方法缩小安全域。验算表明,修正后的线路负荷安全域,在约束安全压差的同时,还可满足多级电网的静态功-角稳定要求。该局部功率约束条件,可广泛应用于全网优化控制、分散安全控制和网架、无功规划等,具有理论和实际价值。

The problem of distributed power constraint of lines to maintain the global voltage security and static power-angle stability of multiple voltage level(multi-level for short)power grid is difficult to analyze and lacks sufficient theoretical basis.The analysis found that the voltage amplitude of multi-level grid has a"sawtooth distribution"characteristic,and the key to maintaining the global grid voltage safety level is to limit the voltage differential of each line.The line load security domain obtained in the previous study plays a leading role in restraining the voltage difference of lines.Further research found that the allowable pressure difference of the line,the size of load safety domain,and the maximum power angle in the domain correspond to each other and approximately proportional.Regardless of the topology,in each level of power grid,the maximum power angle of the active path depends on the allowable voltage difference;but due to the lines load security domain constraint of maintaining the allowable voltage difference,the power angle of the active power path in the multi-level grid may exceed the limit,which does not meet the necessary and sufficient condition for static power-angle stability.Therefore,the correction methods for the safety zone of the line load were proposed.For example,considering the load power factor,using series impedance or distributing the line can limit the voltage difference to reduce the safety zone.Checking calculations show that the revised line load security domain can meet the static power-angle stability requirements of multi-level power grids while constraining the safety pressure difference.This local power constraint can be widely used in global optimization control,decentralized safety control,grid and reactive power planning,etc.It has great theoretical and practical significance.