基于近似连续潮流的在线电压稳定分析

On-line Voltage Stability Analysis Based on Approximate Continuation Power Flow

提出近似连续潮流算法以实现电压稳定的在线监视,该算法由预测算法和校正算法2部分组成。其中,预测算法线性化潮流方程,并以一个切线预报来预测其下一个步长状态变量的数值;校正算法则将预测值代入潮流方程,进而求得负荷的计算增长方向。为了减小负荷增长方向和计算增长方向的偏差,每一个步长的预测计算均回到负荷增长的调整方向,并依次反复迭代,直到负荷增长方向与计算增长方向的夹角大于给定值,此时表明潮流方程的线性程度显著恶化,从而得到负荷裕度的近似值。进一步给出了近似连续潮流算法为连续潮流算法线性近似的严格数学证明。该算法不存在潮流方程的收敛问题,计算速度快,所求得的电压稳定指标线性程度好,物理意义明确。IEEE39节点的算例证明了算法的有效性。

A novel approximate continuation power flow algorithm is presented to realize voltage stability on-line monitoring. The method consists of two stages, viz. prediction and correction. The prediction algorithm linearizes power flow equations and predicts next step power flow solution along its tangent direction. The correction algorithm obtains calculative load increase direction by substituting the prediction solution into power flow equations. The algorithm uses the adjusted direction to predict power flow solution of next step, which can decrease the angle between load increase direction and calculative load increase direction. It is iterated until the angle is greater than a given value, which means that the linearization degree of power flow equation is deteriorated and the approximate load margin is obtained. Furthermore, in order to show the validity of the new algorithm in analyzing voltage stability, a strict mathematic proof is presented to show that this algorithm is linearization approximation of continuation power flow. The algorithm has a fast calculation speed and no convergence problem. Its voltage stability index has explicit physical meaning and good linearization property. Case studies using the IEEE 39-bus system are given to prove the effectiveness of the proposed algorithm.