潮流计算中PV-PQ节点转换逻辑的研究

STUDY ON PV-PQ BUS TYPE SWITCHING LOGIC IN POWER FLOW COMPUTATION

详细地研究了潮流计算中的 PV-PQ 节点转换逻辑,指出潮流计算中因为节点类型识别错误引起的发散是系统失去电压稳定性的一种表现形式,它对应于约束诱导型电压崩溃现象。几种补逻辑的使用会导致潮流计算收敛于一个不稳定解。文中通过对一个实际系统算例和 IEEE 118 节点标准算例的数值试验说明了这一情况。并给出了潮流计算中要获得稳定解必须满足的稳定性条件的数学列式,说明了它与PV-PQ 转换逻辑的等价关系。最后指出了在基于连续潮流的电压稳定性评估中如果采用不合理的 PV-PQ 补转换逻辑将得到错误的结果。

A comprehensive investigation on bus PV-PQ type switching logic in power flow computation is carried out in this paper. Besides the power mismatches blow up, the frequent switching of some bus type is another kind of divergence to suffer. To remove this type of oscillation occurring on some buses in a power flow calculation, several complementary logics were used in references, but this kind of method may sometimes make the power flow converging to an unstable solution. Researches done by this paper show that failure in bus type identification may result in a kind of voltage instability corresponding to the limit induced bifurcation. Some numerical simulations on IEEE 118 bus test system and a practical power system have been carried out and the results support to explain this phenomenon. Based on a theoretical analysis, a set of inequality constraints describing stability conditions are defined as the necessary condition for a stable power flow solution. This paper gives an example to show that some wrong stability margins are obtained when an incorrect bus PV-PQ type switching logic is used in Continuation Power Flow computation for static voltage stability assessment.