多时间尺度电力系统的模型降阶及稳定性分析:(二)电力系统的降阶与中长期失稳

从元件的基本方程出发 ,导出了电力系统的三时间尺度模型。利用慢流形和快流形的概念 ,研究了电力系统三时间尺度动态模型降阶的条件。在感应电动机并联线性阻抗的负荷模型下 ,证明了在静态稳定和暂态稳定分析中略去发电机定子绕组阻尼磁链和负荷感应电动机转子绕组磁链动态的合理性 ;证明了在静态稳定分析中固定发电机组原动机力矩的合理性 ;通过一个利用固定负荷慢动态的降阶模型判断暂态稳定性导致误判的实例 ,说明了在暂态稳定分析中随意地固定负荷慢动态是不可取的 ,并指出未建模负荷慢动态是造成电力系统发生中长期失稳的原因

ORDER REDUCTION AND STABILITY ANALYSIS FOR MULTI-TIME SCALE POWER SYSTEMS Part Two Order Reduction and Loss of Mid-term and Long-term Stability

In this paper, a three time scale power system model is derived based on basic equations of power system elements. The condition for the reduction of a three time scale power system model is studied by using the concepts of fast and slow manifolds. In this study all the system loads are modeled as induction motors in parallel with linear impedance. It is proved that the dynamics of the flux linkages of generator damp windings and induction motor rotor windings can be neglected reasonably in conducting dynamic and transient stability analysis, and that it is reasonable to fix the generator mechanical torques in performing dynamic stability analysis. Through studies on a simplified power system, it is shown that fixing the slow dynamics of loads may result in errors in stability assessment, and it is explained that the existence of slow load dynamics is the reason for leading to loss of mid term and long term stability of power systems.