Interaction of torsional dynamics and loads

The linearization equations of load models including fifth-order motor, constant impedance (Z), constant current (I) and constant power (P) are derived, which can interface with the network equations for the analysis of subsynchronous resonance (SSR). The IEEE First Benchmark Model is adopted to analyze the effect of the above load models on the damping characteristics of torsional modes. It is observed that the analysis result can be optimistic without inclusion of load models and there is no any load model which ensures that the results are always conservative.