Stability Analysis for HVDC/AC Power Systems Based on a Modal Series Method

Modal series methods can be used to represent the dynamic characteristics of a nonlinear system. In this paper the modal series method is applied to investigate the stability and the nonlinear modal interaction in HVDC/AC power systems. A comprehensive analytical technique based on the modal series method and symbolic computer algebra is proposed for the analysis of power systems that include HVDCs. Using this method, we can study the oscillation modes and non-linear dynamic behavior of power systems subjected to large disturbances. The results are suitable for complex power system stability analysis and control system design. The proposed method is general and may be extended to include other FACTS devices. A test system is used to illustrate the proposed methodology. The analytical results are compared with detailed non-linear time-domain simulations to check the validity of the analysis. 1