Analysis of the transient voltage stability of AC/DC system based on numerical energy function method

Transient voltage stability problem has been a hot topic since power systems in many places suffer voltage collapse after large disturbance. In this paper, a numerical energy function, including detailed High Voltage Direct Current (HVDC) model, three-order generator model and one-order induction model, is proposed. Besides, a heuristic method is studied to identify the controlling unstable equilibrium point (CUEP) of the power system interconnected by HVDC. Combining the proposed energy function and the identified CUEP, the critical time for a power system to maintain transient voltage stability can be obtained. A three-machine nine-bus system interconnected with HVDC is used to demonstrate the effectiveness of the method.