Study of influence on AC line active power by DC system quitting operation

If DC system quits operation due to commutation failure in AC-DC hybrid transmission system, the power flow will largely transfer to AC lines, which may cause AC lines overload. Thus, it's essential to analyze the power transferring after DC system quits operation. And the results will provide the basis for the following emergency control measures to ensure system security. This paper studies the change of AC line active power caused by the quitting of DC line under steady-state operation conditions, and sensitivity analysis of AC system is extended to AC-DC system. Fast adjustable performance of DC system and the impact on AC system is equivalent to load or power source with fast dynamical performance. DC line active power transferring sensitivity is introduced to describe the impact of DC quitting operation on AC line active power. Besides, complicated power calculation is avoided by applying the sensitivity of node power injection to line active power. Then the change of AC line active power can be quickly calculated to predict whether there is an overload. The rapidity and validity of the proposed algorithm is verified by the calculation results of improved CEPRI 36 bus test system.