Transition Process and Influencing Factors of AC Transient Overvoltage Subject to HVDC Disturbances

Abstract

The AC overvoltage at the sending is an important factor to limit HVDC capacity. The previous research typically focuses on the static voltage characteristics, while this paper further studies the influence of the system-side dynamics on the AC transient overvoltage. Firstly, the voltage transition process subject a disturbance is analyzed to be divided into the electromagnetic transient process and electromechanical transient process. The transition on the equivalent impedance of the generators leads to a gradual increase of the overvoltage. The relationship between power angle and voltage is also deduced based on the Thevenin equivalent. Secondly, based on the electromagnetic transient transition process, the overvoltage mechanism is elaborated under the block, commutation failure, restarting, and short circuit faults. Meanwhile, different locations where DC is connected are considered to highlight the influence of the power distribution and inertia on the transient overvoltage. Finally, it is concluded that static voltage characteristics can give the initial value of the overvoltage, however, it cannot reflect the transition process of overvoltage. The time scale of the overvoltage involves the coupling of electromagnetic and electromechanical processes, and the influencing factors of overvoltage under different conditions should fully be considered.