Research on transient AC overvoltage suppression method of DC sending end based on novel fast-excitation MCR

• An improved winding connection mode as a fast excitation structure of MCR with its corresponding control logic is proposed, which can realize the rapid change of MCR output capacity by controlling the thyristors. The simulation and test verify that this fast excitation structure and control logic can reduce the dynamic response time of MCR from 400ms to 37ms. • A method for suppressing transient AC overvoltage of DC sending-end bus after commutation failure is proposed which is based on fast-excitation MCR. • It’s verified that the method proposed in this article can reduce the transient AC overvoltage of DC sending-end bus after commutation failure can be reduced from 1.352 p.u. to 1.298 p.u., and it is verified by parameter sensitivity analysis that within the range of U set from 1.0 p.u. to 1.16 p.u., changes in U set have a limited impact on the magnitude of the transient AC overvoltage, indicating that the proposed control strategy exhibits good robustness to variations in U set within a reasonable interval. • The voltage threshold triggering control strategy based on fast excitation MCR proposed in this article can ensure the suppression effect of transient AC overvoltage while avoiding deepening the degree of voltage drop in the early stage. The growing reliance on high-power high-voltage direct current (HVDC) transmission systems has intensified challenges associated with transient AC overvoltage induced by commutation failures resulting from converter operation characteristics. A widely adopted engineering solution involves deploying reactive power compensation devices to absorb excessive reactive power in converter stations post-commutation failure. Among these, the magnetically controlled reactor (MCR) demonstrates notable operational stability. However, conventional MCRs exhibit comparatively slower dynamic response times than alternative compensation devices, thereby constraining their effectiveness in transient overvoltage suppression. To address this limitation without introducing supplementary circuitry, this study presents a three-phase MCR optimization structure employing modified winding configurations and proposes its application for transient AC overvoltage mitigation in DC sending-end AC buses. A dynamic response simulation model of the fast-excitation MCR was developed using an electromagnetic transient simulation platform. Comparative analyses with conventional MCR systems revealed a 91 % reduction in dynamic response time, from 400 ms to 37 ms. Subsequent integration of the fast-excitation MCR into a HVDC system demonstrated its operational efficacy under commutation failure conditions. Implementation reduced transient AC overvoltage at the sending-end converter bus from 1.352 p.u. to 1.298 p.u., confirming the technical viability of the proposed fast-excitation MCR for overvoltage suppression in DC transmission infrastructure.