Arm reactors

as critical components in modular multilevel converter(MMC)

are predominantly implemented as air core reactors. Their fixed inductance values make it difficult to optimize and balance the current suppression performance and system dynamic response. To overcome this

this paper proposes a novel magnetic saturation bridge arm coupled reactor (MACR) with adaptively variable inductance. The MACR utilizes the nonlinear magnetization characteristics of soft magnetic materials and mutual coupling between windings to achieve adaptive inductance modulation under three operating conditions

namely

steady state

circulating current

and fault current

thereby effectively suppressing both circulating and fault currents. Firstly

for the magnetic saturation core structure and four winding coupling design of the MACR

the three different operating modes were analyzed from the perspective of magnetic circuit and electrical circuit equivalent models

and the analytical expressions of the equivalent inductance under corresponding operating conditions were derived. Secondly

device finite element simulation and system level co-simulation for the ±800 kV voltage class were conducted. The results prove that the inductance value of the MACR remains stable during steady state operation

increases under circulating current conditions

and increases further during faults. This effectively enhances the system’s ability to suppress circulating currents and limit fault currents. Finally

a small capacity MACR prototype was developed

and prototype experiments were carried out. The experimental results are consistent with the theoretical analysis

verifying the feasibility of the proposed topology.