Investigation of Liquid Metal Current Limiter for MVDC Power System

Liquid metal current limiter (LMCL) based on forced current commutation is potential to be used in MVDC power system. This LMCL utilizes fast switch (FS) and a parallel connecting path consists of several current limiting elements (CLEs) and an auxiliary magnetic induction module (MIM) in serial. The MIM consists of a pre-charged capacitor C, a thyristor T and a set of magnetic coupling coils (MCC). In this paper, a simulation model of this LMCL is built to investigate the current limiting process. And it is experimentally verified according to current commutation and limitation characteristics. Furthermore, based on this model, the current commutation characteristics are analyzed allowing for different influencing factors including the stray inductance of CLEs path and the parameters of MIM. It can be concluded that the effect of CLEs path stray inductance plays a vital role to current commutation process. Finally, the pre-arcing characteristics of CLE during current commutation process are experimental revealed. The pre-arcing duration tends to decrease with the first 100μs current rising rate (di/dt) increasing. And the arc will not ignite during current commutation when the first 100μs di/dt is 200A/μs at specific conditions.