Fault current limiter and control strategy based on hybrid distribution transformer in DC microgrid

After a short-circuit fault on the DC bus of a Hybrid Distribution Transformer (HDT), the existing passive protective measures are difficult to effectively protect power electronic devices. Furthermore, when considering the inductance of the DC line and the capacitance on the DC bus side of the converter, conventional active current limiters exhibit the characteristic of current oscillation in the limiting inductance. This paper provides a detailed analysis of the mechanism behind this current oscillation characteristic and explores the impact of changes in system parameters on the oscillation peak of the limiting inductance current. Additionally, a novel topology and control strategy for an active current limiter are proposed. This topology dissipates energy by adding an energy dissipation branch that conducts when the DC bus voltage of the limiter becomes negative, thereby resolving the issue of inductance current oscillation. Simulations have verified the effectiveness of the proposed novel active current limiter in suppressing inductance current oscillation characteristics and demonstrated its robustness under different operating conditions.