Design and Implementation of a Parallel-Connected Fault Current Attenuator for Power Distribution Systems

Parallel-connected fault current attenuator (PFCA) is a novel concept for active reduction of short-circuit currents (SCCs) through circuit breakers (CBs) in power distribution grids. The sustained increase in the SCCs could exceed the rating of the CBs, dangerously spreading the fault. Several series-connected schemes, such as fault current limiters and series reactors, have been proposed in recent decades to reduce these high currents. This article designs and experimentally verifies the feasibility of a parallel-connected power converter to reduce the SCCs, operating as a controlled current source by absorbing current from the fault point. This new configuration reduces the SCCs in all CBs of an electrical substation. The proposed PFCA is implemented using a single-phase neutral-point clamped (NPC) converter and tested using a predictive current control scheme for short-circuits in a scaled-down power system. The experimental results prove the effectiveness of the proposed scheme, reducing significantly the first SCC peak, even when the ac bus voltage is close to zero.