Fault Current Limitation With Energy Recovery Based on Power Electronics in Hybrid AC–DC Active Distribution Networks

The active distribution networks have a tendency to develop toward hybrid ac–dc systems constructed by power electronics, the magnitude and direction of power may change randomly at any time, making the usual protection potentially insensitive, raising the negative impacts of single-phase ground (SPG) fault which accounts for the majority of all faults that occurred in medium-voltage (MV) distribution networks in the past. The zero-sequence current in the impedance induced between the lines and ground will pass through the SPG fault branch as fault current. This article transfers the flow path of the zero-sequence current from the SPG fault branch to the power electronic branch connected between the faulty phase and ground involved in the construction of hybrid ac–dc system, thereby limiting SPG fault branch current and reducing fault node potential. This helps to suppress fault arc and provides engineers with safe conditions to clear faulty elements from the SPG fault branch. The power electronic carries this zero-sequence current instead of SPG fault branch and therefore absorb energy from the distribution networks in the same way as SPG fault, but the energy is not lost but routed back to the hybrid ac–dc system for reuse. Simulations and experiments validate the proposal.