A systematic review of fault characteristics and protection schemes in hybrid AC/DC networks: Challenges and future directions

Incorporating DC into existing AC networks to meet rising energy demands and lessen carbon emissions has changed the paradigm of power systems. Hybrid AC/DC networks integrate renewable energy sources (RESs) to increase capacity and reduce losses in transmission/distribution networks. However, the existing AC and DC protection schemes are being challenged in hybrid networks due to the different characteristics of AC, DC faults, and bidirectional power flows from RESs. These schemes require multiple modifications before their application to the fault protection of a hybrid network. Therefore, the current study reviewed the existing protection schemes with an in-depth analysis of hybrid network architectures, AC/DC fault characteristics, and grounding techniques concerning the protection challenges of hybrid AC/DC networks. This study emphasizes the recent developments of intelligent techniques and their applicability to hybrid network protection to avoid faults and blackouts. This research is based on a systematic and thorough investigation of fault-protection schemes with proper classification based on the hybrid AC/DC protection criteria with simulated results. Subsequently, a critical analysis of the merits and demerits of existing protection schemes is performed. Furthermore, the findings and recommendations are presented as a contribution to the protection of hybrid networks based on the detailed overview and simulated analysis to make hybrid networks more robust and reliable.