Bidirectional Hybrid X Shape FCL in HVdc System With Multifunctional Feature

Bidirectional fault issue is common and serious in HVdc system and it cannot be handled by unidirectional fault current limiter (FCL). The novel contribution of this article is that it proposes a hybrid X shape FCL (HXFCL) with bidirectional fault limiting, fast breaking, and power flow adjusting capabilities. The HXFCL adopts the mutual inductance coupling effect of limiting magnetic modules and uses the full/semi control power electronic devices group. By working with the system fault protection signal and breaking part of the dc circuit breaker, the HXFCL can alter its device status and implement different functions with variable reactance. This article presents general topology of the HXFCL and gives analytical and optimization work of magnetic part. Meanwhile, electrical feature, control strategy, complete functions, and detailed performance comparison of the proposed HXFCL were performed. Simulations and experiments verify that the proposed HXFCL can work under multiple occasions. The fault limiting performance can be significantly improved, while the breaking requirements and reacting time can be significantly reduced.