Boost inverter-based HVDC transmission system with inherent blocking capability of AC side contribution during DC side faults

Abstract

Semiconductor advancements in the past three decades have positioned the voltage source converter-based HVDC (VSC-HVDC) solution as a practical and popular alternative to its line-commutated converter high voltage DC (LCC-HVDC) counterpart. The VSC-HVDC systems offer higher flexibility and system controllability features. One of the important challenges requiring careful investigation in such systems is the protection against DC side faults. Unfortunately, the VSC is inherently defenseless against such faults (DC link short circuit or DC cable short circuit). This paper proposes an HVDC system topology, namely, the boost inverter-based HVDC system (BI-HVDC), which provides complete blocking capability between the AC grid and the DC side fault. This blocking capability limits the DC fault current level to the DC capacitor discharge current. Ratings and characteristics of the proposed system compared to other existing topologies are highlighted in this work. A simulation study is conducted to check the performance of the proposed system during normal as well as abnormal operating conditions. A comparison between the performance of the conventional 2-level VSC-HVDC and the proposed system during DC side faults is also presented. The simulation results elucidate a significant decrease in the DC fault current due to the blocking capability of the BI-HVDC system during DC side faults.