Symmetrical Multi-pole MMC-HVDC with DC Fault Ride Through Capability Using HBSM

• Published in: Electric power components and systems 2023-06, Vol.51 (10), p.991-1008
• Main Authors: Yadav, Ankit, Singh, S. N., Das, S. P.
• Format: Article
• Language: English
• Subjects: Algorithms; Configuration management; Controllers; DC fault; Electric power supplies; fault ride through (FRT), DC transmission; HVDC; Impact analysis; modular multilevel converter (MMC); multi-pole; Power transfer; Reactive power; Real time; Shutdowns; sub-module (SM); Switches; Time measurement; Transmission lines; tri-pole
• ISSN: 1532-5008; 1532-5016
• DOI: 10.1080/15325008.2023.2188315

-The modular multilevel converter (MMC) has proven to be the most advanced voltage source converter (VSC). For long-distance power transfer, high-voltage DC (HVDC) is the best choice. Across the globe, electric power networks are witnessing rapid growth in MMC-HVDC installation to meet the ever-growing power demand. The existing AC transmission lines can be converted to DC lines by adding converters. The MMC-based multi-pole HVDC presents an adequate solution for upgradation. However, more study is required to make it a reality. The present paper attempts to bridge this gap. The proposed study can be divided into two parts. Initially, the concept of symmetrical multi-pole MMC-HVDC is proposed, and its mathematical relations have been derived. The multi-pole has been subdivided into an even and an odd configuration. The half-bridge submodule (HBSM)-based MMC lacks DC fault handling capability. The second part of the study includes controller and fault analysis of the HBSM-based tri-pole MMC HVDC. The study shows the severity of the pole-to-pole faults, leading to a complete shutdown of the transmission line. A controller and an algorithm for the DC fault-ride-through (FRT) have been proposed. The proposed controller has digital switches to temporarily bypass the real-time measurement values with measurements taken under healthy conditions. An impact analysis of the parameters of one MMC on the equilibrium of the entire multi-pole configuration is performed. The performance of the proposed controller has been carried out on a real-time digital simulator (RTDS). The proposed controller and FRT algorithm ensure that the tri-pole HVDC maintains the power supply during all DC faults. In the worst-case scenario, the shutdown is averted with a 50% reduction in power transfer capability. The transients in active and reactive power are minimized and eliminated within a cycle. Further, using the most economical and simplest submodule ensures the configuration without any additional cost.