Reliability and Cost Modeling of a Modular Multilevel Converter

This paper presents an analytical expression to calculate the reliability, cost and loss for Modular Multilevel Converter (MMC) based high voltage applications. A three-terminal DC system is chosen as a case study with different terminal modeling. Terminal 1 is modeled with conventional vector current control and circulating current control. Terminal 2 is modeled with a Fault-Tolerant Controller and dq based circulating current control, and terminal 3 is modeled with a conventional vector current control with no circulating current control. In addition to the control structure, Nearest Level Modulation (NLM) is adopted for each terminal. The MTDC system is investigated based on the total reliability and availability of the terminals. Besides, analytical loss and cost calculations are performed for the three-terminal DC system. Different redundancy techniques for MMC arms are presented, but a 10% active redundancy scheme is adopted in the three-terminal DC system.