SiC-based MMC for HVDC Applications: A Cost-Benefit Analysis

Abstract

This paper presents a comparative loss and cost analysis of Si and SiC-based modular multilevel converters (MMC). SiC devices have advantages like high critical breakdown strength, high-frequency operation, and lower switching losses. However, SiC devices are costlier than Si devices. The submodule in the designed (Si and SiC) MMC uses a half-bridge cell configuration, capacitor sorting algorithm was used to reduce the floating nature of voltage across capacitors in the submodules of MMC. Level shifted pulse width modulation technique has been implemented to provide switching to the MMC. For providing closed-loop control of grid-connected MMC, the output current control method was used. The average method of approach is followed to calculate the losses in the system. The MMC system design and analysis were done using MATLAB software. The loss analysis shows that the losses in SiC MOSFET MMC are about 22.8% lesser than in the Si-based MMC. However, the cost of SiC-based MMC is comparatively higher than Si-based MMC. But, the additional cost incurred in the SiC-based MMC can be recovered in 3.54 years.