Topology Improvement of the Current Source Modular Multilevel Converter: Steady-State Analysis

A steady-state analysis of the Current Source Modular Multilevel Converter (CSMMC) is carried out in this paper. Time-domain expressions of the inductors current, upper and lower currents, and the so-called circulating currents are derived. The underlying reason behind the existence of a fundamental-frequency component in the inductors currents is explained. A modified CSMMC that eliminates that component is proposed. The modified CSMMC uses the same number of switches, with the same voltage ratings, and half the number of inductors. Moreover, the inductors sizes are reduced. Steady-state analysis of the modified CSMMC is also included.