Full-bridge modular multilevel converter (FB-MMC) with extended control range

This paper presents an attractive control scheme that decouples cell capacitor voltage regulation of the FB-MMC from the dc link voltage regulation. This is achieved by manipulating both ac and dc components of modulation functions. The dc component of modulation function is used to regulate the cell capacitor voltages independent of the dc link voltage, while the magnitude and phase of modulation function ac component are manipulated to control active and reactive powers FB-MMC exchanges with the ac grid. The significance of this control scheme is that it permits the FB-MMC to operate with variable dc link voltage, including negative dc link voltage and zero, while full control over the power FB-MMC exchanges with ac grid is retained. Additionally, this paper provides comprehensive discussion of MMC fundamental theory, including logical and mathematical derivations of the basic relationships that governed its operation and modulation. The validity of the presented control scheme is confirmed using simulations.