Y-Matrix Modulation for SC-MMC Medium Voltage Grid-Tie Converter

This article illustrates the practical implementation of $Y$ -Matrix Modulation for a medium voltage grid-tie switched-capacitor modular multilevel converter (SC-MMC) with a middle submodule (SM). SC-MMC only contains switches and capacitors, and there is no physical arm inductor. Through $Y$ -Matrix Modulation, SC-MMC has the capability of self-voltages balancing. $Y$ -Matrix Modulation also eliminates the need for voltage sensors and complicated feedback controls. Moreover, $Y$ -Matrix Modulation can be used for both half-bridge and full-bridge structures for any $N$ -level modular multilevel converter (MMC). Therefore, this modulation is very effective owing to its simplicity, modularity, and sensorless features. Additionally, SC-MMC with a middle SM can generate the same voltage level with fewer cells. A modified $Y$ -Matrix Modulation is needed with the minimum number of sensors. This article provides experimental implementation of this modulation for a medium voltage grid-tie converter. $Y$ -Matrix generation is simplified using a less computationally demanding method. $Y$ -Matrix Modulation for four-SM SC-MMC with a middle SM is demonstrated in this article and compared with conventional modulations. A real-time computer hardware in the loop setup and small-scale experimental setup is used to verify the operation of the controller under steady-state and transient conditions.