Comparison of Modular Multilevel Converter Based Solid State Transformer for AC/DC Application
Zhengzhao Li (TU Delft - DC systems, Energy conversion & Storage)
Zian Qin (TU Delft - DC systems, Energy conversion & Storage)
Reza Mirzadarani (TU Delft - High Voltage Technology Group)
Mohamad Ghaffarian Niasar (TU Delft - High Voltage Technology Group)
Mahesh Itraj (Vonk)
Lou Van Lieshout (Vonk)
Pavol Bauer (TU Delft - DC systems, Energy conversion & Storage)
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Abstract
For electrolyzer applications, traditional solutions using line frequency transformers plus rectifiers are bulky, heavy and have low controllability. The Solid State Transformer (SST) could be a promising solution to solve the mentioned issues. This paper compares the semiconductor ratings and capacitance of five different Modular Multilevel Converter (MMC) based Solid State Transformer (SST) topologies. The results show that the DRU (Diode Rectifier Unit)-MMC based topologies have the lowest semiconductor ratings and capacitance. Because of the unidirectional power flow requirement, the source side MMC of Back-to-Back (BtB) MMC based SST could be replaced by DRU, thus the cost is drastically saved. Another interesting finding is that the DRU-MMC energy ripple is much lower than half of the energy ripple in BtB MMC, which is different from HVDC MMC.