Resonant Modular Multilevel DC Transformer Based on Quasi-square-wave Modulation Strategy
DC grid is an essential solution to achieving efficient integration of renewable energy and flexible access of DC loads,and the DC transformer is a piece of key equipment that can interconnect DC systems with different voltage levels.In this paper,a resonant modular multilevel DC transformer is proposed,in which half-bridge submodule strings are series connected on the medium-voltage side and full-bridges are parallel connected on the low-voltage side.As a re-sult,the voltage and current stress are significantly reduced,and the number of power devices and transformers also de-ceases.Quasi-square-wave modulation and phase-shifted control are employed to increase the AC link frequency and achieve the fixed frequency output voltage control.Based on the fundamental harmonic approximation method,the transmission power characteristics are analyzed,and the key parameter design procedure and output voltage control strategy are formulated accordingly.Finally,the feasibility of the proposed topology and control method was validated by a 4 kW/600 V/100 V prototype.
DC gridDC transformer(DCT)modular multilevel converter(MMC)resonant converterquasi-square-wave(QSW)modulation
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维普
