Research on capacitor voltage ripple suppression method for power electronic transformer considering fluctuating power coupling

Cascaded power electronic transformer usually adopts large capacitance to suppress the capacitance voltage fluctuation of sub modules, which seriously limits the improvement of power density of power electronic transformer. To solve this problem, this paper firstly deduces the generation mechanism of double frequency fluctuating voltage and the coupling principle of fluctuating power. Secondly, this paper analyzes the reason why fluctuating power cannot flow naturally into the later stage from the perspective of input impedance, thereby, puts forward a capacitor voltage ripple suppression strategy by adjusting DAB input current in real time, which effectively reduces the fluctuation amplitude of capacitor voltage. Finally, the simulation model is built in PSCAD/ EMTDC, and compared with the traditional control strategy to verify the effectiveness of the proposed strategy.