Research on voltage and switching balance control for cascaded power electronic transformer under hybrid PWM modulation

A voltage and switching balance control method for cascaded power electronic transformer under hybrid PWM modulation is investigated in this paper. By using switch function rotation strategy among sub-modules as well as a switching allocation scheme between bridge arms to equalize the power and switching distribution, the method is developed. In addition, a voltage feedback-feedforward-based controller for IBDC converters is utilized to further ensure the dc-link voltages are balanced, in case of slight difference of series modules. By utilizing the proposed control method, the properties of the subject investigated including voltage and switching balance, low THD, unity power factor, and reduced switch frequency, are satisfactory. And the validity of the design is verified by the simulation and experimental results.