Minimum DC Link Capacitance for a Family of Three-Phase Three-Level Grid-Connected Converters Operating with Arbitrary Power Factor

This paper introduces an approach to calculating the minimum value of split DC link capacitance in three-phase three-level grid-connected DC-AC converters operating with arbitrary power factor without either active balancing circuits or AC zero sequence injection. Due to the fact that partial DC link voltages and rectified mains phase voltages reach their maximum and minimum values, respectively, at different time instants, it is feasible to decrease the minimum value of the former below the maximum value of the latter while still maintaining proper functionality of the power stage. The minimum possible split DC link capacitance values are hence derived from the boundary condition where the above-mentioned voltages are tangent to each other. The accuracy of the analytical derivations is confirmed by simulations using PSIM software, which show a high degree of agreement.