Abstract The operation mode of the capacitor-filtered three-phase uncontrolled rectifier can be divided into continuous current mode and discontinuous current mode. In accordance with the number of conducted power devices in the operation, there are two discontinuous current modes, i.e. ‘2/0’ mode and ‘2/3/2/0’ modes. Because the switching process of 2/3/2/0 mode is complex, and the corresponding load range is specific, the research before mostly concentrated in 2/0 mode. Numerical analysis is applied in this paper to study the 2/3/2/0 mode. According to the equivalent circuit and boundary conditions in different stages,by taking advantage of the symmetry of the voltage and current,parsing expressions are listed. Mathematical derivation is made to describe the circuit states switches during 1/6 of a period by a five-element differential equations system and to solve the system in a numerical way. Following the above steps, the harmonic content of voltage and current is analyzed. Compared with the simulation results, the correctness of the proposed method is verified.
2018, Vol. 19 
