A novel voltage source converter for low voltage DC system based on high input AC voltage applications

The main structure of the proposed voltage source converter (VSC) for low voltage DC (LVDC) system is composed of three cascaded PWM rectifiers (CPRs) and a parallel DC-DC converter (PDC). High voltage AC grid is the input of the VSC. In order to ensure proper operation of the VSC, the control method should achieve output voltage sharing (OVS) among rectifiers in CPR, output current sharing (OCS) among DC-DC converters in PDC and low total harmonic distortion (THD) in VSC input currents. Master-slave direct current control (MDCC) is used to control CPR. The anti-interference ability of control system is robust by using MDCC without circuit parameters. PDC is controlled by three-loop control which is composed of outer common output voltage loop, inner current loops and current sharing loops. Simulation results show low THD in VCS input currents, good OVS in CPR and good OCS in PDC.