PROJECT TITLE :

Soft-Switching Operation of Isolated Modular DC/DC Converters for Application in HVDC Grids

ABSTRACT:

High-voltage dc/dc converters play an necessary role in HVDC grids. Isolated modular dc/dc converters (IMDCCs) based mostly on modular multilevel converter technology give a sensible resolution to high-voltage applications. In order to cut back the dimensions of the system, the IMDCC is needed to be operated with a high ac-link frequency, however this will result in increased switching loss and so degraded efficiency. This paper proposes a soft-switching operation scheme for such an IMDCC. In this scheme, a quasi-square-wave (QSW) modulation methodology is used, where the chain-links generate quasi-sq. terminal voltages with reduced dv/dt. With such chain-link terminal voltages, the arm currents which provide sensible condition for the soft-switching operation of the QSW-IMDCC can be obtained. Since soft switching will be achieved for the power switches, the proposed theme will suffer less switching loss, so improving the efficiency of the converter. Moreover, a capacitor voltage-balancing control strategy is proposed. This strategy does not would like any arm current sensors, thus reducing the value. The proposed soft-switching operation scheme and capacitor voltage-balancing management strategy are verified by the simulation results.