Modified Dual Active Bridge DC/DC Converter With Improved Efficiency and Interoperability in Hybrid LCC/VSC HVDC Transmission Grids

DC transmission grids are the promising electrical networks in the near future especially with the high penetration of large-scale renewables. This article proposes a modified version of the dual active bridge (DAB) dc/dc converter with ac link capacitors generating reactive power to compensate for nonactive power consumption, hence mitigating current stresses and losses to improve efficiency. The proposed topology also enables the connectivity of current source line-commutated HVDC and voltage source HVDC technologies particularly during power reversal; a feature which conventional DAB is incapable of doing. Analysis and detailed design of the proposed converter are addressed and a comparative performance analysis is carried out with conventional DAB. Converter principle of operation is explained and MATLAB/Simulink simulations are carried out to verify converter operation particularly under adverse conditions such as rated power reversal and dc fault conditions. A low-scale prototype substantiates the theoretical analysis and simulation results.