Disturbance Rejection and Control Design of MVDC Converter with Evaluation of Power Loss and Efficiency Comparison of SiC and Si Based Power Devices

Abstract

With direct current (DC) power generation from renewable sources, as well as the current relocation of loads from alternating current (AC) to DC, medium-voltage DC (MVDC) should fill gaps in the areas of distribution and transmission, thereby improving energy efficiency. The MVDC system is a platform that interconnects electric power generation renewables (solar, wind) with loads such as data centers, industrial facilities and electric vehicle (EV) charging stations (also using MVDC technology). DC–DC power converters are part of the rising technology for interconnecting future DC grids, providing good controllability, reliability and bi-directional power flow. The contribution of this work is a novel and efficient multi-port DC–DC converter topology having interconnections between two converters, three-level neutral point clamping (NPC) on the high-voltage (HV) side and two converters on the low-voltage (LV) side, providing two nominal low voltages of 400 V (constant) and 500 V (variable), respectively. The design of this new and effective control strategy on the LV side has taken into condition load disturbances, fluctuations and voltage dips. A double-closed-loop control topology is suggested, where an outside voltage control loop (in which the capacitance energies are analyzed as variable, and the inside current loop is decoupled without the precise value of boost inductance) is used. The simulation results show the effectiveness of the proposed control system. In the second part of this study, wide-bandgap SiC and Si devices are compared by using comprehensive mathematical modeling and LT-spice software. Improving power loss efficiency and overall cost comparisons are also discussed.