Research on a novel DC/DC transformer and its control strategy for DC grid-connected renewable energy

Compared with conventional AC gird, the direct current (DC) grid is marked with flexible interconnection, variable control and economy benefits. With the development of DC grid, it is kept paying attention by both industry and academy while the corresponding DC grid technology has been extensively studied and researched. This paper discusses on the latest development of DC grid, summarizes suitable simulated models of DC grid´s facilities, and proposes a new DC/DC converter based on combining the single-phase modular multilevel converter (MMC) and H-bridge inverter, meanwhile, a novel control strategy in terms of carried phase shifted sinusoidal pulse width modulation (CPS-SPWM) is presented for the MMC control. By using simulation software, the DC/DC converter model is established and simulated in steady-state operation, load fluctuations and module failure scenarios respectively, the results show the demonstration on availability and reliability of this new DC/DC converter, and it becomes a stable technical scheme for the interconnection between renewable energy and DC gird.