A Partial Power Processing Structure Embedding Renewable Energy Source and Energy Storage Element for Islanded DC Microgrid

Abstract

In the past ten years, because of less power transferred loss, the partial power processing (PPP) converter systems are extensively studied for embedding the renewable energy source (RES) into the strong grid system. Moreover, by combining the energy storage system (ESS), the RES can provide the required power for the consumer stably, but the RES is usually connected to the dc bus through dc–dc converter system without PPP characteristic. Therefore, in this article, a novel PPP structure, which can embed the RES and the ESS, is proposed for the islanded dc microgrid with robust dc-link voltage. Notably, this structure can deal with the small difference among different RES units as well as the difference between the total output power of RESs and the required power of consumer. Besides, in the proposed PPP structure, the RES should feature the limited range of voltage regulation such as photovoltaic (PV) and fuel cell. Then, the control requirement of the RES and the robust dc-link voltage can both be achieved. In addition, based on the dual-active-bridge (DAB) dc–dc converter, a DAB-based PPP converter system is proposed for verifying the effectiveness of the proposed PPP structure. Then, a high-robustness control scheme is proposed for maintaining the total dc-link voltage when the working condition of the RES, the output voltage of the ESS, and the power requirement of the consumer are changed. Furthermore, when output power of one RES unit is limited, the corresponding operation is also proposed. Finally, by using PV panel as an example, simulation results and experiment results are provided to verify the effectiveness of the proposed PPP structure and the proposed methods.