Multimode Operation Mechanism Analysis and Power Flow Flexible Control of a New Type of Electric Energy Router for Low-Voltage Distribution Network

Due to limitations of topology, the series architecture electric energy router (SA-EER) for low-voltage distribution network (LVDN) has the disadvantages that the energy transmission range is limited to 100% and reactive powers are unable to operate flexibly. For this reason, a new type of EER with series-parallel architecture (SPA-EER) is constructed in this paper, and it can break through the above disadvantages in SA-EER. In addition to series-parallel architecture, a two-degree-of-freedom power flow flexible control strategy (TDF-PFFCS) is proposed to further support the realization of these two breakthroughs. According to TDF, the operation states of SPA-EER can be discriminated into 6 modes, and then their operation mechanisms are analyzed. Considering the rated capacity limitations of LVDN ports and power electronic converters in SPA-EER, the operation ranges of TDF are discussed, and constraint relationships between TDF and these rated capacities are further established, so as to avoid the issue of over-limit rated capacities. Finally, the simulation results prove that the constructed SPA-EER and proposed TDF-PFFCS can achieve the transmission targets that the maximum allowable amounts of active and reactive powers are 200% and 120% respectively, which provides new design ideas and solutions for EERs to realize the high-power energy flexible transmission.