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With the development of renewable energy, DC distribution power system (DPS) becomes more and more attractive. The stability of whole system is still a big concern though every single converter is well-designed based on the stand alone operation with sufficient stability. Since the cascaded connection of power converters is one of the most dominant connection forms in the DC DPS, the stability analysis of the cascaded system is very important to ensure stability of the whole system. Based on Lyapunov linearization method and Brayton-Moser's mixed potential theory, stability of equilibrium point and an estimation of the region of attraction are investigated for cascaded system in the DC DPS. Based on the analysis, stability prediction criteria for cascaded system under small-signal and large-signal disturbance are obtained. The two criteria is simple and straightforward, which can be unified to get a general stability criterion to predict system's stability under both small-signal and large-signal transient disturbance. The relationship between system parameters and the stability is presented and discussed in the paper. Therefore, instead of trial and error, the proposed criterion can predict and guarantee the stability operation of cascaded system during the design process, and it is also helpful to select matched power converters in system level design. The simulation and experimental results verify the effectiveness of the proposed criterion.

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Activated epidermal growth factor receptor (EGFR) has emerged as an important therapeutic target for a variety of solid tumors, particularly malignant gliomas. A recently discovered transmembrane glycoprotein, LRIG1, antagonizes the activity of epidermal growth factor receptor family receptor tyrosine kinases and acts as a negative feedback loop of EGFR and proposed tumor suppressors. The aim of this study was to investigate the impact of LRIG1 on the biological features of glioma cells and the possible mechanisms of enhanced apoptosis induced by upregulation of LRIG1. We observed that the expression of LRIG1 was decreased, while the expression of EGFR was increased in the majority of astrocytomas, and the ratio of EGFR/LRIG1 was increased by sixfold in tumors versus corresponding non-neoplastic tissue. Upregulation of LRIG1, followed by a decrease of EGFR on the cytomembrane of the cells, induced cell apoptosis and cell growth inhibition, and further reversed invasion in glioma cell lines and primary glioma cells. Our study now clearly indicates that LRIG1 indeed affects cell fate and biology behaviors of the cells in vitro by inhibiting phosphorylation of downstream MAPK and AKT signaling pathway, and the elevated release level of caspase-8 might contribute to the enhanced apoptosis in LRIG1 transfected glioma cells. Taken together, these findings provide us with an insight into LRIG1 function, and we conclude that LRIG1 evolved in gliomas as a rare feedback negative attenuator of EGFR and could offer a novel therapeutic target to treat patients with malignant gliomas.