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This paper proposed a novel battery energy storage system based on modular multilevel converter (MMC), which has several merits compared with two-level and cascaded multilevel battery energy storage systems. The proposed system can manage the state-of-charges (SOCs) of all batteries to be equal to avoid the overcharge or over discharge of single battery stack as traditional. Besides, the inherent power exchange characteristics using circulating current could increase the control flexibility for SOC balancing, and improve output waveform quality, maximize storage capacity and reduce internal losses. The key issues regarding injected dc current control, SOC balancing control and circulating current control are discussed in this paper. Finally, the proposed system were verified through Matlab/Simulink simulation and a scaled down experiment prototype.

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Background and ObjectiveThe role of glucose transporters in cancers remains contradictory. We conducted a systematic review and meta-analysis to assess the association between overall survival and glucose transporter s (GLUTs) 1 and 3 to find an accurate prognostic biomarker.MethodsWe systematically searched the PubMed, EMbase and Medline databases for relevant published studies that were consistent with the eligible criteria up to January 2016, and calculated pooled estimated hazard ratios of GLUT-1 and -3′s expressions in different cancer types and ethnic populations. Random-effects models were used to assess estimates from studies with significant heterogeneities.ResultsOverall, 12 studies concerning GLUT 1 and 2 studies concerning GLUT 3, which involved 2008 participants when combined, were included in this analysis. We found that overexpression of GLUTs were significantly correlated to poorer survival rates (HR=1.63, 95%CI=1.09-2.44 and HR=1.89, 95%CI=1.28-2.81). In the subgroup analysis, the GLUT 1 up-regulation was correlated with negative overall survival in pancreatic cancer and gastric cancer and with better overall survival in colorectal cancer. In addition, overexpression of GLUT 1 was associated with a poorer prognosis in the Asian population, while no significance was found in the non-Asian subgroup. However, limitations do exist, which could be handled better.ConclusionsA combination of GLUTs 1 and 3 might help predict malignancy of cancers and direct effective cancer therapy.