Search

The energy crisis has swept the whole earth in the 21st century, and all kinds of traditional fuels have been used out, and the serious pollution of environment has restricted the further development of the world. In this way, the clean and no-pollution renewable energy is very precious. And the solar technology shows great potential in many kinds of renewable energies. So if we want to have a widespread application of solar energy and connect to the grid, the grid-connected technology must be safe and reliable. And the DC power produced by photovoltaic power generation should use the inventers when it connects to the grid. We know that the topology structures of active filter and inverter are very similar. Therefore, using the similarities of them to study the unified control of photovoltaic grid system and harmonic compensation of APF can make it have two functions. This paper puts forward a design method of LCL filter circuit which can be used on both photovoltaic and APF based on summarizing the application under each situation. This paper talks the advantage of LCL circuit compared with other filtering ways, and puts forward the design principle, the choice of parameters and the simulation experiments to get a proper grid-connected photovoltaic system inverter. [ABSTRACT FROM AUTHOR]

Objective To summarize the characteristics of PPP disease complex with placenta implication and explore the value of prenatal ultrasonographic scoring system in placenta prevlia complicate with placenta accrete. Methods An retrospective analysis was conducted among 179 case of ultrasound images of pernicious placenta previa complicate with placenta accrete, and the results of postpartum were compared. Based on clinical surgery and/or pathological results as the gold standard， all cases were divided into adhesive placenta accreta group and non-adhesive placenta accreta group. Results Logistic regression identified six sonographic parameters，including placenta thickness， obliteration of retroplacental hypoechoic space， smallest sagittal myometrial thickness， presence of abnormal vessels linking the placenta to the bladder， lacunar flow distributed within intraparenchymal placenta area and the cervical form. Different scores were assigned according to the odds ratio of these parameters. The critical score of the ultrasound score of adhesive placenta accreta and non-adhesive placenta was 6 points. Conclusions Prenatal ultrasonographic scoring system is a reliable method to diagnose the degree of the accretion in pernicious placenta previa complicate with placenta accrete. [ABSTRACT FROM AUTHOR]