Three-Phase Four-Wire Inverter Topology with Neutral Point Voltage Stable Module for Unbalanced Load Inhibition

Cai, Chunwei,An, Pufeng,Guo, Yuxing,Meng, Fangang The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

A novel three-phase four-wire inverter topology is presented in this paper. This topology is equipped with a special capacitor balance grid without magnetic saturation. In response to unbalanced load and unequal split DC-link capacitors problems, a qusi-full-bridge DC/DC topology is applied in the balance grid. By using a high-frequency transformer, the energy transfer within the two split dc-link capacitors is realized. The novel topology makes the voltage across two split dc-link capacitors balanced so that the neutral point voltage ripple is inhibited. Under the condition of a stable neutral point voltage, the three-phase four-wire inverter can be equivalent to three independent single phase inverters. As a result, the three-phase inverter can produce symmetrical voltage waves with an unbalanced load. To avoid forward transformer magnetic saturation, the voltages of the primary and secondary windings are controlled to reverse once during each switching period. Furthermore, an improved mode chosen operating principle for this novel topology is designed and analyzed in detail. The simulated results verified the feasibility of this topology and an experimental inverter has been built to test the power quality produced by this topology. Finally, simulation results verify that the novel topology can effectively improve the inhibition of an inverter with a three-phase unbalanced load while decreasing the value of the split capacitor.

A Novel Zero-Voltage-Switching Push-Pull Forward Converter with a Parallel Resonant Network

Cai, Chunwei,Shi, Chunyu,Guo, Yuxing,Yang, Zi,Meng, Fangang The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

A novel zero-voltage-switching (ZVS) push-pull forward converter with a parallel resonant network is presented in this paper. The novel topology can provide a releasing loop for the energy storage in a leakage inductor for the duration of the power switching by the resonant capacitors paralleled with the primary windings of the transformer. Then the transformer leakage inductor is utilized to be resonant with the parallel capacitor, and the ZVS operation is achieved. This converter exhibits many advantages such as lower duty-cycle losses, limited peak voltage across the rectifier diodes and a higher efficiency. Furthermore, the operating principles and key problems of the converter design are analyzed in detail, and the ZVS conditions are derived. A 500W experimental converter prototype has been built to verify the effectiveness of the proposed converter, and its maximum efficiency reaches 94.8%.

A Novel Zero-Voltage-Switching Push-Pull Forward Converter with a Parallel Resonant Network

Chunwei Cai,Chunyu Shi,Yuxing Guo,Zi Yang,Fangang Meng 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

A novel zero-voltage-switching (ZVS) push-pull forward converter with a parallel resonant network is presented in this paper. The novel topology can provide a releasing loop for the energy storage in a leakage inductor for the duration of the power switching by the resonant capacitors paralleled with the primary windings of the transformer. Then the transformer leakage inductor is utilized to be resonant with the parallel capacitor, and the ZVS operation is achieved. This converter exhibits many advantages such as lower duty-cycle losses, limited peak voltage across the rectifier diodes and a higher efficiency. Furthermore, the operating principles and key problems of the converter design are analyzed in detail, and the ZVS conditions are derived. A 500W experimental converter prototype has been built to verify the effectiveness of the proposed converter, and its maximum efficiency reaches 94.8%.

Three-Phase Four-Wire Inverter Topology with Neutral Point Voltage Stable Module for Unbalanced Load Inhibition

Chunwei Cai,Pufeng An,Yuxing Guo,Fangang Meng 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

A novel three-phase four-wire inverter topology is presented in this paper. This topology is equipped with a special capacitor balance grid without magnetic saturation. In response to unbalanced load and unequal split DC-link capacitors problems, a qusi-full-bridge DC/DC topology is applied in the balance grid. By using a high-frequency transformer, the energy transfer within the two split dc-link capacitors is realized. The novel topology makes the voltage across two split dc-link capacitors balanced so that the neutral point voltage ripple is inhibited. Under the condition of a stable neutral point voltage, the three-phase four-wire inverter can be equivalent to three independent single phase inverters. As a result, the three-phase inverter can produce symmetrical voltage waves with an unbalanced load. To avoid forward transformer magnetic saturation, the voltages of the primary and secondary windings are controlled to reverse once during each switching period. Furthermore, an improved mode chosen operating principle for this novel topology is designed and analyzed in detail. The simulated results verified the feasibility of this topology and an experimental inverter has been built to test the power quality produced by this topology. Finally, simulation results verify that the novel topology can effectively improve the inhibition of an inverter with a three-phase unbalanced load while decreasing the value of the split capacitor.

Insoluble Dietary Fiber from Pear Pomace Can Prevent High-Fat Diet-Induced Obesity in Rats Mainly by Improving the Structure of the Gut Microbiota

( Shimin Chang ),( Xingtian Cui ),( Mingzhang Guo ),( Yiling Tian ),( Wentao Xu ),( Kunlun Huang ),( Yuxing Zhang ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.4

Supplement of dietary fibers (DF) is regarded as one of the most effective way to prevent and relieve chronic diseases caused by long-term intake of a high-fat diet in the current society. The health benefits of soluble dietary fibers (SDF) have been widely researched and applied, whereas the insoluble dietary fibers (IDF), which represent a higher proportion in plant food, were mistakenly thought to have effects only in fecal bulking. In this article, we proved the anti-obesity and glucose homeostasis improvement effects of IDF from pear pomace at first, and then the mechanisms responsible for these effects were analyzed. The preliminary study by real-time PCR and ELISA showed that this kind of IDF caused more changes in the gut microbiota compared with in satiety hormone or in hepatic metabolism. Further analysis of the gut microbiota by high-throughput amplicon sequencing showed IDF from pear pomace obviously improved the structure of the gut microbiota. Specifically, it promoted the growth of Bacteroidetes and inhibited the growth of Firmicutes. These results are coincident with previous hypothesis that the ratio of Bacteroidetes/Firmicutes is negatively related with obesity. In conclusion, our results demonstrated IDF from pear pomace could prevent high-fat diet-induced obesity in rats mainly by improving the structure of the gut microbiota.

1-methylcyclopropene treatment improves postharvest quality and antioxidant activity of Prunus domestica L. cv. Ximei fruit

Ma Yanyan,Zhang Weida,CHENGSHAOBO,Yang Wanting,Liu Yuxing,Yang Shengyu,Zhang Xinling,Guo Minrui,Chen Guogang 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.6

Prunus domestica L. cv. Ximei fruit perishes quickly due to intense metabolic activity after being harvested. To prolong shelf life and maintain fruit quality, the eff ects of 1-methylcyclopropene (1-MCP) treatment on P. domestica fruit during storage at 4 ± 1 °C were investigated. The results showed that the soluble solid content (SSC), respiratory rate (29.8%), ethylene production (27.2%), anthocyanin content, malonaldehyde content (MDA), hydrogen peroxide content (H 2O2), and superoxide anion activity (O 2·−) of P. domestica fruit were all signifi cantly reduced by 1-MCP treatment (1.0 μL L −1), while the content of ascorbic acid and total phenol, and the activity of SUPEROXIDE DISMUTASE (SOD, 61.3%), CATALASE (CAT, 39.0%), ASCORBATE PEROXIDASE (APX, 23.7%), and PEROXIDASE (POD, 38.0%) increased compared to untreated fruit after 35 days of cold storage. Overall, 1-MCP treatment could maintain high postharvest quality and anti- oxidant activity in P. domestica fruit