China's moon rover separates from moon lander

CHINA ATERIZOU COM SUCESSO SUA PRIMEIRA SONDA ESPACIAL NÃO TRIPULADA NA LUA,CHINA E APENAS O TERCEIRO PAIS A POUSAR NA LUA,SEGUINDO OS EUA E A ANTIGA UNIÃO SOVIETICA,QUE TANTO REALIZOU AS TAREFAS DECADAS ATRAS. "E UMA CONQUISTA DIGNA DE RESPEITO",DISSE JOHN LOGSDON,PROFESSOR EMERITO DA UNIVERSIDADE DE GEORGE WASHINGTON,QUE HA MUITO TEM MONITORADO POLITICA ESPACIAL.
'CHANG-3 E IMPRESSIONANTE COMO O PRIMEIRO POSSO NA LUA EM QUASE QUATRO DECADAS,CAINDO EM UM LUGAR QUE NÃO FOI EXPLORADO E USANDO INSTRUMENTAÇÃO CIENTIFICA RELATIVAMENTE AVANÇADA.

Analysis of the Internal Electrical Characteristics of Electronic Power Transformers Yang Yi*, Cheng-Xiong Mao*, Dan Wang†, and Ji-Ming Lu**

Analysis of the Internal Electrical Characteristics of Electronic Power Transformers Yang Yi*, Cheng-Xiong Mao*, Dan Wang†, and Ji-Ming Lu** *State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, China †**College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, China.
Abstract The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC–DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC–DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations,and experiments confirm the theoretical analysis of the subunit of EPT.
LINK
 http://jpe.or.kr/archives/view_articles.asp?seq=776

New Isolated Single-Phase AC-DC Converter for Universal Input Voltage Ming-Rong Lee*, Lung-Sheng Yang†, and Chia-Ching Lin*

New Isolated Single-Phase AC-DC Converter for Universal Input Voltage Ming-Rong Lee*, Lung-Sheng Yang†, and Chia-Ching Lin* *†Dept. of Electrical Engineering, Far East University, Tainan City, Taiwan Abstract This paper investigates a new isolated single-phase AC-DC converter, which integrates a modified AC-DC buck-boost converter with a DC-DC forward converter. The front semi-stage is operated in discontinuous conduction mode (DCM) to achieve an almost unity power factor and a low total harmonic distortion of the input current. The rear semi-stage is used for step-down voltage conversion and electrical isolation. The front semi-stage uses a coupled inductor with the same winding-turn in the primary and secondary sides, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. The discharging time can be shortened. In other words, the duty ratio can be extended. This semi-stage can be operated in a larger duty-ratio range than the conventional AC-DC buck-boost converter for DCM operation. Therefore, the proposed converter is suitable for universal input voltage (90~264 Vrms) and a wide output-power range. Moreover, the voltage stress on the DC-link capacitor is low. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.
 LINK
http://jpe.or.kr/archives/view_articles.asp?seq=760

Modeling and Control Method for High-power Electromagnetic Transmitter Power Supplies Fei Yu† and Yi-ming Zhang*

Modeling and Control Method for High-power Electromagnetic Transmitter Power Supplies Fei Yu† and Yi-ming Zhang* †*College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing, China
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=769

Study on the Influence of Distribution Lines to Parallel Inverter Systems Adopting the Droop Control Method Xuan Zhang*, Jinjun Liu*, Zhiyuan You†, and Ting Liu*

Study on the Influence of Distribution Lines to Parallel Inverter Systems Adopting the Droop Control Method Xuan Zhang*, Jinjun Liu*, Zhiyuan You†, and Ting Liu* *†Dept. of Electronic Engineering, Xi’an Jiaotong University, Xi'an, China Abstract This paper takes into account the influence of the different impedances of distribution lines on power distribution among inverters when the inverters are paralleled with the droop control method. The impact of distribution lines on the power distribution of inverters can be divided into two aspects. Firstly, since the distributed generators are in low voltage grids, there is resistive impedance in the distribution lines, which will cause control coupling and reduce system stability. The virtual negative resistive impedance of inverters is adopted in this paper to neutralize the resistive element of distribution lines and thus make the distribution line impedance purely inductive. Secondly, after solving the resistive impedance problem, the difference in the inductive impedance value of distribution lines due to the low density of distributed generators will cause an unequal share of reactive power. With regards to this problem, modification is put forward for the droop control strategy to share the reactive power equally. The feasibility of the design is validated by simulation and experimental results.
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=771