Dual mode AC DC AC converter for contactless power transfer system

A new type AC DC AC converter which can work in Buck or Boost mode is proposed in order to overcome the deficiencies of the primary circuit of the traditional contactless power transfer system. Through switching this two modes and turning the duty cycles of the switches, not only the resonant current amplitude of the primary resonant current can be controlled to be constant against a wide range variation of input voltage, but also the problems, such as surge current, high cost, complex control etc., caused by the DC filter and DC/DC converter in a traditional CPT system are effectively eliminated. The topology and operation principle of the proposed converter have been analyzed. The corresponding control strategy has been presented and verified by simulation results.     

A new family of zero current and zero voltage switching pulse width modulation converters

A new family of zero current and zero voltage switching (ZC ZVS) pulse width modulation (PWM) converters was proposed, based on a new ZC ZVS PWM switch cell. The main switches operate at ZCS on and off, the auxiliary switches operate at ZVS on and off, and the passive semi conductor devices in the ZC ZVS converters operate at ZCS on and off. In addition to operating at constant frequency and reducing commutation losses, the new converters have no additional current stress or conduct loss in the main switch in comparison to hard switching converters. The principle of the new ZC ZVS PWM Boost converter was analyzed. The simulation results of the ZC ZVS PWM converter are provided to verify the performance of the new ZC ZVS PWM converters.     

Modeling and control of An LCL bi-directional inductive power transfer system

Since there exist high-frequency switching networks and complicated operating modes in bi-directional inductive power transfer (IPT) system, it is easy to result in high harmonics and EMI interference. An LCL filter network is introduced to effectively filter out the unwanted harmonics in track current and reduce EMI interference. Based on a mathematical model of the power transmission established by complex analysis of the AC variables, under the condition of maximum transmission efficiency, the phase angle differences between the primary input voltage and secondary output voltage U·so are ±90° and the energy is respectively transferred in forward or backward direction. Moreover, the power magnitude can be controlled by adjusting the modulus of U·pi and U·so. In addition, to keep the track current constant, different phase-shifting control strategies are designed in the primary and secondary parts. Simulation and experimental results show that these strategies can not only adjust track current to keep constant but also dynamically change the direction and magnitude of power transmission according to the working conditions and actual needs of the system load to improve the system operating efficiency.     

多学科结合的新型农业技术推广体系探索

在实施“河北省第三次夏谷良种更新工程”的过程中,将生态区划理论和品种发育规律、栽培技术、新型推广模式研究及良种繁育等多个技术领域结合一起,探索出了一套新型农业技术推广体系,取得了较好的效果。其技术体系主要包括：①依据生态条件,将项目区划分为若干生态类型区;②筛选适宜的推广品种等技术主体;③进一步揭示主推品种在各类型区的特征特性和生育规律;④进行不同品种在各类型区的配套栽培技术研究;⑤探索切实可行的农技推广新模式。     

新型农村金融体系与农村信用合作

笔者分析了国外和中国台湾地区农村金融服务体制以及历史文化环境,从各国政府对农村金融的支持逐步从参与金融活动转变为更加重视运用法律手段和经济政策,阐述了中国发展和扶持农村合作金融必要性,勾画了中国新型农村金融服务体系的框架,并结合中国实际就发展农村合作金融提出了对策建议。     

Efficiency optimization matching strategy of continuously variable transmission system with reflux power

To solve the problem that the transmission efficiency of continuously variable transmission system with reflux power varies in a great range, and the traditional control strategy can’t make sure that the overall system is under ideal conditions, an economy control method based on system efficiency optimization is put forward. The engine/transmission efficiency numerical model and system optimization model are built. Taking Matlab/Simulink as the platform, objective throttle position control table and objective ratio control table are obtained by solving the optimization model. Furthermore, ECE+EUDC drive cycle simulation based on the fuel economy of sample car is carried out, and the simulation results indicate that the method of system efficiency optimization make fuel consumption reduce by more than 1.5%.     

GGH heat transfer enhancement and a new type heat exchangerin the desulphurization system of wet flue gas

This paper conducts in-tube heat transfer experiments in a three dimensional fin tube with 102 mm outer diameter.Compared with the smooth tube,the heat transfer enhancement ratio is between 1.65 and 1.7,and the pressure drop ratio is between 1.65 and 1.7.Based on the analysis of the heat transfer and tube surface temperature,a new type heat exchanger is put forward.Moreover,the design and calculation method is explored.The engineering example indicate that not only the tube surface temperature is higher than the smooth tube,but also the quantity of heat is increased by about 20% than the smooth tube.Compared with other types,the new type heat exchanger has a overall better performance.     

Design and implementation of a collaborative monitoring system

We designed a collaborative monitoring system based on JXTA. The system integrates P2P network technology with network management technology. We introduced the mechanism of JXTAs peer group, discussed the necessity of using a P2P network in a peer group application, presented the cooperative work scheme of P2P network, and emphasized the mechanism of peer group collaborative monitoring network when applying P2P network technology. The implementation method of the system was put forward by remotely monitoring the CISCO3640 port utilization ratio. The system features expansibility, usability, interoperability, high performance, decentralization, and robustness.     

Design of GIS-based monitoring and maintenance decision support system for urban sewage pipe network

Monitoring and maintenance of sewer system is important to city water environmental management. A method for pipeline monitoring and maintenance decision support system (PMMDSS) based on geologic information system (GIS) and decision making system (DSS) is developed for upgrading sewer system maintaining efficiency. Visual basic (VB) and standardized Active X components are employed in PMMDSS, which selected SuperMap Objects as the development platform. PMMDSS integrates the spatial and model system to achieve the decision analysis for the sewer system monitoring and maintenance. An application Software is developed based on a case study in Yuechi Country of Sichuan Province. The software can be used to dynamically monitor the heath condition and provide an optimum visual decision making platform for the city sewer system.     

Numerical calculation and experimental study of mass transfer coefficient of CO2 in circulating water system

To moniter the operation condition of circulating water system and realize real-time prediction of the pH variation of circulating cooling water, a mathematic model of pH variation tendency is set up and the mass transfer coefficientof gaseous CO2 is calculated. Then the validity of the model is verified by quasi-dynamic simulation experiment. Results illustrate that circulating water can achieve the gas-liquid equilibrium state after it fully contacts with gaseous CO2 in atmosphere, and the maximum error limit between the theoretical and the measured pH value is only 0.04. The pH variation tendency of quasi-dynamic system is in line with the predicting mathematic model and the A·KG is a constant when temperature(T）and spray flow(Q）are fixed. 10 5·A·KG=0.023 6Q－0.02 gives the relationship between A·KG and Q, when T is 40 ℃.     

Design of networking condition monitoring andfault diagnosis for wind turbine transmission system

In order to solve the incipient fault diagnose problem of the transmission system, a networking condition monitoring and failure diagnosis system based on B/S and C/S hybrid architecture for wind turbine transmission system is designed in the paper. Firstly, the paper analyzes the demands of condition monitoring and fault diagnosis system for wind turbine transmission system, and designs its overall framework and function modules. Then, combining with the data acquisition equipment, by the .NET and SQL Server platform, the paper designs condition monitoring and failure diagnosis system for wind turbine transmission system, which includes the functions of networking data acquisition, remote condition monitoring, signal analysis, fault diagnosis and database as well. The system has been successfully applied to a condition monitoring and fault diagnosis of wind turbine transmission system.     

The equivalent enthalpy drop theory calculation of the ejector heaters applied for low-pressure feed water heater system of thermal power unit

There is much exergy loss in low-pressure feed water heater system of the thermal unit. The thermo-economic characters by the equivalent enthalpy drop method while the low-pressure heater was replaced with the ejector heater. At the same time, the thermo-economic characters formulas for the different factors were also gotten. Based on these results, the thermo-economic changing features were analyzed for the low pressure heaters replaced with the ejector heaters of the N600-165/535/535 units, and the results were compared with the normal heat balance method. The results show that the ejector heaters can reduce the exergy loss efficiently, and the thermo-economic effects is the best for replacing the all low-pressure heaters with the ejector heaters, and its efficiency can be increased by 0.263%. The given equations of this paper can be used for analyzing the thermal economic effects.