Analysis of the Temperature Limit of Dynamic Water Intake of Open loop Surface Water Source Heat Pump Systems

Energy consumption of water intake is one of the key factors for energy saving in the application of the open loop surface water heat pump system. An energy efficiency ratio coupling model for open loop surface water source heat pump systems was established on the basis of the energy consumption model for the water intake and the heat pump units. According to energy saving rate and regulation of energy consumption of water intake, dynamic temperature limits of water intake in different water supply temperature of cooling tower and different pump head were proposed so as to find a calculation method of temperature limits of water intake of open loop surface water heat pumps. Moreover, the energy saving rate of surface water source heat pump systems compared with traditional air conditioning systems under various condition was also calculated.     

Analysis on mechanical properties evolution ofoutburst coal under cyclic loading

Briquette specimens made of outburst coal are taken as research objects, and both mechanical properties evolution under cyclic loading and law of hysteretic curve evolution under different loading level are studied. The results show that hysteretic loop is composed of load-unload curve when briquette specimens are studied under cyclic loading, and secondary hysteretic loop is produced from the second cycle. The area composed by hysteretic curve becomes smaller with the addition of cycle numbers. The relation between deformation response and loading level is very close. Load-unload curve of hysteretic curve is expressed by conic, and the change law of fitting parameters of conic is very regular with the addition of cycle numbers, but the regularity of the law with loading level isn’t very obvious; the minis sign of fitting parameters of conic is opposite.     

Improvement and simulation on direct torque control system of permanent magnet synchronous motor

To solve the problems of large flux, torque ripple and inconstant inverter switching frequency in conventional direct torque control (DTC), a space vector modulation (SVM) technique is introduced to the conventional PMSM-DTC system and analyzed thoroughly based on the mathematical model. This novel control method which enjoys the advantages of VC and DTC has only one easy adjustable PI regulator and is easy to realize. The simulation verifies that this control system is capable of effectively improving the steady state performance and keeping the excellent dynamic performance of the PMSM-DTC system simultaneously and remain the switching frequency constant.     

谷物冷却机环流冷却技术在浅圆仓中的应用研究

本文探讨增加一系列风管和控制机构使浅圆仓冷却通风形成环流状态,通过对谷物冷却作业过程中粮堆热交换后所排出空气进行回收并重复利用,达到节省能源,提高谷物冷却机作业能力和效率的目的,并对该套装置潜在的效益和在低温储粮中的作用进行了评估.     

The design of torque dynamic sliding mode controller in permanent magnet synchronous generator for wind turbine

Permanent magnet synchronous generator for wind turbine is a multivariable nonlinear system with strong coupling. Considering the influence of the volatile parameters of the generator on the performance of vector control, the torque dynamic sliding-mode control strategy is further studied. The proposed first order dynamic sliding-mode control strategy reduces the chattering by using a new switch function constituted with derivative element. With the dynamic sliding-mode controller in the power outer loop, the PMSG vector control system shows excellent robustness and insensitivity to the parameters and disturbance, which is confirmed by simulation.     

Discussion on the Hydraulic Calculation Method of Loop Heating Pipe Network

The authors definitely make out the concept of loop main pipeline, supplying main pipeline and ramiform branch line, as well as the order of their hydraulic calculation. Then they puts forward the principia of how to study out the direction of loop main pipeline and presents the method of making flux initial distribution. The matrix of loop main pipeline hydraulic square dispersion is set up. The node referenced pressure is defined and the equation of how to calculate it is deduced. A software is developed to calculate the loop main pipeline hydraulic square dispersion. The method of calculating ramiform branch margin impetus is given.     

Modeling and Simulation of the Doubly Fed Generatorwith the Matrix AC-AC Converter as an Exciter

According to the space vector modulation method of the AC DC AC converter,the switch control scheme of the matrix AC AC converter is deduced,and the model of a three phase matrix AC AC converter is constructed. According to the mathematic model of the doubly fed generator and the excitation control principle based on dynamical synchronous reference frame,the simulation model of the generator and excitation controller are established,then the modeling and simulation of the doubly fed generator system with the matrix AC AC converter as an exciter are implemented.The steady state and transient characteristics of the system are simulated,the harmonics of the EMF and stator?rotor current are researched.     

电网的统一时钟系统

介绍现有几种时钟系统，并着重介绍电视场运程同步时钟系统的工作原理及其在电网应用的实施方案。该系统具有投资小、时间精度高、易于实现的特点，可以使整个电网的时间达到精确统一，从而提高SOE功能记录事件顺序间的时间分辨率。     

Coordinated pressure control of a regenerative braking system based on a hybrid electric vehicle with an integrated startor and generator

With a focus on a Changan hybrid electric vehicle (HEV) with an integrated startor and generator (ISG), strategies for braking force distribution and coordinated pressure control are put forward, and a dynamic braking control model is constructed for off     

水轮机尾水管涡带压力脉动同步及非同步特性研究

尾水管涡带是混流式水轮机在部分负荷工况运行时尾水管内出现的一种螺旋状涡旋运动,其诱发的压力脉动对水轮机运行稳定性有直接影响且易造成疲劳破坏。基于SST k-ω湍流模型对运行在42. 35%额定功率的某混流式模型水轮机进行了尾水管内部流动特性的试验测试与数值研究,数值压力脉动幅值及主频与试验测试吻合度好,误差分别约为2. 70%和2. 62%。尾水管内出现进动涡带时,测点压力均作0. 25倍转频的周期性脉动,涡带扫过测点时,其压力最低。位于涡带运动轨迹附近的压力测点,其压力幅值最高。为了进一步阐明尾水管涡带的复杂流动特征及其动力学特性,将尾水管压力信号分解为同步分量及非同步分量。研究发现,分解后的非同步分量对原始信号有较强的依从性,其幅值较高且保持主频为0. 25倍转频,而同步分量主频发生变化且压力脉动幅值较小,表明非同步分量对尾水管涡带的形成贡献大于同步分量。尾水管锥管段不同高程上同步及非同步分量幅值的量化分析表明,非同步分量幅值绝对占优,沿流动方向非同步分量幅值先增大后减小,而同步分量幅值逐渐增加。