With the rapid development of railway transportation, using a locomotive and vehicle rolling vibration test bench for dynamic simulation testing is one of the extremely important testing methods in the current locomotive and vehicle development process. The rolling vibration table simulates the dynamic changes of the actual track by applying excitation to a finite radius track wheel. The measurement error of the spatial geometric parameters of the track wheel has an undeniable impact on the bench test. This paper proposes a method for measuring the geometric parameters of a rolling vibration test bench for locomotives and vehicles. Using the perspective projection theory, a geometric parameter measurement model for the rolling vibration test bench is established, and a measurement system calculation program is developed to achieve high-precision measurement of the static geometric parameters of the rolling vibration test bench for locomotives and vehicles.

Based on the operation process of vehicle traction converter, the design scheme of phase change cooling system is proposed, and the evaporation heat transfer process and flow characteristics of working medium in cold plate with parallel channels are theoretically calculated and experimentally studied. By comparing the pressure and temperature changes of each measuring point of the system under different heating power and flow conditions, the flow resistance of two-phase working medium and the heat transfer performance of cold plate are studied. Experimental results show that the decrease of flow rate or the increase of heating power will increase the vapor quality of channel outlet and wall temperature. At the same time, comparing the calculation results of the experimental correlation of frictional pressure drop and heat transfer of two-phase flow with the experimental data, it can be seen that the flow and heat transfer process of two-phase fluid in parallel channels can be well simulated and estimated by using a separated two-phase flow model and Steiner-Taborek asymptotic method.

随着可再生能源工业的发展对发电机技术提出更高容量和更大功率密度的需求,高温超导发电机在海上风力发电机领域有着广阔的应用前景.中国科学院电工研究所与上海电气集团上海电机厂有限公司合作研究高温超导发电机技术并研制基于国产YBCO带材的500 kW高温超导发电机原理样机.500 kW高温超导发电机为首台基于国产YBCO超导带材的高温超导发电机.目前,超导发电机已经完成研制工作并进行满负荷运行测试,电机运行良好,各项指标依据国标测试达到预期值.该文着重介绍500 kW高温超导发电机系统的研制工作,其中包括国产YBCO带材和9％Ni低温导磁钢的电磁特性研究,超导励磁绕组的优化设计和研制,同时介绍500 kW高温超导发电机的系统级测试工作,包括空载特性、负载特性、满载效率,并给出相应实验测试结果.

Evaporative cooling technology is an effective cooling method with high reliability and economic performance. Based on the experimental and theoretical analysis for equivalent model in previous researches, a real size of 30MW turbo generator stator bars model was designed and established. The stator coil internal evaporative cooling capacity and characteristic at different heat loads and different coolant flow were analyzed in this paper. At the same time, experimental results verifies the circulation system rationality and reliability under fault conditions, such as the circulation pump is out of service suddenly or cooling water is cut off in the condenser.

The sensorless control strategy has become one of the important research directions of brushless DC motors. Researchers have proposed a variety of rotor position signal detection methods. Now, brushless DC motor position sensors usually use the back EMF to detect the zero-crossing point. While the zero-crossing point of the back EMF of the non-conducting phase winding is detected, and then delay 30° electrical angle to obtain the commutation time. But the method needs to reconstruct the neutral point of the motor with a certain error. In order to avoid the influence of the error, the paper studies and analyzes the rotor position detection technology based on the line voltage difference based on the traditional back EMF zero-crossing signal detection technology. Finally, a test platform based on STM32F103 development board was built. The feasibility of the method was verified by the actual operation of the motor.

Due to high power density, high efficiency and outstanding dynamic characteristics, high temperature superconducting (HTS) machine shows a good application prospect in ship proportion and new energy generation. To ensure the safe operation of the HTS machine, the wireless online monitoring system to determine that whether HTS has failed is necessary. An online monitoring system was designed by detecting the voltage, environment temperature and liquid nitrogen level and the system was applied to the 500kW HTS machine. The experiment result shows that the wireless online monitoring system designed in this paper sufficient accuracy and reliability.

首先,针对传统预测转矩控制磁链和转矩脉动较大、开关频率不固定等问题,将一种占空比调制方法应用于传统预测转矩控制中以改善其控制性能.其次,针对传统预测转矩控制加入占空比调制后算法仍较复杂的问题,基于定子磁链坐标系对磁链和转矩实现完全解耦,并将转矩误差转换为电压矢量作用时间,消除了权重系数,加入占空比调制实现了一种更为简单的预测转矩控制.此外,针对模型参考自适应观测器参数鲁棒性差、滑模观测器开关抖振大等问题设计了自适应滑模观测器,将其应用于优化后的预测转矩控制中,比较了滑模观测器和自适应滑模观测器的稳定性和参数鲁棒性.最后,通过仿真分析证明所提算法以及自适应滑模观测器的优越性.

Considering the disadvantages such as large torque ripple and unfixed switching frequency of the traditional direct torque control (TDTC), a deadbeat predictive torque control strategy (DB-PTC) based on stator flux coordinate was proposed. First of all, the control principle of TDTC and the reason of large flux and torque ripple were analyzed. Secondly, due to the fact that the parameters setting the controllers are complex and the control effect is not ideal in the SVM-DTC and the complex strategy with large computation in the model predictive torque control (MPTC) and DB-MPTC, the decoupling control of the stator flux and the torque was realized based on the stator flux coordinate, which combined the deadbeat theory to calculate the voltage vector and simply realize the decoupling control. Finally, the simulation results show that the strategy has the advantages of simple strategy and low computation while can effectively eliminate the torque ripple.

铜包铝管母线是铝管外包覆薄铜管的新型节能输电母线,两种导体共同分担承载的电流,同时内部较厚的铝管起到机械支撑的作用.在相同频率和幅值的交流电流情况下,铜管的集肤效应深度大于铝管.这种复合结构能有效增加母线交流载流能力,减小母线重量和阻抗以及过流面积,降低母线损耗和温升,提高能效.本文采用数值计算和有限元仿真方法,得到了铜包铝管母线的温升和分布情况,并进行了实验,计算结果与实验数据相符.最后通过对比常规铜排母线和铜包铝管母线的实验结果,显示出铜包铝管母线在节材和节能方面的优异效果.

This paper summarized the heat problem and water cooling technology of HVDC converter valve, and presented applying evaporative cooling technology to HVDC field. A model was designed for the 5-inch thyristors, composed of a wall-type evaporator, gas collecting pipe, liquid tube and condenser, etc. Based on this model, the temperature fields of the thyristors in different power conditions are calculated by FEM. The percentage error between simulation data and experimental result is under 8%. And the results have verified the accuracy of the calculation and test. Studies have shown that the application of evaporative cooling technology makes the temperature distribution of thyristors more uniform, and the increasing of cooling margin can guarantee the current-carrying capacity of HVDC converter valve unit. These results will offer theoretical and design support for using of evaporative cooling technology in HVDC station.

To enhance the reliability, sensorless vector control strategy based on sliding mode observer was adopted in flux-switching permanent magnet machine. The rotor position and speed estimation algorithm was obtained according to the voltage equation on αβ coordinate system of flux-switching permanent magnet machine, which contains the information of rotor positron. Further, a flux-switching permanent magnet machine prototype and its control system were designed. At last, the sensorless control strategy based sliding mode observer was designed and verified well by experiments.

As heat flux densities grow higher, the evaporative cooling system seems to be the most effective way of removing heat from high current rectifier equipment. In order to validate the evaporative cooling system can substitute the water cooling in engineering application and get the actual operational effect, also to provide the DC power supply demands for 200MW turbogenerator model, the high current rectifier equipment with self-circulation evaporative cooing system is designed. The temperature distribution characteristics are discussed. The experimental results show that the high current rectifier equipment with the evaporative cooling system has the advantage of high efficiency, energy-saving, high-reliability, low operational cost.

A guiding principle for data reduction in statistical inference is the sufficiency principle. This paper extends the classical sufficiency principle to decentralized inference, i.e., data reduction needs to be achieved in a decentralized manner. We examine the notions of local and global sufficient statistics and the relationship between the two for decentralized inference under different observation models. We then consider the impact of quantization on decentralized data reduction, which is often needed when communications among sensors are subject to finite capacity constraints. The central question we intend to ask is: if each node in a decentralized inference system has to summarize its data using a finite number of bits, is it still optimal to implement data reduction using global sufficient statistics prior to quantization? We show that the answer is negative using a simple example and proceed to identify conditions under which sufficiency based data reduction followed by quantization is indeed optimal. They include the well known case when the data at decentralized nodes are conditionally independent as well as a class of problems with conditionally dependent observations that admit conditional independence structure through the introduction of an appropriately chosen hidden variable.

This paper proposes an orthogonal frequency division multiplexing passive optical network (OFDM-PON) scheme by using frequency hopping at physical layer to enhance system security. The transmitted signal is concealed with frequency hopping pattern, which is generated by Latin Square. A 10 Gbps FH-OFDM signal transmission system has been realized over 25 km standard single mode fiber (SSMF). Simulation results show our proposed scheme has excellent anti-interference and anti-intercept capability.

Optimal transmit power allocation strategies are proposed for an energy harvesting estimation system, where energy can be harvested from the environment and buffered in a battery for future use. With the aim of minimizing the mean squared error at the receiver, two types of side information (SI) available to the transmitter are considered: causal SI (energy harvested in the past) and non-causal SI (energy harvested in the past, present and future). For the case where non-causal SI is available and battery storage is unlimited, it is shown that the optimal power allocation can be attained by a simple water-filling-like procedure, where the water level follows a non-decreasing staircase function. Dynamic programming is used to optimize the allocation policy when causal SI is available. The issue of unknown transmit power at the receiver is also addressed.

The prevalent use of unmanned vehicles in military and civilian applications requires the existence of robust and high throughput communication with airborne platforms. Real channel measurements are conducted and the analysis supports the use of MIMO communications for such applications due to its potential throughput advantage. Unique challenges and the ways to address them are described in detail. In particular, the lack of scattering and the blockage of line of sight may lead to rank deficient channel matrices, which are exacerbated due to the absence of channel state information at the transmitter. A variable rate MIMO scheme is proposed to overcome these challenges in order to realize the promising throughput gain afforded by MIMO communication.

Direct drive (DD) wind turbine has lots of benefits, such as low noise, small size and high efficiency in low wind speed, etc. therefore it will be the main model in future wind power market. This paper presents different structures of DD wind turbines from major wind power manufacturers and compares several main drive train structures. Result of this research can provide relevant reference for manufacturers of DD wind turbine.

This paper focuses on designing a distributed medium access control algorithm that aims at achieving time fairness among contending stations and throughput maximization in an 802.11 wireless LAN. The core idea of our proposed algorithm lies in that each station needs to select an appropriate contention window size so as to fairly share the channel occupancy time and maximize the throughput under the time fairness constraint. The derivation of the proper contention window size is presented rigorously. We evaluate the performance of our proposed algorithm through an extensive simulation study, and the evaluation results demonstrate that our proposed algorithm leads to nearly perfect time fairness, high throughput, and low collision overhead.

The sum capacity of a class of discrete memoryless interference channels is determined. This class of channels is defined analogous to the Gaussian Z-interference channel with weak interference; as a result, the sum capacity is achieved by letting the transceiver pair subject to the interference communicates at a rate such that its message can be decoded at the unintended receiver using single user detection. Moreover, this class of discrete memoryless interference channels is equivalent in capacity region to certain discrete degraded interference channels. This allows the construction of a capacity outer-bound using the capacity region of associated degraded broadcast channels. The same technique is then used to determine the sum capacity of the discrete memoryless interference channel with mixed interference. The above results allow one to determine sum capacities or capacity regions of several new discrete memoryless interference channels.

Cooling technology of rotor is a key technology for high temperature superconducting electrical machines. Based on the theory of rotating piping flow and pool boiling, the heat transfer principles of cooling methods are proposed, which are including integrated rotating thermosyphon, distributed rotating thermosyphon, immersion cooling, layered open evaporative cooling, and rotating piping evaporative cooling, respectively. The temperature distributions of cooling methods of rotor section are simulated by ANSYS steady state model. An experimentally integrated test platform adaptable to five cooling methods is designed and built up. Experiments on characteristics of heat transfer and flow are investigated. The performances of five cooling methods were contrasted, and the results are that immersion cooling makes the best performance and the others are different with it. Moreover, the experimental results are compared with the simulated ones. It is verified that the simulations could match the experiments well.