论构筑陕西防洪体系的基本思路

本文从全省防洪现状及经验教训出发 ,按实施西部大开发战略的安全保证要求 ,就主要河流水系防洪体系的建立提出了一些基本思路 ,供决策参考。     

Genetic algorithm-based induction machine characterization procedure with application to maximum torque per amp control

There has been considerable research in developing improved induction motor models. One recently developed model simultaneously includes magnetizing path saturation, leakage saturation, and a highly flexible transfer function approach to represent the rotor circuits. This alternate QD model (AQDM) is also computationally efficient in that it is noniterative at each time step. It is considerably more accurate than the classical QD model (CQDM). However, the suggested characterization procedure is complicated and time consuming. This paper proposes a new characterization procedure for the AQDM. The proposed procedure employs a genetic algorithm (GA) as an optimization engine to identify the parameters of the AQDM by simultaneously considering per-phase fundamental frequency impedance and stand-still frequency response (SSFR) impedance. The proposed approach is validated by comparison of current ripple predictions (to validate high-frequency model behavior) and by application to maximum torque per ampere control design (to validate fundamental frequency model behavior). The proposed procedure is significantly more straightforward than the other published method of obtaining AQDM parameters.     

Design consideration of low temperature differential double-acting Stirling engine for solar application

This paper presents design considerations to be taken in designing of a low temperature differential double-acting Stirling engine for solar application. The target power source will be a thermosiphon solar water heater with integrated storage system, which will supply a constant source temperature of 70 °C. Hence, the system design is based on a temperature difference of 50 °C, assuming that the sink is kept at 20 °C. During the preliminary design stage, the critical parameters of the engine design are determined according to the Schmidt analysis, while the third order analysis was used during the design optimisation stage in order to establish a complete analytical model for the engine. The heat exchangers are designed to be of high effectiveness and low pressure-drop, and are made from a 0.015 m tube, while the porosity of the steel wool of 0.722 is used for the regenerator matrix. Upon optimisation, the optimal engine speed is 120 rpm with the swept volume of 2.3 l, and thus the critical engine parameters are found to be the bore diameter of 0.20 m. In addition, the volumes of heater, cooler and regenerator are 1.3 l, 1.3 l and 2.0 l volumes, respectively.     

Investigation of PEMFC fault diagnosis with consideration of sensor reliability

Despite the wide range of applications for the polymer electrolyte membrane fuel cell (PEMFC), its reliability and durability are still major barriers for further commercialization. As a possible solution, PEMFC fault diagnosis has received much more attention in the last few decades. Due to the difficulty of developing an accurate PEMFC model incorporating various failure mode effects, data-driven approaches are widely used for diagnosis purposes. These methods depend largely on the quality of sensor measurements from the PEMFC. Therefore, it is necessary to investigate sensor reliability when performing PEMFC fault diagnosis.In this study, sensor reliability is investigated by proposing an identification technique to detect abnormal sensors during PEMFC operation. The identified abnormal sensors will be removed from the analysis in order to guarantee reliable diagnostic performance. Moreover, the effectiveness of the proposed technique is investigated using test data from a PEMFC system, where fuel cell flooding is observed. During the test, due to accumulation of liquid water inside the PEMFC, the humidity sensors will give misleading readings, and flooding cannot be identified correctly with inclusion of these humidity sensors in the analysis. With the proposed technique, the abnormal humidity measurements can be detected at an early stage. Results demonstrate that by removing the abnormal sensors, flooding can be identified with the remaining sensors, thus reliable health monitoring can be guaranteed during the PEMFC operation.     

Optimal reserve capacity allocation with consideration of customer reliability requirements

An algorithm for determining optimal reserve capacity in a power market is presented in this paper. Optimization process in the proposed algorithm is based on the cost-benefit trade off. Market clearance is executed with consideration of uncertainties of power system components in an aggregated environment. It is assumed that both generating units and interruptible loads participate in the reserve market. In addition, customers’ reliability requirements are considered as constraints for decision making process of ISO. The rendered method considers random outages of generating units and transmission lines and determined outage of interruptible loads and employs Monte Carlo Simulation (MCS) for scenarios generation. Unlike previous methods in which a constant value is assumed for cost of the energy not supplied, a flexible value for this parameter is applied which shows an important effect in the evaluation results. The performance of the proposed method has been examined on the IEEE-Reliability Test System (IEEE-RTS).     

考虑空气污染因素的光伏发电量回归分析

人类活动产生的大气污染物对到达地面的太阳总辐照和光谱分布都会产生一定影响。文章利用一座分布式电站的实测数据,通过模型回归分析的统计学方法,定量地研究了空气质量和光伏发电量之间的直接关联强度。同时,考虑了温度、风力、云量和太阳光入射角度等气象、物理参数对于光伏发电量的影响。利用该回归模型,可以根据公开气象资料对小型光伏电站的发电量进行简单预测。     

Design of multiperiod hydrogen network with flexibilities in subperiods and redundancy control

To ensure the operational flexibility of multiperiod hydrogen network and reduce the capacity redundancy of compressors, a method for design of multiperiod hydrogen network is proposed based on flexibility analysis. In the proposed method, an initial multiperiod hydrogen network is obtained by solving the single period optimization models of hydrogen networks for each subperiod, where the minimal capacities of compressors in different subperiods are assigned. Then, the flexibility of the initial multiperiod hydrogen network is examined and improved by solving a proposed flexible design model to identify the bottlenecks of operational flexibility of each subperiod. The additional capacities of compressors and flowrates of hydrogen utility in each subperiod are then determined to finalize the design of the flexible multiperiod hydrogen network with the redundancy control of compressors capacities. The application of the proposed method are illustrated via a hydrogen network of a refinery in China.     

A hybrid GA approach for OPF with consideration of FACTS devices

This letter presents a hybrid genetic algorithm (GA) method to solve optimal power flow (OPF) in power systems incorporating flexible AC transmission systems (FACTS). In the solution process, GA is integrated with conventional OPF to select the best control parameters to minimize the total generation fuel cost and keep the power flows within the security limits. A case study using an IEEE test system is presented to demonstrate its applicability     

Design consideration of sustainable self‐sufficient energy system using ferroelectric material for wearable healthcare

Design of the sustainable self‐sufficient energy generator and storage devices using ferroelectric material were considered for wearable healthcare device. Recently, personal health‐monitoring system is expected to be one of the most important and attractive applications of wearable electronics. It becomes more important for us to develop power generator and storage devices used in monitoring our health condition status on an aging society. The power generator and storage devices are desirable to be embedded into clothes or textile intangibly. In this paper, button type solar cell for power generator and film capacitor on fiber for power storage were considered by using ferroelectric material. The target power consumption for wearable healthcare device is more than 3.6 mW for communication means and sensing ECG, SpO₂, temperature, heart rate, and blood pressure that were essential for our health condition monitoring. The target capacity of power storage is more than 150 mAh for 5 days' operation. Clothes are thought to be suitable for embedding sufficient energy system. One proposed circuit that consists of solar cell and film capacitor is considered. The button type solar cell of the four pieces of 20 mm diameter and the film capacitor on fiber are proposed as power generator and storage. The proposed circuit will make it possible to use the healthcare devices more than 5 days without sunshine when we put on clothes of more than 160 g such as thin coat or outerwear. Moreover, the proposed circuit will make it possible to use the devices more than 30 days without sunshine when we put on clothes of more than 960 g such as thick coat or outerwear. As we don't forget to put on clothes that embedded the self‐sufficient energy system, the self‐sufficient system will become useful for sustainable society in the future. Copyright © 2016 John Wiley & Sons, Ltd.     

Design and control of a direct drive wind turbine equipped with multilevel converters

This paper concentrates on the design and control of a three-level grid side converter (GSC) for direct drive high power wind turbines. The three-level, neutral point clamped (NPC) topology was investigated. The proposed control scheme, based on vector current control, offers very satisfying performances regarding to structure stability and grid connection requirements (GCR). In order to have an accurate evaluation of grid voltage source, two grid synchronization methods are developed and their performances are compared. The GSC performances are evaluated under both normal and grid fault conditions. Simulation results show that stability is maintained during voltage dips and that the proposed direct drive wind turbine satisfies completely GCR.     

风光互补路灯控制系统的设计

对风光互补路灯的使用特性进行了分析;对现有各种风光互补路灯控制系统所存在的问题进行了探讨和研究;提出了一种新的风光互补控制方法——逐步刹车保护法.逐步刹车保护法能很好的解决目前现有系统出现的刹车故障问题,提高了风光互补系统的可靠性.     

Operation of offshore wind farms connected with DRU-HVDC transmission systems with special consideration of faults

The diode rectifier unit (DRU)-based high-voltage DC (DRU-HVDC) system is a promising solution for offshore wind energy transmission thanks to its compact design, high efficiency, and strong reliability. Herein we investigate the feasibility of the DRU-HVDC system considering onshore and offshore AC grid faults, DC cable faults, and internal DRU faults. To ensure safe operation during the faults, the wind turbine (WT) converters are designed to operate in either current-limiting or voltage-limiting mode to limit potential excessive overcurrent or overvoltage. Strategies for providing fault currents using WT converters during offshore AC faults to enable offshore overcurrent and differential fault protection are investigated. The DRU-HVDC system is robust against various faults, and it can automatically restore power transmission after fault isolation. Simulation results confirm the system performance under various fault conditions.     

Heat and mass transfer in adsorbent bed with consideration of non-equilibrium adsorption

In the solid adsorption refrigeration cycles, the actual adsorption processes are all non-equilibrium. To investigate the heat and mass transfer in adsorbent bed, mathematical model is established and solved by a numerical method. The relations between adsorption temperature, adsorption velocity, adsorption quantity, coefficient of performance (COP), specific cooling power (SCP) and time are discussed during the process of cooling the adsorbent bed. The relations between desorption temperature, desorption velocity, desorption quantity and time are discussed during the process of heating the adsorbent bed. It indicates that there is a peak value for adsorption velocity in the adsorption process and there is also a peak value for desorption velocity in the desorption process. It also shows that the changing rate of the adsorbent temperature tends to let up, and the coefficient of performance value grows nearly linearly in the adsorption process and there is a peak value of SCP in the adsorption process.     

Analytical determination of permeability of porous fibrous media with consideration of electrokinetic phenomena

Flow behavior in porous fibrous media with consideration of electrokinetic phenomena is investigated based on a linearized Poisson–Boltzmann equation and Navier–Stokes equation. An analytical solution of effective permeability of porous fibrous media as functions of porosity, dimensionless local averaging net charge density and dimensionless electric resistance number is derived in this paper. The influences of the electrokinetic phenomena can be measured by the dimensionless electric resistance number, which is proportional to the square of the liquid dielectric constant, the solid surface Zeta potential and inversely proportional to the liquid dynamic viscosity, electric conductivity and the square of the maximum pore radius. The analytical results show that when the dimensionless electric resistance number is small and the porosity is large, the dimensionless total flow rate shows a nearly uniform distribution. When the dimensionless electric resistance number is large, the resistant effects of the electrical double layer (EDL) become so significant that the superficial velocity decreases. The effective permeability of the porous fibrous media decreases correspondingly. Furthermore, the theoretical predicted effective permeability values are compared with experimental data, and good agreement is observed between the two. It shows that the mathematical model for the effective permeability of porous fibrous media with consideration of electrokinetic phenomena is satisfactory.     

全天候太阳方位跟踪控制系统的设计

采用光感跟踪与时间跟踪相结合的方法,设计了全天候太阳方位跟踪控制系统。该系统包括监测装置、跟踪方式转换控制模块和双跟踪方式控制模块。监测装置监测天气状态为跟踪方式转换控制模块提供判断依据,跟踪方式转换控制模块发出指令启动相关跟踪方式,控制传动及支撑装置的运动,以改变太阳能电池板采光面的位置。系统的跟踪精度高,跟踪能耗低。     

定日镜自动控制系统设计应用

一前言 目前中国太阳能低温热利用已经走到了世界的前列,中国的发展模式得到了世界的关注和认可,然而我国的太阳能发电技术还只是处于起步阶段.太阳能发电的两种形式是太阳能光伏发电和太阳能热发电,太阳能热发电在国外有几十年的发展历史,在我国还只是一个新兴的产业.太阳能热发电的三种主要形式是塔式、槽式和碟式,其中塔式高温热发电具有能大规模推广,实现产业化的优点,发展前景比较广阔.     

Design of a scaled wind turbine with a smart rotor for dynamic load control experiments

The ever increasing size of wind turbines poses a number of design issues for the industry, like increasing component mass and fatigue loads. An interesting concept for reducing fatigue loads is the implementation of spanwise distributed devices to control the aerodynamic loading along the span of the blade, thus mitigating fluctuations in loading and adding damping to the blade modes. This is usually referred to as the smart rotor concept. In the design of such a rotor, as compared to a traditional one, the integration of sensors and actuators poses additional design challenges. In the research discussed in this paper, a scaled smart rotor was designed and constructed to study its fatigue load reduction potential. A 1.8 m diameter rotor was manufactured and equipped with trailing‐edge flaps. The flaps were based on piezo electric Thunder actuators that allow for high‐frequent actuation. The dynamic strain behaviour of the blade was analysed for optimal placement of the sensors. Several sensors that record the strains and accelerations at different locations along the blade were implemented, but the controller was based on a piezo electric strain sensor. The rotor blades were mounted on a small turbine in the Delft University's Open Jet Facility wind tunnel and a mathematical state space model was obtained by using dedicated system identification techniques. Single‐Input Single‐Output, Multi‐Input Multi‐Output ??_∞ feedback and feedforward controllers were designed, each focusing on different parts of the load spectrum. The rotor was tested at 0 and 5° yaw angles, with and without load control. A significant reduction of the dynamic loads was attained. Copyright © 2010 John Wiley & Sons, Ltd.     

考虑实际气体性质的三轴燃气轮机中冷循环性能优化

考虑实际气体的热力性质,建立了三轴燃气轮机中冷循环的热力模型,以循环功率和效率为优化目标,对中间压比(或低压压气机压比)的分配进行了优化,同时分析了低压压气机进口气流温度、中冷度和总压比对循环性能的影响。研究发现,与不考虑实际气体热力性质的研究结论相比,循环功率或效率最大时的中间压比并不等于高压压气机压比。     

Heat transfer enhancement of transverse ribs in circular tubes with consideration of entrance effect

The heat transfer enhancement of transverse ribs in circular tubes with a length-to-diameter ratio of 87 was experimentally investigated. The mean heat transfer and friction data were obtained for the air flow started from the entrance. An isothermal surface condition was considered. The rib pitch-to-tube diameter ratio (p/d) was in the range 0.304–5.72; the rib height-to-tube diameter ratio (e/d) was in the range 0.015–0.143; the considered Reynolds number (Re) was in the range 4608–12,936. The mean Nusselt number (Nu) and friction factor (f) were individually correlated as a function of p/d, e/d and Re. A critical e/d, equal to 0.057, was found. For e/d < 0.057, the f is proportional to e/d; for e/d ⩾ 0.057, the f is proportional to (e/d)^2.55. A performance map, indicating the corresponding heat transfer enhancement index (r₁) and efficiency index (r₂) for various p/d and e/d, was constructed. This performance map clearly indicates the ranges of p/d and e/d with a high r₂.     

铁路起重机智能化集成控制系统的设计

介绍了铁路起重机集成化操作与智能化控制系统的设计思想及软、硬件设计技术。该系统综合利用智能技术与计算机技术等对我国现有铁路起重机主导产品进行系统的技术改造和性能提升,使铁路起重机成为自主创新与技术引进相结合的新一代智能化产品。