Power conditioning system for grid-connected photovoltaic system

This study develops a new control strategy for an expandable grid-connected photovoltaic (PV) system. The proposed system performs dual functions of a PV generation and an active power filter, or either one. To this end, the grid current, instead of output current of the converter, is shaped to be a sinusoidal current in phase (or opposite phase) with the grid voltage. Furthermore, its reference current is generated in multiplying the voltage loop controller output by the grid voltage waveform, and therefore non-active components analysis for harmonics elimination and reactive power compensation in the conventional design is not necessary. As a result, the algorithm is simple and easy to implement, and only one sensor for current detection plus two voltage sensors are required. Experimental results verified the effectiveness of the proposed method.     

微型热电联产系统

作为一种以家庭住宅为单位的全新的能源供应思路和技术 ,微型热电联产系统代表了未来家庭能源供应的主要方向。本文分别介绍了基于斯特林发动机、内燃机和燃料电池的三种微型热电联产方式的原理及特点 ,并进行了系统的性能比较     

基于模型的航天器推进系统故障诊断

设计了基于模型的推进系统的故障诊断系统,根据推进系统的结构和行为模型,分析出各组件可处的工作状态及组件之间的连接关系,利用JMPL建模语言建立了推进系统各组件的定性模型。把推进系统模型和系统场景文件输入给诊断推理引擎,可实现推进系统的实时诊断。诊断结果表明,建立的推进系统模型是准确可靠的,开发的诊断系统能有效地找出故障组件并确定故障组件的状态。     

Monitor system design of distributed wind turbine-energy storage system

风储互补配合是提高风电质量、增加风电可控性、解决风电并网问题的有效途径。本文对“一机一储”的分布式风储系统进行了分析,探讨了分布式风储系统设计的整体方案,对风储能量管理系统监控后台的数据记录、监控界面和报表生成等进行了功能设计。风储系统实际运行效果表明,该监控后台能够很好地实现监控显示、历史数据记录、运行模式设定、统计分析和报表生成等功能,系统运行可靠,可为风储系统的推广应用提供一定的参考。     

Artificial immune system for fixed head hydrothermal power system

This paper presents artificial immune system for optimal scheduling of thermal plants in coordination with fixed head hydro units. Numerical results of two test systems have been presented to demonstrate the performance of the proposed algorithm. The results obtained from the proposed algorithm are compared with those obtained from differential evolution, particle swarm optimization and evolutionary programming technique. From numerical results, it is found that the proposed artificial immune system based approach is able to provide better solution than differential evolution, particle swarm optimization and evolutionary programming in terms of minimum cost and computation time.     

Performance analysis of thermal energy system with linear system method

The paper addresses the system performance of coal-fired power unit with changed auxiliary system or other localheat disturbance.The idea of state space model is imported and the universal formula for the calculation of sys-tem performance output is deduced on the system state equation.Two important vector of system are worked outunder linear system assumption and transform.The transfer matrix is the characteristics of system itself and isconstant for a similar condition,which greatly facilitates the analysis.The concept of thermal disturbance vectoris proposed to construct the thermal disturbance input easily.The method can be helpful for analyzing any ther-mal disturbance input satisfying the assumption and also for supplementing the correction means of performancetest.An example of 600MW power unit is presented to demonstrate its availability.     

Artificial neural network power system stabilizers in multi-machinepower system environment

The effectiveness of an artificial neural network (ANN), functioning as a power system stabilizer (PSS), in damping multi-mode oscillations in a five-machine power system environment is investigated in this paper. Accelerating power of the generating unit is used as the input to the ANN PSS. The proposed ANN PSS using a multilayer neural network with error-backpropagation training method was trained over the full working range of the generating unit with a large variety of disturbances. The ANN was trained to memorize the reverse input/output mapping of the synchronous machine. Results show that the proposed ANN PSS can provide good damping for both local and inter-area modes of oscillations     

Identification of system vulnerabilities in the Ethiopian electric power system

The Ethiopian Electric Power (EEP) has been operating and managing the national interconnected power system with dispersed and geographically isolated generators, a complex transmission system and loads. In recent years, with an increasing load demand due to rural electrification and industrialization, the Ethiopian power system has faced more frequent, widely spread and long lasting blackouts. To slash the occurrence of such incidents, identifying the system vulnerabilities is the first step in this direction. In this paper, the vulnerability assessment is performed using indices called active power performance index (PI_p) and voltage performance index (PI_v). These indices provide a direct means of comparing the relative severity of the different line outages on the system loads and voltage profiles. Accordingly, it is found that the most severe line outages are those lines that interconnect the high load centered (Addis Ababa and Central regions) with the rest of the regional power systems. In addition, the most vulnerable buses of the network in respect of voltage limit violations are mainly found at the high load centers.     

轮乘制下机车段修制度改革的探讨

通过对机车轮乘制下新的检修形势的分析,提出了确立以机车检查为主、修理为辅,检、修分离,检查范围模块化等建议;只有将机车检查从检修中分离和独立出来,才能真正保证轮乘机制下的机车质量.     

中央太阳能热水系统供水价格体系初探

一中央太阳能热水系统供水价格问题的提出 近年来，太阳能与建筑一体化的迅速兴起正顺应社会发展的潮流，让太阳能普及到千家万户。太阳能与建筑一体化的结合，除需要考虑建筑如何有机地与太阳能结合外，太阳能热水供应系统的选取也是非常关键的，中央太阳能热水系统是常用的系统之一，一直广泛应用在宾馆、学校和部队。随着太阳能与建筑一体化的推广与普及，这种系统更具广阔的应用前景。     

Catalytic combustion and system performance assessment of MCFC-MGT hybrid system

The catalytic combustor is applied as an off-gas and startup combustor for a molten carbonate fuel cell-micro-gas turbine (MCFC-MGT) hybrid system (HS) so as to utilize the waste energy of fuel cell off-gas. Three types of catalysts are prepared over a cordieritic honeycomb support. One is Pt catalyst which is not cost effective and less high temperature stability. CeZrO₂ and LaMnO₃ have been selected as an additive for another two Pt catalysts to improve the performance. Tests have been completed in realistic conditions and reaction feed close to the MCFC-MGT hybrid system. Simulations are carried out with a fluid mechanical code that incorporates detailed transport and heat loss mechanisms. The simulation results are compared with the Pt catalyst test results. The agreement confirms the accuracy of simulation. The model can be used to develop an MCFC-MGT hybrid system with an off-the-shelf gas turbine and assess the performances during part-load operation. From the experimental results, the reaction starts at 620 K for 1 vol.% CH₄ using Pt catalyst, while the temperature is above 800 K for the addition of additive. For the 50% CH₄ conversion, the preheated temperature of the three catalysts is 713 K, 870 K and 950 K respectively. While all of the catalysts exhibit good performance when using the MCFC off-gas as fuel. The results of performance analysis for part-load conditions show that the cell operation temperature and turbine inlet temperature (TIT) should be maintained as close as possible to the design value to prevent the performance degradation.     

Experimental verification of fuzzy excitation control system formulti-machine power system

A fuzzy excitation control system (FECS), based on the fuzzy theorem and having the function of both AVR and PSS, was established to improve power system stability. This paper includes the results of experiments of the FECS on the AC/DC power system simulator of the CRIEPI. The FECS is compared with the conventional quick-response excitation system with optimized PSSs on a 4-machine long distance fish-bone type power system and various system configurations. The results show that the FECS increases the power transfer limit more than 20 (%) without any parameter tuning     

反馈系统在池炉燃气热值调节中的应用研究

为了提高超白玻璃的生产质量并降低能耗,要求对玻璃炉窑燃用的天然气的热值进行精确控制。利用对空气流加热的方法在线测量燃气的热值,通过给燃气加入空气调整燃气热值,设计了燃气热值反馈调节系统。系统采用前馈和双闭环的调整方法,有效地保障了池炉燃气供应系统良好的热值调节质量。试验表明:反馈控制系统控制精度为1.0%,重复性为0.3%,响应时间为6 s,采用热值反馈系统后燃气热值波动范围由原来的40.9~42.8MJ/m3减小为34.5~34.7MJ/m3,满足了玻璃熔化质量的要求,提高了窑炉燃烧效率。     

Motor-pump system modelization

This paper presents two mathematical motor-pump models for photovoltaic (PV) applications. These models will allow us to obtain the operating point with the PV array and the flow rate of the pumped water. The modelled motor-pump characteristics are current–voltage and flow–voltage. The models are established for centrifugal and positive displacement pumps coupled to DC motors. The experimental data is obtained in our pumping test facility. A simplified method is proposed to obtain the parameters of these models in order to reduce the number of experimental measurements to the minimum.     

Photovoltaic system testing

Methodologies use to measure the field performance of photovoltaic modules and array are presented herein. Uncertainties related to the measurement of solar irradiance are discussed and techniques to reduce these uncertainties are presented. Measurement techniques for short-circuit current, open-circuit voltage, and peak-power are reviewed, as well as methods for translating data at actual test conditions to “standard test conditions”.     

风-光互补发电系统

在目前利用的诸多新能源中,太阳能与风能处于特别引人注目的地位。在我国很多地区（约占全国面积的２/３）,太阳能与风能具有一定的互补特性,即两者在上下两个半年中在变化趋势上呈现完全相反的特性,这种特性为太阳能与风能的互补（联合）发电提供了可能,与风力发电机或太阳光伏电池单独发电系统相比,互补发电系统的供电质量有较大提高,而系统的重复投资则有所下降。一风光互补发电系统风能与太阳能的随机性强,随季节、时间、天气等条件的变化差异很大。为保证供电质量,在单独发电或互补（联合）发电系统中都必须配备储能环节。构成储能环节…     

Power system optimization

Long-term gas purchase contracts usually determine delivery and payment for gas on the regular hourly basis, independently of demand side consumption. In order to use fuel gas in an economically viable way, optimization of gas distribution for covering consumption must be introduced. In this paper, a mathematical model of the electric utility system which is used for optimization of gas distribution over electric generators is presented. The utility system comprises installed capacity of 1500 MW of thermal power plants, 400 MW of combined heat and power plants, 330 MW of a nuclear power plant and 1600 MW of hydro power plants. Based on known demand curve the optimization model selects plants according to the prescribed criteria. Firstly it engages run-of-river hydro plants, then the public cogeneration plants, the nuclear plant and thermal power plants. Storage hydro plants are used for covering peak load consumption. In case of shortage of installed capacity, the cross-border purchase is allowed. Usage of dual fuel equipment (gas–oil), which is available in some thermal plants, is also controlled by the optimization procedure. It is shown that by using such a model it is possible to properly plan the amount of fuel gas which will be contracted. The contracted amount can easily be distributed over generators efficiently and without losses (no breaks in delivery). The model helps in optimizing of fuel gas–oil ratio for plants with combined burners and enables planning of power plants overhauls over a year in a viable and efficient way.     

Three-layer electrochromic system

The electrochromic effect may be observed by employing a single mixed conducting layer in-between two transparent electronically conducting leads. Besides the simplicity of the design, the advantage is the displacement of ions only within a single phase rather than across phase boundaries. The applied voltage controls the compositions at the two interfaces according to Nernst's law independent of majority or minority ionic conduction. Appropriate materials are commonly intrinsic conductors in the unpolarized transparent state and become n-type and p-type conducting at the negative and positive electrode, respectively. Several examples have been studied, such as lithiated tungsten oxide and lithium and tantalum co-doped tungsten oxide.