Power characteristics of a fuel cell micro‐grid with wind power generation

An independent micro‐grid connected with renewable energy has the potential to reduce energy costs, and reduce the amount of greenhouse gas discharge. However, the frequency and voltage of a micro‐grid may not be stable over a long time due to the input of unstable renewable energy, and changes in short‐period power load that are difficult to predict. Thus, when planning the installation of a micro‐grid, it is necessary to investigate the dynamic characteristics of the power. About the micro‐grid composed from 10 houses, a 2.5 kW proton exchange membrane fuel cell is installed in one building, and it is assumed that this fuel cell operated corresponding to a base load. A 1 kW PEM‐FC is installed in other seven houses, in addition a 1.5 kW wind turbine generator is installed. The micro‐grid to investigate connects these generating equipments, and supplies the power to each house. The dynamic characteristics of this micro‐grid were investigated in numerical analysis, and the cost of fuel consumption and efficiency was also calculated. Moreover, the stabilization time of the micro‐grid and its dynamic characteristics accompanied by wind‐power generation and fluctuation of the power load were studied. Copyright © 2007 John Wiley & Sons, Ltd.     

微网中光伏发电系统的储能控制研究

利用可再生能源（如太阳能和风能）的分布式发电,其输出是典型的不稳定,这些不稳定的输出对现有的电力系统产生负面影响。为了减少负面影响,需要控制在微网中的各个分布式电源的输出。设计了一种基于蓄电池储能的并网光伏发电系统结构,结合功率流动的控制策略介绍了各部分的运行原理,对系统能流模型进行了详细分析,根据电池的特性设计了充放电的控制策略。在PSCAD平台下对设计的模型进行仿真,通过在不同能流模型下控制策略仿真分析,验证所提出储能方案的正确合理性,对功率平衡起到很好的调节作用。     

A hybrid power system using alternative energy facilities in isolated island

A hybrid power system uses many wind turbine generators in isolated small islands. The output power of wind turbine generators is mostly fluctuating and has an effect on system frequency. In order to solve this problem, we propose a new power system using renewable energy in small, isolated islands. The system can supply high-quality power using an aqua electrolyzer, fuel cell, renewable energy, and diesel generator. The generated hydrogen by an aqua electrolyzer is used as fuel for a fuel cell. The simulation results are given to demonstrate the availability of the proposed system in this paper.     

Frequency deviation control by coordination control of FC and double-layer capacitor in an autonomous hybrid renewable energy power generation system

In this paper, a novel control strategy for frequency control in stand-alone application based on coordination control of fuel cells (FCs) and double-layer capacitor (DLC) bank in an autonomous hybrid renewable energy power generation system is implemented. The proposed renewable energy power generation subsystems include wind turbine generator (WTG), photovoltaic system (PV), FC system and DLC bank as energy storage system. The system performance under different condition has been verified by using real weather data. Simulation results demonstrate the validity of proposed studied hybrid power generation system feeding isolated loads in power frequency balance condition.     

Load response characteristics of a fuel cell micro-grid with control of number of units

The dynamic characteristics and generation efficiency of a micro-grid structured from 17 houses were examined. A gas engine generator with a power generation capacity of 3 kW installed in a house is made to correspond to the base load, and a solid-polymer-membrane-type fuel cell with a power generation capacity of 1 kW is installed in 16 houses. Moreover, when changing the load of a micro-grid, the correspondence takes place by controlling the number of fuel cells. Using numerical analysis, the characteristics of the power quality of a fuel cell micro-grid, and the generation efficiency of the fuel cell were examined. As a result, the relationship between the parameter of the controller and power quality and a fall in generation efficiency by a partial load was clarified.     

Techno-economic analysis of hydrogen energy for renewable energy power smoothing

With the increasing proportion of renewable energy (mainly wind power and photovoltaic) connected to the grid, the fluctuation of renewable energy power brings great challenges to the safe and reliable operation of power grid. As a clean, low-carbon secondary energy, hydrogen energy is applied in renewable energy (mainly wind power and photovoltaic) grid-connected power smoothing, which opens up a new way of coupling hydrogen storage energy with renewable energy. This paper focuses on the optimization of capacity of electrolyzers and fuel cells and the analysis of system economy in the process of power output smoothing of wind/photovoltaic coupled hydrogen energy grid-connected system. Based on the complementary characteristics of particle swarm optimization (PSO) and chemical reaction optimization algorithm (CROA), a particle swarm optimization-chemical reaction optimization algorithm (PSO-CROA) are proposed. Aiming at maximizing system profit, the capacity of electrolyzers and fuel cells are constrained by wind power fluctuation, and considering environmental benefits, government subsidies and time value of funds, the objective function and its constraints are established. According to the simulation analysis, by comparing the calculated results with PSO and CROA, it shows that PSO-CROA effectively evaluates the economy of the system, and optimizes the optimal capacity of the electrolyzers and fuel cells. The conclusion of this paper is of great significance for the application of hydrogen energy storage in the evaluation of power smoothness and economy of renewable energy grid connection and the calculation of economic allocation of hydrogen energy storage capacity.     

The spectrum of power from wind turbines

The power spectral density of the output of wind turbines provides information on the character of fluctuations in turbine output. Here both 1-second and 1-hour samples are used to estimate the power spectrum of several wind farms. The measured output power is found to follow a Kolmogorov spectrum over more than four orders of magnitude, from 30 s to 2.6 days. This result is in sharp contrast to the only previous study covering long time periods, published 50 years ago. The spectrum defines the character of fill-in power that must be provided to compensate for wind's fluctuations when wind is deployed at large scale. Installing enough linear ramp rate generation (such as a gas generator) to fill in fast fluctuations with amplitudes of 1% of the maximum fluctuation would oversize the fill-in generation capacity by a factor of two for slower fluctuations, greatly increasing capital costs. A wind system that incorporates batteries, fuel cells, supercapacitors, or other fast-ramp-rate energy storage systems would match fluctuations much better, and can provide an economic route for deployment of energy storage systems when renewable portfolio standards require large amounts of intermittent renewable generating sources.     

网外与网内2种微电网供电方式的协调

微电网供电方式可分为网外与网内2类,前者为大电网参与微电网供电,后者为利用微电网内部各类发电方式进行供电,包括利用风力发电、光伏发电等可再生分布式发电,投入燃料电池、微型燃气轮机等不可再生分布式发电以及中断可中断负荷。为提高微电网供电经济性,充分利用这2种供电方式之间的经济互补特性,基于协调优化理论,建立协调这2种供电方式的数学模型,并基于代价对参数的灵敏度来指导优化方向的寻优算法对该模型进行求解,量化微电网各类供电方案的经济性,分析各因素对供电方案的影响。仿真结果表明,这2种供电方式之间存在协调空间,且协调要比不协调更能够提高微电网供电经济性。     

基于超级电容储能的风电并网功率调节控制系统

风能是一种随机变化的能源,风速变化会导致风电机组输出功率的波动,对电网的电能质量产生影响,使用储能装置可以改善风电质量。通过在风电场并网的交流侧母线上并联超级电容储能单元,能实现对风电场功率的调节,减小功率的波动。文章设计了风电场并网及储能系统各部分的控制策略,在Matlab/Simulink仿真环境下创建了系统的仿真模型,验证了控制策略的正确性。仿真系统最终实现了电机侧变流器最大风能跟踪、电网侧变流器单位功率因数并网和超级电容储能单元对风电场并网功率的调节。     

Analytical model for predicting the performance of photovoltaic array coupled with a wind turbine in a stand-alone renewable energy system based on hydrogen

We present the results of an analysis of the performance of a photovoltaic array that complement the power output of a wind turbine generator in a stand-alone renewable energy system based on hydrogen production for long-term energy storage. The procedure for estimating hourly solar radiation, for a clear sunny day, from the daily average solar insolation is also given. The photovoltaic array power output and its effective contribution to the load as well as to the energy storage have been determined by using the solar radiation usability concept. The excess and deficit of electrical energy produced from the renewable energy sources, with respect to the load, govern the effective energy management of the system and dictate the operation of an electrolyser and a fuel cell generator. This performance analysis is necessary to determine the effective contribution from the photovoltaic array and the wind turbine generator and their contribution to the load as well as for energy storage.     

基于Matlab的微电网孤岛运行仿真研究

微电网技术是21世纪电网发展的一个重要方向.这种全新的供配电形式,不仅更适合于新能源接入,而且人性化地赋予了电力用户更多的选择和管理空间.利用Matlab/Simulink软件模拟搭建了一个由风能和水能提供电源的微电网仿真平台,并对平台在遇到主网故障时的两种运行模式(关闭/开启孤岛运行)进行了仿真.结果表明,关闭孤岛运行模式时,微电网将在大电网故障时承受长时间及大幅值的功率与电压波动;开启孤岛运行模式时,微电网的功率与电压波动将有所减弱,能较好保证微电网的供电稳定和设备安全.研究表明,微电网的孤岛运行机制是有效且必要的.     

Optimal scheduling of a renewable micro-grid in an isolated load area using mixed-integer linear programming

In the energy management of the isolated operation of small power system, the economic scheduling of the generation units is a crucial problem. Applying right timing can maximize the performance of the supply. The optimal operation of a wind turbine, a solar unit, a fuel cell and a storage battery is searched by a mixed-integer linear programming implemented in General Algebraic Modeling Systems (GAMS). A Virtual Power Producer (VPP) can optimal operate the generation units, assured the good functioning of equipment, including the maintenance, operation cost and the generation measurement and control. A central control at system allows a VPP to manage the optimal generation and their load control. The application of methodology to a real case study in Budapest Tech, demonstrates the effectiveness of this method to solve the optimal isolated dispatch of the DC micro-grid renewable energy park. The problem has been converged in 0.09 s and 30 iterations.     

风光联合发电系统的储能容量优化配置方法

随着可再生能源大规模接入电网,风力发电和光伏发电的不稳定性威胁着电网的安全稳定运行。储能系统作为一种可调度的能源,可实现可再生能源输出功率的平滑输出。通过分析风光联合发电系统输出功率特性,提出采用平抑指标和平滑效果评价指标对比分析滑动平均法和最小二乘法滤波效果,用于确定蓄电池储能配置的参考输出功率。在获得平滑后的功率曲线后,根据提出的曲线局部平滑指标和总体平滑指标,综合考虑蓄电池投资成本和平滑效果优化配置储能容量。最后,采用某地区实际的风光资源历史数据,验证了所提方法的可行性。     

计及环境效益的虚拟电厂经济性优化调度

虚拟电厂（Virtual power plant, VPP）能有效减小新能源对电网的冲击,提高供电可靠性。本文在分析了VPP各分布式电源（Distributed generator, DG）发电成本的基础上,构建了计及环境效益的含风力发电、光伏发电、小水电和微型燃气轮机发电的VPP经济性优化调度模型,设计了基于小水电季节特性的VPP运行策略。以各时段内VPP实际出力跟踪计划出力、同时VPP发电成本和环境成本最小为目标,通过粒子群算法计算得到VPP各DG的出力。讨论了丰水期、平水期和枯水期VPP完成计划出力时微型燃气轮机出力系数,比较了丰水期、平水期和枯水期VPP发电成本和环境成本,并基于火力发电的环境成本计算了丰水期、平水期和枯水期VPP环境效益。实验结果验证了所建模型和运行策略的合理性,并表明VPP能有效平抑新能源出力偏差,降低DG发电总成本。     

The Advanced Energy Initiative

The President's Advanced Energy Initiative (AEI), launched in 2006, addresses the challenges of energy supply and demand facing our Nation by supporting research and development of advanced technologies for transportation and stationary power generation. The AEI portfolio includes clean coal, nuclear and renewable energy technologies (solar and wind) for stationary power generation and advanced battery technologies, cellulosic ethanol as a fuel and hydrogen fuel cells for transportation. These research and development programs are underpinned by comprehensive life-cycle analysis efforts using models such as Hydrogen Analysis (H2A) and Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET) to enable a better understanding of the characteristics and trade-offs associated with advanced energy options and to help decision makers choose viable pathways for clean, reliable and affordable energy.     

Prospects of renewable energy - a feasibility study in the Australian context

Given the recent increasing public focus on climate change issues, there is a need for robust, sustainable and climate friendly power transmission and distribution systems that are intelligent, reliable, and green. Current power systems create environmental impacts as well as contributing to global warming due to their utilization of fossil fuels, especially coal, as carbon dioxide is emitted into the atmosphere. In contrast to fossil fuels, renewable energy is starting to be used as the panacea for solving climate change or global warming problems. This paper describes a feasibility study undertaken to investigate the potentialities of renewable energy including the prospective locations in Australia for renewable energy generation, in particular solar and wind energy. Initially, a hybrid model has been developed to investigate the prospects of wind energy for typical Australian region considering production cost, cost of energy, emission production and contribution from renewable energy using the Hybrid Optimization Model for Electric Renewable (HOMER), a computer model developed by the USA’s National Renewable Energy Laboratory (NREL). This model also explores suitable places around Australia for wind energy generation using statistical analysis. Subsequently, the usefulness of solar energy in the Australian context and suitable locations for solar energy generation are also investigated using a similar hybrid model. Finally, the model has been developed to investigate the prospects of renewable energy in particular wind and solar energy including specific locations in Australia that would be suitable for both wind and solar energy generation. From simulation analysis it is clearly observed that Australia has enormous potentialities for substantially increased use of renewable energy; a large penetration of renewable energy sources into the national power system would reduce CO₂ emissions significantly, contributing to the reduction of global warming.     

Equipment plan of compound interconnection micro-grid composed from diesel power plants and solid polymer membrane-type fuel cell

Although the micro-grid using a diesel power plant power generator (DEG) has a high possibility of implementation, there is a problem in the emission of carbon dioxide gas. Then, an independent micro-grid that compounds and connects a diesel power plant generator and a solid polymer membrane-type fuel cell (PEM-FC) is proposed. The operation of DEG is controlled to correspond to the base load of whole compound interconnection micro-grid (CIM), and, on the other hand, the operation of PEM-FC is controlled to follow the load fluctuation of CIM. In this paper, the generation capacity of DEG and PEM-FC installed into CIM and the grid route of PEM-FC were analyzed with the object of maximizing generation efficiency. A complex community model and residential area model were used for analysis. In this paper, the micro-grid concerning the urban area (18 buildings) in Tokyo was investigated. From the results of analysis, it was confirmed that CIM could be operated with a high generation efficiency of 27.1–29.9%.     

Micro-grid design and life-cycle assessment of a mountain hut's stand-alone energy system with hydrogen used for seasonal storage

Mountain huts, as special, stand-alone, micro-grid systems, are not connected to a power grid and represent a burden on the environment. The micro-grid has to be flexible to cover daily and seasonal fluctuations. Heat and electricity are usually generated with fossil fuels due to the simple on-off operation. By introducing renewable energy sources (RESs), the generation of energy could be more sustainable, but the generation and consumption must be balanced. The paper describes the integration of a hydrogen-storage system (HSS) and a battery-storage system (BattS) in a mountain hut. The HSS involves a proton-exchange-membrane water electrolyser (PEMWE), a hydrogen storage tank (H₂ tank), a PEM fuel cell (PEMFC) and a BattS consisting of lead-acid batteries. Eight micro-grid configurations were modelled using HOMER and evaluated from the technical, environmental and economic points of view. A life-cycle assessment analysis was made from the cradle to the gate. The micro-grid configurations with the HSS achieve, on average, a more than 70% decrease in the environmental impacts in comparison to the state of play at the beginning, but require a larger investment. Comparing the HSS with the BattS as a seasonal energy storage, the hydrogen-based technology had advantages for all of the assessed criteria.     

智能微电网技术效益分析与评估模型及应用

鉴于在技术可行的前提下实现智能微电网系统经济效益最大化是智能微电网系统建设过程中必须解决的关键问题,基于可再生能源发电技术特性,分析了智能微电网技术给电力系统和各参与主体带来的经济效益,选取了智能微电网经济效益评价指标,进而建立了强制评分—主成分分析评估模型,并通过算例分析验证了模型的可行性。     

Prioritization of potential locations for harnessing wind energy to produce hydrogen in Afghanistan

Due to the devastating ecological effects and constrained reserves of fossil fuels, renewable energies are now globally accepted as viable alternative sources of energy. Among renewable energy sources, wind energy has become globally popular, primarily because wind farms can be rapidly built and easily maintained at a relatively low cost. Wind-powered hydrogen production is an effective solution for storing the excess energy output of wind farms. The hydrogen produced in this way can be used not only in fuel cells but also in cooling, oil, gas, and petrochemical fields. As a country devastated by war and instability, Afghanistan has major energy generation challenges and a substantially large power supply deficiency. However, there are good wind energy potentials in several parts of this country. There are also several hydrogen-consuming fields in Afghanistan that can benefit from hydrogen production from wind energy. This paper endeavored to distinguish the appropriate areas in Afghanistan for harvesting wind energy for hydrogen production using multi-criteria decision-making techniques. Eleven criteria were utilized to prioritize 20 Afghan provinces with wind energy potential. The Step-wise Weight Assessment Ratio Analysis (SWARA) was utilized to weight the criteria and Evaluation based on Distance from Average Solution (EDAS) were utilized to prioritize the provinces. Then, ARAS, TOPSIS, and VIKOR methods were used to validate the resultants. For criteria weighting with SWARA, “wind speed”, “wind power density” and “area of windy regions” with weights of 0.1423, 0.1356, and 0.1221 were introduced as the most significant criteria for this ranking. In all the rankings, Herat, Farah, and Jowzjan were identified as the top three most suitable provinces for wind power generation. The power output and hydrogen output to be achieved in Herat province using a 900-kW turbine were estimated to 2558.4 MW per year and 41.4 tons per year, respectively.