Application of energy capacitor system to wind power generation

In this paper, it is reported that energy capacitor system (ECS), which combines power electronic devices and electric double‐layer capacitor, can significantly decrease voltage and power fluctuations of grid‐connected fixed‐speed wind generator. The proper selection of wind farm output power reference is still a problem for smoothing the wind farm output power. This paper proposes exponential moving average to generate the reference output power of a grid‐connected wind farm. The objective of the control system is to follow the line power reference by absorbing or providing real power to or from the ECS. Moreover, the necessary reactive power can also be supplied to keep the wind farm terminal voltage at the desired reference level. Real wind speed data were used in the simulation analyses, which validate the effectiveness of the proposed control strategy. Simulation results clearly show that our proposed ECS can be suitable for wind power application. Copyright © 2007 John Wiley & Sons, Ltd.     

碟式太阳能发电在分布式能源系统中的应用

碟式太阳能发电系统具有单机容量小,排布灵活,余热可综合利用等特点,是一种较适合与分布式能源系统结合的太阳能利用类型。对碟式太阳能发电技术进行逐一分析,总结了在分布式能源站中应用碟式太阳能所面临的诸多问题。结合实例,详细介绍华电电力科学研究院有限公司一套25 kW的碟式太阳能发电系统运行情况,提出系统的改进和提升方向。     

风光互补独立供电系统优化匹配设计实例

以系统的最小安装成本为优化目标,以系统的供电可靠性为约束条件,对内蒙古满洲里市某居民家庭用电风光互补独立供电系统进行基于计算机仿真计算的优化匹配设计。     

新型户用风光互补供电系统

简要描述了新型户用风光互补供电系统及其应用示范情况,以一个典型的实例分析了系统运行情况。经过1年的运行证明,该系统设计合理,能够满足边远地区目前的用电需求,具有推广应用价值。     

Complimentary nature of wind and solar energy at a continental mid-latitude station

Daily values of solar and wind energy have been used (i) to study renewable energy availability at various times of year, (ii) to test the level of persistence for inferences about the practicality of energy storage and (iii) to examine the complementary behaviour of these two daily time series on both seasonal and daily bases. Results for the station studied (central Iowa) show a bimodal distribution for winter solar energy, whereas non-winter solar and wind (all seasons) show unimodal distributions. Wind and solar energy were observed to be highly complementary on an annual basis, but only slightly complementary on a daily basis.     

An application of a combined wind and solar energy system in Izmir

In this work, a combined system which is produced electrical energy from both solar radiation via solar cells and wind energy by using wind turbine was studied. For wind energy, measurements of wind velocities at 12 m height were taken. Then, these values were calculated for 42 m by using Hellmann equation. After that, wind energy converted to the electrical energy. However, value of solar radiation from solar cells was taken at the optimum slope angle of collector which provided higher energy production for each 1 h during this application. Thus, obtained data from each system were used together for finding total energy. For this study, measurements, which would be used in calculation of wind energy and solar energy were taken for four years between 1995 and 1998 in Izmir. As a result, energy of the combined system could support each other when one of them produces energy insufficiently.     

Probabilistic modelling of hybrid solar/wind power system with solar tracking system

This paper presents a probabilistic model applied to a hybrid solar-wind power system (HSWPS), which is equipped with either a one-axis or a two-axis solar tracking system.Within the framework of a case study, the potential of the developed probabilistic approach is presented, and the effect of the solar tracking systems on the annual energy gain is discussed.Specifically, the impact of a tracking system on the probability density function (PDF) of the power produced by a photovoltaic system (PVS) is evaluated through the first four moments (mean, variance, skewness and kurtosis) of a PDF.Finally, to estimate the impact of a tracking system on HSWPS energy performance, a reliability analysis is performed using the energy index of reliability (EIR), which is directly related to energy expected not supplied (EENS), given different annual load scenarios.     

Dynamic model of wind energy conversion systems with PMSG-based variable-speed wind turbines for power system studies

In order to study the impact of a wind farm on the dynamics of the power system, a significant issue is to develop appropriate equivalent models that allow characterizing the dynamics of all individual wind turbine generators (WTGs) composing the park. In this sense, with the advance of power electronics, direct-driven permanent magnet synchronous generators (PMSGs) have drawn increased interest to wind turbine manufacturers due to their advantages over other variable-speed WTGs. These include the possibility of multi-pole design with a gearless construction that offers slow speed operation and reduced maintenance since no brushes are used, elimination of the excitation system, full controllability for maximum wind power extraction and grid interface, and easiness in accomplishing fault-ride through and grid support. In this way, this paper presents a comprehensive dynamic equivalent model of a wind farm with direct-driven PMSG wind turbines using full-scale converters and its control scheme. The proposed simplified modelling is developed using the state-space averaging technique and is implemented in the MATLAB/Simulink environment. The dynamic performance of the wind farm and its impact on the power system operation is evaluated using the phasor simulation method.     

Utilizing wind and solar energy as power sources for a hybrid building ventilation device

Wind and solar energy are currently used to power many building ventilation devices. Such devices rely exclusively on either solar or wind energy, which limits their usefulness. A low-cost hybrid ventilation device that utilizes both wind and solar energy as power sources was designed to overcome some of the shortcomings of these devices. Wind tunnel testing conducted at the aerodynamics laboratory of the University of New South Wales revealed that the hybrid device had improved operational and performance benefits compared with conventional commercial roof top ventilators, particularly at zero to low wind speeds. This represents a significant step forward and will have an immediate impact in promoting the use of clean energy for the purposes of building ventilation.     

Probabilistic model of a two-site wind energy conversion system

A general probabilistic model of a two-site wind-energy conversion system (WECS) is described in this paper. The wind speeds at the two sites are not assumed to be independent, which prevents the convolution theorem from being directly applicable. Instead, a model based on the conditional probability theorem and mutually exclusive events is presented. The model supports the assessment of the energy resource available to supply a given load represented by its load duration curve, taking into consideration wind-turbine failure modes and the intermittent nature of the wind resource. The model is based on a capacity-probability table constructed using fundamental probability theorems on conditional and mutually exclusive events. The table is then combined with a load model in order to assess its performance and determine the expected energy not supplied (EENS) of the system. A planning study is then reported on a realistic system to illustrate how the most efficient wind turbines can be selected to support an existing thermal system using a procedure based on a minimization of the incremental marginal cost of operation.     

Using hydropower to complement wind energy: a hybrid system to provide firm power

This paper presents a theoretical study of how wind power can be complemented by hydropower. A conceptual framework is provided for a hybrid power station that produces constant power output without the intermittent fluctuations inherent when using wind power. Two hypothetical facilities are considered as case studies. One of them is a hydropower plant located on the “Presidente Benito Juarez” dam in Jalapa del Marques, Oaxaca, Mexico. The other hypothetical facility is a wind farm located near “La Venta”, an area in Juchitan, Oaxaca, Mexico. The wind–hydro-power system is a combined wind and hydro power plant in a region that is rich in both resources. The model shows that the hybrid plant could provide close to 20 MW of firm power to the electrical distribution system. On a techno-economic basis, we obtain the levelized production cost of the hybrid system. Taking into account two different discount rates of 7% and 10%, figures for levelized production cost are developed.     

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies.At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.     

A multi‐predictor model to estimate solar and wind energy generations

Recent technological developments in renewable energy systems and significant growth of solar and wind energy have made these 2 renewable sources potential viable alternatives for conventional energy sources. However, due to intermittent nature, their reliability and availability are not similar to traditional sources. Hence, it is crucial to estimate the solar and wind availability and contribution more accurately. There are various factors affecting the generation capacity of renewable sources. There has been a vast research on the impact of factors related to climate condition such as wind speed, air temperature, and humidity on renewable energy generation. However, there are several other factors with indirect impact on renewable capacity and generation mostly overshadowed by the climate factors. In this study, a multi‐predictor regression model is developed and presented for solar and wind energy generation capacity across the USA. Our study of 50 states shows how the generation capacity can be affected by several indexes including human development index. Variables with the more significant impacts have been chosen using a regression analysis. A recommendation on the best transformation of the response variables and sensitivity analysis of the results has also been presented. The results provide a model to estimate the generation capacity using significant predictors. For instance, the impact of population growth on the wind turbine generation can be explored using these models.     

Technology mix alternatives with high shares of wind power and photovoltaics—case study for Spain

The shift to a low carbon society is an issue of highest priority in the EU. For electricity generation, such a target counts with three main alternatives: renewable energies, nuclear power and carbon capture and storage. This paper focuses on the renewables’ alternative. Due to resource availability, a technology mix with a high share of PV and wind power is gaining increasing interest as a major solution for several EU member states and in part for the EU collectively to achieve decarbonization and energy security with acceptable costs. Due to their intermittency, the integration of high shares of PV and wind power in the electricity supply is challenging. This paper presents a techno-economic assessment of technology mix alternatives with a high share of PV and wind power in Spain, as an example. Thereby, the focus is on the option of increasing wind curtailment versus substituting rigid baseload generation in favor of the more flexible gas turbines and combined cycle gas turbines.     

太阳能与风能发电在通信电源系统中的综合应用

介绍了太阳能发电与风力发电相结合在边远通信基站电源系统中的应用设计,针对通信系统的电源特点和要求,引入了主备控制方式的太阳能充电控制技术以及常规的高频整流方式的风能充电控制技术,两种发电方式组成的互为补充的供电方式,可大大降低单纯采用太阳能供电的电源系统成本,并进一步提高系统供电的安全性.     

Optimization of a combined wind and solar power plant

The paper is concerned with determining the optimized active areas of a photovoltaic conversion system, of a group of electricity generating wind machines and the optimal capacity of a battery storage system for a combined power plant. Minimization of the total life-cycle cost of the system is the criterion to obtaining the optimized parameters of the system. The algorithm consists of generating the system costs corresponding to various values of the parameters and to use these costs in a search procedure to determine the minimum. Each point is generated by a simulation program describing the system behaviour.     

Simulation of a combined wind and solar power plant

The combined generation of electricity by wind and solar energy is a very attractive solution for isolated regions with high levels of yearly wind energy and insolation. A computer model is developed for the simulation of the electricity system of a Mediterranean island, including a wind power plant, a photovoltaic power plant and a storage system. In order to obtain an overall view of the system performance and economic aspects, the model also incorporates a number of diesel generators. Daily simulations for the Greek island Kythnos show that such a combined system of moderate size can provide a large fraction of the electrical energy requirements. Various parameters calculated in the simulation can be used to improve the configuration of the system and to estimate the cost of the electrical energy unit.     

Maximum power point tracker of wind energy conversion system

In this paper, a simple control strategy for an optimal extraction of output power from grid connected variable speed wind energy conversion system (WECS) is presented. The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator (PMSG) through a gear box, a diode bridge rectifier, a dc-to-dc boost converter and a current controlled voltage source inverter. The maximum power point tracker (MPPT) extracts maximum power from the wind turbine from cut-in to rated wind velocity by sensing only dc link power. The MPPT step and search algorithm in addition to the DC–DC and DC–AC converters PWM controllers are simulated using MATLAB-SIMULINK software. The obtained simulation results show that the objectives of extracting maximum power from the wind and delivering it correctly to the grid are reached.     

Probabilistic analysis of weather data for a hybrid solar/wind energy system

In this paper, a procedure for the probabilistic treatment of solar irradiance and wind speed data is reported as a method of evaluating, at a given site, the electric energy generated by both a photovoltaic system and a wind system. The aim of the proposed approach is twofold: first, to check if the real probability distribution functions (PDFs) of both clearness index and wind speed overlap with Hollands and Huget and Weibull PDFs, respectively; and then to find the parameters of these two distributions that best fit the real data. Further, using goodness‐of‐fit tests, these PDFs are compared with another set of very common PDFs, namely the Gordon and Reddy and Lognormal functions, respectively. The results inform the design of a pre‐processing stage for the input of an algorithm that probabilistically optimizes the design of hybrid solar wind power systems. In this paper, the validity of the proposed procedure was tested using long‐term meteorological data from Acireale (Italy). Copyright © 2010 John Wiley & Sons, Ltd.     

A demonstrative study for the wind and solar hybrid power system

In March 1995, a small scale wind and solar hybrid power system was installed at Ashikaga Institute of Technology. Until now, the authors have acquired the data of the output of the hybrid power plant along with wind speed, wind direction, and the solar radiation, in order to demonstrate a complementary relationship between solar energy and wind energy.After nine months operation of the system, the authors confirmed that there exists a complementary relationship between solar energy and wind energy. We also found, however, that the power output by wind does not have much prospect compared to that by solar cell especially in summer season in Ashikaga area.