Power flow control model of energy storage connected to smart grid in unbalanced conditions: a GSA-technique-based assessment

A gravitational search algorithm (GSA)-based power flow control (PFC) model for energy storage related to smart grid under unbalance conditions is proposed in this paper. Source side and load side power transfer capability is considered to be increased by this proposed algorithm and it offers several conveniences such as the improved predicting capability, degradation in complexity as well as the randomization and so on. The smart grid incorporates the combination of the microgrid (MG) such as renewable energy sources, energy storage devices, grid and load. Here, a renewable energy source of the photovoltaic (PV) system and energy storage of fuel cell (FC) is considered and AC load is utilized. In the proposed method, the controller parameters of the power controller are optimized by the GSA technique based on the variation of active and reactive power of the system. The better power flow under unbalanced load conditions with subject to the minimum power variation is ensured by the optimization process. The proper control signals to the voltage source inverter (VSI) system are generated by this proposed method. Then, the proposed method is implemented using the MATLAB/Simulink platform and a comparison analysis with the existing techniques presents the performance of the proposed method.     

凝聚智慧,着眼未来 本期话题:使用率得分与成本对比

2011年新春伊始,全国建筑业企业特级资质信息化标准与实施办法已颁布,这对于期待应对特级资质考评,提升企业管理能力与综合竞争力的建筑业企业来说,是一件大事。《联盟论坛》栏目在新的一年,将继续跟踪IT实践者的讨论话题与内容,从中凝练出具有代表性的思想与观点,记录建筑业企业信息化前进的脚步。     

Analysis of a combined photovoltaic–geothermal gas-fired absorption heat pump system in a Canadian climate

This study examines the technical feasibility of using a geothermal gas-fired absorption heat pump (A-GSHP) for space conditioning and domestic hot water heating in a Canadian climate. The A-GSHP is coupled to a photovoltaic (PV) system with battery storage intended to ensure the full autonomy of the heating, ventilating and air conditioning (HVAC) system from the electric grid. The system is modelled using TRNSYS with standard models and a new performance-based A-GSHP model, which accounts for part-load operation. Results indicate that the coefficient of performance (COP) is equal to 1.12, 0.55 and 1.79 for heating only, cooling only and simultaneous cooling and domestic hot water (DHW) heating, respectively. A 13.5 kWp PV array and a 400 kWh battery storage are necessary to provide the electrical power required to operate the A-GSHP and the associated HVAC system at all times without importing electrical energy from the grid.     

The feasibility of new design of hybrid photovoltaic-thermal system – a theoretical approach

Hybrid photovoltaic thermal (PVT) collectors have been evaluated according to the physical features of commercial photovoltaic (PV) cells; therefore, their commercial application is limited. The Tedlar collector has good electrical insulating properties, resulting in reduction in electrical efficiency. A researcher found that a glazed PVT system without Tedlar was the best among others, showing a significant increase in the overall efficiency. Inspired by this finding, we thought to study, for the first time, the feasibility of a new PVT that has been built by modifying a commercial PV panel and retrofitting it with the integration of two tubes in glass above the PV cell pasted on a thin metal ribbon before PV encapsulation. A heat transfer modelling/simulation in 3D was performed using COMSOL Multiphysics software.

The results show that under the no-cooling situation, the PV cell temperature reaches 74.87°C and the electrical power dropped significantly to 0.113 for electrical efficiency of 0.15 at the reference conditions. The water flow velocity is determined so that the cell can be effectively cooled. The cell temperature variation reaches to 45.9°C for a flow velocity of 0.5m/s, an irradiation of 1000W/m² and ambient temperature equal to 20.15°C.     

The potential of a small hydro/photovoltaic hybrid system for electricity generation in FUTO,Nigeria

An evaluation of the potential of a small hydro/PV (SHPV) hybrid system for electricity generation in FUTO, Nigeria is presented. Major components of the hydro and PV systems were considered. The study area electricity load demand for a 10-year period, available hydrological data of the Otamiri River and a 12-year solar radiation data of the study area were used in the study. The obtained results show that at a net head of 3 m, the maximum available hydropower was determined during October as 174.70 kW while the Kaplan turbine with a runner diameter not less than 4.67 m was found to be the most suitable. For the photovoltaic (PV) system, the maximum area, the number of PV modules and the battery bank capacity were determined as 3248 m², 3025 and 98,521,098 Ah, respectively. Thus, a SHPV hybrid system is a viable source of power generation for the study area.     

杭州科技馆光伏屋面一体化设计与研究

介绍了杭州科技馆光伏屋面一体化的主要设计内容。将屋面光伏系统目标容量定为100kW,选用180W的嵌入模块式光伏组件,介绍了组件布置方式,并通过试验测试了组件力学性能、发电效率、水密性等;阐述了支架布置和连接方式,并建模分析了其在荷载工况作用下的杆件内力和变形情况;对光伏系统的逆变器配置、光伏阵列设计、光伏汇流设计和相关配电设备配置等内容进行了简要论述,建立了一套完整的用户侧低压并网系统。     

Advanced sliding mode control for solar PV array with fast voltage tracking for MPP algorithm

ABSTRACT

This paper presents a photovoltaic (PV) system with a maximum power point tracking (MPPT) method. The main aim of this work is to collect the maximum power generated from a solar photovoltaic generator (PVG). This goal is accomplished by integrating a sliding mode controller (SMC) that drives a voltage source inverter (VSI) connected between the PVG and the load. The system is modelled and tested in MATLAB/SIMULINK. In simulation, the SMC gives a fast and accurate convergence to the MPP that is tracked by incremental conductance (INC) type MPPT algorithm. The consequence of the system is capable of tracking MPPs accurately and rapidly without steady-state oscillation and also its performance is satisfactory. The INC type MPPT algorithm is used to track MPPs because it exhibits a precise control under rapidly changing atmospheric conditions. As the solar energy gives the variable light energy at different times and is not constant, the SMC performance is calculated at variable irradiation points by using one slider gain for the variation of the insolation levels.     

分布式光伏并网系统运行中存在的问题

光伏建筑一体化作为分布式光伏电站的一种存在形式,越来越受到关注。分布式光伏系统接入配电网运营后,改变了传统电网的结构,从过去的无源电网转变为有源电网。由于光伏发电系统输出的电能具有间歇性、不稳定性等特点,必然会对所接入配电网的电能质量、潮流分布、短路电流、保护协调、孤岛效应、光伏逆流等方面产生不同程度的影响。根据国家电网公司颁布的《分布式电源接入系统典型设计》的要求,针对分布式光伏并网系统运行中存在的问题,提出了改进措施和具体的技术要求。     

Z源逆变器光伏发电系统变量调制范围随动的两级控制研究

Z源逆变器光伏发电系统是一种具有升/降压功能的单级系统,可以通过调节直通占空比实现前级光伏电池的最大功率跟踪(MPPT)控制,然后由逆变器调制因子m实现并网控制.提出了一种直通占空比调制范围上限随动的两级控制策略.该策略兼顾了两级控制和单级控制的优点:充分利用了直通零矢量,使逆变器的调制因子m增大,直流电压利用率高,相应的有源器件的电压应力和逆变器输出电流谐波得到很大地改善;消除了光伏电池和电网之间的影响.仿真和实验结果验证了理论分析的正确性与实用性.     

上海地区独立住宅分布式光伏发电系统的后评估研究

基于上海一独立住宅光伏发电系统运行一年的数据,从发电量、光伏系统效率、光伏能源替代率、光伏系统效率影响因素等方面进行后评估。结果表明:过去一年度理论预测年发电量为5 738 k W·h,实际发电量为4 109 k W·h,全年度光伏系统效率为73%。为研究光伏系统效率的影响因子,在系统运行期间未对光伏组件表面实施人工清洁维护,对此条件下的运行数据进行分析发现,光伏系统效率总体呈现逐渐降低的趋势。其中在近水平安装角度的情况下,组件光电转换效率最大降低达2.08%。在该住宅按照现行理想的设计条件运行(冬季连续采暖确保室内20℃、夏季连续空调确保室内26℃)的前提下,过去一年度的总用电量为12 054 k W·h,其中空调用电量为9 332 k W·h,占到总用电量的77.4%。全年光伏能源替代率为34%,过渡季节可实现光伏能源替代率最高达180%。独立住宅上存在较大的节能空间和光伏能源替代率提升空间。     

Efficiency characteristic of building integrated photovoltaics as a shading device

A building-integrated photovoltaic system (BIPV) has been operated over 1 year in the Samsung Institute of Engineering & Construction Technology (SIECT) in Korea. The PV cells are mounted on the south facade and on the roof of the SIECT in the Giheung area. Special care was taken in the building design to have the PV modules shade the building in the summer, so as to reduce cooling loads, while at the same time allowing solar energy to enter the building during the heating season, and providing daylight. This paper gives a 1 year analysis of the system performance, evaluation of the system efficiency and the power output, taking into account the weather conditions. As a part of certain design compromises, that took into account, aesthetic, safety, and cost considerations, non-optimal tilt angles and occasional shading of the PV modules made the efficiency of PV system lower than the peak rating of the cells. The yearly average efficiency of the sunshade solar panel is 9.2% (average over 28.6°C surface temperature), with a minimum of 3.6% (average over 27.9°C surface temperature) in June and a maximum of 20.2% (average over 19.5°C surface temperature) in December.     

试论光伏并网配电系统谐波治理的分析与研究

随着科技水平的不断提高,太阳能发电逐渐成为可能,而且与常规能源更加得接近,光伏并网发电的优势也逐渐显现出来。在我国很多地区（如江苏省等）,光伏发电已经作为一种可靠的再生能源,广泛地应用于办公、酒店、机场、商场等建筑。光伏发电在光伏并网发电系统中,采用的是电子装置,非线性负载对并网配电系统的电能质量影响比较大,尤其是谐波影响。本文将对光伏并网配电系统进行分析,并在此基础上就符合有效治理谐波,谈一下自己的观点和认识,以供参考。     

50kWp屋顶分布式光伏并网发电系统的研究

结合天津地区某小区屋顶分布式光伏发电系统,对其运行状态进行实时测试和分析。从发电效率、累计发电量、逆变器效率等指标评价实际工程的运行效果。针对分布式发电的特点,比较售楼处4个发电单元的运行情况,验证了发电单元朝向正南、倾角为当地纬度安装才有最佳的运行效果。并网逆变器能在阵列输出功率较小时达到较高的效率,且能量损失小。     

Performance prediction of 60 kWp PV power plant in an educational institute

Due to government initiatives, many solar photovoltaic (PV) power plants of different sizes will be set up in India in the near future. In this context, the performance of a 60?kW_p PV power plant is discussed in this paper which is installed at National Institute of Technology (a centrally funded institute of Government of India), Agartala, located in a small state (Tripura) of North East India where supply of grid electricity is a critical issue. This article examines the various parameters for performance prediction of this solar power plant.     

空冷型自动追光百叶帘式光伏窗的应用研究

简述了国内外光伏技术在建筑窗体上的研究及应用现状,设计了一种自动追光百叶帘式光伏窗,将薄膜太阳能光伏片取代传统百叶帘中的百叶并内置于中空双层窗中,调节室内采光量的同时还能获得电能收益。通过光敏元件的控制使其具有追踪太阳光的能力,光伏百叶倾角的调节过程将形成扰流,加速空冷散热,进而提高光电转换效率。此外,利用不同的工作模式将散热量与室内外进行热量交换,进一步提升了光伏的发电效率,极大降低了室内建筑能耗,在建筑环境与能源应用领域拥有着广大的市场前景。     

Experimental Study of the Fire Behaviour on Flat Roof Constructions with Multiple Photovoltaic (PV) Panels

Fire experiments were conducted on four mock-up roof constructions with an array of six photovoltaic (PV) panels to study the fire dynamics and flame spread behaviour, so as to better characterise the fire risks of such a system. As it is customary to retrofit PV panels to existing warehouse roofs, where expanded polystyrene (EPS) and polyvinylchloride-based roofing membrane B_ROOF(t2) is a typical roofing, the experiments were carried out on such installations, but with a mitigation solution on top; 30 mm mineral wool or 40 mm polyisocyanurate (PIR). All mock-ups were 6.0 m long, whereas the width was 2.4 m (Experiments 1 and 2) and 4.8 m (Experiments 3 and 4), respectively. A wood crib was placed under the PV panels and it ignited the roofing membrane after 7 min to 8 min, which in all four experiments resulted in fire spread under all the six PV panels covering an area of 5.1 m?×?2.0 m. However, no self-sustained fire was observed beyond the area below the PV array. Within the first hour, the maximum temperatures were measured to respectively 175 °C and 243 °C underneath the two mitigation solutions of PIR insulation and mineral wool, which is more than 100 °C below the piloted ignition temperature for the EPS insulation. However, the EPS was ignited in both experiments with the PIR insulation due to thermal degradation of the protective material after approximately 1 h. These experiments confirm that a small initial fire underneath a PV installation can transform into a hazardous scenario due to the changed fire dynamics associated with adding the PV panels to the existing roof.     

石墨填充式PV/T系统光电光热性能试验

设计制作了一种以高导热材料——石墨为填充介质的新型PV/T结构,并搭建了该PV/T系统的光电光热性能综合试验台,在大连地区对其光电光热性能进行了试验研究。研究结果表明：在天气晴朗的情况下,与普通PV板相比,石墨填充式PV/T系统的输出功率相对提高可达120.67%;系统的瞬时热效率可达28.68%;系统水经过一天的循环,可使水箱温度上升至38℃。     

Effect of building integrated photovoltaics on microclimate of urban canopy layer

Building integrated photovoltaics (BIPV) has potential of becoming the mainstream of renewable energy in the urban environment. BIPV has significant influence on the thermal performance of building envelope and changes radiation energy balance by adding or replacing conventional building elements in urban areas. PTEBU model was developed to evaluate the effect of photovoltaic (PV) system on the microclimate of urban canopy layer. PTEBU model consists of four sub-models: PV thermal model, PV electrical performance model, building energy consumption model, and urban canyon energy budget model. PTEBU model is forced with temperature, wind speed, and solar radiation above the roof level and incorporates detailed data of PV system and urban canyon in Tianjin, China. The simulation results show that PV roof and PV façade with ventilated air gap significantly change the building surface temperature and sensible heat flux density, but the air temperature of urban canyon with PV module varies little compared with the urban canyon of no PV. The PV module also changes the magnitude and pattern of diurnal variation of the storage heat flux and the net radiation for the urban canyon with PV increase slightly. The increase in the PV conversion efficiency not only improves the PV power output, but also reduces the urban canyon air temperature.     

一种光伏应用新技术

本文总结目前光伏应用现状,在简要说明离网式和并网式应用的主要特点和问题后,指出目前太阳能光伏发电在建筑领域应用的主要技术障碍是由于存在逆向功率问题.本文详细介绍了光伏微电网共网应用新技术,指出这是一种针对建筑光伏应用的、将分散建筑上的分散阳光分散变成光伏电力分散使用的新技术.     

高效非逆变光伏技术理论基础

关于光伏应用形式的主要争论之一,是光伏电力的逆变应用与非逆变应用之争。其实"逆变"只是电力技术中一种直流变交流的方法,逆变与非逆变的本质区别,并不在于采用该方法与否。在逆变应用中也有直流线路,非逆变应用中也有逆变装置。关键问题是,被统称为"逆变并网"的逆变应用,是推崇用光伏电力取代市电的一种思潮,并长期以来作为主流观点在光伏应用领域占统治地位。而非逆变应用就不赞成这种应用形式,并且有针对性地提出了许多不同意见,归结起来有3条:第一,不必要,因为直流电、交流电都可以应用,将直流低压的光伏电力变成高压交流电去适应普通电气应用是多余而又降低效率的环节;第二,问题复杂化,因为光伏电力的输出功率不稳定,又不采用储能装置,依附电网上的负载卸载,势必给网电造成影响,从而发生一系列技术问题和与电力部门的协调问题,人为增加了光伏电力应用的困难;第三,经济上不合算,无论如何,光伏电力成本的价格还是远高于市电。而逆变应用反驳得不太有说服力,除了第一条所说的应用方便之外,其余2条对于实际问题的解决,至今没有实质性的进展。