Optimal allocation and sizing for profitability and voltage enhancement of PV systems on feeders

This paper presents a systematic algorithm to determine the optimal allocation and sizing of Photovoltaic Grid-connected Systems (PVGCSs) in feeders that provides the best overall impact onto the feeder. The optimal solution is reached by multi-objective optimization approach. Both technical and economical objective functions are taken into account in the optimization procedure. The technical objective is related with the improvement of the distribution feeder voltage conditions. The economical objective is associated with the profitability both PV generation and potential loss reduction on the feeder. This procedure aims at finding the PV solution that yields the best compromise for the two considered objectives between various potential candidates of PVGCSs well known. The results obtained with the proposed methodology for feeders found in the literature demonstrate its applicability.     

Impact of active power curtailment on overvoltage prevention and energy production of PV inverters connected to low voltage residential feeders

As non-controllable power sources, photovoltaics (PV) can create overvoltage in low voltage (LV) distribution feeders during periods of high generation and low load. This is usually prevented passively by limiting the penetration level of PV to very conservative values, even if the critical periods rarely occur. Alternatively, one can use active power curtailment (APC) techniques, reducing the amount of active power injected by the PV inverters, as the voltage at their buses increase above a certain value. In this way, it is possible to increase the installed PV capacity and energy yield while preventing overvoltage. This paper investigates a number of approaches for sizing and controlling the PV power generated by 12 net-zero energy houses equipped with large rooftop PV systems in a typical 240 V/75 kVA Canadian suburban radial distribution feeder. Simulations of a one year period with typical solar irradiance and load profiles are conducted with PSCAD to assess the performance of the different approaches in terms of overvoltage occurrence, sharing of the burden for overvoltage prevention per house and total energy yield of the residential PV feeder.     

A photovoltaic voltage regulation impact investigation technique.I. Model development

With changing weather patterns or clouds moving over a given utility service area, the power generated by any photovoltaic (PV) power systems in that service area will vary tremendously. Depending on the percentage penetration of these PV systems on a distribution feeder, these variations in the PV systems' performance may cause undesirable voltage fluctuations along the feeder and also may impact the operation of the voltage regulating equipment on the distribution feeder. A computer program was developed to allow the utility engineer to determine the impact of the fluctuating PV generation due to moving cloud patterns. This impact is determined on the distribution system level by monitoring the feeder voltage profile and the operation of any voltage regulating devices. The model is rigorous and includes modeling capabilities beyond those of previous investigations     

链条锅炉分层给煤装置的功能与发展

剖析了链条锅炉分层给煤装置的几种形式，介绍了三辊式，二辊式分层给煤装置的特点，并叙述了选择分层燃烧装置的几个要领。     

Impact of residential photovoltaic power systems on the electric utility in Cairo, Egypt

The impact of utility-interactive residential photovoltaic (PV) power systems on the electric utility was studied. Power flow analyses were performed before and after the introduction of PV, on a subtransmission and distribution network model of an actual residential utility feeder serving a suburban area of Helwan in Cairo, Egypt. The changes in bus voltages and utility power factor were used to assess the impacts caused by the PV introduction. PV systems were examined at different penetration levels and were introduced in the low- and high-voltage buses of the distribution circuit. PV power factors as low as 0·7 were used to account for various power conditioner designs. PV-utility interconnection at the high-voltage distribution level is recommended since it results in acceptable voltage regulation throughout the network as well as a good utility power factor.     

Impact of Residential Photovoltaic Power Systems on the Distribution Feeder

A computer study was conducted to evaluate the impact of distributed residential photovoltaic power system on the feeder. This study indicated that the PV system would not seriously effect the feeder voltage. It also indicated that an inverter power factor of 0.85 would be acceptable.     

Impact of widespread photovoltaics generation on distribution systems

Prompted by the need for clean energy sources, increasing numbers of photovoltaic (PV) generators are being connected to electricity distribution systems around the world. There is thus a growing imperative to understand and quantify the technical impact that high penetrations of such generators may have on the operation and performance of electricity distribution systems. Detailed simulations of a very high penetration of PV within a typical UK urban distribution network (11 kV, 400 V and 230 V) are reported. The study performed unbalanced three-phase load-flow analysis on an entire feeder within a time-domain simulation framework using load and generation data at 1 minute intervals. The results indicate that even at very high penetrations of PV, network voltage rises are small and unlikely to cause problems. Effects on network power flows and losses are also quantified and discussed     

Options for improving the load matching capability of distributed photovoltaics: Methodology and application to high-latitude data

At high latitudes, domestic electricity demand and insolation are negatively correlated on both an annual and a diurnal basis. With increasing integration of distributed photovoltaics (PV) in low-voltage distribution grids of residential areas, limits to the penetration level are set by voltage rise due to unmatched production and load. In this paper a methodology for determining the impacts of three options for increased load matching is presented and applied to high-latitude data. The studied options are PV array orientation, demand side management (DSM) and electricity storage. Detailed models for domestic electricity demand and PV output are used. An optimisation approach is applied to find an optimal distribution of PV systems on different array orientations and a best-case evaluation of DSM and a storage model are implemented. At high penetration levels, storage is the most efficient option for maximising the solar fraction, but at lower overproduction levels, the impact of DSM is equal or slightly better. An east-west orientation of PV arrays is suggested for high penetration levels, but the effect of the optimised orientation is small. Without an optimised storage operation, the overproduced power is more efficiently reduced by DSM than storage, although this is highly dependent on the applied DSM algorithm. Further research should be focused on the DSM potential and optimal operation of storage.     

Interline fuel cell (I-FC) system with dual-functional control capability

In this paper, a new system concept is presented for the grid connection of fuel cells. In conventional grid-connected systems, fuel cells ensure the generated power into a single electrical feeder and control the electrical-line through interfacing elements. In the proposed system, interline fuel cell (I-FC) system shares a common dc-dc converter tied fuel cell at the base of inverters and eliminates the additional fuel cell & dc-dc converter in a multi-feeder system. For this purpose, a fuel cell system is connected to multi-feeders through separate inverters, thereby sharing electrical power into the feeders and attenuating the harmonics at grid-side currents. In this direction, the proposed system presents an economical way for the mitigation of electrical problems for multi-feeders. In order to achieve the functional capabilities of I-FC system, dual-functional control is separately applied in the grid inverters. In the testing stage of I-FC, nonlinear loads in feeder I & feeder II create 31.29% and 27.61% total harmonic distortion (THD) at grid-side currents, respectively. With I-FC, the THD values are reduced to approximately 3% values in both feeders after the harmonic elimination capability. Also, I-FC allocates the active power to both feeders, and reduces the electrical power demand from the utility-grids. The evaluation results verify that I-FC system accomplishes the good performance to control power-sharing and attenuate the current harmonics at grid-side.     

智能配电网馈线自动化发展及展望

分析了馈线自动化发展情况,指出目前的馈线自动化系统对通信依赖太强,并不适合于配电馈线。提出了需要研究具有选择性、能够快速切除馈线故障并具有故障自愈能力的智能配电网,并就智能化馈线自动化系统组成进行了探讨,分析了其研究方向和需要解决的问题。     

Calculation of the PV modules angular losses under field conditions by means of an analytical model

Photovoltaic (PV) modules in real operation present angular losses in reference to their behaviour in standard test conditions, due to the angle of incidence of the incident radiation and the surface soil. Although these losses are not always negligible, they are commonly not taken into account when correcting the electrical characteristics of the PV module or estimating the energy production of PV systems. The main reason of this approximation is the lack of easy-to-use mathematical expressions for the angular losses calculation. This paper analyses these losses on PV modules and presents an analytical model based on theoretical and experimental results. The proposed model fits monocrystalline as well as polycrystalline and amorphous silicon PV modules, and contemplates the existence of superficial dust. With it angular losses integrated over time periods of interest can be easily calculated. Monthly and annual losses have been calculated for 10 different European sites, having diverse climates and latitudes (ranging from 32° to 52°), and considering different module tilt angles.     

一种新型气力式给煤粉装置的研制与实验

在分析总结几种气力式给粉装置的基础上,针对煤粉低尘燃烧技术工程开发中遇到的给粉量不均匀、不稳定等问题,设计了一种直立螺旋-气固喷射器小型给粉装置,该给粉装置巧妙地组合了螺杆与喷射器两个部件,结构简单,控制方便。实测数据结果表明,该装置满足小型煤粉燃烧器供煤量的要求,研制的产品达到了实用化水平。     

Heterogeneity in the adoption of photovoltaic systems in Flanders

We study the determinants of PV adoption in the region of Flanders (Belgium), where PV adoption reached high levels during 2006–2012, because of active government intervention. Based on a unique dataset at a very detailed spatial level, we estimate a Poisson model to explain the heterogeneity in adoption rates. We obtain the following findings. First, local policies have a robust and significant impact on PV adoption. Second, there is a strong unconditional income effect, implying a Matthew effect in the subsidization of PVs. Our third finding is however that this income effect is largely driven by the fact that wealthier households are more likely to adopt because they tend to be higher users, are more frequent house owners, or own houses that are better suited for PV. In several extensions, we consider the determinants of the average size of installed PVs, and the differential impact of certain variables over time.     

基于分散电源和配电网重构的多馈线升级延缓规划

研究了分布式发电技术在延缓配电网升级中的作用,以多条出现线路过载的配电馈线为研究对象,同时采用分布式发电技术和传统的配电网重构技术消除所有馈线过载;建立了以所有馈线损耗最小为目标的函数并考虑线路容量约束、分散电源渗透功率约束和配电网孤岛运行约束等的扩容规划数学模型,该规划模型同时考虑了多年的负荷增长对线路过载的影响;采用混合粒子群优化算法（HPSO）进行模型求解,IEEE16节点3馈线测试系统的仿真结果表明模型和算法的可行性和有效性,对于分布式发电技术在电力系统中的应用具有重要的指导意义。     

Photovoltaic-grid connection in the UAE: Technical perspective

Connection of utility-interactive PV generators at the distribution level, namely PV distributed generation (PVDG), could bring many benefits to the distribution network. However, deployment of PVDG systems, in any country, requires actual data on the performance of these systems under actual weather conditions. Additionally, it needs compliance with the electrical structure and regulations of the power distribution network in that country. Hence, applying PVDG technology in the UAE brings forth many considerations and this work aims at tackling potential technical ones. Among these is the role of daily load curve and PV production curve in determining feasible locations and capacities of PVDG systems. The analyses are based on existing case study feeders at the 11 kV level of Abu Dhabi distribution network. Accordingly, the work results in suitable recommendations on feasible locations of PVDG systems. Also it defines rational objectives and constraints for optimal sizing and location of such systems.The other consideration tackled in this work is the performance of PVDG systems in actual UAE weather conditions. Actual data from two pilot PVDG systems installed in Abu Dhabi are collected and analyzed. The production of PV array, consistency of voltage and frequency and the conversion efficiency of PV modules and inverters along with the impact of ambient temperature are considered. In the same connection, the influence of accumulated dust deposition on the production of PV array in UAE is also taken over in this work.     

光伏发电系统增加单轴跟踪装置的经济性分析

通过计算全国46个地区东西向平单轴、南北向平单轴、斜单轴三种单轴跟踪光伏系统相对于固定式光伏系统(同样条件下)增加成本的收回年数及偿还增加成本后的年净收益,指出了各种单轴跟踪方式在不同纬度、不同海拔地区的适用性,对各地区拟建的光伏电站是否使用单轴跟踪、选用何种单轴跟踪方式提供参考.     

循环流化床锅炉给煤机多点给煤遇到的问题和对策

循环流化床锅炉给煤机多点给煤系统出现的问题,既有系统和设备设计本身先天不足的因素,也有对系统运行方式选择不当的原因。配煤口设计不能满足均匀给煤需要是主要原因之一。提出了相应的解决方法和正确的系统运行方式。     

建筑光伏系统电池姿态与可吸收辐射量的关系

该文探讨了在大气混浊化的趋势下，建筑光伏系统如何加强对散射辐射的吸收，以及在姿态上如何适应太阳辐射的年周期变化和日周期变化，以获得较低的单位电价、较高的场所总发电量和较稳定的输出。在此基础上，对光伏系统在建筑顶面上采用不同姿态方案的单位电价与场所总发电量进行了评价，从中得出了不同纬度和辐射条件下光伏组件在顶面的布置方式。     

含高渗透率分布式光伏的主动配电网电压分区协调优化控制

随着高渗透率分布式光伏的接入,配电网的过电压问题愈发严重,传统集中式的电压优化控制方法因为变量维数过多而无法满足控制时间的要求.基于此,该文提出一种主动配电网电压分区协调优化控制的方法.首先提出无功/有功分区质量函数作为分区指标,并以网络快速分区算法对配电网进行无功、有功分区.在无功分区内,以无功调节量最少为目标建立光...     

Optimal sizing of array and inverter for grid-connected photovoltaic systems

Optimum PV/inverter sizing ratios for grid-connected PV systems in selected European locations were determined in terms of total system output, system output per specific cost of a system, system output per annualised specific cost of a system, PV surface orientation, inclination, tracking system, inverter characteristics, insolation and PV/inverter cost ratio. Maximum total system output was determined for horizontal, vertical and 45° inclined surfaces for a low efficiency inverter for sizing ratios of 1.5, 1.8 and 1.3, respectively; and for a medium efficiency inverter with sizing ratios of 1.4, 1.5 and 1.2. PV surface orientation and inclination have little impact on the performance of a high efficiency inverter. For different PV tracking systems and for different inverter characteristics, the optimum sizing ratio varied from 1.1 to 1.3. The PV/inverter cost ratio and the PV and inverter lifetimes have significant impact on the optimum PV/inverter sizing ratio. A correlation relating optimum sizing ratio and PV/inverter cost ratio has been developed; the correlation coefficients were found to be functions of insolation and inverter type. The impact of PV/inverter sizing ratio on PV array performance was less when PV array has a much higher cost than the inverter. The optimum sizing ratio for PV/inverter cost ratio of 6 and low efficiency inverter system varied from 1.4 to 1.2 for low to high insolation sites. For a high efficiency inverter system, the corresponding variation was from 1.3 to 1.1.