Performance analysis of various system configurations on grid-connected residential PV systems

Performance and loss analysis of residential photovoltaic (PV) systems are conducted using the sophisticated verification (SV) method. Performance of the various system configurations is quantitatively analyzed and compared in this paper. The south-oriented systems have approximately 22% more reference yield than the systems that are not oriented south. Difference of the module manufacturers shows more than 10% differences of the performance ratio whereas array configuration shows less difference. Imbalance of the string voltages causes system peak power loss and MPP mismatch. This loss cannot be minimized by the DC/DC converter in most of the systems.     

采用空间矢量调制方法的光伏并网系统滞环电流控制

文章研究了基于空间矢量调制概念的光伏并网系统滞环电流控制技术。该技术使用双滞环控制器获取电流误差信息,内滞环使输出电流在限定范围内,外滞环确定输出指令电压信号的空间位置。根据电流误差信号优化并网逆变器输出电压矢量,使误差电流信号变化速度降低,从而使逆变器的开关频率降低。该技术结合了空间矢量控制及滞环电流控制方法的优点,提高了逆变装置直流端的电压利用率,系统响应速度快,并且减少装置的散热及能量损失,使系统高效运行     

多逆变器光伏并网发电系统的群控策略和实现方法

光伏并网发电系统由光伏阵列和逆变器两个组群构成.根据光伏并网发电系统的特点和需求,以提高发电效率、改善电能质量、完善监测功能为目的,首次提出一体化的群控装置和群控策略,对大容量光伏阵列和多逆变器组群进行统一监测和协调控制.给出了光伏阵列/逆变器组轮循投切的具体实现方法、无功补偿的统一群控方法、以及监控功能和群控器的实现方法.     

Performance results and analysis of 3 kW grid-connected PV systems

Four 3 kW grid-connected photovoltaic (PV) generation systems have been installed and monitored at the Field Demonstration Test Center in Korea since October 2002. To observe the overall effect of meteorological conditions on their operation characteristics by field test, the monitoring system has been constructed for measuring and analyzing the performance of PV systems and components in November 2002. In this paper, the performance of PV systems is evaluated and analyzed not only for component perspective but also for global perspective by reviewing one year of monitoring results and loss factors of PV systems. On the basis of these monitoring results, the performance of PV systems is compared to the measured performance of PV systems with the estimated performance by simulation. These results will indicate that it is highly imperative to develop evaluation, analysis and application technology for PV systems.     

A voltage regulation method for dispersed grid-connected PV systems under high-density connection

This paper describes a voltage regulation method for dispersed grid-connected PV systems under high-density connection. In the near future, many PV systems will be connected to distribution systems. The reverse power flow of the grid-connected PV systems will raise line voltage to the upper limit of the legal voltage range. In the first part of this paper we examine the voltage characteristics of a distribution system under high-density connection, while the second part of the paper describes a voltage regulation method for high-density PV connections, using reactive power proportional to global irradiance. The results of tests clearly demonstrate a restraining effect on voltage during the daytime and a smoothing effect on voltage fluctuation.     

Monitoring and remote failure detection of grid-connected PV systems based on satellite observations

Small grid-connected photovoltaic systems up to 5 kW_p are often not monitored because advanced surveillance systems are not economical. Hence, some system failures which lead to partial energy losses stay unnoticed for a long time. Even a failure that results in a larger energy deficit can be difficult to detect by PV laymen due to the fluctuating energy yields.Within the EU project PVSAT-2, a fully automated performance check has been developed to assure maximum energy yields and to optimize system maintenance for small grid-connected PV systems. The aim is the early detection of system malfunctions and changing operating conditions to prevent energy and subsequent financial losses for the operator. The developed procedure is based on satellite-derived solar irradiance information that replaces on-site measurements. In conjunction with a simulation model the expected energy yield of a PV system is calculated. In case of the occurrence of a defined difference between the simulated and actual energy yield, an automated failure detection routine searches for the most probable failure sources and notifies the operator.This paper describes the individual components of the developed procedure—the satellite-derived irradiance, the used PV simulation model, and the principles of the automated failure detection routine. Moreover, it presents results of an 8-months test phase with 100 PV systems in three European countries.     

Review of the performance of residential PV systems in France

The main objective of this paper is to review the state of the art of residential PV systems in France. This is done analyzing the operational data of 6868 installations. Three main questions are posed. How much energy do they produce? What level of performance is associated to their production? Which are the key parameters that most influence their quality? During the year 2010, the PV systems in France have produced a mean annual energy of 1163 kWh/kW_p. As a whole, the orientation of PV generators causes energy productions to be some 7% inferior to optimally oriented PV systems. The mean Performance Ratio is 76% and the mean Performance Index is 85%. That is to say, the energy produced by a typical PV system in France is 15% inferior to the energy produced by a very high quality PV system. On average, the real power of the PV modules falls 4.9% below its corresponding nominal power announced on the manufacturer's datasheet. A brief analysis by PV modules technology has led to relevant observations about two technologies in particular. On the one hand, the PV systems equipped with heterojunction with intrinsic thin layer (HIT) modules show performances higher than average. On the other hand, the systems equipped with the copper indium (di)selenide (CIS) modules show a real power that is 16% lower than their nominal value.     

A new estimation method of irradiance on a partially shaded PV generator in grid-connected photovoltaic systems

A new method for estimating the irradiance on a partially shaded photovoltaic generator system is proposed. The basic principle of this method consists of two parts: firstly, an approximation of the obstacles’ outline or the local horizon by a set of linear functions. Here, a survey of the surroundings is based on the reading of the topographic coordinates of the only significant points of all the objects surrounding the photovoltaic generator. Secondly, the irradiance on the photovoltaic plane is estimated using an accurate model such as the Perez et al. model and assuming that the shading affects both the direct radiation and a part of the diffuse component (circumsolar component).The aim of this paper is to present the principles of the proposed method and the algorithm used for calculating the irradiance on shaded planes. In addition, the results of the comparison between the simulated and measured values of this method are presented.     

Review of the performance of residential PV systems in Belgium

The main objective of this paper is to review the state of the art of residential PV systems in Belgium by the analysis of the operational data of 993 installations. For that, three main questions are posed: how much energy do they produce? What level of performance is associated to their production? Which are the key parameters that most influence their quality? This work brings answers to these questions. A middling commercial PV system, optimally oriented, produces a mean annual energy of 892 kWh/kW_p. As a whole, the orientation of PV generators causes energy productions to be some 6% inferior to optimally oriented PV systems. The mean performance ratio is 78% and the mean performance index is 85%. That is to say, the energy produced by a typical PV system in Belgium is 15% inferior to the energy produced by a very high quality PV system. Finally, on average, the real power of the PV modules falls 5% below its corresponding nominal power announced on the manufacturer's datasheet. Differences between real and nominal power of up to 16% have been detected.     

光伏并网电站数据采集监测系统

描述了计算机控制系统在光伏并网电站中的应用。介绍了数据采集监测系统的硬件结构以及软件的设计和实现。系统的硬件有并网逆变器、传感器、数据采集器等;系统的软件具有采集、处理、储存和查询功能。该数据采集监测系统为获取太阳能并网光伏电站的运行数据提供保证。     

带升压变压器的光伏并网逆变器控制与实现

光伏并网逆变器中的升压变压器可能因直流偏磁给逆变器和电网带来危害,针对光伏并网逆变器的闭环PI参数设计以及变压器直流偏磁的问题,分析了并网逆变器直流偏磁产生的原因以及对逆变电器的影响。给出了PI参数的整定方法,提出了一种抑制直流偏磁的控制策略,并在一台3 k W并网逆变器上进行了实验。实验结果表明,PI设计参数合适,该策略能够有效抑制直流偏磁。     

On the value of decentralised PV systems for the GCC residential sector

Based on the rich natural potential of the Gulf region, solar energy is expected to play a greater role in the future of the Gulf Corporation Council (GCC) countries. This study examines whether the integration of the photovoltaic (PV) into individual residential buildings in the GCC countries is worth the investment. A prototype residential building is developed and a building integrated photovoltaic (BiPV) system is then designed. The system performance is simulated, and through economic analysis, it is shown that the current BiPV technology is not a cost-effective option for the GCC countries based on the present electricity tariff, PV system cost and system efficiency. The only way such a system would be viable with current technology is if the electricity tariff were to increase substantially. However, if the tariff remains constant for the foreseeable future, BiPV solar energy technology will only be feasible if the total system cost drops drastically. This study shows that BiPV systems offer cost reductions in both energy and economic terms over centralised PV plants, especially if the costs of avoided building construction materials are taken into account. To bring about the benefits of BiPV technology for the GCC residential sector, therefore, the first logical and most practical step is the implementation of a continuous promotion strategy that consists of both subsidies for investments and reasonable tariffs.     

Measurements, analyses and evaluation of residential PV systems by Japanese monitoring program

This paper is about measurements, analyses and evaluation of residential PV systems in the Japanese Monitoring Program, on which JQA was subsidized by NEDO (New Energy Development and Industrial Technology Organization) that is currently proceeding [NSS R&D] from FY1997 to FY 2000.The aim of this investigation refers, through the data evaluation and analyses, to obtain knowledge required for optimizing design of PV systems, such as system performance, characteristics and regional dependency under practical operation and to develop the system evaluation technology on the design parameter method.     

Overview of the state of technique for PV inverters used in low voltage grid-connected PV systems: Inverters below 10 kW

An analysis has been made of the most important electrical parameters related to photovoltaic grid-connected inverters below 10 kW. To achieve this, a compilation of up to 50 manufacturers, various brands and up to 500 different models has been prepared and updated to February 2008. Datasheet and manuals have been compiled, noting down their electrical output and input characteristics. Different and important aspects with respect to performance of some PV grid-installation have been analyzed: the number of different models for values of power; topology option; operational DC parameters range (such as nominal power, maximum power, nominal current, voltage), operational AC parameter range (such as nominal power, maximum power, nominal current, voltage), inverter conversion efficiency vs nominal power and normalized inverter size and weight.     

网间规模化光伏并网对系统阻尼的影响及优化措施

电力系统受到大扰动后,其振荡中心电压大幅波动,受此影响,其近区规模化光伏汇集线功率会出现显著波动,加剧光伏与电网交互作用。文章基于光伏暂态仿真模型,分析了并网电压低频跌落或回升过程中,光伏并网系统暂态功率特性;基于等面积原理,分析了不同控制方式下光伏并网系统等值电纳Bpv的Us-Bpv轨迹及其对振荡的影响,并据此揭示了光伏并网系统对电网振荡阻尼的作用机制。通过两区域四机系统受扰时域仿真,验证了基于光伏并网系统Us-Bpv轨迹特征,评估其对系统阻尼影响的有效性,在此基础上,指出利用附加阻尼控制的SVG具有增强系统正阻尼作用。     

Modeling and simulation of a grid-connected PV generation system for electromagnetic transient analysis

This paper addresses modeling and simulation of a grid-connected photovoltaic system (GCPS) to analyze its grid interface behavior and control performance in the system design. A simple circuit model of the solar array is used to easily simulate its inherent characteristics with the basic specification data. Detailed power and protection control of the GCPS as well as its electrical circuits have been represented by user-defined and built-in components to take into account transients in normal and fault conditions, which are dominated by its power electronic controller. The model has been described with the reference to and implemented in PSCAD/EMTDC, a power system transient software package. Extensive simulation results are presented and analyzed to validate that the proposed simulation model is effective for control and protection performance evaluation of the GCPS in terms of electromagnetic transient analysis.     

Projected costs of a grid-connected domestic PV system under different scenarios in Ireland,using measured data from a trial installation

This paper presents results of a study of projected costs for a grid-connected PV system for domestic application in Ireland. The study is based on results from a 1.72 kWp PV system installed on a flat rooftop in Dublin, Ireland. During its first year of operation a total of 885.1 kWh/kWp of electricity was generated with a performance ratio of 81.5%. The scenarios employed in this study consider: a range of capital costs; cost dynamics based on a PV module learning rate of 20±5%; projections for global annual installed PV capacity under an advanced and moderate market growth conditions; domestic electricity cost growth of 4.5% based on historic data; and a reduction of 25% or 50% in the CO₂ intensity of national electricity production by 2055. These scenarios are used to predict when system life cycle production costs fall to grid prices (grid parity).     

DC current injection into the network from PV inverters of <5 kW for low-voltage small grid-connected PV systems

The present paper is focused on the study of DC current injection for low-voltage small grid-connected PV systems, which is one of the power quality requirements of utility companies. To achieve this aim, the existing status of guidelines and regulations in six selected countries where the development in the grid PV sector has evolved rapidly over the last decade (Australia, Germany, Japan, Spain, the United Kingdom and the United States) has been reviewed according to the DC current injection into the grid. Furthermore, a grid-connected system installed in Spain has been used to carry out measures concerning possible DC current injection into the grid. Thus, 12 single-phase inverters <5 kW (according to the transformer options: 50 Hz LF transformers, HF transformers or transformerless) from the European market have been tested. Many groups of measurements were made under different conditions. The results show that in all cases there is DC current injection, even if an LF transformer inverter is used.     

Optimal sizing of a grid-connected PV system for various PV module technologies and inclinations, inverter efficiency characteristics and locations

An optimal sizing methodology based on an energy approach is described and applied to grid-connected photovoltaic systems taking into account the photovoltaic module technology and inclination, the inverter type and the location. A model describing the efficiency for m-Si, p-Si, a-Si and CIS is used. The method has been applied on various meteorological stations in Bulgaria and Corsica (France). The main parameter affecting the sizing is the inverter efficiency curve. The influence of the PV module technology seems less important except for amorphous photovoltaic modules for which special remarks have been made. The inclination on the PV system influences the performances particularly when the inverter is undersized compared to the PV peak power.     

Trade-off between environmental and economic implications of PV systems integrated into the UAE residential sector

PV technology offers clean resource and environmental advantages over fossil-fuel-based electricity generation; however, it remains more expensive than conventional technology in most grid-connected applications. The trade-off between environmental and economic parameters represents a challenge for governments. The objectives of this study are: firstly, to review studies in relation to the use of PV systems in the Gulf region and secondly, to assess the trade-off between environmental and economic parameters that influence the value of building integrated photovoltaic (BiPV) technology applied into the UAE building sector. This work examines residential buildings and concludes that the economic viability of BiPV systems is subject to capital cost, system efficiency and electricity tariff. To be a cost-effective option in the UAE, subsidies for PV investments and reasonable electricity tariff must be implemented. It is suggested that BiPV systems offer cost reductions in both energy and economic terms over centralised PV plants, especially if the costs of saved operating energy and avoided building materials are taken into account. Each square meter of BiPV is capable of making a significant reduction in CO₂ emissions generated by conventional power plants. This will limit the impact of global warming on the UAE and others.