Grid-connected Photovoltaic Power Research Articles

Utility scale photovoltaic plant indices and models for on-line monitoring and fault detection purposes

Improving reliability and reducing maintenance and operating costs have become important factors in increasing the competitiveness of photovoltaic (PV) systems. For grid connected PV power plants every kilowatt-hour is crucial, because only kilowatt-hours that are fed into the grid are remunerated.A plant's operator can only adopt prompt measures to eliminate operational faults when these are immediately signaled. In fact, just reading the feed-in meter periodically is not sufficient to promptly recognize faults and to avoid the loss of yields. For this reason, continuous, absolute and comparative measurements are necessary to ensure the highest efficiency and availability of photovoltaic plants. Specifically, comparing the estimated, by means of suitable models of the PV plant, and the measured power allows to provide information on the operating status of the photovoltaic systems and so to perform preventive and/or reparative maintenance.In this context, a physical model has been developed and compared with other models to estimate the DC and AC power. Further, a novel figure of merit, named Non-Uniformity Index is proposed. It permits to individuate those cases the whole system, which is composed of many sections, e.g. PV fields, is working with a sufficient efficiency, but one or more photovoltaic fields are working at lower efficiencies compared to the others.The quality of the measured data has a significant influence on the estimation accuracy of the performance model and thus on the monitoring system, for this reason, models for irradiance and PV module temperature are used to check the measured data for inconsistency and other anomalies.Based on such models, a straightforward methodology for PV plants monitoring and fault detection purposes, which allows to minimize the number of required sensors and that can be applied to PV plants of any dimension, has been developed.The proposed methodology has been applied to a utility scale PV power plant (rated 1MW), where a Supervisory Control and Data Acquisition system has been installed; operational data are saved on a remote server and available on a dedicated website. The experimental results show the effectiveness of the proposed approach. In order to have the possibility to analyze and compare the performance of the studied PV plant with others, the efficiency of the system has been estimated by both conventional Performance Ratio and Corrected Performance Ratio.

Multivariate Statistics and Supervised Learning for Predictive Detection of Unintentional Islanding in Grid-Tied Solar PV Systems

Integration of solar photovoltaic (PV) generation with power distribution networks leads to many operational challenges and complexities. Unintentional islanding is one of them which is of rising concern given the steady increase in grid-connected PV power. This paper builds up on an exploratory study of unintentional islanding on a modeled radial feeder having large PV penetration. Dynamic simulations, also run in real time, resulted in exploration of unique potential causes of creation of accidental islands. The resulting voltage and current data underwent dimensionality reduction using principal component analysis (PCA) which formed the basis for the application ofQstatistic control charts for detecting the anomalous currents that could island the system. For reducing the false alarm rate of anomaly detection, Kullback-Leibler (K-L) divergence was applied on the principal component projections which concluded thatQstatistic based approach alone is not reliable for detection of the symptoms liable to cause unintentional islanding. The obtained data was labeled and aK-nearest neighbor (K-NN) binomial classifier was then trained for identification and classification of potential islanding precursors from other power system transients. The three-phase short-circuit fault case was successfully identified as statistically different from islanding symptoms.

Life cycle assessment of grid-connected photovoltaic power generation from crystalline silicon solar modules in China

The environmental impacts of grid-connected photovoltaic (PV) power generation from crystalline silicon (c-Si) solar modules in China have been investigated using life cycle assessment (LCA). The life cycle inventory was first analyzed. Then the energy consumption and greenhouse gas (GHG) emission during every process were estimated in detail, and finally the life-cycle value was calculated. The results showed that the energy payback time (TEPBT) of grid-connected PV power with crystalline silicon solar modules ranges from 1.6 to 2.3years, while the GHG emissions now range from 60.1 to 87.3g-CO2,eq/kWh depending on the installation methods. About 84% or even more of the total energy consumption and total GHG emission occupied during the PV manufacturing process. The solar grade silicon (SoG-Si) production is the most energy-consuming and GHG-emitting process, which accounts for more than 35% of the total energy consumption and the total GHG emission. The results presented in this study are expected to provide useful information to enact reasonable policies, development targets, as well as subsidies for PV technology in China.

A real-time American Sign Language word recognition system based on neural networks and a probabilistic model

The photovoltaic power generation and active filter (PV-AF) system can realize photovoltaic grid-connected power regulation, and meanwhile it can also improve the power quality of power grid effectively. The four-leg grid-connected inverter has successfully been used in the three-phase four-wire system. In this paper, a three-dimensional space vector pulse width modulation (3D-SVPWM) method based on the gh$\gamma $ coordinate system for a four-leg inverter has been proposed. As the switching vectors of the four-leg inverter are in the three-dimensional space, it is difficult to realize the complex modulation process. In order to simplify the modulation process, the reference vector is placed into gh$\gamma $ coordinates in the proposed modulation strategy, and then the vectors are selected and the duration times are acquired directly by a group of intermediate variables, which could be obtained by linear transformation of the coordinates. As the intermediate variables are used, the modulation can be easily implemented by the proposed modulation strategy without excessive mathematical calculations. The simulation and experimental results all confirmed the validity and effectiveness of this strategy.

New three-dimensional space vector pulse width modulation of PV-AF system based on the gh$\gamma $ coordinate system

The photovoltaic power generation and active filter (PV-AF) system can realize photovoltaic grid-connected power regulation, and meanwhile it can also improve the power quality of power grid effectively. The four-leg grid-connected inverter has successfully been used in the three-phase four-wire system. In this paper, a three-dimensional space vector pulse width modulation (3D-SVPWM) method based on the gh$\gamma $ coordinate system for a four-leg inverter has been proposed. As the switching vectors of the four-leg inverter are in the three-dimensional space, it is difficult to realize the complex modulation process. In order to simplify the modulation process, the reference vector is placed into gh$\gamma $ coordinates in the proposed modulation strategy, and then the vectors are selected and the duration times are acquired directly by a group of intermediate variables, which could be obtained by linear transformation of the coordinates. As the intermediate variables are used, the modulation can be easily implemented by the proposed modulation strategy without excessive mathematical calculations. The simulation and experimental results all confirmed the validity and effectiveness of this strategy.

Research on Grid-Connected Photovoltaic Power System Based on Virtual Synchronous Generator

In order to realize the solar photovoltaic (PV) system connecting with grid friendly, a PV system with voltage-controlled inverter based on virtual synchronous generator (SG) is presented. This kind of system has features of SG, which supply the virtual moment of inertia to grid. The mathematical model of PV and virtual SG is built, and the control strategy of the maximum power point tracking (MPPT) is also studied in the paper. Simulation model of the grid-connected PV power system is built on Matlab/Simulink. Finally, correctness and feasibility of this system are verified by simulation results.

Transformerless DC/AC Converter for Grid-Connected PV Power Generation System

Transformerless photovoltaic (PV) systems have two shortcomings: low voltage not fulfilling load requirement and ground-leakage current flowing through parasitic capacitance between the PV panel and ground. Therefore, a DC/AC converter—a single-phase bipolar sinusoidal pulse width modulation (SPWM) H-Bridge power inverter configuration with a DC/DC high-gain conversion-boosting (CD-Boost) stage—is proposed. Its conversion ratio was compared with a conventional converter’s. It provides a high conversion ratio of the PV voltage before the DC is converted into AC for the load. The bipolar SPWM modulation technique is proposed for lower ground-leakage current, and the effectiveness of the proposed modulation technique was compared with the unipolar SPWM technique.The effect of unbalanced filter inductance and of parasitic capacitance on the combined CD-Boost bipolar SPWM H-Bridge converter system was investigated. Simulation and experiment results verified the proposed converter’s feasibility in addressing issues of transformerless DC/AC converters in grid-connected PV systems.

Design of the Three-Phase Photovoltaic Grid-Connected Inverter

Photovoltaic grid-connected power generation is the inevitable development trend of solar photovoltaic systems,grid inverter is an essential part of photovoltaic grid-connected power generation. With the developed three phase current type PWM inverter device as the research object, and symmetry rules sampling method is applied to the inverter, through the method combined by the computer simulation and experiment research, the device was verified by simulation and experimental .The results show that: This method could not only effectively reduce the DC side inductance volume of the current-mode PWM inverter , and it could make output AC currents sinusoidal and in phase with grid voltages, but also improve the efficiency of the system, it will be more suitable for photovoltaic grid-connected.

Photovoltaic Grid-Connected Generation Gnalog Device Gesign

With the reduction of non-renewable energy resources, energy conservation and development of new energy has become an important strategic plan around the world. Photovoltaic technology is also developing rapidly with more and more applications of solar energy. The project designed a set of solar photovoltaic grid-connected power generation analog devices. In this paper, the maximum power point tracking, DC-AC inverter technology, SPWM control technology related to single-phase grid-connected PV system have been studied, a comprehensive theoretical has been analyzed and to develop the relevant control scheme and design a set of simulator based on MSP430F169 microcontroller. The experimental results have met the target and achieved the desired effect.

Climate and land-use change impacts on potential solar photovoltaic power generation in the Black Sea region

• The solar resource is sufficient to provide PV power at suitable locations within the Black Sea catchment. • Climate change will not significantly impact the solar resource, although uncertainty exists. • Land-use change will significantly impact potential PV power, although socio-economic factors will have more importance. • It is important to strengthen regional cooperation for the integration of renewable energy resources. Climate change is a naturally occurring phenomenon that has recently been greatly impacted by anthropogenic greenhouse gas (GHG) emissions. One of the main contributing sectors to GHG emissions is the energy sector, due to its high dependency on fossil fuels. Renewable energy systems, notably solar energy, can be an effective climate change mitigation alternative. Photovoltaic (PV) technology provides an interesting method to produce electricity through a virtually infinite renewable resource at the human time scale: solar radiation. This study evaluates the current and future solar energy potential through the use of grid-connected PV power plants at the scale of countries within the Black Sea catchment. Simulated data are used to determine potential change in climate and land-use according to two different development scenarios. Incident solar radiation flux from re-analyses, spatial interpolation, and the application of the Delta change method are used to assess the current and future solar resource potential within this catchment. Potential sites suitable for PV power plants are selected following a Fuzzy logic approach, and thus the total potential solar energy through PV power generation can be determined. Results show that climate change will have little impact on the solar radiation resource, while land-use change induces more variability. However, regardless of the scenario followed, the solar energy potential is sufficient to provide an interesting contribution to the electricity generation mix of most countries within the Black Sea region.

Analysis of the Influence of Environment Parameters on Grid-Connected Photovoltaic System

The performance of grid-connected Photovoltaic (PV) power generation system operating in the field is inevitably affected by environmental parameters (solar irradiance, temperature, humidity, wind speed, spectrum, cloud cover, dust, etc.), of which the main factors are solar irradiance and temperature. Based on the data of 100kW PV system of ShangYi PV Plant captured form June 1, 2012 to May 31, 2013 (1 min resolution) and the data of Qinghai Delingha 20MW PV Plant in China captured in 2012., the influence of solar irradiance and temperature on PV system is analyzed. The results show hourly PV array DC power has highly significant positive correlation with hourly total solar radiation, also PV system AC power output and solar irradiance have good consistency. Both of them show irradiance is the main environment factor to the PV system. Then using the captured data, the relationship between maximum load and PV panels surface temperature is also analyzed, the surface temperature is higher, the maximum load is lower.

Grid connected fuel cell and PV hybrid power generating system design with Matlab Simulink

Renewable energy sources have been taken the place of the traditional energy sources and especially rapidly developments of photovoltaic (PV) technology and fuel cell (FC) technology have been put forward these renewable energy sources (RES) in all other RES. PV systems have been started to be used widely in domestic applications connected to electrical grid and grid connected PV power generating systems have become widespread all around the world. On the other hand, fuel cell power generating systems have been used to support the PV generating so hybrid generation systems consist of PV and fuel cell technology are investigated for power generating. In this study, a grid connected fuel cell and PV hybrid power generating system was developed with Matlab Simulink. 160 Wp solar module was developed based on solar module temperature and solar irradiation by using real data sheet of a commercial PV module and then by using these modules 800 Wp PV generator was obtained. Output current and voltage of PV system was used for input of DC/DC boost converter and its output was used for the input of the inverter. PV system was connected to the grid and designed 5 kW solid oxide fuel cell (SOFC) system was used for supporting the DC bus of the hybrid power generating system. All results obtained from the simulated hybrid power system were explained in the paper. Proposed model was designed as modular so designing and simulating grid connected SOFC and PV systems can be developed easily thanks to flexible design.

MW级光伏电站设计研究及探讨

随着化石能源的日趋减少和环境污染的日趋严重，大功率太阳能发电的核心技术成为新能源研究领域的新热点之一。本文主要针对MW级光伏发电系统进行介绍并且提出一种切实可行的设计方案。该方案采用RS485通讯方式的监控装置，对工作环境、运行状态和运行参数进行实时监控，有效避免了孤岛效应、电压和频率异常等安全隐患。为了验证大功率光伏并网发电系统可行性，运用MATLAB/SIMULINK进行了仿真模拟，仿真与实验结果表明，本MW级光伏发电系统的设计方案不仅对MW级光伏电站的建设起到很好的启示和验证作用，而且对光伏发电系统的发展起到了进一步促进作用。本文研究详细，在已有数据基础上，运用MATLAB进行模拟，模拟结果对工程实践具有指导意义。 With the increasing reduction of fossil energy and the serious environmental pollution, the core technology of high-power solar power has become one of the new focuses of energy research. This article mainly aims at introducing the MW-class photovoltaic power generation system and putting forward a feasible design plan. The scheme adopted the monitoring device of RS485 communication mode, monitoring the working environment, operational status and operating parameters in real time, to effectively avoid islanding effect, abnormal voltage and frequency, and other potential risks. In order to verify the feasibility of high-power photovoltaic grid-connected power system, analogue simulation was done using MATLAB/SIMULINK; the simulation and experimental results showed that the MW-class photovoltaic power generation system is not only enlighten and validate the construction of MW-class photovoltaic power station, but also promote the development of photovoltaic power generation system. This paper has studied in detail using MATLAB simulation based on the existing data; the simulation results are of guiding significance for engineering practice.

Spatial viability analysis of grid-connected photovoltaic power systems for Turkey

This paper investigates viability of 0.2, 0.5, 1, 3, 5 and 10MW grid-connected photovoltaic (PV) power plants using 22-year data for 135 locations across Turkey and RETScreen model to predict energy production. Mean annual global solar radiation (GSR), sunshine duration (SSD), and ambient air temperature (Tair) were spatially interpolated over Turkey based on universal kriging method. The technical renewable energy potential of grid-connected solar PV in Turkey estimated for a 0.2–10MW power plant, on average, ranged from 0.31 to 15.56GWhm−2yr−1 for a fixed system, and from 0.41 to 20.81GWhm−2yr−1 for a dual-axis tracker in direct alignment with the sun. The use of the proposed PV grid-connected power plants was found to provide the highest energy production in Osmaniye, Dalaman, and Koycegiz and the lowest energy production in Tosya, Gumushane, and Artvin.

The Study and Design of 20kW Photovoltaic Power System

This paper firstly analysis the principle of three-phased photovoltaic grid-connected power system. Secondly, the 20KW photovoltaic power system will be given as an example to introduce the design strategy of photovoltaic modules. Also, the photovoltaic grid-connected inverter is designed, which includes its parameters calculation and components selection. Finally, the whole photovoltaic power system is designed and verified via the experiment. The result of the experiment shows the design is reasonable and reliable. The power system can achieve full power operation and satisfy its expected goal.

Control Method of Inverter for Large-Scale Grid-Connected Photovoltaic Generation System

A grid-connected inverter control method to analyze dynamic process of large-scale and grid-connected photovoltaic (PV) power station is proposed. The reference values of control variables are composed of maximum power output of the photovoltaic array in the photovoltaic power plant and power factor specified by dispatching. Control strategy of dynamic feedback linearization is adopted. Nonlinear decoupling controller is designed for realizing decoupling control of real-and reactive-power. The cascade PI regulation is proposed to avoid inaccurate parameter estimation which generates the system static error. Simulation is carried out based on the simplified power system with large-scale photovoltaic plant model, the power factor, and solar irradiation, and bus fault are considered for the further research. Its demonstrated that the parameter adjustment of PI controller is simple and convenient, dynamic response of system is transient, and the stability of the inverter control is verified.

DESIGN AND ANALYSIS OF A GRID-CONNECTED PHOTOVOLTAIC POWER SYSTEM

A grid-connected photovoltaic (PV) power system with high voltage gain is proposed, and the steady-state model analysis and the control strategy of the system are presented in this paper. For a typical PV array, the output voltage is relatively low, and a high voltage gain is obligatory to realize the grid-connected function. The proposed PV system employs a ZVT-interleaved boost converter with winding-coupled inductors and active-clamp circuits as the first power-processing stage, which can boost a low voltage of the PV array up to a high dc-bus voltage. Two compensation units are added to perform in the system control loops to achieve the low total harmonic distortion and fast dynamic response of the output current. Furthermore, a simple maximum-power-point-tracking method based on power balance is applied in the PV system to reduce the system complexity and cost with a high performance. At last, a 2-kW prototype has been built and tested to verify the theoretical analysis of the paper.

Transformerless Inverter With Virtual DC Bus Concept for Cost-Effective Grid-Connected PV Power Systems

In order to eliminate the common-mode (CM) leakage current in the transformerless photovoltaic (PV) systems, the concept of the virtual dc bus is proposed in this paper. By connecting the grid neutral line directly to the negative pole of the dc bus, the stray capacitance between the PV panels and the ground is bypassed. As a result, the CM ground leakage current can be suppressed completely. Meanwhile, the virtual dc bus is created to provide the negative voltage level for the negative ac grid current generation. Consequently, the required dc bus voltage is still the same as that of the full-bridge inverter. Based on this concept, a novel transformerless inverter topology is derived, in which the virtual dc bus is realized with the switched capacitor technology. It consists of only five power switches, two capacitors, and a single filter inductor. Therefore, the power electronics cost can be curtailed. This advanced topology can be modulated with the unipolar sinusoidal pulse width modulation (SPWM) and the double frequency SPWM to reduce the output current ripple. As a result, a smaller filter inductor can be used to reduce the size and magnetic losses. The advantageous circuit performances of the proposed transformerless topology are analyzed in detail, with the results verified by a 500-W prototype.

Research on Control Method of Inverters for Large-scale Grid Connected Photovoltaic Power System

A grid-connected inverter controlling method to analyze dynamic process of large-scale and grid-connected photovoltaic power station is proposed. The reference values of control variables are composed of maximum power which is the output of the photovoltaic array of the photovoltaic power plant, and power factor specified by dispatching, the control strategy of dynamic feedback linearization is adopted. Nonlinear decoupling controller is designed for realizing decoupling control of active and reactive power. The cascade PI regulation is proposed to avoid inaccurate parameter estimation which generates the system static error. Simulation is carried out based on the simplified power system with large-scale photovoltaic plant modelling, and the power factor, solar radiation strength, and bus fault are considered for the further research. It’s demonstrated that the parameter adjustment of PI controller is simple and convenient, dynamic response of system is transient, and the stability of the inverter control is verified.

A Review of Islanding Detection Method of Grid-Connected PV Power System

With the increasing of the capacity of grid-connected photovoltaic (PV) power system, islanding detection becomes more prominent and significant. At present, islanding detection methods used in grid-connected photovoltaic system can be divided into passive detection methods and active detection methods these two categories, which can also be divided into a variety of methods. This paper shows a comprehensive review of islanding detection methods, classifies the methods of islanding detection, analyzes the principles and characteristics of various islanding detection methods, indicates their appropriate situations, and pointes out the prospect of islanding detection methods. In practical applications, according to the actual situation, selects one or more islanding detection methods can attain better detection effect.