Showing papers on "Grid-connected photovoltaic power system published in 2010"

Grid-connected photovoltaic power systems: Technical and potential problems—A review

Abstract: Traditional electric power systems are designed in large part to utilize large baseload power plants, with limited ability to rapidly ramp output or reduce output below a certain level. The increase in demand variability created by intermittent sources such as photovoltaic (PV) presents new challenges to increase system flexibility. This paper aims to investigate and emphasize the importance of the grid-connected PV system regarding the intermittent nature of renewable generation, and the characterization of PV generation with regard to grid code compliance. The investigation was conducted to critically review the literature on expected potential problems associated with high penetration levels and islanding prevention methods of grid tied PV. According to the survey, PV grid connection inverters have fairly good performance. They have high conversion efficiency and power factor exceeding 90% for wide operating range, while maintaining current harmonics THD less than 5%. Numerous large-scale projects are currently being commissioned, with more planned for the near future. Prices of both PV and balance of system components (BOS) are decreasing which will lead to further increase in use. The technical requirements from the utility power system side need to be satisfied to ensure the safety of the PV installer and the reliability of the utility grid. Identifying the technical requirements for grid interconnection and solving the interconnect problems such as islanding detection, harmonic distortion requirements and electromagnetic interference are therefore very important issues for widespread application of PV systems. The control circuit also provides sufficient control and protection functions like maximum power tracking, inverter current control and power factor control. Reliability, life span and maintenance needs should be certified through the long-term operation of PV system. Further reduction of cost, size and weight is required for more utilization of PV systems. Using PV inverters with a variable power factor at high penetration levels may increase the number of balanced conditions and subsequently increase the probability of islanding. It is strongly recommended that PV inverters should be operated at unity power factor.

Design and Analysis of a Grid-Connected Photovoltaic Power System

Abstract: 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. Accordingly, an accurate steady-state model is obtained and verified by the simulation and experimental results, and a full-bridge inverter with bidirectional power flow is used as the second power-processing stage, which can stabilize the dc-bus voltage and shape the output current. 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.

Overview of recent grid codes for wind power integration

Abstract: The challenge to bring down the cost of produced photovoltaic (PV) power had a major impact on the PV market and in consequence the grid operators experienced higher and higher PV power penetration. The growing share of this decentralized generation plants started to affect the grid stability and Distribution System Operators (DSOs) had to keep the safety and reliability of the network under strict rules and regulations. The aim of the paper is to realize a survey of recent Grid Codes (GC) and regulations for grid connected PV systems. The focus is on grid interface requirements, power quality concerns and Anti-Islanding (AI) issues regarding PV systems connected to low voltage (LV) and medium voltage (MV) levels of the network.

Quantifying Rooftop Solar Photovoltaic Potential for Regional Renewable Energy Policy

Abstract: Solar photovoltaic (PV) technology has matured to become a technically viable large-scale source of sustainable energy. Understanding the rooftop PV potential is critical for utility planning, accommodating grid capacity, deploying financing schemes and formulating future adaptive energy policies. This paper merges the capabilities of geographic information systems and object-based image recognition to determine the available rooftop area for PV deployment in an example large-scale region in south eastern Ontario. An innovative five-step procedure has been developed for estimating total rooftop PV potential which involves geographical division of the region; sampling using the Feature Analyst extraction software; extrapolation using roof area-population relationships; reduction for shading, other uses and orientation; and conversion to power and energy outputs. A relationship across the region was found between roof area and population of 70.0 m2/capita ± 6.2%. For this region with appropriate roof tops covered with commercial solar cells the potential PV peak power output is 5.74 GW (157% of the region’s peak power demands) and the potential annual energy production is 6909 Gwh (5% of Ontario’s total annual demand). This suggests that 30% of Ontario’s demand can be met with province-wide rooftop PV deployment. This new understanding of roof area distribution and potential PV outputs has an immense significance to energy policy formulation in Ontario and the methodology developed here is transferable in other regions to assist in solar PV deployment.

A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement

Abstract: Injection of the wind power into an electric grid affects the power quality. The performance of the wind turbine and thereby power quality are determined on the basis of measurements and the norms followed according to the guideline specified in International Electro-technical Commission standard, IEC-61400. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation and these are measured according to national/international guidelines. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. In this proposed scheme STATic COMpensator (STATCOM) is connected at a point of common coupling with a battery energy storage system (BESS) to mitigate the power quality issues. The battery energy storage is integrated to sustain the real power source under fluctuating wind power. The STATCOM control scheme for the grid connected wind energy generation system for power quality improvement is simulated using MATLAB/SIMULINK in power system block set. The effectiveness of the proposed scheme relives the main supply source from the reactive power demand of the load and the induction generator. The development of the grid co-ordination rule and the scheme for improvement in power quality norms as per IEC-standard on the grid has been presented.

Distributed control of reactive power flow in a radial distribution circuit with high photovoltaic penetration

Abstract: We show how distributed control of reactive power can serve to regulate voltage and minimize resistive losses in a distribution circuit that includes a significant level of photovoltaic (PV) generation. To demonstrate the technique, we consider a radial distribution circuit with a single branch consisting of sequentially-arranged residential-scale loads that consume both real and reactive power. In parallel, some loads also have PV generation capability. We postulate that the inverters associated with each PV system are also capable of limited reactive power generation or consumption, and we seek to find the optimal dispatch of each inverter's reactive power to both maintain the voltage within an acceptable range and minimize the resistive losses over the entire circuit. We assume the complex impedance of the distribution circuit links and the instantaneous load and PV generation at each load are known. We compare the results of the optimal dispatch with a suboptimal local scheme that does not require any communication. On our model distribution circuit, we illustrate the feasibility of high levels of PV penetration and a significant (20% or higher) reduction in losses.

Fundamentals of Photovoltaic Modules and their Applications

Abstract: Solar Radiation History of PV integrated systems Solar cell materials and its characteristics PV Array Analysis Role of batteries and its uses Case Studies of PV/T Systems Thermal modeling of hybrid photovoltaic/thermal (PV/T) systems Energy and Exergy Analysis CO2 Mitigation and Carbon Trading Economic Analysis Appendices Glossary Subject Index

An Authenticated Control Framework for Distributed Voltage Support on the Smart Grid

Abstract: Existing and forthcoming devices at the residential level have the ability to provide reactive power support. Inverters which connect distributed generation such as solar panels and pluggable hybrid electric vehicles (PHEVs) to the grid are an example. Such devices are not currently utilized by the power system. We investigate the integration of these end-user reactive-power-capable devices to provide voltage support to the grid via a secure communications infrastructure. We determine effective locations in the transmission system and show how reactive power resources connected at those buses can be controlled. Buses belong to reactive support groups which parallel the regions of the secure communications architecture that is presented. Ultimately, our goal is to present how the smart grid can enable the utilization of available end-user devices as a resource to mitigate power system problems such as voltage collapse.

Local Control of Reactive Power by Distributed Photovoltaic Generators

Abstract: High penetration levels of distributed photovoltaic (PV) generation on an electrical distribution circuit may degrade power quality due to voltage sags and swells caused by rapidly varying PV generation during cloud transients coupled with the slow response of existing utility compensation and regulation equipment Fast-reacting, VAR-capable PV inverters may provide the necessary reactive power injection or consumption to maintain voltage regulation under difficult transient conditions As side benefit, the control of reactive power injection at each PV inverter provides a new tool for distribution utilities to minimize the thermal losses in circuit We suggest a local control scheme that dispatches reactive power from each PV inverter based on local instantaneous measurements of the real and reactive components of the consumed power and the real power generated by the PVs Using one adjustable parameter per circuit, we balance the requirements on power quality and desire to minimize thermal losses The performance of the proposed control scheme is evaluated via numerical simulations of realistic rural lines in several generation/consumption scenarios Simultaneous improvement of both the power quality and the magnitude of losses is observed for all the scenarios, even when the renewable generation in excess of the circuit own load

Analytical modelling of partial shading and different orientation of photovoltaic modules

Abstract: Analytical modelling of a photovoltaic (PV) power system for studying the effects of partial shading and different orientation of PV modules is presented. The proposed analytical model, although limited to the case of series PV modules and composed of complicated non-linear implicit functions, allows several important electrical characteristics of a PV system, such as I - V curve, open-circuit voltage, short-circuit current, maximum power and reverse voltage, to be investigated and presented in two- and three-dimensional graphs to provide in-depth physical interpretation of the issue.

Modeling Smart Grid Applications with Co-Simulation

Abstract: Our analysis of a complex Smart Grid control scheme uses simulation to model both the communication network and the power system. The control scheme uses a wireless communication network to activate distributed storage units in a segment of the electrical grid to compensate for temporary loss of power from a solar photovoltaic (PV) array. Our analytical model of the communication network provides a means to examine the effect of communication failures as a function of the radio frequency (RF) transmission power level. We use these results in an open source event-driven simulator to determine the impact on the electrical power system.

Forecasting power output for grid-connected photovoltaic power system without using solar radiation measurement

Abstract: With the increasing penetration of photovoltaic (PV) power system into the utility network, the issue caused by the fluctuation and intermittence of PV power output draws more attention. In order to predict the hourly power output for a PV system without any complex meteorological instrumentation, a NARX network-based forecasting model is proposed in this paper. Hottel's radiation model is applied to calculate clear-sky radiation incident on any inclined surface at any time. Furthermore, weather forecast data from public websites are taken as the variables that depict the cloud status in future days. By giving enough historical data, the network can be well trained. While forecasting power output, the NARX network can also adjust its weights according to the forecast error. Due to its adaptation to time-varying input, the proposed method can predict PV power output accurately even if the weather changes suddenly. Forecasting results of a roof-top PV power system verify the effectiveness of the proposed model with high precision and high efficiency.

An improved two-diode photovoltaic (PV) model for PV system

Abstract: This paper proposes a MATLAB Simulink simulator for photovoltaic (PV) system. The main contribution of this work is the utilization of the two-diode model to represent the PV cell. This model is known to have better accuracy at low irradiance level which allows for a more accurate prediction of PV system performance. To reduce computational time, the input parameters are reduced to four and the values of Rp and Rs are estimated by an efficient iteration method. Furthermore, all the inputs to the simulator are information available on standard PV module datasheet. The simulator supports large array simulation that can be interfaced with MPPT algorithms and power electronic converters. The accurateness of the simulator is verified by applying the model to two PV modules. It is envisaged that the proposed work can be very useful for PV professionals who require simple, fast and accurate PV simulator to design their systems.

Electricity from Sunlight: An Introduction to Photovoltaics

Abstract: About the Author. Preface. Acknowledgements. 1. Introduction. 1.1 The Sun, Earth, and Renewable Energy. 1.2 The Solar Resource. 1.3 The Magic of Photovoltaics. 1.4 A Piece of History. 1.5 Coming up to Date. References. 2. Solar Cells. 2.1 Setting the Scene. 2.2 Crystalline Silicon. 2.2.1 The Ideal Crystal. 2.2.2 The p n Junction. 2.2.3 Monocrystalline Silicon. 2.2.3.1 Photons in Action. 2.2.3.2 Generating Power. 2.2.3.3 Sunlight, Silicon, and Quantum Mechanics. 2.2.3.4 Refi ning the Design. 2.2.4 Multicrystalline Silicon. 2.3 Amorphous and Thin-fi lm Silicon. 2.4 Other Cells and Materials. 2.4.1 Copper Indium Diselenide (CIS). 2.4.2 Cadmium Telluride (CdTe). 2.4.3 Specialised and Innovative Cells. 2.4.3.1 Gallium Arsenide (GaAs). 2.4.3.2 Dye-sensitised Cells. References. 3. PV Modules and Arrays. 3.1 Introductory. 3.2 Electrical Performance. 3.2.1 Connecting Cells and Modules. 3.2.2 Module Parameters. 3.3 Capturing Sunlight. 3.3.1 Sunshine and Shadow. 3.3.2 Aligning the Array. 3.4 Concentration and Tracking. References. 4. Grid-connected PV Systems. 4.1 Introductory. 4.2 From DC to AC. 4.3 Completing the System. 4.4 Building-integrated Photovoltaics (BIPV). 4.4.1 Engineering and Architecture. 4.4.2 PV Outside, PV Inside. 4.5 Large PV Power Plants. References. 5. Stand-alone PV Systems. 5.1 Remote and Independent. 5.2 System Components. 5.2.1 Batteries. 5.2.2 Charge Controllers. 5.2.3 Inverters. 5.3 Hybrid Systems. 5.4 System Sizing. 5.4.1 Assessing the Problem. 5.4.2 PV Arrays and Battery Banks. 5.5 Applications. 5.5.1 PV in Space. 5.5.2 Island Electricity. 5.5.3 PV Water Pumping. 5.5.4 Solar-powered Boats. 5.5.5 Far and Wide. References. 6. Economics and the Environment. 6.1 Paying for PV. 6.1.1 Costs and Markets. 6.1.2 Financial Incentives. 6.1.3 Rural Electrification. 6.2 Environmental Aspects. 6.2.1 Raw Materials and Land. 6.2.2 Life-cycle Analysis. References. Index.

Evaluation of the voltage support strategies for the low voltage grid connected PV generators

Abstract: Admissible range of grid voltage is one of the strictest constraints for the penetration of distributed photovoltaic (PV) generators especially connection to low voltage (LV) public networks. Voltage limits are usually fulfilled either by network reinforcements or limiting of power injections from PVs. In order to increase PV penetration level further, new voltage support control functions for individual inverters are required. This paper investigates distributed reactive power regulation and active power curtailment strategies regarding the development of PV connection capacity by evaluation of reactive power efforts and requirement of minimum active power curtailment. Furthermore, a small scale experimental setup is built to reflect real grid interaction in the laboratory by achieving critical types of grid (weak and sufficiently stiff).

Recent Developments in Maximum Power Point Tracking Technologies for Photovoltaic Systems

Abstract: In photovoltaic (PV) system applications, it is very important to design a system for operating of the solar cells (SCs) under best conditions and highest efficiency. Maximum power point (MPP) varies depending on the angle of sunlight on the surface of the panel and cell temperature. Hence, the operating point of the load is not always MPP of PV system. Therefore, in order to supply reliable energy to the load, PV systems are designed to include more than the required number of modules. The solution to this problem is that switching power converters are used, that is called maximum power point tracker (MPPT). In this study, the various aspects of these algorithms have been analyzed in detail. Classifications, definitions, and basic equations of the most widely used MPPT technologies are given. Moreover, a comparison was made in the conclusion.

Photovoltaic systems

Abstract: The aim of the present paper is the description of various types of photovoltaic systems, basic calculation and design principles, the scopes of application and their operation investigation. Various types of the PV stations are described in this paper. The basic principles of calculation of the photovoltaic systems, the description of the basic design components of each type and the principles of each component choice are given. The scopes of application of photovoltaic systems are reviewed. The practical applications of PV systems in grid on systems, beacons, telecommunications and street lightings are given in Russia, Poland and Germany. The performances of grid on station in Germany are investigated for four years period. The possibility of low power applications like photographic and video cameras, mobile phones, music players and so on is considered.