Showing papers on "Electricity generation published in 2008"
TL;DR: In this article, the authors analyse the impact of renewable electricity generation on the electricity market in Germany and show that the financial volume of the price reduction is considerable, which gives rise to a distributional effect which creates savings for the demand side by reducing generator profits.
910 citations
TL;DR: In this article, a security-constrained unit commitment (SCUC) algorithm is proposed for managing the security of power system operation by taking into account the intermittency and volatility of wind power generation.
Abstract: This paper presents a security-constrained unit commitment (SCUC) algorithm which takes into account the intermittency and volatility of wind power generation. The UC problem is solved in the master problem with the forecasted intermittent wind power generation. Next, possible scenarios are simulated for representing the wind power volatility. The initial dispatch is checked in the subproblem and generation redispatch is considered for satisfying the hourly volatility of wind power in simulated scenarios. If the redispatch fails to mitigate violations, Benders cuts are created and added to the master problem to revise the commitment solution. The iterative process between the commitment problem and the feasibility check subproblem will continue until simulated wind power scenarios can be accommodated by redispatch. Numerical simulations indicate the effectiveness of the proposed SCUC algorithm for managing the security of power system operation by taking into account the intermittency and volatility of wind power generation.
869 citations
TL;DR: An optimal sizing method was developed to calculate the optimum system configuration that can achieve the customers required loss of power supply probability (LPSP) with a minimum annualized cost of system (ACS).
841 citations
TL;DR: In this paper, the authors describe methodologies to model hybrid renewable energy systems (HRES) components, HRES designs and their evaluation and highlight the issues related to penetration of these energy systems in the present distribution network.
Abstract: Hybrid renewable energy systems (HRES) are becoming popular for remote area power generation applications due to advances in renewable energy technologies and subsequent rise in prices of petroleum products. Economic aspects of these technologies are sufficiently promising to include them in developing power generation capacity for developing countries. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The paper describes methodologies to model HRES components, HRES designs and their evaluation. The trends in HRES design show that the hybrid PV/wind energy systems are becoming gaining popular. The issues related to penetration of these energy systems in the present distribution network are highlighted.
775 citations
TL;DR: In this paper, an AC-linked hybrid wind/photovoltaic (PV)/fuel cell alternative energy system for stand-alone applications is proposed, where wind and PV are the primary power sources of the system, and an FC-electrolyzer combination is used as a backup and a long-term storage system.
Abstract: This paper proposes an AC-linked hybrid wind/photovoltaic (PV)/fuel cell (FC) alternative energy system for stand-alone applications. Wind and PV are the primary power sources of the system, and an FC-electrolyzer combination is used as a backup and a long-term storage system. An overall power management strategy is designed for the proposed system to manage power flows among the different energy sources and the storage unit in the system. A simulation model for the hybrid energy system has been developed using MATLAB/Simulink. The system performance under different scenarios has been verified by carrying out simulation studies using a practical load demand profile and real weather data.
722 citations
TL;DR: A biomechanical energy harvester that generates electricity during human walking with little extra effort that is well-suited for charging powered prosthetic limbs and other portable medical devices.
Abstract: We have developed a biomechanical energy harvester that generates electricity during human walking with little extra effort. Unlike conventional human-powered generators that use positive muscle work, our technology assists muscles in performing negative work, analogous to regenerative braking in hybrid cars, where energy normally dissipated during braking drives a generator instead. The energy harvester mounts at the knee and selectively engages power generation at the end of the swing phase, thus assisting deceleration of the joint. Test subjects walking with one device on each leg produced an average of 5 watts of electricity, which is about 10 times that of shoe-mounted devices. The cost of harvesting-the additional metabolic power required to produce 1 watt of electricity-is less than one-eighth of that for conventional human power generation. Producing substantial electricity with little extra effort makes this method well-suited for charging powered prosthetic limbs and other portable medical devices.
692 citations
TL;DR: In this article, the authors investigated the combined optimization of a wind farm and a pumped-storage facility from the point of view of a generation company in a market environment, and formulated the optimization model as a two-stage stochastic programming problem with two random parameters: market prices and wind generation.
Abstract: One of the main characteristics of wind power is the inherent variability and unpredictability of the generation source, even in the short-term. To cope with this drawback, hydro pumped-storage units have been proposed in the literature as a good complement to wind generation due to their ability to manage positive and negative energy imbalances over time. This paper investigates the combined optimization of a wind farm and a pumped-storage facility from the point of view of a generation company in a market environment. The optimization model is formulated as a two-stage stochastic programming problem with two random parameters: market prices and wind generation. The optimal bids for the day-ahead spot market are the ldquohere and nowrdquo decisions while the optimal operation of the facilities are the recourse variables. A joint configuration is modeled and compared with an uncoordinated operation. A realistic example case is presented where the developed models are tested with satisfactory results.
674 citations
TL;DR: In this paper, the authors presented small-signal stability analyzed results of an autonomous hybrid renewable energy power generation/energy storage system connected to isolated loads using time-domain simulations.
Abstract: Small-signal stability analyzed results of an autonomous hybrid renewable energy power generation/energy storage system connected to isolated loads using time-domain simulations is presented in this paper. The companion paper presents frequency-domain analyzed results of the same hybrid system. The proposed renewable energy power generation subsystems include three wind turbine generators (WTGs), a diesel engine generator, two fuel cells (FCs), and a photovoltaic system (PV) while the energy storage subsystems consist of a battery energy storage system and a flywheel energy storage system. An aqua electrolyzer absorbs a part of generated energy from PV or WTGs to generate available hydrogen for FCs. A time-domain approach based on three mathematical models for three studied cases under various operating points and disturbance conditions is performed. It can be concluded from the simulation results that the proposed hybrid power generation/energy storage system feeding isolated loads can be properly operated to achieve system power-frequency balance condition.
672 citations
TL;DR: Life cycle GHG emissions from PHEVs are assessed and it is found that they reduceGHG emissions by 32% compared to conventional vehicles, but have small reductions compared to traditional hybrids.
Abstract: Plug-in hybrid electric vehicles (PHEVs), which use electricity from the grid to power a portion of travel, could play a role in reducing greenhouse gas (GHG) emissions from the transport sector. However, meaningful GHG emissions reductions with PHEVs are conditional on low-carbon electricity sources. We assess life cycle GHG emissions from PHEVs and find that they reduce GHG emissions by 32% compared to conventional vehicles, but have small reductions compared to traditional hybrids. Batteries are an important component of PHEVs, and GHGs associated with lithium-ion battery materials and production account for 2–5% of life cycle emissions from PHEVs. We consider cellulosic ethanol use and various carbon intensities of electricity. The reduced liquid fuel requirements of PHEVs could leverage limited cellulosic ethanol resources. Electricity generation infrastructure is long-lived, and technology decisions within the next decade about electricity supplies in the power sector will affect the potential for l...
650 citations
TL;DR: In this paper, a short-term forward electricity market-clearing problem with stochastic security is formulated to account for variable wind power generation sources, which allows greater wind power penetration without sacrificing security.
Abstract: In their attempt to cut down on greenhouse gas emissions from electricity generation, several countries are committed to install wind power generation up to and beyond the 10%-20% penetration mark. However, the large-scale integration of wind power represents a challenge for power system operations planning because wind power 1) cannot be dispatched in the classical sense; and 2) its output varies as weather conditions change. This warrants the investigation of alternative short-term power system operations planning methods capable of better coping with the nature of wind generation while maintaining or even improving the current reliability and economic performance of power systems. To this end, this paper formulates a short-term forward electricity market-clearing problem with stochastic security capable of accounting for nondispatchable and variable wind power generation sources. The principal benefit of this stochastic operation planning approach is that, when compared to a deterministic worst-case scenario planning philosophy, it allows greater wind power penetration without sacrificing security.
649 citations
20 Jul 2008
TL;DR: In this paper, the authors proposed to add virtual rotational inertia to the distributed generators to stabilize the grid frequency by adding a short-term energy storage to the generator, combined with a suitable control mechanism for its power electronics converter.
Abstract: In electricity grids the frequency of the voltage is stabilized by a combination of the rotational inertia (rotating mass) of synchronous power generators in the grid and a control algorithm acting on the rotational speed of a number of major synchronous power generators When in future small non-synchronous generation units replace a significant part of the synchronous power generation capacity, the total rotational inertia of the synchronous generators is decreased significantly This causes large frequency variations that can end up in an unstable grid A way to stabilize the grid frequency is to add virtual rotational inertia to the distributed generators A virtual inertia can be attained for any generator by adding a short-term energy storage to it, combined with a suitable control mechanism for its power electronics converter In this way a generator can behave like a ldquoVirtual Synchronous Generatorrdquo (VSG) during short time intervals, and contribute to stabilization of the grid frequency
20 Jul 2008
TL;DR: A short-term forward electricity market-clearing problem with stochastic security capable of accounting for non-dispatchable and variable wind power generation sources is formulates and allows greater wind power penetration without sacrificing security.
Abstract: In their attempt to cut down on greenhouse gas emissions from electricity generation, several countries are committed to install wind power generation up to and beyond the 10-20% penetration mark. However, the large-scale integration of wind power represents a challenge for power system operations planning because wind power (i) cannot be dispatched in the classical sense; and, (ii) its output varies as weather conditions change. This warrants the investigation of alternative short-term power system operations planning methods capable of better coping with the nature of wind generation while maintaining or even improving the current reliability and economic performance of power systems. To this end, this paper formulates a short-term forward electricity market-clearing problem with stochastic security capable of accounting for non-dispatchable and variable wind power generation sources. The principal benefit of this stochastic operation planning approach is that, when compared to a deterministic worst-case scenario planning philosophy, it allows greater wind power penetration without sacrificing security.
TL;DR: In this article, the authors present the key scientific advances required in order to successfully develop energy-storage technologies generally represent realistic goals that may be achieved by 2050, given the appropriate research effort, the main barriers to overcome with regard to the development of SMES technology are those related to high-temperature superconductors.
TL;DR: Overall, all PV technologies generate far less life-cycle air emissions per GWh than conventional fossil-fuel-based electricity generation technologies.
Abstract: Photovoltaic (PV) technologies have shown remarkable progress recently in terms of annual production capacity and life cycle environmental performances, which necessitate timely updates of environmental indicators. Based on PV production data of 2004-2006, this study presents the life-cycle greenhouse gas emissions, criteria pollutant emissions, and heavy metal emissions from four types of major commercial PV systems: multicrystalline silicon, monocrystalline silicon, ribbon silicon, and thin-film cadmium telluride. Life-cycle emissions were determined by employing average electricity mixtures in Europe and the United States during the materials and module production for each PV system. Among the current vintage of PV technologies, thin-film cadmium telluride (CdTe) PV emits the least amount of harmful air emissions as it requires the least amount of energy during the module production. However, the differences in the emissions between different PV technologies are very small in comparison to the emissions from conventional energy technologies that PV could displace. As a part of prospective analysis, the effect of PV breeder was investigated. Overall, all PV technologies generate far less life-cycle air emissions per GWh than conventional fossil-fuel-based electricity generation technologies. At least 89% of air emissions associated with electricity generation could be prevented if electricity from photovoltaics displaces electricity from the grid.
TL;DR: A power generator array based on thick-film piezoelectric cantilevers is investigated to improve frequency flexibility and power output and is promising to support networks of ultra-low-power, peer-to-peer, wireless nodes.
TL;DR: This paper presents power-control strategies of a grid-connected hybrid generation system with versatile power transfer, the combination of photovoltaic array, wind turbine, and battery storage via a common dc bus, and its control system.
Abstract: This paper presents power-control strategies of a grid-connected hybrid generation system with versatile power transfer. The hybrid system is the combination of photovoltaic (PV) array, wind turbine, and battery storage via a common dc bus. Versatile power transfer was defined as multimodes of operation, including normal operation without use of battery, power dispatching, and power averaging, which enables grid- or user-friendly operation. A supervisory control regulates power generation of the individual components so as to enable the hybrid system to operate in the proposed modes of operation. The concept and principle of the hybrid system and its control were described. A simple technique using a low-pass filter was introduced for power averaging. A modified hysteresis-control strategy was applied in the battery converter. Modeling and simulations were based on an electromagnetic-transient-analysis program. A 30-kW hybrid inverter and its control system were developed. The simulation and experimental results were presented to evaluate the dynamic performance of the hybrid system under the proposed modes of operation.
TL;DR: In this paper, the authors empirically analyzed the social benefits provided by electricity from renewable energy sources (RES-E), including environmental and socioeconomic ones, and showed that the reduction in the wholesale price of electricity as a result of more RES-E generation being fed into the grid is greater than the increase in the costs for the consumers arising from the RESE support scheme (the feed-in tariffs).
TL;DR: In this paper, the optimal control of distribution voltage with coordination of distributed installations, such as the load ratio control transformer, step voltage regulator (SVR), shunt capacitor, shunt reactor, and static var compensator, is proposed.
Abstract: In recent years, distributed generation, as clean natural energy generation and cogeneration system of high thermal efficiency, has increased due to the problems of global warming and exhaustion of fossil fuels. Many of the distributed generations are set up in the vicinity of the customer, with the advantage that this decreases transmission losses. However, output power generated from natural energy, such as wind power, photovoltaics, etc., which is distributed generation, is influenced by meteorological conditions. Therefore, when the distributed generation increases by conventional control techniques, it is expected that the voltage change of each node becomes a problem. Proposed in this paper is the optimal control of distribution voltage with coordination of distributed installations, such as the load ratio control transformer, step voltage regulator (SVR), shunt capacitor, shunt reactor, and static var compensator. In this research, SVR is assumed to be a model with tap changing where the signal is received from a central control unit. Moreover, the communication infrastructure in the supply of a distribution system is assumed to be widespread. The genetic algorithm is used to determine the operation of this control. In order to confirm the validity of the proposed method, simulations are carried out for a distribution network model with distributed generation (photovoltaic generation).
TL;DR: In this paper, a method for placement of distributed generation (DG) units in distribution networks has been presented based on the analysis of power flow continuation and determination of most sensitive buses to voltage collapse.
Abstract: In this paper, a method for placement of distributed generation (DG) units in distribution networks has been presented. This method is based on the analysis of power flow continuation and determination of most sensitive buses to voltage collapse. This method is executed on a typical 34-bus test system and yields efficiency in improvement of voltage profile and reduction of power losses; it also may permit an increase in power transfer capacity, maximum loading, and voltage stability margin.
TL;DR: It is demonstrated that when PV array- inverters are operating in the master mode in stand-alone applications, they well perform the task of controlling the voltage and frequency of the power system and that PV power generators constitute a valuable energy source.
Abstract: A substantial increase of photovoltaic (PV) power generators installations has taken place in recent years, due to the increasing efficiency of solar cells as well as the improvements of manufacturing technology of solar panels. These generators are both grid-connected and stand-alone applications. We present an overview of the essential research results. The paper concentrates on the operation and modeling of stand-alone power systems with PV power generators. Systems with PV array-inverter assemblies, operating in the slave-and-master modes, are discussed, and the simulation results obtained using a renewable energy power system modular simulator are presented. These results demonstrate that simulation is an essential step in the system development process and that PV power generators constitute a valuable energy source. They have the ability to balance the energy and supply good power quality. It is demonstrated that when PV array- inverters are operating in the master mode in stand-alone applications, they well perform the task of controlling the voltage and frequency of the power system. The mechanism of switching the master function between the diesel generator and the PV array-inverter assembly in a stand-alone power system is also proposed and analyzed. Finally, some experimental results on a practical system are compared to the simulation results and confirm the usefulness of the proposed approach to the development of renewable energy systems with PV power generators.
TL;DR: In this special feature, Nature's News team looks at how much carbon-free energy might ultimately be available - and which sources make most sense.
Abstract: Electricity generation provides 18,000 terawatt-hours of energy a year, around 40% of humanity's total energy use. In doing so it produces more than 10 gigatonnes of carbon dioxide every year, the largest sectoral contribution of humanity's fossil-fuel derived emissions. Yet there is a wide range of technologies - from solar and wind to nuclear and geothermal - that can generate electricity without net carbon emissions from fuel. The easiest way to cut the carbon released by electricity generation is to increase efficiency. But there are limits to such gains, and there is the familiar paradox that greater efficiency can lead to greater consumption. So a global response to climate change must involve a move to carbon-free sources of electricity. This requires fresh thinking about the price of carbon, and in some cases new technologies; it also means new transmission systems and smarter grids. But above all, the various sources of carbon-free generation need to be scaled up to power an increasingly demanding world. In this special feature, Nature's News team looks at how much carbon-free energy might ultimately be available - and which sources make most sense.
TL;DR: In this paper, a sliding mode control strategy is proposed to ensure stability in both operation regions and to impose the ideal feedback control solution despite model uncertainties in variable-speed wind energy conversion systems (VS-WECS).
Abstract: This paper addresses the problem of controlling power generation in variable-speed wind energy conversion systems (VS-WECS). These systems have two operation regions depending on the wind turbine tip-speed ratio. They are distinguished by minimum phase behavior in one of these regions and a nonminimum phase in the other one. A sliding mode control strategy is then proposed to ensure stability in both operation regions and to impose the ideal feedback control solution despite model uncertainties. The proposed sliding mode control strategy presents attractive features such as robustness to parametric uncertainties of the turbine and the generator as well as to electric grid disturbances. The proposed sliding mode control approach has been simulated on a 1.5-MW three-blade wind turbine to evaluate its consistency and performance. The next step was the validation using the National Renewable Energy Laboratory (NREL) wind turbine simulator called the fatigue, aerodynamics, structures, and turbulence code (FAST). Both simulation and validation results show that the proposed control strategy is effective in terms of power regulation. Moreover, the sliding mode approach is arranged so as to produce no chattering in the generated torque that could lead to increased mechanical stress because of strong torque variations.
Book•
01 Jan 2008
TL;DR: In this paper, the authors present an analysis of the impact of renewable energy generation on the frequency control and reliability of large-scale power systems, as well as the number of faults and failures.
Abstract: Foreword . Preface . Acknowledgements . 1 Energy and Electricity . 1.1 The World Energy Scene. 1.2 The Environmental Impact of Energy Use. 1.3 Generating Electricity. 1.4 The Electrical Power System. References. 2 Features of Conventional and Renewable Generation . 2.1 Introduction. 2.2 Conventional Sources: Coal, Gas and Nuclear. 2.3 Hydroelectric Power. 2.4 Wind Power. 2.5 PV and Solar Thermal Electricity. 2.6 Tidal Power. 2.7 Wave Power. 2.8 Biomass. 2.9 Summary of Power Generation Characteristics. 2.10 Combining Sources. References. 3 Power Balance/ Frequency Control . 3.1 Introduction. 3.2 Electricity Demand. 3.3 Power Governing. 3.4 Dynamic Frequency Control of Large Systems. 3.5 Impact of Renewable Generation on Frequency Control and Reliability. 3.6 Frequency Response Services from Renewables. 3.7 Frequency Control Modelling. 3.8 Energy Storage. References. Other Useful Reading. 4 Electrical Power Generation and Conditioning . 4.1 The Conversion of Renewable Energy into Electrical Form. 4.2 The Synchronous Generator. 4.3 The Transformer. 4.4 The Asynchronous Generator. 4.5 Power Electronics. 4.6 Applications to Renewable Energy Generators. References. 5 Power System Analysis . 5.1 Introduction. 5.2 The Transmission System. 5.3 Voltage Control. 5.4 Power Flow in an Individual Section of Line. 5.5 Reactive Power Management. 5.6 Load Flow and Power System Simulation. 5.7 Faults and Protection. 5.8 Time Varying and Dynamic Simulations. 5.9 Reliability Analysis. References. 6 Renewable Energy Generation in Power Systems . 6.1 Distributed Generation. 6.2 Voltage Effects. 6.3 Thermal Limits. 6.4 Other Embedded Generation Issues. 6.5 Islanding. 6.6 Fault Ride-through. 6.7 Generator and Converter Characteristics. References. 7 Power System Economics and the Electricity Market . 7.1 Introduction. 7.2 The Costs of Electricity Generation. 7.3 Economic Optimization in Power Systems. 7.4 External Costs. 7.5 Effects of Embedded Generation. 7.6 Support Mechanisms for Renewable Energy. 7.7 Electricity Trading. References. 8 The Future - Towards a Sustainable Electricity Supply System . 8.1 Introduction. 8.2 The Future of Wind Power. 8.3 The Future of Solar Power. 8.4 The Future of Biofuels. 8.5 The Future of Hydro and Marine Power. 8.6 Distributed Generation and the Shape of Future Networks. 8.7 Conclusions. References. Appendix: Basic Electric Power Engineering Concepts . A.1 Introduction. A.2 Generators and Consumers of Energy. A.3 Why AC?. A.4 AC Waveforms. A.5 Response of Circuit Components to AC. A.6 Phasors. A.7 Phasor Addition. A.8 Rectangular Notation. A.9 Reactance and Impedance. A.10 Power in AC Circuits. A.11 Reactive Power. A.12 Complex Power. A.13 Conservation of Active and Reactive Power. A.14 Effects of Reactive Power Flow - Power Factor Correction. A.15 Three-phase AC. A.16 The Thevenin Equivalent Circuit. Reference. Index.
TL;DR: In this article, the main technical challenges associated with the integration of wind power into power systems are discussed, including effects of wind energy on the power system, the power systems operating cost, power quality, power imbalances, power system dynamics, and impacts on transmission planning.
Abstract: Wind power is going through a very rapid development. It is among the fastest growing power sources in the world, the technology is being developed rapidly and wind power is supplying significant shares of the energy in large regions. The integration of wind power in the power system is now an issue in order to optimize the utilization of the resource and to continue the high rate of installation of wind generating capacity, which is necessary so as to achieve the goals of sustainability and security of supply. This paper presents the main technical challenges that are associated with the integration of wind power into power systems. These challenges include effects of wind power on the power system, the power system operating cost, power quality, power imbalances, power system dynamics, and impacts on transmission planning. The main conclusion is that wind power's impacts on system operating costs are small at low wind penetrations (about 5% or less). At higher wind penetrations, the impact will be higher, although current results suggest the impact remains moderate with penetrations approaching 20%. In addition, the paper presents the technology and expectations of wind forecasting as well as cases where wind power curtailment could arise. Future research directions for a better understanding of the factors influencing the increased integration of wind power into power systems are also provided.
TL;DR: In this paper, the authors presented an optimization approach to choose such systems and their operating schedules using Berkeley Lab's Distributed Energy Resources Customer Adoption Model (DER-CAM), extended to incorporate electrical and thermal storage options.
Abstract: The deployment of small ( < 1-2 MW ) clusters of generators, heat and electrical storage, efficiency investments, and combined heat and power (CHP) applications (particularly involving heat-activated cooling) in commercial buildings promises significant benefits but poses many technical and financial challenges, both in system choice and its operation; if successful, such systems may be precursors to widespread microgrid deployment. The presented optimization approach to choosing such systems and their operating schedules uses Berkeley Lab's Distributed Energy Resources Customer Adoption Model (DER-CAM), extended to incorporate electrical and thermal storage options. DER-CAM chooses annual energy bill minimizing systems in a fully technology-neutral manner. An illustrative example for a hypothetical San Francisco hotel is reported. The chosen system includes one large reciprocating engine and an absorption chiller providing an estimated 11% cost savings and 8% carbon emission reductions under idealized circumstances.
TL;DR: In this article, an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations, is presented. But the proposed generator cannot generate enough energy for proper operation.
Abstract: This paper presents an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations. For most wireless applications, the ambient vibration is generally at very low frequencies (1-100 Hz), and traditional scavenging techniques cannot generate enough energy for proper operation. The reported generator up-converts low-frequency environmental vibrations to a higher frequency through a mechanical frequency up-converter using a magnet, and hence provides more efficient energy conversion at low frequencies. Power is generated by means of EM induction using a magnet and coils on top of resonating cantilever beams. The proposed approach has been demonstrated using a macroscale version, which provides 170 nW maximum power and 6 mV maximum voltage. For the microelectromechanical systems (MEMS) version, the expected maximum power and maximum voltage from a single cantilever is 3.97 muW and 76 mV, respectively, in vacuum. Power level can be increased further by using series-connected cantilevers without increasing the overall generator area, which is 4 mm2. This system provides more than an order of magnitude better energy conversion for 10-100 Hz ambient vibration range, compared to a conventional large mass/coil system.
TL;DR: This paper presents the analysis, design, and implementation of a parallel connected maximum power point tracking (MPPT) system for stand-alone photovoltaic power generation and presents the functions of battery charger and step-up converter.
Abstract: This paper presents the analysis, design, and implementation of a parallel connected maximum power point tracking (MPPT) system for stand-alone photovoltaic power generation. The parallel connection of the MPPT system reduces the negative influence of power converter losses in the overall efficiency because only a part of the generated power is processed by the MPPT system. Furthermore, all control algorithms used in the classical series-connected MPPT can be applied to the parallel system. A simple bidirectional dc-dc power converter is proposed for the MPPT implementation and presents the functions of battery charger and step-up converter. The operation characteristics of the proposed circuit are analyzed with the implementation of a prototype in a practical application.
TL;DR: In this paper, the authors proposed a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs), where the aerodynamic characteristics of the wind turbine were approximated by a Gaussian radial basis function network based nonlinear input-output mapping.
Abstract: This paper proposes a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs). A specific design of the proposed control algorithm for a wind turbine equipped with a doubly fed induction generator (DFIG) is presented. The aerodynamic characteristics of the wind turbine are approximated by a Gaussian radial basis function network based nonlinear input-output mapping. Based on this nonlinear mapping, the wind speed is estimated from the measured generator electrical output power while taking into account the power losses in the WTG and the dynamics of the WTG shaft system. The estimated wind speed is then used to determine the optimal DFIG rotor speed command for maximum wind power extraction. The DFIG speed controller is suitably designed to effectively damp the low-frequency torsional oscillations. The resulting WTG system delivers maximum electrical power to the grid with high efficiency and high reliability without mechanical anemometers. The validity of the proposed control algorithm is verified by simulation studies on a 3.6MW WTG system. In addition, the effectiveness of the proposed wind speed estimation algorithm is demonstrated by experimental studies on a small emulational WTG system.
TL;DR: In this article, the frequency response capability of the full converter variable speed wind turbine generator (FCWTG) with permanent magnet synchronous generator (PMSG) is investigated and a control scheme is developed that improves the frequency control performance.
Abstract: With an increased number of wind turbine generators (WTGs) connected to an electricity network the system operator may request that they participate in frequency control in the event of a sudden unbalancing of power generated and consumed on the system. In this paper the frequency response capability of the full converter variable speed wind turbine generator (FCWTG) with permanent magnet synchronous generator (PMSG) is investigated. A control scheme is developed that improves the frequency control performance, illustrating the importance of the initial active power output of the FCWTG. A method of carefully ending the frequency support of a wind farm is proposed and simulated. The resulting frequency control performance compares favorably to that of a conventional synchronous generator plant.
TL;DR: In this article, the authors presented the results of a life cycle assessment (LCA) of the electric generation by means of photovoltaic panels, considering mass and energy flows over the whole production process starting from silica extraction to the final panel assembling, considering the most advanced and consolidate technologies for polycrystalline silicon panel production.