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Records Added in February 2019
Records added in February 2019
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Showing records 76 to 100 of 179. [First] Page: 1 2 3 4 5 6 7 8 Last
Ensemble Learning Approach for Probabilistic Forecasting of Solar Power Generation
Azhar Ahmed Mohammed, Zeyar Aung
February 27, 2019 (v1)
Keywords: ensemble models, Machine Learning, probabilistic forecasting, regression, solar power
Probabilistic forecasting accounts for the uncertainty in prediction that arises from inaccurate input data due to measurement errors, as well as the inherent inaccuracy of a prediction model. Because of the variable nature of renewable power generation depending on weather conditions, probabilistic forecasting is well suited to it. For a grid-tied solar farm, it is increasingly important to forecast the solar power generation several hours ahead. In this study, we propose three different methods for ensemble probabilistic forecasting, derived from seven individual machine learning models, to generate 24-h ahead solar power forecasts. We have shown that while all of the individual machine learning models are more accurate than the traditional benchmark models, like autoregressive integrated moving average (ARIMA), the ensemble models offer even more accurate results than any individual machine learning model alone does. Furthermore, it is observed that running separate models on the da... [more]
Forecasting Crude Oil Price Using EEMD and RVM with Adaptive PSO-Based Kernels
Taiyong Li, Min Zhou, Chaoqi Guo, Min Luo, Jiang Wu, Fan Pan, Quanyi Tao, Ting He
February 27, 2019 (v1)
Keywords: crude oil price, energy forecasting, ensemble empirical mode decomposition (EEMD), kernel methods, particle swarm optimization (PSO), relevance vector machine (RVM)
Crude oil, as one of the most important energy sources in the world, plays a crucial role in global economic events. An accurate prediction for crude oil price is an interesting and challenging task for enterprises, governments, investors, and researchers. To cope with this issue, in this paper, we proposed a method integrating ensemble empirical mode decomposition (EEMD), adaptive particle swarm optimization (APSO), and relevance vector machine (RVM)—namely, EEMD-APSO-RVM—to predict crude oil price based on the “decomposition and ensemble” framework. Specifically, the raw time series of crude oil price were firstly decomposed into several intrinsic mode functions (IMFs) and one residue by EEMD. Then, RVM with combined kernels was applied to predict target value for the residue and each IMF individually. To improve the prediction performance of each component, an extended particle swarm optimization (PSO) was utilized to simultaneously optimize the weights and parameters of single kern... [more]
Dynamic Simulation of a Trigeneration Scheme for Domestic Purposes Based on Hybrid Techniques
Luis Acevedo, Javier Uche, Alejandro Del Almo, Fernando Círez, Sergio Usón, Amaya Martínez, Isabel Guedea
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: dynamic simulations, hybrid systems, membrane distillation (MD), photovoltaic/thermal (PVT), reverse osmosis (RO), TRNSYS®, wind turbine (WT)
In this paper, the design of a system providing electricity by coupling photovoltaic/thermal (PVT) collectors and a wind turbine (WT), sanitary hot water (SHW) coming from the PVT and evacuated tube collectors (ETCs) and fresh water (FW) produced in two seawater desalting facilities (membrane distillation, MD, and reverse osmosis, RO), has been carefully analyzed by means of a dynamic model developed in TRNSYS®. This analysis is compulsory to operate a lab-scale pilot plant that is being erected at Zaragoza, Spain. A new model-type has been included in TRNSYS® in order to include the MD unit in the scheme. A sensitivity analysis of some free-design variables, such that the ETC surface, PVT and ETC tilt, water storage tank, batteries capacities, and mass flow rates delivered to the SHW service and/or feeding the MD unit has been performed in order to propose the definite design of the scheme. The proposed base case was able to produce up to 15,311 L per year in the MD system and cover a... [more]
Life Cycle Assessment of Horse Manure Treatment
Ola Eriksson, Åsa Hadin, Jay Hennessy, Daniel Jonsson
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: anaerobic digestion, bedding material, biogas, combustion, composting, horse manure, incineration, life cycle assessment (LCA)
Horse manure consists of feces, urine, and varying amounts of various bedding materials. The management of horse manure causes environmental problems when emissions occur during the decomposition of organic material, in addition to nutrients not being recycled. The interest in horse manure undergoing anaerobic digestion and thereby producing biogas has increased with an increasing interest in biogas as a renewable fuel. This study aims to highlight the environmental impact of different treatment options for horse manure from a system perspective. The treatment methods investigated are: (1) unmanaged composting; (2) managed composting; (3) large-scale incineration in a waste-fired combined heat and power (CHP) plant; (4) drying and small-scale combustion; and (5) liquid anaerobic digestion with thermal pre-treatment. Following significant data uncertainty in the survey, the results are only indicative. No clear conclusions can be drawn regarding any preference in treatment methods, with... [more]
Optimal Scheduling and Real-Time State-of-Charge Management of Energy Storage System for Frequency Regulation
Jin-Sun Yang, Jin-Young Choi, Geon-Ho An, Young-Jun Choi, Myoung-Hoe Kim, Dong-Jun Won
February 27, 2019 (v1)
Keywords: energy management, energy storage system (ESS), frequency regulation (FR), optimal scheduling, state-of-charge (SOC)
An energy storage system (ESS) in a power system facilitates tasks such as renewable integration, peak shaving, and the use of ancillary services. Among the various functions of an ESS, this study focused on frequency regulation (or secondary reserve). This paper presents an optimal scheduling algorithm for frequency regulation by an ESS. This algorithm determines the bidding capacity and base point of an ESS in each operational period to achieve the maximum profit within a stable state-of-charge (SOC) range. However, the charging/discharging efficiency of an ESS causes SOC errors whenever the ESS performs frequency regulation. With an increase in SOC errors, the ESS cannot respond to an automatic generation control (AGC) signal. This situation results in low ESS performance scores, and finally, the ESS is disqualified from performing frequency regulation. This paper also presents a real-time SOC management algorithm aimed at solving the SOC error problem in real-time operations. This... [more]
Cost Analysis of Direct Methanol Fuel Cell Stacks for Mass Production
Mauro Francesco Sgroi, Furio Zedde, Orazio Barbera, Alessandro Stassi, David Sebastián, Francesco Lufrano, Vincenzo Baglio, Antonino Salvatore Aricò, Jacob Linder Bonde, Michael Schuster
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: catalysts, cost analysis, direct methanol fuel cell (DMFC), Membranes, stack
Fuel cells are very promising technologies for efficient electrical energy generation. The development of enhanced system components and new engineering solutions is fundamental for the large-scale deployment of these devices. Besides automotive and stationary applications, fuel cells can be widely used as auxiliary power units (APUs). The concept of a direct methanol fuel cell (DMFC) is based on the direct feed of a methanol solution to the fuel cell anode, thus simplifying safety, delivery, and fuel distribution issues typical of conventional hydrogen-fed polymer electrolyte fuel cells (PEMFCs). In order to evaluate the feasibility of concrete application of DMFC devices, a cost analysis study was carried out in the present work. A 200 W-prototype developed in the framework of a European Project (DURAMET) was selected as the model system. The DMFC stack had a modular structure allowing for a detailed evaluation of cost characteristics related to the specific components. A scale-down... [more]
Development of Correlations for Windage Power Losses Modeling in an Axial Flux Permanent Magnet Synchronous Machine with Geometrical Features of the Magnets
Alireza Rasekh, Peter Sergeant, Jan Vierendeels
February 27, 2019 (v1)
Keywords: AFPMSM, Computational Fluid Dynamics, magnet parameters, windage losses
In this paper, a set of correlations for the windage power losses in a 4 kW axial flux permanent magnet synchronous machine (AFPMSM) is presented. In order to have an efficient machine, it is necessary to optimize the total electromagnetic and mechanical losses. Therefore, fast equations are needed to estimate the windage power losses of the machine. The geometry consists of an open rotor⁻stator with sixteen magnets at the periphery of the rotor with an annular opening in the entire disk. Air can flow in a channel being formed between the magnets and in a small gap region between the magnets and the stator surface. To construct the correlations, computational fluid dynamics (CFD) simulations through the frozen rotor (FR) method are performed at the practical ranges of the geometrical parameters, namely the gap size distance, the rotational speed of the rotor, the magnet thickness and the magnet angle. Thereafter, two categories of formulations are defined to make the windage losses dim... [more]
A Hybrid Modular Multilevel Converter with Partial Embedded Energy Storage
Georgios Konstantinou, Josep Pou, Daniel Pagano, Salvador Ceballos
February 27, 2019 (v1)
Keywords: Energy Storage, hybrid multilevel converters, modular multilevel converter (MMC), multilevel converters
Modular and cascaded multilevel converters provide a functional solution for the integration of energy storage systems (ESSs). This paper develops a hybrid multilevel converter based on the modular multilevel converter (MMC) that can be functionally extended with partial embedded ESS as a fraction of the overall converter power rating. The configuration, which can operate as a typical DC-AC converter, enables multi-directional power flow between the DC- and AC-side of the converter, as well as the embedded energy storage elements. The use of a three-phase flying-capacitor submodule eliminates the second-order harmonic oscillations present in modular cascaded multilevel converters. Current, voltage and power control are discussed in the paper while simulation results illustrate the operation of the hybrid MMC as a DC-AC converter in a typical inverter application and the additional functions and control of the embedded ESS.
Study of Unwanted Emissions in the CENELEC-A Band Generated by Distributed Energy Resources and Their Influence over Narrow Band Power Line Communications
Noelia Uribe-Pérez, Itziar Angulo, Luis Hernández-Callejo, Txetxu Arzuaga, David de la Vega, Amaia Arrinda
February 27, 2019 (v1)
Keywords: Distributed Energy Resources, meter reading, microgrids, Narrow-Band Power Line Communications, noise
Distributed Energy Resources might have a severe influence on Power Line Communications, as they can generate interfering signals and high frequency emissions or supraharmonics that may cause loss of metering and control data. In this paper, the influence of various energy resources on Narrowband Power Line Communications is described and analyzed through several test measurements performed in a real microgrid. Accordingly, the paper describes the effects on smart metering communications through the Medium Access Control (MAC) layer analysis. Results show that the switching frequency of inverters and the presence of battery chargers are remarkable sources of disturbance in low voltage distribution networks. In this sense, the results presented can contribute to efforts towards standardization and normative of emissions at higher frequencies higher, such as CENELEC EN 50160 and IEC/TS 62749.
Augmented Nonlinear Controller for Maximum Power-Point Tracking with Artificial Neural Network in Grid-Connected Photovoltaic Systems
Suliang Ma, Mingxuan Chen, Jianwen Wu, Wenlei Huo, Lian Huang
February 27, 2019 (v1)
Keywords: artificial neural network (ANN), augmentation system, DC/DC converter, maximum power-point tracking (MPPT), non-linear controller, photovoltaic (PV) systems
Photovoltaic (PV) systems have non-linear characteristics that generate maximum power at one particular operating point. Environmental factors such as irradiance and temperature variations greatly affect the maximum power point (MPP). Diverse offline and online techniques have been introduced for tracking the MPP. Here, to track the MPP, an augmented-state feedback linearized (AFL) non-linear controller combined with an artificial neural network (ANN) is proposed. This approach linearizes the non-linear characteristics in PV systems and DC/DC converters, for tracking and optimizing the PV system operation. It also reduces the dependency of the designed controller on linearized models, to provide global stability. A complete model of the PV system is simulated. The existing maximum power-point tracking (MPPT) and DC/DC boost-converter controller techniques are compared with the proposed ANN method. Two case studies, which simulate realistic circumstances, are presented to demonstrate th... [more]
Experimental and Potential Analysis of a Single-Valve Expander for Waste Heat Recovery of a Gasoline Engine
Wenzhi Gao, Wangbo He, Lifeng Wei, Guanghua Li, Ziqi Liu
February 27, 2019 (v1)
Keywords: gasoline engine, intake valve timing, piston expander, Rankine cycle, waste heat recovery
In this paper, a Rankine cycle test system is established to recover exhaust energy from a 2.0 L gasoline engine. Experiments on the system’s performance are carried out under various working conditions. The experimental results indicate that the recovery power of the expander is strongly related to the load and speed of the gasoline engine. It is found that when the output power of the gasoline engine is 39.8⁻76.6 kW, the net power of the expander is 1.8⁻2.97 kW, which is equivalent to 3.9%⁻4.9% of the engine power. The performance simulation shows that the mass flow rate, power output, and isentropic efficiency of the piston expander are directly determined by the intake valve timing. Selecting a suitable intake valve timing can optimize the performance of the expander. The simulation results show that a 1 kW increment in power can be obtained only by selecting an optimum intake open timing. The experimental results further verify that the single-valve piston expander, because of its... [more]
American’s Energy Future: An Analysis of the Proposed Energy Policy Plans in Presidential Election
Ming-Hsun Cheng, Minliang Yang, Yu Wang
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: energy future, party polarization, president election, public opinion, Renewable and Sustainable Energy
As the leader of the largest economy, President of the United States has substantive influence on addressing climate change problems. However, a presidential election is often dominated by issues other than energy problems. This paper focuses on the 2016 presidential election, and examines the energy plans proposed by the leading Democrat and Republican candidates. Our data from the Iowa caucus survey in January 2016 suggests that voters were more concerned about terrorism and economic issues than environmental issues. We then compare the Democratic and Republican candidate’s view of America’s energy future, and evaluate their proposed renewable energy targets. We find that the view on renewable energy is polarized between Democratic and Republican candidates, while candidates from both parties agree on the need for energy efficiency. Results from our ordinal least squares regression models suggests that Democratic candidates have moderate to ambitious goals for developing solar and ot... [more]
Soiling and Cleaning of Polymer Film Solar Reflectors
Christopher Sansom, Aránzazu Fernández-García, Florian Sutter, Heather Almond, Peter King, Lucía Martínez-Arcos
February 27, 2019 (v1)
Subject: Other
Keywords: concentrating solar power (CSP), mirror cleaning, polymer film, reflectance, soiling, solar collector
This paper describes the accelerated ageing of commercially available silvered polymer film by contact cleaning using brushes and water in the presence of soiling created by dust and sand particles. These conditions represent cleaning regimes in real concentrating solar power (CSP) solar fields in arid environments, where contact cleaning using brushes and water is often required to clean the reflecting surfaces. Whilst suitable for glass reflectors, this paper discusses the effects of these established cleaning processes on the optical and visual characteristics of polymer film surfaces, and then describes the development of a more benign but effective contact cleaning process for cleaning polymer reflectors. The effects of a range of cleaning brushes are discussed, with and without the presence of water, in the presence of sand and dust particles from selected representative locations. The experiments were repeated using different experimental equipment at Plataforma Solar de Almería... [more]
A Novel Boil-Off Gas Re-Liquefaction Using a Spray Recondenser for Liquefied Natural-Gas Bunkering Operations
Jiheon Ryu, Chihun Lee, Yutaek Seo, Juneyoung Kim, Suwon Seo, Daejun Chang
February 27, 2019 (v1)
Subject: Other
Keywords: boil-off gas, bunkering, liquefied natural gas, re-liquefaction, recondenser
This study presents the design of a novel boil-off gas (BOG) re-liquefaction technology using a BOG recondenser system. The BOG recondenser system targets the liquefied natural gas (LNG) bunkering operation, in which the BOG phase transition occurs in a pressure vessel instead of a heat exchanger. The BOG that is generated during LNG bunkering operation is characterized as an intermittent flow with various peak loads. The system was designed to temporarily store the transient BOG inflow, condense it with subcooled LNG and store the condensed liquid. The superiority of the system was verified by comparing it with the most extensively employed conventional re-liquefaction system in terms of consumption energy and via an exergy analysis. Static simulations were conducted for three compositions; the results indicated that the proposed system provided 0 to 6.9% higher efficiencies. The exergy analysis indicates that the useful work of the conventional system is 24.9%, and the useful work of... [more]
Reorientation of Magnetic Graphene Oxide Nanosheets in Crosslinked Quaternized Polyvinyl Alcohol as Effective Solid Electrolyte
Jia-Shuin Lin, Wei-Ting Ma, Chao-Ming Shih, Bor-Chern Yu, Li-Wei Teng, Yi-Chun Wang, Kong-Wei Cheng, Fang-Chyou Chiu, Shingjiang Jessie Lue
February 27, 2019 (v1)
Subject: Other
Keywords: crosslinked quaternized polyvinyl alcohol (CL-QPVA), direct methanol alkaline fuel cell (DMAFC), graphene oxide-iron oxide (GO-Fe3O4), magnetic field, reorientation
This work aims to clarify the effect of magnetic graphene oxide (GO) reorientation in a polymer matrix on the ionic conduction and methanol barrier properties of nanocomposite membrane electrolytes. Magnetic iron oxide (Fe₃O₄) nanoparticles were prepared and dispersed on GO nanosheets (GO-Fe₃O₄). The magnetic GO-Fe₃O₄ was imbedded into a quaternized polyvinyl alcohol (QPVA) matrix and crosslinked (CL-) with glutaraldehyde (GA) to obtain a polymeric nanocomposite. A magnetic field was applied in the through-plane direction during the drying and film formation steps. The CL-QPVA/GO-Fe₃O₄ nanocomposite membranes were doped with an alkali to obtain hydroxide-conducting electrolytes for direct methanol alkaline fuel cell (DMAFC) applications. The magnetic field-reoriented CL-QPVA/GO-Fe₃O₄ electrolyte demonstrated higher conductivity and lower methanol permeability than the unoriented CL-QPVA/GO-Fe₃O₄ membrane or the CL-QPVA film. The reoriented CL-QPVA/GO-Fe₃O₄ nanocomposite was used as the... [more]
Hydraulic Hybrid Excavator—Mathematical Model Validation and Energy Analysis
Paolo Casoli, Luca Riccò, Federico Campanini, Andrea Bedotti
February 27, 2019 (v1)
Keywords: energy analysis, fuel saving, hydraulic hybrid excavator, numerical modeling
Recent demands to reduce pollutant emissions and improve energy efficiency have driven the implementation of hybrid solutions in mobile machinery. This paper presents the results of a numerical and experimental analysis conducted on a hydraulic hybrid excavator (HHE). The machinery under study is a middle size excavator, whose standard version was modified with the introduction of an energy recovery system (ERS). The proposed ERS layout was designed to recover the potential energy of the boom, using a hydraulic accumulator as a storage device. The recovered energy is utilized through the pilot pump of the machinery which operates as a motor, thus reducing the torque required from the internal combustion engine (ICE). The analysis reported in this paper validates the HHE model by comparing numerical and experimental data in terms of hydraulic and mechanical variables and fuel consumption. The mathematical model shows its capability to reproduce the realistic operating conditions of the... [more]
The Energy Audit Activity Focused on the Lighting Systems in Historical Buildings
Giacomo Salvadori, Fabio Fantozzi, Michele Rocca, Francesco Leccese
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: energy audit, energy saving, historical buildings, lamps replacement, lighting systems
The energy audit for a building is a procedure designed mainly to obtain adequate knowledge of the energy consumption profile, identify, and quantify opportunities for energy savings by a cost-benefit analysis and report, clearly and comprehensively, about the obtained results. If the audit is referred to a building with a significant historical and artistic value, a compatibility evaluation of the energy saving interventions with the architectural features should also be developed. In this paper, analysing the case study of a historical building used as public offices in Pisa (Italy), the authors describe how it is possible to conduct an energy audit activity (especially dedicated to the lighting system) and they show how, for this type of buildings, it is possible to obtain significant energy savings with a refurbishment of the lighting system. A total number of seven interventions on indoor and outdoor lighting sub-systems were analysed in the paper. They are characterised by absolu... [more]
Wind Turbines’ End-of-Life: Quantification and Characterisation of Future Waste Materials on a National Level
Niklas Andersen, Ola Eriksson, Karl Hillman, Marita Wallhagen
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: composites, copper, decommission, electronics, end-of-life, iron, materials, plastic, recycling, Steel, Sweden, waste, wind turbine
Globally, wind power is growing fast and in Sweden alone more than 3000 turbines have been installed since the mid-1990s. Although the number of decommissioned turbines so far is few, the high installation rate suggests that a similarly high decommissioning rate can be expected at some point in the future. If the waste material from these turbines is not handled sustainably the whole concept of wind power as a clean energy alternative is challenged. This study presents a generally applicable method and quantification based on statistics of the waste amounts from wind turbines in Sweden. The expected annual mean growth is 12% until 2026, followed by a mean increase of 41% until 2034. By then, annual waste amounts are estimated to 240,000 tonnes steel and iron (16% of currently recycled materials), 2300 tonnes aluminium (4%), 3300 tonnes copper (5%), 340 tonnes electronics (<1%) and 28,000 tonnes blade materials (barely recycled today). Three studied scenarios suggest that a well-func... [more]
Optimization of Key Parameters of Energy Management Strategy for Hybrid Electric Vehicle Using DIRECT Algorithm
Jingxian Hao, Zhuoping Yu, Zhiguo Zhao, Peihong Shen, Xiaowen Zhan
February 27, 2019 (v1)
Keywords: DIRECT, energy management strategy, fuel economy, hybrid electric vehicle, logic threshold value, parameters optimization
The rule-based logic threshold control strategy has been frequently used in energy management strategies for hybrid electric vehicles (HEVs) owing to its convenience in adjusting parameters, real-time performance, stability, and robustness. However, the logic threshold control parameters cannot usually ensure the best vehicle performance at different driving cycles and conditions. For this reason, the optimization of key parameters is important to improve the fuel economy, dynamic performance, and drivability. In principle, this is a multiparameter nonlinear optimization problem. The logic threshold energy management strategy for an all-wheel-drive HEV is comprehensively analyzed and developed in this study. Seven key parameters to be optimized are extracted. The optimization model of key parameters is proposed from the perspective of fuel economy. The global optimization method, DIRECT algorithm, which has good real-time performance, low computational burden, rapid convergence, is sel... [more]
Leaching of Metal Ions from Blast Furnace Slag by Using Aqua Regia for CO₂ Mineralization
Jun-Hwan Bang, Seung-Woo Lee, Chiwan Jeon, Sangwon Park, Kyungsun Song, Whan Joo Jo, Soochun Chae
February 27, 2019 (v1)
Keywords: blast furnace slag, calcium leaching, CO2 mineralization
Blast furnace slag (BFS) was selected as the source of Ca for CO₂ mineralization purposes to store CO₂ as CaCO₃. BFS was dissolved using aqua regia (AR) for leaching metal ions for CO₂ mineralization and rejecting metal ions that were not useful to obtain pure CaCO₃ (as confirmed by XRD analysis). The AR concentration, as well as the weight of BFS in an AR solution, was varied. Increasing the AR concentration resulted in increased metal ion leaching efficiencies. An optimum concentration of 20% AR was required for completely leaching Ca and Mg for a chemical reaction with CO₂ and for suppressing the leaching of impurities for the production of high-purity carbonate minerals. Increasing the liquid-to-solid ratio (L/S) resulted in the increased leaching of all metal ions. An optimum L/S of 0.3/0.03 (=10) was required for completely leaching alkaline-earth metal ions for CO₂ mineralization and for retaining other metal ions in the filtered residue. Moreover, the filtrate obtained using 20... [more]
Two Dimensional Thermal-Hydraulic Analysis for a Packed Bed Regenerator Used in a Reheating Furnace
Chien-Nan Lin, Jiin-Yuh Jang, Yi-Shiun Lai
February 27, 2019 (v1)
Keywords: heat exchanger, packed bed, regenerator, reheating furnace
Packed bed is widely used for different industries and technologies, such as heat exchangers, heat recovery, thermal energy storage and chemical reactors. In modern steel industry, packed bed regenerator is widely utilized in the reheating furnace to increase the furnace efficiency. This study established a two dimensional numerical model to simulate a packed bed used in regenerative furnaces. The physical properties of fluids and packed stuffing (such as density, thermal conductivity, and specific heat) are considered as functions of temperature to adapt the large temperature variation in operation. The transient temperature profiles of the flue gas, packed bed, and air during the heating and regeneration period are examined for various switching time (30, 60, 120, and 240 s). The results reveal that, during the heating period, the spanwise averaged heat transfer coefficient is decreased along the longitudinal downstream direction, while during the regeneration period, the opposite tr... [more]
A Novel Hybrid Short Term Load Forecasting Model Considering the Error of Numerical Weather Prediction
Guowei Cai, Wenjin Wang, Junhai Lu
February 27, 2019 (v1)
Keywords: artificial bee colony (ABC), seasonal autoregressive integrated moving average (SARIMA), short term load forecasting (STLF), support vector regression (SVR)
In order to reduce the effect of numerical weather prediction (NWP) error on short term load forecasting (STLF) and improve the forecasting accuracy, a new hybrid model based on support vector regression (SVR) optimized by an artificial bee colony (ABC) algorithm (ABC-SVR) and seasonal autoregressive integrated moving average (SARIMA) model is proposed. According to the different day types and effect of the NWP error on forecasting prediction, working days and weekends load forecasting models are selected and constructed, respectively. The ABC-SVR method is used to forecast weekends load with large fluctuation, in which the best parameters of SVR are determined by the ABC algorithm. The working days load forecasting model is constructed based on SARIMA modified by ABC-SVR (AS-SARIMA). In the AS-SARIMA model, the ability of SARIMA to respond to exogenous variables is improved and the effect of NWP error on prediction accuracy is reduced more than with ABC-SVR. Contrast experiments are c... [more]
Modeling and Controller Design of PV Micro Inverter without Using Electrolytic Capacitors and Input Current Sensors
Faa Jeng Lin, Hsuang Chang Chiang, Jin Kuan Chang
February 27, 2019 (v1)
Keywords: active-clamped current-fed push-pull DC-DC converter, incremental conductance maximum power point tracking, input current, ripple voltage cancellation technique, sensorless
This paper outlines the modeling and controller design of a novel two-stage photovoltaic (PV) micro inverter (MI) that eliminates the need for an electrolytic capacitor (E-cap) and input current sensor. The proposed MI uses an active-clamped current-fed push-pull DC-DC converter, cascaded with a full-bridge inverter. Three strategies are proposed to cope with the inherent limitations of a two-stage PV MI: (i) high-speed DC bus voltage regulation using an integrator to deal with the 2nd harmonic voltage ripples found in single-phase systems; (ii) inclusion of a small film capacitor in the DC bus to achieve ripple-free PV voltage; (iii) improved incremental conductance (INC) maximum power point tracking (MPPT) without the need for current sensing by the PV module. Simulation and experimental results demonstrate the efficacy of the proposed system.
A New Design Optimization Method for Permanent Magnet Synchronous Linear Motors
Juncai Song, Fei Dong, Jiwen Zhao, Siliang Lu, Le Li, Zhenbao Pan
February 27, 2019 (v1)
Keywords: 3D finite element analysis (3D-FEA), gravity center neighborhood algorithm (GCNA), multiple support vector machine (multi-SVM), non-parametric quick calculation model, permanent magnet linear synchronous motors (PMSLM), thrust, thrust ripple
This study focused on the design optimization of permanent magnet synchronous linear motors (PMSLM) that are applied in microsecond laser cutting machines. A new design optimization method was introduced to enhance PMSLM performances in terms of motor thrust, thrust ripple, and inductive electromotive force (EMF). Based on accurate 3D finite element analysis (3D-FEA), a multiple support vector machine (multi-SVM) was proposed to build a non-parametric quick calculation model by mapping the relation between multivariate structure parameters and multivariate operation performances. The gravity center neighborhood algorithm (GCNA) was also applied to search the global optimal combination of the structure parameters by locating the gravity center of the multi-SVM model. The superiority and validity of this method are verified by experiments.
Strategy Design of Hybrid Energy Storage System for Smoothing Wind Power Fluctuations
Jingyu Liu, Lei Zhang
February 27, 2019 (v1)
Keywords: battery, hybrid energy storage system (HESS), power allocation, state-of-charge (SOC), supercapacitor, wind power, wind power regulation system
With the increasing contribution of wind power plants, the reliability and security of modern power systems have become a huge challenge due to the uncertainty and intermittency of wind energy sources. In this paper, a hybrid energy storage system (HESS) consisting of battery and supercapacitor is built to smooth the power fluctuations of wind power. A power allocation strategy is proposed to give full play to the respective advantages of the two energy storage components. In the proposed strategy, the low-frequency and high-frequency components of wind power fluctuations are absorbed by battery groups and supercapacitor groups, respectively. By inhibiting the low-frequency components of supercapacitor current, the times of charging-discharging of battery groups can be significantly reduced. A DC/AC converter is applied to achieve the power exchange between the HESS and the grid. Adjustment rules for regulating state-of-charge (SOC) of energy storage elements are designed to avoid over... [more]
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