In this study, fast Fourier transform and inverse transform are adopted for noise reduction filtering the data of load rejection pressure of a single unit in a one-tube, four-unit pumped storage power station. Five-spot triple smoothing method is used to extract the time-average and pulsation value of the water hammer pressure of the spiral case and draft tube inlet. The reasonable correction formula is put forward, and the pulsating pressure rise rate of the spiral case (4.44%) and the draft tube inlet (−1.22%) are obtained. A mathematical model is also established for the transition process of the water conveyance and power generation system of the pumped storage power station, and the field single-unit load rejection condition is simulated. The simulation results are consistent with the measurements, and the accuracy of the calculation model in predicting the time-average pressure of water hammer is verified. Thus, the extreme successive load rejection conditions can be simulated ba... [more]

The wind energy conversion system (WEC) has been increasingly proposed to capture wind energy producing electrical power in high efficiency. One of the most important factors that has significant influence on the overall efficiency is the performance of generators in a fixed-speed wind turbine. The efficiency of the generator strongly depends on the operating speed. Therefore, the generator should be controlled to operate at the rated speed to increase the overall efficiency. In this paper, a continuously variable transmission (CVT) was employed to maintain the speed of the generator by controlling the transmission ratio. By employing a position control system based on an electro-hydraulic actuator (EHA), the speed ratio could be tuned continuously to keep the generator at rated speed. Here, an adaptive fuzzy sliding mode control (AFSC) was developed to control the proposed EHA CVT. Mathematical analysis was also carried out to investigate the global stability of the system. Finally, e... [more]

The determination of chemical composition of lignocellulose biomass by wet chemistry analysis is labor-intensive, expensive, and time consuming. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a rapid and no-destructive alternative method. The objective of this work is to develop a NIR calibration model for olive tree lignocellulosic biomass as a rapid tool and alternative method for chemical characterization of olive tree pruning over current wet methods. In this study, 79 milled olive tree pruning samples were analyzed for extractives, lignin, cellulose, hemicellulose, and ash content. These samples were scanned by reflectance diffuse near infrared techniques and a predictive model based on partial least squares (PLS) multivariate calibration method was developed. Five parameters were calibrated: Lignin, cellulose, hemicellulose, ash, and extractives. NIR models obtained were able to predict main components composition with R2cv values over 0.5, except f... [more]

It is well accepted that faults have significant impacts on the safe production of underground coal mines; however, the fault-slip mechanism during longwall mining through a fault still needs to be investigated. In this study, the distribution of microseismicity events during panel mining through a fault is analyzed, and 3-dimensional fast Lagrangian analysis of continua was used to study the mining stress distribution and fault-slip behavior under the two different mining directions, i.e., mining the panel through the fault from the footwall, or mining the panel through the fault from the hanging wall. The research shows that when the panel is mined through the fault from the footwall, the shear displacement of the fault is significantly greater than those created by mining the panel through the fault from the hanging wall. Under the two mining directions, the variation behaviors of the normal stress and shear stress on the fault are quite different, and fault-slips mainly occur in fa... [more]

The design of ground source heat pumps is a fundamental step to ensure the high energy efficiency of heat pump systems throughout their operating years. To enhance the diffusion of ground source heat pump systems, two different tools are developed in the H2020 research project named, “Cheap GSHPs”: A design tool and a decision support system. In both cases, the energy demand of the buildings may not be calculated by the user. The main input data, to evaluate the size of the borehole heat exchangers, is the building energy demand. This paper presents a methodology to correlate energy demand, building typologies, and climatic conditions for different types of residential buildings. Rather than envelope properties, three insulation levels have been considered in different climatic conditions to set up a database of energy profiles. Analyzing European climatic test reference years, 23 locations have been considered. For each location, the overall energy and the mean hourly monthly energy p... [more]

This paper proposes a fault diagnosis and tolerant control methods for an open-switch fault caused in a three-phase three-level neutral-point-clamped (NPC) pulse-width modulation (PWM) active rectifier. The open-switch fault in the three-level NPC active rectifier causes a distortion in the input phase current and a ripple in the DC-link capacitor voltage. Therefore, proper fault diagnosis and tolerant control methods are required to prevent additional failures and performance degradation in the rectifier system. This paper conducted a detailed analysis of the effect of the single open-switch fault on the NPC PWM active rectifier and proposed a fault diagnosis method utilizing the DC link voltage and the phase angle of the input grid voltage. Furthermore, this paper proposes a fault-tolerant control method to reduce the effect of the open-switch fault by compensating a distorted reference voltage. The effectiveness of the proposed fault diagnosis and tolerant control methods are verifi... [more]

In generation expansion planning, sustainable generation expansion planning is gaining more and more attention. Based on the comprehensive consideration of generation expansion planning economics, technology, environment, and other fields, this paper analyzes the sustainable development of power supply planning evaluation indicators and builds a multi-objective generation expansion planning decision model considering sustainable development. According to the target variables in the model, the variables such as attribute variables are divided into different subsets, and the logical relationship analysis method between different nodes is obtained based on Dynamic Bayesian network theory, which reduces the complexity of the planning model problem. The application examples show the feasibility and effectiveness of the proposed model and the solution method.

With the application of information and communication technology (ICT), the modern power system has gradually been updated to a typical cyber physical power system (CPPS). The deployment of distributed measurement devices enriches the application range of power communication services. However, due to the easy accessibility of distributed devices, it also creates favorable conditions for distributed denial-of-service (DDoS) attacks. In this paper, we focus on the security performance and defense strategies of the CPPS against DDoS attacks. In order to construct a coordinated defense in the power and information space, the cyber-attack process with a complete data flow of the CPPS needs to be described precisely. Therefore, a co-simulation technology-based platform is utilized to coordinate various layers in the CPPS and provide a unified research tool for the attack-defense test. On this basis, OPNET is used to replicate DDoS attacks in the information layer. Then, through the load freq... [more]

The composite bucket foundation for offshore wind turbine bears the vertical load from not only the superstructure and the horizontal load, caused by wind and wave, but also from the torque load caused by rotating structures, such as blades. Based on layered soil foundation, the influence of the skirt height, the friction coefficient between soil and bucket foundation and the diameter of the bucket foundation on the stress of the bucket skirt under the torque load are studied in this paper. Moreover, the envelope curves of the bearing capacity of H−T and V−H−T are obtained by the fixed displacement ratio loading method. The bearing capacity characteristics of composite bucket foundation under different loading combinations are analyzed. The results show that: (1) The effect of inside soil on the bucket skirt is greater than that of the outside soil; (2) when composite loads are applied, the torque-bearing capacity decreases slowly with the increase of horizontal force, and when the hor... [more]

State of charge (SOC) estimation is of vital importance for the battery management system in electric vehicles. This paper proposes a new fuzzy logic sliding mode observer for SOC estimation. The second-order resistor-capacitor equivalent circuit model is used to describe the discharging/charging behavior of the battery. The exponential fitting method is applied to determine the parameters of the model. The fuzzy logic controller is introduced to improve the performance of sliding mode observer forming the fuzzy logic sliding mode observer (FLSMO). The Federal Urban Driving Schedule (FUDS), the West Virginia Suburban Driving Schedule (WUBSUB), and the New European Driving Cycle (NEDC) schedule test results show that the average SOC estimation error of FLSMO algorithm is less than 1%. When the initial SOC estimation error is 20%, the FLSMO algorithm can converge to 3% error boundary within 2400 s. Comparison test results show that the FLSMO algorithm has better performance than the slid... [more]

The olive orchard cultivation in Mediterranean countries results in huge amounts of lignocellulosic biomass residues. One of the main residues are olive leaves. Olive leaves contain high concentrations of bioactive antioxidant compounds like oleuropein and luteolin-7-glucoside. The production of biactive compounds from olive leaves requires treatments capable of breaking the lignocellulosic structure. Current research focuses on use of inexpensive, quick, and not harmful to the environment treatments, searching a more simplified large-scale operation approach. Recently, advances in applied chemistry have led to possible new emerging industrial techniques like ultrasound-assisted extraction (UAE). This technology is a promising candidate as a green treatment solution for olive leaves utilization in a biorefinery. However, this application goes through prior optimization of technique and operating conditions. The goal of this study was to optimize the extraction of oleuropein and luteoli... [more]

This work aims to analyze and validate through mathematical modeling and experimental results, in a three-phase three-wire electrical system, the technical viability of a static power converter with a two-level topology with only two controlled branches (2L2B), operating as a grid-side converter (GSC) in a wind turbine generator based on a doubly fed induction generator (DFIG). With this reduced-switches topology, the GSC is able to regulate the DC-link voltage level from the generator back-to-back converter and provide ancillary services of harmonic filtering and reactive power compensation from linear/nonlinear loads connected to the point of common coupling. An 8-kVA experimental prototype was implemented in the laboratory to validate the proposal. The prototype control system was realized using the dSPACE DS1103 PPC Controller Board platform programmed via MATLAB/Simulink. The effectiveness of the proposed system is verified by comparing the results obtained with the 2L2B topology... [more]

This article presents the results of a comparative analysis of two electronically commutated brushless direct current machines intended for fault-tolerant drives. Two machines designed by the authors were compared: a 12/14 dual-channel brushless direct current motor (DCBLDCM) with permanent magnets and a 12/8 dual-channel switched reluctance motor (DCSRM). Information is provided here on the winding configuration, the parameters, and the power converters of both machines. We developed mathematical models of the DCBLDCM and DCSRM which accounted for the nonlinearity of their magnetization characteristics in dual-channel operation (DCO) and single-channel operation (SCO) modes. The static torque characteristics and flux characteristics of both machines were compared for operation in DCO and SCO modes. The waveforms of the current and the electromagnetic torque are presented for DCO and SCO operating conditions. For DCO mode, an analysis of the behavior of both machines under fault condit... [more]

This study is devoted to investigating the potential use of Jet A in blend along with biodiesel from waste cooking oil, petrol diesel, and renewable diesel. Biodiesel use allows for reducing carbon monoxide (CO), unburned hydrocarbons (HC), and soot due to the oxygen contained in the fuel. The drawbacks in its use are related to the low volatility and high viscosity of vegetable oil that cause difficulties in fuel atomization and in its mixing with air. Moreover, an increased amount of NOx emission was observed. The aim of the experimentation is to evaluate the ability of Jet A of enhancing the combustion process and pollutant emissions of a diesel engine, thus overcoming the difficulties in biodiesel usage (high viscosity, poor cold weather performance, compatibility with diesel engine equipment) and then increasing the renewable fuel percentage in the fuel. Testing was carried out on a small displacement common rail diesel engine. Hardware and ECU setting were not modified in order t... [more]

This paper examines the recent advances made in the field of Deep Learning (DL) methods for the automated identification of Partial Discharges (PD). PD activity is an indication of the state and operational conditions of electrical equipment systems. There are several techniques for on-line PD measurements, but the typical classification and recognition method is made off-line and involves an expert manually extracting appropriate features from raw data and then using these to diagnose PD type and severity. Many methods have been developed over the years, so that the appropriate features expertly extracted are used as input for Machine Learning (ML) algorithms. More recently, with the developments in computation and data storage, DL methods have been used for automated features extraction and classification. Several contributions have demonstrated that Deep Neural Networks (DNN) have better accuracy than the typical ML methods providing more efficient automated identification technique... [more]

The aim of this study is to assess how different renovation scenarios affect the environmental and economic impacts of a multi-dwelling building in a Nordic climate, how these aspects are correlated and how different energy carriers affect different environmental impact categories. In order to reduce greenhouse gas emissions, the European Union has set an agenda in order to reduce energy use in buildings. New buildings on the European market have a low replacement rate, which makes building renovation an important factor for achieving the European Union goals. In this study, eight renovation strategies were analyzed following the European Committee for Standardization standards for life cycle assessment and life cycle costs of buildings. This study covers all life cycle steps from cradle to grave. The renovation scenarios include combinations of photovoltaics, geothermal heat pumps, heat recovery ventilation and improved building envelopes. Results show that, depending on the energy ca... [more]

Driver perception, decision, and control behaviors are easily affected by traffic conditions and driving style, showing the tendency of randomness and personalization. Brake intention and intensity are integrated and control-oriented parameters that are crucial to the development of an intelligent braking system. In this paper, a composite machine learning approach was proposed to predict driver brake intention and intensity with a proper prediction horizon. Various driving data were collected from Controller Area Network (CAN) bus under a real driving condition, which mainly contained urban and rural road types. ReliefF and RReliefF (they don’t have abbreviations) algorithms were employed as feature subset selection methods and applied in a prepossessing step before the training. The rank importance of selected predictors exhibited different trends or even negative trends when predicting brake intention and intensity. A soft clustering algorithm, Fuzzy C-means, was adopted to label th... [more]

This work presents a computational method for the simulation of wind speeds and for the calculation of the statistical distributions of wind farm (WF) power curves, where the wake effects and terrain features are taken into consideration. A three-parameter (3-P) logistic function is used to represent the wind turbine (WT) power curve. Wake effects are simulated by means of the Jensen’s wake model. Wind shear effect is used to simulate the influence of the terrain on the WTs located at different altitudes. An analytical method is employed for deriving the probability density function (PDF) of the WF power output, based on the Weibull distribution for describing the cumulative wind speed behavior. The WF power curves for four types of terrain slopes are analyzed. Finally, simulations applying the Monte Carlo method on different sample sizes are provided to validate the proposed model. The simulation results indicate that this approximated formulation is a possible substitute for WF outpu... [more]

Selection of the most appropriate contractor for the installation of solar panels is essential to maximizing the benefit of this renewable, sustainable energy source. Solar energy is one of the 100% renewable energy sources, but implementation may not be very simple and cost-effective. A key phase in the implementation of renewable energy is the evaluation of contractors for the installation of solar panels, which is addressed as a multi-criteria decision-making (MCDM) problem. A new hybrid method is proposed that combines the stepwise weight analysis ratio assessment (SWARA) and full consistent method (FUCOM) weights that are represented as grey numbers used with traditional grey relational analysis (GRA) and evaluation based on distance from average solution (EDAS) methods. The ranking of contractors by both methods is the same, which confirmed the results presented in this research. The use of the grey SWARA-FUCOM weighting method combined with the GRA and EDAS methods increased the... [more]

A DC power flow controller (DCPFC) can help to facilitate power flow routing in the multi-terminal high-voltage direct current (HVDC) transmission system. Realizing its multi-port output can effectively improve the device regulate range and capability. Based on analysis of the traditional multi-port interline DC power flow controller (MI-DCPFC), this paper presents a switches reduced topology of MI-DCPFC. In addition, for solving the problem of coupling of the port-output voltage of the traditional MI-DCPFC, a novel control strategy based on carrier phase shifting pulse width modulation (CPS-PWM) is proposed. It implements the decoupling of the port-output voltage of MI-DCPFC, which can ensure completely independent tracking of the power flow regulating commands for different controlled lines. Moreover, key relationships between the system state variables are also analyzed and detailed in this study. Finally, the performance of the proposed controller and control strategy are confirmed... [more]

Due to the unbalanced three-phase loads, the single-phase distributed photovoltaic (PV) integration, the long feeders, and the heavy loads in a three-phase four-wire low voltage distribution network (LVDN), the voltage unbalance factor (VUF), the network loss and the voltage deviation are relatively high. Considering the uncertain fluctuation of the PV output and the load power, a robust optimal allocation of decentralized reactive power compensation (RPC) devices model for a three-phase four-wire LVDN is proposed. In this model, the uncertain variables are described as box uncertain sets, the three-phase simultaneous switching capacity and single-phase independent switching capacity of the RPC devices are taken as decision variables, and the objective is to minimize the total power loss of the LVDN under the extreme scenarios of uncertain variables. The bi-level optimization method is used to transform the robust optimization model with uncertain variables into bi-level deterministic... [more]

This study aims to investigate the influence of the current direction on the energy production of a tidal turbines array. It is based on a three-dimensional (3D) numerical simulation of the flow where the turbines are represented with actuator disks. The case study consists of modelling the energy extraction of a small array of turbines (staggered and aligned layouts) placed in the Raz Blanchard (Alderney Race, France). The simulations are performed with hydrodynamic data (current magnitude and direction) representative of a mean tide, with several resistance forces and ambient turbulence intensities. The influence of the current direction on the energy production is highlighted by comparing the simulations forced with the real current direction with those in which the angle of incidence between the incoming flow and the turbine’s axis is “switched off” (bi-directional flow). When the flow is aligned with the turbines’ axis (misalignment “switched off”), the staggered layout produces m... [more]

The direct carbon fuel cell (DCFC) is an emerging technology for energy production. The application of biomass in DCFCs will be a major transition from the use of coal to generate energy. However, the relationship between biomass or biochar composition and the electrochemical performance of a DCFC is yet to be studied. The performance of a DCFC using fuel sources derived from woody and non-woody biomass were compared in this study. The effect of pyrolysis temperature ranges from 550 °C to 850 °C on the preparation of biochar from rubber wood (RW) and rice husk (RH) were evaluated for power generation from DCFCs. In addition, the effect of applying chemical pre-treatment and post-treatment on biochar were further investigated for DCFC performance. In general, the power density derived from rubber wood biochar is significantly higher (2.21 mW cm−2) compared to rice husk biochar (0.07 mW cm−2). This might be due to the presence of an oxygen functional group, higher fixed carbon content, a... [more]

Large synchronous generators are the heart of the modern world, while producing the vast majority of the electric power consumed globally. Although they are robust devices, they are prone to degradation and failure. If such failures are not detected at an early stage, then the negative impact may be catastrophic in terms of financial costs, repair times, human lives and quality of life. This is the reason for continuous research in the field of condition monitoring aiming towards the reliable operation of synchronous generators. This paper proposes a novel technique for the diagnosis of the static eccentricity in synchronous generators. The proposed approach is off-line and non-intrusive, allowing the estimation of the fault severity with stator current measurements only. The performed work has been carried out with Finite Element Simulations and extensive experimental testing.

Of the cost centres that combine to result in Levelised Cost of Energy (LCOE), O&M costs play a significant part. Several developers have calculated component costs, demonstrating how they can become commercially competitive with other forms of renewable energy. However, there are uncertainties relating to the O&M figures that can only be reduced through lessons learned at sea. This work presents an O&M model calibrated with data from real sea experience of a wave energy device deployed at the Biscay Marine energy Platform (BiMEP): the OPERA O&M Model. Two additional case studies, utilising two other O&M calculation methodologies, are presented for comparison with the OPERA O&M Model. The second case study assumes the inexistence of an O&M model, utilising a Simplified Approach. The third case study applies DTOcean’s (a design tool for ocean energy arrays) O&M module. The results illustrate the potential advantages of utilising real sea data for the calibration and development of an O&... [more]