Wind turbines are very vulnerable to lightning because of their height, sharp edges and remote locations often with low soil conductivity. In this paper we present numerical simulations of the impedance of a typical wind turbine grounding geometry. We analyze the effect of interconnecting grounding systems of different wind turbines. IEC TR61400-24 suggests interconnection of grounding electrodes of wind turbines through horizontal electrodes (in the form of insulated or bare conductors) to achieve low steady-state grounding resistance. The analysis takes into account frequency dependent soil parameters. It is shown that the low frequency grounding impedance is reduced by a factor of two or more. However, the reduction is lower at higher frequencies because of the interconnection wire's inductance.
The life style of building occupants is continuously arising towards conditions that are more comfortable involving, on turn, the growing of the electric energy consumptions for climatization purposes. This calls for the improvement of the efficiencies of equipment along with environmental performance of building materials. Laboratory analyses of samples of mixed materials, utilizing tomato stems harvested in Sicily and Cataluna, have been conducted Thermal conductance and mechanical properties have been detected for different rates of bio-component and inert materials. First results of the thermal properties seem to situate such bio-composites among the insulating building materials, for all the analyzed percentages of the presence of tomato stems. On the other hand, measurements regarding mechanical properties of the same samples suggest that further analyses are certainly required in order of getting definitive judgments concerning the optimal rate of tomato fibers.
emission trading system is one of the recent controlling tools for the greenhouse gases (GHG) emission. This policy was made in order to decrease the amount of emission from pollutant industries. One of the most challenging subject in this criteria is the mechanism of allowance allocation. The grandfathering and the allowance auction are two common approaches to allocate allowances to generation companies in electricity market. . In this paper, the emission market is modeled to investigate the interaction of the two market simultaneously. To model the behavior of the generation units in the presence of emission market, the Cournot model for electricity market and the allowance supply function for emission market is utilized. Furthermore, the impact of emission allowance auction, the approaches of allocating emission allowances to power plants and allowance trading in emission market on the profitability of production units in the electricity market is investigated.
The present work aims at analyzing the use of the wave resource together with solar and wind resources to supply energy to the Pantelleria public bus system, by substituting the existing Diesel buses with electric buses. Wave resource is exploited by means of the ISWEC (Inertial Sea Wave Energy Converter), a floating, all-enclosed, gyroscopic wave energy converter, deployed at full scale prototype in Pantelleria in 2015. In this paper, the efficiency of an optimal control designed earlier is studied in numerical environment, using a Matlab model and results compared with a Droop Control Method for DC Microgrids Based on Low Bandwidth Communication.
Developing a suitable framework for real-time optimal power flow (RT-OPF) is of utmost importance for ensuring both optimality and feasibility in the operation of energy distribution networks (DNs) under intermittent wind energy penetration. The most challenging issue thereby is that a large-scale complex optimization problem has to be solved in real-time. Online simultaneous optimization of the wind power curtailments of wind stations and the discrete reference values of the slack bus voltage which leads to a mixed-integer nonlinear programming (MINLP) problem, in addition to considering variable reverse power flow, make the optimization problem even much more complicated. To address these difficulties, a two-phase solution approach to RT-OPF is proposed in this paper. In the prediction phase, a number of MINLP OPF problems corresponding to the most probable scenarios of the wind energy penetration in the prediction horizon, by taking its forecasted value and stochastic distribution into account, are solved in parallel. The solution provides a lookup table for optional control strategies for the current prediction horizon which is further divided into a certain number of short time intervals. In the realization phase, one of the control strategies is selected from the lookup table based on the actual wind power and realized to the grid in the current time interval, which will proceed from one interval to the next, till the end of the current prediction horizon. Then, the prediction phase for the next prediction horizon will be activated. A 41-bus medium-voltage DN is taken as a case study to demonstrate the proposed RT-OPF approach.
This paper introduces a characterization of a single Grounding System (GS) or a set of interconnected GSs, according to their safety level and defines their condition of “conventionally safe” and “intrinsically safe”. GSs or a set of them are intrinsically safe, if they guarantee safe touch/step voltages permanently permissible for an assigned ground fault value. It is proposed a new definition of Global Grounding Systems (GGSs) revising that offered by the Standards IEC 61936-1/EN 50522. The paper suggests a safety criterion, useful for urban and industrial areas with reduced accessibility, that allows to identify the safety zone of influence and the intrinsically safe condition of a single GS and of a GGS, constituted by a set of interconnected single GSs.
Solar water heating in homes of low-income families as Energy Efficiency Action enables energetic benefits from points of view of the consumer and the Brazilian electrical system, thereby reducing environmental impacts associated with generation, transmission and distribution of electricity. The purpose of the present study is to evaluate these gains through measurement and verification methodology adapted from the International Performance Measurement and Verification Protocol, from case studies involving Energy Efficiency Projects in the Goiás State, Brazil. This paper also presents the stochastic modelling for the generation of future scenarios of electricity saving resulted by these Energy Efficiency Projects. The model is developed by using the Geometric Brownian Motion Stochastic Process with Mean Reversion associated with the Monte Carlo simulation technique. Results show that the electricity saved from the replacement of electric showers by solar water heating systems in homes of low-income families has great potential to bring financial benefits to such families, and that the reduction in peak demand obtained from this Energy Efficiency Action is advantageous to the Brazilian electrical system. Results contemplate also the future scenarios of electricity saving and a sensitivity analysis in order to verify how values of some parameters influence on the results, once there is no historical data available for obtaining these values.
The purpose of this paper is to compare mathematical modeling and practical bench in order to validate the electrical interactions between an induction generator and a synchronous generator. Two generators was connected to a common bus in steady state, subject to non-linear load. The results comparing modeling and bench tests show that the induction generator besides the active power increasing, has a better way for harmonic currents flowing in common bus. It was concluded that the induction generator repowering and attenuates current harmonic components present at the connection point, improving the network voltage profile.
The growing trend in the annual global temperature makes clear that only the reduction of carbon emissions can be the basis for a meaningful policy to counteract climate change. These considerations explain the importance of urban/architectural resilience and the need to reduce energy consumption to restrict global warming. Therefore the design of urban spaces acts as “thermodynamic mediation” between the constructed object, the human body, and space (environment), between meteorology and physiology (meteorological architecture). One of the key aspects of this approach is design based on meteorological conditions, weather, climate forcing, and thermodynamic demands to obtain architectural and urban shapes that are no longer conceived in a “structural” sense, but rather “climatologically oriented.” Investigating the built environment through tomographic sections processed with CFD software (tomographic environmental section, TENS), it is possible to evaluate the effects of an extreme event on an indoor/outdoor space in order to design appropriate (adaptive) climate mitigation devices, focusing on historical centers where energy retrofitting is always a delicate matter. By “slicing” the environment and studying the initial and boundary conditions, building and environmental performance simulations for outdoor spaces are analyzed in order to test extreme events (heat waves) using climate data series.
The estimation of running times is essential for the railway timetable definition. The trains travel duration must respect some constraints, which depend on the railway network. Usually, the running times minimize the trains travel duration on the railway network. They are typically calculated without considering the energy consumption. The green transportation has recently gained significant importance. In this paper, the energy consumption in the running times estimation is taken into account by defining an optimization problem to calculate the running times for the railway timetable definition. This optimization problem finds the running times which minimize the energy consumption. Precisely, an algorithm to handle the optimization problem with the integration platform for multi-objective and multi-disciplinary optimization modeFRONTIER is defined. The algorithm is tested on a case study and the results are validated with the OpenTrack Railway Simulation Tool.
This paper presents the control strategies by Proportional-Integral (P-I) and Fuzzy Logic (FL) for a DC-DC boost power converter for high output voltage configuration. Standard DC-DC converters are traditionally used for high voltage direct current (HVDC) power transmission systems. But, lack its performances in terms of efficiency, reduced transfer gain and increased cost with sensor units. Moreover, the internal self-parasitic components reduce the output voltage and efficiency of classical high voltage converters (HVC). This investigation focused on extra high-voltage (EHV) DC-DC boost power converter with inbuilt voltage-lift technique and overcome the aforementioned deficiencies. Further, the control strategy is adapted based on proportional-integral (P-I) and fuzzy logic, closed-loop controller to regulate the outputs and ensure the performances. Complete hardware prototype of EHV converter is realized and experimental tasks are set out with digital signal processor (DSP) TMS320F2812 under different perturbation conditions. Observed set of results is provided and shown good conformity with developed hypothetical predictions.
Voltage Source Converters (VSCs) operating in very weak grids with low Short Circuit Ratio (SCR) are known to meet stability challenges. This article investigates instability of a grid connected current-controlled converter under weak grid conditions, which is often attributed to the dynamic interaction between the phase-locked loop (PLL) and system impedance networks. To accomplish this object, available approaches are overviewed, and their advantages and disadvantages are briefly explained. Then a simple yet effective technique based on the joint operation of virtual impedance technique and an amplitude estimation strategy is presented to tackle their shortcomings. The effectiveness of the proposed strategy is finally evaluated using the simulation results.
The overloading of lines due to transmission line outages is often the first step that when not appropriately addressed leads to a system-wide blackout. While enhancing generation capacity or reinforcing the grid are recognized mitigation measures, the advances made in demand response are increasingly offering measures of altering demand to keep line flows within thermal limits. As the proportion of dispatchable generation decreases through increased renewable duplicating conventional stations, the use of flexible demand in this will increasingly grow. This paper presents an assessment of the ability of a demand response approach on a large scale to mitigate the vulnerability of transmission line outages. It is demonstrated by means of integrating the power flow analysis tool, MATPOWER with demand side management simulator based on PowerMatcher Technology. Two terms, line outage distribution factor (LODF) and power transfer distribution factor (PTDF), are used to determine the most effective localized demand side action. The methodology is implemented on a simulation of a previous power outage scenario in Southern Thailand, and the results of outage mitigation have shown the measure of contribution to post-fault recovery made.
Microgrid frequency and voltage regulation is a challenging task, as classical generators with rotational inertia are usually replaced by converter-interfaced systems that inherently do not provide any inertial response. The aim of this paper is to analyse and compare autonomous primary control techniques for alternating current (AC) and direct current (DC) microgrids that improve this transient behaviour. In this context, a virtual synchronous machine (VSM) technique is investigated for AC microgrids, and its behaviour for different values of emulated inertia and droop slopes is tested. Regarding DC microgrids, a virtual-impedance-based algorithm inspired by the operation concept of VSMs is proposed. The results demonstrate that the proposed strategy can be configured to have an analogous behaviour to VSM techniques by varying the control parameters of the integrated virtual-impedances. This means that the steady-state and transient behaviour of converters employing these strategies can be configured independently. As shown in the simulations, this is an interesting feature that could be, for instance, employed for the integration of different dynamic generation or storage systems, such as batteries or supercapacitors.
This paper aims to show some applications of microbial fuel cells (MFCs), a suitable energy harvesting technique, as clean power source to supply a wireless sensor network for environmental monitoring or wastewater treatment or biosensor. An MFC is a bioreactor that converts energy stored in chemical bonds of organic matter into electrical energy. The performance of MFC is limited by a low output voltage and low output power. However this energy may be enough to supply low power applications to replace their batteries. Moreover considering that the performances of MFCs are related to many operating conditions, MFCs can be employed as a biosensor to measure some parameters (Organic matter concentration, temperature, and pH). The applications targets inaccessible environments where soil and waste-water are nonetheless present. In this case, a terrestrial microbial fuel cell (TMFC), based on soil that acts as membrane and as flow of nutrient, it can function as a pH sensor. Instead a wastewater microbial fuel cell (WWMFC), where waste-water acts as flow of nutrient and bacteria, it can operate as a temperature sensor. Other low power devices can be supplied by the harvested energy from MFCs.
There is a growing interest in integrating renewable energy based distributed generation (DG) in the electrical power distribution networks. The installation of DG units at distribution level impacts critically the planning and operation characteristics of the network. The type, location, number and capacity of the integrated DGs affects system behavior and performance. In this paper the effect of installing new DGs on the distribution network voltage stability is studied. The optimal location of the newly installed DGs are decided based on the Power Stability Index (PSI) and Voltage Stability Index (VSI). Moreover, Voltage Stability Margin (VSM) of the interconnected DG distribution network is demonstrated for different scenarios.
In this paper, a decentralized voltage control service for the distribution system operator (DSO) is proposed and a comparison with a centralized strategy, such as the conservation voltage control (CVR) technique is presented. The service is designed to provide short term power reserve to the grid and it implements a local voltage-led demand response. The proposed service manages residential units' power demand by regulating the household devices' main voltages in a local way instead of changing the secondary voltage of the medium voltage/low voltage (MV/LV) transformer. The proposed service allows having a wider voltage regulation range, overcoming the CVR limits due to voltage violations at the end of the feeders. In order to analyze the decentralized control impact in terms of maximum control range available on the LV distribution grid, a simulation set based on OpenDSS and MATLAB is carried out. The results are compared with those obtained by using the CVR technique in order to highlight the advantages provided by the proposed solution.
Current in series connected photovoltaic modules receiving different irradiance is limited by the module that receives the least irradiance. This reduces output power of PV array operating under partially shaded conditions as the module that receives higher irradiance do not operate at their maximum power point. Current compensation can be applied to all the modules to match the current of modules receiving different irradiance. With an aim to reduce the number of power converters required for current compensation, the paper presents an algorithm of current compensation for the Total- Cross-Tied ( TCT) configuration. The algorithm is simple to implement and requires less sensors. Simulation results obtained in MATLAB/Simulink are included to demonstrate the effectiveness of the proposed approach.
