The interfering nature of harmonics always causes various power quality issues that impacts on both efficiency, and expected transformer life. Optimal analysis of the three-phase core power transformers using harmonic spectrum can limit these power quality issues. This paper designs the Adaptive Neuro-Fuzzy Inference System (ANFIS) based model for the estimation of losses. Further optimal parameters selection of three-phase power transformer using iron and ferrite core materials. This paper demonstrates factors that deteriorate the power quality, responsible for harmonics distortions and inefficiency in power transformers. The proposed ANFIS based analysis provides an optimal solution to harmonic reduction and improves overall efficiency. Also, providing a comparative study of various core parameters that will be suitable for a three-phase core transformer. The proposed parameters are demonstrated for improving the overall transformer efficiency using iron and ferrite core material. ANSYS Maxwell simulation estimates the Total Harmonic Distortion (THD) and enhances THD in contributing to the optimal core material. The design of a three-phase power transformer and the performance evaluation of the proposed methodology performed in MATLAB simulation environment.
This paper presents a calculation algorithm, design assumptions and results of studies concerning a flue gas/water heat exchanger with the condensation of water vapor contained in flue gas from the combustion of brown coal. The algorithm was used for design calculations of a pilot-scale heat exchanger with capacity of 380/312 kW. A cross-counter flow heat exchanger with capacity of 312 kW and coils made of PFA (perfluoroalkoxy polymer) was designed and installed. Waste heat is recovered from flue gas produced by a pulverized brown coal fired subcritical steam boiler operated in a power unit with capacity of 370 MWe. The heat exchanger was theoretically divided into a non-condensing part (sensible heat recovery) and a part with the condensation of water vapor contained in flue gas (recovery of sensible and latent heat). The point of the division is the temperature of flue gas in the stream core (higher than near the pipe wall) where the condensation of water vapor occurs on the pipe surface. The heat transfer in the non-condensing part was calculated using the same formulas as for the economizer in a pulverized-fuel boiler, while the calculations of the heat and mass transfer in the condensing part were performed using the VDI algorithm. The results of the thermal calculations and the geometry of the heat exchanger together with the place of installation of the entire test rig are presented. The results of the calculation are then compared with the test results. Good correlation was achieved between the test results and the assumptions and results of the design calculations. Calculations for full scale exchanger for 370 MWe brown coal fired power unit showed a 1.18% net efficiency increase with improving wet flue gas desulphurization process (EUR 3.7 million annual savings of fuel consumption and CO2 emission).
Transitioning to renewable energy is part of the answer to, on the one hand, growing industrial development and the rising demand for energy and, on the other, environmental concerns and the need to preserve fossil fuel resources for future generations. This research focuses on the potential for integrating hydrogen storage into a highly reliable renewable energy system. The purpose of this study is to determine the potential of renewable energy in an Iranian location, in a project that looks at a power grid in various connected and disconnected scenarios involving hydrogen storage. The energy potential is identified: annual production capacity is 2218818 kW, requiring a total investment outlay of US$697,624.
Nuclear power plant process systems have developed greatly over the years. As a large amount of data is generated from Distributed Control Systems(DCS) with fast computational speed and large storage facilities, smart systems have taken over analysis of the process. These systems are built using data mining concepts to understand the various stable operating regimes of the processes, identify key performance factors, makes estimates and suggest operators to optimize the process. Association rule mining is a frequently used data-mining concept in e-commerce for suggesting closely related and frequently bought products to customers. It also has a very wide application in industries such as bioinformatics, nuclear sciences, trading and marketing. This paper deals with application of these techniques for identification and estimation of key performance variables of a lubrication system designed for a 2.7 MW centrifugal pump used for reactor cooling in a typical 500MWe nuclear power plant . This paper dwells in detail on predictive model building using three models based on association rules for steady state estimation of key performance indicators (KPIs) of the process. The paper also dwells on evaluation of prediction models with various metrics and selection of best model.
The drive system of a switched reluctance motor (SRM) is a nonlinear one with coupling between the rotor position, inductance, and flux linkage. Moreover, the system parameters change with the external environment such as temperature, humidity, and pressure. At the same time, uncertain factors including friction, torque fluctuation, and external interference in the system, reduce system stability and reliability. To effectively improve the influence of uncertain factors on the performance of an SRM system, this study proposes an auxiliary sliding position tracking method, under the condition of limited control input. First, the mathematical model of the system was established according to the structure and characteristics of an SRM. Second, an auxiliary sliding mode position tracking controller was designed by constructing the auxiliary system and utilizing the sliding mode control theory. Finally, the effectiveness and superiority of the proposed method were verified through comparison with proportional integral differential (PID) control and the traditional sliding mode control using simulation. Results demonstrate that under limited control input, the auxiliary sliding position tracking control method still delivers rapid and error-free tracking of the position and speed for the change of model parameters. The recommended scheme has a response time 2.9 times shorter than that of PID control. Furthermore, the steady-state errors of the PID control position and speed are 0.66 rad and 1.62 rad/s, respectively. The control input of the traditional sliding mode control has greater chattering than the proposed method. When the system has interference, the designed method under the condition of limited control input can achieve the desired tracking command within 1.7 s. The steady-state error is 0.0044 rad, and the steady-state accuracy of the developed scheme is 10.3 times higher than that of PID control. Therefore, the proposed method enjoys both high position tracking accuracy and strong robustness to external disturbances.
Energy generation systems basing on renewable energy sources (RES) are characterized with rapidly growing share of global power and heat market. Majority of such systems are suited to and applied within the distributed energy sector, including i.e. distributed heat production. Individual users and local low-power plants, using solar thermal devices to prepare domestic hot water, cold or support their heating network, state significant number between all users of discussed technology. Nevertheless, vital variability of solar irradiance makes it difficult to harvest efficiently, especially considering longer time periods, as months or years. Therefore, maximization of heat acquired from single solar thermal device in a moment of high radiation flux might vitally influence grow in overall, year-averaged operational parameters of such units. The paper discusses computational research on enhancement of convective heat transfer, taking place within the absorber of a parabolic trough collector (PTC), induced by vibrations of immersed flat plate. The investigation covers identification of influence of different amplitudes and frequencies of oscillatory motion on the absorber's parameters, as well as their comparison with classical absorber's construction and the other flow turbulization method. Results indicate limited application of vibrations to enhance operational parameters of solar thermal absorbers, with the best results obtained for thermal fluid flows below 0.1 dm 3 /s.
This article reports on an analysis of the possibility of storing thermal energy in a rock bed. The calculations were made in Ansys CFX 18.0 CFD. The analysis determined the charging time of a packed bed of granite rocks in variable flow conditions for the assumed geometry of the energy storage system. The model was 2-dimensional, consisting of two domains connected by an interface. The packed bed was modelled using a porous model approach. The inlet velocity was varied in the range 0.25-4 m/s. The total charging time was 70 to 1100 min, depending on inlet velocity.
Motor coolers are operated with the coupling of temperature and pressure fields, in which the change rule is affected by multiple factors. In this study, the thermal resistance of the motor cooler was examined using the velocity coefficient method to reveal the influence of heat transfer and wind resistance. The temperature and pressure fields were analyzed using the finite element method based on the hydrodynamics and momentum theorem. By varying the heat transfer and wind resistance coefficients to reflect temperature and pressure characteristics, wind and water velocities were determined. Results demonstrate that the total convective heat transfer and wind resistance coefficients of the cooler model are sensitive to variations in face-to-face wind velocity, but not to those of the cooling water flow rate. When wind velocity increases from 0.8 to 5.19 m/s, the total convective heat transfer increases by 1.85 times and wind resistance increases by 18.74 times. Variations in cooling water velocity has little effect on the Nusselt number on the air side and the Euler number of the single row tube, which are multiplied with the increase of the Reynolds number. When the Reynolds number increases from 1020 to 6345, the Nusselt number increases by 2.05 times and the Euler number decreases by 2.29 times. The results provide references for the design and performance testing of high-power motor coolers.
This paper describes a shunt active power filter for compensating harmonic currents and reactive power. The shunt active power filter(SAPF) was implemented with a phase pulse modulated current control voltage source inverter. The proposed system is based on PLL synchronization with reduced fuzzy logic controller (RD-FLC). These control techniques for SAPF prove that source current is sinusoidal even when load is non linear. The CC-VSI inverter switching is done according to gating pulse obtained from the hysteresis controller using RD-FLC controller. The proposed system is investigated using simulation results. The effectiveness of the controller is observed in the form of total harmonic distortion, reactive power compensation and settling time of dc link voltage under non linear load condition. This technology reduced the rules of fuzzy logic controller from 49 to 37.
The Montreal Protocol on ozone-depleting substances and the Kyoto Protocol to the United Nations Framework Convention on Climate Change are affecting the refrigeration industry. Both documents have banned the use of substances responsible for ozone depletion and global warming. The automotive industry must keep up with these changes. The design of cooling systems in cars must meet the requirements of new refrigerants. In addition, changing the production profile of large car companies towards electric and hybrid cars increases this need. This development has a significant impact on the solutions installed in passenger vehicles. The paper presents a critical assessment of R134a, R1234yf, and R744 in passenger car heat pump systems. The possibility of their use in common air conditioning systems with motor drive and in the heat pump of an electric vehicle was presented. The calculation algorithm of the heat pump system has been developed, showing the influence of the physical properties of refrigerants on efficiency during the process of the designed heat pump system. The impact of using new refrigerants in the car production process has been analyzed and commented on. The influence of thermodynamic and ecological properties of refrigerants on the process of designing a heat pump system using a calculation model was described. Types of heat pump in electric cars and a calculation model were presented.
To date no technical-economic-environmental review has been carried out on the use of hybrid wind-solar power plants in Japan. The study reported in this paper used HOMER software to analyze the electricity supply from renewable energy systems at 198 stations in Japan. The ranges of wind speed and solar radiation of the locations are 1.6-12 m/s and 2.7235.435 kWh/m(2)-day, respectively. The results show that the average, maximum and minimum use of renewable energy in Japan are 96.2%, 100% and 89%, respectively. Also, the average, maximum and minimum cost per kWh of energy are $ 0.434, $ 0.526, and $ 0.249, respectively. The cheapest wind turbine system (the cheapest renewable energy system), the cheapest solar system, the cheapest hybrid wind-solar system, and the most expensive hybrid system, have a price per kWh of energy $ 0.294, $ 0.349, $ 0.339 and $ 0.526, respectively. These systems are located at Fuji Mountain, Minamitorishima, Iwojima and Tokyo, respectively.
In this paper a modified space vector pulse-width modulation (SVPWM) technique for a three-phase T-type inverter is proposed that utilizes the state redundancies for fault-tolerant application. The performance of the T-type, 3-level inverter is analyzed with a three-phase induction motor load under the open-circuit fault condition of the inverter. The voltage space vectors of the three-level inverter under the open switch fault (open circuit fault) condition in any one leg of the three-phase inverter is analyzed and modified using the SVPWM adopted to overcome the problems of sudden stall at open switch fault conditions. Modelling and simulation of T-type 3-level inverter using proposed modified space vector pulse width modulation is carried out in the MATLAB/SIMULINK environment. The experimental results are presented here for verification of the simulation results using real-time simulator (dSPACE 1103).
The paper concerns the analysis of the combustion and exhaust emission phenomena in an SI (spark ignition) engine equipped with direct gasoline injection system for various injector placement parameters in the combustion chamber. Achieving a good combustion process is shaped by the direct fuel injection process, of which parameters vary. This article focuses on the aspect of injector spatial and angular position in order to perform injection and achieve fuel combustion. The injector's pseudo-optimal location has been presented along with several changed positions (27 configurations). The research was conducted as a simulation experiment using AVL FIRE software. The best injector position was selected based on the fuel atomization, injection and combustion process indicators. The pseudo-optimal location, was characterized by: 1) the largest inset in the combustion chamber: y = 7 mm, 2) the shortest distance from the spark plug: z = 9 mm, 3) the highest angle in relation to the axis of the cylinder: alpha = 20 deg. The analysis of this impact results in the following conclusions: 1) the longitudinal change of the injector position is the most important value affecting changes in the fuel atomization and combustion indicators, 2) this change is about 3 times more significant than the change in the position of the injector's distance from the axis of the spark plug and about 8 times more significant than the angle of the injector's position.
Research into the application of Electrical Capacitance Tomography (ECT) carried out in the Laboratory of the Aircraft Engines Division at Warsaw University of Technology has shown that it is applicable to recognition of various flames. Several cases were tested using the ECT system and the system successfully created cross sectional images of premixed and diffusion flames. Studies were then conducted which significantly increased the functionality of the system. This article describes experimental studies that afforded insight into the effects of the degree of ionization generated during the combustion process on the changing signal of the ECT system. Research was carried out in an experimental stand consisting of a burner, 6 and 12 electrodes capacitance sensors and an optical spectrometer. Burner injection was used to obtain stability of combustion. Two rotameters were installed in the inlet of the burner. The flow rate of air and methane was used to determine the composition of the combustible mixture formed in the mixing chamber. A grating spectrometer was used to perform a detailed analysis of combustion processes and to detect various types radicals. This experimental test focused on measuring chemiluminescence intensities and possible correlations of the OH*, CH*, C-2* and H2O with air/methane ratio. The data from the ECT system and optical spectrometer was then analyzed. It was found that the strong correlations between the peak intensity of OH*, CH*, C-2* and H2O in the reaction zone to the equivalence ratio could be used to investigate the local flame stoichiometry.
This paper sets out the results of experiments for falling film at Re-w = 70 ... 340 in the vertical channel of two coaxial tubes, (empty set) 37/17 mm, 1 m high, for a countercurrent air flow with Re-air = 2200 ... 10(4). Subject to investigation was falling film on smooth and capillary-porous wall surfaces at constant film thickness greater than the height of the capillary-porous coating (0.3 mm). It was established that film thickness is weakly dependent on the velocity of the countercurrent airflow at w (air) = 1.7 ... 7.3 m/s. The water concentration on a smooth surface is 2 times higher at the same film thickness. The results of flooding in a channel with a smooth wall surface confirm the validity of the Wallis equation with deviation up to 20%.
Users of fossil fuels are facing a range of challenges such as long-term rising demand, climate concerns due to emission of greenhouse gases, ecological pollution, finite reserves and price fluctuations. Diesel fuel is similarly affected, though with its own subset of issues. Studies suggest that diesel fuel characteristics are affected by addition of nanoparticles. In this research, carbon nanotubes (CNTs) were blended with pure diesel as an additive at concentrations of 30, 60, and 90 ppm to assess the emission and performance characteristics of a single-cylinder compression combustion engine. The considered emission contents included CO, CO2, HC, and NO produced by an engine at 50% and 100% loads, at 1800, 2300, and 2800 rpm. Addition of CNTs to the diesel fuel considerably reduced the emission of CO, CO2, HC, and NO compared to additive-free diesel fuel. Furthermore, with the addition of carbon nanotubes, the Exhaust Gas Temperature (EGT) and the Brake Specific Fuel Consumption (BSFC) decreased, while the power and Brake Thermal Efficiency (BTE) increased at all loads and speeds of the engine.
We present in this paper a novel DTC-SVM scheme for a Dual Star Induction Motor fed by two 3 levels inverter with NPC structure, this type of inverter has many points of interest in comparison with the conventional 2 levels inverter, such as: sinus waveforms of the output voltage, low THD of voltage and current and low switching frequency. Also, we present in this article an improved direct power control with virtual flux (DPCVF-SVM) for the control of three phase rectifier. It is shown that the DPC-SVM presents several advantages: constant switching frequency, good dynamic response, sinusoidal line currents ... etc.
With the rapid development of new energy power generation, large-scale wind power generation has been integrated into power grids. However, the fluctuation and discontinuity of wind power pose challenges to the safe and reliable operation of power systems. Therefore, constructing a reasonable dispatching method to manage the uncertainty of wind power output has become an important topic and this study was structured with this precise aim in mind. An ellipsoidal robust set of wind power outputs was initially constructed in accordance with the predicted value and predicted error of wind power. Second, a power system optimization dispatch model of automatic generation control (AGC) was established on the basis of the robust set. This model aimed to minimize the cost of power generation and maximize the use of wind power according to the following constraint conditions: power system power balance, upper and lower limit of wind and thermal power unit outputs, climbing power, and spinning reserve. Finally, the internal point method was employed to solve the example. Results show that, on the premise of safe operation, the total operating cost of the robust optimization dispatch method is decreased by 8.64% compared with that of the traditional dispatch method, and economic efficiency is improved. Robust optimal dispatch factors in the uncertainty of wind power output meaning the load shedding scenario seldom occurs, thereby enhancing operational reliability. This study can be used to improve the reliability and economics of power system operation and provide a basis for optimizing dispatch in power systems.
There are advantages to be gained by using a generalized method of data validation and reconciliation in energy conversion processes in terms of decreasing the uncertainty of measurements data. This method was used to complete the validation model of the process (conditional equations of optimization task) including substance and energy conservation principles with additional equations describing energy conversion processes. The methodology developed was used for example for calculations of data reconciliation in the selected steam power unit. The equations of steam flow capacity, adiabatic internal efficiency and equations resulting from the form of an isobaric line on the h-s diagram for a group of turbine stages were applied. Also applied as additional equations in the validation model were: Darcy's equation of steam pressure drop in the pipeline into heat exchangers and Peclet's equations of heat transfer and equations of over-cooling of condensate in regenerative heat exchangers. The criterion of an assessment of the decrease of measurements uncertainty in the form of global decrease of measurements variance after measurement data reconciliation is proposed. Derivation of the analyzed coefficient was based on the characteristic property of the measurements variance, coming from the variance-covariance matrix of measurements before and after data reconciliation. The criterion for selection of the mathematical form of additional equations in the validation model in reconciliation calculation was formulated. Professor Jan Szargut introduced and developed the advanced data validation and reconciliation method in Poland for thermodynamic analysis of energy conversion processes. The author of this paper engaged in further research on the development and application of this method in thermodynamic analyses.
Charging electric vehicles (EVs) represents an extra and increasing load for the power system. And the higher the charging power is, the more likely it is that serious problems will arise. In addition to home charging, in Hungary - the area of interest in this paper - Level 2 chargers in the streets are currently installed with a maximum charging power of 22 kW. Since the local market share of EVs is low at present and expected to remain relatively low in the years to come, it is essential to see where the limits of the low-voltage distribution grid are in terms of taking the extra EV charging load. This paper presents extensive simulation results taking various EV charging characteristics, arrival statistics, household load variation, and other assumptions into consideration to determine how EV charging will affect the low voltage grid. The stochastic simulations were conducted in DIgSILENT Power Factory augmented with a Python code. Simulation results indicate that an already moderately loaded grid is capable of accommodating EVs at a penetration level of approximately 20%, which can be considered a high value.
