Maximum Power Load Research Articles

Automated electrical demand peak leveling in a manufacturing facility with short term energy storage for smart grid participation

Demand side management of energy is a vital function in the smart grid that allows for greater integration of renewable energy resources, and is facilitated with economic incentives in energy and demand pricing schedules. Manufacturing systems can take advantage of these incentives to reduce their energy costs through active energy management. This paper is a simulation analysis on the implementation of a novel algorithm that levelizes the maximum power load of an industrial bakery that operates under an on-peak demand price structure. The algorithm takes advantage of an untapped thermal energy storage resource in the facility, a chilled glycol buffer tank, to level the short intra-day power oscillations that the facility experiences. One of the key advantages of the algorithm is that it does not require precise demand forecasting or complex control algorithms, such as model predictive control. Even with substantial error in peak power estimates (5%), the algorithm is expected to result in at least a 2% peak reduction. Under ideal prediction, the algorithm reduces the on-peak facility power maximum by 7.3% of the possible 9.0% reduction the storage can provide. Further, the algorithm uses very few facility specific inputs, and can readily be adapted for any facility with short intra-day oscillatory power profiles and untapped storage capacity. The key insight of the paper is the employment of a novel algorithm to leverage untapped energy storage in manufacturing facilities to transform them into smart grid participants with no major capital investment.

Optimal range of loading for operating a fixed-speed wind turbine using a self-excited induction generator

In the present study, a new strategy of analysis was used to determine the optimal interval of a single-phase resistive load to operate a fixed-speed wind turbine. The essence of this optimal range is to enable the generator to have stable voltages and current balances, large power, and an acceptable frequency range, and also mitigate generator overheating. The generator windings and excitation capacitances were prepared according to the C-2C connection scheme with suitable values of excitation capacitances. The admittance matrix of the system was based on positive and negative sequence generator voltages and was calculated by symmetrical components theory. The generator performance was found through optimization of the determinant admittance matrix magnitude. Moreover, balanced position of the generator can be achieved near the maximum load power. Consequently, the best interval of resistive load of the generator (1.5 kW) was found around 2% voltage unbalance factor. The appropriate optimal load was approximately ±6% of the perfect balance resistive load value.

A Maximum Power Loading Factor (MPLF) Control Strategy for Distributed Secondary Frequency Regulation of Islanded Microgrid

Microgrids rely on both primary and secondary frequency control techniques to maintain system stability. Secondary frequency control effectively minimizes frequency fluctuations by adjusting the active power reference in each power inverter, but requires complex and costly interequipment communication. In this paper, we propose a distributed secondary frequency control strategy for microgrids containing multiple virtual synchronous generator (VSG) units based on a new maximum power loading factor (MPLF) concept. The MPLF algorithm facilitates power sharing by dynamically identifying the maximum VSG loading factor at each time instance, and then using this value as a unified reference signal for all the VSGs in the microgrid. The active power reference for each VSG will be adjusted based on the unified reference signal, subsequently the secondary frequency control can be realized. The proposed strategy does not require high-bandwidth communication since the MPLF data are transmitted among the VSGs using low-bandwidth communication. We also develop small-signal models for the control architecture to analyze the influence of major proportional–integral control parameters and communication latency. The MPLF control strategy is implemented using custom digital signal processor controllers, and experimentally validated using hardware in loop simulations. Finally, the new control paradigm demonstrates significant tolerance for communication delay or failure, which we purposely introduced in our investigation.

Provincial Grid Investment Scale Forecasting Based on MLR and RBF Neural Network

Accurate calculation of power grid investment scale is an important work of power grid management. It is very important to power grid efficient development. Due to the characteristics of short data time series, lots of influencing factors, and large change of power grid investment, it is very difficult to calculate grid investment accurately. Firstly, this paper uses hierarchical clustering analysis method to divide the 23 provinces into four classes with considering fifteen power grid influencing factors, then uses spearman’s rank-order correlation to find out five key influencing factors, and then establishes the regression relationship between the growth rate of investment scale and GDP, permanent population, total social electricity consumption, installed power capacity of operation area, maximum power load, and other growth rates by using the multiple linear regression method (MLR), and the estimation error is corrected by using RBF neural network. Finally, the validity of the model is verified by using data related to power grid investment. The calculation error indicates that the model is feasible and effective.

Powertrain control of a solar photovoltaic-battery powered hybrid electric vehicle

This paper proposes a powertrain controller for a solar photovoltaic battery powered hybrid electric vehicle (HEV). The main objective of the proposed controller is to ensure better battery management, load regulation, and maximum power extraction whenever possible from the photovoltaic panels. The powertrain controller consists of two levels of controllers named lower level controllers and a high-level control algorithm. The lower level controllers are designed to perform individual tasks such as maximum power point tracking, battery charging, and load regulation. The perturb and observe based maximum power point tracking algorithm is used for extracting maximum power from solar photovoltaic panels while the battery charging controller is designed using a PI controller. A high-level control algorithm is then designed to switch between the lower level controllers based on different operating conditions such as high state of charge, low state of charge, maximum battery current, and heavy load by respecting the constraints formulated. The developed algorithm is evaluated using theoretical simulation and experimental studies. The simulation and experimental results are presented to validate the proposed technique.

Optimal Operation of Isolated Microgrids Considering Frequency Constraints

Isolated microgrids must be able to perform autonomous operation without external grid support. This leads to a challenge when non-dispatchable generators are installed because power imbalances can produce frequency excursions compromising the system operation. This paper addresses the optimal operation of PV–battery–diesel-based microgrids taking into account the frequency constraints. Particularly, a new stochastic optimization method to maximize the PV generation while ensuring the grid frequency limits is proposed. The optimization problem was formulated including a minimum frequency constraint, which was obtained from a dynamic study considering maximum load and photovoltaic power variations. Once the optimization problem was formulated, three complete days were simulated to verify the proper behavior. Finally, the system was validated in a laboratory-scaled microgrid.

Energy Management and Coordinated Control Strategy of PV/HESS AC Microgrid During Islanded Operation

An energy management control strategy is proposed for an islanded AC microgrid with the hybrid energy storage system, including the battery and the supercapacitor (SC). According to the state of charge of the battery, the photovoltaic system can work in either maximum power point tracking mode or load power tracking mode to prevent the battery from over charging. Similarly, the load shedding control is adopted to prevent the battery from over discharging. A virtual impedance control strategy is proposed to achieve effective power sharing in hybrid energy storage systems, where the battery provides steady state power and the SC only supports transient power fluctuations. The terminal voltage of the SC can be restored to the initial value automatically by introducing a high-pass filter in the voltage control loop. The AC bus voltage remains constant using the voltage secondary controller to compensate the voltage drop caused by the virtual impedance control strategy. The simulation results under typical working conditions verify the correctness and effectiveness of the proposed control strategy.

Analysis of the implementation of microgrid: case study of wide-area Bjelimići

Microgrids are increasingly put forward as key concepts of future energy supply, complementing as well as transforming the conventional, centralized energy system. Here, the aim was to construct microgrid composed of wind and solar power plants, diesel generator and battery storage which will be independent of a large, centralized electricity grid and incorporate more than one type of power source so to supply Bjelimici area. This area is taken as a case study since it has large potential considering the renewable energy sources and because this feeder is quite long which makes energy losses considerably higher. All material which were used in this project consist of real network parameters which are provided by Public Electric Utility Elektroprivreda of Bosnia and Herzegovina. For completing the project, DIgSILENT PowerFactory software (base package and Quasi-Dynamic Simulation Toolbox), HOMER (Hybrid Optimization Model for Multiple Energy Resources) software and Microsoft Excel were used. System has been modeled using minimum total cost of investment as a goal for optimization function and to cover the maximum power load with battery storage and diesel generators. Therefore, appropriate installed power of wind, solar and diesel power plants in combination with battery storage, based on real energy resource data and real load profiles of existing customers, has been chosen. In the end, using obtained data from HOMER for model in DIgSILENT PowerFactory, power flow, voltage profiles, line and transformer loading, and total grid losses were analyzed. It has been concluded that microgrids should be considered as excellent solution for such and similar areas, especially when considering the construction or significant upgrading of networks. Also, results from DIgSILENT PowerFactory have proved that system can operate with modeled microgrid. In addition, it is shown that better conditions of the network are present when operated in the island mode.

The Effects of Two Different Resisted Swim Training Load Protocols on Swimming Strength and Performance.

This study used a power rack device to evaluate the effects of 2 different approaches to resisted swim training loads on swimming strength and performance. Sixteen male, youth national-level swimmers (mean age, 16.22 ± 2.63 years; body height, 169 ± 10.20 cm; body mass, 61.33 ± 9.90 kg) completed a 6-week specific strength-training program, and were then randomly assigned to one of the two groups: a standard training group (GS, n = 8) and a flat pyramid-loading pattern group (GP, n = 8). Strength and power tests along with specific swimming tests (50-m crawl and 50-m competition-style time trials) were conducted at baseline (pre-test), before the third week (mid-test), and after 6 weeks of intervention (post-test). Isokinetic swim bench tests were conducted to obtain measurements of force production and power, and 1RM tests with the power rack system were conducted to measure the maximum drag load (MDL) and specific swimming power. Following 6 weeks of intervention, the mean MDL increased (p < 0.05) by 13.94%. Scores for the 50-m competition style and 50-m crawl time trials improved by 0.32% and 0.78%, respectively, in the GP; however, those changes were not statistically significant. The GS significantly increased their time in the 50-m competition style by 2.59%, and their isokinetic force production decreased by 14.47% (p < 0.05). The 6-week strength-training program performed with the power rack device in a pyramidal organization was more effective than a standard linear load organization in terms of producing improvements in the MDL; however, it did not produce significant improvements in performance. The use of a strength-training program with a pyramidal organization can be recommended for specific strength-training in young swimmers during a preparatory period. However, in our study, that program did not produce significant changes in 50-m crawl and main competition style performance.

Effects of Observer's Mental State on Mirror Neuron System Activity

Recently, electricity demand is increasing drastically compared to electric power supply. In particular, this trend is due to the demand for heating in winter, leading to the electricity peak consumption at any time of the day. In this study, a new heat pump system is proposed to address the imbalance between power supply and demand solving the electricity soaring problem. The suggested heat pump system uses thermal energy storage and discharge concept that is capable of continuous heating operation simultaneously. In order to demonstrate the effectiveness of such a system, the dynamic performance change of the system was investigated by experimental study. From the results, it was shown that the performance of heat storage system was varied according to refrigerant mass flow rate branched to the heat storage tank. Furthermore, it was confirmed that the performance was reduced during the heat storage operation process, and it was improved during the discharge operation process. The overall performance is reduced taken as a whole, but it is meaningful that it disperses the electricity peak. As a result of this study, it is expected that the new thermal storage heat pump system can reduce the maximum power load.

Energy management for thermoelectric generators based on maximum power point and load power tracking

Thermoelectric generators (TEGs) can be widely applied to directly convert thermal energy into electricity. Herein, we propose an energy management system for TEGs to achieve efficient energy storage and use. Specifically, we consider both the generally unstable power generation given the variable temperature difference between the hot and cold sides of TEGs and the variable load that requires the inclusion of a storage unit consisting of a battery and supercapacitor for improving the system performance. The supercapacitor mitigates energy fluctuations and reduces transients in the bus voltage, and the battery acts as a backup energy source, storing energy and delivering electricity when the load power demand is high. In addition, we propose a novel threshold control strategy based on the bus voltage intervals for the energy management system that incorporates maximum power point tracking (MPPT) and load power tracking (LPT) to maintain energy balance among the system units. MPPT aims to provide an efficient collection of thermal energy, and LPT based on fuzzy logic is used to maintain a stable bus voltage when the DC load power demand is low. The experimental results verify that the proposed LPT approach regulates the evaluated variations in DC load power with an average error of 3.5% and that the energy management properly operates under variable load power and battery state of charge.

Temperature-Robust Air-Gapless EE-Type Transformer Rails for Sliding Doors

In this paper, a sliding EE transformer (SEET) rail, which has a strong and independent magnetic coupling to the gap variation between the transmitter (Tx) line and receiver (Rx) coil for powering the sliding door, is newly proposed. In the SEET rail, the Tx line and the Rx coil share a single EE ferrite core, while the winding window of the ferrite core is considered as the gap variation. In the proposed structure, the magnetic coupling can be maintained as strong and constant even though the ferrite core moves along the door rail when the sliding door is closed or opened. Through detailed coil designs based on electric and magnetic circuit analyses, design constraints on voltage, output power, flux density, and zero voltage switching are proposed with a closed-form solution of output voltage and theoretical maximum output power. The SEET rail is successfully designed to provide a maximum load power of 200 W for the sliding door within an ambient temperature range from −40 to 125 °C by following design constraints. Moreover, optimal design parameters such as number of turns, air-gap, and ferrite thickness are provided, which maximize power transfer efficiency of the SEET rail while maintaining its performance in the temperature range. The proof-of-concept prototype shows a strong magnetic coupling, κ = 0.76 at 20 °C and the variation of the magnetizing inductance with respect to the temperature variation was measured as 13.8%. The maximum power transfer efficiency excluding the regulator at a nominal load power of 100 W was 85%, and the efficiency at the maximum load power of 200 W was measured as 82% with a 3%P variation by the temperature variation.

ФУНКЦИОНАЛЬНОЕ СОСТОЯНИЕ ПОДРОСТКОВ ПРИ ПОЗНАВАТЕЛЬНОЙ ДЕЯТЕЛЬНОСТИ В ЗАВИСИМОСТИ ОТ УРОВНЯ АЭРОБНОЙ МОЩНОСТИ

Aim. The aim of this article is to reveal the features of functional state in adolescent school students characterized by the high and low level of aerobic power development. Materials and methods. We examined 162 male pupils aged 13–14 belonging to the main medical group. We used a variety of indicators characterizing physiological, psychological and behavioral aspects of the functional state of the body. As informative integral indicators of the maximum power of aerobic process we used maximum oxygen consumption, PWC170 test and load power with a maximum time for the load performed of 900 sec (W900). As a result of statistical processing we divided all participants from the sample studied into 3 groups depending on the level of aerobic capacities of the body. Results. The results obtained demonstrate that the functional state of adolescents aged 13–14 significantly depend on the development of aerobic capacities of the body. We established that boys with a powerful aerobic system of energy supply differ from untrained peers by the decreased activity at quiet wakefulness and less pronounced changes in vegetative indicators of functional state under intense cognitive load against a high adaptation potential of the body. They are characterized by the increased effectiveness of the activity combined with the high scores of well-being, activity and mood assessment. Conclusion. The level of aerobic power can be considered as a factor determining the changes in adolescents’ functional state under intense cognitive load.

The Power Load on Kinematic Pairs of Tractor Variable Base Mechanism

Both longitudinal and transverse stability as well as maneuverability and controllability are important parameters of the tractor for efficient processing of land areas in mountainous and foothill areas, which surface has significant irregularities, and are often located under large bias. It is known that in order to ensure the stability of the tractor, its base must be maximum, and to ensure a minimum turning radius – minimum. However, the design used in the agro-industrial complex of the Republic of Uzbekistan 4-wheel universal tractors does not provide a mechanism for changing the wheelbase. In this regard, SDB Tractor designed 4-wheeled universal tractor, equipped with a special mechanism that changes the base of the tractor by 670 mm. It is showed that the reliability of the mechanism depends primarily on the strength of the parts, which account for the maximum power load. (Purpose of the study) We investigate the force loads acting in kinematic pairs of the alternation mechanism of the tractor base. (Materials and methods) The possibility of changing the parameters of the tractor base is showed on the example of the 3D model. To calculate the parameters of the designed tractor came from the figures: weight per axle; the dimensions of the hinge parallelogram arrangement; the radius at which the moving end of the rod of the hydraulic cylinder; a rolling resistance of the front wheels on the supporting surface of the concrete cover, etc. (Results and discussion) Power loads in kinematic pairs of the tractor base change mechanism were determined on the basis of generally accepted methods of the theory of mechanisms and machines with the use of structural analysis of the mechanism. The magnitude of the forces acting at each kinematic pair of mechanism for database changes, calculated by the graphical-analytical method on the basis of the law of statics using conditions of equilibrium. (Conclusions) It is found that the values of forces acting in the hinges of the mechanism of changing the base of the tractor range from 8816.25 H to 93255.82 H. On the basis of the calculations presented the following results: the greatest efforts in the links of the mechanism of change of the tractor base act in their longitudinal direction, which should be taken into account when one determines the parameters of the mechanism of change of the tractor base and the calculations of parts for strength.

Experimental study on the performance of multi-split heat pump system with thermal energy storage

Recently, electricity demand is increasing drastically compared to electric power supply. In particular, this trend is due to the demand for heating in winter, leading to the electricity peak consumption at any time of the day. In this study, a new heat pump system is proposed to address the imbalance between power supply and demand solving the electricity soaring problem. The suggested heat pump system uses thermal energy storage and discharge concept that is capable of continuous heating operation simultaneously. In order to demonstrate the effectiveness of such a system, the dynamic performance change of the system was investigated by experimental study. From the results, it was shown that the performance of heat storage system was varied according to refrigerant mass flow rate branched to the heat storage tank. Furthermore, it was confirmed that the performance was reduced during the heat storage operation process, and it was improved during the discharge operation process. The overall performance is reduced taken as a whole, but it is meaningful that it disperses the electricity peak. As a result of this study, it is expected that the new thermal storage heat pump system can reduce the maximum power load.

Investigation of thermoelectric generators connected in different configurations for micro-grid applications

This research work investigates the power-current (P-I) and voltage-current (V-I) characteristics of the thermoelectric modules (TEMs) in series-parallel configurations under homogeneous and heterogeneous temperature difference (ΔT) condition. To study its performance, 5 different series-parallel combinations were formed using 16 TEMs. The comparisons among the different configurations have been done to determine the optimal series-parallel configuration. The total load power extracted from 16 individually connected TEMs was 18.2 W, which was placed as a reference load power. The optimal series-parallel combination for maximizing the load power is square series-parallel configuration, whose maximum load power is 95.5%, compared to the reference load power. Moreover, in square series-parallel configuration, the total internal resistance value that remains constant is equal to the internal resistance of a single TEM, and the total open-circuit voltage increases gradually on adding any number of TEMs. Thus, it produces higher load voltage and higher load current simultaneously, which is recommended to power DC micro-grid applications. Furthermore, the series, parallel, and square series-parallel configurations are connected as star to obtain 3 separate DC output to power the same application. The performance of TEMs under various configurations is analyzed, and the obtain results are verified experimentally.

Stability Analysis and Stabilization Methods of DC Microgrid With Multiple Parallel-Connected DC–DC Converters Loaded by CPLs

Constant power loads may yield instability due to the well-known negative impedance characteristic. This paper analyzes the factors that cause instability of a dc microgrid with multiple dc–dc converters. Two stabilization methods are presented for two operation modes: 1) constant voltage source mode; and 2) droop mode, and sufficient conditions for the stability of the dc microgrid are obtained by identifying the eigenvalues of the Jacobian matrix. The key is to transform the eigenvalue problem to a quadratic eigenvalue problem. When applying the methods in practical engineering, the salient feature is that the stability parameter domains can be estimated by the available constraints, such as the values of capacities, inductances, maximum load power, and distances of the cables. Compared with some classical methods, the proposed methods have wider stability region. The simulation results based on MATLAB/simulink platform verify the feasibility of the methods.

X-Ray Powder Diffraction: Why Not Use CuKβ Radiation?

CuKβ radiation with a wavelength of λ = 1.3923 ? is recommended for crystal structure determination from X-ray powder diffraction using the Rietfeld method. A highly sensitive image plate detector is able to collect enough intensity to record a brilliant X-ray powder pattern in a reasonable time, compared to CuKα1 radiation used today. Especially atomic displacement coefficients could be determined more precisely with the much greater number of reflections recorded. A double-radius Guinier camera attached to a micro-focus rotating anode tube ensures increased brilliance besides high resolution. A simple construction specification is presented to make smart cylindrically bent Ge(111) or Si(111) X-ray monochromators that deliver focused CuKβ radiation. The highly linear response of image plate detectors allows removing of fluorescence radiation simply as background of the pattern. The proposed equipment is a cost-efficient alternative to a liquid gallium-metal-jet X-ray source with maximum power load and a similar wavelength of λ(GaKα1) = 1.34013 ?.

Thermal modeling of a novel rotary engine

Studies on rotary engines and their high operation efficiency, in comparison with reciprocating-piston engines, has encouraged further research on different types of these engines. This paper focuses on thermal analysis of a novel rotary engine with 24 combustion processes per rotation. This engine has only two moving parts, the vanes and the rotor. Two cams operate as stationary parts. The modeling, based on maximum power and full load operation, evaluates approximately the thermal behavior of the engine running with diesel fuel and a compression ratio (20:1). Initially, by presenting a thermodynamic model, pressure, temperature and convective heat transfer coefficient of combustion gases inside one cylinder of the engine are calculated; results obtained from the model are used as boundary conditions for adjacent control volumes and thereafter steady-state temperature distribution in the engine components are obtained using the commercial software Ansys. With regard to material limitation, the resulting temperature distribution shows that the cam needs an auxiliary cooling system, while the rotor and the vanes cool down using the lubrication oil of the engine. Finally, it is suggested that cooling such as air or water is needed for the cooling of the cam, as an auxiliary cooling system.

An omni-directional kinetic energy harvester using a novel spherical Halbach array transducer

A spherical electromagnetic energy harvester is designed to harvest omni-directional kinetic energy. A novel spherical Halbach array is proposed, which increases the magnetic field gradient in the coil compared with the traditional permanent magnet array, to increase the output performance. The parameter optimization of the spherical structure is carried out in accordance with the analytical results of the corresponding physical model. Finite element analysis and experimental performance test are carried out on the prototype. Experimental results demonstrate that the novel transducer can harvest kinetic energy in any direction, and then transfer to electric power. When the excitation direction is horizontal with frequency of 7.5 Hz, the load resistance is 3.2 Ω, the electric power reaches its maximum value. The maximum load power of a single coil is 0.18 mW. It can meet the needs of some microelectronic devices and has the potential to take the place of chemistry batteries and supply power to wildlife monitoring and positioning systems.