Variable Power Research Articles

Maximum Power Control of DFIG Based Grid Connected Wind Turbine Generator System

This paper presents a simulation model of variable speed wind turbine with a doubly fed induction generator developed in Matlab/simulink. Vector control of a doubly fed induction generator (DFIG) drive for variable speed wind power generation is described. A slip ring (wound rotor) induction generator with back to back three phase PWM converter between its rotor and the grid forms the electrical system. A vector control scheme for the PWM converters results in independent control of active and reactive power. Line (supply) voltage oriented reference frame has been used to independently control the active and reactive power. Results are provided at the end for sub synchronous and super-synchronous operation of the DFIG.

A performance comparision between brush and brushless doubly fed asynchronous generators for wind power systems.

This paper presents dynamic modeling and simulation of Brushless Doubly Fed Induction Generator (BDFIG) as an alternative for variable speed wind power applications. The mathematic models of active and reactive power for BDFIG have been developed. The power control systems of a 75 kVA generator and wind turbine were simulated in Matlab/Simulink/SymPower Systems. The generator’s control system is based on vector control principles which enable to decouple active and reactive power control. The BDFIG performance is compared to a wound rotor doubly fed induction generator. The power flow in the two generators systems and in the grid is analyzed and compared. The efficiencies of the two systems are compared.

Using ultracapacitors in photovoltaic systems. A technical proposal.

none

Performance of the distribution network by connecting solar and wind DGs

The operation of the distribution network (DN) is difficult due to the voltage stability when connecting multiple distributed generations. This paper explains the performance of a distribution network by connecting solar and wind Distributed Generation (DG). The distribution network is stable when the voltages are within the boundary limits. The voltage boundary limits are 0.95< 1 < 1.05 per unit. The voltages and power loss of the IEEE-85 and 25 bus radial distribution networks are evaluated by connecting Solar Distributed Generation (SDG) with variable power supply due to changes in the irradiation of solar panels. The voltages and power loss of the IEEE-85 bus distribution network are evaluated by connecting Wind-Distributed Generation (WDG) with variable power supply due to wind speed changes, and voltages and power loss are evaluated with load changes in the presence of WDG. By connecting both solar and wind-distributed generations, the voltages and power loss of the IEEE-85 bus DN are evaluated. The Multi-Objective Slime Mould Algorithm (MOSMA) is used to connect solar and wind DGs at optimal locations and sizes in the DN. The MOSMA has been applied to the IEEE-85 bus and 25 bus DN in MATLAB.

Exponential fast terminal sliding mode based finite-time control of manipulator systems

A finite-time controller is designed based on an exponential fast terminal sliding mode for multi-joint manipulators, which solves the problem of slow convergence in trajectory tracking. By adding an exponential function on the basis of fast terminal sliding mode, the convergence speed is greatly improved. In addition, a new fast variable power reaching law is designed to reduce the chattering problem. The approaching speed is adjusted by changing the size of the power term adaptively in different stages of the approximation, so that the states of the system enter the sliding mode surface faster and more stablely. The controller realizes the finite-time trajectory tracking of the manipulator, shorens the convergence time and weakens the chattering frequency. Finally, the above views are verified by simulation and comparison experiments.

A Comprehensive Review on Matrix-Integrated Single-Stage Isolated MF/HF Converters

A matrix-integrated single-stage isolated MF/HF AC-AC/DC-AC/AC-DC converter topology stands out as an innovative concept, offering a multitude of advantages including minimal output current THDs, near UPF, 4Q operation, smooth BPF capability, and increased power density leading to the converter’s enhanced efficiency, cost-effectiveness, and reliability. These characteristics render it an exemplary choice for RE-based power conversion applications. In fact, the matrix-integrated single-stage isolated MF/HF converters have witnessed an increased adoption of RE-based grid interconnection in recent years, specifically within solar PV, WECS, grid-tied offshore WF, and FC-based applications. RE sources produce variable and intermittent AC power by nature, further necessitating conversion to a stable and grid-compatible AC voltage and frequency. This is where MCs offer distinct advantages when contrasted with the conventional indirect dual-stage VSC-based rectifier–inverter topology. In this paper, a total of 22 matrix-integrated HF isolated converter topologies are broadly explored. Our study provides a comprehensive analysis and classification of matrix-integrated isolated single-stage MF/HF AC-AC converters, DC-AC inverters, and AC-DC rectifier topologies including modified topology architectures, control method, modulation techniques along with significant applications. Within this scope, the matrix-integrated converter topologies are categorized based on their architectures and other relevant subvariants. Our primary objective of this study is to impart a clear understanding of the overarching framework and principles of the matrix-integrated single-stage isolated MF/HF converter topologies and stimulate the creation of new topologies that cater to specific requirements for grid-interconnected systems.

Fuzzy Logic Based Adaptive P&O MPPT Control of a DC-DC Boost Converter Used in a Wind Energy Conversion System with a Permanent Magnet Synchronous Generator

In this paper, we present a Maximum Power Point Tracking (MPPT) algorithm employing Perturb and Observe (P&O) using Fuzzy Logic (FL) control to overcome limitations associated with the conventional P&O MPPT method in order to improve transient response and reduce steady-state terminal voltage oscillations. In particular, the FL approach was applied to define the perturbation amplitude for the P&O MPPT algorithm, according to the ratio between the incremental power and incremental voltage in the input of a DC-DC boost converter. The approach was a variable speed wind power conversion chain based on the permanent magnet synchronous machine. The MPPT control continuously adjusts the duty cycle of the DC-DC converter to maintain the wind turbine at the maximum power point. MATLAB-SIMULINK environment is used to simulate the entire system demonstrating the extraction of the maximum available power from the wind turbine under a varying wind speed.

Machine learning guided adaptive laser power control in selective laser melting for pore reduction

An adaptive laser power control strategy for Selective Laser Melting (SLM) has been developed using data from a co-axial photodiode monitoring system with 200 KHz temporal resolution. A supervised machine learning based algorithm outputs variable laser power along the scanning path based on mechanistic features. The approach was implemented on a commercial machine and demonstrated an average 12 % reduction in porosity size and 65 % reduction in the standard deviation of porosity size measured by X-Ray Computed Tomography (CT) compared to parts built with constant laser power. This approach is scalable and its precalculated nature is compatible with regulatory concerns.

Advanced Control Strategy of Switched Reluctance Generator-Based Wind Energy Conversion Systems Using Backstepping and Extremum Seeking Techniques

Switched reluctance generators (SRG) become increasingly competitive with other electrical machines due to their design, which includes only a stator winding. The SRG are known for their reliability and capacity to operate over a wide speed range, these generators find significant use in variable wind power plants. The main limitations of these machines are torque fluctuation and relatively low efficiency. In this respect, the aim of this work is to mitigate these drawbacks. Presently, an extremum seeking online method has been developed, and a backstepping controller is designed for SRG-based wind energy conversion system (WESC) connected to the grid via a VSC converter. One of the main objectives of the proposed controller is to achieve the optimum rotation speed of the turbine and to regulate the SRG for tracking the maximum power point (MPPT) while minimizing torque ripple via Direct Instantaneous Torque Control (DITC). To show the efficiency and performance of the proposed controllers, simulation examples of the proposed controllers are established using MATLAB/SIMULINK tools. The simulation results show that the efficiency and performance of the system using the proposed controller are significantly improved.

Research on the distribution of heat fluxes during infrared drying of grain material

Purpose. To develop mathematical models of unsteady heat and mass transfer during the infrared (IR) drying process, and to create an algorithm for calculating the variable power of IR energy input to ensure quality drying of thermolabile material. Methods. The methods of mathematical modeling used to describe the unsteady drying process of thermolabile material in a dryer are based on the formalized description in the form of nonlinear inhomogeneous differential equations, taking into account the change in the power of IR energy input during the drying process. Results. A dependency for calculating the perceivable power of the IR source by the grain, based on the given process mode parameters, has been obtained. The drying kinetics of the grain, derived from formula (10), more accurately characterizes the process from a physical point of view than the drying equation (8) with a constant coefficient kck. It was established that three characteristic periods of the drying process can be traced in the graphical dependencies: I – heating; II – constant drying rate; III – falling drying rate. The calculation of heat fluxes for downward cross-ventilation of the grain layer, where air washes over IR heaters and reflectors and heats up to 35 °C, is presented. It was found that in the implementation of the process with a downward airflow, it is necessary to supply 20–25 % less radiant energy to the material at the same drying exposures according to the graphical dependencies. Conclusions. A mathematical description of the unsteady drying process of thermolabile material in a dryer, considering the change in the power of IR energy input during drying, has been formulated. An algorithm for calculating parameters that can be used for process identification and optimization of the operating parameters of existing grain dryers has been developed. Keywords: drying, grain material, mathematical model, diffusive transfer, moisture content, temperature, speed.

Research on Electricity Operation Behaviour Recognition Strategy Combined with Intelligent Image Recognition and Its Key Technology

Abstract This paper builds a power operation target detection model based on the YOLOv4 algorithm in intelligent image recognition, and optimizes the YOLOv4 algorithm by combining with the loss function to improve the accuracy of power target operation detection. The kmeans++ algorithm was used to cluster the electric power operation behaviors to obtain a more accurate electric power operation behavior dataset. Three sets of tests were conducted after the model was constructed, targeting the behavioral set of electric power workers in a certain place and the behavior in VOC format, followed by the multi-target tracking effect test. The analysis based on the obtained data showed that the helmet placement detection confidence, fatigue detection confidence, smoking detection confidence, and fall detection confidence reached 0.97, 0.93, 0.89, and 0.93, respectively. The transmission speed got 53.58 fps, and the recall and precision of the multi-target tracking were also above 93%. The YOLOv4 detection model based on keans++ clustering algorithm can effectively detect and identify the variable power operation behavior images.

A Constructive and Empirical Study of Individualized Teaching Quality Evaluation for College English Teachers

Abstract With the rapid development of society and the rapid change of software technology, the original teaching content and teaching mode of college English can no longer meet the learning needs of college students, so how to improve the quality of personalized teaching in the classroom of college English teachers is of great significance to improve the teaching level and other aspects. The article uses the idea of variable power to obtain personalized features, and through the Apriori algorithm, through data mining, so that students can choose courses suitable for themselves while using hierarchical analysis to evaluate and analyze the personalized teaching of English classroom in a university, in addition, using structural equation model to seek for factors affecting the personalized teaching of college English, and then improve the quality of English teaching. After normalization, we get E 2 = [0.305 0.463 0.166 0.069], which means that the students’ comprehensive judgment of the personalized teaching quality assessment system of English teachers in the university is good. Finally, through the construction of structural equation modeling, the correlation coefficients between “teaching responsibility,” “teaching level,” and “teaching method” are all above 0.9. Their C.R. values are all greater than 1.96, indicating that the students have good judgment on the personalized teaching quality assessment system of the English teachers in the school. Because the C.R. values are all above 1,96, the correlation between the three factors and teaching quality is more significant.

Dynamic economic load dispatch problems in microgrid containing renewable energy sources based ontunicate swarm algorithm

Dynamic Economic Load Dispatch (DELD) is a significant problem in microgridincluding renewable energy sources (RESs). The aim of this paper is to minimize the overall cost of the system while ensuring that the power demands of the consumers are met. However, with the added complexity of RESs, conventional optimization techniques may not be able to provide optimal solutions. This is where metaheuristic algorithms come into play, which are optimization techniques inspired by natural phenomena such as biological, nature, and animal behavior. This studycovers a new bio-inspired algorithm called Tunicate Swarm Algorithm (TSA)applied for solving DELD in microgrid with considering the variable power output of RES such as wind and solar energy. The DELD problem should also incorporate various constraints such as power balance and generation limits. Four cases of DELD containing RESs are treated. The obtained resultsare compared to other methods.. The result shows that for the DELD problem, the TSA demonstrate the superiority in term of optimise thegeneration cost compared to other optimization techniques.

Analysis and Validation of a Novel Symmetrical Structure for Toroidal Variable Power Inductors in Energy Storage Systems

Analysis and Validation of a Novel Symmetrical Structure for Toroidal Variable Power Inductors in Energy Storage Systems

Review on the Electric Spring Connected to the Renewable Energy System to Minimize Harmonics and Voltage Profile Enhancement

The emerging smart grid technology known as Electric Spring (ES) has been employed previously to maintain voltage and power stability in renewable energy-based grids that are minimally regulated or self-contained. This study thoroughly investigated the foundational theories, modeling approaches, practical uses, and restrictions associated with Electric Springs by analyzing existing Scholarly works in this domain Electric Springs implement a direct power control approach. solution for the next-generation single-phase Systems, addressing the limitations of current ES control methods. This solution aims to improve power management in microgrids, where integrating renewable energy sources (RESs) poses challenges due to the unpredictable power output. The challenge involves managing two aspects: the variable Power consumed by ES and the power fed into the grid. The suggested straightforward and accurate signal manipulation method, namely, ANN-based Electric Spring (ES), is set to be deployed. This technique can adeptly manage these aspects in both stable conditions and during transitions in Renewable Energy Sources (RES).

Minimum waiting time scheduling of power supply assignation to variable rate requests

The paper deals with a novel scheduling strategy for the assignation of a power resource. More precisely, a set of tasks, characterized by power requests with variable power rate, such as in the domestic electric appliances, is considered and the strategy aims at minimizing the average waiting time. The main result is that to determine the assignation strategy only the information on the maximum needed power and on the duration of the tasks is required. During the implementation of the strategy, the scheduler needs to periodically obtain, from the appliances, information on the maximum power needed to complete the task. In the case of two tasks, the strategy is shown, both analytically and with simulations, to perform better than a non-interruptible strategy.

Experimental and numerical simulation study of sodium heat pipe with large aspect ratio

As a core cooling device of reactor, a high temperature sodium heat pipe is designed in this paper which has a large aspect ratio of 126. The effects of heating mode and evaporation section length on its start-up are studied experimentally. The results show that the axial temperature uniformity of the heat pipe is better under variable power heating mode. As the evaporation cross-section length increases, thermal resistance decreases by 50%. Compared with heat pipes with low aspect ratio, heat pipes with large aspect ratio are more difficult to start up. Furthermore, numerical simulation is conducted on the designed sodium heat pipe to acquire the velocity and pressure distribution during steady-state operation.

Biomagnetic Fluid Flow on a Nonlinearly Stretching Sheet with Variable Thickness in a Magnetic Environment

The main contribution of the current work is a numerical and mathematical investigation of the effects of magnetic dipole and electrical conductivity on the heat and flow transfer of biomagnetic fluid over a non-linear stretched sheet with variable thickness. Static magnetic fields are produced by magnetic dipoles, which are used in medical a pplications such as MRI, drug administration, and cancer therapy. Additionally, the impact of non-linear heat source/sink features was examined in the study, leading to an interesting phenomenon. The PDEs are attenuated to nonlinear ODEs with dealing appropriate similarity variables. These resultant ODEs are computed by developing an effective method emerged on the application of the finite differences technique. In the end, this section offers a summary of the implications resulting from different physical limitations on blood flow, including variable thickness and power index effects. It was discovered that the rise in Kelvin and Lorentz forces in the boundary layer significantly affected blood flow. The current findings for the biomagnetic fluid model are novel and inventive since they effectively expand upon the issues previously addressed by previously published scientific documentation.

АВТОМАТИЗИРОВАННАЯ СИСТЕМА СУШКИ И ОЧИСТКИ РАСТИТЕЛЬНОГО СЫРЬЯ С ПРИМЕНЕНИЕМ ТЕПЛОВЫХ АККУМУЛЯТОРОВ И ЭЛЕКТРОНАГРЕВАТЕЛЕЙ С ЭФФЕКТОМ САМОРЕГУЛИРОВАНИЯ ТЕМПЕРАТУРЫ

The paper presents an automated system for processing fruit and vegetable products, which includes such technological operations as steam peeling (thermovacuum method), cutting, convective and vacuum drying of fruit and vegetable products. For efficient operation of the plant a control system is used, which provides full automation of the whole complex of technological elements. The plant has a high level of energy efficiency, as it uses thermal accumulators (with the effect of thermomagnetic convection) and heaters with temperature self-regulation. The parameters of the operation modes of thermal accumulators agree with the operation of the heater with adaptive energy consumption (with variable power and constant temperature) depending on the temperature of heating of plant raw materials. At the first stage, when intensive heat flow is required for drying - thermal accumulators provide inertia-free heating of horticultural products. The function of the heater is connected with controlled heating depending on the temperature of plant raw material, providing heat flow correlated with the operation of thermal accumulators. The use of combined and adaptive heating from thermal accumulators and electric heaters allows for uniform temperature distribution (temperature field), which ensures efficient processing of vegetable raw materials. Automated change of heating power from electric heaters and thermal accumulators provides the possibility of adaptation to any power electric network based on the need for the level of processed horticultural products, and the use of thermal accumulators allows to accumulate thermal energy from solar collectors.

Temperature field optimization for distributed combined heat of multi-microwave sources based on group consistency under time-varying communication topology

Microwave heating is one of the commonly used methods for heat treatment of various materials. This paper proposes a consistent variable power heating strategy under multi microwave source cluster switching topology mode. Firstly, a distributed structure of microwave source cluster collaborative output with bidirectional ring communication topology was constructed using virtual structure method. On this basis, nonlinear distributed control with consistent output of microwave source clusters in different modes was achieved. Meanwhile, a microwave source clustering scheme is proposed, and the objective function of automatic power allocation for each subgroup and its constraint function are constructed to realize the formation of different clustering modes in different time periods, and the consistent output of self-allocation of power for each subgroup. Secondly, the feasibility and effectiveness of the proposed strategy are verified by the experiments of heating SiC materials in a high-power microwave reactor and analyzing the temperature uniformity and energy conversion efficiency during the heating process. Finally, the simulation results show that the temperature uniformity is improved by 35.7%–63.6% and the energy conversion efficiency is improved by 27.9%–41.1%, which can effectively optimize the temperature field distribution.