Application of a boundary integral method to the optimization ofsolid rotor machines

This paper is devoted to the optimization of electric machine solid rotors for high speed applications, using a boundary integral method. The method is applied to two examples: a slotted asynchronous rotor; and a salient reluctant synchronous rotor. Starting under constant voltage is especially studied in both cases. An important part of the paper deals with the asynchronous motor. An idealized stator generates a sinusoidally distributed tangential flux density, so that the optimization concerns only the rotor slotting. At constant permeability, the boundary integral method proves to be very fast and efficient for the approximate design of a slotted rotor     

Simulation of the impulse response of electrical machines

This paper presents three different methods for modeling the transient response of electrical machines. The state-space approach, the Laplace transformation technique and the realization of a new, wide-frequency range equivalent circuit of the machine terminal impedance are applied to obtain the transient response to any waveform. The introduced methods are based on the frequency response of the machine which is often seen as a black box. Both laboratory- and large-scale machines are used to investigate the effect of a variety of impulse waveforms on the transient response of the other phases and to obtain the voltage distribution along the winding of each phase. A frequency response test for the machine is applied to obtain the resonance frequencies and the rational forms for both the voltage gains and terminal impedance. Excellent agreement (error is within 3%) is found between the three methods and the experimental results for different types and ratings of electrical machines under different impulse waveforms     

Support vector machines for short‐term electrical load forecasting

Short‐term electrical load forecasting plays a vital role in the electric power industries. It ensures the availability of supply of electricity, as well as providing the means of avoiding over‐ and under‐utilization of generating capacity and therefore optimizes energy prices. Several methods have been applied to short‐term load forecasting, including statistical, regression and neural networks methods. This paper introduces support vector machines, the latest neural network algorithm, to short‐term electrical load forecasting and compares its performance with the auto‐regression model. The results indicate that support vector machines compare favourably against the auto‐regressive model using the same data for building and testing both models based on the root‐mean‐square errors between the actual and the predicted data. Support vector machines allow the training data set to be increased beyond what is possible using the auto‐regressive model or other neural networks methods. Increasing the training data further improves the performance of support vector machines method. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance of an improved design for storage-type domestic electrical water-heaters

Performance of an improved design for storage-type domestic electrical water-heaters (EWHs) was experimentally investigated for energy conservation. The results were compared with those of conventional design EWHs having the same tank size and power rating. Data were obtained for two tanks with aspect ratios of 1 and 2, two draw-off rates of 5 and 10 l/min, and using three heating elements of different heights. It is found that improved design EWHs provide more hot water at almost constant temperature in the first mean residence time, which is of prime concern for the user. Thus, they exhibit higher discharging efficiencies due to better thermal stratification inside the heater storage tank. Also, thermal performance is enhanced with increasing tank aspect ratio and decreasing draw rate. These characteristics have a direct impact on energy consumption and result in lower electricity bills. The design improvements are simple to adapt as they only require minor modifications to be made to existing EWH models.     

End effect in linear induction and rotating electrical machines

The finite length of the iron core (stator) has a significant impact on the performance of linear induction machines (LIMs). The performance of a cylindrical symmetric linear induction machine (CSLIM) has been studied considering the impact of the finite stator length. The analytical procedure, originally developed for calculation of plane linear induction machines, has been modified to facilitate the analysis of CSLIM. The procedure is based on Fourier series expansions of the electromagnetic quantities and the air-gap length. This study further provides information on the effect of finite length of tooth in the direction of rotation in rotating electrical machines. As examples, the overheating of the stator core in a 500 MVA synchronous hydrogenerator and the detrimental impact of the end effect on a 506.5 MVA synchronous turbogenerator in a nuclear power station is described.     

基于改进混沌粒子群算法的光伏阵列建模方法研究

准确地建立光伏阵列模型对光伏电站性能分析具有十分重要的意义.由于传统光伏阵列建模方法具有模型参数计算困难、计算结果精度低、对铭牌参数依赖性高等不足,导致传统光伏阵列模型具有适应性差等.文章从实测数据出发,提出了一种基于改进混沌粒子群算法的光伏阵列建模方法.模拟结果表明,相比于传统的建模方法,基于改进混沌粒子群算法的光伏...     

A standstill frequency response method for large salient pole synchronous machines

In this article, a Standstill Frequency Response Test (SSFR) is proposed, with the aim of determining the direct and quadrature axis operational impedances for salient pole synchronous machines. The method is applied with the rotor at standstill in a given arbitrary position, thus avoiding the difficulties in rotor mechanical alignment and rendering it suitable for large salient pole synchronous machines of hydroelectric power plants.     

A new method for determining the armature leakage reactance ofsynchronous machines

A method for determining the armature leakage reactance of synchronous machines is presented. In this method, the terminal voltage/armature current characteristic with the machine unloaded and unexcited is needed, together with the open-circuit characteristic of the machine. The armature leakage reactance is derived from these two curves using an iterative technique. The armature leakage reactances of five synchronous machines of different designs are obtained using this method. Their values are compared with those of the Potier reactance of these machines measured at various terminal voltages     

A field reconstruction method for optimal excitation of permanent magnet synchronous machines

Vibration caused by torque ripple and radial force harmonics is a concern in many applications of permanent magnet synchronous machines (PMSMs). Alternative methods of machine design and/or stator excitation to minimize torque ripple have received considerable attention in recent years. Comparatively, methods to minimize radial force harmonics have received less attention. In this paper, a field reconstruction (FR) method is derived that provides a designer with the capability to rapidly determine the radial and tangential components of force under arbitrary stator excitation. Using the field reconstruction method, stator current waveforms that minimize the ripple of both torque and radial force are derived subject to the constraint of maintaining a satisfactory level of torque density.     

A method for magnetizing curve identification in rotor fluxoriented induction machines

Operation of an indirect rotor flux oriented induction machine in the field weakening region is usually realized by varying the rotor flux reference in inverse proportion to the speed of rotation. In order to provide the correct stator d-axis current reference at all speeds, it is necessary to incorporate the inverse magnetizing curve of the machine in the controller. The paper proposes an experimental method for identifying the inverse magnetizing curve, specifically developed for the type of vector controlled drives described. The method utilizes the same indirect vector controller and PWM inverter that are used in subsequent normal operation of the drive. It requires that the machine can run under no-load conditions and that the fundamental component of the stator voltage can be measured. The simplicity and accuracy of the method make it well suited for use during commissioning of the drive. The method is verified by extensive experimentation     

Application of AI tools in fault diagnosis of electrical machines and drives-an overview

Condition monitoring leading to fault diagnosis and prediction of electrical machines and drives has recently become of importance. The topic has attracted researchers to work in during the past few years because of its great influence on the operational continuation of many industrial processes. Correct diagnosis and early detection of incipient faults result in fast unscheduled maintenance and short down time for the machine under consideration. It also avoids harmful, sometimes devastative, consequences and helps reduce financial loss. Reduction of the human experts involvement in the diagnosis process has gradually taken place upon the recent developments in the modern artificial intelligence (AI) tools. Artificial neural networks (ANNs), fuzzy and adaptive fuzzy systems, and expert systems are good candidates for the automation of the diagnostic procedures. This present work surveys the principles and criteria of the diagnosis process. It introduces the current research achievements to apply AI techniques in the diagnostic systems of electrical machines and drives.     

电机冷却用翅管换热器传热和阻力特性研究

研究了一种电机冷却用新型翅片开孔结构换热器的性能,对三种结构的翅片管换热器进行了换热和阻力性能测试,新型翅片换热器结构为翅片间距2.1 mm且翅片上具有开孔结构,对照组换热器分别为翅片间距2.1 mm无开孔换热器和翅片间距2.3 mm无开孔换热器。试验结果表明,相同Re数下,该种具有开孔结构换热器在所有换热器中换热性能最好,较2.1 mm无孔提升38%～39%,但同时压降损失也最大,较2.1 mm无孔提升41.9%～42.9%。采用j/f评价综合性能,结果显示,Re>6700时,新型翅片换热器性能优于同翅片间距无开孔换热器。文章还对这三种结构翅片管换热器进行了传热和阻力关联式拟合,可为相关理论研究和工程选用提供参考。     

An improved dynamic test method for solar collectors

A comprehensive improvement of the mathematical model for the so called transfer function method is presented in this study. This improved transfer function method can estimate the traditional solar collector parameters such as zero loss coefficient and heat loss coefficient. Two new collector parameters t and m_fC_f are obtained. t is a time scale parameter which can indicate the heat transfer ability of the solar collector. m_fC_f can be used to calculate the fluid volume content in the solar collector or to validate the regression process by comparing it to the physical fluid volume content if known. Experiments were carried out under dynamic test conditions and then test data were processed using multi-linear regression method to get collector parameters with statistic analysis. A comparison of the collector parameters obtained from the improved transfer function (ITF) method and the quasi-dynamic test (QDT) method is carried out. The results show that the improved transfer function method can accurately obtain reasonable collector parameters. The influence of different averaging time intervals is investigated. Based on the investigation it is recommended to use on line calculation if applicable for the second-order differential term with 6–9 min as the best averaging time interval. The measured and predicted collector power output of the solar collector are compared during a test of 13 days continuously both for the ITF method and the QDT method. The maximum and averaging error is 53.87 W/m² and 5.22 W/m² respectively of the ITF method while 64.13 W/m² and 6.22 W/m² of the QDT method. Scatter and relative error distribution of the measured power output versus the predicted power output is also plotted for the two methods. No matter in either error analysis or scatter distribution, the ITF method is more accurate than the QDT method in predicting the power output of a solar collector.In conclusion, all the results show that the improved transfer function method can accurately and robustly estimate solar collector parameters and predict solar collector thermal performance under dynamic test conditions.     

A comprehensive method for the calculation of inductance coefficients of cage induction machines

In this paper, a new comprehensive method for the calculation of inductance coefficients of squirrel cage induction machine based on combined winding function approach (WFA) and magnetic equivalent circuit (MEC) is presented. By taking into account machine geometry, rotor skewing, stator and rotor slots effects and type of windings connection, this method is able to model most of the important features of an induction machine. The effects of each machine parameter on the inductance coefficients are verified. Also, effects of several rotor asymmetries on these inductances are shown. Simulation results are verified by more elaborate nonlinear finite element model and finally with experimental results.     

A method for data-driven evaluation of operator impact on energy efficiency of digging machines

Material handling (including digging) is one of the most energy-intensive processes in mining. Operators’ skills and practices are known to be some of the major factors that affect energy efficiency of digging operations. Improving operators’ skills through training is an inexpensive and effective method to improve energy efficiency. The method proposed in this work uses data collected by monitoring systems on digging equipment to detect the monitored parameters that lead to differences in energy efficiency of operators (responsible parameters). After data extraction, removing the outliers, and identifying the operators with sufficient working hours, correlation analysis can be used to find parameters that are correlated with energy efficiency. Regression analysis on pairs of operators is then used to detect responsible parameters. Random sampling is used to overcome missing data issues in the analysis. This statistics-based method is simple and adequately accounts for the high variability in data collected from these monitoring systems. The proposed method was illustrated using data collected on five operators working on a 64-m³ (85 yd³) Bucyrus-Erie 1570w dragline. The case study results show that dump height and engagement/disengagement position of the bucket are the most likely parameters to cause differences between energy efficiency of these operators. On the other hand, cycle time, payload, and swing in time are least likely to influence differences in operator energy efficiency.     

Study on adjoint-based optimization method for multi-stage turbomachinery

Adjoint-based optimization method is a hotspot in turbomachinery.First,this paper presents principles of adjoint method from Lagrange multiplier viewpoint.Second,combining a continuous route with thin layer RANS equations,we formulate adjoint equations and anti-physical boundary conditions.Due to the multi-stage environment in turbomachinery,an adjoint interrow mixing method is introduced.Numerical techniques of solving flow equations and adjoint equations are almost the same,and once they are converged respectively,the gradients of an objective function to design variables can be calculated using complex method efficiently.Third,integrating a shape perturbation parameterization and a simple steepest descent method,a frame of adjoint-based aerodynamic shape optimization for multi-stage turbomachinery is constructed.At last,an inverse design of an annular cascade is employed to validate the above approach,and adjoint field of an Aachen 1.5 stage turbine demonstrates the conservation and areflexia of the adjoint interrow mixing method.Then a direct redesign of a 1+1 counter-rotating turbine aiming to increase efficiency and apply constraints to mass flow rate and pressure ratio is taken.     

An improved design method for solar water heating systems

In this paper, the $\text{Φ}$,f-chart method is extended to open-loop solar hot water heating systems. This method is an improvement over the f-chart method since it does not impose any restrictions on the water set temperature, water mains temperature, or the preheat tank loss coefficient. The procedure is general for both one-tank and two-tank systems. The modified $\text{Φ}$,f-chart method is still applicable to the closed-loop systems for which it was originally developed.     

基于改进灰狼优化算法的孤岛微网系统容量优化分析

孤岛微网的日前调度安排对岛屿配电网的安全稳定运行意义重大。为了对孤岛微网的日前调度进行安排,更好地优化微网结构,文章针对含有光伏和抽水蓄能电站的孤岛微网进行建模分析,将光伏阵列数量、额定功率和抽水蓄能电站上水库的容积作为决策变量,等年值平均投资成本和负荷失电率为目标函数,使用Matlab对某岛屿的天气和负荷数据进行分析。为了使光电-抽水蓄能协同运行的效益最大化,采用灰狼优化算法求解微网模型。优化结果表明,灰狼优化算法在孤岛微网模型的容量优化问题中可以节约投资成本,实现环境友好型供电。