Search

Cryogenic cooling is a well-established and expanding technology. In the field of electric machines, it allows the construction of more efficient machines with a high power density. This paper addresses the main cooling technologies and their impact on cryogenic machine construction, providing perspective for their use in future electrical machines. Although cost and safety issues of cryogenic systems are still holding back the uptake of cryogenic electric motors and generators, research in this field should provide significant improvements and promote their use at different levels. [ABSTRACT FROM AUTHOR]

Purpose: More electric aircraft (MEA) is defined as the extensive usage of electric power in aircraft. The demand for electric power in new generation aircraft rises due to environmental and economic considerations. Hence, efficient and reliable starter/generators (SGs) are trending nowadays. The conventional main engine starting system and power generation system can be replaced with an individual SG. The constraints of the SG should be investigated to handle the aviation requirements. Even though the SG is basically an electric machine, it requires a multidisciplinary study consisting of electromagnetic, thermal and mechanical works to cope with aviation demands. This study aims to review conventional and new-generation aircraft SGs from the perspective of electric drive applications. Design/methodology/approach: First of all, the importance of the MEA concept has been briefly explained. Also, the historical development and the need for higher electrical power in aircraft have been indicated quantitatively. Considering aviation requirements, the candidate electrical machines for aircraft SG have been determined by the method of scoring. Those machines are compared over 14 criteria, and the most predominant of them are specified as efficiency, power density, rotor thermal tolerance, high-speed capability and machine complexity. The features of the most suitable electrical machine are pointed out with data gathered from empirical studies. Finally, the trending technologies related to efficient SG design have been explained with numeric datasets. Findings: The induction motor, switched reluctance motor and permanent magnet synchronous motor (PMSM) are selected as the candidate machines for SGs. It has been seen that the PMSM is the most preferable machine type due to its efficient operation in a wide range of constant power and speed. It is computationally proven that the using amorphous magnetic alloys in SG cores increases the machine efficiency more. Also, the benefits of high voltage direct current (HVDC) use in aircraft have been explained by a comparison of different aircraft power generation standards. It is concluded that the HVDC use in aircraft decreases total cable weight and increases aircraft operation efficiency. The thermal and mechanical tolerance of the SG is also vital. It has been stated that the liquid cooling techniques are suitable for SGs. Originality/value: The demand for electrical power in new generation aircraft is increasing. The SG can be used effectively and efficiently instead of conventional systems. To define requirements, constraints and suggestions, this study investigates the SGs from the perspective of electric drive applications. [ABSTRACT FROM AUTHOR]

The problem of reducing magnetic losses (no-load losses) in the steel of magnetic circuits of electrical machines is studied. The determination of the optimum thickness of steel sheets of magnetic circuits in electrical machinery is investigated. The optimization criterion is minimum power losses in the steel. The magnetic power losses in contemporary electrical machinery and apparatus are analyzed as a function of the thickness of the sheets of electrical steel. A method is proposed for determining the optimum thickness of steel sheets in the magnetic circuit of an electrical machine based on a wattmeter technique. During an experiment on two identical magnetic circuits made of different thicknesses of sheet steel, the losses in the steel were measured at two magnetic reversal frequencies and the optimum thickness of the sheets was calculated. It was shown that the proposed formula for calculating the sheet thickness holds for both isotropic and anisotropic steel. The proposed method is applicable to transformers, as well as to electric motors and generators. [ABSTRACT FROM AUTHOR]

The reduction of emission is a key goals for the aviation industry. One enabling technology to achieve this goal, could be the transition from conventional gas turbines to hybrid-electric drive trains. However, the requirements concerning weight and efficiency that come from applications like short range aircraft are significantly higher than what state-of-the-art technology can offer. A key technology that potentially allows to achieve the necessary power and volume densities for rotating electric machines is superconductivity. In this paper we present the concept of a high power density generator that matches the speed of typical airborne turbines in its power class. The design is based on studies that cover topology selection and further electromagnetic, HTS, thermal, structural and cryogenics aspects. All domains were analyzed by means of analytical sizing and 2D/3D FEA modeling. With the help of our digital twin that is a synthesis of these models, we can demonstrate for the first time that under realistic assumptions on material properties gravimetric power densities beyond 20 kW kg−1 can be achieved. [ABSTRACT FROM AUTHOR]

This study addresses double-sided stationary stators in a linear electric generator with similar operation to a linear oscillatory motion electric machine. The plate mover in the linear electric generator's double-sided stationary stators is powered by the acoustic power output of the thermoacoustic engine's acoustic line. The main originality of this structure resides in the linear guidance used for the moving part. The mover is made up of a plate of sandwich magnets between two stators. This plate is in magnetic balance between the two stators through a controlled friction device. [ABSTRACT FROM AUTHOR]

Resonances in nonlinear spherical dynamos are considered in the framework of a simple dynamo model which is formulated in terms of an appropriate dynamical system. For a suitable parametric range, the model demonstrates a magnetic field excitation in the form of vacillations, dynamo bursts and even stationary magnetic configurations. A resonance can be expected if the magnetic field penetrates another shell from one dynamo active shell, or for a periodic modulation of dynamo drivers. In both cases, we isolate some resonant phenomena mainly in the form of resonant absorption. The results obtained are, however, quite far from naive expectations and the problem seems to deserve a more extended investigation. [ABSTRACT FROM AUTHOR]

The paper presents electric Machine-Converter Voltage Source (MCVS) for systems of distributed power supply with shaping output voltage in an electric machine (generator). The MCVS consists of electric machine and a cycloconverter that has three-phase bridge circuit. Both synchronous generator and asynchronous exciter, which are located in one housing, operate as electric modulation generator. Functional diagram of complex MCVS, where the output voltage is stabilized by simultaneous or separate use of several control channels. We analyzed output voltages of MCVS and dependences of non-sinusoidality and distortion factors on ratio rotational speed of generator to output voltage frequency of MCVS for various amplitude modulation indexes and control modes of cycloconverter. [ABSTRACT FROM AUTHOR]

This paper presents the characteristics analysis of the flux-switching synchronous generator (FSG) applying noinsulation (NI)-type high-temperature superconducting (HTS) field coils. The HTS FSG can be cost effective, since the field coils and armature windings are both installed in the stator, while the rotor is onlymade of iron corewith tooth. Alongwith lowcost, since HTS field coils in the FSGs are located in the stationary part of the generator, FSG can be a solution for the design complexities of the excitation and cooling systems for HTS field coils. In addition, several studies on HTS coils without turn-to-turn insulation (NI) have been reported for HTS field coils for applying in electrical rotating machines. The NI-type winding technique enhances the stability of the HTS field coil since the overcurrent is automatically bypassed through the contacts between winding turns. Nevertheless, there is still an issue about whether the NI-type HTS field coil can be applied to the electrical rotating machines. In this study, we fabricated and tested an NI-type HTS field coil. In addition, a 600-kW HTS FSG was designed using a fundamental design process and the characteristics analysis of the generator was performed based on the test results of the fabricated NI-type field coil. The results show that the HTS FSG having NI-type HTS field coils is able to operate normally under normal operating conditions. However, the field current charging problem issue has been revealed through this study. Therefore, further research will need to improve the problem. [ABSTRACT FROM AUTHOR]

The article presents a new topology of the high-speed synchronous electrical machines with permanent magnets with the tooth-coil windings with a stator magnetic core made of amorphous alloys for prospective unmanned aerial vehicles. This is a multidisciplinary design algorithm with optimization elements, which are proposed to design such machines. Based on the proposed algorithm, calculations of several topologies were performed by using computer simulation methods. In addition, the analysis of the rotor dynamics as part of the turbojet engine of the unmanned aerial vehicle and the calculations of the mechanical rotor strength were performed. To minimize the eddy-current losses in permanent magnets, the multicriteria optimization of the slotted zone was carried out by using genetic algorithms. A cooling system was proposed, and thermal calculations were performed. To verify the proposed design algorithm and to evaluate the efficiency of the amorphous alloy, a full-sized 5 kW experimental sample with a rotational speed of 60,000 rpm was created. Results can be used to create new promising UAVs and to design electrical machines for other industrial applications. [ABSTRACT FROM AUTHOR]

Although triboelectric nanogenerator (TENG) has been explored as one of the possible candidates for the auxiliary power source of portable and wearable devices, the output energy of a TENG is still insufficient to charge the devices with daily motion. Moreover, the fundamental aspects of the maximum possible energy of a TENG related with human motion are not understood systematically. Here, we confirmed the possibility of charging commercialized portable and wearable devices such as smart phones and smart watches by utilizing the mechanical energy generated by human motion. We confirmed by theoretical extraction that the maximum possible energy is related with specific form factors of a TENG. Furthermore, we experimentally demonstrated the effect of human motion in an aspect of the kinetic energy and impulse using varying velocity and elasticity, and clarified how to improve the maximum possible energy of a TENG. This study gives insight into design of a TENG to obtain a large amount of energy in a limited space. [ABSTRACT FROM AUTHOR]

This paper presents work completed in order to investigate the importance of magnetic shunts in transverse flux machines. Two types of transverse flux machines with different configurations were designed and tested in the laboratory. The first type of machine is a transverse flux generator with inner rotor. This machine was designed according to one of the patents. The second type of the machine is a transfer flux generator with double coil. Both types of the generators were designed in such a way so that it was possible to implement magnetic shunts inside the machines. Finite-element method analysis and experimental results showed that transverse flux machines without magnetic shunts had a number of disadvantages compared to those with magnetic shunts. These disadvantages are: higher flux leakage in the stator cores, partial cancelation of flux linkage in the coils, higher cogging torque, and increased torque ripple. This paper showed that magnetic shunts played a significant role in the performance of transverse flux machines. As study showed, magnetic shunts complicate a manufacturing process and increase the weight of the machine. However, power to weight ratio of the machines with magnetic shunts is higher than that of the machines without magnetic shunts. [ABSTRACT FROM AUTHOR]

In this paper, a simplified analysis technique is introduced to allow the dq modeling of a nonoverlap, short-circuited coil winding slip permanent magnet (PM) coupler (S-PMC). The proposed technique for predicting the coil currents using a number of static finite-element (FE) solutions takes the effect of, amongst others, mutual coupling between the coils and layers into account. The technique also allows a difference in the currents of top- and bottom-layer coils, if such coil windings are used. This all makes the method particularly attractive for use in the design optimization of the S-PMC. Excellent correlation with measured and transient FE analysis results was found for a 2.2 kW S-PMC prototype with an efficiency of 97% at a rated load. [ABSTRACT FROM AUTHOR]

In high-speed aircraft, an altitude adjustment system is an important auxiliary part that needs rapid power support. In this paper, an ultrahigh-speed generator is described. However, the ultrahigh-speed generator's safe operation and smooth power supply to the load can be threatened by mismatch between the open-loop generator and fickle load conditions. In this study, a power converter with a paralleled energy-matching link was developed, which can broaden the safe operation zone and ensure the generator's safe operation as well as the load's smooth power supply under relatively light-load conditions. This power converter can also ensure the power supply voltage under relatively heavy-load conditions. The validity of the proposed power converter was verified by experiments. [ABSTRACT FROM AUTHOR]

Two general methods to start the engine are investigated by the linear electric machine operating as a linear motor and identified one for a specific FPEG prototype configuration. Based on that, a novel method to start the engine by mechanical resonance is proposed. Both simulation and test results are presented, and the numerical model is successfully validated. The results show that with a fixed motor force of 110 N, within 0.5 s, the maximum in-cylinder pressure could reach 13 bar, indicating that the engine is ready for ignition. Further investigation on the engine performance with the closed-loop control strategy is carried out. The results demonstrate that it is feasible to start the FPEG with mechanical resonance with a closed-loop controlled electric linear machine that applies a proper constant motor force in the direction of the natural bouncing motion. With different starting motor force, the top dead centre (TDC) value for both cylinder is different during the first few running cycles, but the difference reduces and tends to be zero during the stable resonance state. There is not any significant difference observed on the engine frequency and piston profile during combustion process. [ABSTRACT FROM AUTHOR]

The paper covers the theoretical background and tests of two asynchronous squirrel cage generators connected to voltage source inverters working in parallel. Inverters were connected in parallel by their intermediate direct current circuits by means of auctioneering diodes, and then to a DC power network. The real-time control algorithm of digital signal processor DSP and field-programmable gate array FPGA was used to achieve proper excitation of two different power machines, and to maintain high enough levels of direct current link voltage. Windings of both generators are fed by use of so-called machine side inverters. The asynchronous generator is a voltage source inverter controlled by a field-oriented control algorithm based on the current machine model. To prove robustness of the chosen algorithm, different types of load were applied while generators and inverters worked in parallel. [ABSTRACT FROM AUTHOR]

A traction electric drive is used for an industrial tractor. The motor consists of a generator, a controlled rectifier, autonomous inverters, and two onboard motors. The key feature of the introduced electric drive is the use of field regulated independent excitation reluctance machine as a generator and traction motors. These electric machines have the following performance specifications: the generator and motor design is brushless; and simple, the rotor has high mechanical stiffness that increases reliability at high rate and overloads. There are no turns on the rotor; the motor is designed for simplicity of manufacture. The drives have increased effectiveness in terms of the effect of a “cold” rotor frame; the motors have high torque overloads power (up to 4-6 times the values of nominal torque). The turns of the motor and the generator are one- layered with full pitch capability of current and voltage. The drive manipulation is based on the transistors. The interval of the torque regulation is 1:10 resulting in permanent power for the drive [1] . This motor is used not only as a traction drive, but because of the simplicity of a frame it may be used for other devices where high load working cycles are required for operation. [ABSTRACT FROM AUTHOR]

This paper presents the modeling of intelligent energy control center (ECC) controlling distributed generators (DGs) using multi-agent system. Multi-agent system has been proposed to provide intelligent energy control and management in grids because of their benefits of extensibility, autonomy, reduced maintenance, etc. The multi-agent system constituting the smart grid and agents such as user agent, control agent, database agent, distributed energy resources (DER) agent work in collaboration to perform assigned tasks. The wind power generator connected with local load, the solar power connected with local load and the ECC controlled by fuzzy logic controller (FLC) are simulated in MATLAB/SIMULINK. The DER model is created in client and ECC is created in server. Communication between the server and the client is established using transmission control protocol/internet protocol (TCP/IP). The results indicate that the controlling of DER agent can be achieved both from server and client. [ABSTRACT FROM AUTHOR]

In order to increase the utilization of renewable energy sources and to reduce the need of generator-provided ancillary services and inefficient peaking generation, buildings are progressively transforming into smarter electricity consumers and active participants in power system operations. In this work, an R-C thermodynamic model of building that strongly relates to the power consumption of heating ventilation air-conditioning system (HVAC) is firstly introduced. To offer the aggregated flexible HVAC power to the grid as regulating power, we propose a building-aggregator-grid contract framework and formulate a robust model predictive control (MPC) algorithm which both maximizes the profit of aggregator and minimizes the payment of each participating building to optimally declare power flexibility. Lastly, simulation results on a group of real and hypothetical buildings validate the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

This paper demonstrates that machine learning can be used to create effective algorithm selectors that select between power system control algorithms depending on the state of a network, achieving better performance than always using the same algorithm for every state. Also presented is a novel method for creating algorithm selectors that consider two objectives. The method is used to develop algorithm selectors for power flow management algorithms on versions of the IEEE 14- and 57-bus networks, and a network derived from a real distribution network. The selectors choose from within a diverse set of power flow management algorithms, including those based on constraint satisfaction, optimal power flow, power flow sensitivity factors, and linear programming. The network state-based algorithm selectors offer performance benefits over always using the same power flow management algorithm for every state, in terms of minimizing the number of overloads while also minimizing the curtailment applied to generators. [ABSTRACT FROM AUTHOR]

In this paper authors are studying processes in electrical generators with rotors and stators with nonmagnetic shield with high coercitive permanent magnets. These generators can be used in hydroenergy and aerospace industry. In the paper there is developed a mathematic model allowing to analyze statical and dynamical characteristics of electrical generators with rotors and stators with nonmagnetic shield. To check the theoretical results there was made computer model in Ansys software. Authors got that results of mathematical models is comparable with the results of computer model. [ABSTRACT FROM AUTHOR]

To maximize efficiency and drivability of EV/HEV/FCV, an improved software and hardware architecture is developed. Four node cluster based microcontroller configuration is built for running V/f DTC and FOC algorithms on three different nodesin parallel to deliver real time torque and speed demand of vehicle in start-stop, acceleration and cruising mode respectively. This paper presents development of Direct Torque Control (DTC) algorithm to drive induction motor which will run on proposed parallel computing environment. DTC is implemented with conventional 3 level, 5 level symmetric and 7 level asymmetric inverterconfigurations. In order to minimize THD content in output voltage of inverter when operated with DTC mode, new PWM control strategy is developed. This has helped in obtaining DTC advantages with more Torque /Ampere and thus making this control efficient as close to FOC. Both symmetric and asymmetric multilevel inverter prototypes are developed and implemented with improved software and hardware architecture to run induction motor in transient conditions. Results are compared with DTC implemented with 3 level inverter and demonstration is done to show improvement in State of Charge (SoC) and other performance related parameters of battery. This exercise is carried out as a part ofimproving energy efficiency offull parallel HEV configuration for a passenger car application. [ABSTRACT FROM AUTHOR]

Further improvements in demand response programs implementation are needed in order to take full advantage of this resource, namely for the participation in energy and reserve market products, requiring adequate aggregation and remuneration of small size resources. The present paper focuses on SPIDER, a demand response simulation that has been improved in order to simulate demand response, including realistic power system simulation. For illustration of the simulator's capabilities, the present paper is proposes a methodology focusing on the aggregation of consumers and generators, providing adequate tolls for the demand response program's adoption by evolved players. The methodology proposed in the present paper focuses on a Virtual Power Player that manages and aggregates the available demand response and distributed generation resources in order to satisfy the required electrical energy demand and reserve. The aggregation of resources is addressed by the use of clustering algorithms, and operation costs for the VPP are minimized. The presented case study is based on a set of 32 consumers and 66 distributed generation units, running on 180 distinct operation scenarios. [ABSTRACT FROM AUTHOR]

Time-varying magnetic forces are the main source of vibrations in rotating electrical machines. A number of papers dealing with computational modelling of the dynamic behaviour of rotating electrical machines have been published. Almost all of these papers do not consider electro-mechanical interaction between the stator and the rotor of the machine. A computational model including electro-mechanical interaction is proposed in this paper. The influence of the air gap eccentricity due to eccentric mounting of the rotor pack on the shaft of the rotor is investigated. Electromagnetic coupled-field analysis was performed to obtain the dependence of the magnetic forces, which act on the stator and the rotor pack, on the time and air gap eccentricity. Attention has been paid to the air gap eccentricity due to the interaction between the stator and the rotor and the influence of the air gap eccentricity on the vibration and sound power of the machine. The obtained results show that the air gap eccentricity affects the amplitude spectrum of the magnetic forces. This change of amplitude spectrum causes a significant increase in the torsional vibration of the stator of the examined machine. The air gap eccentricity is also significantly reflected in the trajectory of the rotor centre line and radial load of bearings in the machine. [ABSTRACT FROM AUTHOR]

Compact solid-state system is the main development trend in pulsed power technologies. A compact solid-state high-voltage nanosecond pulse generator with output voltage of 300 kV amplitude, 10 ns duration (FWHM), and 3 ns rise-time was designed for a dielectric wall accelerator. The generator is stacked by 15 planar-plate Blumlein pulse forming lines (PFL). Each Blumlein PFL consists of two solid-state planar transmission lines, a GaAs photoconductive semiconductor switch, and a laser diode trigger. The key components of the generator and the experimental results are reported in this paper. [ABSTRACT FROM AUTHOR]

In a previous paper the authors optimally sized a combined heat and power distributed generator for an agro-industrial microgrid using expected demand profiles; in this paper, the effectiveness of such a generator is further investigated using measured demand profiles. A number of comparison are performed, including the calculation of the economic benefits, the evaluation of the impact of the generator by the grid point of view and the calculation of the imbalance reduction. [ABSTRACT FROM AUTHOR]

This paper focuses on the numerical modelling of a spark ignited free-piston engine generator and the model validation with test results. Detailed sub-models for both starting process and steady operation were derived. The compression and expansion processes were not regarded as ideal gas isentropic processes; both heat transfer and air leakage were taken into consideration. The simulation results show good agreement with the prototype test data for both the starting process and steady operation. During the starting process, the difference of the in-cylinder gas pressure can be controlled within 1 bar for every running cycle. For the steady operation process, the difference was less than 5% and the areas enclosed on the pressure–volume diagram were similar, indicating that the power produced by the engine and the engine efficiency could be predicted by this model. Based on this model, the starting process with different starting motor forces and the combustion process with various throttle openings were simulated. The engine performance during stable operation at 100% engine load was predicted, and the efficiency of the prototype was estimated to be 31.5% at power output of 4 kW. [ABSTRACT FROM AUTHOR]

It is necessary to accurately estimate parameters to have a better prediction on the response of a generator under different operating conditions. Since automatic generation control (AGC) is closely related to the real power and frequency of the unit, the dynamic parameters that are required by a standard AGC function are determined for the electric system of an oil facility. Speed droop characteristics, governor deadbands, and generation ramp rates are evaluated using field tests on thermal units. Frequency bias for the area control error calculation is also presented. Test procedures for each parameter calculation are described in detail for thermal units of 1, 3, and 3.75 MW installed at Ecuadorian oil well facilities. Test results for these units demonstrate the practicability of the proposed test procedures. [ABSTRACT FROM AUTHOR]

This paper proposes the design of a novel dc excitation control for a wound-rotor induction generator (WRIG) under autonomous-generation mode using a microcontroller based on a reduced instruction set chip (RISC). The source of the dc excitation control for the studied WRIG is obtained from its generated ac voltage through a step-down transformer, a bridge rectifier, and a dc-to-dc buck converter. In order to effectively modulate the desired dc voltage for controlling the generated voltage of the WRIG, a fuzzy controller embedded in the RISC-based microcontroller is properly designed and implemented using the PIC 8-bit microcontroller under voltage variations. The calculation results are sent to the pulsewidth-modulation ports to drive the power MOSFET switch of the dc-to-dc buck converter. The proposed WRIG system with its dc excitation control is practically implemented in a laboratory wound-rotor induction machine driven by a dc motor. From both experimental measurements and computer simulations, it can be concluded that the proposed isolated WRIG with its dc excitation controlled by the microcontroller can provide better voltage profile than a self-excited induction generator containing only excitation capacitors under various loading and switching conditions. [ABSTRACT FROM AUTHOR]

This paper describes the operation of a direct-drive brushless generator for a Bristol Cylinder ocean wave device. This is a very low-speed device; thus, the pole number and diameter are very large. Although the machine may be large, its pole pitch and axial length is low. The application is described and simulated using analytical and finite-element analysis techniques. A 248-pole design with surface rotor magnets is developed with both surface and slotted windings. An analysis of the control is put forward. [ABSTRACT FROM AUTHOR]

This paper proposes a space-vector modulation (SVM)-based direct-torque control (DTC) scheme for a permanent-magnet synchronous generator (PMSG) used in a variable-speed direct-drive wind power generation system. A quasi-sliding-mode observer that uses a relatively low sampling frequency, e.g., 5 or 10 kHz, is proposed to estimate the rotor position and stator flux linkage based on the current model of the PMSG over a wide operating range. The optimal torque command is directly obtained from the estimated rotor speed for the DTC by which the maximum power point tracking control of the wind turbine generator is achieved without the need for wind speed or rotor position sensors. Compared with the conventional DTC, the proposed SVM-DTC achieves a fixed switching frequency and greatly reduces the flux and torque ripples, while retaining the fast dynamic response of the system. The effectiveness of the proposed SVM-DTC scheme is verified by simulation studies on a 1.5-MW PMSG wind turbine and is further verified by experimental results on a 2.4-kW PMSG with a 10-kHz sampling frequency. [ABSTRACT FROM AUTHOR]

Pulsed power applications are widespread, ranging from microscopic devices up to systems that are major installations and cost many millions of dollars. This paper describes some of the approaches used for the larger systems that have been built and discusses their engineering challenges. Basic energy storage approaches include electrostatic (capacitors), magnetic (inductors), inertial (flywheels), electrochemical (batteries), and fuel or explosives. Systems based on these approaches each have their own requirements and challenges but also have many common components. An example of one potential future large-scale opportunity—launch to space—is given and the need to develop more competitive economic approaches is discussed. [ABSTRACT FROM PUBLISHER]

This paper presents a novel method to identify the fault that would affect the transient stability of one machine to an infinite bus. Here, the swing equation of each machine is expressed in the form of a closed-loop transfer function in Laplacess-domain. In the transfer function, the duration of the fault and the changes in maximum electrical power output of the machine during and after the fault are considered. Then, the real value of the dominant root of each machine's characteristic equation is identified on the real axis of thes-plane. In this method, the generator has been considered unstable based on the position of the real value of the dominant root in the left half or very close to the imaginary axis or in the right half of thes-plane. The results obtained by the proposed method are compared with those of the conventional step-by-step method on the basis of different fault clearing times, and good agreements have been demonstrated. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper presents an approach to the allocation and designs the PSSs. [•] The proposed approach has succeeded in determining the dominant generator. [•] Paper proposed a model for designing PSS regarding oscillation modes of the power. [Copyright &y& Elsevier]

In this paper swallowtail catastrophe is used to determine the transient stability regions. The bifurcation set represents the transient stability region in terms of power system transient parameters bounded by the transient stability limits. The system modelling is generalized in such, that the analysis could handle either one or any number of critical machines. This generalized model is then tested on a New England 39bus 10-machine power system. The results of the stability analysis done with the generalized method are compared with the time solution and the results were satisfactory. The transient stability regions determined are valid for any changes in loading conditions and fault location. This method is a good candidate for on-line assessment of transient stability of power systems. [ABSTRACT FROM AUTHOR]

The training tool presented here is integrated into a set of electric machine and power electronic training tools (EM&PETT) at the Basque Country University and consists of a motor-generator group with two twin 30 W permanent magnet d.c. motors, three batteries and an array of three solar panels. Speed and torque control methods for d.c. machines, tracking of maximum power point algorithms for photovoltaic systems and control of energy recovery of the d.c. generator when it works as an active mechanical load are experimental procedures within the scope of the EM&PETT. The fundamental idea behind this training tool is to introduce engineering students to the concepts of electric propulsion control through electronic power converters, with energy efficiency criteria and solar energy generation. Finally, both the operation and adjustment of the system and the display of the variables that are included in the EM&PETT can be done locally or remotely by several users. [ABSTRACT FROM AUTHOR]

Some high-torque electric machines, such as low-speed wind generators, may be very difficult to test on load because of the large and expensive mechanical equipment required to load them (motors) or to drive them (generators). In this paper, a full-load regenerative testing methodology is described which does not require any rotating equipment to be coupled to the machine where the rated active power flows in a closed loop between the machine and a suitably connected dual-stage converter. The successful application of this methodology to a 780-kW 14-r/min wind generator prototype is addressed as a study case. Relevant experimental results are reported in a companion paper. [ABSTRACT FROM AUTHOR]

The accurate calculation of iron loss from finite-element analysis in electrical machines is essential if optimal machines are to be designed. This paper conducts a holistic review of the extensive literature field before examining, in detail, several methods in order to recommend an optimum engineering solution. Both frequency domain and time domain methods are discussed including the use of different orthogonal components as well as the relative merits of using all, or some, of the eddy current, anomalous, and hysteresis loss components. A theoretical cubic meter of iron is simulated to quickly demonstrate the inaccuracies of Cartesian coordinate methods before calculations on several manufactured machines are undertaken showing the superior accuracies of major/minor loop calculation. Calculation undertaken using the radial tangential orthogonal plane is shown to have less than 1% average difference to that of the major/minor loop yet is over six times quicker. The peak percentage error in an individual element is shown to be less than 5%. Discussions are also made regarding the method of curve fitting to gain loss constants and any possible sources of inaccuracy particularly during manufacture. [ABSTRACT FROM PUBLISHER]

Manufacturing processes may introduce a significant variability on the magnetic properties of claw pole generator stators. The present work deals with the analysis of two groups of stator samples. The first group is composed of 28 slinky stators (SS) and the second group is composed of 5 stators, manufactured using laser cut stacked laminations (SL). Both groups are made from the same lamination grade and with the same geometrical dimensions. Characterization was carried out for several levels of excitation field at 50 Hz. A noticeable variability has been observed on the iron losses for SS samples, whereas it appears to be not significant for SL samples. The loss separation technique has then been investigated for the SS samples. Results show that the variability of static losses is more important than the one of dynamic losses. [ABSTRACT FROM PUBLISHER]

This paper deals with a permanent magnet (PM) brushless machine used for integrated starter generator (ISG) in an electric vehicle (EV) onboard range extender (ORX). Proper machine configuration selection is briefly introduced. Then, ISGs with both surface-mounted PM (SPM) and interior PM (IPM) rotors have been developed for comparatively analysis. Some techniques for eddy current loss reduction are discussed, while influence of the rotor protecting sleeve material and thickness, axial segmental sleeves, and short circuit rings (ShCRs) around each magnet are particularly investigated. Subsequently, experimental results as of the starter and generator are presented respectively. Moreover, cost evaluation is also presented. [ABSTRACT FROM PUBLISHER]

The design of the load current multiplier with a 1.75-current enlargement factor, when the pulse amplitude of the current through a 3-MA load of the МИГ terawatt pulse generator (multifunction pulse generator), is described, and its operation is demonstrated. The design of the multiplier is sufficiently simple, and it is easily demounted, allowing one to use the МИГ generator in other operation modes with different-impedance loads. It is shown that it is expedient to use the multiplier for operation with static low-inductance loads, e.g., in studies of the skin electric explosion or nonlinear diffusion of megagauss magnetic fields. In this case, the multiplier application is intended to ensure a one-and-one-half increase in the current through the load as compared to the standard operation mode of the МИГ generator. [ABSTRACT FROM AUTHOR]

This paper proposes a strategy of flicker mitigation for doubly-fed induction generator (DFIG) wind turbine systems. In the weak grid system where the grid impedance ratio is low, the reactive power compensation only cannot suppress the flicker sufficiently due to the limited power capacity of the converters or the DFIG. For the full suppression of flickers, the active power smoothening using the energy storage system (ESS) needs to be utilized together with the reactive power compensation. The effectiveness of the proposed method is verified by PSCAD/EMTDC simulation results for a 2[MW] DFIG wind turbine system and by experimental results for a 3[kW] wind turbine simulator. [ABSTRACT FROM AUTHOR]