Load identification of different Halbach-array topologies on permanent magnet synchronous generators using the coupled field-circuit FE methodology

In this paper, the influence of gap consideration on load identification under various Halbach-array-based topologies (HABOs) is investigated while the system is on-duty. The load characteristics of a radial flux generator with closed-slots and the exterior rotor topology is discussed, where the effect of eddy-currents are observed. This comparative study deals with the consideration of the combined moment of inertia calculation that demonstrates how electromagnetic-based post processing calculations are estimated without the aid of nominal machine parameter values. The analysis was performed using a 2-D finite-element simulation of different HABOs with the gap consideration between the segments. Additionally, a comprehensive comparison with no gap is considered. Also, the dynamic analysis using an uncontrolled conventional rectifier model is used to derive effected key output parameters such as torque, output power, power factor, and line-to-line voltage. The major objective of the study is to determine corresponding load results in order to employ the most suitable and capable magnetization topology from the load perspective in the PM synchronous generator (PMSGs). Accordingly, the maximum power (MP) point was carried out to maximize the output DC power. With respect to the combined moment of inertia estimation, the load parameter estimation is verified experimentally on a surface-mounted PMSG using different magnetization topologies. Furthermore, commercial and environmental issues of the project are considered to reduce CO2 emissions as part of green power generation development.Peer ReviewedPostprint (author's final draft

Identification of Synchronous Machine Magnetization Characteristics From Calorimetric Core-Loss and No-Load Curve Measurements

The magnetic material characteristics of a wound-field synchronous machine are identified based on global calorimetric core-loss and no-load curve measurements. This is accomplished by solving a coupled experimental-numerical electromagnetic inverse problem, formulated to minimize the difference between a finite-element (FE) simulation-based Kriging surrogate model and the measurement results. The core-loss estimation in the FE model is based on combining a dynamic iron-loss model and a static vector Jiles-Atherton hysteresis model, the parameters for which are obtained by solving the inverse problem. The results show that reasonable hysteresis loops can be produced for a grid-supplied machine, while for an inverter-supplied machine the limitations in the FE and iron-loss models seemingly exaggerate the area of the loop. In addition, the effect of the measurement uncertainty on the inverse problem is quantitatively estimated.Peer reviewe

Parameter estimation for a synchronous machine

Tämän työn tavoitteena on estimoida tahtikoneen kaksiakselimallin parametrit käyttäen numeerista impulssimenetelmää. Esitetyn menetelmän etu on, että saadut parametrit kuvaavat todellista toimintapistettä, toisin kuin harmonisen taajuusanalyysin ja oikosulkukokeen avulla saadut parametrit. Tahtikoneen parametrit on arvioitu käyttäen lineaarista ja epälineaarista elementtimenetelmämallia. Huomataan, että kyllästyminen ei juuri vaikuta taajuusvasteisiin, kun käytetään 1 % verkkojännitteen RMS-arvon suuruista impulssia. Työssä esitetään Taylorin kehitelmään perustuva lineaarisointimenetelmä tahtikoneen yhtälöille. Lisäksi esitetään laskennallisesti tehokas menetelmä siirtofunktion muodostamiseen, jossa käytetään lineaarisen systeemin esitystä ja tiloja hyväksi. Piirimallille on suoritettu stabiilisuustarkastelu Lyapunovin mielessä. Todetaan, että systeemillä on vain yksi pysyvä tila. Syötetyn impulssin amplitudin suuruuden vaikutusta taajuusvasteeseen elementtimenetelmän epälineaarisessa mallissa tutkitaan käyttämällä erisuuruisia impulsseja. Numeerisen impulssimenetelmän toimivuus on osoitettu todeksi piirimallilla tehtyjen simulaatioiden avulla Simulink-ympäristössä. Piirimallissa on käytetty estimoituja parametreja. Piirimallilla tehtyjen simulaatioiden taajuusvasteet vastasivat hyvin FEM simulaatioilla saatuja taajuusvasteita. Taajuusvasteiden yhteneväisyys osoittaa todeksi käytetyt menetelmät ja numeerisen impulssimenetelmän käyttökelpoisuuden parametrien estimoinnissa.The aim of this study is to estimate two-axis model parameters for a synchronous machine using the numerical impulse method. An advantage of the numerical impulse method over the standstill frequency response and the sudden short circuit tests is that the obtained parameters describe behavior of the machine at the certain operation point. The operation point may be a loaded operation point with a three-phase supply. The parameters of the machine have been estimated using data from linear and nonlinear finite element models. It is seen that saturation does not affect much when an impulse with the amplitude of 1% of the average RMS-value of the line voltages is used. A linearization method based on the Taylor's expansion is presented for synchronous machine equations. In addition, a computationally effective way to establish transfer functions is presented. The transfer function derivation takes advantage of the linear system representation and states of the system. Stability issues concerning the circuit model have been investigated in the sense of Lyapunov. It is taken note that there is only one steady state. The effect of the impulse amplitude in the nonlinear FEM model has been studied by doing different impulse sizes and the frequency responses are compared. The numerical impulse response method is verified using circuit simulations in Simulink. The frequency responses obtained from circuit simulations, with the estimated parameters, match well with the frequency responses of finite element simulations. The similarity verifies the used methods and the applicability of the numerical impulse method in parameter estimation

Nonlinear transient and steady state analysis for self-excited single-phase synchronous reluctance generator

With today\u27s trend for distributed generation and the need for alternative and renewable energy sources, self-excited induction and synchronous reluctance generators have attracted more attention for wind, tidal and hydro power generation applications. Compared to synchronous and DC generators, they have the advantages: they are brushless, they are robust, they do not need DC excitation and they are relatively low cost.;Compared with SEIG, the self-excited reluctance generator (SERG) not only has the advantages of simplicity and ruggedness, but can also have enhanced steady-state characteristics and high efficiency over a wide range of operation. Moreover, its output frequency is determined only by the prime mover speed, rather than by both the load and the prime mover speed as in an induction generator, so SERG can be easily integrated with power electronic devices to implement a control scheme.;Most of the current analyses deal with three-phase reluctance generators, but insufficient attention has been paid to single-phase self-excited reluctance generators (SPSERG). Their unbalanced loads make their analysis more difficult. This research is motivated by the fact that SPSERG provides a good alternative to single-phase induction generators used in stand-alone generation applications. A general methodology is suggested for transient response prediction and steady state performance analysis for the SPSERG type of electric machine.;To establish a design environment, finite element method is an effective tool, which can be integrated in machine modeling to obtain good performance prediction. In this work, an off-line FEM approach is proposed to obtain the saturation characteristics for state space simulation. During the process, transformation between instantaneous inductance and average inductance is investigated. Off-line FEM + SS approach is proved to be a simple and economic method and can fit the experimental results in good accuracy.;Moreover, a steady state model has to be built to reveal the parametric dependence and provide good design guidance. However, because of the unbalanced load and nonlinear feature of the machine, existing models are not suitable for analysis. In this dissertation, a novel inductance-oriented steady state model based on the harmonic balance technique is introduced. The idea is that starting from the inductance determination under certain load, the fluxes can be attained by a nonlinear relationship, after that, the machine variables can be solved according to the fluxes. Comparison between simulation and experiment validates this approach

Simulation Methods for the Transient Analysis of Synchronous Alternators

The integration of unconventional renewable energy sources on the electrical grid poses challenges to the electrical engineer. This chapter focuses on the transient modeling of electrical machines. These models can be used for the design of generator control, the definition of the protection strategies, stability studies, and the evaluation of the electrical; mechanical; and thermal constraints on the machine. This chapter presents three modeling techniques: the standard d-q equivalent model, the coupled-circuit model, and the finite element model (FEM). The consideration of magnetic saturation for the different models is presented. The responses of the different models during three-phase, two-phase, and one-phase sudden short circuit are compared

Iron Loss Computation in a Synchronous Machine from a Static Field Solution

Owing to the increasing energy demand, a highly efficient synchronous machine can play a crucial role in energy saving by reducing energy consumption. An optimum machine design requires a good estimation of the power losses, particularly the iron loss due to the complexity involved with the accurate loss prediction. The prediction of iron loss in the synchronous machine has drawn massive attraction due to the extensive use in the power stations and other industrial applications. The conventional time-stepping method for iron loss calculation is computationally highly expensive and can be productive as long as the number of computations remains in a respectable range. However, the situation is different when an excessive number of computations are required, such as for machine optimization, which turns this method into unprofitable. The development of fast and computationally efficient static analysis in case of synchronous machine induce a thought of computing the iron loss using this method which can minimize the computation cost and substitute the time consuming traditional loss computation method. Based on this notion, an effective iron loss computation technique was developed from a single static field simulation which is much faster than the conventional time-stepping method and provide a fair accuracy. A two-dimensional Finite Element Method was used, and the model was integrated with the static FEM analysis program in the in-house software FCSMEK. The model was applied to a 12.5 MW salient pole synchronous machine, and the computational accuracy was validated with the conventional time-stepping simulation

Improved transistor-controlled and commutated brushless DC motors for electric vehicle propulsion

The development, design, construction, and testing processes of two electronically (transistor) controlled and commutated permanent magnet brushless dc machine systems, for propulsion of electric vehicles are detailed. One machine system was designed and constructed using samarium cobalt for permanent magnets, which supply the rotor (field) excitation. Meanwhile, the other machine system was designed and constructed with strontium ferrite permanent magnets as the source of rotor (field) excitation. These machine systems were designed for continuous rated power output of 15 hp (11.2 kw), and a peak one minute rated power output of 35 hp (26.1 kw). Both power ratings are for a rated voltage of 115 volts dc, assuming a voltage drop in the source (battery) of about 5 volts. That is, an internal source voltage of 120 volts dc. Machine-power conditioner system computer-aided simulations were used extensively in the design process. These simulations relied heavily on the magnetic field analysis in these machines using the method of finite elements, as well as methods of modeling of the machine power conditioner system dynamic interaction. These simulation processes are detailed. Testing revealed that typical machine system efficiencies at 15 hp (11.2 kw) were about 88% and 84% for the samarium cobalt and strontium ferrite based machine systems, respectively. Both systems met the peak one minute rating of 35 hp

Stator current signal crossing for fault diagnosis of self-excited induction generators

This paper presents a novel method for modelling and diagnosis of electrical and mechanical faults in fixed-Speed Self-Excited Induction Generators (SEIGs) operating in autonomous mode in a small-scale wind energy system. The proposed method is validated using the finite element method. After the selection of the magnetising capacitors, the self-excitation process is performed under no-load conditions. Once the stator voltage is established, a symmetrical three-phase load is connected. The fault detection method introduced here is called Stator Current Signal Crossing (SCSC). The SCSC extracts a new signal from the stator currents, that enables the detection of stator inter turn shortcircuits, broken rotor bars, and dynamic eccentricity faults in SEIGs. A spectral analysis of SCSC using the Fast Fourier Transform (FFT) algorithm is used to precisely locate the induced fault components. What sets this fault-tracking method apart from its predecessors is its exceptional ability to detect faults of any magnitude by analysing the modulation of the SCSC signal. These faults are directly identified by the presence of distinct harmonics, each indicative of a specific type of fault. This study also focuses on the SEIG in a wind energy system, whereas previous works have mainly addressed the induction machine in motor mode. In contrast, previous methods involved analysing a single current signal and isolating specific harmonics from a wide frequency range. The effectiveness of the proposed fault detection method and the self-excitation process are illustrated by simulation results and spectral analysis

Modelling and Detecting Faults of Permanent Magnet Synchronous Motors in Dynamic Operations

Paper VI is excluded from the dissertation until the article will be published.Permanent magnet synchronous motors (PMSMs) have played a key role in commercial and industrial applications, i.e. electric vehicles and wind turbines. They are popular due to their high efficiency, control simplification and large torque-to-size ratio although they are expensive. A fault will eventually occur in an operating PMSM, either by improper maintenance or wear from thermal and mechanical stresses. The most frequent PMSM faults are bearing faults, short-circuit and eccentricity. PMSM may also suffer from demagnetisation, which is unique in permanent magnet machines. Condition monitoring or fault diagnosis schemes are necessary for detecting and identifying these faults early in their incipient state, e.g. partial demagnetisation and inter-turn short circuit. Successful fault classification will ensure safe operations, speed up the maintenance process and decrease unexpected downtime and cost. The research in recent years is drawn towards fault analysis under dynamic operating conditions, i.e. variable load and speed. Most of these techniques have focused on the use of voltage, current and torque, while magnetic flux density in the air-gap or the proximity of the motor has not yet been fully capitalised. This dissertation focuses on two main research topics in modelling and diagnosis of faulty PMSM in dynamic operations. The first problem is to decrease the computational burden of modelling and analysis techniques. The first contributions are new and faster methods for computing the permeance network model and quadratic time-frequency distributions. Reducing their computational burden makes them more attractive in analysis or fault diagnosis. The second contribution is to expand the model description of a simpler model. This can be achieved through a field reconstruction model with a magnet library and a description of both magnet defects and inter-turn short circuits. The second research topic is to simplify the installation and complexity of fault diagnosis schemes in PMSM. The aim is to reduce required sensors of fault diagnosis schemes, regardless of operation profiles. Conventional methods often rely on either steady-state or predefined operation profiles, e.g. start-up. A fault diagnosis scheme robust to any speed changes is desirable since a fault can be detected regardless of operations. The final contribution is the implementation of reinforcement learning in an active learning scheme to address the imbalance dataset problem. Samples from a faulty PMSM are often initially unavailable and expensive to acquire. Reinforcement learning with a weighted reward function might balance the dataset to enhance the trained fault classifier’s performance.publishedVersio