Identification of the Induction Motor Parameters at Standstill Including the Magnetic Saturation Characteristics

Identification of the induction motor parameters at standstill is studied in this thesis. The main goal of this work is to search for the feasible and applicable speed sensorless self-commissioning schemes. The magnetic saturation of the magnetizing inductance is taken into account. The magnetizing inductance is modeled as a function of the stator flux. Two different identification schemes are chosen based on the literature review. First method uses the single-axis sinusoidal excitation as the test signal. Second method uses the DC-decay test for the magnetizing inductance estimation and DC-biased sinusoidal excitation for the leakage inductance and rotor resistance identification. The DC-decay test is found to be a suitable method for identification of the magnetizing inductance. The single-axis sinusoidal excitation is found to be problematic in the saturation region. The source of the inaccuracy in the single-axis sinusoidal excitation is studied and the reasons are explained. The sensitivity of the schemes to the stator resistance and stator voltage errors is evaluated. Both methods show a very high sensitivity to the stator voltage errors in the case of the magnetizing inductance estimation. However, the DC-decay test shows a lower estimation error in the presence of the stator resistance errors. The estimation of the leakage inductance is robust against the stator voltage errors when the method based on the single-axis sinusoidal excitation is used. The estimation of the rotor resistance using the DC-biased excitation depends on the DC offset current in the presence of both the stator resistance and stator voltage errors

Rotor parameter identification of saturated induction machines

An induction machine model is proposed for the identification of rotor parameters using high-frequency signal injection. The model includes both the magnetic saturation caused by the fundamental-wave components and the frequency dependence encountered in the signal injection method. Both the skin effect in the rotor winding and the eddy current losses in the rotor core are taken into account. Sinusoidal signal injection is used at several frequencies, and the model parameters are fitted to the results. The rotor leakage inductance and the rotor resistance valid at low slip frequencies are also obtained from the model directly. Experimental results for a 45-kW machine are presented. It is shown that the model fits well to the measured data in various operating points, and the accuracy of the identified parameters is good.Peer reviewe

Identifikacija parametara asinkronog motora na temelju pokusa zaleta i zaustavljanja

In this paper, a newstep-by-step approach to identifythe parameters ofan induction machine combining free acceleration and deceleration transient data is presented. The measurement ofthe statorline voltages and currents is required only. The free acceleration torque characteristic is used in orderto identifythe inertia and to avoid the influence ofthe harmonic fields effect on the identification accuracy. The rotorresistance is identified from both free acceleration and deceleration transients data, and in that waythe skin effect factoris determined. The identification results are compared with the motorparameters obtained byperforming locked-rotorand no-load tests.U ovom je radu predstavljen jedan novi postupak za identifikaciju parametara asinkronog motora koji se temelji na pokusima zaleta i zaustavljanja neopterećenog motora. Pritom se zahtjeva samo mjerenje statorskih napona i struja. Momentna karakteristika motora dobivena iz mjerenja u pokusu zaleta koristi se za određivanje inercije. Na taj način izbjegnut je utjecaj viših prostornih harmonika polja na točnost identifikacijskog postupka. Otpor rotora određuje se iz pokusa zaleta i iz pokusa zaustavljanja, čime je posredno određen i faktor potiskivanja struje. Rezultati dobiveni identifikacijskim postupkom uspoređeni su s parametrima motora dobivenima iz pokusa praznog hoda i kratkog spoja

Parameter Estimation of Induction Machine at Standstill Using Two-Stage Recursive Least Squares Method

This paper presents a two-stage recursive least squares (TSRLS) algorithm for the electric parameter estimation of the induction machine (IM) at standstill. The basic idea of this novel algorithm is to decouple an identifying system into two subsystems by using decomposition technique and identify the parameters of each subsystem, respectively. The TSRLS is an effective implementation of the recursive least squares (RLS). Compared with the conventional (RLS) algorithm, the TSRLS reduces the number of arithmetic operations. Experimental results verify the effectiveness of the proposed TSRLS algorithm for parameter estimation of IMs

Using stator discharge current for the parameter estimation of a single-phase axial flux induction motor

AbstractBecause Axial Flux Induction Motors (AFIMs) have many advantages over radial flux (conventional) ones, they are increasingly used in industrial applications. So, their performance prediction is an important issue. On the other hand, parameter estimation is an inseparable part of performance prediction. In this paper, a new method, based on the discharge current of stator windings, is presented. In the proposed method, theoretical and practical discharge currents are compared to calculate coefficients, time constants and parameters. Then, calculated parameters are employed in the d-q model of the AFIM. Finally, 3-D finite element analysis and experimental tests are used to verify the proposed method

Онлайн-идентификация электромагнитных параметров асинхронного двигателя

Incompliance of the settings of the system to control actual values of the parameters of a variable frequency induction electric drive may sometimes result in complete non-operability of a variable frequency electric drive as well as in the considerable reduction of the dynamic quality parameters. Such parameters as active rotor resistance, rotor inductance, and inductance of the magnetization circuit are available for the immediate measuring. They are not identified in terms of the acceptance tests, and the values presented in catalogues and reference books are calculated ones that may differ considerably from the real values of a certain machine. Despite constant studies by the researchers, a task to identify electromagnetic parameters of the equivalent circuit of an induction motor is still important and topical. The objective of the paper is to develop a method of online-identification of the electromagnetic parameters of an induction motor making it possible to implement accurate regulator adjustment of the frequency control system in terms of operational changes in the driving motor parameters. For the first time, the paper analyzes a steady mode of induction motor operation which does not apply T-network of the equivalent circuit of an induction motor. An approach has been proposed relying on the equation of an induction motor in three-phase fixed coordinate system obtained on the basis of the theory of generalized electromechanical converter. Несоответствие настроек системы  управления  фактическим  значениям  параметров частотно-регулируемого  асинхронного  электропривода  может  иногда  приводить  к  полной неработоспособности частотного электропривода, к существенному снижению динамических показателей качества. Такие параметры, как активное сопротивление и индуктивность ротора, индуктивность цепи намагничивания, недоступны для непосредственного измерения. При приемо-сдаточных испытаниях они не определяются, а величины, приводимые в каталогах и справочниках, являются расчетными и могут существенно отличаться от реальных значений конкретной машины. Несмотря на постоянные усилия исследователей, задача идентификации электромагнитных параметров схемы замещения асинхронного двигателя остается важной и актуальной. Авторы статьи разработали метод онлайн-идентификации электромагнитных параметров асинхронного двигателя, что позволит реализовать точную настройку регуляторов системы частотного управления при эксплуатационных изменениях характеристик приводного двигателя. Выполнен анализ установившегося режима работы асинхронного двигателя без использования Т-образной схемы его замещения. Предложен подход, опирающийся на уравнения асинхронного двигателя в трехфазной неподвижной системе координат, полученные на основе теории обобщенного электромеханического преобразователя. С учетом аналитических преобразований этих формул получена система нелинейных алгебраических уравнений четвертого порядка, решение которой позволяет определить активное сопротивление ротора, сопротивление рассеивания и главную взаимную индуктивность асинхронного двигателя в предположении, что активное сопротивление статора известно. Произведена верификация предлагаемого метода. На основании данных установившегося режима работы асинхронного двигателя типа 4А250М2УЗ выполнена идентификация его электромагнитных параметров, исследовано влияние начального приближения на точность полученных результатов, которые подтверждают работоспособность рассматриваемого метода идентификации

Induction motor parameter identification in elevator drive modernization

Tässä työssä tutkitaan, miten oikosulkumoottorin sähköiset parametrit voidaan identifioida askel- ja taajuusvastemenetelmien avulla pyörittämättä roottoria. Oikosulkumoottoria voimanlähteenä käyttävien hissien ohjaustarkkuus riippuu pitkälti siitä, miten tarkasti taajuusmuuttajan momentti- ja nopeussäätäjän parametrit vastaavat todellisia varsinkin, jos hissin paikkaa tai nopeutta ei mitata. Vanhojen hissien modernisoinnin yhteydessä ongelmaksi muodostuu se, että olemassa olevaa moottoria ei voi identifioida perinteisillä oikosulku- ja tyhjäkäyntikokeilla, koska moottoria ei voi pyörittää kuormattomana. Sen sijaan identifiointi voidaan tehdä analysoimalla vaihejännitteitä ja -virtoja, joita esiintyy, kun staattorikäämityksiin syötetään sellainen heräte, joka ei aiheuta pyörivää sähkömagneettista kenttää eikä siten vääntömomenttia. Esitettävässä askelvastemenetelmässä moottoria syötetään tasavirtapulsseilla, jolloin halutut parametrit saadaan, kun vaihejänniteen ja -virran mittaukset prosessoidaan tilamuuttujien suodatuksella ja saatu lineaarinen yhtälöryhmä ratkaistaan rekursiivisella pienimmän neliösumman algoritmilla. Toisessa, taajuusvasteeseen perustuvassa, menetelmässä moottoria syötetään yhtä aikaa sekä tasa- että vaihtovirralla. Tällöin moottorin parametrit voidaan ratkaista vaihejännitteen ja -virran välisen amplitudisuhteen ja vaihe-eron perusteella lasketun moottorin liittimistä näkyvän induktanssin taajuusriippuvuuden avulla. Molempia menetelmiä on tutkittu sekä tietokonesimuloinneilla että kokeellisilla menetelmillä. Tulosten perusteella havaittiin valitun menetelmän olevan kompromissi parametrien tarkkuuden ja testin suoritusajan välillä.A study is presented where an induction motor, whose rotor is not allowed to rotate, is identified using system identification methods based on transient and frequency response tests. Precise control of elevators powered with frequency converter fed induction motors depends on the accuracy of the parameters used in the motor controller, particularly when no external position or speed sensors are used. When an elevator is modernized with a new control system, the old motor cannot be identified with a regular locked rotor and no-load tests as the motor is not allowed to rotate. However, the identification can be performed in such conditions by analyzing the voltages and currents when the motor windings are excited with such an AC or DC that does not produce torque. A step response method is introduced for the DC excitation where the desired motor parameters are obtained as a result when the measured data is processed with state variable filters, and the produced linear system of equations is solved with a recursive least-squares algorithm. The frequency response method presented uses both DC and AC excitation. The method is based on finding the amplitude ratio and the phase difference between the voltage and current phasors using the properties of the Fourier series. This information is then used to calculate the inductance between the motor terminals, from which the other motor parameters can be solved. Both methods are tested with simulations and experiments. The final choice of the proper identification method is found to be a compromise between the parameter accuracy and measurement time

Efficiency improvement of three phase squirrel cage induction motor by controlling the applied voltage to the stator using SIMULINK models

2018 Spring.Includes bibliographical references.Optimizing the efficiency of three phase squirrel cage induction motors (SCIMs) plays a big role in saving electric energy consumption. The purpose of this thesis is to maximize the efficiency of three phase (SCIM) when it runs at speeds greater than the speed at which the efficiency is maximum during normal operation, i.e., rated voltage by decreasing the applied voltage to the stator using MATLAB/SIMULINK. Equivalent circuit and parameter identification of three phase (SCIM) are explained. MATLAB/SIMULINK is employed to identify the motor parameters and to simulate a three phase (SCIM) under different loads. The effect of reducing the voltage on motor characteristics such as the produced torque by the motor, power factor, reactive power, apparent power, output power, rotor speed and magnetizing current is explained

On the identifiability of steady-state induction machine models using external measurements

A common practice in induction machine parameter identification techniques is to use external measurements of voltage, current, speed, and/or torque. Using this approach, it has been shown that it is possible to obtain an infinite number of mathematical solutions representing the machine parameters. This paper examines the identifiability of two commonly used induction machine models, namely the T-model (the conventional per phase equivalent circuit) and the inverse Γ-model. A novel approach based on the alternating conditional expectation (ACE) algorithm is employed here for the first time to study the identifiability of the two induction machine models. The results obtained from the proposed ACE algorithm show that the parameters of the commonly employed T-model are unidentifiable, unlike the parameters of the inverse Γ-model which are uniquely identifiable from external measurements. The identifiability analysis results are experimentally verified using the measured operating characteristics of a 1.1-kW three-phase induction machine in conjunction with the Levenberg-Marquardt algorithm, which is developed and applied here for this purpose

Sensorless control for limp-home mode of EV applications

PhD ThesisOver the past decade research into electric vehicles’ (EVs) safety, reliability and availability has become a hot topic and has attracted a lot of attention in the literature. Inevitably these key areas require further study and improvement. One of the challenges EVs face is speed/position sensor failure due to vibration and harsh environments. Wires connecting the sensor to the motor controller have a high likelihood of breakage. Loss of signals from the speed/position sensor will bring the EV to halt mode. Speed sensor failure at a busy roundabout or on a high speed motorway can have serious consequences and put the lives of drivers and passengers in great danger. This thesis aims to tackle the aforementioned issues by proposing several novel sensorless schemes based on Model Reference Adaptive Systems (MRAS) suitable for limp-home mode of EV applications. The estimated speed from these schemes is used for the rotor flux position estimation. The estimated rotor flux position is employed for sensorless torque-controlled drive (TCD) based on indirect rotor field oriented control (IRFOC). The capabilities of the proposed schemes have been evaluated and compared to the conventional back-Electromotive Force MRAS (back-EMF MRAS) scheme using simulation environment and a test bench setup. The new schemes have also been tested on electric golf buggies. The results presented for the proposed schemes show that utilising these schemes provide a reliable and smooth sensorless operation during vehicle test-drive starting from standstill and over a wide range of speeds, including the field weakening region. Employing these new schemes for sensorless TCD in limp-home mode of EV applications increases safety, reliability and availability of EVs