A review of sensorless control in induction machines using HF injection, test vectors and PWM harmonics

This paper gives a review of sensorless methods developed for ac drives’ operation at very low and zero speed. The sensorless drives presented in this paper use reluctance spatial anisotropy to track the mechanical rotor position, allowing the use of vector control. To extract the position information additional test signals in form of active vector pulses or continuous high frequency signals are injected into the machine. This paper also presents a technique which does not make use of additional test signals, but only components resulting from the inverter PWM pattern. Practical results show that with all reviewed methods sensorless vector control at very low and zero speed is possible. However, disturbances (eg. coming from the inverter or magnetic saturation) affect the position signal significantly and require appropriate compensation.peer-reviewe

A review of saliency-based sensorless control methods for alternating current machines

Operation of model-based sensorless control of Alternating Current machines at low and zero speeds is unreliable and can fail. To overcome the limitations of sensorless control at low speeds, several alternative techniques have been developed to estimate speed and position. These are mainly based on detecting machine saliencies by measuring the response of the current to some form of voltage injection. This paper discusses injection methods, machine saliencies, and techniques used to extract speed and position that are applicable to both induction machines and permanent magnet synchronous motors.peer-reviewe

A review of sensorless control in induction machines using HF injection and test vectors

This paper describes various methods aimed at tracking the flux and rotor position for cage induction machines without a shaft sensor using specially designed saliencies or natural saliencies. The estimation methods employ a High Frequency (HF) signal or test vectors to detect the machine saliency. As is common knowledge, multiple saliences can cause problems to track only one particular saliency. Ways to overcome this problem for rotor position and rotor flux tracking are discussed. The performance of these methods is investigated at all loads at low and zero speed and also at zero fundamental frequency.peer-reviewe

Sensorless control of AC machines for low and zero speed operation without additional test signal injection

This work considers the sensorless control of AC machines for the low and zero speed operation range. Two novel techniques have been developed that use the inherit nature of the inverter PWM to estimate the rotor position of the machine. The inherent back EMF and the saliency of AC machines can be utilized to identify the rotor/flux position. The zero vector current derivative (ZVCD) technique for permanent magnet synchronous machines (PMSM) utilizes both of these effects. No additional test signals are injected into the machine and the difficulty in sensing the machine terminal voltage at low speed is eased. Only three standard current transducers are used in the drive system. For the position/ speed estimator only the machine current derivative during the relatively long (at low speed) zero voltage vectors is used for obtaining the rotor position. Practical results show the operation of the drive at several torque and speed conditions including stand still. A further method has been developed for the sensorless control of induction machines. The high frequency harmonics present in a PWM inverter drive system can be used to detect an equivalent impendence saliency that shows modulation due to rotor/ flux position saliency. The proposed method focuses particularly on the extraction of spatial saliency modulation due to rotor bar slotting effect, which can be used to determine the mechanical rotor position. No additional signal injection is required; the method simply employs some of the inherent PWM carrier harmonics

Sensorless control of AC machines for low and zero speed operation without additional test signal injection

This work considers the sensorless control of AC machines for the low and zero speed operation range. Two novel techniques have been developed that use the inherit nature of the inverter PWM to estimate the rotor position of the machine. The inherent back EMF and the saliency of AC machines can be utilized to identify the rotor/flux position. The zero vector current derivative (ZVCD) technique for permanent magnet synchronous machines (PMSM) utilizes both of these effects. No additional test signals are injected into the machine and the difficulty in sensing the machine terminal voltage at low speed is eased. Only three standard current transducers are used in the drive system. For the position/ speed estimator only the machine current derivative during the relatively long (at low speed) zero voltage vectors is used for obtaining the rotor position. Practical results show the operation of the drive at several torque and speed conditions including stand still. A further method has been developed for the sensorless control of induction machines. The high frequency harmonics present in a PWM inverter drive system can be used to detect an equivalent impendence saliency that shows modulation due to rotor/ flux position saliency. The proposed method focuses particularly on the extraction of spatial saliency modulation due to rotor bar slotting effect, which can be used to determine the mechanical rotor position. No additional signal injection is required; the method simply employs some of the inherent PWM carrier harmonics

Sensorless position control of induction machines using high frequency signal injection

The aim of this research project was to develop a position controlled induction machine vector drive operating without a speed or position sensor but having a dynamic performance comparable to that of a sensored position vector drive. The methodology relies on the detection of a rotor saliency in the machine by persistent high-frequency voltage injection. The rotor position is then estimated from the resulting stator current harmonics that are modulated by the spatial rotor saliency. This can be a built-in rotor saliency (a designed asymmetry) or the natural saliency due to rotor slotting. This project investigates the demodulation of the extracted high-frequency current spectrum and different topologies for the estimation of rotor position. The tracking of rotor position through rotor saliencies helps to overcome the limitations of model-based approaches that are restricted to speeds above 30rpm on a 4-pole machine and are sensitive to parameter mismatches. The project addresses the difficult problem of separating the modulation effects due to the rotor saliency from distorting modulations due to the saturation saliency and inverter effects. In previous research it had been found that the saturation saliency causes a deterioration of the position estimate that can result in a loss of position and eventually causes the drive to fail. The application of filters to remove the interfering saturation harmonics is not possible. In this research a new approach was developed that compensates online for the saturation effect using pre-commissioned information about the machine. This harmonic compensation scheme was utilized for a 30kW, 4-pole induction machine with asymmetric rotor and enabled the operation from zero to full load and from standstill up to about ±150rpm (±5Hz). The steady-state performance and accuracy of the resulting sensorless drive has been found to operate similarly to a sensored drive fitted with a medium resolution encoder of 600ppr. The project involved studies of the inverter switching deadtime and its distorting effect on the position estimation. A second compensation strategy was therefore developed that is better suited if a large interfering modulation due to the inverter deadtime is present in the machine. The new compensation method was implemented for a second 30kW machine that utilizes the rotor slotting saliency. Good tracking results were obtained with a mean error of less than ±0.5° mechanical under steady-state. The derivation of the position signal for higher speeds introduces an additional speed-dependent error of about 4° mechanical at 170rpm. Sensorless position control was realized for operation from zero to full load for the fully fluxed machine. The performance allowed low and zero speed operation including position transients reaching a speed of 50rpm. The high-frequency modulation introduced by the fundamental currents during transient operation was examined and identified as the main factor limiting the dynamics of the sensorless drive. Two rigs were used for the research. The first rig is build around a network of Transputers, the second rig uses state-of-the-art TMS320C40 and TMS320F240 digital signal processors for the control and was designed and constructed as part of the research

A precise, General, Non-Invasive and Automatic Speed Estimation Method for MCSA Steady-State Diagnosis and Efficiency Estimation of Induction Motors in the 4.0 Industry

Tesis por compendio[ES] Hay dos aspectos cruciales a la hora de operar motores de inducción en la industria: la estimación de su eficiencia (para minimizar el consumo de energía) y su diagnóstico (para evitar paradas intempestivas y reducir los costes de mantenimiento). Para estimar la eficiencia del motor es necesario medir tensiones y corrientes. Por ello, resulta conveniente y muy útil utilizar la misma corriente para diagnosticar también el motor (Motor Current Signature Analysis: MCSA). En este sentido, la técnica MCSA más adecuada es aquella basada en la localización de armónicos de fallo en el espectro de la corriente de línea del estator en régimen permanente, pues esta es la condición de funcionamiento de la mayoría de los motores de inducción de la industria. Por otro lado, dado que la frecuencia de estos armónicos depende de la velocidad, resulta imprescindible conocer esta magnitud con precisión, ya que esto permite localizar correctamente los armónicos de fallo, y, por tanto, reducir las posibilidades de falsos positivos/negativos. A su vez, una medida precisa de la velocidad también permite calcular con precisión la potencia mecánica, lo que se traduce en una estimación más exacta del rendimiento. Por último, para adaptarse a las necesidades de la Industria 4.0, en la que se monitoriza continuamente un gran número de motores, la velocidad también debe ser obtenida de manera no invasiva, automática y para cualquier motor de inducción. A este respecto, dado que la medición precisa de la velocidad a través de un encóder es invasiva y costosa, las técnicas de estimación de velocidad sin sensores (SSE en inglés) se convierten en la mejor opción. En la primera parte de esta tesis se realiza un análisis exhaustivo de las familias de técnicas SSE presentes en la literatura técnica. Como se demuestra en ella, aquellos métodos basados en armónicos de ranura (RSHs en inglés) y en armónicos laterales de frecuencia rotacional (RFSHs) son potencialmente los únicos que pueden satisfacer todos los requisitos mencionados anteriormente. Sin embargo, como también se demuestra en esta parte, y hasta esta tesis, siempre había existido un compromiso entre la precisión (característica de los RSHs) y la aplicabilidad general del método (característica de los RFSHs). En la segunda parte, y núcleo de esta tesis, se presenta una metodología que acaba con este compromiso, proporcionando así el primer método de estimación de velocidad preciso, general, no invasivo y automático para el diagnóstico en estado estacionario MCSA y la estimación de la eficiencia de motores de inducción que operan en un contexto de Industria 4.0. Esto se consigue desarrollando una novedosa técnica basada en RSHs que, por primera vez en la literatura técnica, elimina la necesidad de conocer/estimar el número de ranuras del rotor, lo que había impedido hasta la fecha que estos métodos fueran de aplicación general. Esta técnica proporciona además un procedimiento fiable y automático para localizar la familia de RSHs en el espectro de la corriente de línea de un motor de inducción. De igual forma y sin la ayuda de un experto, la técnica es capaz de determinar los parámetros necesarios para estimar la velocidad a partir de los RSHs, utilizando medidas tomadas en régimen estacionario. La metodología es validada utilizando motores con diferentes características y tipos de alimentaciones, empleando para ello simulaciones, pruebas de laboratorio y 105 motores industriales. Además, se muestra un caso de aplicación industrial en el que el algoritmo desarrollado se implementa en un sistema de monitorización continua mediante MCSA, lo que acaba conduciendo al descubrimiento de un nuevo fallo en motores sumergibles de pozo profundo: el desgaste de los anillos de cortocircuito. Por último, se presenta una segunda aplicación directa para este tipo de motores derivada del procedimiento de detección de RSHs: el uso de estos armónicos para diagnosticar, en fase temprana, cortocircuitos entre espiras.[CA] Hi ha dos aspectes crucials a l'hora d'operar motors d'inducció en la indústria: l'estimació de la seua eficiència (per a minimitzar el consum d'energia) i el seu diagnòstic (per a evitar parades intempestives i reduir els costos de manteniment). Per a estimar l'eficiència del motor és necessari mesurar tensions i corrents. Per això, resulta convenient i molt útil utilitzar el mateix corrent per a diagnosticar també el motor (Motor Current Signature Analysis: MCSA). En aquest sentit, la tècnica MCSA més adequada és aquella basada en la localització d'harmònics de fallada en l'espectre del corrent de línia de l'estator en règim permanent, ja que aquesta és la condició de funcionament de la majoria dels motors d'inducció de la indústria. D'altra banda, atés que la freqüència d'aquests harmònics depén de la velocitat, resulta imprescindible conéixer aquesta magnitud amb precisió, ja que això permet localitzar correctament els harmònics de fallada i, per tant, reduir les possibilitats de falsos positius/negatius. Al seu torn, una mesura precisa de la velocitat també permet calcular amb precisió la potència mecànica, la qual cosa es tradueix en una estimació més exacta del rendiment. Finalment, per a adaptar-se a les necessitats de la Indústria 4.0, en la qual es monitora contínuament un gran nombre de motors, la velocitat també ha de ser obtinguda de manera no invasiva, automàtica i per a qualsevol motor d'inducció. En aquest sentit, atès que el mesurament precís de la velocitat a través d'un encóder és invasiva i costosa, les tècniques d'estimació de velocitat sense sensors (SSE en anglés) es converteixen en la millor opció. En la primera part d'aquesta tesi es realitza una anàlisi exhaustiva de totes les famílies de tècniques SSE presents en la literatura tècnica. Com es demostra en ella, aquells mètodes basats en harmònics de ranura (RSHs en anglès) i harmònics laterals de freqüència rotacional (RFSHs en anglés) són els més prometedors, ja que son potencialment els únics que poden satisfer tots els requisits esmentats anteriorment. No obstant això, com també es demostra en aquesta part, i fins a aquesta tesi, sempre havia existit un compromís entre la precisió (característica dels RSHs) i l'aplicabilitat general del mètode (característica dels RFSHs). En la segona part, i nucli d'aquesta tesi, es presenta una metodologia que acaba amb aquest compromís, proporcionant així el primer mètode d'estimació de velocitat precís, general, no invasiu i automàtic per al diagnòstic en estat estacionari MCSA i l'estimació de l'eficiència de motors d'inducció que operen en un context d'Indústria 4.0. Això s'aconsegueix desenvolupant una nova tècnica basada en RSHs que, per primera vegada en la literatura tècnica, elimina la necessitat de conéixer/estimar el nombre de ranures del rotor, cosa que havia impedit fins avui que aquests mètodes foren d'aplicació general. Aquesta tècnica proporciona a més un procediment fiable i automàtic per a localitzar la família de RSHs en l'espectre del corrent de línia d'un motor d'inducció. De la mateixa forma i sense l'ajuda d'un expert, la tècnica és capaç de determinar els paràmetres necessaris per a estimar la velocitat a partir dels RSHs, utilitzant mesures preses en règim estacionari. La metodologia és validada utilitzant motors amb diferents característiques i condicions d'alimentació, emprant per a això simulacions, proves de laboratori i 105 motors industrials. A més, es mostra un cas real d'aplicació industrial en el qual l'algoritme desenvolupat és implementat en un sistema de monitoratge continu mitjançant MCSA, la qual cosa acaba conduint al descobriment d'una nova fallada en motors submergibles de pou profund: el desgast dels anells de curtcircuit. Finalment, es presenta una segona aplicació directa per a aquest tipus de motors derivada del procediment de detecció de RSHs: l'ús d'aquests harmònics per a diagnosticar, en fase primerenca, curtcircuits entre espires.[EN] There are two crucial aspects when operating induction motors in industry: efficiency estimation (to minimize energy consumption) and diagnosis (to avoid untimely outages and reduce maintenance costs). To estimate the motor's efficiency, it is necessary to measure voltages and currents. Hence, it is convenient and very useful using the same current to also diagnose the motor (Motor Current Signature Analysis: MCSA). In this regard, the most suitable MCSA technique is that based on locating fault harmonics in the spectrum of the stator line current under steady-state, as this is the operating condition of most induction motors in industry. Since the frequency of these harmonics depends on the speed, it becomes essential to be able to know this magnitude with precision, as this makes it possible to correctly locate the fault harmonics, and therefore, reduce the chances of false positives/negatives. In turn, an accurate speed information also allows to calculate the mechanical power with precision, which results in a more accurate estimation of the motor performance. Finally, to adapt to the needs of 4.0 Industry, where large numbers of motors are continuously monitored, the speed must not only be obtained very accurately, but also non-invasively, automatically (without the need for an expert) and for any induction motor. In this regard, since precise speed measurement through a shaft sensor is invasive and expensive, Sensorless Speed Estimation (SSE) techniques become the best option. The first part of this thesis conducts a thorough analysis of all the families of SSE techniques present in the technical literature. As demonstrated therein, those techniques based on Slotting and Rotational Frequency Sideband Harmonics are the most promising, as they can potentially meet all the aforementioned requirements. However, as also proved in this part, and up to this thesis, there had always been a trade-off between accuracy, characteristic of Rotor Slot Harmonics (RSHs), and general applicability, characteristic of Rotational Frequency Sideband Harmonics (RFSHs). The second part, and core of this thesis, presents a methodology that ends with this trade-off between accuracy and general applicability, thus providing the first precise, general, noninvasive and automatic speed estimation method for MCSA steady-state diagnosis and efficiency estimation of induction motors that operate in a 4.0 Industry context. This is achieved by developing a novel RSH-based technique that, for the first time in technical literature, eliminates the need to know/estimate the number of rotor slots, which had so far prevented these techniques to be generally applicable. This technique also provides a reliable and automatic procedure to, from among the high number of significant harmonics present in the spectrum of the line current of an induction motor, locate the RSHs family. Also automatically and without the help of an expert, the technique is able to determine the parameters needed to estimate speed from RSHs, using only measurements taken during the motor normal operation at steady-state. The methodology is validated using motors with different characteristics and supply conditions, by simulations, lab tests and with 105 industrial motors. Furthermore, a real industrial case of application is shown as well, where the speed estimation algorithm is implemented in a continuous motor condition monitoring system via MCSA, which eventually leads to the discovery of a new fault in deep-well submersible motors: the wear of end-rings. Finally, a second direct application derived from the reliable and automatic procedure to detect RSHs is presented: the use of these harmonics to diagnose early-stage inter-turn faults in induction motors of deep-well submersible pumps.Bonet Jara, J. (2023). A precise, General, Non-Invasive and Automatic Speed Estimation Method for MCSA Steady-State Diagnosis and Efficiency Estimation of Induction Motors in the 4.0 Industry [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/194269Compendi

Sensorless control of surface mounted permanent magnet machine using fundamental PWM excitation

This thesis describes the development of a sensorless control method for a surface mounted permanent magnet synchronous machine drive system. The saturation saliency in the machine is tracked from the stator current transient response to the fundamental space vector PWM (pulse width modulation) excitation. The rotor position and speed signals are obtained from measurements of the stator current derivative during the voltage vectors contained in the normal fundamental PWM sequence. In principle, this scheme can work over a wide speed range. However, the accuracy of the current derivative-measurements made during narrow voltage vectors reduces. This is because high frequency current oscillations exist after each vector switching instant, and these take a finite time to die down. Therefore, in this thesis, vector extension and compensation schemes are proposed which ensure correct current derivative measurements are made, even during narrow voltage vectors, so that any induced additional current distortion is kept to a minimum. The causes of the high frequency switching oscillations in the AC drive system are investigated and several approaches are developed to reduce the impact of these oscillations. These include the development of a novel modification to the IGBT gate drive circuit to reduce the requirement for PWM vector extension. Further improvements are made by modifications to the current derivative sensor design together with their associated signal processing circuits. In order to eliminate other harmonic disturbances and the high frequency noise appearing in the estimated position signals, an adaptive disturbance identifier and a tracking observer are incorporated to improve the position and speed signals. Experimental results show that the final sensorless control system can achieve excellent speed and position control performance

Stator inter-turn faults diagnosis in induction motors using zero-sequence signal injection

This study presents a strategy for stator inter-turn faults diagnosis in induction motors (IMs) operating under timevariable load and time-variable speed conditions. The strategy consists in injecting a zero-sequence high-frequency signal in order to analyse variations in the stator inductances. Incipient stator inter-turn faults are detected by a simple signal processing of the derivatives of the currents. A feature of the strategy is that the zero-sequence high-frequency signal is generated by the inverter that feeds the machine, without modifying the standard space vector modulation of the IM-drive. Experimental results show that faults representing <1% of the stator winding can be detected, as well as the phase location of the fault, validating this proposal.Fil: Otero, Marcial. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; ArgentinaFil: de la Barrera, Pablo Martin. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; ArgentinaFil: Bossio, Guillermo Rubén. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; ArgentinaFil: Leidhold, Roberto. Otto-von-Guericke-Universität Magdeburg; Alemani