Experimental results of vector control for an asynchronous machine

The aim of this article is contributeto the advanced vector control strategy of asynchronous machines. Analyzes of experimental of indirect field-oriented control are presented. In this context, we propose vector control algorithms to provide solutions to the disadvantages of field-oriented control FOC.The results obtained from various methods of determining the parameters for asynchronous machine are compared. We calculate the various parameters and then we present the technical characteristics of each element of the asynchronous machine; finally, we implement the vector control used asbasis of comparison between the simulation under Matlab/Simulink software and experiments. The simulation and experimental tests show that the proposed controller is suitable for medium and high-performance applications

Speed -Sensorless Estimation And Position Control Of Induction Motors For Motion Control Applications

Thesis (Ph.D.) University of Alaska Fairbanks, 2006High performance sensorless position control of induction motors (IMs) calls for estimation and control schemes which offer solutions to parameter uncertainties as well as to difficulties involved with accurate flux and velocity estimation at very low and zero speed. In this thesis, novel control and estimation methods have been developed to address these challenges. The proposed estimation algorithms are designed to minimize estimation error in both transient and steady-state over a wide velocity range, including very low and persistent zero speed operation. To this aim, initially single Extended Kalman Filter (EKF) algorithms are designed to estimate the flux, load torque, and velocity, as well as the rotor, Rr' or stator, Rs resistances. The temperature and frequency related variations of these parameters are well-known challenges in the estimation and control of IMs, and are subject to ongoing research. To further improve estimation and control performance in this thesis, a novel EKF approach is also developed which can achieve the simultaneous estimation of R r' and Rs for the first time in the sensorless IM control literature. The so-called Switching and Braided EKF algorithms are tested through experiments conducted under challenging parameter variations over a wide speed range, including under persistent operation at zero speed. Finally, in this thesis, a sensorless position control method is also designed using a new sliding mode controller (SMC) with reduced chattering. The results obtained with the proposed control and estimation schemes appear to be very compatible and many times superior to existing literature results for sensorless control of IMs in the very low and zero speed range. The developed estimation and control schemes could also be used with a variety of the sensorless speed and position control applications, which are challenged by a high number of parameter uncertainties

Direct torque control of a current source inverter fed induction motor

U disеrtаciјi је prikаzаnа јеdnа nоvа strаtеgiја uprаvlјаnjа аsinhrоnim pоgоnоm sа struјnim prеtvаrаčеm učеstаnоsti zаsnоvаnа nа dirеktnој kоntrоli mоmеntа mоtоrа. Cilј је dа sе оvаkvоm pоgоnu оbеzbеdе bоlје dinаmičkе pеrfоrmаnsе оd оnih kоd еkvivаlеntnоg vеktоrski uprаvlјаnоg pоgоnа, а uz pојеdnоstаvlјеnjе uprаvlјаčkе strukturе i njеnu јеdnоstаvniјu implеmеntаciјu u mikrоprоcеsоrski sistеm. U tu svrhu su prvо dаtа tеоriјskа rаzmаtrаnjа dirеktnе kоntrоlе mоmеntа kоd аsinhrоnоg mоtоrа i prikаz rаzličitih pristupа zа rеаlizаciјu оvе uprаvlјаčkе strukturе. Nаkоn tоgа аnаlizirаnа је primеnа dirеktnе kоntrоlе mоmеntа kоd аsinhrоnоg pоgоnа sа struјnim prеtvаrаčеm učеstаnоsti pоmоću аdеkvаtnоg mаtеmаtičkоg mоdеlа pоgоnа. Pri tоmе је tеžištе stаvlјеnо nа spеcifičnоst tоpоlоgiје struјnоg prеtvаrаčа i nаčin nа kојi sе vrši trаnsfеr struје iz јеdnоsmеrnоg mеđukоlа u mоtоr. Rеzultаti istrаživаnjа su iskоrišćеni zа izrаdu uprаvlјаčkе strаtеgiје kоја pоrеd brzоg оdzivа mоmеntа kао kоd vеktоrskе kоntrоlе оbеzbеđuје јеdnоstаvniјi аlgоritаm uprаvlјаnjа bеz upоtrеbе оbrtnе trаnsfоrmаciје i zаhtеvа zа upоtrеbоm sеnzоrа brzinе nа vrаtilu mоtоrа. Zа rаzliku оd rеšеnjа dirеktnе kоntrоlе mоmеntа sа аsinhrоnim mоtоrоm nаpајаnim iz struјnоg invеrtоrа prеdlоžеnih u litеrаturi, dаtih bеz еkspеrimеntаlnе vеrifikаciје, аlgоritаm izlоžеn u disеrtаciјi је zаsnоvаn nа rаdu invеrtоrа sа kоnstаntnоm učеstаnоšću uz mоdifikаciјu оptimаlnе tаblicе аktivirаnjа prеkidаčа u invеrtоru. Оvim su izbеgnuti prоblеmi pri uprаvlјаnju dirеktnоm kоntrоlоm mоmеntа kоrišćеnjеm histеrеzisnоg rеgulаtоrа mоmеntа (znаčајnе pulsаciје mоmеntа, nеоphоdnоst filtrirаnjа еstimirаnоg signаlа mоmеntа, pоtrеbа аdаptаciје širinе histеrеzisа u zаvisnоsti оd brzinе mоtоrа). Аnаlizа pеrfоrmаnsi prеdlоžеnе strаtеgiје uprаvlјаnjа је izvršеnа simulаciјоm nа rаčunаru, а zаtim sе pristupilо rаzvојu uprаvlјаčkоg аlgоritmа u prоgrаmskоm јеziku C. Uprаvlјаčki аlgоritаm је implеmеntirаn i tеstirаn pоmоću mikrоprоcеsоrskоg sistеmа u оkviru rеаlizоvаnоg lаbоrаtоriјskоg prоtоtipа pоgоnа sа klаsičnim tiristоrskim prеtvаrаčеm učеstаnоsti. Svi pоstignuti rеzultаti, kаkо simulаciјоm tаkо i еkspеrimеntоm, pоtvrdili su isprаvnоst prеdlоžеnе uprаvlјаčkе strаtеgiје.The new control strategy based on direct torque control of CSI fed induction motor is presented. The goal of this work is to obtain better performances than exist in similar vector controlled drive, but with reduced control structure and its simpler implementation in the microprocessor system. For that purpose the theory of direct torque control (DTC) is given and different DTC-based strategies are described. Than, the analysis of DTC strategy in CSI fed induction motor drive is performed with adequate mathematical model. The aim of analysis were specific current converter topology and the way of current transfer from DC link to motor. Obtained results are used for developing such a control strategy that, besides a fast torque response as in vector control of the same drive, provide simpler control algorithm without necessity for coordinate transformation and speed sensor on the motor shaft. Contrary to the direct torque control of CSI drive presented in the known literature without experimental results, algorithm suggested in dissertation is based on constant-switching-frequency with modification of the inverter optimal switching table. With such a solution, problems detected under DTC using torque hysteresis controller are avoided (significant torque pulsations, requirement for filtering estimated torque and adaptation of hysteresis bandwidth in depend of motor speed). Performance analysis of recommended control strategy is completed on PC conmputer and than, the control algorithm is developed as software written in C programming language. Control algorithm is implemented and tested in the microprocessor system. This system is a part of the realized drive prototype with a standard thyristor type frequency converter. All results that are obtained by simulation and by experiment confirm the exactness of the proposed control strategy

Evolução dos parâmetros de motores de indução trifásicos e sua influência em estratégias de controlo

Tese de mestrado. Automação, Instrumentação e Controlo. Faculdade de Engenharia. Universidade do Porto. 200

Current derivative estimation for sensorless motor drives

The work presented in this thesis aims to improve the performance of the Fundamental PWM sensorless control technique by proposing a new way to estimate current derivatives in the presence of high frequency oscillations. The Fundamental PWM technique offers performance across the entire speed range (including zero speed). The method requires current derivative measurements when certain PWM (Pulse Width Modulation) active and null vectors are applied to the machine. However the switching action of the active devices in the inverter and the associated large dv/dt result in current and current derivative waveforms being affected by high frequency oscillations which prevent accurate measurement of the current derivative. Other approaches have allowed these oscillations to decay before attempting to take a derivative measurement. This requires that the PWM vectors are applied to the machine for a time sufficient to allow the oscillations to decay and a derivative measurement to be made (the minimum pulse width). On some occasions this time is longer than the time a vector would have normally been applied for (for example when operating at low speed) and the vectors must be extended and later compensated. Vector extension introduces undesirable current distortion, audible noise, torque ripple and vibration. In this thesis the high frequency oscillations and their sources are investigated and a method of using Artificial Neural Networks to estimate current derivatives using only a short window of the transient current response is proposed. The method is able to estimate the derivative directly from phase current measurements affected by high frequency oscillations and thus allows a reduction in the minimum pulse width to be achieved (since it is no longer necessary to wait for the oscillations to fully decay) without the need for dedicated current derivative sensors. The performance of the technique is validated with experimental results

Current derivative estimation for sensorless motor drives

The work presented in this thesis aims to improve the performance of the Fundamental PWM sensorless control technique by proposing a new way to estimate current derivatives in the presence of high frequency oscillations. The Fundamental PWM technique offers performance across the entire speed range (including zero speed). The method requires current derivative measurements when certain PWM (Pulse Width Modulation) active and null vectors are applied to the machine. However the switching action of the active devices in the inverter and the associated large dv/dt result in current and current derivative waveforms being affected by high frequency oscillations which prevent accurate measurement of the current derivative. Other approaches have allowed these oscillations to decay before attempting to take a derivative measurement. This requires that the PWM vectors are applied to the machine for a time sufficient to allow the oscillations to decay and a derivative measurement to be made (the minimum pulse width). On some occasions this time is longer than the time a vector would have normally been applied for (for example when operating at low speed) and the vectors must be extended and later compensated. Vector extension introduces undesirable current distortion, audible noise, torque ripple and vibration. In this thesis the high frequency oscillations and their sources are investigated and a method of using Artificial Neural Networks to estimate current derivatives using only a short window of the transient current response is proposed. The method is able to estimate the derivative directly from phase current measurements affected by high frequency oscillations and thus allows a reduction in the minimum pulse width to be achieved (since it is no longer necessary to wait for the oscillations to fully decay) without the need for dedicated current derivative sensors. The performance of the technique is validated with experimental results

Investigations on Direct Torque and Flux Control of Speed Sensorless Induction Motor Drive

The Induction motors (IM) are used worldwide as the workhorse in most of the industrial applications due to their simplicity, high performance, robustness and capability of operating in hazardous as well as extreme environmental conditions. However, the speed control of IM is complex as compared to the DC motor due to the presence of coupling between torque and flux producing components. The speed of the IM can be controlled using scalar control and vector control techniques. The most commonly used technique for speed control of IM is scalar control method. In this method, only the magnitude and frequency of the stator voltage or current is regulated. This method is easy to implement, but suffers from the poor dynamic response. Therefore, the vector control or field oriented control (FOC) is used for IM drives to achieve improved dynamic performance. In this method, the IM is operated like a fully compensated and separately excited DC motor. However, it requires more coordinate transformations, current controllers and modulation schemes. In order to get quick dynamic performance, direct torque and flux controlled (DTFC) IM drive is used. The DTFC is achieved by direct and independent control of flux linkages and electromagnetic torque through the selection of optimal inverter switching which gives fast torque and flux response without the use of current controllers, more coordinate transformations and modulation schemes. Many industries have marked various forms of IM drives using DTFC since 1980. The linear fixed-gain proportional-integral (PI) based speed controller is used in DTFC of an IM drive (IMD) under various operating modes. However, The PI controller (PIC) requires proper and accurate gain values to get high performance. The PIC gain values are tuned for a specific operating point and which may not be able to perform satisfactorily when the load torque and operating point changes. Therefore, the PIC is replaced by Type-1 fuzzy logic controller (T1FLC) to improve the dynamic performance over a wide speed range and also load torque disturbance rejections. The T1FLC is simple, easy to implement and effectively deals with the nonlinear control system without requiring complex mathematical equations using simple logical rules, which are decided by the expert. In order to further improve the controller performance, the T1FLC is replaced by Type-2 fuzzy logic controller (T2FLC). The T2FLC effectively handles the large footprint of uncertainties compared to the T1FLC due to the availability of three-dimensional control with type-reduction technique (i.e. Type-2 fuzzy sets and Type-2 reducer set) in the defuzzification process, whereas the T1FLC consists only a Type-1 fuzzy sets and single membership function. The training data for T1FLC and T2FLC is selected based on the PIC scheme

A synchronised multi-motor control system using hybrid sensorless induction motor drives

The main aim of this project was to research, develop and test an induction motor drive not requiring a speed encoder, but which could be considered commercially viable by motor drives manufacturers, and which should aim to meet the follow requirements: • Dynamic torque performance and steady state speed-holding accuracy to be comparable with encodered vector controlled drives • Extensive and highly accurate knowledge of electrical and mechanical parameters of the motor and load not to be required • Extensive commissioning from an expert engineer not to be necessary • Algorithm not to rely on excessive computational capability being available The drive was to operate, in a stable manner, over speed and load ranges at least comparable with commercially available sensorless induction motor drives. The above requirements were set such that the developed sensorless technique may be considered for synchronised multi-motor process applications, where the advantages of a sensorless system could be exploited for hazardous, damp and hot conditions. The solution developed consists of a leading model-based sensorless method augmented with a speed estimator that tracks harmonics, seen in the stator terminal quantities, due to rotor slotting. The model-based scheme facilitates field-orientated control for dynamic performance. The slot harmonic speed estimator tunes the model for speed accuracy. Slot harmonics are identified using a recursive signal processing method termed the Recursive Maximum Likelihood - Adaptive Tracking Filter. This work is the first example of the method being developed into a practical sensorless drive system and the complete speed identifier is described, including set-up, pre-filtering and the minimal parameter considerations. Being recursive the method is computationally efficient, yet has accuracy comparable with that of FFT identifiers used in other work. The developed sensorless strategy was implemented practically on two motor drive systems. The performance of the scheme is shown to give encoder like speed holding accuracy and field-orientated dynamic performance. The two drives were also configured and tested as a speed synchronised pair, using applicable multi-motor control techniques, themselves compared and contrasted. The sensorless performance is demonstrated, alongside an encodered version acting as a benchmark, and the performance of the two schemes is shown to be highly comparable. The author has found no other example of sensorless techniques considered for use in multi-motor applications. The use of such a technique brings established advantages associated with encoder removal and allows multi-axis electronic synchronisation to be considered for parts of a process where an encoder may not be appropriate

A synchronised multi-motor control system using hybrid sensorless induction motor drives

The main aim of this project was to research, develop and test an induction motor drive not requiring a speed encoder, but which could be considered commercially viable by motor drives manufacturers, and which should aim to meet the follow requirements: • Dynamic torque performance and steady state speed-holding accuracy to be comparable with encodered vector controlled drives • Extensive and highly accurate knowledge of electrical and mechanical parameters of the motor and load not to be required • Extensive commissioning from an expert engineer not to be necessary • Algorithm not to rely on excessive computational capability being available The drive was to operate, in a stable manner, over speed and load ranges at least comparable with commercially available sensorless induction motor drives. The above requirements were set such that the developed sensorless technique may be considered for synchronised multi-motor process applications, where the advantages of a sensorless system could be exploited for hazardous, damp and hot conditions. The solution developed consists of a leading model-based sensorless method augmented with a speed estimator that tracks harmonics, seen in the stator terminal quantities, due to rotor slotting. The model-based scheme facilitates field-orientated control for dynamic performance. The slot harmonic speed estimator tunes the model for speed accuracy. Slot harmonics are identified using a recursive signal processing method termed the Recursive Maximum Likelihood - Adaptive Tracking Filter. This work is the first example of the method being developed into a practical sensorless drive system and the complete speed identifier is described, including set-up, pre-filtering and the minimal parameter considerations. Being recursive the method is computationally efficient, yet has accuracy comparable with that of FFT identifiers used in other work. The developed sensorless strategy was implemented practically on two motor drive systems. The performance of the scheme is shown to give encoder like speed holding accuracy and field-orientated dynamic performance. The two drives were also configured and tested as a speed synchronised pair, using applicable multi-motor control techniques, themselves compared and contrasted. The sensorless performance is demonstrated, alongside an encodered version acting as a benchmark, and the performance of the two schemes is shown to be highly comparable. The author has found no other example of sensorless techniques considered for use in multi-motor applications. The use of such a technique brings established advantages associated with encoder removal and allows multi-axis electronic synchronisation to be considered for parts of a process where an encoder may not be appropriate