Combined vector control and direct torque control method for high performance induction motor drives

A new control method is proposed for three phase high performance induction motor drives. The control system enjoys the advantages of vector control and direct torque control and avoids some of the implementation difficulties of either of the two control methods. In particular, the proposed control system includes a current vector control in connection with a switching table. An extensive comparative performance evaluation of a motor under the proposed control method confirms the effectiveness of the method and its partial superiority over either vector control or direct torque control despite its relative structural simplicity.     

Passivity-based sliding mode position control for induction motor drives

In this paper, a passivity-based sliding-mode controller is proposed to control the motion of an induction motor. At first, the induction motor is proved to be a state strictly passive system. Then, a sliding-mode position controller with an adaptive load torque estimator is designed to control the position of the induction motor such that the chattering effects associated with a classical sliding-mode position controller can be eliminated. The stability analysis of the overall position control system is carried out by the passivity theory. The proposed approach is robust with regard to variations of motor mechanical parameters and load torque disturbances. Finally, experimental results are included to demonstrate that good position tracking can be obtained without the rotor flux observer.     

Online identification of the mutual inductance for vector controlled induction motor drives

Mutual inductance of an induction machine may vary considerably when the flux reference varies. An important and frequent application of a variable flux reference is the operation in the field-weakening region. Standard assumption of constant mutual inductance is no longer valid and it becomes necessary to compensate for the mutual inductance variation. The paper proposes a novel method for online mutual inductance identification in vector controlled induction machines. The method is characterized with very simple structure, ease of implementation, very low parameter sensitivity, and capability to provide an accurate estimate under both transient and steady state operating conditions. Full experimental verification of the proposed scheme is provided and a number of potential applications in a vector controlled induction motor drive are discussed.     

Improved sensorless vector control for induction motor drives fed by a matrix converter using nonlinear modeling and disturbance observer

This paper presents a new sensorless vector control system for high performance induction motor drives fed by a matrix converter with nonlinearity compensation and disturbance observer. The nonlinear voltage distortion that is caused by commutation delay and on-state voltage drop in switching device is corrected by a new matrix converter modeling. The lumped disturbances such as parameter variation and load disturbance of the system are estimated by the radial basis function network (RBFN). An adaptive observer is also employed to bring better responses at the low speed operation. Experimental results are shown to illustrate the performance of the proposed system.     

A modified neural learning algorithm for online rotor resistance estimation in vector controlled induction motor drives

Online estimation of rotor resistance is essential for high performance vector controlled drives. In this paper, a novel modified neural algorithm has been identified for the online estimation of rotor resistance. Neural based estimators are now receiving active consideration as they have a number of advantages over conventional techniques. The training algorithm of the neural network determines its learning speed, stability, weight convergence, accuracy of estimation, speed of tracking and ease of implementation. In this paper, the neural estimator has been studied with conventional and proposed learning algorithms. The sensitivity of the rotor resistance change has been tested for a wide range of variation from -50% to+50% on the stability of the drive system with and without estimator. It is quiet appealing to settle with optimal estimation time and error for the viable realization. The study is conducted extensively for estimation and tracking. The proposed learning algorithm is found to exhibit good estimation and tracking capabilities. Besides, it reduces computational complexity and, hence, more feasible for practical digital implementation.     

Harmonic analysis of slip energy recovery induction motor drives

The impact of electric drives on the power system in terms of harmonic generation is becoming increasingly important. Slip energy recovery induction motor drives (SERIMDs) have the rectifier and inverter connected to the rotor instead of the stator (the case in most conventional drives). The harmonic content of the SERIMD is thus quite different and arguably, less onerous than conventional drives. This paper examines the harmonic content of key waveforms of SERIMDs. Predicted results are supported by extensive experimental results     

A space vector modulation algorithm for torque control of inverterfed induction motor drive

After a short review of the vectorial torque control (VTC) strategy, the design and setup of a dedicated modulation hardware unit is described in detail. Experimental comparisons with traditional induction motor control techniques fully confirm the validity of the proposed system     

Comparative study of various artificial intelligence approaches applied to direct torque control of induction motor drives

In this paper, three intelligent approaches were proposed, applied to direct torque control (DTC) of induction motor drive to replace conventional hysteresis comparators and selection table, namely fuzzy logic, artificial neural network and adaptive neuro-fuzzy inference system (ANFIS). The simulated results obtained demonstrate the feasibility of the adaptive network-based fuzzy inference system based direct torque control (ANFIS-DTC). Compared with the classical direct torque control, fuzzy logic based direct torque control (FL-DTC), and neural networks based direct torque control (NN-DTC), the proposed ANFIS-based scheme optimizes the electromagnetic torque and stator flux ripples, and incurs much shorter execution times and hence the errors caused by control time delays are minimized. The validity of the proposed methods is confirmed by simulation results.     

Cancellation of common-mode Voltages for induction motor drives using active method

This paper presents a theoretical analysis for canceling common-mode (CM) voltages for induction motor (IM) drives using a CM transformer with active circuitry. The design methodology and the practical implementation are presented for motor drives rated 460 V or higher. To verify the design approach, an implementation example and experimental results for a 460-V motor drive system are presented.     

Evaluation of stray load loss in induction motors with a comparison of input-output and calorimetric methods

This paper investigates the input-output and the calorimetric methods of evaluating stray load loss in induction motors. It highlights the difficulties of accurately measuring stray load loss experimentally and thereby declaring the correct machine efficiency. The standard experimental approach of input-output power measurement with loss segregation is widely used but has some limitations. Fifteen induction motors ranging between 11 kW (15 hp) and 200 hp have been carefully studied in this paper mainly using IEEE 112 Method B. Additional results obtained by calorimetric methods have been used to validate the standard test methods. The objectives of this paper are to quantify the stray load loss, to identify possible sources of error in such a process, and to provide indications of how some of these errors may be mitigated. The conclusion drawn confirms that the only valid way is to evaluate stray load loss directly and any arbitrary allowance for stray load loss is unfounded. The importance of this work is in improving measurement techniques and instrumentation accuracy.     

Pulse multiplication in AC-DC converters for harmonic mitigation in vector-controlled induction motor drives

In this paper, an autotransformer with reduced kilovoltampere rating for 24-pulse ac-dc converter fed vector controlled induction motor drives (VCIMDs) is presented for harmonic current reduction. The 24-pulse operation is achieved using dc ripple reinjection technique in 12-pulse ac-dc converters. The proposed novel harmonic mitigator is found capable of suppressing up to 21st harmonic in the supply current. The procedure for the design of autotransformer for proposed ac-dc converter is presented to show the flexibility in the design for making it a cost-effective replacement suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter. A set of power quality indices on input ac mains and on dc bus for a VCIMD fed from other 24-pulse ac-dc converters are also given to compare their performance. The laboratory prototypes of proposed autotransformers based 12-pulse and 24-pulse ac-dc converters are developed and test results are presented to validate the developed design procedure and the simulation models of these ac-dc converters under varying loads.     

A method for transient torque response improvement in optimum efficiency induction motor drives

Optimal efficiency control of induction motor drives implies operation at reduced flux levels with light loads. Two problems in light load operation are a large speed drop after sudden load torque increase and slow acceleration. In order to improve response in these transients, an algorithm for optimum dynamic distribution of the available maximum inverter current into the flux-producing and the torque-producing stator current components is developed in this paper. The proposed algorithm accounts for the main flux saturation effect in the machine and the dynamics of the flux variation. Its performance is illustrated by means of simulation and experimental results. Superiority of the developed algorithm over some of the existing methods is proved by comparing the speed drops, which result after sudden load torque increase during operation at light load, and by examining an acceleration transient under light load condition.     

一种新型抽油机电机电压空间矢量PWM控制技术研究

油田采油设备使用大量的游梁式抽油机,其电机一般均使用三相异步感应电机,由于目前较为成熟的抽油机电机节能控制常采用两电平PWM变频控制,其输出电压中除基波外,还包含有大量的谐波分量,造成电压波形的畸变,因而运行效率较低,浪费了大量的电能。文中介绍了采用电压空间矢量PWM控制技术来控制抽油机电机的方法,与传统的PWM方法相比,可以减小转矩脉动和铁损耗,并可提高电源电压的利用率,从而实现较好的节能效果。     

A computer program to predict the performance of slip energyrecovery induction motor drives

Details are provided, in the form of a flowchart, to permit the reconstruction of a computer program to predict the transient and steady-state performance of slip energy recovery induction motor (IM) drives. Slip energy recovery IM drives are different from most other drives in that the inverter is generally connected only after the machine has reached a predetermined speed. The initial conditions of the inverter are therefore nonzero and difficult to obtain. Three techniques that can be used to calculate the initial conditions are discussed. Theoretical predictions are supported by practical results     

Compensation of magnetic saturation in maximum torque to current vector controlled synchronous reluctance motor drives

This paper investigates the influence of magnetic saturation in maximum torque to current vector controlled synchronous reluctance motor drives. A theoretical analysis is presented where a maximum torque to current condition that takes into account and compensates the effect of magnetic saturation in the synchronous reluctance motor drive performance is derived. The proposed controller does not affect the dynamic performance of the drive and is easily implemented, since an experimental procedure is used to determine its parameter. Therefore, the knowledge of the exact motor model is not required. Several experimental results are presented to validate the effectiveness of the proposed controlled scheme.     

A new induction motor drive based on the flux vector acceleration method

A novel control strategy for the induction motor drive, based on the field acceleration method, is presented. The torque is controlled through variations of the stator flux angular velocity. The stator flux is controlled by using a feedforward control scheme, with the stator flux reference vector adjusted so as to obtain the fixed rotor flux amplitude. The applied controller assures a fast torque response, low torque ripple in the steady state, and drive operation with a constant switching frequency. The algorithm includes the improved stator and rotor flux estimation that guarantees the stable drive operation in all operating conditions, even at low speeds. The experimental tests verify the performance of the proposed algorithm, proving that good behavior of the drive is achieved in the transient and steady-state operating conditions.     

Hybrid fuzzy controller for speed control of switched reluctance motor drives

A hybrid fuzzy controller for speed control of switched reluctance motor (SRM) drives is presented in this paper. The developed hybrid fuzzy control law consists of a proportional integral (PI) controller at steady state, a PI type fuzzy logic controller (FLC) at transient state and a simple logic controller between the steady and transient states to achieve the desired performance at various operating conditions under soft chopping operation. The importance of the hybrid fuzzy controller is highlighted by comparing the performance of various control approaches, including PI control, PI type fuzzy logic control and PD type fuzzy control for speed control of SRM motor drives. The complete control algorithm is demonstrated by intensive experimental results. It is shown that the presented hybrid controller for SRM drive has fast tracking capability, less steady state error and is robust to load disturbance. The complete speed control scheme of the SRM drive incorporating the hybrid control is experimentally implemented and validated using a high speed digital signal processor board TMS320F2812 for a prototype 1.2 kW SRM.     

Performance optimization in switched reluctance motor drives with online commutation angle control

The problem of performance optimization in current controlled switched reluctance motor (SRM) drives is investigated. Two controllers are proposed that determine the optimal turn-on and turn-off angles, respectively, for improving motor efficiency and torque ripple. The suggested controllers are simple, do not affect the complexity of the drive, and are easily implemented since the knowledge of torque-angle-current characteristics or magnetization curves is not required. The proposed control scheme is demonstrated on a prototype experimental system.     

Long-shunt and short-shunt connections on dynamic performance of aSEIG feeding an induction motor load

This paper presents a comparative study of long-shunt and short-shunt configurations on dynamic performance of an isolated self-excited induction generator (SEIG) feeding an induction motor (IM) load. The studied IM is suddenly connected to the output terminals of the studied configurations of the SEIG. Both simulated results and experimental results based on laboratory 1.1 kW induction machines are clearly compared to examine the effects of both connections on voltage variation of the studied SEIG. The analyzed results show that the long-shunt configuration may lead to unwanted oscillations while the short-shunt connection provides better voltage variation. The eigenvalue technique is also employed to examine the possible voltage collapse and unstable conditions in the studied SEIG-IM system     

Direct field oriented control scheme for space vector modulated AC/DC/AC converter fed induction motor

This paper investigates a Luenberger flux observer with speed adaptation for a direct field oriented control of an induction motor. An improved method of speed estimation that operates on the principle of speed adaptive flux and current observer has been proposed. An observer is basically an estimator that uses a plant model and a feedback loop with measured stator voltage and current. Simulation results show that the proposed direct field oriented control with the proposed observer provides good performance dynamic characteristics. The induction motor is fed by an indirect power electronics converter. This indirect converter is controlled by a sliding mode technique that enables minimization of harmonics introduced by the line converter, as well as the control of the power factor and DC-link voltage. The robustness of the overall system is studied using simulation for different operating modes and varied parameters.