Loss minimization in vector-controlled interior permanent-magnet synchronous motor drives

An efficiency optimization method for vector-controlled interior permanent-magnet synchronous motor drives is presented. Based on theoretical analysis, a loss minimization condition that determines the optimal d-axis component of the armature current is derived. Selected experimental results are presented to validate the effectiveness of the proposed control method.     

Loss minimization in DC drives

A method for determining the optimal DC machine excitation for loss minimization is presented. The proposed method may be implemented by using either analog or digital techniques. The method is simple, and its implementation does not affect significantly the cost, the complexity, and the dynamics of the DC drive. Thus, energy can be saved without sacrificing the quality of the DC drive. Even though the conception of the proposed method is based on the loss model of the DC machine, it is shown that its realization does not require knowledge of the loss model     

Loss minimization in wound-field cylindrical rotor synchronousmotor drives

The loss minimization problem in wound-field cylindrical rotor synchronous motor drives (SMDs) is investigated. From the theoretical analysis, a system of two loss model controllers (LMCs), for determining the optimal air-gap flux and optimal excitation current that minimizes the losses, results. The suggested LMCs are simple, and their implementation does not affect significantly the cost and complexity of the drive. Although the conception of the suggested LMCs is based on the loss model of the synchronous motor, it is shown that their implementation does not require knowledge of the loss model. All the theoretical results are verified experimentally     

Decoupling control of induction motor drives

The decoupling control of induction machines is investigated. Three different schemes for decoupling-control methods based on stator flux, airgap flux, and rotor flux field regulation are developed. The control dynamics of each scheme are outlined and studied. Simulation results are presented to verify that these schemes provide decoupling control with excellent dynamic behavior. The transient and steady-state relationships between slip frequency and torque, under constant stator flux, airgap flux, and rotor flux operations, are simulated and compared. The sensitivity characteristics of the three methods of flux-control, machine fed by impressed currents and voltages, are also compared and studied. A prototype torque-drive system is implemented to demonstrate the decoupling control of a squirrel-cage induction machine     

Theoretical and experimental analysis for the RMS current ripple minimization in induction motor drives controlled by SVM technique

In this paper, an analytical approach useful for predicting the current ripple in induction motor drives controlled by space-vector modulation (SVM) technique is presented. The analysis is applied to determine the optimal modulation technique that minimizes the rms value of the current ripple. The minimization procedure is based on the analysis of the locus described by the current ripple in the /spl alpha/--/spl beta/ reference frame. As a result, a simple equation has been obtained, which allows the online calculation of the optimal SVM switching pattern. It has been verified that it is possible to obtain a current ripple lower than that of symmetric modulation, and with a reduced number of commutations. Experimental results are provided to confirm the theoretical approach.     

Torque ripple minimization in switched reluctance motor drives byPWM current control

Higher torque ripple is one of the few drawbacks of switched reluctance motor (SRM) drives which otherwise possess excellent characteristics for applications in many commercial drives. This paper begins with an extensive review of torque ripple reduction methods that appear in the literature and then presents a new strategy of PWM current control for smooth operation of the drive. This method includes a current control strategy during commutation when torque ripple minimization is of utmost importance     

Adaptive decoupling control of induction motor drives

A novel control approach for a robust induction motor drive system with a voltage source inverter has been developed. In the scheme, the induction motor and its corresponding inverter gating signal are controlled using the decoupling control theory. In addition, an adaptive optimal speed regulator employing the model reference adaptive control (MRAC) is incorporated into the drive system to compensate for unfavorable errors. The principles and special features of the control scheme are discussed, and the configuration of the drive system is presented. Comparison is made between conventional proportional plus integral (PI) control and the MRAC. Test results show the robustness and superior dynamic performance of the proposed control system     

Fuzzy adaptive vector control of induction motor drives

This paper deals with the design and experimental realization of a model reference adaptive control (MRAC) system for the speed control of indirect field-oriented (IFO) induction motor drives based on using fuzzy laws for the adaptive process and a neuro-fuzzy procedure to optimize the fuzzy rules. Variation of the rotor time constant is also accounted for by performing a fuzzy fusion of three simple compensation strategies. A performance comparison between the new controller and a conventional MRAC control scheme is carried out by extensive simulations confirming the superiority of the proposed fuzzy adaptive regulator. A prototype based on an induction motor drive has been assembled and used to practically verify the features of the proposed control strategy     

A robust speed controller for induction motor drives

A speed controller considering the effects of parameter variations and external disturbance for indirect field-oriented induction motor drives is proposed in this paper. First a microprocessor-based indirect field-oriented induction motor drive is implemented and its dynamic model at nominal case is estimated. Based on the estimated model, an integral plus proportional (IP) controller is quantitatively designed to match the prescribed speed tracking specifications. Then a dead-time compensator and a simple robust controller are designed and augmented to reduce the effects of parameter variations and external disturbances. The desired speed tracking control performance of the drive can be preserved under wide operating range, and good speed load regulating performance can also be obtained. Theoretic basis and implementation of the proposed controller are detailedly described. Some simulated and experimental results are provided to demonstrate the effectiveness of the proposed controller     

Five-phase induction motor drives with DSP-based control system

This paper introduces two kinds of control schemes: vector control and direct torque control (DTC). These control schemes can be extensively applied to the operation of a five-phase induction motor using a fully digital implementation. Vector control of the five-phase induction motor not only achieves high drive performance, but also generates the desired nearly rectangular current waveforms and flux profile in the air-gap resulting in an improvement in air gap flux density and an increase of 10% in output torque. The DTC method has additional advantages when applied to multiphase, in this case a five-phase, induction motor. The five-phase inverter provides 32 space voltage vectors in comparison to 8 space voltage vectors provided by the three-phase inverter. Therefore, a more elaborate flux and torque control algorithm for the five-phase induction motor can be employed. Direct torque control of the five-phase induction motor reduces the amplitude of the ripples of both the stator flux and the torque, resulting in a more precise flux and torque control. A 32-b floating-point TMS320C32 digital signal processor (DSP) enables these two sophisticated control techniques to be conveniently implemented with high control precision. Experimental results show that an ideal control capability is obtained for both control methods when applied to the five-phase induction motor and further validates theoretical analysis     

Overmodulation and loss considerations in high-frequency modulatedtransistorized induction motor drives

A model for calculating additional induction-motor losses due to harmonics associated with PWM (pulse-width-modulated) voltage-source inverters is presented. A simple and low-cost measurement using small inverter to calculate the coefficients to be used in this loss model is presented for any size of induction motor. Based on measurements of motor losses from 300 Hz to 10 KHz, the proposed model assumes much higher losses at higher voltage harmonics than the conventional models. It is shown that sine-wave modulation at ~3.6 kHz modulation frequency results in higher losses than the six-step operation, while there is a loss minimum at overmodulation. It is concluded that the proposed model will be useful for the evaluation of various modulation schemes for high-frequency transistor inverters     

An innovative direct self-control scheme for induction motor drives

The paper presents a new direct self-control (DSC) scheme for induction motor drives using the stator voltage third harmonic component in order to estimate the air-gap flux and the torque as well as to synchronize the supply voltage vector. Compared to previous DSC schemes the new one is independent from any motor parameter variation, specifically on stator resistance thus showing better performances at low speeds. The paper starts with a quick review on standard DSC main features pointing out the influence of stator resistance variations on the flux and torque control. The new DSC scheme is then introduced and evaluated by simulations and experimental tests on a 1.5 kW induction motor drive     

Current control for induction motor drives using random PWM

Current control in voltage-source inverters with random pulsewidth modulation (RPWM) is investigated. The random modulation is introduced to alleviate the undesirable acoustic, vibration, and EMI effects in inverter-fed AC drive systems. A novel RPWM digital technique with dithering of the switching frequency and compensation of the processing time is described. Design of the current control loop is discussed. Results of investigation of an experimental drive system are presented, proving the feasibility of the proposed solutions     

Adaptive speed control for induction motor drives using neuralnetworks

In this paper, the adaptive speed control of induction motor drives using neural networks is presented. To obtain good tracking and regulating control characteristics, a digital two-degree-of-freedom (2DOF) controller is adopted and a design procedure is developed for systematically finding its parameters according to prescribed specifications. The parameters of the controller corresponding to various drive parameter sets are found off-line and used as the training patterns to estimate the connection weights of neural networks, Under normal operation, the true drive parameters are real-time identified and they are converted into the controller parameters through multilayer forward computation by neural networks. The parameters of the 2DOF controller can be adapted to match the desired specifications under various operating conditions     

A fault-tolerant control architecture for induction motor drives in automotive applications

This paper describes a fault-tolerant control system for a high-performance induction motor drive that propels an electrical vehicle (EV) or hybrid electric vehicle (HEV). In the proposed control scheme, the developed system takes into account the controller transition smoothness in the event of sensor failure. Moreover, due to the EV or HEV requirements for sensorless operations, a practical sensorless control scheme is developed and used within the proposed fault-tolerant control system. This requires the presence of an adaptive flux observer. The speed estimator is based on the approximation of the magnetic characteristic slope of the induction motor to the mutual inductance value. Simulation results, in terms of speed and torque responses, show the effectiveness of the proposed approach.     

A deadbeat current controller for field oriented induction motor drives

Accurate stator current control is essential in high performance field orientation-controlled induction motor drives. Any current error degrades the drive's performance in the same way as an incorrectly tuned field orientation. This paper presents an efficient current control scheme that can achieve high accuracy and a fast dynamic response. This scheme uses voltage decoupling and deadbeat control loops. The decoupling controller provides the voltage needed to oppose the motor's back EMF. The deadbeat controller reduces the current error as fast as possible and stabilizes the system. The control law does not require knowledge of the rotor flux and is independent of the field orientation control tuning. Good static and dynamic performances were obtained in both the simulation and experimental verifications. Because the motor leakage inductance and resistance information were required for this control method, the influence of the estimation errors for these parameters was also investigated. The results show that the leakage inductance model error might cause a current ripple. However, this parameter can be tuned to its correct value easily by inspecting the current response.     

A pulse frequency modulated PWM inverter for induction motor drives

A PWM pulse pattern optimization method using pulse frequency modulation (PFM) is described. In conventional PWMs the pulse frequency is kept constant. In the proposed PFM, however, the pulse frequency is adjusted. The PFM technique is intended to not only reduce the magnetic acoustic noises of driven motors but also to improve the performance of sinusoidal inverters. The PWM pulse patterns are basically controlled so that the time-integral function of the voltage vectors in the space vector notation may draw a circular locus. In addition to this, the pulse frequency, of PWM is also controlled so that the performance index (PI), which represents the degree of achieved objectives, may be minimized. Two PIs, one for minimizing the distortion of output currents and the other for minimizing the torque pulsation of driven motors, are employed. The method is implemented using a single-chip microprocessor, and the experimental results demonstrate its validity     

A digital current control technique for voltage-fed induction motor drives

Precise control of stator current is essential to high performance field orientation controlled induction motor drives. Any current error degrades the performance of the drive in the same way as incorrect tuning of field orientation. Previous research has shown that accurate current control can be achieved with intelligent but complex control algorithms. This paper presents a new current control scheme which can achieve high accuracy and fast dynamic response but which is very simple for microprocessor implementation. The scheme was derived using the discrete state space modelling of the induction motor. The control law does not require knowledge of rotor flux and was independent of the field orientation control tuning. Good static and dynamic performances were obtained in both the simulation and experimental verifications. The results also show that the leakage inductance model error might cause a current ripple. However, this parameter can be tuned to its correct value easily by inspecting the current response.