基于FPGA的直接转矩模糊控制技术研究

直接转矩控制技术是一种具有高静、动态性能的交流调速方法。本文以FPGA芯片为控制核心设计了感应电机直接转矩控制系统,用VHDL语言编写了系统的模糊控制软件.对软件中3/2变换模块、磁链和转矩估算模块、M/T测速模块、PI模块、模糊控制与启动模块、PWM模块进行详细的研究。然后通过实验初步验证了本文设计的基于模糊控制技术的感应电机直接转矩控制系统具有优良的动态和稳态性。     

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     

Variable flux control of permanent magnet synchronous motor drivesfor constant torque operation

In this paper, a small signal model of permanent magnet synchronous machines is developed which includes both components of torque, i.e., magnet torque and reluctance torque. The effects of flux variations on the torque are analyzed by the use of the developed model. The off-line torque compensation method proposed for induction machines is then adapted to permanent magnet motor drives to achieve a constant torque, variable flux operation of the drives. A sensitivity analysis is performed to show that the off-line method is influenced considerably by machine parameter variations. Therefore the concept of forced compensation is introduced and an on-line torque compensation controller is proposed. Simulation results are presented to show the effectiveness of the proposed controller. An experimental vector controlled permanent magnet motor drive including the on-line torque compensation controller is implemented based on a TMS320C31 DSP to evaluate the method. The experimental results also confirm a desirable variable flux control of the motor drive under constant torque operation     

Monitoring of induction motor load by neural network techniques

This paper deals with the electric tracing of the load variation of an induction machine supplied by the mains. A load problem, like a torque dip, affects the machine supply current and consequently it should be possible to use the current pattern to detect features of the torque pattern, using the machine itself as a torque sensor. But current signature depends on many phenomena and misunderstandings are possible. At first the effect of different load anomalies on current spectrum, in comparison with other machine problems like rotor asymmetries, are investigated. Reference is made to low frequency torque disturbances, which cause a quasistationary machine behavior. Simplified relationships, validated by simulation results and by experimental results, are developed to address the current spectrum features. In order to detect on-line anomalies, a current signature extraction is performed by the time-frequency spectrum approach. This method allows the detection of random faults as well. Finally it is shown that a neural network approach can help the torque pattern recognition, improving the interpretation of machine anomalies effects     

A new stator resistance tuning method for stator-flux-orientedvector-controlled induction motor drive

Field-oriented-controlled induction motor drives have been widely used over the last several years. Conventional direct stator-flux-oriented control schemes have the disadvantage of poor performance in the low-speed operating area when the stator flux is calculated using the voltage model, due to the stator resistance uncertainties and variations. In this paper, a new closed-loop stator-flux estimation method for a stator-flux-oriented vector-controlled induction motor drive is presented in which the stator resistance value is updated during operation. This method is based on a simple algorithm capable of running in a low-cost microcontroller, which is derived from the dynamic model of the induction machine. The effects of stator resistance detuning, especially in the low-speed operating region, are investigated and simulation results are shown. The motor drive system as well as the control logic and the resistance estimator are simulated and characteristic simulation results are derived. In addition, the proposed control scheme is experimentally implemented and some characteristic experimental results are shown. The simulation as well as the experimental results reveal that the proposed method is able to obtain precise flux and torque control, even for very low operating frequencies     

Fuzzy-logic-based torque control strategy for parallel-type hybridelectric vehicle

In a parallel-type hybrid electric vehicle (HEV), torque assisting and battery recharging control using the electric machine is the key point for efficient driving. In this paper, by adopting the decision-making property of fuzzy logic, the driving map for an HEV is made according to driving conditions. In this fuzzy logic controller, the induction machine torque command is generated from the acceleration pedal stroke and its rotational speed. To construct a proper rule base of fuzzy logic, the dynamo test and road tests for a hybrid powertrain are carried out, where the torque and the nitrogen oxides (NO_x) emission characteristic of the diesel engine and the driver's driving patterns are acquired, respectively. An HEV, a city bus for shuttle service, with the proposed fuzzy-logic-based driving strategy was built and tested at a real service route. It reveals that the improved NO_x emission and better charge balance without an extra battery charger over the conventional deterministic-table-based strategy     

Direct self control with minimum torque ripple and high dynamics for a double three-level GTO inverter drive

A highly dynamic control scheme with very low torque ripple-direct self control (DSC) with torque hysteresis control-for very high-power medium-voltage induction motor drives fed by a double three-level inverter (D3LI) is presented. In this arrangement, two three-level inverters that are connected in parallel at their DC sides are feeding the open motor windings. The DSC, well known from two- and three-level inverters, is adapted to the D3LI and optimized for a minimum torque ripple. An 18-corner trajectory is chosen for the stator flux of the induction machine since it is approaching the ideal circle much better than the hexagon known from DSC for two-level inverters, without any detriment to the torque ripple. The machine and inverter control are explained and the proposed torque quality and dynamics are verified by measurements on a 180-kW laboratory drive.     

A Direct-Flux-Vector-Controlled Induction Generator With Space-Vector Modulation for Integrated Starter Alternator

A direct-flux-vector-controlled scheme of induction generator has been proposed in this paper for future 42-V automobile application. The fundamental relationship between the rotating speed of the stator flux vector and torque is analyzed. A simple structure with only one proportional-integral (PI) controller is shown to implement the torque and flux controls adequately. By controlling the electromagnetic torque of the induction machine, the required dc-bus voltage can be well regulated within the 42-V PowerNet specifications. Fixed switching frequency and low torque ripple are obtained with space-vector modulation technique. Simulation and experimental results indicate that the proposed scheme provides a practical solution for an integrated starter alternator other than the widely applied field-oriented- control scheme.     

Estimation of induction machine inverse rotor time constant using torque angle tangent calculation

A new inverse rotor time constant estimation scheme for an induction machine is presented. For high performance induction machine control, indirect rotor flux oriented vector control is the most commonly applied control technique. It requires that an accurate estimate of the inverse rotor time constant is obtained to ensure correct orientation of the current vector with the rotor flux vector. An incorrect estimate will result in an incorrect flux level, reduced dynamic torque performance and reduced maximum available torque. A novel parameter estimation scheme is presented, based on the calculation of the tangent of the torque angle. The effectiveness of the technique is demonstrated through simulation and practical results.     

Fuzzy logic based on-line efficiency optimization control of anindirect vector-controlled induction motor drive

Improvement of adjustable speed drive system efficiency is important not only from the viewpoints of energy saving and cooling system operation, but also from the broad perspective of environmental pollution. The paper describes a fuzzy logic based on-line efficiency optimization control of a drive that uses an indirect vector controlled induction motor speed control system in the inner loop. At steady-state light-load condition, a fuzzy controller adaptively decrements the excitation current on the basis of measured input power such that, for a given load torque and speed, the drive settles down to the minimum input power, i.e., operates at maximum efficiency. The low-frequency pulsating torque due to decrementation of rotor flux is compensated in a feedforward manner. If the load torque or speed command changes, the efficiency search algorithm is abandoned and the rated flux is established to get the best transient response. The drive system with the proposed efficiency optimization controller has been simulated with lossy models of the converter and machine, and its performance has been thoroughly investigated. An experimental drive system with the proposed controller implemented on a TMS320C25 digital signal processor, has been tested in the laboratory to validate the theoretical development     

Identification and compensation of torque ripple in high-precisionpermanent magnet motor drives

Permanent magnet synchronous machines generate parasitic torque pulsations owing to distortion of the stator flux linkage distribution, variable magnetic reluctance at the stator slots, and secondary phenomena. The consequences are speed oscillations which, although small in magnitude, deteriorate the performance of the drive in demanding applications. The parasitic effects are analyzed and modeled using the complex state-variable approach. A fast current control system is employed to produce high-frequency electromagnetic torque components for compensation. A self-commissioning scheme is described which identifies the machine parameters, particularly the torque ripple functions which depend on the angular position of the rotor. Variations of permanent magnet flux density with temperature are compensated by on-line adaptation. The algorithms for adaptation and control are implemented in a standard microcontroller system without additional hardware. The effectiveness of the adaptive torque ripple compensation is demonstrated by experiments     

On-line tuning of the rotor time constant for vector-controlledinduction motor in position control applications

The induction motor drive with an indirect field-oriented controller (IFO) exhibits excellent behavior in a low-speed region. Thus, the motor can be advantageously used as an actuator in positioning servomechanisms. The authors propose the adaptation scheme for the continuous on-line tuning of the parameter T*_r, suitable for the environment of a position servo. The outlined analytical considerations and experimental results are focused on operation conditions characterized by the zero speed and a light load of the drive. The proposed adaptation scheme is based on the measurement of the terminal voltages that are used as an auxiliary information; then the scheme is designed in such a way that stator resistance fluctuations and nonlinearities within the analog processing circuitry do not affect the estimated value of the rotor time constant. Experimental results show that the proposed scheme gives good results even in conditions at zero speed and dynamic loads that may be as low as 0.2 p.u     

DTC Drives for Wide Speed Range Applications Using a Robust Flux-Weakening Algorithm

A control scheme for robust flux-weakening operation of direct-torque-control induction motor drive is proposed. The basic idea is to adjust the flux reference on the basis of the torque error, thus determining a spontaneous flux weakening. To exploit the maximum torque capability, it is necessary to estimate the maximum torque that the induction machine is able to generate at any speed. Initially, a basic version of the algorithm, requiring a simple off-line parameter tuning, is presented. Then, the algorithm is improved and completed with the online estimation of the maximum torque, hence avoiding the initial tuning process. The main features of the proposed methods are a little dependence on machine parameters and a smooth transition into and out of the flux-weakening operation mode. Experimental tests demonstrate the effectiveness of the control schemes.     

Independent field-oriented control of two split-phase induction motors from a single six-phase inverter

Split-phase (six-phase) induction motor stator windings consist of two sets of three phase windings, which are spatially phase separated by 30 electrical degrees. Due to mutual cancellation of the air gap flux for all the 6n/spl plusmn/1 (n=1,3,5...) order harmonic voltages, called zero sequence components, large harmonic currents are generated in the stator phases. Only the 12n/spl plusmn/1 (n=0,1,2,3...)-order harmonic voltage components contribute toward the air gap flux and electromagnetic torque production in the machine. In this paper, a novel scheme is proposed where two six-phase induction motors are connected in series with proper phase sequence so that the zero sequence component voltages of one machine act as torque and flux producing components for the other. Thus, the two six-phase motors can be independently controlled from a single six-phase inverter. A vector control scheme for the dual motor drive is developed and experimentally verified in this paper.     

Fuzzy logic enhanced speed control of an indirect field-orientedinduction machine drive

Field orientation control (FOC) of induction machines has permitted fast transient response by decoupled torque and flux control. However, field orientation detuning caused by parameter variations is a major difficulty for indirect FOC methods. Traditional probability density function (PID) controllers have trouble meeting a wide range of speed tracking performance even when proper field orientation is achieved. PID controller performance is severely degraded when detuning occurs. This paper presents a fuzzy logic design approach that can meet the speed tracking requirements even when detuning occurs. Computer simulations and experimental results obtained via a general-purpose digital signal processor (DSP) system are presented     

Iron loss in rotor-flux-oriented induction machines:identification, assessment of detuning, and compensation

Iron loss, traditionally ignored in vector control schemes, has recently attracted more attention as a cause of detuned operation of rotor-flux-oriented induction machines. Appropriate mathematical tools, that enable evaluation of detuning due to iron loss, have become available, and these have been used so far only in assessment of detuning for rated speed operation in the constant flux region. The available studies are based on the measurement of iron losses with voltage supply of rated frequency. This paper attempts to provide a more detailed treatment of iron loss induced detuning in rotor-flux-oriented induction machines by presenting at first an experimental method of iron loss identification over the entire frequency (speed) range of interest. The experimental results enable calculation of the equivalent iron loss resistance that is subsequently used in evaluation of detuning. The regimes dealt with encompass motoring and braking operation in the base speed range and motoring in the field-weakening region up to the five times rated speed. It is shown that detuning in the base speed range will be the highest at rated speed operation and will exhibit opposite trends in motoring and braking regions. Detuning in the field-weakening region is found to be significantly in excess of the one at rated speed, provided that the machine operates at high speeds with relatively light loads. As compensation of iron loss seems to be necessary in this case, the concluding part of the paper presents a novel rotor flux estimator that utilizes experimentally identified equivalent iron loss resistance values and enables elimination of detuning that is otherwise present. The estimator is a modified version of the well-known scheme that operates on the basis of measurement of stator currents and rotor speed (position). Its ability to compensate for iron loss is verified by simulation     

Optimal flux selection of an induction machine for maximum torqueoperation in flux-weakening region

The optimal flux-searching algorithms of an induction machine have reached a stage of development permitting maximum torque operation over an entire flux-weakening region. In the high-speed region, however, the sensitivity to parameter errors of an induction machine still remains a problem. This paper presents an approach that ensures maximum torque operation maintaining robustness to parameter error in the flux-weakening region. To guarantee the performance in the high speed region, the machine leakage inductance is adapted on line, based on the injection of sinusoidal current. Also, the detuned effect on machine inductance is thoroughly analyzed to relate the sensitivity of parameters to the performance of the flux-weakening region. Experimental results demonstrate that the proposed adaptation scheme effectively selects the optimal flux level regardless of variation of leakage inductance     

Direct torque and frequency control of double-inverter-fed slip-ring induction motor drive

A novel sensorless scheme for direct torque and frequency control of a double-inverter-fed slip-ring induction motor is presented. The analysis of a double-inverter-fed induction motor is given to derive the proposed controller. Various frequency profiles are analyzed for a direct frequency controller. A novel frequency profile is suggested to make the sensorless drive operation reliable and machine parameter independent at any rotor speed. Simulation and experimental results are presented from a 50-hp drive, demonstrating that the drive can deliver full torque from 0 to 2-p.u. speed in either direction. Thus, double the rated power can be extracted from the motor without overloading it.     

Dual-Plane Vector Control of a Five-Phase Induction Machine for an Improved Flux Pattern

A technique to improve the flux pattern within a five-phase induction machine is presented. The technique is developed through dual-plane vector control, with synchronized fluxes. By vector space decomposition, an analytical model and vector control of the machine are accomplished in two orthogonal vector planes,d₁-q₁ and d_s-q_s . The magnitude and rotating speed of the associated fluxes (fundamental and third harmonic) can be independently controlled in each vector plane. Synchronization control locks the relative position between the two fluxes. The resultant air-gap flux density is fully controlled, preventing iron saturation. This feature is especially important in reshaping the flux and back EMF waveform of the machine. A quasi-trapezoidal air-gap flux density distribution is achieved for better iron utilization and higher torque density. It is confirmed that compared with sinusoidal fluxing, the quasi-trapezoidal flux pattern will not lead to an oversized power inverter when improving machine torque density. The basic understanding and control scheme can be extended to a multiphase induction machine with a phase number greater than five.     

基于碳化硅功率器件的高频感应焊机设计探索构架

文中基于碳化硅功率器件应用的优势展开分析,讨论了碳化硅功率器件的高频感应焊机设计要点,包括逆变器原理分析、功率单元设计、电源控制系统设计、驱动及减速装置设计、模糊 PID 控制设计等,同时借助实验的方式验证了高频感应焊机设计方案的可行性,积累了相应的设计经验,以期为高频感应焊机的后续开发与设计提供参考。