Field Weakening Mode Research Articles

Reference Input Signals Formation for Induction Motor Control in Traction Drive

The purpose of this work is to build the analytical improved (with resistances estimation) real time computation of the reference inputs for rotor flux and torque in the vector control system of an induction motor of a traction electric drive. The reference inputs must maximize electromagnetic torque in conditions of voltage source instability, particularly in magnetic field weakening mode. The conventional way to control the field weakening mode is to form flux coupling task inversely proportional to the speed or inversely proportional to the square of the speed in second and third zones respectively. Such reference input signals are not able to provide the maximum torque capability over the entire speed range, and the improved torque capability is achieved in different ways. For instance, voltage feedback is useful for the torque capability enhancement in conditions of internal and external perturbations. A wide change in speed with the weakening of the flux reveals the nonlinear properties of an induction electric motor. However, in vector control systems, proportional-integrating (PI) regulators are usually used. Therefore, firstly, linear PI controllers must be robust, and secondly, the reference input signals for flux and torque must guaranty linear, not saturated state of each PI controller. The proposed expressions for calculating reference inputs for induction motor rotor flux and electromagnetic torque as functions of actual rotor speed are the approximate expressions. The estimation of the possible error shows that the error is acceptable. Simulation is performed for the vector control system of an induction motor and taking into account the calculation of the control signal by the microcontroller and the dynamics of the frequency invertor. The simulation of the resulting system validates the effectiveness of the control system using the proposed expressions for the formation of real-time reference input signals for setting the flux and torque.

FEATURES OF THE FIELD WEAKENING MODE IN А SWITCHED RELUCTANCE MACHINE

The magnetic field weakening mode of electric machines is used in modern drives to extend the drive operational speed range when the power supply voltage is limited. In conventional electric drives, a real or fictitious flux control loop, established in a vector control system by using coordinate and phase transformations of corresponding variables, is used for attenuating the motor magnetic flux. Switched reluctance machines have certain design advantages over conventional electric machines; they feature high reliability and wide control possibilities. However, to realize these possibilities, appropriate control outputs should be generated, the choice of which depends on the operational speed range. Another peculiarity of these machines is that there is no separate magnetic flux stabilization or control circuit. The article considers the specific features pertinent to the switched reluctance machine operation in various speed ranges for adequately taking them into account in control algorithms. The studies were carried out using the electric drive simulation model in the MATLAB Simulink environment. It is shown that during the electric drive operation at its limit mechanical characteristic in the low-speed zone under the speed variation conditions, the phase flux linkage average value can be considered almost unchanged. However, control of the average torque carried out by changing the current limitation level is performed at the magnetic flux weakening background. It has been determined that during operation in a high-speed zone at invariable phase switching positions with the speed growing in a natural manner (i.e., without applying control actions), there is an excessive decrease in the flux linkage average value, which leads to a dramatic drop in the phase average torque. This drop can be compensated by progressively shifting the phase engagement position in the leading direction.

ВИЗНАЧЕННЯ КООРДИНАТ ТОЧОК ПЕРЕМИКАНЬ ОПТИМАЛЬНИХ СТРАТЕГІЙ КЕРУВАННЯ ЯВНОПОЛЮСНИМИ СИНХРОННИМИ ДВИГУНАМИ З ПОСТІЙНИМИ МАГНІТАМИ

In this paper, a detailed analysis of the control algorithms for a permanent magnet synchronous motor in a wide range of speeds is carried out using the optimal strategies: "Maximum torque per ampere" (first zone), "Field weakening mode" (second zone) and "Maximum torque per volt" (third zone). A method for determining the boundaries of the first and second zones, as well as a method for determining the maximum static moment with which the motor can operate without the risk of irreversible demagnetization of permanent magnets, was proposed. It allows determining the maximum possible operating speed of the motor at a given load, the maximum motor load at a given speed, as well as the advisability of using the third control zone to achieve the maximum motor speed. References 19, figures 4.

Series Motor Four Quadrants Drive DC Chopper Part3:Field Weakening mode

This paper describes the operation of a field weakening mode of a new four quadrants DC chopper (FQDC) that can be used to extend the speed of an Electric Car (EC). A mathematical model and real experiment are used to verify the effectiveness of the field weakening mode of the proposed FQDC. First, Matlab/Simulink is used to simulate the system under study and the results indicate that the proposed approach is effective. This is followed by a real experiment using a prototype electric vehicle driven by a DC series motor. The results of the experiment show that the proposed FQDC successfully performed the operation as intended.

Topology and control algorithms for a permanent magnet synchronous motor as a part of a vehicle with in-wheel motors

This article describes an electric drive system’s topology with a permanent magnet synchronous motor for a wide speed range applications. Topology consists of a synchronous motor with permanent magnets (PMSM) and two inverters connected to the beginnings and to the ends of the PMSM’s stator windings. The first inverter is connected to a storage battery, while the other one to a floating bridge capacitor, which acts as a back-EMF compensator. The article proposes electric drive system topolo-gy and its control algorithm. Simulation modeling was implemented by the MATLAB/Simulink software package. Simulation results shows that the proposed electric drive system, in comparison with the standard topology with a «star» stator windings connection, is able to increase the maximum speed of PMSM in the field weakening mode by 17%. The maximum achievable torque on the rotor shaft at the maximum speed of the PMSM motor was increased by 16.6%. Also, developed topology allows to in-crease the speed range in the constant torque mode by 34%.

Determination of the characteristic points of approximation for traction electric machines of electric rolling stock

The paper presents a new approach to the selection of characteristic points on the current-voltage curve (CVC) of the brush contact of traction electric machines, for their approximation in the form of three different functions, with characteristic points of transition to the field weakening mode. The problem of raising resources by using new design electro brushes. This constructive solution is consistent with the specific types of traction motors used in urban and rail transport and satisfies the technical conditions for their operation. A construction brush holders, which will save the cost of electro, in connection with their wear and tear due to friction on the walls of the brush holders. Improving the quality of machines saves material means and human resources, increase the profitability of their use, resulting in a significant increase in productivity. The method of calculating the current-voltage characteristics of a new type electro brushes, the distinguishing feature of which is the introduction of a cross section of the body brush. In the course of the experiment revealed steadily increasing rate of proposed electro brushes, compared with the standard of the same type EG61A. Data collected during the experiment showed that electro brushes with a transverse incision is more stable contact with the collector.

Control system of electric traction drive of electric vehicle

The growth rate of electric transport production is increasing every year, so the issues of its improvement and development are relevant. The developmentof a traction electric drive control system that would meet all the requirements, it is the aim of the article. There is a strong weakening of the field, providing a quick change in torque. The results of the created electric drive system are obtained with simulation in the MATLAB. The control system provides the engine in traction mode, recovery mode, reverse, and also allows you to develop high torque at low speeds. The result is a trapezoidal velocity diagram and an almost rectangular moment diagram. When operating at higher speeds up to 400 rad/s, the system works stably. At higher speeds, moment fluctuations appear and dynamics deteriorates. Fluctuations in flux linkage are observed at a speed of more than 700 rad/s. The modeling also showed that the system maintains a constant voltage in the field weakening mode. The development of the control system in order to increase the torque at low speeds is possible due to the introduction of the controller of the balances of the real current of the machine and the current calculated in the engine model. The introduction of a dynamic field attenuation circuit serves to provide high torque when it is not possible to further increase the voltage of the motor stator.

FIELD WEAKENING CONTROL FOR INDUCTION MOTORS BASED ON COPPER AND IRON LOSSES MINIMIZATION

This paper is concerned with the analysis of losses in induction motors. The most significant have been chose for minimization. These are in particular the losses in the windings and in the magnetic circuit due to eddy currents and hysteresis. Equations for the rotor flux linkage and orthogonal components of the stator current in the rotor reference frame dq in the induction motor’s vector control system based on the condition of minimizing the total losses in copper and motor steel in the steady state. Here, effects of steel saturation are not taken into account. The limit values of the torque and speed are determined, where the rotor flux linkage con-trol can improve the energy characteristics of the drive outside the magnetic saturation. It is shown that the main difficulty in imple-menting energy-optimal control is that the rotor flux linkage operates not only energy parameters, but also speed regulation in the field-weakening region.A block diagram of the implementation of energy-optimal control with field weakening mode is proposed. The idea is to switch the control algorithms of the magnetic field of the motor in such a way that in the start-brake modes the rotor flux linkage changes in the speed reference function, and when operating at a steady speed, in the function of the torque. A co mpara-tive analysis for a typical and developed drive systems in field-weakening mode by the simulation is carried out.It is shown that with the same transients of the torque and speed in a typical system, the efficiency in steady-state decreases with a decrease of torque load torque, whereas the proposed system it remains unchanged. The change in efficiency in dynamic conditions occurs when the rotor flux linkage changes. With energy-optimal control, there is a slight increase in the stator current peaks when the torque load changes abruptly, but at low torque load an additional field-weakening leads to a decrease in the stator voltage, which carry on a decrease in electricity consumption.

PMSM control system with open-end winding and floating bridge capacitor

This paper represents structure of permanent magnet synchronous motor (PMSM) control system focused to work in field weakening mode. Structurally it consists of PMSM motor with open end winding, main bridge inverter (MB) with DC voltage at one side of motor winding and floating bridge (FB) inverter with a capacitor at the other side of motor winding. Structure of control system with active and reactive power distribution for MB and FB inverter with capacitor’s voltage level control and motor’s shaft control loops is proposed. Simulation model via Matlab/Simulink and Simscape language is designed. Comparing proposed control system with field oriented PMSM vector control and “Y” motor end winding connection is provided. Obtained results shows that proposed control system helps to reach 1.4 times more maximum speed that a conventional one

Advanced Angle Field Weakening Control Strategy of Permanent Magnet Synchronous Motor

The conventional field weakening algorithm is more dependent on parameters and computational complexity. Therefore, the concept of advanced angle β is introduced, and the conversion of constant torque operation mode to field weakening operation mode is realized by increasing β . In this paper, the conventional field weakening control and advanced angle field weakening are modeled and simulated showing results that the advanced angle field weakening control can make the motor switch smoothly between the constant torque operation mode and the field weakening mode. The dependence of the parameters of the motor is small and the algorithm is simpler. At the same time, the theory of field weakening control of permanent magnet synchronous motor is fused in the vehicle control and the controller is developed. The external characteristic curve of the motor is calibrated by setting up the back-to-back motor test bench. The function of the controller is verified by hardware-in-the-loop experiment. After vehicle verification, it is confirmed that the data can normally enter the field weakening zone to meet the torque response and high-efficiency range. Under the new European driving cycle (NEDC) operating conditions, the efficiency of the whole controller can reach 81.97%.

STUDY WORK OF THE ASYNCHRONOUS MOTOR AD-906U IN FIELD WEAKENING MODE

The article analyzes research of the work asynchronous motor AD-906U in the field weakening mode with vector control system on mathematical model in MATLAB software environment. A quantitative estimation of the deviation of the power by an asynchronous motor is given for different methods of constructing the characteristic |ψR|=f(ωR). The rationale for choosing of the method for constructing a characteristic |ψR|=f(ωR) for an asynchronous motor AD-906U in the field weakening mode in the traction electric drive of a diesel train DEL-02

A Novel Magnetizing-Curve Identification and Computer Storage Technique for Induction Machines Suitable for Online Application

Field orientation control of an induction machine often requires variable flux operation in either energy optimization mode or field-weakening mode above base speed. One way to generate accurate <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis stator current reference at all operating points demands accurate knowledge about the magnetizing curve of the machine. This paper proposes a simple and accurate technique to identify the magnetizing curve, which assumes a synchronously rotating stator current axis as the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis. The proposed method can be implemented with the same hardware available for normal operation of the drive. The effect of parameter variation on the curve identification accuracy is also discussed. A “piecewise mixed model of approximation” is proposed to store the magnetizing curve in the processor memory for online application. The number of sections required by the proposed technique for accurate representation of the curve reduces drastically, compared to the widely used “piecewise linear model.” Different experiments performed on a practical machine validate the proposed concept.

Improvement in the field-weakening performance of switched reluctance machine with continuous mode

A new operation mode for switched reluctance motors (SRMs), called 'continuous mode', is described. By using this mode, the torque and then power in field-weakening mode can be considerably increased without any hardware modifications. Consequently, power and torque densities of SRMs become comparable to other technologies (synchronous and induction motors) and with a field weakening operation over a large speed range. This new degree of freedom makes it possible to improve the motor design, by modifying the rotor pole arc size or the windings turns per pole. Only simulation results are presented here, for a 12/8 SRM. Results confirm that the maximum power is improved (constant power on a very large speed range) and with a higher efficiency than that in the classical discontinuous mode.

Exact tracking by dynamic field-weakened PMAC servodrive

In the paper the exact tracking of permanent magnet AC servodrives with dynamic field-weakening is presented. The analytical solution given in the form of a reference dynamic model of the direct axis current and corresponding transition conditions is derived from the inverse motor dynamics. The presented solution guarantees the control voltage to remain within the constraint during steady states and transients, and also preserves exact tracking of the prescribed mechanical trajectories in the field weakening mode. The suggested method is independent of the implemented control structure. Analytical results have been confirmed by the experiments.

A start-up method for a speed sensorless stator-flux-oriented vector-controlled induction motor drive

This paper describes a zero-speed start-up method of a speed sensorless stator-flux-oriented direct vector-controlled induction motor drive with the help of a machine current model that does not use any speed signal. The machine starts smoothly with vector control at finite developed torque and then transitions to the standard direct vector-control mode with the voltage model signals as the speed begins to develop. The direct vector-control mode with voltage model uses programmable cascaded low-pass filters for flux-vector synthesis and enables the drive to operate from zero speed to field-weakening mode. As the drive speed falls to zero, the drive again transitions to start-up mode, so that it can be smoothly started again. The performance of the start-up scheme has been verified on a 100 kW electric vehicle drive.

Performance characteristics of brushless DC drives

A simulation model for the performance prediction of brushless DC drives is used to investigate the speed control obtained from modulation index and commutation advance variations for a motor of complex magnetic circuit geometry powered by a sine-coded PWM (pulsewidth modulation) inverter. The results of the study show the effects of motor model complexity on voltage and torque. Optimum performance conditions in the field-weakening mode are determined, and the value of motors using sinusoidal induced voltages is explored.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>