Field-weakening Algorithm Research Articles

Model Predictive Control Based Field-Weakening Strategy for Traction EV Used Induction Motor

The field-weakening scheme is generally adopted for traction motors to achieve a wider speed range where the common proportional and integration compensator is needed to regulate the flux-producing current. However, the regulator performance deteriorates due to dc-link voltage disturbances and motor parameter nonlinearities in the different speed regions. To solve this issue, a model predictive control (MPC) based field-weakening algorithm is proposed for a traction electric vehicle using a low-voltage induction motor. The augmented prediction state relationship between stator voltage and flux-producing current is established for motor current control. The steady-state error can be eliminated with an integrator embedded within the augmented equation. The overall closed-loop control is presented where the system eigenvalues are adjusted in real time for various speed regions, and accordingly, the controller performance can be evaluated with the amplitude of the eigenvalues. Moreover, the weight coefficient in the cost function can be adjusted corresponding to speed variation for guaranteed motor control performance. The simulation and experimental results are provided to verify the proposed MPC-based field-weakening algorithm.

Three phase induction motor modelling and control using vector control in LabVIEW

In this paper, a speed control system for a three-phase induction motor was modelled and designed within LabVIEW software environment. After structuring the dynamical model of the motor, a current controller was developed to stabilize the system and avoid a wind-up situation. Then, a speed controller was designed, using PID and Field Weakening techniques, to generate the reference current values. The field-weakening algorithm is used to achieve stability at speeds that are higher than the nominal one. An estimator is used to calculate the flux angle and the electro-mechanical speed of the motor. As a result, the system achieved the desired speed with good transient and steady state responses. In addition, the system proved to be robust when the torque load is applied in all cases.

Constrained field-oriented control of permanent magnet synchronous machine with field-weakening utilizing a reference governor

ABSTRACTThis paper presents a complete solution for constrained control of a permanent magnet synchronous machine. It utilizes field-oriented control with proportional-integral current controllers tuned to obtain a fast transient response and zero steady-state error. To ensure constraint satisfaction in the steady state, a novel field-weakening algorithm which is robust to flux linkage uncertainty is introduced. Field weakening problem is formulated as an optimization problem which is solved online using projected fast gradient method. To ensure constraint satisfaction during current transients, an additional device called current reference governor is added to the existing control loops. The constraint satisfaction is achieved by altering the reference signal. The reference governor is formulated as a simple optimization problem whose objective is to minimize the difference between the true reference and a modified one. The proposed method is implemented on Texas instruments F28343 200 MHz microcontroller and experimentally verified on a surface mounted permanent magnet synchronous machine.

Torque capability improvement of sensorless FOC induction machine in field weakening for propulsion purposes

An electric propulsion system is generally based on torque controlled electric drive and DC series motors are traditionally used for propulsion system. Induction machines, which are reliable, low cost and have less maintenance, satisfy the characteristics of the propulsion and reinstating the DC series motor. Field oriented control (FOC) of induction machines can decouple its torque control from field control which allows the induction motor to act like a separately excited DC motor. In this paper, the characteristic control of induction motor is achieved through appropriate design modification of induction motor by varying magnetizing current to produce maximum torque in field weakening (FW) region. Thus to improve the torque capability of induction machine in FW region by varying machine parameters. The sensorless operation of the induction motor is carried out by adopting model reference adaptive system (MRAS) using sliding mode control (SMC) and a FW algorithm based on the voltage and current constraints. The simulation of the induction motor drive models based on the design options have been carried out and analyzed the simulation results.

Robust Constant Switching Frequency-Based Field-Weakening Algorithm for Direct Torque Controlled Reluctance Synchronous Motors

This paper presents an improved direct torque controlled reluctance synchronous motor drive for field-weakening applications. The contribution of this paper is twofold. First, a modified direct torque control (DTC) algorithm is proposed to enable a constant switching frequency, reducing the torque ripples significantly while simultaneously retaining the simplicity of the DTC. Conventional field weakening entails the knowledge of the machine parameters that inevitably degrades the robustness and stability of the overall drive system. To circumvent this problem, an improved field-weakening method robust to the machine parameter variations is also presented. These two methods are combined to achieve a robust field-weakening algorithm for direct torque controlled reluctance synchronous motor drives with constant switching frequency and reduced torque ripples. The validity of the proposed algorithm is verified by simulation and experimental results supplemented in this paper.

A Robust Field-Weakening Algorithm Based on Duty Ratio Regulation for Direct Torque Controlled Synchronous Reluctance Motor

This paper presents a robust field weakening method for the direct torque controlled (DTC) synchronous reluctance motors (RSMs). The proposed method ensures a smooth and stable transition between the maximum torque per ampere and field weakening including the maximum torque per flux regions. In addition, it is also robust to the variation in the machine dq- axes inductances in the field weakening region. The proposed algorithm is amalgamated with a duty ratio regulation based DTC to achieve high performance torque and flux control in the field weakening region. The effectiveness of the RSM drive is verified by both simulations and experiments.

Modeling and Sensorless Direct Torque and Flux Control of a Dual-Airgap Axial Flux Permanent-Magnet Machine With Field-Weakening Operation

This paper presents the modeling and motion-sensorless direct torque and flux control of a novel dual-airgap axial-flux permanent-magnet machine optimized for use in flywheel energy storage system (FESS) applications. Independent closed-loop torque and stator flux regulation are performed in the stator flux ( x-y) reference frame via two PI controllers. This facilitates fast torque dynamics, which is critical as far as energy charging/discharging in the FESS is concerned. As FESS applications demand high-speed operation, a new field-weakening algorithm is proposed in this paper. Flux weakening is achieved autonomously once the y-axis voltage exceeds the available inverter voltage. An inherently speed sensorless stator flux observer immune to stator resistance variations and dc-offset effects is also proposed for accurate flux and speed estimation. The proposed observer eliminates the rotary encoder, which in turn reduces the overall weight and cost of the system while improving its reliability. The effectiveness of the proposed control scheme has been verified by simulations and experiments on a machine prototype.

Influence of the stator winding resistance on the field-weakening operation of the DRFOC induction motor drive

Abstract In this paper, an analysis of the influence of the stator winding resistance on the field-weakening operation of the induction motor drive based on the Direct Rotor Flux Oriented Control (DRFOC) is presented. Two scenarions of the optimal field-weakening algorithm (with and without stator winding resistance taken into account) have been compared and verified through simulation and experiment, under different operation conditions of the DRFOC drive system with 3 [kW] induction motor.