Flux-weakening Control Research Articles

Improvement on Flux Weakening Control Strategy for Electric Vehicle Applications

This paper proposes an optimized flux weakening (FW) control strategy for interior permanent-magnet synchronous electric motor to address the critical issues that could occur under torque setpoint transition in flux weakening region, due, for example, to an emergency braking. This situation is typical in electric vehicles where the electrical machines operate over a wide speed range to reach high power density and avoid gearboxes. Two modified traditional flux weakening strategies are proposed in this paper to improve torque control quality during high speed torque transition. The proposed modified control strategies were validated both by Matlab/Simulink simulations, modeling the power train of a light vehicle application, and extensive experimental tests on a dedicated test bench.

Maximum Torque per Voltage Flux-Weakening Strategy With Speed Limiter for PMSM Drives

This article presents an enhanced flux weakening (FW) control scheme for permanent magnet synchronous motors, focused on electric vehicle applications. The novelty of the proposed algorithm is the integration in a unified scheme of both the accelerator pedal as torque reference and the cruise speed limiter as speed limit, without interfering between them until this limit is achieved. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis current references are calculated from the proposed algorithm by using a polar coordinate system and a per-unit system. The latter is based on the characteristic machine parameters, which aim to ease and simplify the algorithm implementation. Moreover, it takes advantage of the smooth transition between the low back electromotive force zone and the FW zone thanks to a voltage loop, which changes the current-vector angle. Another fundamental merit of the proposed scheme is its capacity to work in all the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> plane throughout the maximum torque per ampere, constant torque, current and voltage limit, maximum torque per voltage, and constant speed strategies without switching the algorithm. Simulations and experimental results from a real exterior-rotor interior permanent magnet synchronous motor direct-drive e-motorbike verify the effectiveness of the proposed method.

Development of FW and MTPV Control for SynRM via Feedforward Voltage Angle Control

In order to develop a wide speed range operation of the synchronous reluctance motor (SynRM) drive system for constant torque, constant power, and reduced power regions, an extended speed control (ESC) with maximum efficiency (ME), flux weakening (FW), and maximum torque per voltage (MTPV) is proposed in this article. First, a conventional FW control system with field-oriented control is introduced. Moreover, to achieve the ME operation, a lookup table of the results of ME analysis by using the finite element analysis technology is adopted to produce the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current commands for the current control mode of the SynRM in the constant torque region. Furthermore, the FW voltage controller is employed to produce the incremental value of the stator voltage command to achieve the maximum voltage limit. In addition, a novel feedforward-based voltage angle controller with an MTPV limiter is designed to generate the voltage angle command for the voltage control mode in the constant power and reduced power regions. Finally, the proposed ESC system is implemented in a 32-b floating-point digital signal processor TMS320F28075 and its robustness and effectiveness are verified by some experimental results.

Interior Permanent Magnet Synchronous Motor Drive System with Machine Learning-Based Maximum Torque per Ampere and Flux-Weakening Control

An interior permanent magnet synchronous motor (IPMSM) drive system with machine learning-based maximum torque per ampere (MTPA) as well as flux-weakening (FW) control was developed and is presented in this study. Since the control performance of IPMSM varies significantly due to the temperature variation and magnetic saturation, a machine learning-based MTPA control using a Petri probabilistic fuzzy neural network with an asymmetric membership function (PPFNN-AMF) was developed. First, the d-axis current command, which can achieve the MTPA control of the IPMSM, is derived. Then, the difference value of the dq-axis inductance of the IPMSM is obtained by the PPFNN-AMF and substituted into the d-axis current command of the MTPA to alleviate the saturation effect in the constant torque region. Moreover, a voltage control loop, which can limit the inverter output voltage to the maximum output voltage of the inverter at high-speed, is designed for the FW control in the constant power region. In addition, an adaptive complementary sliding mode (ACSM) speed controller is developed to improve the transient response of the speed control. Finally, some experimental results are given to demonstrate the validity of the proposed high-performance control strategies.

Flux-Weakening Control of Dual Three-Phase PMSM Based on Vector Space Decomposition Control

This article proposes a flux-weakening (FW) control for dual three-phase permanent magnet synchronous machine (DTPMSM) based on vector space decomposition (VSD) control, where the output voltage in αβ subplane is employed for voltage feedback in the FW control loop. As the fundamental components are mapped to αβ subplane while the fifth and seventh harmonics are projected to harmonic z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> subplane, the FW current from this new control in αβ subplane is sixth harmonic-free regardless of the fifth and sixth harmonics being resulted from the nonsinusoidal back electromotive force (EMF) or inverter nonlinearity. The proposed control is compared with the conventional FW feedback control extended for DT-PMSM, where the FW control is applied to the two sets of three-phase windings separately. The experimental results show that the proposed FW control based on VSD is superior to the conventional FW control in terms of reduction in current unbalance and harmonic currents.

High-speed control strategy for permanent magnet synchronous machines in electric vehicles drives: Analysis of dynamic torque response and instantaneous current compensation

Flux-weakening control strategy of interior permanent magnet synchronous machines have a massive significance to enlarge the operational speed of electric vehicles (EVs) and to facilitate the power integration. However, how to keep the torque stability and achieve the fast response should be given the top priority. In order to facilitate the flux-weakening control application on EVs, a novel flux-weakening control strategy with fast transient current response is proposed. In detail, the change of dynamic voltage margin and its response are analyzed in this paper. Accordingly, the flux-weakening control is proposed through the collaborative control of the dynamic current compensation and the d-axis current-error adjustment. To fully evaluate effectiveness of proposed strategy, the traditional PI-based voltage-closed flux-weakening and the low-pass-filter method are constructed for comparison. The simulation and experimental results illustrate that the proposed strategy can achieve the fast torque response and also have the capacity to reduce the torque fluctuation of the stable state.

Analysis of Novel Hybrid-PM Variable-Flux PMSMs With Series–Parallel Magnetic Circuits

The development of traditional permanent magnet synchronous machines (PMSMs) in electric vehicle (EV) industry is limited by the unalterable permanent magnet (PM) excitation field. Variable-flux PMSMs are considered as a good candidate for EV propulsion for their ability to operate in a wide speed range with high efficiency by manipulating the magnetization state dynamically. A novel hybrid-PM variable-flux PMSM with series-parallel magnetic circuits is proposed in this article. The structure and operating principle of the proposed machine are introduced. The electromagnetic performances of the proposed machine are analyzed and compared with the series-connected and parallel-connected variable-flux machines, and the proposed machine combines the advantages of these two kinds of machines. The inductance characteristics of the proposed machine are analyzed by frozen permeability method (FPM), and the variation laws of inductance are quite different in different magnetization states and load conditions. The torque capacity of the proposed machine is analyzed. The torque ripple can be significantly reduced and the output torque can be improved by properly applying flux-weakening control.

A Comprehensive Optimization Control Method for Hybrid Excitation Synchronous Motor

Hybrid excitation synchronous motor (HESM) offers the advantages of a convenient flux regulation and a wide range of available speeds. As such, it may be conveniently employed in the fields of electric vehicle and aerospace. In this paper, based on a suitable control strategy for vector and speed partition, we put forward a speed control method for HESM which shows optimal efficiency. On the one hand, our method aims at minimizing the copper loss by an optimal configuration of theq-axis current, thed-axis current, and the excitation current under the constraint voltage at the armature end. On the other hand, we conduct a comprehensive analysis of the effects of the flux-weakening speed coefficient on the operating performance of the motors and suggest a self-adaptive control method to regulate that coefficient and further improve the overall performance of the motors, including their speed-range regulation, their efficiency, and their dynamical properties. The proposed flux-weakening control method has been assessed by simulations and HESM-driven experiments. Results have confirmed the feasibility and optimality of our method.

Flux-Weakening Control for Variable Flux Reluctance Machine Excited by Zero-Sequence Current Considering Zero-Sequence Resistive Voltage Drop

In the control of variable flux reluctance machine (VFRM) excited by zero-sequence current, neglecting the zero-sequence resistive voltage drop would cause a large calculation deviation of the stator voltage, which can saturate the inverter and influence the switching from constant torque region to flux-weakening region. To solve with this problem, a flux-weakening control method considering the zero-sequence resistive voltage drop for VFRM is proposed. Firstly, the relationship between dq-axis voltages, zero-sequence voltage and the maximum voltage is presented. Secondly, based on the deduced voltage constraint, the calculation of optimal reference currents in flux-weakening region is presented by using Lagrange multiplier method. Since the zero-sequence voltage is considered, the calculation accuracy of the stator voltage and the utilization rate of DC link voltage are improved, which improves the output power capability. Finally, the proposed method is verified by the experimental results.

Parameters Compensation of Permanent Magnet Synchronous Motor in Flux-Weakening Region for Rail Transit

This article proposes a dual-parameters compensation control method to improve the torque accuracy of permanent magnet synchronous motor (PMSM) in flux-weakening region for rail transit. For the sake of the feature that six-step operation is the essential operation of rail transit and switching frequency is very low, the proposed method works on the single q-axis current regulator-variable voltage angle (SQCR-VVA) flux-weakening control strategy for PMSM operation. Based on SQCR-VVA flux-weakening control, impact of inaccurate parameters is analyzed in seven different conditions, and inaccurate parameters (d-axis inductance, q-axis inductance and permanent magnet flux linkage) result in the errors on d-axis current response and d-axis feed forward voltage. In order to eliminate the impact of the three parameters at the same time, dual compensation regulators are applied to the proposed method. Error of q-axis inductance is identified by the d-axis voltage regulator. The whole impact of inaccurate d-axis inductance and permanent magnet flux linkage is eliminated by the d-axis current regulator. The proposed method is subsequently tested on PMSM and shows quite good performance on the improvement of torque accuracy.

GPIO-Based Nonlinear Predictive Control for Flux-Weakening Current Control of the IPMSM Servo System

This paper proposes a generalized proportional integral observer (GPIO) based nonlinear predictive control (NPC) for an interior permanent magnet synchronous motor (IPMSM) to improve the flux-weakening (FW) current control performance against the complex nonlinear cross-coupling terms and the IPMSM parameters’ variations. First, the IPMSM is remodeled to further analyze the FW control difficulties caused by such cross-coupling terms and parameters variations. Considering the parameters’ variations as a kind of disturbance, a GPIO is then designed to compensate for such disturbance. A GPIO-based NPC is finally designed to handle the nonlinear cross-coupling terms to obtain an optimized current control performance. Experiments on a digital signal processor (DSP) based IPMSM servo system validate the workability of the proposed control scheme.

Research on Control Methods of Six-phase Permanent Magnet Synchronous Motor

Compared with three-phase motors, multi-phase motor speed control systems have many advantages, which make them have good prospects in many fields, such as the control system of electric vehicle power equipment. In these control systems, it is necessary for the motor to have a wider speed range. This paper takes six-phase permanent magnet synchronous motors as the research object, and analyzes several control methods of vector control theory for permanent magnet synchronous motor control based on the derivation of its mathematical model, including i d = 0 control, maximum torque per ampere (MTPA) control, and flux weakening control. Finally, MATLAB / Simulink is used for simulation research, and the advantages and disadvantages of different control methods are compared. In this paper, a strategy of MTPA control below the base speed and flux weakening control above the base speed is proposed, which not only reduces the copper consumption of the motor, but also expands the speed-up range of the permanent magnet synchronous motor.

Adaptive Voltage Feedback Controllers on Nonsalient Permanent Magnet Synchronous Machine

This article investigates the nonlinear behavior of the conventional voltage feedback flux-weakening control, i.e., the voltage magnitude feedback control on the nonsalient permanent magnet synchronous machine, and proposes an adaptive control parameter tuning method for the voltage feedback controller. Due to less voltage margin in the flux-weakening region, the current dynamic performance is degraded. This issue is more serious when the system operates in the overmodulation region and could affect the system's stability. Based on the designed voltage feedback controller, the system performance in the flux-weakening and overmodulation regions is further improved by utilizing the current and voltage reference modifiers. Consequently, the system can operate well in both linear and overmodulation regions with the specified scaling factor, which is beneficial to general-purpose applications. The viability of the proposed method is demonstrated by the experimental results.

Voltage feedback based flux-weakening control of IPMSMs with fuzzy-PI controller

Voltage feedback based flux-weakening control of IPMSMs with fuzzy-PI controller

Fuzzy Logic Speed Control of Permanent Magnet Synchronous Machine and Feedback Voltage Ripple Reduction in Flux-Weakening Operation Region

Voltage feedback flux-weakening control has the advantages of simplicity and robustness against parameter variation. However, due to less voltage control margin in the flux-weakening region, the increased feedback voltage ripple could deteriorate the system performance in the flux-weakening region and may even cause oscillation. In this article, based on a nonsalient permanent magnet synchronous machine, the steady-state feedback voltage ripple in the flux-weakening region are analyzed first. It shows that the feedback voltage ripple caused by the current command ripple could dominate in some flux-weakening regions. Consequently, the speed bandwidth based on the conventional speed proportional-integral (PI) controller in the flux-weakening region can be hardly increased, which leads to poor dynamic performance. In order to obtain both fast speed dynamics and less steady-state ripple, especially in the flux-weakening region, an adaptive fuzzy logic (FLC) speed controller is designed and compared with the conventional speed PI controller. With the adaptive FLC, the dc-link voltage utilization can be increased and better flux-weakening capability can be obtained. Finally, the improved performances are verified by the experimental results.

Study on Lumped Magnetic Circuit in Interior PM Machines for Aircraft Electric Green Taxiing Systems

This paper considers the possibility of adopting a V-shaped interior permanent magnet (IPM) machine for Electric Green Taxiing (EGT) application. This rotor topology of the IPM machine has been optimized to reduce the torque ripple and iron loss. An analytical lumped magnetic circuit model was adopted to minimize the total harmonic distortion (THD) of air-gap flux density for the V-shaped IPM machine. The results of analytical lumped magnetic circuit model were compared with finite-element analysis (FEA). With the optimized rotor structure parameters, the torque ripple at the maximum torque per ampere and iron loss at the flux-weakening control were investigated.

Modified Flux-Weakening Control for Electric Vehicle with PMSM Drive

Effective control of electric motor in Electric Vehicles (EVs) is critical for providing better driving experience and increased reliability. Conventional Proportional Integral (PI) based Field Oriented Control (FOC) of drive systems suffers from performance degradation under parameter variation due to aging, temperature rise etc. In this work, a Look-Up Table (LUT) based FOC with Sliding Mode Control (SMC) is proposed for EV drive system and its performance is analyzed. Results affirm that the performance of SMC based control scheme is more robust than that of PI controller based scheme.

An Improved UDE-Based Flux-Weakening Control Strategy for IPMSM

Interior permanent magnet synchronous motors (IPMSMs) are usually used in electric vehicle drives and in other applications. In order to enlarge the speed range of IPMSMs, the flux-weakening control method is adopted. The traditional flux-weakening control strategy degrades the control performance because of parameter mismatches caused by variation of motor parameters. An improved uncertainty and disturbance estimator (UDE)-based flux-weakening control strategy is proposed for IPMSM drives in this paper. The parameter tuning method in the UDE-based control is improved. In addition, a flux-weakening adjusting factor is put forward to reduce the torque fluctuation when the operation point switches between the constant torque region and the flux-weakening region. This factor can be adjusted online by a lookup table. Finally, the validity of proposed method is verified by the simulation and experimental results. The results show that the proposed control strategy can effectively enhance the robustness of the system in the flux-weakening region, and make the system switch more smoothly between the constant torque region and the flux-weakening region.

Parameter Optimization of Adaptive Flux-Weakening Strategy for Permanent-Magnet Synchronous Motor Drives Based on Particle Swarm Algorithm

Operating in the high-speed range is necessary for high-performance permanent-magnet synchronous motor (PMSM) drives. However, due to the back electromotive force effect, the PMSM is approaching the voltage limit at field decreasing scope. This paper presents a new flux-weakening scheme along with an improved vector control strategy to alleviate the influence of this problem. Control parameters of the anti-windup proportional and integral (AWPI) controller are optimized off-line in relying on an adaptive velocity particle swarm optimization (AVPSO) algorithm. The AVPSO algorithm considers the summation of AWPI measurement error which is the objective function of the optimization problem without knowing the transfer function of the plant. Hence, the tuned flux-weakening controller with a filter is used to set the flux level without saturating the current controllers. Meanwhile, the other controllers of inner and outer loops award a great dynamic and steady-state performance for the PMSM. In the proposed scheme, the flux-weakening control is not dependent on machine parameters that adapts the flux level automatically and provide a fast transition between the constant torque region and the field-weakening region. Effectiveness and advantages of the proposed scheme are presented in this paper through both simulation and experimental results.

Design for the Interior Permanent Magnet Synchronous Motor Drive System Based on the Z-Source Inverter

The permanent magnet synchronous motor (PMSM) running above the base speed requires flux-weakening control, which is usually realized by the direct-axis demagnetization current generated by the vector control, thus leading to a decrease in the system efficiency in the flux-weakening region. In addition, the motor power output range is limited by the inverter output voltage and current level. In this paper, a Z-Source drive PMSM control system with adjustable DC-link voltage was proposed to improve the efficiency of the motor system. The proposed system was experimentally verified. The response time of DC-link voltage is 10 ms and the overshoot is 3%, indicating good dynamic characteristics. Compared with the flux-weakening scheme, the Z-Source inverter scheme can achieve higher efficiency (about 3%) when the PMSM speed was set to 650 r/min.