Flux-weakening Control Research Articles

Flux-Weakening Control of Linear Induction Motor Drives Considering the Primary Resistance and End Effect

Flux-Weakening Control of Linear Induction Motor Drives Considering the Primary Resistance and End Effect

Improved Flux Weakening Control Strategy for Five-Phase PMSM Considering Harmonic Voltage Vectors

This article proposes a novel flux weakening scheme for five-phase PMSM with active harmonic currents injection. The conventional flux weakening control schemes applied in the five-phase PMSM do not consider the voltage limit drop in the fundamental subspace due to the harmonic current controller. Thus, the derivation between the reference current trajectory and actual current trajectory would cause the current distortion when applying deadbeat current controller (DBCC). This article analyses the precise voltage limit circles considering the voltage drop caused by the resistance and harmonic currents control at first. Then, a feed-forward flux weakening control algorithm is designed to optimize the current trajectory online. The gradient descent method is used to ensure the converge speed and stability of the optimized current trajectory. Thirdly, the peak value of phase currents would be clipped by the harmonic currents to prevent the inverter current limit, where a new non-linear harmonic current controller is designed to precisely control the harmonic currents. Finally, the DBCC and modified SVPWM technology are utilized to generate the duty cycle. The proposed improved flux weakening control strategy is successfully implemented in an interior five-phase PMSM, and the performance demonstrate the effectiveness of this strategy.

A Novel Flux-weakening Control Method with Quadrature Voltage Constrain for Electrolytic Capacitorless PMSM Drives

In electrolytic capacitorless permanent magnet synchronous motor (PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-\psi_{\mathrm{f}}/L_{\mathrm{d}}$</tex> during the high speed operation, the flux-weakening control loop will transform to a positive feedback mode, which means the reduction of flux-weakening current will lead to the acceleration of the voltage saturation, thus the whole system will be unstable. In order to solve this issue, this paper proposes a novel flux-weakening method for electrolytic capacitorless motor drives to maintain a negative feedback characteristic of the control loop during high speed operation. Based on the analysis of the instability mechanism in flux-weakening region, a quadrature voltage constrain mechanism is constructed to stabilize the system. Meanwhile, the parameters of the controller are theoretically designed for easier industrial application. The proposed algorithm is implemented on a 1.5kW electrolytic capacitorless PMSM drive to verify the effectiveness of the flux-weakening performance.

Variable Incremental Controller of Permanent-Magnet Synchronous Motor for Voltage-Based Flux-Weakening Control

This study presents a variable incremental controller for flux-weakening control in the high-speed operation area of a permanent-magnetic synchronous motor (PMSM). In general, voltage-based flux-weakening control utilizes a reference voltage and a PI controller to generate a flux component current. In this paper, the voltage-based flux-weakening control is performed using the variable incremental controller instead of the PI controller. The variable incremental controller can control the flux component current using only the maximum speed and maximum current of the motor. A method for properly setting an appropriate variable incremental controller using acceleration is additionally presented. A variable incremental controller is applied and, accordingly, the overshoot of the motor speed can be reduced and the speed error of the motor can be minimized by reducing the difference between the actual motor and targeted accelerations. This method can simplify the design of a controller that utilizes flux-weakening control and can be applied to railroad cars whose acceleration does not alter frequently to increase the effect of motor control.

Flux-Weakening Control for Variable Flux Reluctance Machine Considering the Second Order Harmonic in Phase Voltage

Due to the second order harmonic in the phase voltage, the voltage peak value is much higher than the amplitude of its fundamental component in the 6/4 variable flux reluctance machines (VFRMs). Conventionally, the amplitude of the fundamental component in the phase voltage is used to calculate the voltage constraint in flux-weakening control, which results in a large voltage margin and reduces the DC link voltage utilization. To deal with this problem in the VFRMs, the flux-weakening control considering the second order harmonic of the phase voltage is proposed in this paper. In this method, the voltage peak value is used to calculate the current operating points, by using which the maximum voltage utilization in flux-weakening region can be achieved. It shows by using the proposed method a wider the constant torque region owing to the lower voltage margin in the VFRMs, which exhibits higher power output in flux-weakening region. Finally, the method is verified by the test results in the VFRM.

Optimized Anti-Windup Coordinating Strategy for Torque-Maximized High-Speed Flux-Weakening Operation of Constrained Induction Motor Drives

Due to the contradiction between torque-maximized requirements and limited voltage and current constraints, voltage closed-loop flux-weakening strategy is developed to circumvent the saturation problem for maximum torque control of induction motor when the accelerating speed enters high-speed region. At the same time, since voltage inconsistency caused by the saturation is employed to construct flux-weakening controller (FC), anti-windup (AW) item in current regulator needs to be cut off to avoid the conflict. However, the replacement discards part of AWs utility and results in the distortion of command voltage, thus compromising system’s dynamic performance and making the tuning process of proportional-integral controller (PI)-based FC much trickier. To address this issue, an equivalent saturation model is presented. An optimized AW coordinating strategy is proposed, combining a novel structure, so-called virtual voltage buffer, with FC. Through an equivalent proof, it can be transformed into over-modulation block for a convenient implementation. Through its compensation in the transient period, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis current can be quickly and smoothly manipulated in a more concise tuning process. As a result, the overall system possesses a fast acceleration capability with maximum torque and a wide speed range, while retaining a desirable system response. Simulation and experimental results verify the effectiveness of proposed method.

Flux-Weakening Drive for IPMSM Based on Model Predictive Control

This paper presents a flux-weakening model predictive control (FW-MPC) for the interior permanent magnet synchronous motor (IPMSM) drive system. The FW control is a strategy to extend the IPMSM’s operating region. However, the primary FW needs to track the torque reference and maximize the electrical torque per current amplitude with the current and voltage limitations. The two objects make it impossible to solve the FW problem using the optimization method. We proposed an equivalent optimization problem to simplify the complex FW problem, including two objective functions. The MPC is selected as the controller due to its high robustness and transient performance. The constraints from the equivalent optimization problem are added in the MPC to control the IPMSM in the FW region. The simulation and experiment results indicate that the proposed FW-MPC is feasible and effective in driving the IPMSM in the FW region. The proposed FW-MPC can find the optimal point with the maximum electrical torque satisfying the current and voltage limitations. Therefore, the proposed FW-MPC can extend the IPMSM’s operating region, benefiting the IPMSM’s application.

Deadbeat predictive current control of PMSM drives with an adaptive flux‐weakening controller

In practical application, the motor speed may need to be greater than the rated speed, so field-weakening control is required. However, the conventional flux-weakening control requires much tuning work, because multiple PI controllers are used. In order to make the tuning work easier, this paper combines flux-weakening control with deadbeat predictive current control (DPCC) to eliminate two PI controllers in current loop. In addition, this paper also proposes a speed adaptive flux-weakening controller, which can further simplify the tuning work. The effectiveness of this method has been confirmed on a 2.2 kW surface permanent magnet synchronous motor (SPMSM) experimental platform.

A Single-Current-Regulator Flux-Weakening Control for PMSM Under Square-Wave Mode With Wider Operation Range

In the rail transit traction system, the traction motor will operate under square-wave mode at high speed. The voltage amplitude will be fixed under the square-wave mode, while only the voltage angle can be regulated. The single-current-regulator (SCR) method is a good choice to regulate the voltage angle while keeping the voltage amplitude constant. However, the existing SCR methods cannot work stably in the whole flux-weakening area of the infinite speed system. The single <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis current regulator-regulates <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis voltage (SDCR-RQV) method that can provide a wider operation range is proposed in this article. SDCR-RQV is qualified for the permanent magnet synchronous motor (PMSM) used in rail transit, whether it is a finite speed system or an infinite speed system. The proposed method is analyzed in detail and verified by simulation and experimental results.

An Adjustable Wide-Range Speed-Control Method for Sensorless IPMSM Drive Systems

This paper proposes an adjustable wide-range speed-control method for sensorless IPMSM drive systems from standstill, low-speeds, middle-speeds, and high-speeds in the flux-weakening region. A sensorless method and an online parameter estimation method based on the measurement of current-slope under SVPWM with an extension compensation are proposed. The estimated rotor position, rotor speed, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d-q</i> axis inductances, magnetic flux, and torque of the IPMSM are precisely computed by using a current-slope measurement, and then a closed-loop speed control sensorless IPMSM drive system is implemented without requiring any external high-frequency signal injection or a complicated observer. In addition, to achieve a high-performance sensorless IPMSM drive system, the estimated parameters are used for real-time maximum torque per ampere control and flux-weakening control. Finally, the proposed sensorless IPMSM drive system provides a wide operation range from 1 r/min to 3000 r/min with excellent performance in constant-torque regions and flux-weakening regions. A digital signal processor, made by Texas Instrument, type TMS 320F2802, is employed to realize the control algorithm and estimation algorithm. Experimental results show the proposed sensorless IPMSM drive system achieves satisfactory responses, including <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm \,{\mathrm {2.5}}^{\circ }$ </tex-math></inline-formula> of electrical position estimation errors, good dynamic responses, and good tracking responses.

Voltage Control of IPMSM Servo Drive in Constant Power Region With Intelligent Parameter Estimation

A novel voltage control scheme for an interior permanent magnet synchronous motor (IPMSM) servo drive in the constant power region with intelligent estimation of the motor parameter is proposed in this study. In the novel voltage control scheme, a feedforward voltage angle controller is proposed where an intelligent parameter estimation method by using a wavelet fuzzy neural network (WFNN) is developed to estimate the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis inductance online. In this study, in order to minimize the copper loss, a flux-weakening (FW) control scheme under maximum phase voltage is developed first. Then, an adaptive backstepping based nonlinear controller (ABNC) considering nonzero <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current is developed to improve the robustness of the speed control. The Lyapunov stability theorem is used to derive the adaptive law of the online estimation of the lumped uncertainty to ensure the asymptotical stability of the ABNC. Moreover, a feedforward voltage angle controller is developed for the voltage control where the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current controller is retained in order to ensure the steady-state performance of the control system. Furthermore, the WFNN is adopted to estimate the actual <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis inductance value online for the feedforward voltage angle controller to improve the dynamic response. In addition, some experimental results are demonstrated to verify the effectiveness of the proposed voltage control scheme with ABNC in the constant power region.

Variable Switching Frequency Control-Based Six-Step Operation Method of a Traction Inverter for Driving an Interior Permanent Magnet Synchronous Motor for a Railroad Car

Most railroad cars employ a natural ventilation cooling method. For this reason, severe problems occur in the control devices for the railroad cars due to the heat generated by the high-power switching loss. Therefore, the traction inverter for the railroad car requires a control method that can reduce the switching loss. In this paper, we propose a control method for an interior permanent magnet synchronous motor in consideration of the driving conditions of the railroad cars. The proposed method combines a variable switching frequency-based synchronous pulse width modulation control method, a flux-weakening control method that considers the maximum voltage modulation index, and an optimized over-modulation method. Through the proposed method, the utilization rate of the DC-link voltage can be maximized while lowering the switching frequency of the traction inverter as much as possible, and the high-performance current control can be performed in the entire speed region of the railroad car. The validity and effectiveness of the proposed method are verified by the simulation results and the experimental results.

Improved Voltage Flux-Weakening Strategy of Permanent Magnet Synchronous Motor in High-Speed Operation

This paper presents an improved voltage flux-weakening strategy of a permanent magnet synchronous motor (PMSM) in a high-speed operation. The speed control performance using voltage flux-weakening control is not affected by the motor parameters, so it is used in various motors for high-speed operations. In general, the voltage flux-weakening control uses voltage references to generate a flux axis current reference. However, there may be errors between the voltage reference and the actual voltage flowing into the motor. This causes an error in the current reference generation and reduces the efficiency of the inverter and motor due to the use of more current. In this paper, the problems that can occur due to voltage errors were analyzed through theoretical approaches and simulations, and improved voltage flux-weakening control to resolve these problems was presented. This method’s advantage is that the error between the voltage reference and the voltage applied to the motor can be minimized, and the target speed can be reached with minimum current. As a result, it was possible to increase the energy efficiency by reducing the amount of current flowing through the motor. The effect of the improved voltage-based flux-weakening control method was verified through simulations and experiments. As a result, the voltage errors were reduced by approximately 2.16% compared to the general method. Moreover, the current used in the field-weakening control region was reduced by up to 27.17% under the same torque condition.

Advanced deep flux weakening operation control strategies for IPMSM

This paper proposes an advanced flux-weakening control method to enlarge the speed range of interior permanent magnet synchronous motor (IPMSM). In the deep flux weakening (FW) region, the flux linkage decreases as the motor speed increases, increasing instability. Classic control methods will be unstable when operating in this area when changing load torque or reference speed is required. The paper proposes a hybrid control method to eliminate instability caused by voltage limit violation and improve the reference velocity-tracking efficiency when combining two classic control methods. Besides, the effective zone of IPMSM in the FW is analyzed and applied to enhance stability and efficiency following reference velocity. Simulation results demonstrate the strength and effectiveness of the proposed method.

Study on design and flux weakening control of direct drive hub motor

The direct drive hub motor is a motor that directly combines the motor and the wheel. It is accompanied by the development of permanent magnet motor and modern control technology. Permanent magnet synchronous motor (PMSM) is especially suitable for use as hub motor use of its advantages of high efficiency, energy saving, high power and easy control. In this paper, Motor Cad software was applied to optimize the design of an outer rotor PMSM motor of a cellular power, and the simulation and analysis of air gap magnetic density and other performance were carried out. The analysis results not only verify the rationality of the motor design, but also provide a basis for the next study on flux weakening control. The design and control results show that the prototype meets the design requirements fully.

Design Criteria for Flux-Weakening Control Bandwidth and Voltage Margin in IPMSM Drives Considering Transient Conditions

Flux-weakening (F-W) methods based on feedback voltage regulation are widely adopted in interior permanent magnet synchronous motor (IPMSM) drives. Generally, the setpoint must be lower than maximum available voltage, to prevent saturation of current regulators during transients. However, the margin should be small, to exploit torque capability of the machine and avoid additional current magnitude during F-W operation. The trade-off between F-W control bandwidth and the necessity of voltage margin has not been analyzed in-depth in previous literature. In fact, F-W regulator design aiming at a certain bandwidth has been addressed by means of gain adaptation, but the choice of the target bandwidth remained as an open issue. In this article, the crucial transient conditions which can cause the saturation of current regulators, specifically the reduction of input voltage, the fast acceleration of the drive and the transient torque demand, are considered. The input voltage reduction affects the available voltage, while fast acceleration and increase of torque demand push towards higher voltage, requiring disturbance rejection action by the F-W controller. All these conditions are analyzed in terms of worst-case requirement and the proposed analytical modeling is verified by means of simulations and experiments. The findings can be applied in the design of automatic tuning procedures and design for high-reliability or safety-critical applications.

An enhanced feedforward flux weakening control for high‐speed permanent magnet machine drive applications

Permanent magnet machines have been used in the high-speed drive applications due to their high-efficiency, high-power-density, and wide-speed range characteristics. However, control of such high-speed permanent magnet machines machine is always challenging and proper flux-weakening controller design is essential to achieve high performance of these machines. In this paper, an improved feedforward flux-weakening control scheme for interior permanent magnet synchronous machine (IPMSM) drives are proposed. The proposed method identifies optimal d-axis and q-axis currents under different operation regions using maximum-torque-per-ampere curve, voltage limit, and current limit curves with a fast Newton–Raphson algorithm. To ensure the optimal performance of the control mechanism, effects of inductance variations due to the magnetic saturation are considered and an innovative high-frequency staircase voltage injection method is used to identify the q-axis inductance. The experimental results show that compared with other existing flux-weakening methods, the proposed technique can improve the DC-link voltage utilisation without the need to tune any controller gains and can fully utilise maximum available torque with desirable transient performance.

A novel MTPA and flux weakening method of stator flux oriented control of PMSM

Abstract Permanent magnet synchronous motor (PMSM) has the advantages of high efficiency, high power density and high reliability. It has been widely used in electric vehicles, rail transit, industrial transmission and other fields. Compared with the traditional PMSM control strategy, the Indirect stator-quantities control (ISC) of low torque ripple induction motor has high dynamic response performance in the whole speed range, with high stability and strong security. However, due to the inherent characteristics of PMSM, there are still some difficulties in applying ISC strategy, such as solving the load angle corresponding to the current torque, realizing the maximum torque per ampere (MTPA) control and flux weakening control method in the stator field oriented control algorithm of PMSM. In this paper, theoretical analysis and discussion are carried out for the above difficulties, and an indirect stator vector control (ISC) method for PMSM is proposed. Finally, combined with the electric drive application platform of electric vehicle, the simulation and experimental results verify that the proposed ISC control strategy of PMSM also has good dynamic and steady-state performance in the whole speed range.

3-D Equivalent Magnetic Network Modeling and FEA Verification of a Novel Axial-Flux Hybrid-Excitation In-wheel Motor

In order to solve the problems of poor capacity and unsatisfactory efficiency of flux-weakening control for the axial-flux permanent magnet (AFPM) machines with surface-mounted permanent magnet (PM) rotor structure, a new axial-flux hybrid-excitation machine (AFHEM) with double consequent-pole rotors is proposed, which combines the high torque density of the AFPM machine and the flexible flux regulation of the hybrid excitation machine. It meets the stringent requirements of the distributed in-wheel motor electric drive vehicle for high efficiency and high torque density. The topology, principle, and basic electromagnetic properties of the new axial-flux hybrid-excitation in-wheel motor are presented in this article. Based on the complex magnetic circuit of the AFHEM, a 3-D equivalent magnetic network (EMN) model is established. The air-gap flux density, flux linkage, back EMF, torque, and fault tolerance ability of the motor are solved through the EMN model and compared with the 3-D finite element analysis (FEA) to verify its validity and correctness. It is hoped to form a rapid design method for the new type of motor with the complex structure of 3-D magnetic flux path property. Finally, based on the EMN model, the influences of the magnetic saturation on the excitation regulation capability of the proposed AFHEM are analyzed, which provides a guideline for the optimization design of the new AFHE in-wheel motor.

Wide Speed Range Operation Strategy of Indirect Matrix Converter–Surface Mounted Permanent Magnet Synchronous Motor Drive

In order to expand the speed range for an indirect matrix converter–surface mounted permanent magnet synchronous motor drive (IMC-SPMSM), a wide speed range operation control strategy based on a flux-weakening control and an over-modulation method is proposed in this paper. In the stage of the inverter, an IMC over-modulation method is designed, which increases the fundamental voltage transmission ratio (VTR) to 1. In addition, considering the variation of the voltage limit boundary of the IMC with motor speed, flux-weakening control is implemented based on the voltage error feedback method, which maximizes the voltage utilization rate by setting the endpoint of the output voltage vector on the voltage boundary during the flux-weakening operation. In the stage of the rectifier, over-modulation is automatically switched on or off according to operation requirements by a modulation depth controller. Finally, experimental results show that the proposed strategy increases the maximum speed of the IMC-SPMSM by nearly 35% compared to the maximum torque per ampere (MTPA) method. Besides, the enlarged voltage margin by the rectifier stage over-modulation effectively shortens the setting time.