Field-weakening Control Research Articles

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.

Extension and improvement of synchronous linear generator based point absorber operation in high wave excitation scenarios

The exploitation of marine wave energy resource has led to the design of numerous Wave Energy Converter (WEC) configurations. The power absorption of a WEC is tightly related to its physical properties and the characteristics of the incoming wave front. Additionally, the operational range of a WEC is limited to certain characteristics of the incoming waves. These restrictions are usually related to limitations in the maximum force of the Power Take-off (PTO) system and the safety of the WEC. As a result, the power production of the WEC must be stopped during sea states of high wave elevation. With the objective of improving the operation of a WEC during these sea states, a Field Weakening (FW) control functionality is proposed to be implemented in the control system of a single-body linear in heave oscillating point absorber with a Permanent Magnet Synchronous Linear Generator (PMSLG) based electrical PTO system. The aim of the aforementioned functionality is to attenuate the magnetic flux in the PMSLG during sea states of high wave elevation. The influence of the size of a WEC on the benefits of the proposed FW functionality is also studied. To that end, two point absorbers with different size are analysed with NEMOH and a wave-to-wire (W2W) model of each WEC is developed. This W2W model enables analysis of the performance and power production of the WECs at different sea states of interest. The obtained results show a remarkable improvement of the operation of a WEC with the implementation of the FW strategy during sea states of high excitation, which leads to an extension of its operation and subsequent additional energy/hydrogen generation.

A comparative dynamic analysis between model predictive torque control and field‐oriented torque control of IM drives for electric vehicles

This article compares two torque control methodologies, model predictive control (MPC), and field-oriented control (FOC), for induction motor (IM) control over a wide speed range applied to an electric vehicle driving system (EVDS). The control technologies are designed and developed to control torque to achieve targeted traction according to vehicle specifications and the demands of the driver. For both control techniques, the specified electric vehicle (EV) is driven under and above base speed with stator flux control and field weakening control of the IM, respectively. In EVDS, the dynamic modeling of the power plants, that is, vehicle dynamics, Li-ion battery, IM, and road forces, is considered. The dynamic behavior of the EVDS of a four-passenger city EV is analyzed and evaluated with urban dynamometer driving schedule (UDDS) driving cycle. From simulations and performance appraisal, the comparison between FOC and MPC is investigated.

Speed Regulation System of Permanent Magnet Synchronous Motor Field Weakening Control Based on Model Predictive Control

The paper is based on the theoretical analysis of motor field weakening control, design field weakening control system based on voltage feedback. In this research, MPC control algorithm is introduced into speed loop. Under field weakening control strategy, the designed MPC controller is applied to motor control system. Finally, the simulation results show: under field weakening control, MPC controller has better robustness and stronger anti-interference ability than PI controller, which improves system stability.

Comparative Performance of Induction Motor Speed Controller System with Flux Weakening Control

In general induction motor not work optimally because cannot reach the maximum speed of the rating. In this paper, simulation is used with several methods, named Maximum Torque Per Ampere (MTPA) and Field-weakening. Simulation of the methods used the function on MATLAB C-Mex and implemented on block of Simulink. The Field-weakening is control speed of the induction motor by decreased flux. The goal is to produce motor speed above the rating. The method of field-weakening control with addition of |iq | used as reference , which will be used to limit . The result of the study is a comparison between the two methods to verify reliability. Simulations results showed that induction motor speed controller using field-weakening control with addition |iq | better performance.

Minimum-Nonlinear-Voltage Method for Torque Ripple Suppression in Induction Motor Overmodulation and Field-Weakening Control

The overmodulation-based nonlinear voltage extension could increase the maximum output torque of the induction motor (IM) in the field-weakening (FW) region. Since the voltage distortion increases with the deepening of overmodulation degree, the extreme nonlinear voltage extension (six-step voltage) is only worthwhile in maximum torque demand conditions. However, the conventional overmodulation-FW scheme always adopts the six-step voltage regardless of torque demand, leading to severe torque ripple. To solve this problem, the minimum-nonlinear-voltage (MNV) method is proposed to satisfy the torque demand with minimum overmodulation-voltage nonlinearity. The difference between the limiting and the feedback values of the torque current is used for suppressing the nonlinear voltage extension during a nonmaximum torque demand state. The quantitative relation between the torque ripple and torque demand of the MNV method is calculated and compared with that of the conventional six-step-FW method. Analysis shows that the MNV method can eliminate the torque ripples of low and medium torque demand conditions completely and partially, respectively. The effectiveness of the proposed method is verified experimentally on a 3.7 kW IM platform.

CCS-MPC for PMSM with Wide Speed Range based on Variable DC-Bus Voltage Control applied to the Flywheel Energy Storage System

In this paper, in order to verify the effect of variable DC-bus voltage control, CCS-MPC (Continuous-Control-Set MPC) control is used to research the control of PMSM (Permanent-Magnet Synchronous Machine) in a wide speed range. In order to maximize the speed of PMSM, the MTPA control, the field weakening control and the variable DC-bus voltage control are applied in the different speed range of PMSM. CCS-MPC can eliminate the control delay by controlling the predicted step size. When CCSMPC is applied to the PMSM control with a wide speed range, the advantages of strong adaptability of CCS-MPC can be exerted.

Overmodulation Index Optimization Method for Torque Quality Improvement in Induction Motor Field-Weakening Control

The overmodulation canimprove the utilization of dc-link voltage in the induction motor (IM) field-weakening (FW) control, thereby extending the maximum output torque. Nevertheless, the high modulation index (MI) will cause severe torque ripple. To figure out the relation between the torque ripple and MI, the amplitude of torque ripple with different MI is calculated quantitatively. Then, a torque quality evaluation function (TQEF) is designed to evaluate the torque quality in overmodulation-FW region by considering both fundamental torque extension and torque ripple suppression. On this basis, a modulation index optimization module is proposed for the maximum TQEF value realization. The analysis shows that the studied method could achieve the optimal trade-off between the fundamental torque extension and the torque ripple suppression. The TQEF value of the studied method is higher than that of the conventional six-step voltage method and the inscribed circle voltage method, meaning that the torque quality is optimized. Finally, the effectiveness of the studied method is verified experimentally on an advanced RISC machines (ARM)-based 3.7 kW IM platform.

Unified Complex Vector Field-Weakening Control for Induction Motor High-Speed Drives

The voltage closed-loop field-weakening scheme (VCFS) is an effective method to achieve the maximum output torque for induction motor high-speed drives. However, the cross-coupling between the inner current and outer voltage loops leads to system performance deterioration. To address this problem, this article proposed a unified complex vector field-weakening control. First, the inherent coupling problem in VCFS is analyzed based on the double closed-loop structure. On this basis, a complex vector structure is designed to unify the inner current and outer voltage loops, following with a decoupled criterion for controller coefficient selection. Compared with the conventional VCFS, the studied scheme can eliminate the natural complex vector zero in the voltage loop, leading to current ripple and voltage overshoot reduction. The experimental results confirm the effectiveness of the investigated scheme.

Phase Lead Compensation of a Phase-Locked Loop in an IPMSM for Air-Conditioner Compressors

In this study, an interior permanent magnet synchronous motor (IPMSM) for single-rotor air conditioner compressors with small inertia is studied, which adopts a sensorless control based on the phase-locked loop (PLL). Owing to the large periodic motor speed fluctuations, the speed and rotor angle of these compressors calculated by the PLL have inherent lagging phase shift and amplitude attenuation, which deteriorates the field weakening control performance and leads to larger speed fluctuations and current oscillations. In this study, a novel phase lead compensated PLL (PLC-PLL) was proposed to reduce the angle error between the real rotor position and estimated rotor position as well as to improve the performance of field weakening control. This method compensates the phase shift of the calculated angle and then reduces the angle error and speed fluctuations. Furthermore, the method of setting parameters for the PLC-PLL is also given. The experimental results confirm that this scheme can greatly reduce the angle error and the fluctuations of speed and currents, which improves the performance of the controller.

A Study on the Core Loss of SPWM Inverter Drive IPMSM considering High Frequency Harmonics

In the paper, the core loss of SPWM inverter drive IPMSM is analyzed considering high frequency harmonics caused by SPWM and field weakening control. The output current of SPWM inverter has many high frequency harmonics at the field weakening region. The high frequency harmonics would affect the core loss on each part such as the yoke, teeth, shoe, and rotor. Therefore, IPMSM core of double layer type is divided into 6 parts to analyze the core loss in each part. In order to calculate the core loss considering the harmonics, the SPWM current is required. This is extracted by linking the SPWM inverter drive IPMSM. FEM analysis is used to compare the core loss when sinusoidal current and SPWM current are applied. The result that which part of the core is most affected is analyzed by FFT analysis applying the P.U. system.

A Parameter-Independent Optimal Field-Weakening Control Strategy of IPMSM for Electric Vehicles Over Full Speed Range

The rest if this article proposes a field-weakening control strategy along with two characteristic curves of IPMSM under electric vehicle driving conditions, where the operation speed, load torque, and target torque change rapidly and continuously. Two characteristic curves, the maximum torque curve, and the switching torque curve are introduced to obtain a strategy that can generate the optimal operation point with minimum stator current at any machine speed. The reference current of the optimal operation points can be derived from both calculation method and conventional calibration method. However, sometimes it is difficult to get solutions directly by the calculation method, not to mention it relies on precise motor parameters that vary with the temperature and magnetic saturation. Additionally, conventional calibration method is really a time-consuming process. In this article, a much simpler approach to obtain reference current based on polynomial fitting is presented, which has a great performance on fitting precision and much less workload with only one additional operation point to be calibrated except for the two characteristic curves. With this fitting method, the reference current generation procedure becomes completely parameter independent. The proposed strategy is demonstrated through simulations and test bench results.

Analysis and Optimization of Current Dynamic Control in Induction Motor Field-Weakening Region

The maximum-torque-output (MTO) trajectory can achieve optimal current distribution for induction motor (IM) field-weakening (FW) control. To provide the dynamic model for MTO, this letter proposes quantitative analysis of the current dynamic character in FW control. As the current vector moves along MTO trajectory, the current changing rate and voltage margin requirement are calculated to study the dynamic control objective and the realization condition of FW control. According to the summarized changing law of voltage margin requirement, the d -axis voltage margin priority approach is applied to the IM FW system for current dynamic optimization. The effectiveness of the studied method is verified through comparison experiments on an advanced RISC machine (ARM)-based 3.7-kW IM platform.

Control strategy for optimising the thrust of a high‐speed six‐phase linear induction motor

In this study, a short primary six-phase linear induction motor (LIM) operating in high-speed non-periodic transient conditions is used as an object of study. In consideration of the coupling terms related to the dynamic end effect, the motor model is simplified and the vector control equation is deduced. A vector control strategy for the real-time modification of slip-frequency and torque current is proposed for dynamic thrust compensation. On this basis, considering the problems of thrust decay caused by dynamic end effect and dc-link voltage drop, this study puts forward a field-weakening control method to keep thrust constant before its decrease in the field-weakening region. The method makes it possible for the LIM to overcome the thrust decay and the narrowing of voltage limits under the high-speed operating conditions. The simulation and experimental results show that the proposed control strategies are useful for optimising the thrust in the transient process thus to realise the high-speed operation of the motor.

Circular Arc Voltage Trajectory Method for Smooth Transition in Induction Motor Field-Weakening Control

In the transition process from the base-speed region to the field-weakening region of induction motor (IM), the voltage margin would suddenly disappear due to the limited inverter voltage. This insufficient voltage margin would deteriorate the current control of IM, causing severe voltage saturation and current ripple. To address this problem, a circular arc voltage trajectory method is proposed with the smooth transition-combined field-weakening controller. The voltage and current behavior are analyzed quantitatively during the transition process. The theoretical analysis shows that the studied circular arc trajectory can suppress the sudden decrease of the voltage increasing rate in the transition region, leading to the reduced voltage saturation and current ripple. The sufficient voltage margin and smooth current can be realized at the cost of <10% voltage utilization ratio. The effectiveness of the studied method is verified by contrast experiments on an ARM-based 3.7-kW IM platform.

Approaching the Ideal BLDC Motor: A Novel Electronic Speed Controller System for a Generator-Converted BLDC Motor with Field Weakening Feature

The concept of an ideal Brushless DC (BLDC) motor which has adjustable rotor magnetic field offers an opportunity for wider BLDC area of implementation as a very versatile electric powerhouse especially in variable load areas such as on electric vehicle or other people movers. Characterized by its high-efficiency level, low maintenance and long service duration, the lack of physical commutation brush like in regular DC motor dictates the requirement of an electronic control system to regulates its commutation.&#x0D; &#x0D; An electronic control system equipped with rotor field control capability in a collaboration with an ideal BLDC motor, is believed to offers wider implementation opportunity. Unlike a normal BLDC motor which has a standard power curved characterized with maximum power is only achievable in one specific speed, if properly controlled will have an adjustable maximum power in a wide range of rotational speed. &#x0D; &#x0D; This study proposes a novel approach to an ideal BLDC implementation through novel electronic speed controller with rotor field control in addition to normal standard motor power control. As there is no such thing as an ideal BLDC motor at the current moment, an automotive generator which has an electromagnetic rotor is converted to become a BLDC motor as an effort to approach the ideal BLDC motor concept. Field weakening, the term used for adjusting rotor magnetic field in induction motor control, is adopted as the term for adjusting the BLDC rotor field in operation. Further, a novel an electronic control system is developed which special features to also control the rotor magnetic field.&#x0D; &#x0D; The converted generator has been found to able to function like an ideal BLDC motor, by adjusting the electromagnetic rotor in its operation. It has been found to be able to provides maximum motor power within a wide range of rotational speed. Through rotor field adjustment, the converted generator provides a real-time versatile capability of allocating its power to either the high torque at low motor speed or to a very high speed at minimum torque. 39% to 81% operational efficiency levels have been achieved during the experiment, rendering the performance level of the converted generator and controller way above brushed DC motor and in par with most of standard BLDC motor.&#x0D; &#x0D; The Field Weakening control has also been found to be useable for speed control. Further, a Proportional &amp;ndash; Integral close-loop speed regulation has also been developed for both motor and rotor control and was found to be able to works subsequently with seamless transition between each other.

Design and control of permanent magnet assisted synchronous reluctance motor with copper loss minimization using MTPA

Abstract It is necessary to find the suitable d - and q -axis reference currents to control PMA-SynRM motors with high efficiency. This paper presents the maximum torque per ampere (MTPA) to minimize the copper losses of the system and utilizes the field weakening control to operate above the rated speed of the PMA-SynRM. The copper losses equation and electromagnetic torque are used to optimize the d - and q -axis current references. A small-scale 1 kW prototype PMA-SynRM was designed and manufactured to test and examine the proposed control in the laboratory. The proposed algorithm was digitally carried out using the MicroLab Box dSPACE. The simulation results show that the copper losses of the machine with the MTPA algorithm are lower than those without the MTPA algorithm. The PMA-SynRM operates above the base speed of ~ 70 % in the constant power region by mean of field weakening control.

Optimization of vector control torque ripple of permanent magnet synchronous motor based on internal model principle

Due to the dead zone effect caused by the non-ideal device of inverter, the currents of the quadrature and straight axis in the synchronous rotation coordinate of permanent magnet synchronous motor (PMSM) contain a large number of harmonic components, resulting in violent torque harmonics. Based on the field weakening control in single current regulator of interior permanent magnet synchronous motor (IPMSM), this paper gives an analysis of the reason for speed fluctuation, and a novel current compensation control strategy based on internal model control is proposed. By this means, the influence of harmonic currents on electromagnetic torque can be reduced meanwhile the advantage of single current regulator in filed weakening control is fully exploited. The feasibility and effectiveness of the proposed scheme are evaluated by Simulation analyses and experimental results.

Maximum Torque Analysis and Extension in Six-Step Mode-Combined Field-Weakening Control for Induction Motor Drives

This paper presents a six-step mode-combined field-weakening control scheme to improve the maximum output torque of induction motor (IM) in the voltage-extension region. Compared with the conventional inscribed circle and hexagon methods, the proposed six-step mode method can increase the utilization of dc-link voltage, leading to extended maximum output torque capability. However, the six-step mode operation will inevitably result in torque ripple and current harmonic. To figure out the quantitative relation between the torque extension and ripple, an “equivalent-circuit”-based method is proposed for theoretical torque analysis in six-step mode. To cut off the main current harmonic (sixth harmonic), a second-order generalized integrator based band-stop filter is designed for the feedback current in the current loop. The designed filter can achieve IM stable operation in a six-step mode without affecting the bandwidth of the current loop. The experimental results from a 3.7-kW IM setup verify the effectiveness of the proposed scheme.

Field Weakening Operation Control Strategies of PMSM Based on Feedback Linearization

Based on current research into the mathematical model of the permanent magnet synchronous motor (PMSM) and the feedback linearization theory, a control strategy established upon feedback linearization is proposed. The Lie differential operation is performed on the output variable to obtain the state feedback of the nonlinear system, and the dynamic characteristics of the original system are transformed into linear dynamic characteristics. A current controller based on the input–output feedback linearization algorithm is designed to realize the input–output linearization control of the PMSM. The current controller decouples the d–q axis current from the flux linkage information of the motor and outputs a control voltage. When the motor speed reaches above the base speed, the field-forward and straight-axis current components are newly distributed to achieve field weakening control, which can realize the smooth transition between the constant torque region and weak magnetic region. Simulation and experimental results show the feasibility and viability of the strategy.