Flux-weakening Control Research Articles

A fuzzy coefficient deep flux weakening algorithm for IPMSM without out-of-control

A fuzzy coefficient q-axis current increment flux weakening (FCCIFW) control method is proposed in interior permanent magnet synchronous motor (IPMSM) drives. The proposed FCCIFW not only simplifies the calculation of flux weakening coefficient according to the derived formula, but also avoids the saturation of current regulator. In FCCIFW, the theoretical calculation formula of conversion coefficient is derived firstly, and then the fuzzy rule base is established according to the formula. FCCIFW not only refrains the use of complex flux weakening calculation formula or fixed control parameters, but also refrains the problem of out-of-control in the process of deep flux weakening control, so as to improve the overall performance in the process of flux weakening. The results show that the proposed method has an effective and correct calculation process and results, Compared with different control methods in the operation process, it shows that the proposed method has more stable control effect, which has great application value in engineering.

Optimal control strategies for PMSM with a decoupling super twisting SMC and inductance estimation in the presence of saturation

This paper deals with optimal control strategies robustified by a decoupling super-twisting sliding mode control (ST-SMC) for permanent magnet synchronous machines (PMSM). In general, ST-SMC is a robust method for controlling systems and guarantees asymptotic convergence in cases where the upper bound of model uncertainties such as disturbances and parametric uncertainties is not known a priori, if the upper bound of the derivative is known. The proposed optimal control strategy is designed for a constant torque reference whose control is implemented in two control regions: maximum torque per ampere (MTPA) and flux-weakening control. In the proposed analysis, the operating point of the motor can also be in the saturation region, which makes the estimation of Ld and Lq in the proposed optimization procedure of particular interest and also important for the decoupling control implemented with ST-SMC. To compensate for typical parameter variations, adaptive parameter estimation is introduced into the control system using an extended Kalman filter (EKF) in combination with a bivariate polynomial. In order to be able to make an assessment of the control performance of the ST-SMC, a comparison with a conventional PI controller is shown at the end of the paper. Measured results using hardware in the loop (HIL) to validate the results and their detailed discussion and analysis are included.

Neural Network With Cloud-Based Training for MTPA, Flux-Weakening, and MTPV Control of IPM Motors and Drives

An interior permanent magnet (IPM) motor is a prime electric motor used in electric vehicles (EVs), robots, and electric drones. In these applications, maximum torque per ampere (MTPA), flux-weakening, and maximum torque per volt (MTPV) techniques play a critical role in the efficient and reliable torque control of an IPM motor. Although several approaches have been proposed and developed for this purpose, each has its specific limitations. The objective of this paper is to develop a neural network (NN) method to determine MTPA, flux-weakening, and MTPV operating points for the most efficient torque control of the motor over its full speed range. The NN is trained offline by using the Levenberg-Marquardt backpropagation algorithm, which avoids the disadvantages associated with online NN training. A cloud computing system is proposed for routine offline NN training, which enables the lifetime adaptivity and learning capabilities of the offline-trained NN and overcomes the computational challenges related to online NN training. In addition, for the proposed NN mechanism, training data are collected and stored in a highly random manner, which makes it much more feasible and efficient to implement lifetime adaptivity than any other methods. The proposed method is evaluated via both simulation and hardware experiments, which shows the great performance of the NN-based MTPA, MTPV, and flux-weakening control for an IPM motor over its full speed range. Overall, the proposed method can achieve a fast and accurate current reference generation with a simple NN structure, for optimal torque control of an IPM motor.

Analysis and Applicability Comparison of Single Current Regulator Methods of PMSM Under Square-Wave Mode

Single current regulator (SCR) control is a popular flux-weakening control for PMSM, which can maintain the output voltage amplitude constant at the maximum value (suitable for square-wave mode), while providing well dynamic performance. Currently, four kinds of SCR control have been proposed separately from different views. The principle of SCR control is summarized from a novel view in this paper. Based on that, another two SCR methods are derived naturally, which are single q-axis current regulator-regulates d-axis and q-axis voltage (SQCR-RDV and SQCR-RQV) methods respectively. More than that, the issue of current regulator structure is discussed in detail. Small signal analysis is adopted to test the system stability while the proper and improper regulators are applied. The influence of the unstable operation is also analyzed by the current locus. Then, appropriate SCR methods are recommended for finite and infinite speed PMSM. The analyses are verified by simulation and experimental results.

A Direct Torque Control Method for CSC Based PMSG Wind Energy Conversion Systems

The Current Source Converter (CSC) technology is well suited for high power wind energy applications. Because it drives generally features like simple converter structure, smooth power injection at the grid side and excellent short circuit protection. The main drawback lays its dynamic torque response. An improved Direct Torque Control (DTC) method is proposed in this paper to overcome this drawback. Using DTC method for Permanent Magnet Synchronous Generators (PMSG) in a wind energy system has some advantages such as, simple control system and topology, ease of tracing Maximum available power from the wind and flux weakening control in high wind speeds. The simulation results demonstrate the effectiveness of the proposed control system, good dynamic response and acceptable MPPT capability.

Torque Closed-Loop Flux-Weakening Control of IPMSM Based on Search Coils

Torque Closed-Loop Flux-Weakening Control of IPMSM Based on Search Coils

Impact of Rotor Excitation Current During Flux-Weakening Control of Hybrid-Excited Permanent Magnet Synchronous Motor

Impact of Rotor Excitation Current During Flux-Weakening Control of Hybrid-Excited Permanent Magnet Synchronous Motor

Investigation of AC Copper Loss Considering Effect of Field and Armature Excitation on IPMSM With Hairpin Winding

As the torque density of traction motors for electric vehicles (EVs) increases, winding technology with a large conductor area, such as hairpin winding, is widely used. However, it has a disadvantage of large AC copper loss affected by the skin and proximity effect. Therefore, the AC copper loss should be considered for deriving characteristics of IPMSM. This paper deals with the maximum torque per ampere (MTPA) and flux-weakening control characteristics of the IPMSM considering AC copper loss. As the AC copper loss is caused by armature and field excitation, a separation process of AC copper loss by each cause is proposed. By using the process, the separated AC copper loss can be analyzed according to the current vector and rotational speed. However, it is inefficient to calculate the AC copper loss according to rotational speed using transient analysis. Therefore, a computationally efficient method of calculating AC copper loss based on magneto-static analysis is presented. In addition, advanced <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d, q</i> -axis equivalent model considering AC copper loss is proposed to analyze MTPA and flux-weakening control characteristics of IPMSM. By using the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d, q</i> -axis equivalent model, the IPMSM can be designed considering the AC copper loss efficiently and accurately.

Model-Free Control for Doubly Salient Permanent Magnet-Generator-Based Tidal Stream Turbine Considering Flux-Weakening Operation

Renewable energy generation is increasingly important due to serious energy issues. A Doubly Salient Permanent Magnet Generator (DSPMG) can be an interesting candidate for tidal stream renewable energy systems. However, the special structure makes the system nonlinear and strongly coupled even after Park transformation and involves a larger torque ripple. Previous research mainly focused on model-based control for this machine, which is very sensitive to the parameters. Thus, to control the complex systems stably and accurately, two model-free control algorithms, Active Disturbance Rejection-Based Iterative Learning Control (ADRILC) and Active Disturbance Rejection Control–Iterative Learning Control (ADRC–ILC), are proposed for the current and speed control loops of a DSPMG-based Tidal Stream Turbine (TST), respectively. ADRC–ILC uses ADRC to deal with the external non-periodic speed ripple and adopts ILC to reduce the internal periodic speed ripple. ADRILC employs an iterative method to improve the ESO for the enhancement of the convergence rate of ILC. Considering the variable tidal speed, when the speed is above the rated value, Maximum Power Point Tracking (MPPT) must be changed to a power limitation strategy for limiting the generator power to the rated value and extending the system operating range. Thus, Optimal Tip Speed Ratio (OTSR)-based MPPT (for a low tidal current speed) and Leading Angle Flux-Weakening Control (LAFWC) (for a high tidal current speed) strategies are also proposed. According to the simulation results, the proposed ADRC–ILC + ADRILC has the lowest torque ripple, the highest control accuracy, as well as a good current tracking capability and strong robustness. At the rated speed, the proposed method reduces the torque ripple by more than 20% and the speed error by about 80% compared with PI control: the current difference is limited in 2A. The LAFWC proposed for an excessive tidal current speed is effective in conserving the electromagnetic power and increasing the generator speed.

PMSM의 고속 운전 제어 을 위한 증분형 제어기의 적용 검증

In this paper, applies an incremental controller for high speed operation control in permanent magnet synchronous motors. Speed control performance using voltage-based flux-weakening control is not affected by motor parameters, so it is used in various motors for high-speed operation. In this paper, an incremental controller is applied to voltage-based flux-weakening control to reduce feedback errors. The incremental controller can reduce speed overshoot and ripple when applications with relatively constant acceleration. As a result of applying the incremental controller to the voltage-based flux-weakening control, the overshoot of the motor speed could be reduced, and the motor speed error could be minimized by reducing the difference between the actual motor acceleration and the target acceleration. It is considered that this method can be applied to devices with little change in acceleration to increase the effect of motor control.

Investigation of Brushless Doubly-Fed Dual-Stator Machines for Traction Applications

Two brushless doubly-fed dual-stator machines with different inner-stator field windings, namely AC and DC field windings, are proposed and investigated. It is shown the proposed machine with AC field windings exhibits advantages of higher torque density and wider flux-regulation range compared with its DC field winding counterpart. Unlike conventional doubly-fed hybrid-excited machines, the proposed machine consists of AC field windings and hence resulting in more flexible field current control. Its armature and field windings are separately placed in two stators, which can alleviate the space competition between the field and armature slots, as well as significantly enhance the space utilization. Consequently, both flux-regulation capability and torque density can be effectively improved. The topology, operating principle, and mathematical model of the proposed machines are introduced. Then, a sectored flux-weakening control method is proposed and elaborated. Based on finite element method (FEM), the main electromagnetic performances of the proposed machines are comprehensively evaluated. The FEM results manifest the proposed machine with AC field windings shows greatly improved flux-regulation range, higher torque and output power under the proposed sectored flux-weakening method over the whole speed range. Finally, prototype machine of the proposed machine is fabricated, and experimental verifications are performed to validate the feasibility of the proposed machines.

Flux Weakening Controller Design for Series-Winding Three-Phase PMSM Drive Systems

Series-winding three-phase PMSMs have a higher bus voltage utilization than the conventional three-phase PMSMs with star connection. This topology is suitable for applications with a limited bus voltage. However, the zero-sequence current controller will reduce the bus voltage utilization of the series-winding PMSMs, which causes problems in the flux-weakening controller design. The conventional flux-weakening control algorithms will cause the series-winding PMSMs to enter the overmodulation region early and degrade the performance of the zero-sequence current suppression algorithm. In this paper, a new flux-weakening controller with a dynamic fundamental voltage limit (FW-DFVL) is designed for the series-winding three-phase PMSM traction system. Firstly, the space vector modulation method combines the proposed virtual zero-sequence vectors to realize both the fundamental current generation and the zero-sequence current suppression. The accurate bus voltage utilization in the fundamental current subspace can be derived from the proposed modulation method. Secondly, the gradient descent method generates the flux-weakening d-axis reference current with the dynamic fundamental voltage, which will converge faster than the conventional PI-based flux-weakening control scheme. Thirdly, the flux-weakening controller in the overmodulation region is also designed where the zero-sequence current will no longer be suppressed. The bus voltage utilization is Vdc in this operation mode. Finally, both the simulation and experimental results are utilized to verify the effectiveness of the proposed FW-DFVL, where faster dynamic performance and higher bus utilization are observed.

Design and Implementation of Predictive Controllers for a 36-Slot 12-Pole Outer-Rotor SPMSM/SPMSG System with Energy Recovery

This paper investigates a drive system with energy recovery which uses a 3-phase 1-kW 36-slot 12-pole distributed winding outer-rotor surface-mounted permanent-magnet synchronous motor (SPMSM) and surface-mounted permanent-magnet synchronous generator (SPMSG), which can be used in indoor exercise bicycles. In order to extend drive system operating speed range, the constant torque control, flux-weakening control, and maximum torque/voltage control are used to extend its operation speed up to 1.75 times rated speed. In addition, a predictive speed controller and a predictive current controller are proposed to improve transient responses, load disturbance responses, and tracking responses. A digital signal processor, type TMS-320F-28035, manufactured by Texas Instruments, is used as a control center for the proposed SPMSM/SPMSG drive system. Experimental results validate the feasibility and correctness of the proposed methods.

Flux-Weakening Controller Design of Dual Three-Phase PMSM Drive System With Copper Loss Minimization

The performance of flux-weakening controllers in the multiphase permanent magnets (PM) machines depends on the accurate fundamental voltage limit derivation, and the minimal copper loss design in the flux-weakening operation region has not been well discussed. In this article, the accurate fundamental voltage limit with considering harmonic current suppression is derived at first. Then, two control concepts are addressed, and the corresponding flux-weakening control strategies are designed with the gradient descent method. In the first control strategy, both the fundamental and harmonic voltage vectors are feasible, resulting in the larger amplitude of the phase currents. The second control strategy obtains higher bus voltage utilization by an additional transition stage. At the same time, the harmonic currents cannot be further suppressed in the flux-weakening operation region. Third, the copper loss per electrical cycle is calculated, and a switching scheme is designed to obtain lower copper loss in the flux-weakening operation region. Finally, both strategies are successfully implemented in a dual three-phase PMSM. Moreover, the proposed switching scheme obtains minimal copper loss in the whole flux-weakening operation region.

Online Adaptive Current Vector Adjustment for Deep Flux-Weakening Control of IPMSM

This article presents a novel online adaptive and accurate deep flux-weakening (FW) control for interior permanent magnet synchronous machine (IPMSM) drives. Based on the fundamental equations of IPMSM, the proposed online current vector adjustment in conjunction with the adaptive torque angle control loop contributes to improving model-based existing literature in two aspects. First, current vector control is constructed on the proposed flexible current vector recognition algorithm, which can be applied for motoring and generating modes. The optimum reference current vector for the FW region is analytically obtained using electrical speed as a feedback signal instead of using voltage feedback. Second, the proposed adaptive gain for the torque angle control loop is obtained using the small-signal approach to overcome the nonlinear effects in deep FW and improve dynamic performance. The effect of adaptive gain is compared using a bode diagram and an experimental test. Also, the stability of the proposed control scheme under parameter variations is maintained and shown by numerical and experimental analyses. The running of the IPMSM with the proposed control provides a smooth transition between regions, including maximum torque per ampere, FW, and deep FW applicable for EVs application. The experimental results confirm the performance of the proposed control strategy.

Analysis and Comparison of Permanent Magnet Synchronous Motors According to Rotor Type under the Same Design Specifications

A surface-mounted permanent magnet synchronous motor (SPMSM) is an electric motor with a simple magnetic circuit design, fast responsiveness, linear torque–current characteristics, speed–voltage characteristics, and constant operating speed. SPMSMs use only magnetic torque; however, interior PMSMs (IPMSMs) have high power densities because they can use reluctance torque. In addition, when flux-weakening control is used, the operating range is wide compared with the SPMSM. This study presents a comparative analysis of the characteristics of SPMSM and bar-type IPMSM. Characteristic analyses are performed by setting the same stator shape, rated speed, number of turns, winding specifications, voltage limit, and magnet usage in a pole/slot combination of six poles and 27 slots. Next, we compare the no-load back electromotive force, cogging torque, and loss characteristics, and perform a characteristic analysis of each model while satisfying the design specifications. No-load and load tests are performed using a back-to-back system. The results of the analysis and experimental results are in good agreement, and the reliability of the analysis results is guaranteed. The SPMSM is approximately 8.5% superior to the IPMSM in terms of core loss, and the eddy current loss is greater than that of the IPMSM.

Active Disturbance Rejection Control Based on Deep Reinforcement Learning of PMSM for More Electric Aircraft

In this article, an active disturbance rejection controller (ADRC) based on deep reinforcement learning (DRL) algorithm is proposed to be used in the flux weakening control (FWC) system of motors for more electric aircraft. Artificial intelligence algorithm is introduced into ADRC motor control system for the first time, and DRL is designed as the automatic tuning for the parameters optimization of ADRC. The interface module scheme is proposed to realize the conversion between the relevant quantities of the control system and the DRL Agent according to the characteristics of ADRC. The parameters are optimized in the form of parameter modification, and a new DRL-ADRC control framework is proposed which can avoid being trapped into local optimum. The ADRC model designed for the speed loop of FWC system are first introduced. An interface module is subsequently built to enable DRL to interact with the FWC system automatically. DRL agent is trained to optimize the internal parameters of ADRC, which have the characteristics of large quantities, weak sensitivity and strong coupling. Deep deterministic policy gradient is used as the strategy of DRL, which can quickly determine the descent gradient and converge the multiobjective optimization problem. Simulation and comparison with classical heuristic algorithms and disturbance rejection methods are carried out to show the superiority of DRL. The feasibility and effectiveness of the proposed control method are verified by experiments on an aerospace motor for MEA.

The Non-Singular Fast Terminal Sliding Mode Control of Interior Permanent Magnet Synchronous Motor Based on Deep Flux Weakening Switching Point Tracking

This paper presents a novel non-singular fast terminal sliding mode control (NFTSMC) based on the deep flux weakening switching point tracking method in order to improve the control performance of permanent interior magnet synchronous motor (IPMSM) drive systems. The mathematical model of flux weakening (FW) control is established, and the deep flux weakening switching point is calculated accurately by analyzing the relationship between the torque curve and voltage decline curve. Next, a second-order NFTSMC is designed for the speed loop controller to ensure that the system converges to the equilibrium state in finite time. Then, an extended sliding mode disturbance observer (ESMDO) is designed to estimate the uncertainty of the system. Finally, compared with both the PI control and sliding mode control (SMC) by simulations and experiments with different working conditions, the method proposed has the merits of accelerating convergence, improving steady-state accuracy, and minimizing the current and torque pulsation.

Review of Flux-Weakening Algorithms to Extend the Speed Range in Electric Vehicle Applications With Permanent Magnet Synchronous Machines

This article reviews Flux-Weakening (FW) algorithms for Permanent Magnet Synchronous Machines (PMSMs), focusing on the automotive sector, especially in electric and hybrid electric vehicles. In the past few years, the spread of Electric Vehicles (EVs) has improved the technology of electric machines and their control to achieve more compact and competitive solutions. PMSMs are the most widespread electric machines used in EVs thanks to their high-power density and potential operation at constant power range during high speed. Such high speed implies a high electromotive force. An FW technique is mandatory to reduce the electromagnetic flux generated by the electric machine due to the voltage limits of the traction inverter and the energy source. This article classifies and analyses the state-of-the-art FW control strategies by comparing their main advantages and drawbacks. The Vector Current Control (VCC) method that regulates the modulus of the applied voltage is the most common one in the literature thanks to i) its robustness to parameter modification and model unsureness, ii) low computational complexity, and iii) high dynamic response and control stability.

Research on Direct Drive Technology of the Permanent Magnet Synchronous Motor for Urban Rail Vehicles

Compared with the traditional gear reduction mechanism of the asynchronous motor, the permanent magnet synchronous motor (PMSM) direct drive technology has obvious advantages and has attracted increasing attention. We analyzed the advantages of the PMSM direct drive technology and put forward the hollow shaft structure of the coupling to reduce the impact force of the wheel and rail, additional noise, vibration, and loss. We deeply studied the topology and mathematical model of the PMSM. To keep the maximum running speed unchanged, it is necessary to conduct a flux weakening control above the rated speed to increase the speed regulation range of the PMSM. To prevent frequent switching jitter at the transition point and smooth the transition between different weak magnetic fields, we designed a new flux-weakening controller to control the current. Simulation results have been presented to verify the proposed approach efficiency. Taking the PMSM system train on Suzhou Metro line 3 as an example, the on-site energy consumption test was carried out. The energy consumption of the PMSM direct drive and asynchronous motor gear mechanism was compared. The energy consumption of the PMSM direct drive is increased by 16.50%. The flexible plate coupling can alleviate the adverse effects of vibration and improve the reliability of train operation. Finally, we put forward the technical difficulties and challenges of the PMSM direct drive technology. We need to optimize the mass distribution of the direct drive bogie to improve the dynamic performance of the bogie, the heat dissipation conditions, and the accurate control of the PMSM. It will have reference value for the development of the PMSM direct drive in the future.