This article discusses the maximum torque per ampere (MTPA) control of synchronous motors, which have become an indispensable part of highly efficient motor drives. It explains the nature of torque produced by synchronous motors, ways to find its maximum and algorithms to operate at this point, despite changes of loads and motor parameter variations. The authors propose a classification of the MTPA methods, based on the features of each algorithm or group of similar methods. They demonstrate the conventional control scheme and discuss the modifications necessary for the implementation of each method. This article reviews existing MTPA control algorithms, discusses their pros and cons, and suggests possible areas of usage for each group of methods. The authors of the article share their vast experience in the industry and research aspects, which were obtained by developing industrial, commercial, traction, and military drives, and report on their views on the perspective of each method taken into consideration. 

Review and Classification of MTPA Control Algorithms for Synchronous Motors

The use of position sensors for the variable frequency drive (VFD) has been verified for years. However, more reliable VFDs with smart autonomous systems require side-by-side implementation of sensor and/or sensorless operation. Recently developed active disturbance rejection control (ADRC) provides robustness to VFD uncertainty and its fast response to reject disturbances. Considering the iron loss effect as the disturbance to the permanent magnet brushless dc motor (PMBLDCM) performances, a novel ADRC is proposed in this article. The ADRC current controller considering the iron loss effect is proposed along with an estimation of the back electromagnetic force disturbance used for the position/speed estimation. The proposed controller incorporates a structured inner and outer closed-loop ADRC that considers process delays and extended state observer dynamics. These dual ADRC-based control algorithms are verified for PMBLDCM drive both by simulation study and experimental findings. The improved performance of the proposed method is validated with a laboratory prototype of 2.5 kW PMBLDCM drive system.

An Enhanced Linear Active Disturbance Rejection Controller for High Performance PMBLDCM Drive Considering Iron Loss

In this article, a high-performance maximum torque per Ampere (MTPA) control strategy is proposed for surface-mounted brushless dc (BLDC) motor drive. Most of published works in the literature have not considered the effect of iron loss branch. As will be demonstrated analytically, underestimating the iron loss in the control system of BLDC motor has two undesirable effects. First, it causes torque errors. Second, the MTPA fails to track the true minimum current for a desired torque. Therefore, the control system should compensate the effect of iron loss. This compensation is proposed to achieve by a direct torque control scheme to prevent internal current loops and feedforward compensations. In addition, the Lagrange's theorem is employed to derive an MTPA criterion. It is proven that forcing the criterion to zero guarantees realization of MTPA strategy. In order to reach these control objectives, a nonlinear control method is designed with two new output, corresponding to electromagnetic torque and the MTPA criterion. Performance of the proposed controller in realization of MTPA and minimization of torque ripple is justified in real-time through simulations and experiments on a 200 W outer rotor prototype.

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MTPA Strategy for Direct Torque Control of Brushless DC Motor Drive

Brushless direct current (BLDC) motors are mostly preferred for dynamic applications such as automotive industries, pumping industries, and rolling industries. It is predicted that by 2030, BLDC motors will become mainstream of power transmission in industries replacing traditional induction motors. Though the BLDC motors are gaining interest in industrial and commercial applications, the future of BLDC motors faces indispensable concerns and open research challenges. Considering the case of reliability and durability, the BLDC motor fails to yield improved fault tolerance capability, reduced electromagnetic interference, reduced acoustic noise, reduced flux ripple, and reduced torque ripple. To address these issues, closed-loop vector control is a promising methodology for BLDC motors. In the literature survey of the past five years, limited surveys were conducted on BLDC motor controllers and designing. Moreover, vital problems such as comparison between existing vector control schemes, fault tolerance control improvement, reduction in electromagnetic interference in BLDC motor controller, and other issues are not addressed. This encourages the author in conducting this survey of addressing the critical challenges of BLDC motors. Furthermore, comprehensive study on various advanced controls of BLDC motors such as fault tolerance control, Electromagnetic interference reduction, field orientation control (FOC), direct torque control (DTC), current shaping, input voltage control, intelligent control, drive-inverter topology, and its principle of operation in reducing torque ripples are discussed in detail. This paper also discusses BLDC motor history, types of BLDC motor, BLDC motor structure, Mathematical modeling of BLDC and BLDC motor standards for various applications. 

/pdf/a-review-of-bldc-motor-state-of-art-advanced-control-mx7gunkv.pdf

A Review of BLDC Motor: State of Art, Advanced Control Techniques, and Applications

Brushless direct current (BLDC) motors are mostly preferred for dynamic applications such as automotive industries, pumping industries, and rolling industries. It is predicted that by 2030, BLDC motors will become mainstream of power transmission in industries replacing traditional induction motors. Though the BLDC motors are gaining interest in industrial and commercial applications, the future of BLDC motors faces indispensable concerns and open research challenges. Considering the case of reliability and durability, the BLDC motor fails to yield improved fault tolerance capability, reduced electromagnetic interference, reduced acoustic noise, reduced flux ripple, and reduced torque ripple. To address these issues, closed-loop vector control is a promising methodology for BLDC motors. In the literature survey of the past five years, limited surveys were conducted on BLDC motor controllers and designing. Moreover, vital problems such as comparison between existing vector control schemes, fault tolerance control improvement, reduction in electromagnetic interference in BLDC motor controller, and other issues are not addressed. This encourages the author in conducting this survey of addressing the critical challenges of BLDC motors. Furthermore, comprehensive study on various advanced controls of BLDC motors such as fault tolerance control, Electromagnetic interference reduction, field orientation control (FOC), direct torque control (DTC), current shaping, input voltage control, intelligent control, drive-inverter topology, and its principle of operation in reducing torque ripples are discussed in detail. This paper also discusses BLDC motor history, types of BLDC motor, BLDC motor structure, Mathematical modeling of BLDC and BLDC motor standards for various applications.

https://ieeexplore.ieee.org/ielx7/6287639/6514899/09774372.pdf

Among the conventional loss minimisation algorithms (LMAs), the model-based approaches have the advantages of fast response and high accuracy. Here, a novel online model-based power losses minimisation approach is presented for indirect field-oriented control (IFOC) of induction motor (IM) drives. The proposed method is introduced as maximum torque per power losses (MTPPL) in which the power losses for a given torque are minimised. The results demonstrate that the proposed approach preserves the LMA merits, while the criterion for the MTPPL scheme is achieved. The mentioned criterion is investigated by a gradient approach so that while the gradient vectors of the torque and power losses are parallel, the MTPPL strategy is realised. The closed-loop IFOC of the MTPPL approach is implemented in real time for a laboratory 2.2 kW three-phase IM drive. The experimental results show the capability and validity of the proposed control scheme.

/pdf/online-maximum-torque-per-power-losses-strategy-for-indirect-2y0kynet1v.pdf

Online maximum torque per power losses strategy for indirect rotor flux-oriented control-based induction motor drives

This study presents a novel online, accurate and simple model-based maximum torque per ampere (MTPA) strategy for input–output feedback linearisation control of induction motor (IM) drives. Despite conventional MTPA control principles which are under the assumption of iron loss neglecting, the proposed strategy takes iron loss effect into account. This study highlights the iron loss influence on MTPA scheme. Firstly, the cross-coupling effects in the IM model and torque non-linearity due to the iron loss in torque–speed characteristics of the IM are discussed. The criterion for the MTPA scheme is then introduced and investigated by gradient approach so that when the gradient vectors of the torque and stator current magnitude are parallel, the MTPA strategy is satisfied. Finally, to confirm the validity of the proposed control scheme, experiments are carried out.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-epa.2019.0400

Online maximum torque per ampere control for induction motor drives considering iron loss using input–output feedback linearisation

This article proposes a nonlinear controller for brushless doubly-fed induction motor (BDFIM) drives on the basis of input–output feedback linearization (IOFL). In the proposed control approach, first, the maximum torque per inverter ampere (MTPIA) control strategy is considered by applying a fifth-order (reduced-order) model of BDFIM. By realizing the MTPIA, the control winding (CW) current magnitude is minimized under the constraint of constant torque. The realization criterion of MTPIA approach is independent of torque level and CW frequency. To fairly share the current between stator windings and minimizing the total current magnitude for a given torque, the MTPIA idea should be extended. Since, the power winding (PW) of BDFIM is not controllable, obtaining this purpose is a challenge. Therefore, to solve this problem, the model-based maximum torque per total ampere (MTPTA) control is introduced for BDFIM drives and the conditions for realizing this strategy are determined. It should be noted that the total amperes refer to the sum of the PW and the CW current magnitudes. In addition, using the fifth-order model of BDFIM, a nonlinear controller is developed based on IOFL technique which is capable to force the deviation from realization criterion of both proposed strategies to zero while the torque is controlled with high accuracy. The overall stability of the proposed controller is proven using the Lyapunov control theory. The validity of the proposed approach is finally verified by simulation and experimental results.

/pdf/online-mtpta-and-mtpia-control-of-brushless-doubly-fed-h60pw2156h.pdf

Online MTPTA and MTPIA Control of Brushless Doubly Fed Induction Motor Drives

Brushless doubly fed induction machine (BDFIM) which is able to operate in both induction mode and synchronous mode, has received increasing attention of researchers, in the last three decades. It could be considered as an emerging competitor for older structures, due to the substantial features such as brushless structure and requiring a fractionally rated frequency converter. The iron loss which constitutes a significant portion of total power losses is higher in BDFIM in contrast with standard induction machine. Even though it is essential to consider the iron loss effect on dynamic behavior of BDFIM, there is still no comprehensive study in the literature. The aim of this paper is to propose a dynamic model of BFIM in general reference frame in which the iron loss is taken into account. This model which is credible for all BDFIM operation modes including synchronous one, facilitates the performance analysis of BDFIM and implementation of the various control techniques. The supplementary simulations and experiments confirm that the proposed model is an appropriate candidate for BDFIM drives. Because of the complex structure of BDFIM, determination of the iron loss isn't straightforward. In this paper, a practical approach is introduced to calculate the iron loss of BDFIM in terms of frequency variations. The experimental data derived from a D132s prototype BDFIM is then compared with the calculated data from the finite element analysis (FEA).

/pdf/modeling-and-dynamic-performance-analysis-of-brushless-4n5dulscql.pdf

Hamidreza Mosaddegh Hesar

Papers

MTPA Strategy for Direct Torque Control of Brushless DC Motor Drive

Online maximum torque per power losses strategy for indirect rotor flux-oriented control-based induction motor drives

Online maximum torque per ampere control for induction motor drives considering iron loss using input–output feedback linearisation

Online MTPTA and MTPIA Control of Brushless Doubly Fed Induction Motor Drives

Modeling and Dynamic Performance Analysis of Brushless Doubly Fed Induction Machine Considering Iron Loss