Online Adaptive Maximum Torque Per Ampere Control for Doubly Salient Electromagnetic Machine

In this paper, a linear torque control strategy is first proposed for interior permanent magnet synchronous motor drives to fully utilize the reluctance torque and simplify the controller design. The proposed linear torque control strategy also extends the existing maximum torque per ampere control in the constant torque limit region up to the entire field-weakening region. It is found that in an intermediate speed region, called partial field-weakening region, the existing maximum torque per ampere control can still be applied under lighter load condition. In addition, the proposed control can also achieve the objective of minimum copper loss (i.e., maximum torque per ampere) for the entire speed range. Sound theoretical basis is given in the context. Moreover, an adaptive limiter is proposed for efficiently implementing the proposed control strategy over the entire speed range. Finally, a prototype is also constructed by using a fixed-point DSP TMS320F240 and some experimental results are given to verify the validity of the proposed control strategy.

For the dual three-phase interior permanent magnet synchronous machines (DT-IPMSMs), open-phase fault can cause current unbalance and degrade the drive performance. This article proposes a fault tolerant maximum torque per ampere (FT-MTPA) control for DT-IPMSMs, which can maximize the ratio of the average torque to the stator current and minimize the fault-induced torque ripple. In the proposed approach, optimal FT-MTPA solution is derived and theoretically proven, and current rms is considered as one design constraint to ensure the equivalent loss to the healthy condition. The proposed FT-MTPA control ensures the smooth switching between fault tolerant control and healthy control without inducing noticeable torque ripple. Compared with existing methods, the proposed approach is computation-efficient and fast in achieving the FT-MTPA control, which is critical to practical applications with fast changing loads. Moreover, this article derives the optimal solution from the faulty MTPA model with fault induced terms considered to ensure high torque. Experiments and comparisons with existing methods are conducted to evaluate the proposed approach on a laboratory DT-IPMSM.

In this paper, a comprehensive and practical method of implementing speed range extended maximum torque per ampere (MTPA) control for permanent magnet synchronous machine (PMSM) is presented. The inverter-based method of measuring PMSM parameters, including winding resistance and d- and q- axis flux linkages, is introduced. The nonlinearities of the inverter, including voltage amplitude error and voltage phase shift, are identified and compensated, which improves the accuracy of the characterized flux linkage. The extended MTPA current references are obtained by employing nonlinear optimization algorithm, and the results are verified analytically on the current plane. MTPA control is applied on the PMSM experimentally in the entire speed range. Current transition, torque control accuracy, and efficiency performance are measured in the entire torque–speed range.

Maximum Torque Per Ampere (MTPA) control makes full use of the Interior Permanent Magnet Synchronous Motor(IPMSM), and the current is minimized under the same torque, so that the energy consumption is minimized. In this paper, the formula method is used to directly calculate the current operating point. The direct calculation method relies on motor parameters, In order to solve this problem, this paper combines the least squares one-time algorithm and the recursive algorithm, and adopts the least-squares limited memory method to identify these parameters. So that The current amplitude of the motor is always kept to a minimum.

To improve the fault-tolerant operation ability of the doubly salient electro-magnetic machine (DSEM) in case of loss-of-excitation, the turns of DSEM winding are designed accordingly. However, the increase of armature winding self-inductance causes the current to rise slowly during commutation, which affects the torque output. In addition, the temperature distribution of the fault-tolerant DSEM will change greatly during normal and fault-tolerant operation. Considering these problems, a comparative analysis is performed on the DSEM to examine the dynamic response of the phase current during the commutation process based on different converters, including the bridge converter and asymmetric half-bridge converter. The field-circuit joint simulation model is built to analyze the performance under normal/fault-tolerant operation. The temperature field model is established to analyze the temperature field of the loss-of-excitation fault-tolerant DSEM under different operating modes. Finally, a prototype is made and tested. The results indicate that the half-cycle control strategy is worth reconsidering. This strategy not only can effectively suppress the torque ripple of fault-tolerant DSEM, but also does not need to change the control strategy of normal and demagnetized fault-tolerant operation. In addition, the copper loss and temperature rise of the motor winding are reduced in this strategy.

매입형 영구자석 동기 전동기는 높은 효율과 빠른 동특성, 넓은 정출력 운전 영역 등의 장점 때문에 다양한 산업 분야에서 각광을 받고 있다. 특히 매입형 영구자석 동기기의 단위 전류당 최대 토크(Maximum Torque Per Ampere, MTPA) 운전 방법은 전동기의 최대 효율 운전을 위해서 필수적인 운전방법이 되었다. 이론적인 MTPA 운전점은 전동기의 제 정수에 의해 결정되는데, 매입형 영구자석 동기 전동기는 온도와 운전 영역에 따라 전동기 제 정수의 변화가 심하여 정확한 MTPA 운전을 하기 위해서는 전동기의 전 운전 영역에 대한 전동기 제 정수를 미리 알고 있어야 한다. 본 논문에서는 신호 주입 개념을 도입한 새로운 MTPA 운전 방법을 제안한다. 전류에 높은 주파수의 신호를 주입하여 그 주입된 신호에 의한 반응을 확인함으로 MTPA 운전점을 판별하게 된다. 이 방법은 전동기 제 정수 변동에 강인하며, 간단한 신호처리 과정을 통하여 MTPA 운전을 할 수 있다. Interior Permanent Magnet Synchronous Motor(IPMSM) have gained an increasing popularity in recent years for a variety of industrial applications, because of their high power density, high efficiency and possibility of flux weakening operation. Because the efficiency of IPMSM is one of the important performance characteristic, the Maximum Torque Per Ampere(MTPA) operating method has been indispensible. In theory, MTPA operating point can be calculated using the exact values of the machine parameters. However, the values of the IPMSM parameters are known to vary widely according to the operating condition. Therefore, to operate the IPMSM in the MTPA operating point, the machine parameters should be estimated in real-time. In this paper, the new MTPA operating method based on the signal injection is presented. By injecting the high frequency current signal, the MTPA operating criteria can be calculated by measuring the input power to IPMSM. The proposed method can find the MTPA operating point with simple signal processing regardless of the parameter variation.

The winding of the motor stator coil can be faulted due to high voltage, high temperature stress and etc. In the ITF (Inter Turn Fault) winding, large fault current, ohmic loss, and excessive winding heat are induced. As a result, fault aggravation and machine burning might happen unless adequate fault diagnosis and management are equipped. By limiting the copper loss by the ITF, the faulted motor could operate without aggravation till the adequate fault management action is performed. In this paper, an IPMSM (Interior Permanent Magnet Synchronous Motor) ITF tolerant drive method by limiting internal copper loss is proposed. The copper loss by the ITF is made simple for the proposed method and analyzed with various current, speed, and output torque condition. By maximizing the output torque with minimum IPMSM copper losses, MTPL (Maximum Torque Per Loss) operation point is suggested. Compared with the MTPA (Maximum Torque Per Ampere) the MTPL is more efficient operation point with ITF. To verify the proposed method, experiment studies are performed with an IPMSM with an ITF. The results show the feasibility and practicality of the proposed method.

The paper studies the impact of first and third current-harmonic repartition in a five-phase Permanent Magnet machine whose Electromotive Forces (emfs) have first and third harmonics of the same amplitude. With a five-phase machine, it is possible for the torque production to achieve independent controls of the first and third harmonics of currents by using a vector control in each one of the two characteristic orthogonal sub-spaces of the machine. The same torque quality as obtained with a three-phase machine with sinusoidal emf can be thus obtained with a non-sinusoidal emf and with one more supplementary degree of freedom for the control. Based on the Maximum Torque Per Ampere (MTPA) strategy used for three-phase machines, a comparison of the obtained torque/speed characteristics of the machine is achieved using either one or two harmonics. The voltage limits imposed by the Voltage Source Inverter and two different values of the maximum allowed current densities are taken into account for obtaining the optimum repartition between first and third harmonics of currents: it appears that at first, from the point of view of efficiency, the MTPA is not optimal except for low speeds and secondly that the repartition of currents is not trivial and depends for example on the considered maximum current densities.

Maximum Torque Per Voltage trajectory has been utilized only during field weakening operation of Interior Permanent Magnet (IPM) motor. In this paper, the voltage minimization control from zero-speed is proposed. Voltage minimization results in maximum torque per voltage control of IPM motor. The control implementation is also simple in comparison to current minimization, as the operation is always along the current-limit locus irrespective of operation in field-weakening. Voltage minimization technique minimizes the core losses whereas current minimization would minimize the copper losses. The mathematical model of IPM motor following voltage minimization is derived and the solution to the 4th order quartic equations is obtained using Ferrari’s method. The solution obtained is utilized to develop a look-up table for vector control of IPM motor. A comparative analysis of voltage minimization and current minimization is established which is supported by simulation results and demonstrated by detailed experimental results.

In this paper, a modified control strategy of Finite-Control-Set Model Predictive Control (FCS-MPC) for the Interior Permanent Magnet Synchronous Motor (IPMSM) is proposed to solve the problem that the actual stator current cannot quickly track the given Maximum Torque Per Ampere (MTPA) current due to the integration saturation of the current regulator caused by sudden changes in load torque. The FCS-MPC controller is used to replace the PI current regulator, to obtain a more accurate voltage vector and achieve real-time dynamic tracking of the IPMSM MTPA target trajectory. The cost function of FCS-MPC control strategy is designed multi-objective combination to meet such requirements: torque tracking, MTPA current tracking and limitation of the maximum current. The simulation and experimental results show that the proposed control strategy can track the MTPA given current and torque in real time during load torque sudden changes.

This paper presents the experimental implementation of Maximum Torque per Ampere (MTPA) control for an Interior Permanent Magnet Synchronous Motor (IPMSM) developed indigenously, where knowledge of motor parameters was initially lacking. The paper discusses the resolution of various challenges encountered in IPMSM speed control. These challenges include limitations imposed by high direct axis inductance ($\mathrm{L}_{\mathrm{ds}}$) and quadrature axis inductance ($\mathrm{L}_{\mathrm{q}}$) on per phase stator voltage, which restrict the motor’s speed and loading capacity below levels specified by the manufacturer. Additionally, the paper addresses issues related to motor starting and the intricate implementation of the MTPA algorithm in a DSP microprocessor. The strategies adopted to overcome these challenges are discussed, and experimental results are provided to illustrate the efficacy of the implemented MTPA control strategy.

Excitation fault is troublesome because it takes a negative impact on the overall performance of the doubly salient electromagnetic machine (DSEM).The output torque of DSEM is only the reluctance torque when it operates in the state of loss of excitation. In order to make the motor operate normally in the state of loss of excitation, the motor parameters should be designed to meet the operation characteristics of DSEM and SRM in the state of loss of excitation as much as possible.In this paper, the main structure factors that affect the normal operation of DSEM in the state of loss of excitation were analyzed. A 12 / 8-pole finite element analysis model of DSEM is established.The different stator pole, stator yoke, rotor pole, rotor yoke and air gap of the motor were simulated. The influence of the structural parameter changes on the electrical and magnetic characteristics of the motor was studied.The number of turns of DSEM winding suitable for loss of excitation fault-tolerant operation was designed and simulated.

In this paper, the possibility of designing a five-phase Surface-mounted Permanent Magnet (SPM) machine with 20 slots and 8 poles for a low power marine propulsion system is examined. Due to its particular winding and surface magnet design, the machine inherently offers an electronic pole changing effect from 3×4 pole pairs at low speed to 4 pole pairs at high speed. At high speed, in the constant power range, according to Finite Element Analysis, the Maximum Torque Per Ampere strategy appears not to be the right solution to minimize the whole machine losses (copper, iron and magnets). In particular, a strategy that favors the 4-pole rotating field at high speed allows to mitigate the magnet losses, thus limiting the risk of magnet overheating.

This manuscript presents an innovative control strategy for the Hybrid Excitation Permanent Magnet Synchronous Motor (HEPMSM) designed for electric vehicle (EV) applications. The strategy combines Maximum Torque Point Tracking (MTPT) and Maximum Torque Per Ampere (MTPA) techniques to track the ideal torque-speed profile, ensuring maximum torque at low speeds for starting and climbing, and high power at higher speeds for cruising. A novel unidirectional excitation current method is proposed to replace traditional bidirectional field current control, eliminating the risk of permanent magnet demagnetization, reducing copper losses, and increasing efficiency. This approach extends the constant power (CP) region by a 4.2:1 ratio. The manuscript also introduces a detailed mathematical model, considering both iron core losses and their impact on the EV profile. Additionally, the Multi-Objective Ant Lion Optimizer (MOALO) algorithm is used in two stages: first to optimize the hybridization ratio (HR) and base speed (Nb), and second to analyze the effect of varying the hybridization ratio while maintaining constrained output power. The proposed strategy is validated through MATLAB simulations, demonstrating its effectiveness in achieving high acceleration, efficiency, and reliability for EV applications.

Interior permanent magnet synchronous machines (IPMSM) are preferably used for traction drives in electric vehicles. These are characterized by high efficiency and high torque as well as power density. The generation of reference currents for the field-oriented control is realized by look up tables (LUT). In these LUT the entire machine characteristic is described. The reference currents are selected on the basis of different operating strategies. The Maximum Torque Per Current (MTPC) method, which minimizes the magnitude of the current at a given torque, is the most common strategy in the constant torque range. It can be proven by measurements on a real motor that the MTPC method deviates considerably from the best efficiency under certain boundary conditions. The use of the Maximum Efficiency (ME) method increases the drive efficiency in comparison to the MTPC up to 0.3% at the same torque level. The ME characteristic however, has to be changed with the machine speed. Using the ME method, the gain of efficiency is small but it can be achieved with minor adaptions of a LUT in the machine control.