A Linear Maximum Torque Per Ampere Control for IPMSM Drives Over Full-Speed Range

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.

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.

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.

In this paper, an experimental investigation on the comparison between the Maximum Torque Per Ampere (MTPA) and the Field Orientation Control (FOC) algorithms for interior permanent magnet synchronous machines (IPMSMs) is described, analyzed and discussed. This investigation was carried out on a small-power IPMSM with low saliency ratio. More in detail, after a previous simulation study, the control techniques have been experimentally implemented and validated through means of a dSPACE® rapid prototyping system. The performances of the two algorithms have been evaluated and compared, obtaining interesting results.

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.

Advanced angle control (AAC) is an effective approach to improve the output torque performance of doubly salient electromagnetic machine (DSEM). But the optimal advanced angle varies with multiple time-changing parameters, such as motor speed, load torque, phase resistances, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">etc</i> ., bringing difficulty to obtain the online optimal AAC. To deal with this problem, this paper proposes an online adaptive maximum torque per ampere control strategy for DSEM. The commutation process is analyzed in detail, and the quantitative expression of optimal angle is obtained. Then, based on the convex characteristic between the advanced angle and DC bus current, an online gradient searching method for the optimal advanced angle is put forward by utilizing the DC bus current as the feedback, no motor parameters are pre-required. Afterwards, based on the analysis of the tradeoff between the searching accuracy and speed, the designing rules for control parameters are obtained. What's more, the feature of DC bus current ripple is explored, and an average DC bus current sampling method is put forward for easier implementation of the proposed searching method. Finally, the experiments on a 12/8-pole DSEM verify the correctness and feasibility of the proposed strategy under multiple operating conditions.

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.

Deep Flux-Weakening Strategy with MTPV for High-Speed IPMSM for Vehicle Application

High-efficiency electric drive systems claim not only optimally designed electric machines but also efficiency-oriented control strategies. Taking machines and drives into synergetic consideration, this paper proposes a fresh particle crowd optimisation (FPCO) of efficiency-oriented control algorithm named maximum outer torque per ampere (MOPA) control and maximum efficiency per ampere (MEPA) control, aiming to maximise the efficiency of interior permanent magnet synchronous machines during operation. Difference from conventional id = 0 or maximum torque per ampere control, MOPA and MEPA fully consider the cross effect core loss, iron loss, supplementary loss and mechanical loss, from which the full-order loss model of interior permanent magnet synchronous motor (IPMSM) is built. In order to identify the accuracy of the efficiency-oriented control algorithm, the efficiency-oriented controlled system on based FPCO using non-singular terminal sliding (NTS) controller is built, on the base of this, the stabilisation of the current trajectory and the voltage vector from simulation and testing are inspected. After that, the higher effectiveness of MOPA and MEPA is proved through the operation experiment of IPMSM of which capacity is 82 kW.

In this paper, the drawbacks of the conventional f-t frame based maximum torque per ampere (MTPA) control schemes are analyzed and mathematically proved. In order to inherit the merits of both the direct flux vector control (DFVC) in field weakening region and field orientated control (FOC) in constant torque region while avoiding their disadvantages, an integrated control scheme is proposed. The proposed control scheme integrates the FOC into f-t reference frame at low speeds to achieve a relatively accurate and robust MTPA control, while at high speeds, the DFVC is adopted to utilize the advantages of f-t frame based control scheme in field weakening region. A shape function is utilized by the proposed control scheme to achieve a smooth transition between the two control schemes. The proposed control scheme is verified by experiments under various operation conditions on a prototype IPMSM drive. The simulation and experimental results illustrate that the proposed control scheme could achieve a better MTPA control accuracy in constant torque region and a better field weakening performance in the constant power region. Meanwhile the complex look-up tables for FOC in field weakening region and the difficulties in observing flux vector at low speed are avoided.

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.