An Optimized Nonlinear Extended State Observer for Sensorless IPM Synchronous Motor Drives

In sensorless control of interior permanent magnet synchronous motor (IPMSM) drives, extended state observers (ESOs) are preferred due to their advantages, e.g., flexible application, and simple implementation. However, the conventional ESOs may experience the degraded performance with the challenging issues of rapidly changing back electromotive force (BEMF) in a sinusoidal form and ramp disturbances in position estimation. To enhance the position estimation accuracy, this article proposes an estimation scheme based on a novel generalized integrator ESO (NGI-ESO) and an integrally compensated (IC)-third-order (3rd)-linear ESO (IC-3rd-LESO). In the proposed estimation scheme, with the modified mathematical model of the BEMF, the NGI-ESO is designed to achieve accurate estimations of the BEMF. Moreover, the IC-3rd-LESO with a compensation loop is used to mitigate position estimation errors caused by the ramp disturbances. Consequently, the overall performance of sensorless-controlled-IPMSM drives is enhanced. The performance of the proposed estimation scheme under different conditions is verified and compared to that of the conventional ESO schemes by using extensive experimental tests.

A comprehensive comparison of the dynamic and steady state performance characteristics of permanent magnet synchronous motors (PMSM) with interior and surface rotor magnets for line-start operation is presented. The dynamic model equations of the PMSM, with damper windings, are utilized for dynamic studies. Two typical loading scenarios are examined: step and ramp loading. The interior permanent magnet synchronous motor (IPMSM) showed superior asynchronous performance under no load, attaining faster synchronism compared to the surface permanent magnet synchronous motor (SPMSM). With step load of 10 Nm at 2 s the combined effect of the excitation and the reluctance torque forced the IPMSM to pull into synchronism faster than the SPMSM which lacks saliency. The ability of the motors to withstand gradual load increase, in the synchronous mode, was examined using ramp loading starting from zero at 2 s. SPMSM lost synchronism at 12 s under 11 Nm load while the IPMSM sustained synchronism until 41 seconds under 40 Nm load. This clearly suggests that the IPMSM has superior load-withstand capability. The superiority is further buttressed with the steady state torque analysis where airgap torque in IPMSM is enhanced by the reluctance torque within 90° to 180° torque angle.

This paper presents improvements of the stator flux estimation for a variable structure direct torque controlled (DTC) interior permanent magnet (IPM) synchronous motor drive. A variable structure observer is proposed to estimate the stator flux linkage based on the IPM motor current model. Compared to open-loop estimator, the observer improves the performance of the IPM motor drive. The experimental results demonstrate that the proposed observer is able to deliver more accurate estimation than open-loop estimator both in the steady state and during transients. Performance of encoder-less operation at very low speed is enhanced significantly.

This paper presents a sliding mode controller for an interior permanent magnet (IPM) synchronous motor, in which direct torque control (DTC) concept, variable structure control and space vector modulation (SVM) are integrated to achieve high performance. In comparison with conventional DTC, the inverter switching frequency is constant and controllable by using SVM, the torque and flux ripple are significantly reduced. The fast response and robustness merits of DTC are preserved. Position and angular speed of the rotor are obtained through an extended Kalman filter (EKF).

The adoption of Interior Permanent Magnet Synchronous Motors (IPMSM) and Synchronous Reluctance Motors (SynRM) is gaining popularity in many fields, including simple industrial applications, where cost and efficiency are the main aspects. In those applications, sensorless control is usually desired and commissioning should be simple and relatively fast. While specific-purpose drives have been successfully addressed by sensorless drives based on PMSMs and SynRMs, the integration of these techniques in general-purpose drives is still limited and, when available, mostly linked to proprietary techniques. In fact, motor parameters are needed for tuning control parameters or characteristics, which are only partially available from standard nameplates. Moreover, manual setup requires specialized knowledge and can be very time consuming. In order to remove these barriers towards wider adoption of these efficient motors, considerable research effort is being devoted to fully automate the commissioning, i.e. “auto-tuning” of the drive. This paper proposes and analyzes a feasible way to obtain complete self-commissioning of a mid-performance IPMSM or SynRM drive.

The increase of pole numbers of the interior permanent magnet (IPM) synchronous machine can boost its air gap flux density, raise its efficiency and torque, and reduce its volume and weight. With the help of geometry module, this paper analyzes the relation between "flux concentration function" and the pole pair numbers of IPM synchronous machine, discusses connections between pole numbers and air gap flux density, per pole flux, non-load electric potential, flux density of rotor lead magnet material, flux density of stator tooth, flux density of stator yoke, and power which permanent magnet of unit volume produce respectively. Finally, authors point out: (1) when the saturation of lead magnet material was considered, the air gap flux density and the sums of the per pole flux will produce a the maximum with the increase of pole pairs, that is, IPM machine has a suitable pole pairs; (2) IPM machine bears "flux concentration function", when its pole pairs is more than or equal to 3, B/sub /spl delta///B/sub M/>1 or 4, B/sub /spl delta///B/sub r/>1; (3) the pole pairs of the IPM machine, which be from 3 to 6, is suitable. (4) the inner flux density of permanent magnet and power produced by the permanent magnet of unit volume will drop with the increase of pole pairs of the IPM machine.

The dual observation of periodic and aperiodic interferences cannot be balanced by traditional linear extended state observer (T-LESO). Therefore, the speed fluctuations caused by uncertain periodic and aperiodic interferences in the interior permanent magnet synchronous motor control system cannot be suppressed by the traditional linear active disturbance rejection controller. To resolve the aforementioned problem, an improved linear active disturbance rejection controller (I-LADRC) in which multifrequency quasi-resonant filtering decoupling linear extended state observer and generalized linear extended state observer (G-LESO) are cascaded is proposed. In this controller, the interference feedforward control method of T-LESO is first changed, the observer bandwidth <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ω_o</i> and controller bandwidth <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ω_c</i> in the transfer function based on the interference term are decoupled from each other, reducing the difficulty of parameter tuning. On this basis, a multifrequency quasi-resonant filter is embedded in the decoupled linear extended state observer (LESO), so that periodic interferences can be accurately observed. For G-LESO, a fourth-order LESO is adopted to enable more accurate observation of aperiodic high-order interferences. The outer loop controller based on I-LADRC is designed, and the correctness and effectiveness of this method are verified through experiments.

Synchronous homopolar motors (SHMs) with an excitation winding located at the stator and a toothed salient pole rotor are a good alternative to motors traditionally used in traction applications such as induction motors or interior permanent magnet synchronous motors (IPMSM). This study presents the results of a theoretical comparison between an IPMSM and an SHM in a traction application with a constant power speed range of 1:10, which is specific to the mining truck drives, and with a rated power of 370 kW. The considered IPMSM and SHM have the same number of phases, poles and stator slots, and the same outer diameter of the stator lamination. The IPMSM design is optimized using the Nelder–Mead method. The main objectives of optimization are to minimize the average losses in the operating cycle and to limit the required power of the semiconductor inverter. The performance of the optimized IPMSM is compared with the previously obtained performance of the SHM optimized by the same method. Although the average losses in the operating cycle in the compared motors are approximately equal, the losses at high speed for the IPMSM are about two times greater than at low speed with maximum torque, which means that there is a need to intensify the IPMSM cooling system and there is deterioration of reliability. The advantage of the IPMSM is the reduction in the length of the active part by 30%. The advantage of the SHM is that there is 4.6 times lower cost of active materials. In addition, the SHM is more reliable than the IPMSM, as there is no risk of overheating, demagnetization or degradation of permanent magnets over time.

In sensorless vector control of Permanent Magnet Synchronous Motor (PMSM) drives, it is important to obtain accurate rotor position. High-frequency (HF) voltage injection method is usually used to estimate the rotor position of the motor at low speed. However, the use of the digital filter reduces the estimation accuracy of the rotor position. In this paper, an improved signal processing method based on the HF square-wave voltage injection method is used to obtain the rotor position error signal. A third-order extended state observer (ESO) is used to estimate the rotor position and speed. Compared with the traditional sensorless control strategy, the proposed method reduces the use of the digital filter, simplifies the signal processing, eliminates the influence of the inverter nonlinearity on the accuracy of rotor position estimation and improves the dynamic performance of the system. Experimental results are provided to verify the effectiveness of the proposed method.

For electric vehicles (EVs), permanent magnet synchronous motors (PMSMs) are competitive owing to their high power factor, high efficiency and high power density. In this paper, four types of PMSMs with different rotor topologies are designed with the same motor main dimensions and the same amount of permanent magnet usage. First, the different PMSMs are compared in terms of their torque characteristics. The torque characteristic curves of the four motors are displayed with the control method i <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> =0 for surface-mounted PMSM (SPMSM) and Maximum Torque per Ampere (MTPA) for interior PMSM (IPMSM). It turns out that IPMSM has higher starting torque than SPMSM due to the reluctance torque. Among the three IPMSMs with different rotor structures, V-shape IPMSM and delta-shape IPMSM can provide higher output torque under the same current supply with the higher salient rate. More information on the no-load magnetic density, torque ripple, efficiency and demagnetization problem operated at the peak current is also provided and compared. Then the four PMSMs with the same peak current are further analyzed and compared on the flux-weakening speed-enlarge (FWSE) capability. The results show good FWSE capability for all of the four PMSMs owing to the large peak current. However, the torque of SPMSM in flux-weakening control region is slightly higher than the IPMSMs.

The mechanism of torque ripple generation by time and space harmonic magnetic fields in permanent magnet synchronous motors is investigated to obtain advanced motor designs. The general expression between the torque ripples and harmonic air-gap flux densities in the motor is derived by using Maxwell stress tensor. Both the numerical and experimental verifications of this expression are carried out. By using this expression, the difference of the torque ripple generation between the surface and interior permanent magnet synchronous motors are discussed. Based on these investigations, the shape of the rotor surface of an interior permanent magnet motor is optimized. It is clarified that specific harmonic components of thetorque ripples in interior permanent magnet synchronous motors can be reduced to be nearly zero by optimizing the rotor surface shape.

Permanent magnet (PM) synchronous motors (PMSMs) have been used to drive a number of vehicles. They have high torque density, high efficiency, and a wide speed range. However, the high cost of PMs is disadvantageous. This paper presents a technique for increasing the torque density by modifying the shape of the PMs and minimizing the magnet volume. The PM characteristics such as flux density, demagnetizing force, PM energy product, and the air-gap flux density are represented by a lumped magnetic equivalent circuit when the thickness and width of the PM are increased for the same volume but with different shapes. The torque, torque ripple, core loss, magnet loss, and efficiency of three interior (IPMSM) models designed by the proposed method are compared by finite element analysis. In addition, the demagnetization of the PM due to high temperature, maximum torque load angle, and an adverse field is analyzed. Finally, the analysis result is compared with that of the experiment to verify the proposed model.

This work focuses on performance improvements of the stator flux estimation for a direct torque controlled interior permanent magnet (IPM) synchronous motor drive. In this paper, an adaptive sliding observer is presented to estimate the stator flux linkage based on the motor current model. The observer has better dynamic behavior, disturbance resistance and high accuracy estimation ability. The experimental results show that the proposed observer is able to deliver more accurate estimation than open-loop estimator both in the steady state and during transients

The paper deals with the experimental realisation of a sensorless interior permanent magnet (IPM) synchronous motor drive. The motor has been specifically designed to get a wide flux-weakening region, to minimise the drive power rating in spite of a wide speed range. Position and angular speed of the rotor are obtained through an extended Kalman filter (EKF). The estimation algorithm requires neither the knowledge of the mechanical parameters, nor the initial rotor position. In the paper, particular emphasis is placed on control algorithms, that are complicated by the motor anisotropy and that have been specifically studied to enhance the overall system performance.

In order to improve the performance, efficiency and reliability of the interior permanent magnet synchronous motor (IPMSM) drive, a set of control strategies are developed for wide speed range operation. A rotor flux oriented vector control with model reference adaptive system (MRAS) based rotor position/speed estimation is employed as the basic control strategy for IPMSM drive. A control strategy named maximum torque per ampere (MTPA) is applied to minimize the motor current magnitude during low speed operation. While an over-modulation method is employed to enhance the voltage transfer ratio of PWM inverter and the output torque capability of IPMSM during high speed operation, and flux weakening control is developed for high speed stable operation of IPMSM drive. Furthermore, phase current reconstruction under overmodulation is taken into account, which lowers the system cost and expands the working range of PWM inverter fed IPMSM motor drives. The issue of seamless switching from MTPA during low speed range to conventional field-weakening control during high speed range is also discussed. Simulation and experimental results demonstrate the feasibility and effectiveness of these control strategies, which realizes the high performance operation of IPMSM drive in wide speed range.