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This paper presents a fault-tolerant operation for dual three-phase surface-mounted permanent magnet machines (SPMSMs) that were both electrically connected on three winding phases and mechanically connected on one shaft. The open-phase fault-tolerant operation is considered in dual three-phase SPMSMs drive thus combining motor drive of three-phase and single-phase. The proposed method controls the torque of each motor with different phases using a single inverter. In order to control these motors, the torque and current are distributed between the motors with the specific ratio. Methods for minimizing torque ripple and copper losses and maximizing the output torque of the three-phase motor are stated in this paper. Accordingly, a system with cost-effective and enhanced reliability is proposed without any configuration adjustment or auxiliary switching devices. The mathematical analysis and experiments are presented to verify the feasibility of the proposed method. After the fault, the resulting system is able to provide up to 75% of the rated torque, and up to 50% of the torque can be utilized without any torque ripple. [ABSTRACT FROM AUTHOR]

In an open-end winding permanent magnet synchronous machines drive with single dc voltage source, zero-sequence current (ZSC) can lead to a high current stress of power modules and loss of motor. Therefore, some modulation strategies have been employed to alleviate ZSC by suppressing zero-sequence voltage (ZSV). However, ZSC still exists in the system because ZSV can also be generated by other nonlinear factors of inverter such as the dead time of system. In addition, zero-sequence back electromotive force in the zero-sequence path can also enlarge torque ripple and ZSC. In order to deal with above problems, first, this paper proposes a full-order adaptive zero-sequence observer to estimate future ZSC and ZSV, which are able to compensate one-step control delay. Second, to achieve the maximum voltage dc bus utilization, this paper proposes a novel deadbeat predictive current control (DPCC) scheme with alternate sub-hexagonal center pulsewidth modulation strategy to suppress ZSC and torque ripple simultaneously. Finally, this paper presents a comparative study of two types of methods, namely traditional DPCC scheme and the proposed DPCC scheme. Simulation and experimental results are demonstrated to verify the effectiveness of the proposed DPCC scheme. [ABSTRACT FROM AUTHOR]

This paper presents nonlinear optimization-based position and speed estimation scheme for IPMSM drives with arbitrary signal injection generated by inherent switching ripples associated with finite control set model predictive control (FCSMPC). The existing standard sensorless techniques are not suitable for FCSMPC which applies voltage vectors directly to an electrical machine without a modulator. The proposed method optimizes the nonlinear cost function derived from the standard IPMSM model with respect to position and speed at every sampling interval. This method can be applied to any type of signal injection and, hence, an ideal candidate for sensorless FCSMPC. In this method, the signal injection is needed only to generate persistent excitation to maintain the observability at low speeds. A strong persistent excitation is always present with FCSMPC except at standstill where the control applies null vector when the reference currents are zero. This situation is overcome in this paper by introducing a small negative $d$ -axis current at standstill. Thus, the proposed method can estimate the position and speed over a wide speed range starting from standstill to the rated speed without a changeover or additional signal injection. This paper also presents detailed convergence analysis and proposes a compensator for standstill operation that prevents converging to saddle and symmetrical solutions, and therefore, also eliminates the well-known ambiguity of $\pi$ rad in position estimation. The performance of the proposed sensorless scheme is experimentally verified for a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a current control of dual three-phase permanent magnet synchronous machine (PMSM) based on five-leg inverter. The five-leg inverter can be utilized to drive dual three-phase PMSM with full torque at slow speed when the conventional dual three-phase voltage source inverter (VSI) has a faulty inverter leg. Usually, the common leg in the five-leg inverter may have severe current stress. By dedicated selection of which two phases as a pair to share the common leg, its current rating is approximately half of current rating of other legs. Meanwhile, the five-leg inverter can fully fulfill the vector space decomposition control for dual three-phase PMSM, which has the same dynamical performance as the conventional dual three-phase VSI. However, due to the asymmetry of five-leg inverter non-linearity, the currents of dual three-phase PMSM are unbalanced. To mitigate this issue, the five-leg inverter non-linearity compensation is also introduced and investigated in this paper, whose effectiveness is verified by comparative experiments on a prototype dual three-phase PMSM. [ABSTRACT FROM AUTHOR]

This paper proposes a d–q cross-coupling current controller for permanent magnet synchronous motor (PMSM) drives. Slotting and cross-coupling effects in PMSMs cause the effective air-gap length to vary with the rotor angle and distort the distribution of the air-gap flux. Such distortions have a significant influence on the current control by changing the relationship between the stator currents and voltages. To investigate their effects, a d–q model is established in this paper, which is suitable for describing the voltage characteristics of the actual PMSMs. The model contains the angle-dependent parameters, the cross-coupling inductance between d–q axes, and the q-axis permanent magnet flux linkage, unlike the ideal d–q model. The transfer function matrix from the d–q currents to d–q voltages of PMSM is newly derived from the model. Based on that, the current controller with the feedback and feedforward terms of 2-by-2 matrix is proposed. It is designed so that the independent gains are in low-pass filter forms and the coupling control gains are zero with eliminating interference between d–q axes. The proposed controller contributes to providing the stable control performance by canceling the slotting and cross-coupling effects. The performance of the proposed current controller is verified by experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a novel current solution is proposed to suppress the electromagnetic torque ripple of brushless dc motor (BLDCM), and simultaneously minimize the rotor eddy-current loss to prevent thermal demagnetization of the permanent magnets. To determine the current solution, an optimizing problem of the rotor loss is developed, subjecting to the constraints of average torque and the sixth harmonic torque. Finite dc supply is also considered. In addition, an improved model of the rotor loss is proposed with a simpler expression of quadratic form, so that the problem can be solved analytically. A comparison with the square-wave and minimal-copper-loss current solutions is studied based on a 3.77 kW, 12000 r/min BLDCM, which indicates that the proposed solution performs as well as the two solutions in suppressing the torque ripple and producing stator losses, but the rotor loss can be significantly reduced by at least 86% and 35%, respectively. Precision of the rotor loss model and performance of the proposed solution are validated experimentally on the 3.77 kW BLDCM setup. [ABSTRACT FROM AUTHOR]

This paper presents a simple dc-link voltage modulation scheme to minimize the commutation torque ripple in a permanent magnet brushless dc motor (PMBLdcM). Maintaining a constant current in the noncommutating (NC) phase helps to minimize the torque ripple, which can be achieved by boosting the motor input voltage whenever two phase currents are undergoing commutation. At low speeds, since the required ac voltage at commutation is also less than nominal, the standard pulsewidth modulation operation of the inverter with nominal dc-link voltage suffices. However, at higher speeds, a momentary (only during the commutation interval) boost in the dc-link voltage (above the nominal level) is needed to ensure a boost in motor voltage, and hence, a steady current in the NC phase. In the proposed scheme, the dc voltage boost at higher speeds is obtained by connecting two capacitors in series, which are normally connected in parallel, across the dc-link. The proposed scheme is verified for a 1-hp PMBLdcM drive through simulations and experiments in the laboratory. Results exhibit a notable improvement in reducing the torque ripple. [ABSTRACT FROM AUTHOR]

This paper proposes an effective charging-torque elimination method for six-phase integrated on-board electric vehicle (EV) chargers. The integrated EV charger is derived from the power inverter, motor windings, sensors, and microchips, which can significantly reduce the system cost and volume. In fact, the charging electromagnetic torque is inevitable to produce, since the alternating currents flow through the motor windings. This is due to the motor windings serving as the filtering inductors of the rectifier for the on-board charger. In order to keep the vehicle standstill during the charging process, a universal expression of charging torque is derived and analyzed, which is according to magnetic co-energy approach. All possible charging torque elimination positions are presented with a numerical method. Moreover, the unity power factor and zero sequence current control are executed during the EV charging process. Finally, the proposed charging torque elimination method is verified by both simulation and experimentation. The results prove the validity of the proposed charging-torque elimination method for six-phase permanent magnet synchronous machine. [ABSTRACT FROM AUTHOR]

This paper proposed a robust deadbeat predictive current control (PCC) of the permanent magnet linear synchronous machine (PMLSM) with an extended state modeling (ESM) based Kalman filter (KF) for both the state and disturbance estimation. First, the disturbance dynamics of the PMLSM electrical subsystem is analyzed in detail and then the ESM is constructed as considering the disturbance as a higher order integrator motivated by the main idea of the extended state observer. Second, the KF for the current prediction with reduced noises and the disturbance estimation due to the parameter variation is designed combining with the ESM. Furtherly, the robust PCC is introduced with the ESM-based KF. Finally, the parameter tuning for the ESM-based KF is discussed with the discrete simulation and then the experimental results are given under the single current closed loop and the double cascade position-current loop with linear-varying parameter. Both the simulation and experimental results verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Three-phase current reconstruction techniques with a single current sensor have been studied for permanent magnet synchronous machines (PMSMs) drive system due to its reducing cost and volume. In order to minimize the current reconstruction dead zone in the conventional method with a single dc-link current sensor, a strategy to couple multiple available positions through the single current sensor is proposed in this paper. With the proposed method, two independent equations of the stator currents can be obtained by sampling the single current sensor twice in both zero voltage vectors and active voltage vectors. By solving these two equations, the phase current reconstruction can be achieved accurately, which moves the current reconstruction dead zone toward six corner area of the space vector hexagon. Meanwhile, in order to guarantee the proposed method suitable in the whole linear modulation region, the suitable selection of the pulsewidth modulation switching period is analyzed in detail. Furthermore, the optimal selections of multiple sampling positions are discussed to lower the actual implementation difficulty of the proposed method. Finally, the experimental results on the PMSM demonstrate that the reconstructed phase currents with the proposed method can be always in consistent with the actual measured currents under different working conditions. [ABSTRACT FROM AUTHOR]

The traditional pulsewidth modulation predictive control (PPC) has poor steady-state performance when used for fault-tolerant control of multi-phase machine drives, because this paper finds that PPC theoretically has a large steady-state error when tracking ac signals. Thus, an improved PPC regulator is proposed, which can rapidly and accurately track ac current references and realize decoupling control among phase currents. The proposed method is developed by redesigning the transfer function of the conventional PPC to a resonant form, reducing the amplitude and phase error in the conventional approach. By making the resonant frequency of the resonant term track the machine frequency, the amplitude and phase response of the system at the working frequency are close to zero. Thus, the proposed R-PPC features fast-response-performance and high-ac-tracking-accuracy. The effectiveness of the proposed method has been verified on a surface-mounted permanent magnet synchronous machine by experiments. [ABSTRACT FROM AUTHOR]

Optimal currents with appropriate harmonic components injected into the motor windings can effectively mitigate torque ripple for interior permanent magnet (IPM) type brushless dc motors (BLDCMs). However, existing approaches may fail to accurately inject the optimal currents into motors due to the limited current loop bandwidth. This paper proposes a simple enhanced generalized vector control strategy to mitigate the torque ripple for IPM-type BLDCMs. With the proposed vector control strategy, the control block diagram for IPM-type BLDCMs is as simple as that with traditional vector control for sinusoidal permanent magnet synchronous motors. First, an electromechanical energy conversion voltage (EECV), considering the effects of the non-sinusoidal back-EMF and the rotor salience property, is proposed in αβ-axis. Then, a novel coordinate frame is constructed with the proposed EECV, which is based on the arbitrary reference frame theory. As a result, the currents of IPM-type BLDCMs can be decomposed into two constant components, one being linked to the torque and the other one to the flux linkage. Thus, the bandwidth of current loop with simple proportional integral regulator can be equivalently expanded in the proposed coordinate frame. Finally, comprehensive experiments are conducted in different operation conditions to validate the effectiveness of the proposed vector control strategy. [ABSTRACT FROM AUTHOR]

This paper investigates open-phase fault modeling and fault-tolerant control (FTC) of dual three-phase permanent magnet synchronous machines (DT-PMSMs). A comprehensive fault model that considers both the permanent magnet torque and reluctance torque under the open-phase fault is proposed first. This model shows that under open-phase fault the average torque of DT-PMSM will decrease, while torque ripple will increase significantly. Then, a novel optimized FTC approach is developed based on the proposed model, in which genetic algorithm (GA) is applied to optimize the stator currents to maximize the average torque and minimize the torque ripple under open-phase fault. The proposed fault model and GA-based FTC are applicable to both surface-mounted and interior DT-PMSMs. However, existing approaches neglecting the reluctance torque are only applicable to surfaced-mounted DT-PMSMs. Moreover, the proposed approach is simple in implementation as it employs the original control structure and it is capable of smooth switching between the healthy operation and FTC without inducing noticeable torque pulses. The proposed approach is demonstrated with design examples, compared with existing one and validated with experiments on a laboratory interior DT-PMSM. [ABSTRACT FROM AUTHOR]

It is well known that spatial field harmonics will cause high eddy current losses in surface-mounted permanent magnets (PMs) especially for the fractional-slot PM motors. However, the influence of temporal current harmonics, especially of the high-order temporal harmonics caused by pulsewidth modulation voltages from an inverter, lacks attentions. This paper studies the eddy current losses of the PMs caused by high-order current harmonics. In order to simplify the calculation and save computation time, analytical methods are used to predict the current harmonics caused by the PWM inverter, and the armature reaction field, the eddy current density, and losses in the PMs generated by the current harmonics. Finite element analysis, coupling simulation, and experimental studies are used to verify the analytical results. The study results show that the high-order current harmonics cause much higher eddy current losses than those caused by slotting and fundamental current even though the amplitudes of the high-order current harmonics are much lower. [ABSTRACT FROM AUTHOR]

This paper presents a fault diagnosis technique for high-resistance connection (HRC) in a nine-phase flux-switching permanent-magnet (FSPM) machine based on zero-sequence voltage components (ZSVC), where the neutral-point connection mode is considered. A nine-phase FSPM machine topology is first introduced and no-load back electromotive force waveforms are analyzed. Moreover, the topologies of the nine-phase FSPM drive with different neutral-point connection modes are studied. Then, the mathematical model of a nine-phase FSPM machine with HRC is established with the consideration of the neutral-point connection mode and then the influence of the HRC on the ZSVC is analyzed based on the established model. It is shown that the HRC may be diagnosed by monitoring the change of the spectral contents of the ZSVC. Furthermore, this paper focuses on the situation of the nine-phase FSPM machine with one neutral point. In this case, to remove the influence of the FSPM machine operating point, an effective fault indicator is defined and used for HRC fault detection. Finally, the simulation and the experiment are carried out to validate the proposed method. Both the results show that the proposed method can be applied for the HRC fault diagnosis in a nine-phase FSPM machine. [ABSTRACT FROM AUTHOR]

The linear vernier permanent magnet (LVPM) motor incorporates the merits of high efficiency, simple mechanism, and low cost, which have a bright future in urban rail transportation. This paper proposes a new sensorless direct thrust force control (DTFC) for the LVPM motor. The novelty is the introduction of a modified flux linkage observer, which has strong robustness against the interferences, no phase lag, and no attenuation. Compared with conventional flux linkage calculation methods, the proposed observer can provide desirable flux linkages, which increases the robustness of the sensorless DTFC system. Simulation and experimental results based on an LVPM motor drive demonstrate the accuracy and robustness. The validations in the aspect of the robustness to parameter errors, measurement errors, and noise show the superiorities of the modified flux linkage observer. [ABSTRACT FROM AUTHOR]

Torque ripple has been a critical issue for high-performance applications using permanent magnet synchronous machines (PMSMs). An efficient approach to minimize torque ripple is to control the stator current to follow an optimized current reference, which will produce an extra torque ripple to cancel the existing one. This paper proposes a multiple reference frame (MRF) based controller for torque ripple minimization (TRM), in which the measured speed ripple is explored as the feedback control signal. The proposed MRF-based controller consists of a TRM controller whose task is to find the optimal current reference and a current controller whose task is to control the actual current to follow the optimized current reference. In TRM controller, the control of reference current magnitude and phase angle is decoupled, and proportional integral (PI) controller is able to achieve TRM control. In current controller, MRF is adopted to convert harmonic current control into dc current control; thus, PI controller is able to achieve harmonic current control with the use of MRF. Compared with existing approaches, the proposed controller is capable of TRM under both steady-state and transient conditions. The proposed controller is experimentally evaluated on a laboratory PMSM drive system. [ABSTRACT FROM AUTHOR]

In this paper, a systematic model-based approach for the state estimation of permanent magnet synchronous motors to build up sensorless drives is presented. A moving horizon estimation algorithm, an optimization-based scheme that yields excellent performance, is applied for the speed and position estimation. Under mild assumptions, an optimal problem of equality constrained quadratic programing type has been solved each iteration. The steady state and transient performance of the proposal are evaluated considering different horizon lengths. The influence of the latter is analyzed in terms of estimation error and computational burden. Besides, the behavior of the scheme is analyzed with different current control loops, i.e., with conventional proportional integral regulators and with model predictive control, highlighting its adaptability and good response in control schemes with completely different features. The performance is compared with that of an extended Kalman filter and the results prove the effectiveness of the proposed control scheme in terms of the estimation accuracy and robustness even at low speed operation. The algorithm has been efficiently implemented showing the real-time feasibility of the proposed approach up to 10-kHz sampling rate. [ABSTRACT FROM AUTHOR]

In this paper, it is shown how to obtain a low-cost, high-resolution, and fault-robust position sensing system for permanent-magnet synchronous motor drives operating in safety-critical systems, by combining binary Hall-effect sensors with high-frequency signal injection. It is shown that the position error signal obtained via signal injection can be merged easily into the quantization-harmonic-decoupling vector-tracking observer that is used to process the Hall-effect sensor signals. The resulting algorithm provides accurate, high-resolution estimates of speed and position throughout the entire speed range; compared to the state-of-the-art drives using Hall-effect sensors alone, the low-speed performance is greatly improved in healthy conditions and also following position sensor faults. It is envisaged that such a sensing system can be successfully used in applications requiring IEC 61508 SIL 3 or ISO 26262 ASIL D compliance, due to its extremely high mean time to failure and to the very fast recovery of the drive following Hall-effect sensor faults at low speeds. Extensive simulation and experimental results are provided on a 3.7-kW interior permanent-magnet drive. [ABSTRACT FROM AUTHOR]

A flux-weakening control algorithm with an improved stator flux linkage command's adjustment part of interior permanent magnet synchronous motors is proposed in this paper. The current commands are derived from lookup tables, which consider variation of motor parameters. The merits of this algorithm are the maximization of torque and high torque stability. Experimental results are demonstrated to verify the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of short-circuit current behavior during interturn short-circuit faults in permanent magnet synchronous machines (PMSMs) by considering the short-circuit contact resistance. For this purpose, an finite element analysis (FEA)-based equivalent circuit model is developed to understand the circulating current behavior in the shorted turns. Various fault resistance and number of shorted turn combinations are examined at different torque and speed levels. To include saturation due to high fault currents, the inductance matrix of faulty machine is created in FEA environment and incorporated into the equivalent circuit model as four-dimensional lookup tables. In order to take loop responses into account, the model is controlled through field oriented control (FOC) with closed speed and current loops. An experimental setup is built to verify the simulation results using a PMSM with several winding taps. It is shown that the experimental results and the simulations are quite consistent with each other. The findings from this study are essential to predict fault severity, develop mitigation techniques and determine the safe operating area for faulty machines. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive super-twisting algorithm based sliding-mode observer (STA-SMO) for surface-mounted permanent magnet synchronous machine (PMSM) sensorless control, in which voltage source inverter (VSI) nonlinearity is taken into consideration. An adaptive algorithm for online tuning the sliding-mode coefficients of STA-SMO is proposed based on the existing stable conditions. Thus, position estimation error can be reduced by the proposed adaptive algorithm in wide-speed range. Furthermore, voltage distortion due to VSI nonlinearity is online compensated to improve the accuracy of PMSM model. Because mismatch between reference and actual voltage due to VSI nonlinearity may bring large rotor position and speed estimation error, especially in low-speed range where distorted voltages may become dominant compared to actual voltages. Thus, a STA-SMO with adaptive sliding-mode coefficients and accurate voltage value could be obtained. Finally, the effectiveness of the proposed adaptive STA-SMO with online VSI nonlinearity compensation is verified on a surface-mounted PMSM by experiments. [ABSTRACT FROM AUTHOR]

In this paper, a new mathematical modeling for a six-phase interior permanent magnet synchronous motor (IPMSM) is presented. The proposed model utilizes two synchronous reference frames. First, the flux model in the $abcxyz$ frame is mapped into the stationary $dq$ frames and then to two synchronous rotating frames. Then, differentiating the flux models, voltage equations are derived in rotating frames. Through this analysis, the interaction between the $abc$ and $xyz$ subsystems is properly described by a coupling matrix. The torque equation is also derived using the two reference current variables. Flux model was verified through FEM analysis. Experiments were done using a 100 kW six-phase IPMSM in a dynamo system. The validity of the torque equation was checked with some experimental results under a shorted condition on an $xyz$ subsystem. [ABSTRACT FROM AUTHOR]

This paper presents an extension of previous methods in order to find electrical series connections between multiphase machines, allowing the independent control of each one of them. These new electrical series connections explore the symmetrical disposition of the phases of even-multiphase machines, allowing the inversed connection of some of the phases, different from the direct connections as it was previously done. Therefore, electrical series connections of two symmetrical six-phase or of four symmetrical ten-phase machines are now possible. Besides that, this new solution ensures a natural independent control of permanent-magnet synchronous machines even if the back electromotive forces (back EMFs) generated by the rotor are not sinusoidal, without need of special machine conception or supplementary control strategy. This control independency is mathematically proved using the decomposition of multiphase machines in fictitious diphase and homopolar machines. Experimental results are presented to show the functioning and the advantages of this new coupling for two symmetrical six-phase permanent-magnet synchronous machines (PMSMs). [ABSTRACT FROM AUTHOR]

This paper proposes a novel circulating-current control strategy applied in back-to-back parallel three-phase converters with individual dc links for permanent magnet synchronous motor (PMSM) drives. First, the zero-sequence circulating current and the cross current paths in the whole parallel system are analyzed. Then, the models of an n-paralleled subsystem with individual dc links in both the three-phase stationary coordinates and the synchronous rotating coordinates are built up, which explores the fundamental mechanism of circulating current. Based on the analysis, a novel control strategy can suppress the circulating current at the motor side. The control system consists of two main loops in the d-axis, q-axis, and zero-axis, which are defined in this paper as sum control and difference control. The proposed control strategy effectively suppresses the circulating current in both steady-state and transient operations. The zero-sequence circulating current is greatly reduced by the difference control on the zero-axis. In addition, the bandwidth of the controllers is greatly improved, especially when the current-sharing inductance is much smaller than the stator inductance. Finally, with a PMSM load, the simulation and experiment results are presented to verify the theoretical analysis and proposed control strategy. [ABSTRACT FROM PUBLISHER]

This paper analyzes the dual inverter driven open-end permanent magnet synchronous motor (PMSM) system and proposes control method which can generate maximum output power in overall speed range for integrated starter/alternator. Dual inverter driven open-end machine system consists of two inverters which are connected to the both ends of the machine winding. By disconnecting one inverter from the power source, the dc-link voltage of flying capacitor can be boosted through the machine. Because one inverter is connected to the only power source, output power of the machine is regulated by the source connected inverter. In this paper, modulation method for maximizing output power of inverter and motor with reduced harmonic and loss is proposed. It is a hybrid modulation combining six-step and pulse width modulations. With proposed method, efficiency and operation area are improved and cost of entire driving system is also decreased due to the removing of dc-dc converter. Analyses, strategies, control method, and simulation results are descripted. The experiments with PMSM are accomplished to verify the feasibility of proposed method. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines performance is highly dependent on the permanent magnets (PMs) temperature. However, PM temperature measurement is not easy and is not normally implemented in standard machines. Alternatively, PM temperature can be estimated. PM temperature estimation methods can be divided into three major groups: thermal model-based methods, BEMF-based methods, and methods based on the injection of some form of high-frequency signal into the stator terminals of the machine. One concern for thermal model-based methods is that the model often needs to be adjusted for each machine design and application, knowledge of the machine geometry, materials, and cooling system being, therefore, required. On the contrary, BEMF methods and methods based on high-frequency signal injection estimate the magnet temperature from measurable electrical variables, knowledge of the geometry or cooling system not being required. Though they use the same type of signals, BEMF and high-frequency signal injection methods present relevant differences. This paper realizes a comparative analysis of both methods. Physical principles, performance, and implementation will be addressed. [ABSTRACT FROM AUTHOR]

This paper proposes a novel drive method for interior permanent magnet machines (IPMMs). In the proposed system, a two-phase IPMM is fed from a single-phase H-bridge inverter for low-cost applications. Its main winding in d -axis is connected to the inverter and the auxiliary winding in q-axis is inherently short circuited. This configuration enables the motor to operate in a wider speed range with higher energy efficiency than most other single-phase drive systems. Also, its torque capability in the high-speed range is as high as that of the three-phase IPMM drive despite the reduced power devices, drivers, and current sensors. Accordingly, the proposed system has benefits such as simple structure, low cost, high-power density, and improved efficiency. In this paper, the system is modeled with an equivalent three-phase machine. Based on the model, its torque characteristics and operating areas are analyzed and compared to those of the conventional IPMM drives. A speed control algorithm is also developed. It includes a maximum torque per ampere control to improve drive efficiency and a flux-weakening control to maximize the feasible inverter output voltage. The proposed system and control algorithm are verified by experimental results. [ABSTRACT FROM PUBLISHER]

This paper proposes novel pulsewidth modulation (PWM) schemes for multi-space-vector pulsewidth modulation (MSVPWM), which is used in position sensorless control of interior permanent-magnet synchronous motor drives. The estimation of the rotor position is based on magnetic saliency and employs high-frequency components of voltage and current, which are excited by MSVPWM. The difference between the instantaneously applied voltage vector and the reference voltage vector causes current ripple. Since six or four voltage vectors are generated during a PWM period, the sequences of the error voltage vectors lead to different types of current ripples. In this paper, the proposed MSVPWM schemes employ six sequences for zero-/low-speed operation and 24 sequences for high-speed operation to reduce line current ripple. Experimental results confirm that the proposed MSVPWM schemes lead to significant reduction in harmonic current while maintaining high performance of sensorless estimation. [ABSTRACT FROM AUTHOR]

This paper proposes a dc-flux-injection method for fault diagnosis of high-resistance connection (HRC) in a direct-torque-controlled permanent magnet synchronous machine (PMSM) drive system. In this method, the flux linkage bias is superimposed in the flux control loop of the direct torque control system, and then the dc current offset is excited in the stator windings. By superimposing two different pairs of flux linkage biases, a binary linear equation group about the resistance deviations can be established based on the stator currents and zero-sequence voltage component. By solving the equation group, the resistance deviations can be calculated for the HRC fault detection, faulty phase location, and fault severity estimation. Both the simulation and experimental results validate the effectiveness of the proposed method. In addition, the proposed method is immune to the symmetrical variations of stator resistance and interturn fault of the PMSM. [ABSTRACT FROM AUTHOR]

Health monitoring and fault detection are becoming more and more important in electrical machine systems due to the increasing demand for reliability. Winding turn fault is a common fault in permanent magnet (PM) machines, which can cause severe damages and requires prompt detection and mitigation. High resistance connection fault, which results in phase asymmetry may also occur but does not require immediate shutdown. Thus, apart from the fault detection, the classification between the two faults is also required. In this paper, a new technique for detecting and classifying turn fault and HRC fault by utilizing both the high and low frequency components of the zero sequence voltage is proposed with the enhanced sensitivity. The dependence on the operating conditions is minimized with the proposed fault indicators. The effectiveness of fault detection and classification has been verified by extensive experimental tests on a triple redundant fault tolerant PM assisted synchronous reluctance machine. The robustness of the turn fault detection in transient states and under no load conditions has also been demonstrated. [ABSTRACT FROM AUTHOR]

High-resistance connection (HRC) is a common electrical fault for the electric machine drive system. This fault can lead to the increased power loss and heat, thus possibly causing the damage of the electric machine drive system due to the excessive temperature. Hence, this paper first proposes a vector control strategy of the surface-mounted permanent magnet synchronous machine (PMSM) drive system with the HRC fault to minimize the copper loss. The mathematical model of the PMSM with the HRC is presented in abc stationary frame. The function relationship between the copper loss and the direct axis current, quadrature axis current, stator resistance, and the additional resistance due to the HRC is established and analyzed. The expression of the direct axis current, which minimizes the copper loss, is deduced under the condition of the HRC in one phase and two phases. Consequently, the proposed vector control strategy for the surface-mounted PMSM driving system is achieved. Both the simulation and experimental results show that the proposed method not only preserves the performance of the conventional vector control method, but also can effectively reduce the copper loss, thus protecting the PMSM from the damage due to the increased temperature possibly caused by the HRC fault. [ABSTRACT FROM AUTHOR]

In the control of permanent magnet synchronous machines (PMSMs), predictive controllers have received considerable attention due to the enhanced dynamic responses. However, periodic disturbances caused by dead-time effects and sampling errors deteriorate the performances of PMSMs. In order to suppress periodic disturbances, one typical control structure is to adopt several corresponding resonant controllers connected in parallel with the main controller. Even though excellent steady-state performances can be obtained, coupling effects between reference tracking and periodic disturbance attenuation can be observed, leading to significant transient oscillations under the situation of a reference step change. In order to realize decoupling between reference tracking and disturbance attenuation, this paper proposes a dual-loop predictive control structure, in which the reference tracking is only determined by the primary predictive controller. Periodic disturbance attenuation is achieved through an embedded disturbance rejection loop. By applying the proposed controller, periodic disturbances are strongly attenuated while smooth and fast transient performances are simultaneously guaranteed. Furthermore, a wide range of low frequency harmonics can be successfully suppressed, including but not limited to the main periodic harmonics. The steady-state performance, dynamic responses, and robustness against parameter variations of the proposed controller are verified through experiments based on a 2.3-kW PMSM. [ABSTRACT FROM AUTHOR]

This paper introduces a novel pulsewidth modulation (PWM) scheme for an open-winding permanent magnet synchronous machine (OW-PMSM) driven by dual two-level three-phase inverter with common dc bus, which can effectively deal with the inherent zero-sequence current (ZSC) problem. Based on the conventional symmetrical unipolar double-frequency sinusoidal PWM scheme with an appropriate phase shift, the common mode voltage (CMV) of two inverters remains same and cancel out each other to eliminate the modulated zero-sequence voltage (ZSV) disturbance source. In this case, the double-frequency effect can be retained to reduce the ac side current ripple and suppress both corresponding motor vibration and acoustic noise, which is advantageous to improve the synthetic performance of motor. The dc-bus voltage utilization of the novel PWM scheme is proved to reach the same maximum value comparing to the conventional modulated ZSV elimination scheme. Meanwhile, a zero-sequence controller is designed to suppress ZSC by further adjusting the two CMVs to counteract other zero-sequence disturbance sources. To verify the analysis, the proposed PWM technique associated with the control method is implemented in an OW-PMSM experimental setup to validate the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

Offline parameter identification of permanent magnet synchronous machines (PMSMs) is of great importance for general-purpose drives with sensorless control. This paper proposes an amplitude-auto-adjusting signal injection (ASI) method for the parameter self-learning of PMSMs at standstill considering inverter nonlinearities and the digital time-delay effect. The ASI method achieves the inductance identification process under various dq-axis currents and at the same time prevents the unexpected rotor rotation during the self-commissioning process. For the test PMSM, the spatial inductance maps of dq-axes and abc-phases concerning the magnetic saturation and cross-coupling effects are identified along with the stator resistance. To enhance the estimation accuracy, an error model of the inverter nonlinearities in dq-axes is established, and a compensation method independent of inverter parameters is proposed based on the Hermite interpolation. In addition, the influence of the digital time-delay effect is analyzed and compensated based on the transient model of the circuits. The effectiveness of the proposed parameter self-learning scheme is confirmed on a 2.2-kW PMSM drive. The accuracy of the experimental results is validated by finite element analysis on the test machine. [ABSTRACT FROM AUTHOR]

The acoustic noises caused by the fixed-frequency signal injection scheme limit the applications of saliency tracking based sensorless control methods for interior permanent magnet synchronous machine (IPMSM) drives at low-speed operation. In this paper, a pseudorandom-frequency sinusoidal injection (PRFSI) considering the sample and hold effect in practical applications is proposed to reduce the undesired acoustic noises. Since the power spectral density (PSD) of the excited high-frequency (HF) current could be dispersed and continuously distributed with PRFSI, the additional HF acoustic noises can be reduced. Through the comparative analysis of HF response currents PSD results for PRFSI and fixed-frequency sinusoidal injection (FFSI), the principle of acoustic noises reduction with PRFSI is analyzed theoretically. Furthermore, the optimal selection of the injection signals is derived considering the sample and hold effect. Whereby, a comparative evaluation of the proposed PRFSI versus FFSI is carried out on a 2.2-kW position sensorless IPMSM drive, in terms of position estimation and PSD results, which verifies the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This article proposes a novel flux weakening scheme for five-phase PMSM with active harmonic currents injection. The conventional flux weakening control schemes applied in the five-phase PMSM do not consider the voltage limit drop in the fundamental subspace due to the harmonic current controller. Thus, the derivation between the reference current trajectory and actual current trajectory would cause the current distortion when applying deadbeat current controller (DBCC). This article analyses the precise voltage limit circles considering the voltage drop caused by the resistance and harmonic currents control at first. Then, a feed-forward flux weakening control algorithm is designed to optimize the current trajectory online. The gradient descent method is used to ensure the converge speed and stability of the optimized current trajectory. Thirdly, the peak value of phase currents would be clipped by the harmonic currents to prevent the inverter current limit, where a new non-linear harmonic current controller is designed to precisely control the harmonic currents. Finally, the DBCC and modified SVPWM technology are utilized to generate the duty cycle. The proposed improved flux weakening control strategy is successfully implemented in an interior five-phase PMSM, and the performance demonstrate the effectiveness of this strategy. [ABSTRACT FROM AUTHOR]

Accurate rotor position detection is essential for the surface permanent magnet synchronous motor (SPMSM) drive system to realize the stable and reliable operation. In this paper, two linear hall-effect sensors are utilized to detect the rotor position. However, the estimated errors in the measured signals, especially the harmonic components, impact on the accuracy of the rotor angle estimation significantly. For this reason, a high-precision rotor position detection method, which is based on the synchronous frequency extractors (SFEs) is presented. Two SFEs are used to filter out the high-order harmonics contained in the hall-effect signals. Further, the estimation of the rotor speed is used for the field-oriented control scheme of the PMSM. The proposed method is advantageous since it is simple, low cost, and high estimation accuracy. Finally, an experimental driveline system used for testing the electrical performance of developed high-speed magnetically suspended motor is built. The experimental results validate the feasibility and effectiveness of the proposed method in whole speed range. [ABSTRACT FROM AUTHOR]

This paper presents a new closed-loop V/f control scheme for sensorless interior permanent-magnet synchronous motor drives. The proposed control scheme combines the merits of conventional V /f and field-oriented control strategies to achieve simple and high-performance motor drive. Two feedback stabilizing loops are designed to correct the V/f voltage vector reference and improve overall system stability. The voltage vector phase angle reference can rapidly be corrected instead of using indirect frequency modulation, which makes it more robust against transient disturbances. In addition, a maximum torque per ampere plug-in block is implemented to optimize torque generation efficiency without intensive power or power factor angle calculations. The proposed scheme is ideal for applications which require good control performance over the wide operating speed range. It also shows robustness to parameter variations caused by temperature increase or flux saturation. Theoretical analysis along with comparative simulation and experimental results are provided to validate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This study presents a novel overmodulation strategy for a six-phase voltage source inverter (VSI)-fed dual three-phase permanent-magnet synchronous motor. The proposed strategy can achieve minimum harmonic injection in the overmodulation region. Four-vector space vector pulse width modulation (SVPWM) renders mathematic foundations for this given method. However, the classical four-vector SVPWM used in six-phase VSI has asymmetrical pulse width modulation waveform, which makes it difficult for hardware implementation. In this paper, the modulation algorithms in both linear and overmodulation regions have been unified and implemented with the double zero-sequence injection PWM strategy. This strategy is able to overcome the inherent shortcomings of the four-vector SVPWM, and it achieves smooth transitions from linear to overmodulation region. Simulation analysis and experimental results demonstrate the effectiveness and feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

In this paper, a simple and accurate method is proposed for online estimation of the rotor permanent magnet (PM) flux linkage for surface mounted PM synchronous machines. By advantageously utilizing an injected zero-voltage vector, the effects of inductance in estimating the PM flux linkage is eliminated. The inverter voltage error and phase resistive voltage drop effects are minimized by repeating the test at different speeds. Therefore, as a result, only the voltage commands are needed for PM flux linkage estimation, resulting in great simplicity. Filtering the current ripple caused by the zero-voltage vector injection is not necessary. The proposed method can be used with sensored or sensorless field-oriented control strategies. The experimental results have shown a good accuracy of the proposed new method. [ABSTRACT FROM AUTHOR]

This paper develops an online interturn fault diagnosis method for permanent magnet synchronous machine (PMSM). The mathematical model of the PMSM with interturn fault is established. The zero-sequence voltage component and zero-sequence current component are analyzed in the PMSM, respectively. Then, the new fault indicators are defined to remove the influence of the variation of the rotor speed and an effective frequency tracking algorithm is presented to extract fault indicators. In this proposed method, not only the interturn fault can be effectively detected, but also the phase in which this fault occurs can be accurately identified. The experiments are carried out and the experiment results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers (SMO) with conventional structure have the disadvantages of high-frequency chattering and poor estimation accuracy, which limit its application in high-performance servo systems. In this paper, the mathematical model of the conventional LTID-SMO is deduced and analyzed. A new LTID-SMO is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operational conditions. [ABSTRACT FROM AUTHOR]

In this paper, a novel multiphase reconfigurable and fault-tolerant drive converter topology is proposed for driver with fail-work capability, and fault-tolerant strategies are proposed for open-circuit and short-circuit faults in the single-phase windings, aiming to improve the motor drive system's fail-work ability in the high reliability applications. The drive converter topology can isolate open-circuit and short-circuit faults in power supplies, power devices, or switches. Then, it can reconfigure the drive circuit topology from independent H-bridge to star type by reconfigurable switches and power devices, according to the fault-type and the fault-tolerant truth tables. After reconfiguration, remedial operation will be utilized for open- and short-circuit faults of windings, so that the motor system has twofold fail-work capabilities in driver and windings. Finally, based on a series of experiments on a transit co-simulation model and test bench, the effectiveness and validity of fault-tolerant capability and the strategies are verified, and has twofold fail-work remedy. [ABSTRACT FROM AUTHOR]

This paper presents a maximum torque per ampere (MTPA) control method for interior permanent-magnet synchronous motor drives. The proposed method employs a variable-equivalent-parameter MTPA control law to calculate the MTPA current references. Different from conventional MTPA control laws, this novel MTPA control law equivalently considers both the influence of the motor parameter values as well as the influence of the derivatives of motor parameters with respect to d- and q-axis currents on the MTPA control. Therefore, the proposed method can achieve the accurate MTPA control under different load conditions. In addition, this novel MTPA control law avoids the computation of derivatives of motor parameters and the complicated computations that exist in conventional MTPA control laws. Thus, the proposed method can provide the MTPA current references easily and in real time, allowing for fast MTPA control to be achieved. Both simulation and experimental results confirm the effectiveness of the proposed MTPA method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel deadbeat current control (DBCC)-based model predictive control for an asymmetrical six-phase permanent magnet synchronous machine. First, the solution of DBCC is adopted to obtain the expected reference voltage vector (RVV). Then, two groups of virtual vectors, in the total number of 24 with different magnitudes, are defined for the sake of current harmonics suppression. Subsequently, two in-phase virtual vectors which are closest to the RVV are selected as the prediction vectors. The next step is to define a cost function which is composed of the error between the RVV and the available prediction vectors. Then, the selected two virtual vectors are evaluated and the one that minimizes the cost function will be applied in the next instant. In this way, only two prediction vectors need to be evaluated and the computation burden is highly alleviated. In the meantime, the weighting factor involved in predictive torque control is avoided. In addition, to achieve the readily implementation with standard pulsewidth modulation switching sequence, 18 virtual vectors are artfully replaced by their corresponding equivalent virtual vectors. Finally, the proposed method is comparatively studied and compared with other benchmark methods. Simulation and experimental results are offered to confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, an observer-based predictive vector-resonant current control strategy for permanent magnet synchronous machines is proposed, which can effectively improve system performance in case of disturbances caused by converter dead-time effect and model mismatch. Taking the external periodic, nonperiodic disturbances, and system delay into consideration, the system model in discrete-time domain is built. This model is then embedded with vector-resonant scheme with the aim of suppressing periodic disturbances resulting from converter dead-time effect and rotor flux harmonics. An extended-state observer is constructed in order to predict system behavior and to estimate the nonperiodic disturbances caused by parameter variations. The overall control law is then derived on basis of cost function minimization. With the proposed method adopted, the undesired anomalous peak around the resonant frequency in the frequency responses can be avoided. Moreover, enhanced transient performances and wider stability margin can also be obtained. The effectiveness and advantages of the proposed strategy are verified by frequency-domain analysis and comparative experimental studies. [ABSTRACT FROM AUTHOR]

In this paper, a load torque observer and two moment of inertia identification methods are developed for permanent magnet synchronous motor drive systems. First, the load torque identification method is proposed based on sliding mode observer, in which the mismatches of moment of inertia, electromagnetic torque, and viscous friction are all considered. It is analyzed that the chattering phenomenon will be well weakened if appropriate observer parameters are chosen. Second, based on the property that the mismatch of the moment of inertia will cause the load torque observation error, two types of moment of inertia identification methods, called direct calculation (DC) method and proportional integral (PI) regulator method, are presented to identify the moment of inertia. In addition, the identification errors of the DC and PI regulator methods are also analyzed theoretically. Simulation and experimental results show that compared with the conventional identification method of the moment of inertia, the proposed DC and PI methods have improved estimation accuracy. Moreover, the presented load torque observer also has high observation precision and fast convergence speed. [ABSTRACT FROM AUTHOR]

The permanent magnet linear synchronous machine driven motion stage for the semiconductor manufacturing equipment and machine tools has the basic requirement of high-dynamic response and high position accuracy. However, due to the direct-drive structure, the effect of parameter uncertainty, including the electrical and the mechanical one, and external disturbance will be directly exerted to the stage. In this paper, an integrated compensation scheme of the overall uncertainty and disturbance is proposed based on the second-order sliding-mode observer (SOSMO). First, an extended state model for considering the disturbance dynamics is established for both the electrical and the mechanical subsystems. To obtain high-dynamic current performance, the predictive current control (PCC) is utilized to design the current controller, and the SOSMO is integrated to compensate the main problem of a parameter mismatch for the PCC. Furthermore, the SOSMO is also configured to estimate the force ripple, and then the observation term is applied in parallel to the velocity controller. With this integrated scheme, the disturbance of the motion stage can be simply and effectively compensated. Experiments are demonstrated to show the effectiveness of the integrated method on both the PCC and force ripple suppression. [ABSTRACT FROM AUTHOR]

In order to have direct and better control of reducing the torque/flux ripples of interior permanent magnet synchronous motor (IPMSM), this paper presents an online torque and flux estimation-based nonlinear torque and flux control (NTFC) scheme of IPMSM drive considering motor electromagnetic developed torque and stator air-gap flux linkage as virtual state variables. For conventional nonlinear controller, thed—q-axis currents ($i_{d}$ , $i_{q}$) are considered as state variables that indirectly controls the torque/flux which may not be suitable for high-performance drives. On the other hand, conventional direct torque and flux control (DTFC) scheme suffers from significant torque ripples. The proposed work overcomes the major drawback of both the conventional nonlinear and DTFC schemes through the significant reduction in torque ripples. Stability of the proposed drive is also demonstrated through Lyapunov's stability criterion and global asymptotic stability is assured through the application of criterion supported by Barbalat's lemma. Reduced torque ripples and robustness of the proposed NTFC scheme is validated through comparative simulation and experimental results with classical nonlinear controller and DTFC-based IPMSM drive. The proposed NTFC scheme achieves the lowest possible torque ripples in steady state at different operating conditions. [ABSTRACT FROM AUTHOR]