Dual Three-phase PMSM Research Articles

Interleaved Model Predictive Control for Three-Level Neutral-Point-Clamped Dual Three-Phase PMSM Drives With Low Switching Frequencies

In this article, the control strategy is studied for the neutral-point-clamped three-level inverter-fed dual three-phase permanent-magnet synchronous motor (PMSM) drive with low switching frequencies. An interleaved finite-control-set model predictive control (MPC) scheme is proposed, where a two-layer MPC is designed to solve the multiobjective optimization problem. The two sets of windings in PMSM are sampled and controlled in an interleaved way so that the control delay and the prediction horizon of the drive system are reduced by half. Moreover, the proposed interleaved control scheme increases the equivalent sampling and control frequency from the perspective of the whole drive system, and thus provides better steady-state performance and dynamic performance. With the switching states of one inverter remaining unchanged, the cross traversal of vector candidate sets between two sets of windings is avoided, and the computational burden can be reduced effectively. Experimental results are given to verify the validity and effectiveness of the proposed interleaved control scheme.

An Online Flux Estimation for Dual Three-Phase SPMSM Drives Using Position-Offset Injection

The rotor flux linkage of permanent-magnet synchronous motor (PMSM) is of great importance for monitoring and high-performance control. However, most of the existing online estimation methods need prior knowledge of other PMSM parameters such as stator resistance and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> axis inductance, which are difficult to realize in the rank-deficient models of electrical machines. This article proposes a simple online estimation method of rotor flux linkage for the dual three-phase surface-mounted PMSM (SPMSM) drives with the assistance of injected position offset. The independent estimation model has been developed for the rotor flux linkage by appropriate setting of positon offset between two sets of three-phase windings of dual three-phase SPMSM drives. The proposed method not only has little influence on the output torque and high signal-to-noise ratio for observation, but also offers the superior performance in estimation accuracy irrespective of the influence of VSI nonlinearity. In addition, the proposed position-offset-based method is suitable for the full-speed region including the field-weakening operation. Finally, comprehensive experimental results are presented to verify validity of the proposed method under different working conditions.

Direct Modulation Pattern Control for Dual Three-Phase PMSM Drive System

The additional harmonic currents in multiphase permanent magnet synchronous motors (PMSMs) have been widely discussed and suppressed by the virtual vectors (VVs). However, the concept of VVs would result in an increasing in the switching frequency and losing the controllability in the harmonic subspace. In this article, a novel direct modulation pattern control (DMPC) method is proposed to provide the further discussion on the lower switching frequency and the better harmonic current suppression. First, a deadbeat control concept is applied to calculate the reference voltage vectors in torque production. In dual three-phase PMSM, there are several switching patterns which could generate the reference voltage vector. The designs of these switching patterns are determined according to the demand. In fact, two design concepts under the structure of DMPC is proposed. One is called the low switching frequency design. The control sets of this design is several switching patterns with only one switching signal. Another is called the low THD design. The control sets of this design is two switching patterns with opposite harmonic voltage vectors. Second, the influence of these different switching patterns in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents is optimized by a cost function. Actually, there are two types of cost function. One is a multiobjective cost function, which is designed to regulate both the amplitude of switching patterns and suppress the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents. Another is derived from the first cost function that regulates only the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents. The amplitude is determined directly in the voltage vector calculation. Finally, the experimental results show a good performance of these control strategies, in terms of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">αβ</i> currents production, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> currents and the switching frequency reduction.

Direct Torque Control of Dual Three-Phase Permanent Magnet Synchronous Motor

In this paper a direct torque control strategy for dual three-phase permanent magnet synchronous motor (DTP-PMSM) is presented, the machine has two sets of three-phase stator windings spatially phase shifted by 30 electric degrees. In order to reduce the stator harmonic current, torque and flux are controlled based on regulators and Vector Space Decomposition technique. The proposed approach has the benefits of low stator current distortion and low torque ripple. The validity and the efficiency of the selected technique are confirmed by simulation results.

A Predictive Torque Control Method for Dual Three-Phase Permanent Magnet Synchronous Motor Without Weighting Factor

In order to solve the problem of the difficult design of weighting factor for model predictive torque control (MPTC) of dual three-phase permanent magnet synchronous motor (DT-PMSM), this paper proposes a MPTC strategy without weighting factor. Firstly, the virtual voltage vector (V3) is introduced to reduce the harmonic currents. Secondly, an approximate alternative principle for predicted current is proposed, which simplifies the dual-vector prediction model and decreases the complexity of the prediction model. The control set at ( $k+1$ )th is selected by judging the change in torque and the position of the stator flux, which reduces the number of candidate voltage vectors. Thirdly, the cost function is selected according to the system state at two adjacent moments. The cost function separates the electromagnetic torque and the stator flux, and eliminates the weighting factor. Decreasing the complexity of the prediction model, reducing the number of candidate voltage vectors, the combination of the two methods in this paper can significantly reduce the computational burden of the CPU. Finally, experiments verify the effectiveness of the proposed method. The results show that the proposed method greatly reduces the calculation burden of the system under the performance of electromagnetic torque does not change much.

Flux-Weakening Control of Dual Three-Phase PMSM Based on Vector Space Decomposition Control

This article proposes a flux-weakening (FW) control for dual three-phase permanent magnet synchronous machine (DTPMSM) based on vector space decomposition (VSD) control, where the output voltage in αβ subplane is employed for voltage feedback in the FW control loop. As the fundamental components are mapped to αβ subplane while the fifth and seventh harmonics are projected to harmonic z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> subplane, the FW current from this new control in αβ subplane is sixth harmonic-free regardless of the fifth and sixth harmonics being resulted from the nonsinusoidal back electromotive force (EMF) or inverter nonlinearity. The proposed control is compared with the conventional FW feedback control extended for DT-PMSM, where the FW control is applied to the two sets of three-phase windings separately. The experimental results show that the proposed FW control based on VSD is superior to the conventional FW control in terms of reduction in current unbalance and harmonic currents.

Experimental implementation PWM strategy for dual three-phase PMSM using 12-sector vector space decomposition applied on electric ship propulsion

The current paper aims at presenting and examining an implementation on a digital signal processor (DSP) of the conventional space vector pulse width modulation (CSVPWM) so as to control the dual three phase permanent magnet synchronous motors (DTP-PMSM) drives applied on electric ship propulsion. It is also an attempt to accomplish a developed control of this technique based on vector space decomposition (VSD) strategy. By this strategy, the analysis and the control of the machine are achieved in three two-dimensional orthogonal subspaces. Among the 12 voltage vectors having maximum, the conventional technique namely the adjacent two-vectors (12SA2V) is chosen. Thereby, the test platform allows the implementation of the chosen vectors which are modeled on MATLAB/Simulink using block diagrams and the automatically generated code which is targeted in the DSP card processor. Simulation and experimental results have exposed the efficiency of the proposed test bench of 5 KW prototype machine by using a low-cost TMS32F28379D.

Field oriented control based on a 24-sector vector space decomposition for dual three-phase PMSM applied on electric ship propulsion

&lt;p&gt;&lt;span lang="EN-US"&gt;A Field Oriented Control (FOC) strategy based on a 24-Sector Vector Space Decomposition (24SVSD) technique used to control a Dual Three-Phase Permanent Magnet Synchronous Motor (DTP-PMSM) applied on electric ship propulsion prototype is presented in this paper. This machine is supplied by Dual Three-Phase Voltage Source Inverter (DTP-VSI). This study carried out on these multiphase machines has revealed that the large zero sequence harmonic current components on (z&lt;sub&gt;1&lt;/sub&gt;, z&lt;sub&gt;2&lt;/sub&gt;) subspace, constitutes major drawbacks; despite their advantages. The machine’s dynamic model is accomplished in three two-dimensional and orthogonal subspaces. In order to reduce more extra stator harmonic currents that produces losses, the current work is also concering of to consider the three different approaches for the sake of boosting the machine’s efficiency. Thus, the principle selection of the reference voltage vector and the time calculation method are presented in details. The proposed strategy effectiveness is validated by simulation results.&lt;/span&gt;&lt;/p&gt;

Deadbeat Predictive Current Control-Based Fault-Tolerant Scheme for Dual Three-Phase PMSM Drives

In this article, a deadbeat predictive current control-based fault-tolerant scheme is proposed and developed for the dual three-phase permanent-magnet synchronous motor (PMSM) drives. For the open-phase fault of the dual three-phase PMSM, the current references are derived without low-order components for minimum stator copper loss. The utilization of the deadbeat predictive current control guarantees high-control bandwidth for the current references under fault-tolerant operation. Then, a fault-tolerant control scheme is proposed for the open-switch fault based on the hybrid current references, which can fully utilize the remaining one health switch in the faulty inverter leg and minimize the stator copper loss. The additional copper loss caused by the open-switch fault can be reduced by around half with the proposed fault-tolerant control compared to previous remedial strategies. Thus, the ultimate torque output under the open-switch fault can be increased by around 20%. The machine model, the space vector diagram, and the control structure of the motor systems remain unchanged with the proposed fault-tolerant control scheme. The validity of the proposed fault-tolerant control schemes is verified by experiments.

Diagnosis-Free Self-Healing Scheme for Open-Circuit Faults in Dual Three-Phase PMSM Drives

Aiming at tolerating common electric faults of multiphase motor drives comprehensively and minimizing the adverse impacts from the remedial scheme itself, a diagnosis-free self-healing scheme is put forward for the open-circuit faults of dual three-phase permanent-magnet synchronous motor (PMSM) drives. First, the self-healing mechanisms of dual three-phase PMSM drives are analyzed in detail. On the basis of theoretical analysis, the repressed self-healing capability of the dual three-phase PMSM drives is fully released by optimizing the current references on harmonic subspace. Since the diagnosis process is not required in the proposed self-healing scheme, the misdiagnosis problem and the prolonged damage caused by the additional time cost of diagnosis can be fundamentally avoided. The proposed self-healing scheme can be generally applied to open-switch faults, single open-phase faults, and multiple open-phase faults in the multiphase motor drives. No change is required for the machine model, modulation strategy, or control framework under different open-circuit faults. Thus, the complex transition strategies among different fault-tolerant control methods for different faults can be avoided, and the adverse impacts from the remedial scheme itself can be minimized. Experimental verification is presented to prove the validity of the proposed self-healing scheme.

Effect of Phase Shift Angle on Radial Force and Vibration Behavior in Dual Three-Phase PMSM

This article investigates the effect of phase shift angle on radial force and vibration behavior in the dual three-phase permanent magnet (PM) synchronous motor (DTP-PMSM). First, the elimination principles of stator magneto-motive force and radial force harmonics with different phase shift angles are derived. Afterward, a 48-slot/22-pole DTP-PMSM with appropriate windings configurations are analyzed from the perspectives of the electromagnetic performance and vibration behavior in detail. It is found that the 7.5° and 30° configurations have great significance for reducing the amplitude of radial force harmonics. The 7.5° configuration has the lowest second-order radial force amplitude, while the 30° configuration has the smallest amplitude of fourth-, sixth-, and eighth-order radial forces. According to the results calculated by the multiphysics vibration prediction model, the 30° configuration has lower vibration acceleration in the entire frequency band. Finally, the prototypes of the 48-slot/22-pole DTP-PMSMs with 30° and 60° phase shift angle are fabricated. The tests are conducted to validate the theoretical analysis.

Current Harmonic Suppression Algorithm for Asymmetric Dual Three-Phase PMSM

Based on the vector space decomposition (VSD) transformation, the currents of an asymmetric dual three-phase permanent magnet synchronous motor (ADT-PMSM) with isolated neutral points are decoupled into the torque, producing α-ß components in the fundamental subspace and the loss-producing x-y components in the harmonic subspace. In order to suppress the current harmonics, a feedforward voltage compensation that is calculated according to the dead time, turn on/off time, and the voltage drop is added to the reference voltage of the control algorithm. Due to the limitations of the feedforward voltage compensation method, a feedback current control loop is set up in the x-y subspace, where an improved resonant controller is adopted to generate the compensation voltage. The improved resonant controller can achieve a high gain at a specific frequency. The experimental results verify the effectiveness of the proposed method.

Single- and Two-Phase Open-Circuit Fault Tolerant Control for Dual Three-Phase PM Motor Without Phase Shifting

A fault tolerant control strategy for dual three-phase permanent magnet synchronous motor (DTP-PMSM) with 0° phase shifting between two windings is proposed in this paper. When a DTP-PMSM suffers from single- or two-phase open-circuit fault, to maintain the torque performance, current in faulty phase must be compensated by other healthy phases, which causes asymmetric self- and mutual inductances. Therefore, the 2nd harmonic component can be observed in the dq -axis currents and torque ripple also increases. To analyse this harmonic component in two types of faults, post-fault model of no-phase-shifting DTP-PMSM based on vector space decomposition (VSD) method is built in this paper. Then, proportion-integral-resonant (PIR) controller which can be used to suppress the specific periodic disturbance is applied to compensate the 2nd harmonic components. As the resonant controller is rarely dependent on motor parameters, phase and amplitude of current harmonic, the PIR controller can be applied in no-phase-shifting DTP-PMSM to suppress the harmonic caused by single- and two-phase open-circuit faults. The experimental results validate the effectiveness of the proposed fault tolerant control under single- and two-phase open-circuit faulty conditions.

Control Strategy for a Five-Leg Inverter Supplying Dual Three-Phase PMSM

This study presents a novel control strategy for a five-leg inverter-fed dual three-phase permanent-magnet synchronous motor (DT-PMSM)system. Three different five-leg inverter topologies (operating modes) can be reconfigured by choosing a pair of phases for sharing the common leg. The five-leg inverter operation mode with 150° phase difference can achieve full torque output, but the utilization of DC bus voltage is low. The operation mode with 30° phase difference has higher DC bus voltage utilization but lower output torque. The modified double zero-sequence injection (DZI) PWM strategy based on carrier-based PWM (CBPWM) for five-leg inverter operating modes is proposed. This strategy can achieve the maximum DC bus voltage utilization. The five-leg inverter operating modes can be used as a fault-tolerant solution for the occurrence of a fault in one leg of the six-leg inverter. Compared with the commonly used open phases fault-tolerant control (FTC) strategies, this strategy has the advantages of without increasing the stator copper, reducing the torque ripples, and implementing easily. Experimental results verify the effectiveness and feasibility of the proposed strategy.

Vector Control of Asymmetric Dual Three-Phase PMSM in Full Modulation Range

The total control range of asymmetric dual three-phase permanent magnet synchronous motor (ADT_PMSM) is divided into three different segments by voltage modulation range and current control dimensions and respective control strategies to get the injected voltages in harmonic subspace for three segments are presented in this paper. The three segments are sinusoidal current modulation region, sinusoidal voltage modulation region and overmodulation region. In sinusoidal current modulation region, resonant controller is adopted in the harmonic subspace to calculate the injected voltages, which can compensate the effect of six-phase voltage source inverter (VSI) dead time for two sets of three-phase windings and takes the pole correction into consideration. In sinusoidal voltage modulation region, open loop control strategy in harmonic subspace is adopted. Overmodulation region 1 and 2 are defined in overmodulation region, and the harmonic voltages which are injected into harmonic subspace to extend the modulation index are calculated based on superposition principle and VSD theory. In order to achieve smooth transition from different regions, a novel space vector pulse width modulation (SVPWM) technique for ADT_PMSM is proposed. The experimental results demonstrate the validity and feasibility of the suggested control approach.

Digital Collaborative Development of a High Reliable Auxiliary Electric Drive System for eTransportation: From Dual Three-Phase PMSM to Control Algorithm

For electrified transportation (eTransportation) systems, multi-phase motors can provide higher performance and reliability than three-phase ones, but also bring more challenges in their optimal design and control. In this article, a set of high reliable electric drive system based on dual three-phase permanent magnet synchronous motor (DTP PMSM) is developed for auxiliary systems in eTransportation field. A digital collaborative develop process is proposed with the support of multiple software tools. Design, manufacture, and bench testing stages of the DTP PMSM, the two-level six-phase inverter, and the control algorithm are efficiently incorporated. A prototype of the multi-phase electric drive system is fabricated and tested. Comparison of the simulation analysis and experimental results confirms the effectiveness of the collaborative develop progress. Control algorithms based on dual d-q model and vector space decomposition model are both verified and compared via the bench test. Operation mode switching from six-phase mode to three-phase mode is also realized with the prototype system, verifying its capability in fault-tolerant and potential in efficiency optimizing.

Optimized SVM and Remedial Control Strategy for Cascaded Current-Source-Converters-Based Dual Three-Phase PMSM Drives System

In this article, the switching strategy and the remedial control scheme are studied for the cascaded current-source converters (CSCs) fed dual three-phase permanent-magnet synchronous motor (PMSM) variable-speed drives. An optimized space vector modulation (SVM) strategy is proposed to reduce the DC-link current ripple for the proposed drives system. In particular, this switching strategy can work effectively for motor drives under low speed with low back EMF, where there exists a large voltage difference between peak voltage values on the grid side and the motor side. Apart from that, a hybrid fault-tolerant control scheme is also designed for the open-phase fault in dual three-phase PMSM drives system, aiming at achieving small DC-link current ripple and torque ripple, low copper loss, and machine-friendly waveform quality. With the proposed optimized SVM and the hybrid fault-tolerant control strategy, the DC-link current ripple of the cascaded CSCs system can be effectively reduced and good operational performance can be obtained under both normal operation condition and open-phase fault condition. Experimental results are provided to verify the effectiveness of the proposed methods.

Vibration Reduction for Dual-Branch Three-Phase Permanent Magnet Synchronous Motor With Carrier Phase-Shift Technique

In motor drive system, ear-piercing acoustic noise caused by high-frequency vibration from motor becomes unacceptable in sensitive environments, due to the application of pulsewidth modulation (PWM) and consideration of switching losses. In this paper, a novel method which associates a presented dual three-phase permanent magnet synchronous motor (PMSM) called dual-branch three-phase PMSM with carrier phase-shift technique is implemented to completely reduce odd-order PWM frequency vibration. The proposed motor has two no phase-shift three-phase windings, whose coils wind on the same teeth; it is driven by paralleled inverters with magnetically coupled inductors. With carrier phase shifting $\pi $ , the odd-order carrier frequency current harmonics with the identical amplitude in two windings are opposite in phase, and therefore the produced magneto-motive-force (MMF) harmonics in the air gap offset with each other. The experimental results are provided to verify the validity of the proposed method in vibration reduction. Compared with the previous work of vibration reduction for dual three-phase PMSMs, the proposed method can achieve total elimination of odd-order PWM frequency vibration.

Comprehensive Diagnosis and Tolerance Strategies for Electrical Faults and Sensor Faults in Dual Three-Phase PMSM Drives

In this paper, fault diagnosis and fault-tolerant control strategies have been studied comprehensively for dual three-phase permanent-magnet synchronous motor (PMSM) drives to improve the reliability. Based on direct torque control (DTC) with space vector modulation, a series of diagnostic and tolerant control methods have been proposed for five types of faults, namely, speed-sensor fault, dc-link voltage-sensor fault, current-sensor fault, open-phase fault, and open-switch fault. First, diagnosis and tolerant schemes are proposed for speed-sensor fault by estimating the rotor angle speed with the rotating speed of stator flux. Second, diagnosis and tolerant schemes are proposed for dc-link voltage-sensor fault by combining the current model based stator flux observer with the voltage model based stator flux observer. Third, a three-step method is designed to diagnose three types of faults related to current signals, namely, current-sensor fault, open-phase fault, and open-switch fault simultaneously. A vector space decomposition based current estimation method is proposed to achieve fault-tolerant control for the current-sensor fault, and the voltage compensation based fault-tolerant control is presented for both open-phase and open-switch faults. The experiments have been taken on a laboratory prototype to verify the effectiveness of the proposed fault diagnosis and fault-tolerant schemes.

Carrier frequency harmonic suppression in dual three‐phase permanent magnet synchronous motor system

Dual three-phase permanent magnet synchronous motor (PMSM) is a major area of interest within the field of motors since it inherits the advantages of both the PMSM and multiphase machines. While dual three-phase PMSM (DTP-PMSM) system has a more severe carrier frequency harmonic problem due to the low impedance in the harmonic subspace, which will not only decrease the efficiency but also produce the high-frequency audible noise. This study proposes an improved space vector pulse-width modulation (SVPWM) strategy by changing the sequence of the pulse-width modulation wave. The improved SVPWM strategy with a 10 kHz carrier frequency has the same effect as the conventional SVPWM with a 20 kHz carrier frequency, which will significantly decrease the switching loss, lead to lower size of inductance, capacitance and eliminate the high-frequency audible noise. Three existing mainstream SVPWM strategies in DTP-PMSM system are introduced and the proposed strategy can be used in them without affecting their original advantages. The switching times are also minimised to reduce the switching loss. The theoretical derivation is proposed to prove the harmonic suppression ability of the proposed SVPWM and the implementation procedure is given then. The simulation and experimental results proved the effectiveness of the strategy.