Dual Three-phase Permanent Magnet Research Articles

On‐line dead‐time compensation method for dual three phase PMSM based on adaptive notch filter

For the dual three-phase permanent magnet synchronous motor(dual-PMSM), the deadtime can introduce fifth and seventh current harmonics, and they are only constrained by the small stator leakage impedance, which means even if there are only small fifth and seventh voltage harmonics, the resulting fifth and seventh current harmonics will be very large. The harmonic current will make an increment of the system loss, thus lead to an reduce of the efficiency of the speed control system. This paper proposes a harmonic current suppression strategy for dual-PMSM based on least mean square (LMS) adaptive notch filter. This strategy suppresses the fifth and seventh harmonic currents by introducing four LMS adaptive notch filters in the subspace. The proposed algorithm has good dynamic performance and is insensitive to motor parameters that are offset within a certain range. The effectiveness of proposed method is verified by a set of comparative simulations and experiments.

Enhancement of Disturbance Rejection Capability in Dual Three-Phase PMSM System by Using Virtual Impedance

Dual three-phase permanent magnet synchronous machine systems usually suffer from small impedance to voltage disturbance such as inverter voltage errors and back EMF harmonics. This article proposes a virtual impedance technique to increase the machine equivalent impedance and, thus, enhance the disturbance rejection capability of the system. This enhancement can contribute to current harmonic suppression in a wide range of frequencies. In addition, the introduction of virtual impedance can also reduce the system sensitivity to parameter variation, which helps to suppress the dynamic current overshoot, pulsating, and cross-coupling effect caused by the parameter mismatch. Simulation and experimental results have verified the effectiveness of the proposed control strategy.

Efficiency improvement of dual three-phase permanent magnet synchronous motor using modified switching table DTC for electric ship propulsion

A direct torque control using a classical switching- table ST-DTC can be used to control the torque and thus the speed of Dual Three-Phase Permanent Magnet Synchronous Motor (DTP-PMSM). The principle is based on direct application of control sequence by using two hysteresis regulators and a switching table. A large stator current containing low order harmonics is produced during the application of the classic ST-DTC technique, this leads to higher losses affecting the efficiency of the machine. To allow a reduction of these harmonics a modified switching-table approach based DTC technique is examined. Indeed, an improved ST-DTC strategy, which consist of replacing the vectors of the classical table with synthetic vectors, is discussed. The simulation results confirm the validity of the selected strategy.

Current Injection-Based Simultaneous Stator Winding and PM Temperature Estimation for Dual Three-Phase PMSMs

This article proposes a current injection-based simultaneous stator winding and permanent magnet (PM) temperature tracking technique for dual three-phase permanent magnet synchronous machines (PMSMs). The estimation models involving winding and PM temperatures are derived for different control strategies with the cancelation of inductances. To improve the tracking performance, a Kalman filter is used for simultaneous winding and PM temperature estimation. Compared with the existing methods, the proposed simultaneous winding and PM temperature estimation technique is independent of the voltage-source nonlinearity effect and is applicable to various machine operating conditions. The main features of the proposed method are underscored by the cancelation of inductance and the elimination of the need for a lookup table. The test results on a laboratory dual three-phase PMSM are used to validate the proposed method under different speed and torque conditions.

Harmonic Current Suppression of Dual Three-Phase PMSM Based on Model Predictive Direct Torque Control

The traditional direct torque control (DTC) method will produce a larger harmonic current in the x, y subspace when applied to a dual three-phase permanent magnet synchronous machine (DTP-PMSM) because the voltage vector used for DTC is not equal to zero in the x, y harmonic subspace. To mitigate this problem, in this manuscript, a model predictive direct torque control (MPDTC) method is proposed to eliminate the harmonic current in DTP-PMSM. The spatial distribution characteristic DTP-PMSM voltage vector is analyzed; then, the table of vector group can be obtained according to DTC, and each vector group can be combined to obtain the zero-voltage vector in the x, y subspace. According to the cost function, MPDTC selects the vector group and obtains the optimal vector sequence combination to eliminate the harmonic current in the x, y subspace. Furthermore, the MPDTC achieves closed-loop control of harmonic currents in the x, y subspace. The MPDTC can also eliminate harmonic currents caused by other factors. The simulation results show that the method of MPDTC can effectively suppress the harmonic current of DTP-PMSM.

A Generalized Decomposition Model of Dual Three-Phase Permanent Magnet Synchronous Machines Considering Asymmetric Impedances and Compensation Capability

This article first proposes a generalized decomposition model for dual three-phase (3-ph) permanent magnet synchronous machines (PMSMs) with 0°, 30°, and 60° angle displacements between two sets of windings, allowing machines controlled in two-dimensional orthogonal αβ and xy subspaces. This model can decouple mutual inductances coupling phases from two sets, respectively. However, there often exist asymmetric impedances, due to inherent asymmetric machine parameters, cables with unequal lengths, manufacture tolerances, etc., in dual 3-ph PMSMs inevitably causing unbalanced phase currents and deteriorating the decoupling performance of the generalized machine model. Therefore, the generalized decomposition model incorporating asymmetric impedances is further developed, in which additional terms incurred by asymmetric impedances lead to the cross-coupling of αβ subspace and xy subspace. Through this model, the compensation capability of asymmetries is derived at a given dc link voltage. Then, a compensation strategy is illustrated to suppress unbalanced phase currents together with current harmonics caused by nonlinearities. Finally, experimental results testify the current balancing performance and simulation results further validate the machine model and the compensation capability.

Fault-Tolerant Control of Dual Three-Phase PMSM Drives With Minimized Copper Loss

In this article, a minimum-copper-loss fault-tolerant control scheme is proposed for open-phase fault and open-switch fault of dual three-phase permanent magnet synchronous motor (DT-PMSM) drives. Both the winding configurations of isolated neutral points and connected neutral points are studied in this article. In conventional minimum-copper-loss fault-tolerant control schemes, the constraints of sinusoidal phase currents result in insufficient copper-loss reduction. Different from them, the current references with the theoretically lowest copper losses are first derived and applied for different fault cases of DT-PMSM drives without using any unnecessary constraints in the proposed fault-tolerant control scheme. Thus, all phase currents in the proposed minimum-copper-loss fault-tolerant control scheme are optimized to be nonsinusoidal waveforms. Besides, the copper losses are further reduced by fully utilizing the remaining healthy switch in the faulty inverter leg for the open-switch fault of DT-PMSM drives with the proposed scheme. It has been theoretically and experimentally proved that the proposed fault-tolerant control scheme can reduce copper losses than all existing fault-tolerant schemes for both open-phase fault and open-switch fault in typical two-level voltage-source-inverter-fed DT-PMSM drives.

Direct Harmonic Current Control Scheme for Dual Three-Phase PMSM Drive System

The performance of model predictive control mainly depends on the accuracy of model and parameters, such as the back electromotive force (EMF) harmonics in dual three-phase permanent magnet synchronous motors (PMSMs). However, the back EMF harmonics would vary with the operation conditions. Thus, the parameter mismatches in the harmonic subspace would be inevitable. In this article, a direct harmonic current control scheme is proposed to provide further harmonic current suppression under parameter mismatches in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> subspace. First, deadbeat control concept is applied to calculate the reference voltage in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">αβ</i> subspace. This reference voltage vector is utilized to generate a group of control sets with different voltage vectors in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> subspace. Then, a slide mode control scheme is provided to deal with the inaccurate parameters in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> subspace. The reference voltage vector in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i> subspace is obtained with this slide mode control scheme without the remaining inductance parameters. Third, a two-step modulation method and cost function are discussed to further suppress the harmonic currents. The control sets generated by deadbeat control are optimized with the cost function. Moreover, a switching pattern with fixed switching frequency is proposed in this section. Finally, experimental results verify that proposed control scheme could further suppress the harmonic currents.

Modelling and vector control of dual three‐phase PMSM with one‐phase open

This study proposes a generic mathematical modelling and decoupling fault-tolerant vector control for dual three-phase permanent magnet synchronous machine (PMSM) with one phase open based on the conventional dual three-phase voltage source inverters, accounting for the mutual coupling between two sets of three-phase windings and the second harmonic inductance. When the dual three-phase PMSM has one phase open, the permanent flux-linkages are asymmetric and there are second harmonic components in the conventional synchronous reference frame (dq-frame). Based on the proposed mathematical modelling, both permanent magnet flux-linkages and currents become DC values in the dq-frame, and therefore, the conventional proportional integral (PI) controller can be used to regulate the dq-axis currents. Then, a decoupling fault-tolerant vector control with/without a dedicated feed-forward compensation is proposed to validate the correctness of the proposed mathematical modelling. Experimental results on a prototype dual three-phase PMSM with one phase open show that the second harmonic dq-axis currents can be well suppressed simply by the conventional PI controller and dedicated feed-forward compensation. It also shows that the decoupling fault-tolerant control based on the proposed modelling and control method has excellent dynamic performance, which is equivalent to the vector space decomposition control for the healthy machine.

Switching-Table-Based Direct Torque Control of Dual Three-Phase PMSMs With Closed-Loop Current Harmonics Compensation

In this article, the new closed-loop current harmonics compensation strategy is introduced in the switching-table-based direct torque control (ST-DTC) of dual three-phase permanent magnet synchronous machines. The harmonic current distortion is the major problem of ST-DTC of multiphase machines and is typically caused by the lack of control in the auxiliary x-y subspace under the vector space decomposition model. The synthetic vectors to obtain average zero voltage in the x-y subspace can be a solution. However, this cannot compensate for current harmonics; for example, due to dead-time and back-electromotive force distortion, which is also mapped into the x-y subspace. Therefore, in this article, the x-y voltage references are obtained by the closed control loop that controls x-y currents to zero. To modulate the nonzero x-y voltage reference, the new modulation approach employing voltage vector groups in the x-y subspace together with the new switching table is developed and incorporated into ST-DTC. Meanwhile, the analysis of the two available sets of 12 voltage vector groups illustrates a tradeoff between linear range in the x-y subspace and the dc-link voltage utilization rate. Finally, the effectiveness of the proposed ST-DTC strategy is verified through experiments and simulation.

Virtual-Vector-Based FCS Model Predictive Current Control with Duty Cycle Optimization for Dual Three-Phase Motors

This paper presents an improved finite control set model predictive current control (FCS-MPCC) based on virtual vectors with duty cycle control for dual three-phase permanent magnet synchronous motor (DTP PMSM) drives. Virtual vectors synthesized by two basic voltage vectors of the inverter are introduced to suppress the harmonic current by the vector space decomposition (VSD) model. And the virtual vectors with the optimal duty cycle can be obtained by duty cycle control using zero vectors to generate a fixed switching frequency. Moreover, a simple scheme of centrosymmetric switching patterns is presented for the realtime implementation. In this way, the performance of current tracking is improved while the computational burden is reduced. Finally, results of simulation analysis and DSP test for the three different strategies are given to verify the validity of the proposed strategy.

An Enhanced SVPWM Strategy Based on Vector Space Decomposition for Dual Three-Phase Machines Fed by Two DC-Source VSIs

This article presents an enhanced space vector pulse width modulation (SVPWM) strategy based on vector space decomposition (VSD) for the dual three-phase machines fed by two dc-source voltage source inverters (VSIs). Compared with existing methods that only account for balanced dc-link voltages, the proposed method considers unbalanced dc-link voltages in both the α-β and 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> planes. Two categories of medium voltage vectors are first defined in this article. An enhanced 12-sector SVPWM strategy that toggles two categories of medium voltage vectors in each fixed 30° sector is proposed. Moreover, the performance of the proposed method, including the modulation depth, the range of the dc-link voltage ratio, and the toggling point of the medium vector is analyzed. The proposed method can reduce the computational burden of the complicated sector classifications and it easily chooses suitable vectors to track the reference voltage with changes in the dc-link voltage ratio. The experimental results of the proposed SVPWM techniques are verified in a dual three-phase permanent magnet synchronous machine (PMSM) fed by two dc-source VSIs.

Model Predictive Torque Control for Dual Three-Phase PMSMs with Simplified Deadbeat Solution and Discrete Space-Vector Modulation

Unprecise voltage vectors applied in conventional model predictive control (MPC) would cause additional ripples in electromagnetic torque. To eliminate the problem, this article proposes an improved model predictive torque control (MPTC) based on deadbeat solution and discrete space-vector modulation (DSVM) for dual three-phase permanent magnet synchronous machines (PMSMs). First, deadbeat-direct torque and flux control (DB-DTFC) algorithm is applied and simplified, so that the computational burden can be reduced. Second, the virtual voltage vectors (VVVs) are adopted in dual three-phase voltage vector space to reduce voltage harmonics. Also, the DSVM is further proposed in this VVVs based vector space to generate more voltage vectors. After that, the simplified DB-DTFC and the DSVM scheme are artfully combined to select suitable voltage vector candidates for the MPTC, and the best one is then chosen to control the dual three-phase PMSMs. Finally, both simulation and experimental results are given to verify the effectiveness of the proposed method.

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.

Dual Reference Frame Based Current Harmonic Minimization for Dual Three-Phase PMSM Considering Inverter Voltage Limit

This article proposes an optimized current harmonic minimization (CHM) approach for dual three-phase permanent magnet synchronous machines (PMSMs) with consideration of inverter voltage limit. The current harmonic model is derived to analyze the dominant current harmonic components in dual three-phase PMSM drives. Dual reference frame (DRF) model is proposed to convert the current harmonics into dc components in the new DRFs, and PI controllers are employed to control voltages to minimize the dc components. This article will prove that current harmonics can be minimized by using the DRF model. Since CHM requires additional voltages, inverter voltage limit must be considered especially at high speeds. Hence, inverter voltage limit is considered to derive the theoretical control strategy, in which minimal copper loss is selected as the design objective to reduce current harmonic with limited voltage. The proposed approach is supported by theoretical analysis and proof, and it does not require inverter voltage and machine parameters. Moreover, the proposed approach is compared with an existing method to show the performance improvement and evaluated with extensive tests on a laboratory prototype under both steady-state and transient conditions.

Current harmonic elimination for dual three‐phase PMSM based on a spatial analytical model of flux linkage

Compared with the conventional three-phase motors, the dual three-phase permanent magnet synchronous motors (PMSMs) have many advantages and have been widely used in various drive fields. However, one major disadvantage of these machines is that they are easy to generate large stator current harmonics, which makes it difficult to have an excellent performance in the drive field. To solve this problem, this study introduces a current harmonic elimination method based on a spatial analytical model of flux linkage. The study reconstructed the analytical model of flux linkage from finite element analysis. The analytical model can describe the spatial harmonics of flux linkage by considering the rotor position information. Based on the model, an active feedforward controller was proposed to eliminate current harmonics by actively injecting the corresponding voltage harmonics, the voltage harmonics are calculated by the model of flux linkage. The performance of the proposed method in eliminating current harmonics is verified by simulations and experiments.

Fault-Tolerant Control of Common Electrical Faults in Dual Three-Phase PMSM Drives Fed by T-Type Three-Level Inverters

In this article, a deadbeat predictive current control based fault-tolerant control scheme is proposed for common electrical faults in T-type three-level inverter-fed dual three-phase permanent magnet synchronous machine (PMSM) drives, which aims at providing a solution for the application of high power rating, low switching frequency, low complexity, and high reliability. First, deadbeat control is combined with current prediction to obtain precise voltage reference for the current control. Each three-phase three-level inverter generates a single optimal inverter voltage vector based on a new division method of space vector diagram. In this way, both low switch frequency and high control precision can be guaranteed in a high-power motor system. Second, fault-tolerant control schemes are designed for five types of common electric faults in a T-type three-level inverter-fed dual three-phase PMSM without changing the mathematical model and control framework. Thus, the complexity of the proposed fault-tolerant control schemes can be avoided and smooth transition can be guaranteed. The validity of the proposed schemes is verified by experimental results.

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;