Open-winding Permanent Magnet Research Articles

Model-free Current Predictive Control of Open-winding Permanent Magnet Synchronous Motor

Model-free Current Predictive Control of Open-winding Permanent Magnet Synchronous Motor

Compatible Phase Current Reconstruction Scheme for Fault-Tolerant Five-Leg Dual-Inverter Fed Open-Winding Permanent Magnet Synchronous Motor

In this paper, a novel phase current reconstruction strategy for a Five-Leg Dual-Inverter (FL-DI) fed Open-Winding Permanent Magnet Synchronous Motor (OW-PMSM) drive is put forward. Benefiting from the doubling of the power legs, the OW-PMSM drive is endowed with outstanding fault-tolerant ability. When an open-circuit fault occurs, the OW-PMSM automatically turns to the post-fault Two-Phase (2-ph) operation. By reconfiguring the wiring method, the fault-tolerant FL-DI topology is obtained, and the post-fault Three-Phase (3-ph) operation is realized. However, the current flow path changes and measurement vectors become unavailable in post-fault operation processes, making the existing current reconstruction schemes unusable. To prevent the system collapse caused by the current reconstruction failure, a novel current reconstruction strategy is proposed, which can be applied in the case of the open-circuit fault in any leg. In addition, the proposed current reconstruction strategy is compatible with the specific Zero-Sequence Current (ZSC) suppression for the FI-DI fed OW-PMSM drive, which ensures better system performance in the post-fault operation. The reconstructed current is of high accuracy, where the relative reconstruction error is 7.8% at low load and 5.3% at heavy load. Finally, experimental results are presented to verify the feasibility and effectiveness of the proposed strategy.

Zero-Sequence Current Suppression Strategy for Five-Phase OW-PMSM With Reduced Common-Mode Voltage and Inverter Losses

Zero-sequence current exists in five-phase open-winding permanent magnet synchronous motors (FPOW-PMSMs) with a common DC bus, resulting in harmonic current and system losses. Besides, the use of the dual-inverter increases inverter losses and induces a high-frequency common-mode voltage, damaging the bearing. This paper proposes a novel zero-sequence current suppression method for the FPOW-PMSM, which can reduce the inverter losses while decreasing the common-mode voltage. First, the average zero-sequence voltage equal to zero is considered a restriction to calculate the duration time of basis vectors. Five active vectors are selected to synthesize the reference voltage vector in each sector. Then, benefiting from abundant switching states redundancy, a novel switching states combination with minimum switching actions is proposed to reduce the common-mode voltage and inverter losses. Furthermore, the modulation range of the proposed modulation method is analyzed, indicating that the proposed method achieves considerable DC bus voltage utilization. Finally, the experimental results verify the effectiveness of the proposed method.

Open-Winding Permanent Magnet Synchronous Generator for Renewable Energy—A Review

The open-winding permanent magnet synchronous machines (OW-PMSMs) have recently been gaining more attention because of their fault-tolerant capability and power quality comparable to a 3-level converter-driven system. This paper reviews the common configurations of OW-PMSM when used as a generator, highlighting its shortcomings and benefits. The OW-PMSM with a common DC bus was found to be a promising direct-drive generator solution for wind energy conversion (WEC) systems considering fault tolerance, DC bus utilization, and power quality when appropriate control algorithms are in place. The presence of the zero-sequence current is the key disadvantage of the common DC bus configuration. The review highlights the algorithms that have been proposed to suppress the zero-sequence current of the OW-PMSM under healthy and various fault conditions, especially the open-circuit fault of semiconductor switch. Shutting down remotely located wind turbines because of faults, until they can be repaired, may not make economic sense. The OW-PMSM can offer the opportunity, to run a WEC system even under fault conditions albeit with low output power. This paper will assess the literature gaps in the existing control techniques that prevent the extension via a comprehensive review.

A Novel Two-Mode Inverter-Based Open-Winding PMSM Drive and Its Modulation Strategies

A novel two-mode inverter based open-winding permanent magnet synchronous motor (OW-PMSM) drive is proposed in this article. The proposed drive operates in hybrid-inverter mode at low and medium speed to achieve high power quality. The common-DC-bus mode is adopted at high speed to fulfill a wider speed range than hybrid-inverter mode. Based on the proposed drive, a modulation strategy for any voltage ratio is proposed, which integrates the instantaneous floating capacitor (FC) voltage into modulation to synthesize the reference voltage vector. The proposed modulation strategy can not only guarantee the FC voltage regulation but also start the drive when the FC voltage is zero and switch the mode of the drive smoothly. Besides, the excellent fault-tolerant capability of the proposed drive is studied under open-phase and switch faults. In the proposed fault-tolerant control, a sinusoidal zero-sequence current is injected to tolerate the open-phase fault in the common-DC-bus mode and redundant switching combinations are used to tolerate switch faults in the hybrid-inverter mode. All the claimed advantages have been validated by experimental results.

A Universal Model Predictive Control Strategy for Dual Inverters Fed OW-PMSM Drives

This study proposed a universal model predictive control (MPC) strategy for dual inverters fed open-winding permanent magnet synchronous motor (OW-PMSM) drives where two isolated buses have arbitrary DC voltages. Diverse and unordered space vector distribution caused by different voltage ratios of DC buses that greatly increases the calculation burden for the conventional MPC algorithm is analyzed in detail. Based on this, a novel MPC strategy that is universally applicable to any voltage ratio is put forward, which could decrease the number of candidate vectors from 49 to less than 15 in every cycle. Although the computational burden is reduced, the output power quality is unaffected owing to the effective simplification of the vectors. Besides, an optimized switching algorithm is designed to adapt to the situation when the voltage ratio changes during the operation state. The experimental results are presented to verify the effectiveness of the proposed method.

An Improved Modulation Scheme With Better Performance for Open-Winding Permanent Magnet Synchronous Motors Drives

In order to improve the performance of voltage synthesis of the open-winding permanent magnet synchronous motors (OW-PMSMs) with isolated DC bus when the voltages of two power supplies are not equal, an innovative voltage modulation method is proposed. The novel method is based on the conventional alternate sub-hexagonal center PWM method, but the low-voltage powered inverter is kept at low-potential clamped state throughout a period instead of having the two inverters clamped alternately. In this way, the high-voltage powered inverter expands the range of voltage synthesis, making up for the deviation between the synthesized voltage and the voltage reference when the high-voltage powered inverter is clamped and the low-voltage powered inverter modulates individually. Therefore, compared with the traditional method, a larger total voltage synthesis range is covered so that the capability of voltage synthesis is enhanced, thereby improving the quality of the corresponding torque and the output current. The simulation and experimental validations are presented to certify the effectiveness of the proposed method under different conditions, and the results prove that the new method indeed improves the current performance and reduces torque ripples.

Capacitance balance control strategy for three-phase four-switch open-winding permanent magnet synchronous motor

The open-winding permanent magnet synchronous motor (OWPMSM) system is a novel high-cost system that uses dual-inverters to control both sides of the stator to improve the performance of the motor. To save the system cost, the three-phase four-switch open-winding permanent magnet synchronous motor (TPFS-OWPMSM) system is proposed to replace the general three-phase six-switch OWPMSM system, but it brings the problem of bridge arm capacitor voltage offset. To solve the instability problem caused by capacitance, this paper carries out the state analysis and offset source analysis of the inverter capacitor voltage, and proposes a dual-inverters capacitor voltage balance control strategy. The capacitor balance control converts unstable capacitor offset voltage into current and injects the currents into the stator current loop through closed-loop correction. And this strategy includes the optimal control of different capacitors under dual-inverters with the goal of system stability. The effectiveness of the balancing strategy is verified by the simulation of various motor working conditions.

Novel SVPWM for Open Winding PMSM Drives With Simultaneous Common Mode Voltage Control and Full Frequency Zero Sequence Current Suppression

Zero sequence voltage (ZSV) can cause zero sequence current (ZSC), while variation of common mode voltage (CMV) can cause bearing current in an open winding (OW) permanent magnet synchronous machine (PMSM) fed by common dc -bus dual two-level inverters. This article proposes a novel space vector pulsewidth modulation (SVPWM) strategy for simultaneously eliminating CMV variation and suppressing full frequency ZSC harmonics in either linear or over modulation region by optimal selection of switching combinations. The proposed SVPWM can reduce large ZSV ripples and number of switching actions in the conventional CMV control method for the common dc -bus OW drive. Thus, high-frequency ZSC harmonics and switching frequency can be significantly reduced in both linear and over modulation regions. Moreover, the proposed SVPWM can suppress large low-frequency ZSC harmonics induced by the conventional method in over modulation region. The superior performances of CMV variation elimination and full frequency ZSC suppression in the proposed SVPWM are verified by experiments.

Harmonic Current Control of OW-PMSM for Low-Voltage Traction by Nonlinear Disturbance Rejection With Improved Modulation Scheme

The open-winding permanent magnet synchronous motor (OW-PMSM) has been developed, mostly potential for low-voltage traction in electric vehicles. Yet, both the disturbance from vehicle system under driving and the motor with low-reactance (LR) feature expose the limits of traditional controllers that are prone to great current harmonics. Therefore, the current control for LR OW-PMSM becomes challenging. The main objective of this research is to provide a current harmonic control strategy for LR OW-PMSM by the nonlinear lumped disturbance observer (NLDO) combined with improved space vector modulation (SVM) scheme. The existence of nonlinear, unknown, unmodeled factors has been confirmed by current measurement and harmonic analysis in full operation range, and thus is considered in proposed controllers. The NLDO is designed for all the three axes under the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> 0 frame. The SVM algorithm is adjusted to two switching patterns in order to get widened linear voltage modulation range. In addition, in the 3-D voltage space is the possible modulation area investigated. Ultimately, the target LR OW-PMSM has been designed, prototyped, and tested. The proposed NLDO, juxtaposed with ordinary PI and deadbeat controllers, reduces current harmonics on both the motor and inverter sides, possesses high robustness, and is practical for LR motors, according to experimental results.

A Novel SVPWM for Open Winding Permanent Magnet Synchronous Machine With Extended Operation Range

In this article, a novel space vector pulsewidth modulation (SVPWM) with the zero sequence current (ZSC) control strategy is proposed to extend the operation range for an open winding (OW) permanent magnet synchronous machine (PMSM). The proposed SVPWM can achieve the ZSC control and extend the operation range by considering voltages in the zero sequence axis and voltage vectors in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha \beta $ </tex-math></inline-formula> -plane, both of which are mapped by switching combinations in an OW drive. The effect of switching combinations with non-null zero sequence voltage (ZSV) on the modulation region of a common-dc bus OW-PMSM is investigated for the first time. The proposed SVPWM has optimal selection of switching combinations on the large hexagon rather than on the small hexagon in the conventional SVPWM for ZSC control and still maintains the controllability of ZSC in the overmodulation region. Compared with the conventional SVPWM strategy, the operation range of OW-PMSM can be extended over 10% with the proposed SVPWM strategy. The performance of both the conventional and proposed SVPWMs is compared experimentally.

An improved power balancing control scheme for open‐winding permanent magnet synchronous machine based on redistribution of reference voltages

In open-winding permanent magnet synchronous machine (OW-PMSM) applied in electric vehicular system, two voltage sources composed of battery packs are applied. For safety and better performance, the over-discharge on one of these two voltage sources should be avoided and their state of charges (SOCs) should be controlled in balance. On this basis, a reference voltage redistribution-based control scheme is proposed to balance the SOCs of OW-PMSM system in this letter, which utilizes the SOCs of the two voltage sources to distribute the reference voltages into two inverters. With the proposed method, the SOCs of the two voltage sources can be controlled in balance dynamically, while the synthesis of the reference voltage is not affected. The performance of the proposed method is validated experimentally.

Adaptive Capacitor Voltage-Based Model Predictive Control for Open-Winding PMSM System With a Floating Capacitor

In this article, an adaptive capacitor voltage-based model predictive control (ACV-MPC) strategy for the open-winding permanent magnet synchronous motor system with a floating capacitor (FC-OW-PMSM) is proposed. The control precision of the conventional model predictive control (CMPC) strategy is improved by adjusting the capacitor voltage without using high switching frequency methods. The position of voltage vectors (VVs) is uncertain under different capacitor voltages. To establish a unified motion process of the uncertain VVs, the VV trajectories are analyzed. Furthermore, a novel region division scheme is proposed to locate the candidate VV trajectory. To further determine the reference capacitor voltage and select the candidate VVs from the candidate VV trajectory, the proposed scheme is analyzed in each VV trajectory. Finally, a cost function with only one capacitor voltage constraint is carried out to select the optimal VV, and thus, the weighting factors and the complicated iterative process are both avoided. Experimental studies are carried out to verify the effectiveness of the proposed strategy.

Fast diagnosis strategy for open‐circuit fault of switch devices in open‐winding PMSM system based on voltage error estimation

In the dual inverter topology of open-winding permanent magnet synchronous motor system, due to the symmetry of the topology, switch devices have high similarity in working characteristics, which undoubtedly increases the difficulty in locating faulty devices. In this paper, by analysing the difference of inverter output characteristics before and after switch devices open-circuit fault, the relationship between the inverter output voltage error and fault location is found, and a fault diagnosis strategy is proposed. In this strategy, a construction method of fault phase characteristic current and the estimation equation of inverter output-voltage error are designed. Then, the real-time diagnosis of single device fault and two devices with the same characteristics fault at the same time is realized. Since the strategy proposed in this paper does not need additional voltage sensors, it has the same applicability as the traditional current method. In addition, the diagnosis method based on voltage information reduces the diagnosis time. Besides, this method is independent of the PWM strategy and is not sensitive to the phenomena of dead time and delayed insulated gate bipolar transistors switching. Finally, experimental results demonstrate the effectiveness of the proposed fault diagnosis strategy.

The Torque Ripple Optimization of Open-Winding Permanent Magnet Synchronous Motor With Direct Torque Control Strategy Over a Wide Bus Voltage Ratio Range

Due to the battery voltage performance of the dual power supply open-winding permanent magnet synchronous motor (OW-PMSM) system in electric vehicles, the dc bus voltages of the dual power supply varies and the traditional direct torque control (DTC) method will not be suitable and may lead to obvious torque ripples. Thus, in this article, based on the analysis of the effect of voltage vector on torque variation, a bus voltage ratio is employed in the switching table optimization strategy of DTC for OW-PMSM, the voltage vector selection method is also modified according to different voltage ratio, and then, the optimized control scheme for OW-PMSM over a wide bus voltage ratio is achieved to diminish the torque ripples. Finally, simulation models of the proposed method are built to verify the theory, and the corresponding experiments are also conducted to verify the feasibility and effectiveness of the proposed optimized control strategy.

An Improved Model-Free Predictive Current Control Scheme for Open-Winding PMSM with Common DC Bus

To improve the parameter robustness of the open-winding permanent magnet synchronous motor (OW-PMSM), this paper proposes an improved model-free predictive current control (MFPCC) method. First, the first-order ultra-local model of OW-PMSM is established, which does not contain any motor parameter. Secondly, a sliding mode observer (SMO) is introduced into the model to estimate the current in d-q-0 axis. Then, to suppress the torque ripple generated by the zero-sequence current (ZSC), the central hexagonal modulation strategy and the q-axis current injection method are combined, and the compensation current that needs to be injected into the q-axis is calculated according to the estimated value of ZSC. Finally, after considering the one-step delay, the voltage reference at the next instant is calculated based on the estimated values of d-q axis current and compensation current. Simulation and experimental results indicate that the proposed method can improve the parameter robustness of OW-PMSM, and the performance of current and torque has been improved under various parameter mismatch conditions.

A phase‐shift‐free synchronous reference frame filter‐based position sensorless control method for open‐winding permanent magnet generator system

An open-winding permanent magnet generator (OWPMG) system that offers features like fewer switching devices and high integration can be used in multi-input generator systems. To achieve high-accuracy position sensorless operation for the OWPMG system, this study investigates a phase-shift-free synchronous reference frame filter (SRFF-PSF) for use in the sliding mode observer (SMO) position sensorless algorithm. The proposed SRFF-PSF can completely restore the fundamental component of back-electromotive force (EMF) without phase shift and filter out the high-order harmonics owing to the following two improvements. First, the fundamental phase lag is eliminated by removing the low-pass filter between the back-EMF and the SRFF. Second, the error iteration of the output position angle is avoided by using the synchronous angle information from an additional phase locked loop module for the coordinate transformation of the SRFF. Based on the aforementioned improvements, the proposed method can effectively solve the phase shift problem in position estimation. The correctness and effectiveness of the method are verified by the experimental results.

The output performance of high power quality three‐phase to single‐phase AC power generation system based on open‐winding PMSG for standalone power system

A three-phase to single-phase direct AC power generation system based on the open-winding permanent magnet synchronous generator (PMSG) with the dual-inverter is proposed in this study for the standalone power system. The negative DC terminals of the dual-inverter are commonly connected, and the positive DC terminals are reconstructed as the output port of the single-phase AC power; the three-phase AC power generated by PMSG could be converted to be the high power quality single-phase AC power directly without any LC filters. Different from the traditional OW-PMSG system, zero-sequence current is employed to achieve adjustable frequency and voltage of the single-phase AC power, and the corresponding dual voltage-loop control strategy with the separate positive-sequence and zero-sequence currents regulation of PMSG is given to achieve high output performance. The effectiveness of the proposed control strategy and the output characteristics have been verified by simulation and the experiment of the prototype, and the results show that the high-quality single-phase AC power can be obtained at a wide speed range and at different load operating conditions.

Low-Complexity Deadbeat Model Predictive Current Control for Open-Winding PMSM Drive With Zero-Sequence Current Suppression

The application of model predictive current control (MPCC) on the open-winding permanent magnet synchronous machine (PMSM) drive system confronts the challenge of complexity due to the enumeration process and the multiobjective cost function evaluation. In this article, a new low-complexity MPCC is proposed to eliminate the online enumeration process and the cost function evaluation. In the proposed scheme, the reference voltage vector components are calculated based on the deadbeat principles. Then, the optimal voltage vector that matches the reference vector is selected from the control set based on predefined optimization criteria. These criteria are defined offline by solving the conventional current control cost function in the 3-D ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$ </tex-math></inline-formula> ), utilizing new 3-D analysis. The proposed control scheme is compared with the conventional finite control set (FCS)-MPCC and the existing 3-D-MPCC schemes using MATLAB simulation and hardware-in-the-loop (HIL) results. Compared with conventional FCS-MPCC and 3-D-MPCC schemes, the proposed control scheme presents the same salient features, such as fast dynamic response, low output current/torque ripple, and zero-sequence current suppression. The computational complexity of the proposed control scheme is much lower than the conventional FCS-MPCC.

Simplified model predictive current control strategy for open-winding permanent magnet synchronous motor drives

For a semi-controlled open-winding permanent magnet synchronous motor, to improve the steady-state control performance of the traditional predictive control system and to concurrently lessen the computation burden, a novel model predictive current control strategy is proposed in this paper. First, to achieve simultaneous control of the d-axis current, q-axis current, and current error-based cost functions. Then, to further reduce the calculation burden and complexity of the prediction algorithm, the predicted voltage of the converter is used as the reference voltage. In addition, the judgment of the sector where the reference voltage is located, and the selection method of the voltage vector are also given. Finally, the effectiveness of the proposed prediction method is tested by the simulation and experimental results.