Zero-sequence Current Suppression Research Articles

Advanced Zero-Sequence Current Suppression in P-HIL Testbed With Integration of Feed-Forward Compensation and LADRC

Advanced Zero-Sequence Current Suppression in P-HIL Testbed With Integration of Feed-Forward Compensation and LADRC

Direct Torque Control for Series-Winding PMSM with Zero-Sequence Current Suppression Capability

The series-winding permanent-magnet synchronous motor (SW-PMSM) has the merits of high output power and excellent control performance, as does the open-winding permanent-magnet synchronous motor (OW-PMSM). Meanwhile, it can greatly reduce the number of power devices. However, due to the existence of the zero-sequence path, zero-sequence current occurs, which can cause additional losses and torque ripples. Thus, this paper proposes a novel direct torque-control strategy for the SW-PMSM with zero-sequence current suppression capability (ZSCS-DTC). First, the series-winding topology (SWT) and the voltage vector distribution in the SW-PMSM drives are analyzed. Secondly, the basic DTC (B-DTC) scheme for the SW-PMSM is investigated, and the defects of zero-sequence current open-loop control in the B-DTC scheme are revealed. Thirdly, a new voltage vector synthesis scheme is proposed for suppression of zero-sequence current while ensuring bus voltage utilization. A switching table is reconstructed with the newly synthesized voltage vectors. On this basis, a ZSCS-DTC scheme for the SW-PMSM is proposed based on zero-sequence current closed-loop control so that electromagnetic torque, stator flux linkage and zero-sequence current can be controlled simultaneously. Finally, the effectiveness of the proposed ZSCS-DTC scheme for the SW-PMSM drives is verified.

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.

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 control for fault current damper based on model predictive control

In a multi-terminal direct current (MTdc) system based on a modular multilevel converter (MMC), high-speed and large interruption capability direct current circuit breakers (dc CBs) are required for dc fault interruption. However, commercializing these breakers is challenging, especially offshore, due to the large footprint of the surge arrester. Hence, a supplementary control is required to limit the rate of current rise along with the fault current limiter. Furthermore, the operation of the dc CB is not frequent. Thus, it can lead to delays in fault interruption. This study proposes the indirect model predictive control (MPC)-based zero-sequence current control. This control provides dc fault current suppression by continuously controlling the zero-sequence current component using circulating current suppression control (CCSC) and by providing feedback to the outer voltage loop and inner current loop of MMCs. The proposed control is simulated for pole-to-pole and pole-to-ground faults at the critical fault location of an MTdc system. The simulation is performed in Real Time Digital Simulator (RTDS) environment, which shows that the predictive control reduces the rate of rise of the fault current, providing an additional 3 ms after the dc fault occurrence to the dc CB to clear the fault. Besides, the energy absorbed by the dc CB’s surge arrester during the pole-to-pole and pole-to-ground fault remains the same with the proposed control.

Multivector-Based Model Predictive Current Control With Zero-Sequence Current Suppression for Three-Phase Series-End Winding Permanent Magnet Synchronous Motor Drives

To suppress the zero-sequence current and enhance the steady-state performance of the three-phase series-end winding permanent magnet synchronous motor (TPSW-PMSM) drives, a multi-vector-based model predictive current control scheme with zero-sequence current suppression is developed in this paper. The concept of the desired voltage is utilized to preselect the candidate voltage vectors and offer the guidance of the geometric division of the sector. In one sampling period, multi-voltage vectors are employed, and the combinations include one active voltage vector and one null voltage vector, and two active voltage vectors, which improves the steady-state performance. Meanwhile, the duty cycle of each voltage vector is derived based on an intuitive geometric expression of the cost function. Further, the relationship between the zero-sequence voltage injection and the switching sequence is revealed, and it is employed to suppress the zero-sequence current actively. In addition, overmodulation operation is also taken into consideration in the proposed scheme. Finally, the experimental study validates the effectiveness of the proposed scheme.

Flux Weakening Controller Design for Series-Winding Three-Phase PMSM Drive Systems

Series-winding three-phase PMSMs have a higher bus voltage utilization than the conventional three-phase PMSMs with star connection. This topology is suitable for applications with a limited bus voltage. However, the zero-sequence current controller will reduce the bus voltage utilization of the series-winding PMSMs, which causes problems in the flux-weakening controller design. The conventional flux-weakening control algorithms will cause the series-winding PMSMs to enter the overmodulation region early and degrade the performance of the zero-sequence current suppression algorithm. In this paper, a new flux-weakening controller with a dynamic fundamental voltage limit (FW-DFVL) is designed for the series-winding three-phase PMSM traction system. Firstly, the space vector modulation method combines the proposed virtual zero-sequence vectors to realize both the fundamental current generation and the zero-sequence current suppression. The accurate bus voltage utilization in the fundamental current subspace can be derived from the proposed modulation method. Secondly, the gradient descent method generates the flux-weakening d-axis reference current with the dynamic fundamental voltage, which will converge faster than the conventional PI-based flux-weakening control scheme. Thirdly, the flux-weakening controller in the overmodulation region is also designed where the zero-sequence current will no longer be suppressed. The bus voltage utilization is Vdc in this operation mode. Finally, both the simulation and experimental results are utilized to verify the effectiveness of the proposed FW-DFVL, where faster dynamic performance and higher bus utilization are observed.

Zero-Sequence Current Suppression Method for Fault-Tolerant OW-PMSM Drive With Asymmetric Zero-Sequence Voltage Injection

For the open winding permanent magnet synchronous motor (OW-PMSM) with leg open-circuit faults, a novel zero-sequence current (ZSC) suppression method with asymmetric zero-sequence voltage (ZSV) injection is proposed in this article. To realize the fault-tolerant control (FTC) in leg open-circuit fault conditions, the leg-sharing method is developed, where the output terminal of the faulty leg is connected to that of the remaining equivalent leg. However, the ZSC increases in the FTC mode, which causes severe torque ripple and system performance degradation. If the traditional ZSC suppression method is still adopted, the suppression performance is decreased. Besides, an undesired voltage vector is introduced, resulting in current distortion. To solve these problems, a novel ZSC suppression strategy is put forward. By asymmetrically adjusting the voltage output of the remaining legs, the ZSC of OW-PMSM in FTC mode can be effectively suppressed. Moreover, the proposed strategy is suitable for both the single-leg and double-leg FTC modes, where the ZSC suppression performance is almost the same as that of the traditional method in normal operation mode. Furthermore, experiments are performed on an OW-PMSM to verify the effectiveness of the proposed ZSC suppression scheme.

Simple Discontinuous Pulse-Width Modulation Scheme for the Loss Reduction of a Dual Inverter Fed an Open-End Winding Induction Motor

This paper presents a simple discontinuous pulse width modulation (DPWM) switching scheme to reduce the switching loss of a single DC-link dual two-level inverter fed an open-end winding (OW) induction motor (IM). The dual inverter system is attractive in many applications due to higher DC-link voltage utilization. Additionally, the OW motor has the potential fault-tolerant capability. However, the use of the dual inverter results in reduced system efficiency due to increased power losses in the inverter. Moreover, an OW motor inherently suffers from a zero-sequence current (ZSC) issue because the open neutral point of the stator windings provides the ZSC path. The ZSC causes negative effects in the system, such as an additional power loss and total harmonic distortion (THD). Thus, this work proposes an optimal DPWM scheme to reduce the inverter loss while suppressing the ZSC. Additionally, this work proposes a strategy to make the average power loss of each inverter equal. The performance of the proposed method is discussed in terms of switching power loss reduction and ZSC suppression. Simulation and experimental results are provided to verify the effectiveness of the proposed DPWM scheme.

Zero-Sequence Current Reduction Technique for Electrical Machine Emulators With DC Coupling by Regulating the SVM Zero States

In this article, a new zero-sequence current suppression technique for electrical machine emulators with reduced component count is proposed. The proposed control scheme is implemented by properly regulating the zero states in space vector modulation (SVM). It is well known that a machine emulator allows fast experimental validation of the control and design of a drive system without having a physical electrical machine, since the machine is replaced by another voltage-source converter and a three-phase inductor. However, in emulators with a coupled dc link, circulating zero-sequence current is freely developed creating additional load for the power switches. The currently available control methods require additional hardware common-mode filters to effectively reduce this current. Contrarily, the proposed SVM algorithm suppresses the zero-sequence current more effectively via direct compensation of common-mode voltage, and thus, no additional hardware filters are needed. Thus, an electrical machine emulator with less hardware requirements can be developed with the proposed control technique for being utilized in several laboratory test-bench applications. Experimental results on a 60-kW system validate the effectiveness of the proposed SVM algorithm, since the zero-sequence current amplitude has been measured to be 3.7% of the phase current or even less than this.

Phase Current Reconstruction of Open-Winding Synchronous Reluctance Motor Based on Edge-Alignment and Phase-Shift Strategy

This article proposes a phase current reconstruction strategy for open-winding synchronous reluctance motor (OW-SynRM) drives with the dual-inverter topology and common dc bus. The traditional reconstruction strategy cannot be applied in OW motor drives because the dual-inverter modulation and zero-sequence current suppression strategies complicate the vector combinations and shorten their durations. Besides, additional sampling is required because the sum of the three-phase current is not zero. To solve these issues, the edge alignment algorithm is proposed to extend the duration of certain vector combinations, and the phase-shift strategy for the third sampling is proposed to obtain extra current information. In the case of the reconstruction failure in immeasurable regions, the corresponding compensation strategy is investigated. With the proposed reconstruction strategy, the system cost can be significantly reduced and the reliability can be improved, where only one current sensor is required. Besides, the single sensor can be reused for power detection and protection for the whole system by selective installation. Moreover, the proposed strategy is compatible with both the 180° and 120° assignment schemes, increasing the flexibility of application. Finally, experiments are carried out on an OW-SynRM to verify the high accuracy and feasibility of the proposed strategy.

Research on Fault-Tolerant Operation Strategy of Permanent Magnet Synchronous Motor with Common DC Bus Open Winding Phase-Breaking Fault

In some key areas, fault-tolerant control is usually needed in order to enable the motor to operate continuously in fault mode. Given that it is difficult to detect the zero-sequence current of the open winding permanent magnet synchronous motor after the phase break fault occurs, the traditional zero-sequence current suppression strategy is no longer applicable after the phase break fault occurs. Therefore, a zero-sequence current suppression strategy for a common DC bus under a phase break fault is proposed in this paper. By establishing the mathematical model between the current component in the synchronous coordinate system and the current component and the zero-sequence current in the static coordinate system, the relationship between the non-fault phase current and the zero-sequence current in the open phase fault is analyzed. A method of suppressing the zero-sequence current by using proportional integral double resonance in a zero-sequence current control loop is proposed. In addition, according to the large number of calculations in traditional space vector modulation (SVPWM)—such as sector judgment and coordinate transformation—a decoupling modulation algorithm is proposed to modulate the reference voltage vector. Finally, the experimental platform for the common DC bus open winding permanent magnet synchronous motor is built, and the zero-sequence current suppression method for the common DC bus OW-PMSM under phase break fault is verified experimentally.

Three-Dimension Space Vector Based Finite Control Set Method for OW-PMSM With Zero-Sequence Current Suppression and Switching Frequency Reduction

The zero-sequence current (ZSC) of open-end winding permanent magnet synchronous motor (OW-PMSM) with common dc bus mainly comes from zero-sequence voltage (ZSV) and third harmonic back electromotive force, so the ZSV levels of voltage vectors in model predictive control (MPC) need to be considered to suppress the ZSC. Different from the conventional MPC methods for OW-PMSM, which usually select the optimal voltage vector under αβ0 coordinate system, this article proposes a three-dimension space vector (TDSV) based MPC method under ABC three-phase coordinate system for OW-PMSM with ZSC suppression and switching frequency optimization strategy. Benefiting from the three-phase voltages decoupling feature of OW-PMSM, TDSVs in ABC coordinate system are regularly distributed in a space cube. A simple optimal TDSV selection method is proposed based on subcubes division. TDSV contains the predicted α-,β-,0 -axis voltages information, so ZSC suppression is achieved automatically. Furthermore, utilizing the switch states redundancy feature of dual-inverter system, a cost function is designed to optimize the switch states change and reduce the switching frequency without affecting the optimal TDSV selection. The performance and switching frequency reduction effect of the proposed method are verified and compared with the existing methods through experiments.

Deadbeat Predictive Current Control for Series-Winding PMSM Drive with Half-Bridge Power Module-Based Inverter

Series-winding topology (SWT) could improve the DC-link voltage utilization, as open-winding topology does. Meanwhile, it can greatly reduce the number of power devices. Firstly, for the half-bridge power modules (HBPMs)-based inverter, an N-phase series-winding motor only requires N + 1 HBPMs for driving. On the other hand, such SWT also brings new challenges to the drive system. A zero-sequence loop is introduced into the motor windings due to SWT. The generated zero-sequence current would degrade the total harmonic distortion of the phase currents and produce the additional torque ripple. Moreover, current sensors are typically integrated with the HBPMs. However, in SWT, their measured results are the leg currents of the inverter, not the phase currents of the motor, which is crucial to the motor control. Thus, this paper mainly focuses on the aforementioned problems in a three-phase series-winding permanent-magnet synchronous motor (TPSW-PMSM) drive with HBPM-based inverter. Firstly, to control the zero-sequence subspace, the voltage vector distribution of TPSW-PMSM is analyzed. In addition, two voltage vectors with zero-sequence components are selected to generate the zero-sequence voltage. Then, the phase currents are reconstructed according to the leg currents from the current sensors on HBPMs. Based on the above, the deadbeat predictive current control (DBPCC) scheme is proposed for a TPSW-PMSM drive with HBPM-based inverter. It provides the TPSW-PMSM drive with fast dynamic response and effective zero-sequence current suppression. Finally, both simulation and experimental results verify the feasibility and effectiveness of the proposed DBPCC scheme.

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.

Sensorless Drive Strategy of Open-End Winding PMSM With Zero-Sequence Current Suppression

The open-end winding permanent magnet synchronous motor (OW-PMSM) with common DC bus configuration provides a path for zero-sequence current (ZSC). Apart from the zero-sequence voltage (ZSV) generated by inverters modulation, ZSC also comes from the third harmonic back-EMF. However, the third harmonic back-EMF contains the position information of the rotor, which can be extracted by an appropriate strategy to achieve position sensorless drive. In order to achieve sensorless drive and ZSC suppression simultaneously, this paper proposes a novel general-integral extended state observer (GI-ESO) based method. The third harmonic back-EMF of the OW-PMSM is estimated and calculated in three-phase stationary coordinate system by GI-ESO. And then, a single-phase phase lock loop observer (SPLL) is exploited to extract the position and speed information of the rotor. Meanwhile, the estimated third harmonic back-EMF is directly fed forward to SPWM as the ZSV reference, then the output voltages of the inverters contains the ZSV that can exactly counteract the third harmonic back-EMF, so as to realize the suppression of ZSC. Compared with the method of combining the fundamental back-EMF detection and proportional resonance (PR) regulator, this method can realize sensorless drive and ZSC suppression at the same time with only one scheme. Benefiting from the use of GI-ESO, the observer bandwidth can be relatively low, which helps suppress noise and extend the speed range of sensorless operation. Moreover, this method has strong robustness against motor parameters. The proposed strategy is validated by experiments.

3-D Vector-Based Model Predictive Current Control for Open-End Winding PMSG System With Zero-Sequence Current Suppression

In this article, 3-D vector-based model predictive current control (MPCC) for the open-end winding permanent magnet synchronous generator (OEW-PMSG) system driven by a dual inverter with a common dc bus is proposed to suppress the zero-sequence current. First, the 3-D voltage vector distribution of this system is analyzed and their zero-sequence voltages are investigated. Then, in order to reduce the computation burden of prediction control caused by vector enumeration, an improved current prediction control is developed, in which candidate voltage vectors for the dual inverter are determined according to the position of the zero-sequence reference voltage vector and the sector location of 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> -axis reference voltage vector. Moreover, to further improve the steady-state control performance of the whole generation system, a separate vector-selection method for the dual inverter is proposed. In this method, the first inverter applies one voltage vector in a control period and the voltage vector of the second inverter is synthesized by two vectors and selected in 3-D space. Finally, experiments are carried out to validate proposed methods, and the comparison experiments indicate that the proposed method has better control performance compared to conventional methods.

Three-Vector-Based Model Predictive Current Control With Zero-Sequence Current Suppression for Open-Winding LPMVM Drives

Because of the enhanced utilization of dc-link voltage and the low cost of power supply, common dc-link dual-inverter is a desirable drive topology to solve the low power factor problem of open-winding linear permanent-magnet vernier motor (OW-LPMVM). However, the common dc-link structure causes a zero-sequence current (ZSC) in the motor windings, which increases current distortion and thrust ripple of the LPMVM. To effectively decrease the ZSC as well as thrust ripple, this paper proposes a three-vector-based model predictive current control (TV-MPCC) scheme. In the proposed TV-MPCC, one optimal vector produced by one of the dual-inverter is obtained based on the deadbeat current control principle, which simplifies the prediction process and reduce the switching frequency. On the other hand, the other two optimal vectors produced by another of the dual-inverter are obtained by means of a cost function cascade evaluation, which improves the steady-state performance. With the proposed scheme, the ZSC is effectively suppressed with the simple implementation, enhanced thrust performance, fast transient response, good robustness against parameter variations, and reduced switching frequency compared with the existing ZSC suppression methods. Simulation and experimental results are demonstrated for confirming the proposed TV-MPCC.

Improved Direct Torque Control for Open-Winding PMSM System Considering Zero-Sequence Current Suppression With Low Switching Frequency

This article proposes an improved direct torque control strategy for open-winding permanent magnet synchronous motor (OW-PMSM) with common dc bus for zero-sequence current (ZSC) suppression. The proposed strategy builds a novel voltage vectors (VVs) look-up table, which keeps the simple control structure of the conventional DTC (C-DTC) and effectively suppresses the ZSC. In each control period, two VVs are selected. One is selected based on torque and flux control mode in the C-DTC strategy with two switching phases conducting for the whole control period; the other is selected to produce a suitable zero-sequence voltage based on the ZSC control with an additional third switching phase conducting for a short period of time. Since the duty cycle generation controller only adjusts the conducting time of one switching phase and the duration time of VV for the torque and flux control is not affected, the proposed strategy has low switching frequency and wide modulation range. Experimental results validate that the proposed strategy has a favorable control performance.

Zero-Sequence Current Suppression Strategy With Common-Mode Voltage Control for Open-End Winding PMSM Drives With Common DC Bus

The zero-sequence loop inherently exists in the structure of the three-phase open-end winding permanent-magnet synchronous machine (OW-PMSM) system with common dc bus, which provides the circulating path for zero-sequence current (ZSC) and consequently causes the torque ripple and extra system loss. Besides, the common-mode voltage (CMV), which can cause many negative effects, such as the bearing current and the failure of motor bearing, is another concern in the driving system. However, the simultaneous suppression of ZSC and the CMV control of the devices is investigated mainly in the application of the induction machine system and the multiphase OW-PMSM system, whereas it is ignored in the application of the three-phase OW-PMSM system, in which the suppression of ZSC is more complex considering the effect of flux linkage harmonic components. On this basis, this article proposes a strategy that can not only suppress the ZSC, but also eliminate the ripple of CMV in the three-phase OW-PMSM system. In the proposed method, the suppression of ZSC is achieved by synchronously adjusting the duration time of each phase within every control cycle based on the reference voltage of zero-sequence control loop, which can simplify the conventional rearrangement-based scheme. Furthermore, the duration time of each phase is distributed into each switch device of the two inverters, with the principle of eliminating the ripple of CMV. Consequently, both the suppression of ZSC and the CMV control can be achieved easily. Furthermore, the influence of dead time on the CMV control is analyzed, indicating that the CMV control is irrelevant with the dead time. Moreover, the effective modulation range of the proposed technique is analyzed. Finally, the experimental validation is conducted on a three-phase OW-PMSM system with common dc bus.