The power conversion system (PCS) serves as the core device for power transfer between energy storage systems and the grid, effectively dispatching electricity generated by intermittent sources like renewable energy to match load demands. Conventional grid-connected PCS architectures typically employ PI regulators for closed-loop control of the power outer-loop and current inner-loop. However, this approach cannot effectively suppress disturbances caused by parameter command variations and grid condition changes. Consequently, traditional PCS systems exhibit degraded quality in grid-connected output current during power command transients or sudden changes in grid voltage amplitude and frequency. To address these issues, this paper proposes a dual-loop control method for PCS based on the Uncertainty and Disturbance Estimator (UDE). The dual-loop parameters of the UDE control are systematically designed. Simulation and experimental results verify that the proposed control method significantly enhances the disturbance rejection capability of the PCS. The experimental results show that the response time of the PCS using the UDE controller can be reduced by more than 50% compared with that using the PI controller.

The four degrees of freedom (4-DOF) 12/4 bearingless switched reluctance motor (BSRM) generally requires 48 power devices, 24 current sensors, and 2 microchips to simultaneously achieve rotation and levitation. To reduce the number of power devices and sensors used in the system, a split-phase converter and a multiplexed-sensor method are employed. However, significant voltage deviation occurs on the two split-phase capacitors due to the inconsistent levitation currents, which deteriorates the levitation performance. Therefore, this paper proposes a magnetic-flux balance control (MFBC) method to solve this problem. The method constrains the total current of all windings in each phase to form a balanced bias magnetic flux. By balancing the discharge depth of the two split-phase capacitors, voltage deviation is eliminated and stable levitation operation is ensured. Moreover, an improved multiplexed-sensor method is developed to enhance levitation stability at high speeds. Finally, the demonstrated performance of the proposed scheme is verified on a test rig of a 4-DOF 12/4 BSRM-type magnetic levitation system.

The power-off protection mechanism of the maglev system is particularly important in the field of aero-space.When a high speed running rotor disengages from active control due to a sudden power-off,the Permanent Magnet Synchronous Motor(PMSM)in the levitation system must immediately switch to an energy feedback power supply mode to maintain levitation stability.This process,however,induces transient inrush currents far exceeding rated values through electromagnetic coupling,leading to risks such as power device breakdown and motor winding in-sulation damage.To suppress the inrush current,this paper proposes an inrush current suppression strategy based on feeding voltage trajectory planning.By establishing a feeding mathematical model of PMSM driven by a three-level Neutral Point Clamped(NPC)converter,the mechanism of inrush-current generation is analyzed,and a segmented given voltage method based on trajectory planning is designed.Experimental results confirm that the proposed strat-egy achieves 42%and 47%reductions in no-load and loaded inrush currents within a controllable switching time.Compared with conventional"ramp"-and"S"-curves trajectory planning strategy,the proposed segmented given method based on trajectory planning achieves a better balance between the target voltage response speed and inrush current magnitude suppression,effectively mitigating the conflict between these two competing objectives.

The conventional levitation control strategies for bearingless switched reluctance motors (BSRMs) depend on accurate mathematical models and exhibit weak rejection of displacement disturbance. To solve this problem, this paper proposes an improved direct displacement control (DDC) with second-order uncertainty and disturbance estimator (UDE). Unlike most UDE applications in first-order systems, this work establishes a complete second-order UDE design framework. Firstly, the reference trajectory for displacement is established. Next, the lumped disturbances, including uncertainties and external disturbances, are estimated by a low-pass filter. The estimated value is fed forward into the control loop to directly adjust the differences of winding currents on the opposite poles through the displacement errors. Then, the differences are superimposed on the bias currents to obtain the desired currents of each winding. Therefore, the BSRMs, which possess disturbance rejection capability, only need to track the desired currents to gradually drive the displacement to converge to its reference trajectory. Finally, the demonstrated performance of the proposed strategy is verified on a test rig of 12/4 BSRM-type magnetic levitation system with four degrees of freedom (DOFs).

This article establishes a multi-VSG parallel admittance model based on the control foundation of virtual synchronous generator (VSG). First, a detailed study is conducted on the influence of line parameters on the stability and oscillation mechanism of parallel systems, based on existing references. Second, a power-angle compensation control is designed using the equal-area method to enhance transient stability and is supported by power-angle equations that reveal dynamic interactions. Finally, for multi-VSG systems with parameter discrepancies, a phase-angle decoupling coordination strategy is proposed to eliminate cross-coupling in phase angle control loops. This improves regulation accuracy of phase deviations and suppresses transient/steady-state oscillations while optimizing power sharing. This strategy demonstrates superior stability margins over conventional methods after parameter-design via return-difference matrix singular value analysis and stability-verification through generalized Nyquist criterion. Simulations and experiments confirm enhanced dynamic and steady-state performance, addressing the fundamental synchronization issue in parallel systems.

Notch filters (NFs) are widely applied in the five-degrees of freedom (5-DoFs) magnetic levitation motors to reduce the vibration near the resonant frequency. However, due to the existence of axial thrust disk, rotor masses at the two ends of the shaft are generally different. It not only increases the difficulty of NF design, but also reduces of fatigue life of rotor system. Therefore, a cross displacement control (CDC) method is proposed in this paper to synchronize the displacements at the two ends, which reduces the number of NFs and improves the fatigue life of rotor system. Simulation and experimental results show that the fatigue life of rotor system can be improved by 17.70 times, 21% and 10% at 4000 r/min, 10000 r/min and 20000 r/min, respectively. On the basis of that, the phase-shift NF can also be added to reduce the vibration near the resonant frequency. Experimental results verify that the fatigue life of rotor system can be improved by 26.5% near the resonant frequency with proposed strategy, and the adjustable time of displacement can also be reduced by 51.7%.

In this paper, a direct power control (DPC) strategy with virtual synchronous machine (VSM) mechanism is proposed for a two-stage AC-DC converter-based battery charger. In the proposed method, the absorbed power from the AC grid or the battery charging power can be controlled to track the reference values directly. To ensure power balance between the source (AC-grid) and load (battery), the corresponding DC-side power compensation and AC-side power compensation schemes are proposed respectively without estimating the power losses in realtime. As compared with the traditional VSM-based control strategy, the DC-bus voltage closed-loop controller is not required so that the bus-voltage sensor can be removed in the hardware. As the core algorithm of the VSM scheme is still adopted in the control of the front-end AC-DC converter stage, this method can achieve accurate and stable power control, while retaining the ability of VSM to regulate the frequency and voltage of the power grid. The feasibility of the proposed method is evaluated through systematic analysis and validated experimentally on a developed test-bed.

The radial support of five-degree-of-freedom (5-DOF) magnetic levitation systems typically relies on radial magnetic bearings (RMBs). Replacing RMBs with bearingless switched reluctance motors (BSRMs) provides both levitation force and torque, enhancing integration and functionality. Conventional BSRMs often require dual windings and complex drives, limiting their compactness and integration. To address this challenge, an integrated BSRM is proposed, where conventional stator and rotor cores with a single winding simultaneously realize rotation and radial levitation. A design methodology for the integrated BSRM topology is introduced, and an evaluation framework combining theoretical modeling and finite-element analysis identifies the 12/4 topology as best-balanced among the evaluated candidates. To minimize converter size and improve system integration, a minimum-device drive topology is developed, accompanied by a unified current control strategy coordinating torque and levitation. Finally, a 12/4 integrated BSRM prototype is experimentally compared with an RMB-based system, demonstrating RMB-comparable levitation while delivering torque capability.

In the speed regulation system of a permanent magnet synchronous motor (PMSM), the open circuit of a power device is the most common type of fault but is not easy to detect. With the fault, the control precision and output performance of the system decrease. To reduce the risk of fault contagion and ensure the safety and reliability of the system operation, this paper focuses on open-circuit fault diagnosis and fault-tolerant control. First, based on the defects of the long diagnosis time and poor adaptability to speed and load changes of the average current method, which is commonly used in engineering practice, an online fault diagnosis strategy that utilizes changes of the sector width is proposed. Experimental results demonstrate that the diagnosis time can be shortened to one electrical period or less. Meanwhile, extra sensors are not required to assist in the fault diagnosis, greatly reducing the volume and cost of the whole drive system. After that, to verify operation with a fault, a three-phase four-leg inverter is introduced in this scheme, which uses the advantage of the hardware redundancy of the three-phase four leg to reduce the difficulty of fault-tolerant control. A reliability comparison between three-phase bridge and three-phase four-leg topology is analyzed in detail using the Markov model, and the fault-tolerant performance of the latter is verified by experimental results.

In traditional model predictive torque control (MPTC) of switched reluctance motor (SRM), it is necessary to traverse multiple switch state combinations, which may result in complex calculations. To solve this problem, a torque compensation-based MPTC for SRM with switching states restructuration is proposed. The strategy is optimized by the following two aspects: Firstly, a 9-sector switch state allocation method is adopted, which considers the problem that the actual torque cannot instantly track the reference torque in the initial excitation area of the incoming phase, as well as the problem of negative torque caused by the slow decrease of terminal current. By optimizing the switch state combination rules through partitioning, the number of candidate switch state combinations is reduced from 27 to 2 or 4. Secondly, the proposed MPTC integrates a torque compensation algorithm with torque sharing function (TSF), which selects phases with better torque tracking ability for torque compensation and adjusts the allocation of compensation modes through dynamic position updates. The experimental results show that compared with traditional current chopping control (CCC) and other MPTC schemes, the proposed MPTC can effectively reduce computational burden and ensure better torque ripple suppression effect.

In this article, a sensorless finite-control set model predictive torque control (MPTC) strategy is proposed for switched reluctance motor (SRM) drives. To minimize the switching vector candidates and relieve the computing pressure in traditional MPTC methods, the flux linkage closed loop is adopted to assist candidate vector screening. In the controller, the flux linkage of each phase is calculated via the flux integral with the terminal voltage and phase currents. Through alpha-belta transformation, the rotating flux angle and rotational speed can be estimated via phase locked loop. As the rotor position angle is synchronizing with the rotating flux angle, thus can be estimated directly by compensating the angle bias between them. The estimated position angle can be used for modeling the flux linkage and deriving the predicted torque, which is utilized in constructing the cost function in the MPTC method. Based on the aforementioned control process, the position sensorless control can be fully achieved. The experiments are performed under a 12/8 SRM test-bed, which verify the validity of the proposed method.

High performance and reliability are critical for the starter-generator system in multi-electric aircraft engines. Therefore, a five-DOF magnetic levitation starter and generator system of dual three phase bearingless permanent magnet synchronous motor (DTP-BPMSM) is proposed in this paper, which allow for the integration of functions such as starting, generation, fault tolerance, and levitation. In addition, this paper explores the operating principles and establish levitation force mathematical models of the DTP-BPMSM. Finally, the levitation force mathematical model is validated through simulation, and closed-loop control is implemented.

The traditional DTC method directly controls the torque and flux linkage without model calculation, which is beneficial to restraining torque ripples. However, the LRSRM not only provides the torque required for rotary motion, but also provides the axial force required for linear motion. Hence, the winding usually works in two-phase excitation mode. Given the different torque output capabilities of the front and rear phases under different rotor position angles, the conduction angles of the adjacent two phases can be further optimized. In this paper, a phase commutation optimized method is proposed to improve the torque generation between two neighboring phases and reduce torque ripple. Firstly, the hysteresis-loop control of the flux linkage is removed, which can reduce the calculation burden of digital controller. Secondly, the sector division and voltage vector selection without flux hysteresis control are redesigned. Experimental results verify the effectiveness of the proposed method. The phase current in negative torque region is reduced, and the torque ripple is suppressed as well.

In the five-degrees of freedom (5-DoF) magnetic levitation system, passive axial forces (PAFs) usually occur when stator and rotor are not aligned axially during levitation, which tends to pull the rotor back to the balanced position and is benefit for the reduction of axial displacement ripple further. However, they are generally ignored in conventional axial levitation control of 5-DoF magnetic levitation permanent magnet synchronous motors (PMSMs). This paper analyzes the influence of PAFs on axial displacement, and improves the conventional control. Besides, coil-current fluctuation of radial magnetic bearings (RMBs) and motor can also result in PAF ripples, which increases the axial displacement ripple further. On the basis of it, the influence of RMB coil-current fluctuation on axial displacement is analyzed, and a feedforward compensation strategy is also proposed to reduce the axial displacement ripple. Experimental results show that the axial displacement ripples are reduced by 38.6% and 37.3% at 0 r/min and 20000 r/min with improved control, respectively. Further, the axial displacement ripples are also reduced by 37.8% and 27.7% at 0 r/min and 20000 r/min with the proposed strategy, respectively.

The torque and levitation force in a single-winding bearingless switched reluctance motor (BSRM) are generally generated by the windings of each phase simultaneously. However, the commutation of the BSRM results in significant decrease and ripple of the levitation force due to the lower current rising rate at high speeds, requiring advancements in the existing levitation control to ensure stable levitation. To compensate for this deficiency, this article reallocates the conduction intervals of the levitation force while ensuring torque performance. By extending the conduction period, the levitation force for each phase is allocated based on the proposed levitation-force sharing function (LFSF). In addition, an online correction algorithm is proposed to adjust the reference levitation force of the previous phase, which can smooth the levitation force at the beginning of next-phase conduction. The improved LFSF exhibits better adaptability to speed variation. Finally, the feasibility of the proposed strategy is verified on a test rig of 12/4 BSRM.

Magnetic bearings (MBs) are widely applied in high-speed permanent magnet synchronous motors (PMSMs), which can avoid the friction loss and mechanical vibration by levitating the shaft. However, there is no active stiffness on the rotor of PMSMs, which can also generate the unbalanced magnetic pull (UMP) and vibration due to the changing air gap between stator and rotor. Further, it can deteriorate the stability of magnetic levitation system. Therefore, a negative stiffness injection method for PMSM in five degrees of freedom (5-DoF) magnetic levitation systems is proposed in this article, which is realized by injecting negative d-axis current to weaken the UMP and without other windings or equipments. Simulation and experimental results both verify that the multifrequency vibration accelerations are greatly reduced and the operation safety of magnetic levitation system is improved. Moreover, the proposed method is benefit for PMSM to pass the resonant frequency safely as well.

Considering the mechanical coupling, the displacement cross-coupling control is applied to the magnetic levitation PMSM system operating. The proposed approach effectively restrains levitation displacement, and the control algorithm is simple to implement. The stability margin of multi-input multi-output system is evaluated by the singular value method of system return difference matrix, which verifies that the stability of the proposed algorithm is better. Finally, simulation and experimental results show that the displacement fluctuation can be reduced by a minimum of 15%, at the resonance frequency.

A displacement sensor is one of the important components in the high-speed magnetic bearing system, which directly influences the control accuracy. Traditional magnetic bearing systems rely on multiple eddy current sensors with high displacement measurement costs and low integration. To address this issue, this article proposes a transverse flux displacement sensor based on printed circuit boards (PCBs). This sensor integrates three axial-radial degrees-of-freedom measurement within a single compact structure, demonstrating sensitivity of 5 V/mm in axial direction and 4 V/mm in the radial direction with linearity errors below 3% across all measurement axes. Through experimental validation, the coupling between axial and radial directions was measured at 47%, which was subsequently reduced to below 13% via the decoupling method. The integration of these performance metrics highlights the sensor's advantages of good sensitivity, compact size, and cost-effectiveness compared to traditional multisensor configurations.

The radial levitation displacement control strategy for four-degree-of-freedom (4-DOF) bearingless switched reluctance motor (BSRM) conventionally depends on the accuracy of the analytical model. However, the analytical model of BSRM is difficult to precisely formulate. In this paper, a controller with uncertainty and disturbance estimation (UDE) capabilities is utilized to directly establish the displacement-current control loop. This method estimates the parameter perturbation and external interference changes of the system through filters and feedforward compensates them into the control loop, which reduce the dependence on the accurate analytical model. Simulation results show that the proposed method improves the steady-state accuracy of levitation displacement and has good suppression ability for step and periodic disturbances.

Accurately extracting the electromagnetic radiation signal of the equipment to be tested from the environmental electromagnetic signal is one of the difficult problems that urgently need to be solved when conducting electromagnetic compatibility on-site testing. Virtual darkroom technology can accurately receive radiation information from the tested equipment in a noisy environment. However, there may be significant errors in the test results when there are strong interference signals. Based on the principle of spatial cancellation, this paper proposes a new method for suppressing background electromagnetic interference. This method combines the idea of simultaneously cancelling background noise in a virtual darkroom with the introduction of array signal processing, and uses beamforming as the operating mode to filter out background noise in on-site testing. This algorithm can overcome the shortcomings of traditional methods, that is, it does not need to assume that background noise is not related to the radiation signal of the tested equipment, the spatial distribution of background noise is uniform, and the signal-to-noise ratio is large. By providing less prior information or reference information of the on-site environment, good results can be achieved. Its core is high-precision direction of arrival estimation through multiple signal classification algorithm (MUSIC). After obtaining the direction of the signal, the Linear Constrained Least Variance (LCMV) algorithm is used to weight the signal received by each antenna. The weighted sum of each antenna suppresses background noise and preserves the radiation signal of the tested equipment intact. Finally, the correctness of this method was verified through an example.