With the advancement of active magnetic bearings, improving system reliability has become a major research focus. Fault diagnosis, a critical aspect of reliability enhancement, still offers considerable potential for optimization, particularly in terms of diagnostic time. This paper presents a rapid fault diagnosis method for power devices, capable of detecting both open-circuit and short-circuit errors, by utilizing the switching states of power devices in conjunction with multi-current-sensor data fusion. An auxiliary current sensor is integrated into the DC bus circuit. The proposed method can identify fault types and potential locations in power amplifiers within a single switching cycle by presetting coil switching states, employing oversampling, and comparing current data. Specific diagnostic criteria are established through modifications to the modulation mode, allowing for the localization of the exact fault position. The diagnostic process requires only one to five switching cycles, resulting in more than a 70% reduction in diagnosis time compared to conventional methods. Experimental results validate the effectiveness of the proposed approach.

In high-power applications, pulse width modulation (PWM) techniques are widely adopted to achieve superior motor control performance, yet they inevitably introduce significant electromagnetic interference (EMI) issues. This paper first illustrates the principle of harmonic suppression through carrier phase-shifting (CPS) strategy, then leverages the multiple degrees of freedom in a four-module drive system to optimize the strategy, enabling selective additional EMI suppression in targeted frequency bands. Subsequently, a hybrid modulation strategy combining CPS strategy and uniformly distributed pulse width modulation (UDPWM) is proposed and its feasibility is experimentally validated. This approach demonstrates the capability to achieve further reduction in EMI. Experimental result shows that the proposed hybrid modulation strategy can achieve up to 20 dB EMI suppression.

For the ISOP-based Dual Active Bridge (DAB) converter, zero common-mode (ZCM) voltage can be achieved under a symmetric topology, while ensuring that the power balance control of the system remains unaffected. In this scenario, the DAB can utilize the extended phase shift (EPS) modulation. The combination of phase shift ratios in EPS has a significant impact on the system's performance. This study focuses on optimizing the backflow power, under the constraints of zero-voltage switching (ZVS) and zero common-mode voltage. The phase shift ratios are optimized to reduce current stress, enhance efficiency, and further mitigate electromagnetic interference (EMI) above the MHz range. The effectiveness of the proposed optimization method is validated through theoretical analysis and experimental results.

Active magnetic bearing (AMB) is an advanced contactless bearing system for high rotation speed equipment but cannot work stably without closed-loop control. Normally multiple proportional integral derivative (PID) controllers are used to control the multiaxis AMB system. However, existing AMB PID controller tuning methods mainly focus on optimization and cannot turn an AMB system from unstable to stable. In this article, a model-free AMB PID tuning method is proposed to solve this problem for the first time, which imitates an experienced AMB engineer and utilizes physical information from runtime data. The effects of varying PID controller parameters on rotor displacements are analyzed in the time domain and meta-parameters are proposed to describe the parameters' performance. The effectiveness of the proposed tuning method is supported by the time-domain analysis and is also verified through experiments. For an unknown and untuned AMB system, the proposed tuning method provides a parameters solution in a short time with acceptable performance. With the tuned AMB system provided by the proposed tuning method, further works like system identification or optimization can be carried out more easily.

This paper proposes a variable-topology motor drive with soft-shifting method for PMSM operating range extension. To satisfy both heavy-load and high-speed requirement, smooth online conversion between half-bridge topology and series-winding topology is achieved by considering shift transient control. The shift circuit is special designed and the step-by-step shifting method is proposed to avoid the output torque interrupt during the shifting process. By actively controlling and injecting the 0-axis current, the proposed zero-current shifting method solves the reliability issues of shift switches, avoiding the overvoltage and electric spark in electromagnetic relay. The experimental results have verified that the proposed variable-topology motor drive can significantly extend the speed range and achieve high efficiency and high torque capability in the global operating region, while the online topology conversion process using the soft-shifting technology has little effect on the motor operations.

In ac–dc power conversion system, modular multilevel converter (MMC) has been a promising technology, especially for high-voltage application. In such kind of application, the common-mode voltage (CMV) generated by power electronic switching can cause damage to electrical components and increase the electromagnetic interference (EMI) to the system. Hence, this article proposes a modulation scheme to reduce the CMV of MMC applied in high-voltage system, such as high-voltage dc. Usually, MMC consisting of numerous submodules (SMs) adopts the nearest level modulation (NLM) with the low switching frequency, so the CMV of the NLM scheme is analyzed, which indicates that the peak value of CMV is one-third of SM voltage. If one more or one less SM is turnedoncompared with NLM, the CMV caused by modulation can be eliminated theoretically. Subsequently, a modulation scheme based on the nearest zero CMV vector (NZCMVV) to reduce CMV is proposed for MMC. The NZCMVV scheme utilizes the two adjacent levels as candidate levels, and the theoretical ZCMVVs are picked out. Finally, the ZCMVV closest to the reference vector is selected to approximately replace the reference. The proposed method is simple and easy to implement. Simulated and experimental results validate that the proposed scheme can reduce CMV and CM current compared with the traditional NLM method.

In DC-biased sinusoidal current vernier reluctance machines (DC-biased-VRMs), the DC exciting winding and AC armature winding are integrated into one single winding. Therefore, the copper loss can be reduced with torque density increasing, and only one set of power electronic converter is demanded. This paper is to propose a DC-biased-VRMs drive with asymmetrical power electronics devices and corresponding control strategy. In order to make the power dissipation and temperature rise of each devices more balanced, the asymmetrical H-bridge inverter with both higher current capacity devices and lower ones is designed as well as simulated. The proposed asymmetrical H-bridge can reduce the cost of power electronics devices effectively due to the use of lower current capacity IGBTs and diodes without unipolar current constraint. The simulation and experimental results verify that the proposed drive system is feasible for DC-biased-VRMs driving.

This paper introduces a paralleled three-phase four-leg inverters and the corresponding pulse width modulation (PWM) method for the purpose of reduction the common mode current (CMC) and common mode electromagnetic interference (EMI). Considering the control principle of three-phase four-leg to limit the common mode voltage and the characteristic of paralleled inverters, the simple PWM scheme for paralleled three-phase four-leg inverters can be deduced. In the modified topology, the low frequency and high frequency models can be set up to determine the load parameters of the extra phase. The results based on MATLAB SIMULINK and experiments are provided to validate the proposed method.

In order to optimize aircraft performance and decrease operating and maintenance costs, traditional aircraft is moving towards a more electric aircraft. Moreover, integrated starting/generating system is one of the key components in a more electric aircraft. To determine whether starting/generating system meets the intended requirements, it is necessary to test the system. Herein, this paper is going to present a power converter-based test platform to replace traditional test benches for the considerations of flexibility, costs and safety. Firstly, applications and advantages of power converter-based test platform are illustrated. Secondly, the structure of power converter-based starting/generating system emulator is proposed. Next, operating principle of the emulator is comprehensively illustrated. Finally, MATLAB/Simulink based simulation model is build up to evaluate the proposed power electronics emulator for both starting and generating performance. The simulation results can support the working principle of the power electronics emulator and could be used for prototype development.