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A gallium nitride (GaN)-based resonant step-up converter is proposed for the application in the satellite electric propulsion (EP) system. This converter consists of a full-bridge inverter, a resonant tank and a multi-stage Cockcroft-Walton (CW) voltage multiplier to provide a high gain. Additionally, the air-core transformer is introduced due to the megahertz switching frequency allowed by the GaN device. Thus, the limited magnetizing inductance of transformer and the remarkable junction capacitance of diode have to be carefully considered in the resonant tank design, especially after considering that this converter normally operates at the light load in the EP system. In this work, the 4-order LCLC resonant converter is investigated. The recommended parameter selection for the 4-order resonant tank is also provided. A 1.2-MHz, 23-V/2.5-kV, and 6-W prototype is demonstrated. It achieves a low harmonics distortion and a low power loss with the zero voltage switching (ZVS).

The step-up resonant converter serves as an essential part of the ion propulsion power suppy (IPPS), which has been widely used in micro- and nano-satellites. However, the common-mode (CM) noise could deteriorate the converter performance, and hence it needs to be evaluated and mitigated. This work studies the CM noise of a 2 W, 500 kHz, 15-V/1.2-kV Gallium Nitride (GaN) based LCLC resonant converter. Based on the working principle of this converter, the CM noise current path is analyzed. In addition, an LCL filter is applied to evaluate its performance for CM noise suppression. The experimental and simulation results show that significant CM noise exists in the GaN-based step-up LCLC resonant converter from the frequency range of 150 kHz to 30 MHz, and the LCL filter realizes a good suppression for the CM noise.

Due to the advantages of high efficiency, low mass, modularization and high power density, the step-up resonant converter is widely adopted in providing kV-level high voltage for the ion propulsion power supply. As a key part of the resonant converter, the resonant tank topology is evaluated in this paper. Based on the characteristics of the high-voltage resonant converter, a selecting criteria for the resonant tank is proposed. Applying the criteria to the 2-element, 3-element, and 4-element resonant tank topologies, the candidate for high-voltage application can be recommended. Then, the selected topologies are compared based on the relationship between voltage gain and frequency. The analytical results show that the gain valley could be more easily founded in the 4-element resonant tank compared with others, thus it is more suitable for the high-voltage application.

GaN HEMT is a promising alternative of Si MOS-FET for the high-density power converter applications. Due to their lower switching losses, GaN HEMT may lead to new horizons in the application area of power electronics such as faster charger, wireless charging, and 5G power amplifier. However, evaluation of power loss and EMI of GaN HEMT versus Si MOSFET for the application in a synchronous low-voltage buck converter have not been comprehensively investigated. In this paper, the application boundary of 40-V, 10-A GaN HEMT is analyzed by comparing with Si counterpart has been assessed in terms of power loss, oscillation and EMI though the double pulse test. Based on the DPT results, it can be found that the switching energy of GaN HEMT is nearly 1/10 of Si MOSFET and also exhibits zero reverse recovery loss. Additionally, the impact of different switches on the converter performances is analyzed by the PLECS thermal simulation. It can be found that GaN-based converter shows lower efficiency at low frequency, and its efficiency is more seriously influenced by the dead time which is its application boundary.

Gallium nitride (GaN) high electron mobility transistor (HEMT) is a promising candidate for the high-efficiency and high-frequency motor drive applications when compared with the silicon (Si) counterpart. In this work, the GaN-based and Si-based devices based full bridge converters for DC motor drive are investigated and compared. Firstly, three different driving schemes including bipolar, unipolar and synchronous rectification are analyzed. Then, performance comparison between 40-V/l0-A GaN HEMT and Si MOSFET are conducted based on the datasheet and double pulse test experiment results. Finally, the model of DC motor drive is proposed based on PLECS thermal simulation. Based on the model, the impact of three schemes and two different switches on the efficiency is investigated. Results show the GaN-based full-bridge converter has higher efficiency and lower power loss.

The motor drive has been widely adopted in modern power applications. With the emergency of the next generation wide bandgap semiconductor device, such as silicon carbide (SiC) MOSFET, performance of the motor drive can be improved in terms of efficiency, power density, and reliability. However, the fast switching transient and serious switching ringing of the SiC MOSFET can cause unwanted high-frequency (HF) electromagnetic interference (EMI), which may significantly reduce the reliability of the motor drive in many aspects. In order to comprehensively reveal the mechanism of the EMI previously used in motor drives using SiC MOSFET, this paper plans to analyze the influences of both HF impedance of the motor and switching characteristics of the SiC MOSFET. A simulation model for motor drives has been proposed, which contains the HF circuit model of the motor as well as a semi-behavioral analytical model of the SiC MOSFET. Since the model shows a good agreement with the experimentally measured results on spectra of drain-source voltage of the SiC MOSFET (vds), phase to ground voltage of the motor (vphase), CM voltage (vcm), phase current of the motor (idm), and CM current (icm), it can be adopted to quantitatively investigate the influence of the motor impedance on EMI through frequency-domain analysis. Additionally, the impacts of switching characteristics of SiC MOSFET on EMI are also well studied according to relative experiment results in terms of switching speed, switching frequency, and switching ringing. Based on the analysis above, the relationship between motor impedance, switching characteristics of the SiC MOSFET, and HF EMI can be figured out, which is able to provide much helpful assistance for application of the motor drive.

With the superior features of lower cost and higher power density, the permanent magnet synchronous motor (PMSM) based adjustable speed drive (ASD) system has been paid much more attentions recently. A high-frequency (HF) model of PMSM is proposed to predict the conducted electromagnetic interference (EMI) emission, which brings much detrimental affection to the ASD system, in this paper. This model can depict the impedance characteristics of a three-phase surface-mounted PMSM from $0.1 \mathrm {k}\mathrm {H}\mathrm {z}$ to 10 MHz well. Then, experiment is implemented to validate the proposed HF model for EMI prediction. The experimental results manifest that the model is able to calculate CM voltage, CM current, and phase current of the PMSM in a simplified ASD system correctly. Therefore, the proposed HF model of PMSM is expected to provide much more instructions for EMI predicting in the ASD system.

Under the influence of high speed power switch device, electromagnetic interference (EMI) affects heavily the normal operation of the buck-boost circuit in hybrid energy storage system (HESS). In this paper, the working principle of the buck-boost converter in hybrid energy storage system is analyzed, and the relationship between common-mode (CM) voltage and the voltage of switching device is obtained. By analyzing the frequency spectrum of the voltage of switching device, the relationship between the switching characteristics and the system conducted electromagnetic interference is proposed, and the prediction model of the conducted electromagnetic interference for hybrid energy storage system is established. In addition, the mechanism of ringing and overshoot during switching time of switching devices is studied and reduced by the method of adding capacitor, and experimental results validate the analysis method.

In this paper, top joint method is proposed to solve a practical engineering problem of temperature stress and temperature crack of super-long slab-column structure bearing temperature difference. From the study, it is shown that as for super-long slab-column structure undergoing temperature difference of inside and outside, joint located in bottom stories nearly has no influence on temperature stress and deformation while joint in top stories can significantly reduce temperature stress and deformation of super-long slab-column structures. In addition, comparison of joints located in top one story, top several stories and from bottom to top stories indicates that influences of them on temperature stress and deformation are similar. As for top joint method, among which cantilever plate method, double column method and corbel method are discussed and results indicate that influence effects of these methods on structures are similar.