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EMI Modeling and Experiment of a GaN Based LLC Half-Bridge Converter
Mofan Tian,Yuan Hao,Kangping Wang,Yang Xuan,Lang Huang,Jingjing Sun,Xu Yang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper focuses on the electromagnetic interference (EMI) research and analysis of the MHz switching frequency GaN MOSFET based on the LLC resonant DC-DC converter. In this paper, first, the CM coupling paths are studied to get simplified models. Then the impact of the parasitic capacitors (both the capacitors to the ground and the capacitors in the devices) on the CM current are analyzed. Finally the high frequency model is derived from the work above. Moreover this paper makes the comparison between normal Si MOSFET and GaNbased MOSFET behavior in EMI. The modeling result proves that GaN MOSFET has a worse behavior on EMI test. An experiment layout which is aimed at minimizing the irrelevant factors is designed and the experiment result proves the accuracy of the modeling.
Design and Implementation of a High Power Three-Level T-Type Inverter for a Photovoltaic System
Yang Xuan,Mofan Tian,Xiaomei Song,Wenjie Chen,Xu Yang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Nowadays, the grid-connected photovoltaic systems are an important part of the renewable energy sources, and their performance is getting more and more important. Many reported researches focused on the traditional NPC topology. However, few researches were about the T-type NPC inverter. In this paper, a high power three-phase T-type neutral point clamped grid connected photovoltaic inverter prototype is designed and implemented. The design and implementation procedure of the inverter is discussed in detail. Experimental results showed that the output power of the proposed inverter could reach up to 100kW with unit power factor, while the total harmonic distortion of the grid current was less than 3%. And the total efficiency of the system is measured as 95.6%. The experimental results demonstrated the T-type NPC inverter can operate with a good performance.
Active Gate Charge Control Strategy for Series-Connected IGBTs
Fan Zhang,Yu Ren,Mofan Tian,Xu Yang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Since the voltage blocking capability of a single insulated gate bipolar transistor (IGBT) is limited, series-connected IGBTs are used in power electronic converters to satisfy the requirements of high-power and high-voltage applications. However, due to the parameter differences of the series-connected IGBTs, it is difficult to ensure an equal voltage sharing between the devices during both transient and steady-state operations. This paper proposes a novel active gate drive which operates basing on the active gate charge control strategy. The proposed active gate drive is able to achieve both minimized power loss and proper voltage sharing between the series-connected IGBTs. The active gate charge control strategy has been validated by simulations, and promising results have been obtained.
Yang Chen,Yaqi Sun,Mofan Tian,Laili Wang,Haoyuan Jin 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Dielectric elastomer (DE) is a kind of capacitive material that widely used in soft robots’ applications as actuators. To obtain notable deformation, the drive voltage is typically up to several thousand volts and the charging charges must be removed to make it recover. In this paper, a high step-up capacitive load bi-directional flyback converter with active clamp technique is proposed. For the charging process, the effects of increasing high output voltage and parasitic elements in the circuit on the operation of the active clamp circuit are discussed in detail. Wide bandgap devices are used at the secondary side to reduce the parasitic capacitance. The proposed lossless active clamp circuit can absorb the energy in leakage inductance of transformer and achieve zero-voltage-switching (ZVS) over most of the charging process. Besides, the EMI problem caused by leakage inductance of conventional flyback converter is also solved. A prototype with 12V input and 1000V output has been fabricated and compared with a quasi-resonance flyback (QR flyback) at the same working condition. The tested results verify the good performance of the proposed ACF converter.
Analysis and Design of LLC Resonant Converters Operating in Reverse Mode
Angyang Zhou,Xu Yang,Mofan Tian,Naizeng Wang,Laili Wang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this paper, the reverse operating characteristics of LLC resonant converters from fr/2 to fr are explored. The reverse voltage-gain and the conditions for zero-voltage switching (ZVS) of the reverse LLC resonant converter are summarized, and the frequency interval is obtained according to the magnitude of the turn-off current. The accuracy of the above analysis is verified by experiments. The research on the reverse operating characteristics of LLC resonant converters has practical significance in some special applications especially when require for the bidirectional operation.
Lang Huang,Xu Yang,Bin Zhang,Liang Qiao,Hongchang Li,Mofan Tian 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The modular multilevel matrix converter (M3C) applied to a low frequency alternating current (LFAC) transmission system is investigated. Due to the complexity and tight coupling of the converter, a novel hierarchical model predictive control (MPC) scheme with a cascaded structure of power control, capacitor voltage averaging and balancing control for M3C is proposed. The terminal behavioral model of M3C is derived out and the fast separated space-vectors approximation method is realized. The proposed scheme clearly achieves the system-level multi-objective control without the empirical procedure of the weighting factor design and significantly reduces the computational cost. This is the first time to apply the MPC to a converter in a hierarchical structure. Simulation results of a 7-level M3C are provided to illustrate the system’s performance.