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The bidirectional CLLC resonant converter has distinguished potential in battery chargers and energy storage systems for its advantages in soft switching and bidirectional power flow capability. However, traditional CLLC converters generally adopt symmetrical design to maintain bidirectional symmetrical characteristics, which means the secondary LC network is designed to be equal to the primary LC network after reflection. The symmetrical design is only suitable for voltage grade matching scenarios where a wide voltage range is not required, such as CLLC-type dc transformers. Whereas in the field of bidirectional chargers, due to the wide voltage range of battery, there are significant differences in the characteristics required between charging and discharging mode, which makes symmetrical design no longer applicable. To cope with this issue, this paper proposes a novel design methodology of CLLC based on parameter equivalent and time domain model. With the parameter equivalent principle, the CLLC resonant tank with arbitrary parameters is investigated to satisfy the requirements of wide voltage range for bidirectional charger application. Compared with the symmetrical design, the proposed method can meet the requirements of bidirectional gain within preset frequency range and guarantee the achievement of zero-voltage switching under required load conditions with the minimum reactive power. In addition, the area product capacity of the magnetic part of the CLLC resonant tank is minimized based on the parameter equivalent principle. Finally, experiments have been performed on a 1 kW prototype to confirm the validity and feasibility of the proposed design methodology. [ABSTRACT FROM AUTHOR]

Compared with silicon insulated-gate bipolar transistor, silicon carbide (SiC) metal–oxide–semiconductor field-effect transistor (mosfet) presents good features that it clearly shows on its switching and thermal performance. However, the fast switching speed of SiC mosfet makes it much more difficult for solving the dynamic voltage imbalance problem caused by the parameter fluctuations of the SiC mosfets and drive circuits when they are connected in series. This article proposes an effective gate drive circuit and its dynamic voltage balancing control method to tackle this issue. The proposed method not only balances the dynamic voltage during high-speed switching but also adapts to the variation of the dc-bus voltage by utilization of overdrive control method (ODCM). Furthermore, to widen the control range of the ODCM, a switched-capacitor compensation method by switching and combining different drive capacitors into different values is proposed. The operation principles and the parameter design method are discussed in detail. The performance of the proposed series-connected SiC mosfets gate drive circuit and its dynamic voltage balancing control method is validated by experimental results. The dynamic voltage can be well balanced within the design range. [ABSTRACT FROM AUTHOR]

This paper presents a new active gate drive (AGD) for switching performance improvement and overvoltage protection of high-power insulated gate bipolar transistors (IGBTs). In addition to the conventional gate drive (CGD) based on fixed voltage sources and fixed gate drive resistors, the proposed AGD has a complementary current source to provide extra gate drive current into the gate. Specific transient switching stages of the IGBT can be therefore accelerated, leading to higher switching speed and lower switching loss of the IGBT. Additionally, the turn-off voltage overshoot of the IGBT can be controlled at a preset reference value with a fast closed-loop overvoltage protection circuit. Moreover, the switching speed of the IGBT, including the turn-on/off delay times and the turn-on/off voltage slopes, can be effectively regulated with an adaptive switching speed control method. Accordingly, the gate drive is capable of operating the IGBT at specified delay times and fixed voltage slopes when varying the switching conditions (e.g., temperature, load current). The operation principle of the proposed AGD and control concept are presented. By comparing with the CGD, the proposed method is experimentally verified on a 3.3 kV/1.5 kA IGBT module in both double-pulse and multipulse tests. [ABSTRACT FROM PUBLISHER]