在电力电子变压器和直流配电网等领域,需要采用DC/DC变换器双向传输能量。为了适用不同电压等级电网,研究适用于ISOS拓扑的双向DC/DC变换器,采用双向LLC谐振实现能量双向流动时开关器件的ZVS和准ZCS,使用均压电阻实现系统的稳态均压。首先描述双向LLC谐振变换器的工作波形,然后采用基波分析法对电路的增益特性进行分析。将适用于ISOS拓扑的增益特性及软开关的实现条件作为双向LLC谐振网络设计的依据,并对高频隔离变压器和ISOS拓扑的均压电路进行分析与设计。最后研制2个6.25 k W的变换器,对所提出的设计方法进行验证。试验证实变换器能够实现能量双向传输时开关器件的ZVS和准ZCS,并且能量双向流动时变换器具有相同的增益特性,同时变换器的串联不均压度小于3%。
Bidirectional DC/DC converters are required in the field of power electronic transformers and DC power distribution networks. In order to apply in different DC distribution grids, the topology of ISOS based on bidirectional DC/DC converters is studied in this paper. The ZVS and ZCS are realized by using LLC resonance in bidirectional energy flow, and resistances are used to realize the voltage-sharing in the topology. Firstly, the experimental waveforms of bidirectional LLC resonant converters are described, then the gain characteristic of the circuit is analyzed by using the fundamental wave analysis method. The same gain characteristic of ISOS topology when the bidirectional energy flow and the realization conditions of soft-switching are the basis of the design of bidirectional LLC converters. The transformers of high frequency and the circuit of voltage-sharing of ISOS topology are analyzed and designed. Finally, two converters of 6.25 kW are developed to verify the analysis method proposed. The DC/DC converters can realize ZVS and ZCS when energy is bi-directionally transmitting, and experimental research confirms the DC/DC converters have the same gain characteristic when energy is bi-directionally transmitting, and the voltage unbalance rate of two converters is less than 3%.