Study On Modular Technology Of Bidirectional DC/DC Converter

Compared to a single module, modular power supply connected in ISOS (input series output series) has many advantages, it can improve reliability and voltage level and it’s suitable for two stages V2G (Vehicle-to-grid) system. During transferring power in both ways, the modular power supply needs a lot of input voltage control loop, that will decrease the reliability. To solve the above problems, this paper proposes ISOS module that makes up of DAB (bidirectional dual active bridge), and use the common duty control to increase the reliability of the power supply.On the basis of analyzing the working states of DAB, the relationship between the flowing energy’s direction and the moving angle is studied. The small signal model and the average circuit model of DAB is established. On the basis of establishing models, analyze the loss of the device and the soft switching region. The module ignores the resonance of the parasitic capacitance and needs to be verified.The differences of three-loop strategy and two-loop strategy are compared. The relation between input voltage and output current of DAB is special. Based on this, the common-duty-ratio control is proposed. Use simulation to verify the control mode and analyze the impact of various parameters on the input voltage.In consideration of the reactive power flow, soft switching range and the energy transfer ability and other factors, design the open-loop element, the sampling circuit and driving circuit is also designed; TMS320F28335 is used for controlling 16 MOSFET, DSP software is designed.Build the two DAB modules that is connected in ISOS and verify the ability of two-way energy flowing; the stability of control strategy is verified; waveform of different situations is obtained to verify our theory.