Bidirectional Isolated Ripple Cancel Dual Active Bridge DC-DC Converter

The bidirectional isolated dual active bridge DC-DC converter has been widely used for high power applications. The converter features a simple configuration, high efficiency, compact size, and flexible design. However, DC-link capacitors suffer from high current ripple that limits the lifetime of aluminum electrolytic capacitors. In addition, the power rating of DC-DC applications is growing more and more nowadays. One example, is ultra-fast charging stations for future electric vehicles. Accordingly, the design of DC-link capacitors faces high current ripple issue, that is to say, the challenge of converter reliability and volume selection. To solve this problem, a ripple cancel type dual active bridge converter is proposed in this paper. By adding few small size and capacitance film or ceramic capacitors, the current ripple of the DC-link capacitor could be significantly reduced. Input/output voltage ripple could be reduced as well. In addition, the voltage stress of the main switches could be clamped without additional snubber capacitors. Furthermore, the circuit design is similar to the conventional DAB converter. A 1kW prototype was implemented with a 400 V input/output voltage and a 100 kHz switching frequency to demonstrate its feasibility. The RMS current of the DC-link capacitor was reduced to 125mA in the experiment.