Abstract
In this paper, a non-isolated stacked bidirectional DC-DC converter with zero-voltage-switching (ZVS) is introduced for the high step-up/step-down conversion systems. The extremely narrow turn-on and/or turn-off duty cycle existing in the conventional bidirectional buck-boost converters can be extended due to the stacked module configuration for large voltage conversion ratio applications. Furthermore, the switch voltage stress is halved because of the series connection of half bridge modules. The PWM plus phase-shift control strategy is employed, where the duty cycle is adopted to regulate the voltages between the input and output sides and the phase-shift angle is applied to achieve the power flow regulation. This decoupled control scheme can not only realize seam-less bidirectional transition operation, but also achieve adaptive voltage balance for the power switches. In addition, ZVS soft-switching operation for all active switches is realized to minimize the switching losses. Finally, a prototype of 1 kW operating at 100 kHz is built and tested to demonstrate the effectiveness of the proposed converter and the control strategy.
Highlights
Energy storage systems (ESS) with bidirectional DC-DC converters are essential in renewable energy based microgrids, electric vehicles (EVs), transportations, et al [1,2,3,4,5]
Due to the stack structure and plus phase-shift control (PPS) control method, the voltage stress of power switches is reduced to half of the high-side voltage and the extreme duty cycle operation is avoided in high step-up/step-down conversion systems
Once the falling time tf of S1 is smaller than the dead time td, ZVS turn-on of S1 can be achieved by satisfying the following jILr ðt0Þjtf 1⁄4 uDtf
Summary
Energy storage systems (ESS) with bidirectional DC-DC converters are essential in renewable energy based microgrids, electric vehicles (EVs), transportations, et al [1,2,3,4,5]. The duty cycle and phase shift angle of the PPS control strategy can balance the voltage of the high and low voltage side sources, and regulate the power flow independently and smoothly, which eliminates the requirement of switching pattern change. Due to the stack structure and PPS control method, the voltage stress of power switches is reduced to half of the high-side voltage and the extreme duty cycle operation is avoided in high step-up/step-down conversion systems. The resonant current iLr remains unchanged due to the short interval and the capacitor Cs4 is charged while Cs3 is discharged in a linear way, and the ZVS turn-off of S4 is achieved. At t5, the switching voltage of S2 reduces to zero and iLr flows through the anti-parallel diode of S2, to guarantee the ZVS turn-on for S2 during this stage. Resonant capacitor Cr is parallel connected with CH2 through inductor Lr, and iLr changes with a small slope. iLf decreases with the same slope as that in stage and ix equals to iLr : ILr ðt7Þ
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