Abstract
A phase-shifted dual-bridge series resonant DC-DC converter (DBSRC) is a competitive candidate for applications of an energy storage system. At the request of a step-load-change command such as the start-up and power-level change, the converter may suffer from large-amplitude transient oscillations due to improper transient modulation. Furthermore, the DC bias current and overshoot current/voltage in the resonant tank and transformer caused by oscillations may result in transformer saturation and poor dynamic performance. To solve these problems, two fast transient modulation (FTM) methods are proposed in this paper. First, based on the steady-state analysis of the converter with phase-shift control, the current and voltage trajectory of the resonant capacitor can be obtained. Then, the detailed principles of two FTM methods are explained for achieving a smooth transition. Through the adjustment of the durations of the adjacent switching intervals temporarily, the transient trajectory can be predicted and is expected to match the destination trajectory within one switching period. Consequently, the proposed FTM methods enable the converter to move from one steady state to another instantly and the step-load-change transition can be an overshoot-free procedure. Finally, both simulation and experimental tests prove that the two modulation methods can effectively eliminate DC bias current and overshoot current/voltage in the DBSRC transient process and obtain a fast transient response.
Highlights
This paper proposes two fast transient modulation (FTM) methods to achieve a fast and overshoot-free step-load change process
The DC bias current caused by the oscillations may increase the current stress of transformers and affect the reliability of converters
This paper proposes two methods based on fast transient modulation (FTM) to address these concerns
Summary
With the fast development of distributed power generation and energy storage facilities, efficient power conversion technologies have become hotspots in the research field of power electronics [1,2]. A small-signal model of DBSRC is further introduced in [17] and model-predictive control has been investigated in [18] All these feedback control strategies ignore the transient state in the analysis as the converter adapts to different transfer power demands. A universal solution for all the transient states with seamless transient processes is investigated in [27] These phase-shift strategies are optimized for non-resonant transient-state converters and need to select the switching pattern for multiple working modes, which complicates the implementation of the control strategy. The two methods will adjust the durations of switching intervals to match the predicted ones It can effectively solve large overshoot current and long transient response time in the transient process and obtain a fast transient response.
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