Abstract
Dead-time effect has become an apparent issue in high-switching-frequency high-power dual active bridge (DAB) DC-DC converter. This paper gives a detailed analysis of phase-shift errors effect caused by dead time, including output voltage offset, soft-switching failure, optimal scheme failure, etc. Phase-shift errors effect will invalidate traditional analyses of optimal control and mislead the design of DAB converter. To overcome these drawbacks, various operating modes and an accurate transmission power model incorporating dead time under triple-phase-shift (TPS) control are developed. On this basis, an optimal TPS incorporating dead time (TPSiDT) scheme is further proposed to minimize the current stress, while guaranteeing soft-switching operation by using Lagrange multiplier method (LMM) and Genetic Algorithm (GA). The novel transmission power model can provide accurate power flow computation to avoid phase-shift errors. Therefore, in practical applications, the minimum current stress and soft-switching operation can be guaranteed, and the efficiency of DAB converter can be improved. Finally, the experimental results verify the feasibility of the proposed TPSiDT scheme.
Highlights
With the development of hybrid microgrid, battery energy storage systems, and uninterrupted power supplies, bidirectional DC-DC converters have been widely used in bidirectional power conversion applications [1,2,3,4,5]
It can be seen that the soft-switching constraints of dual active bridge (DAB) converter could be guaranteed over the full power range; the converter can operate in soft-switching state in practical applications
Based on the accurate power model and operational-mode constraints, a current stress reduction scheme is proposed based on Lagrange multiplier method (LMM) and Genetic Algorithm (GA)
Summary
With the development of hybrid microgrid, battery energy storage systems, and uninterrupted power supplies, bidirectional DC-DC converters have been widely used in bidirectional power conversion applications [1,2,3,4,5]. In previous work, researchers have paid more attention to the external characteristics of dead-time effect, and the phase-shift errors effect is seldom studied comprehensively These problems will affect the accuracy of the traditional optimal schemes, and even invalidate the modulation schemes. The transmission power and switching characteristics are provided in [19] to describe the dead-time effect in three-phase DAB converter These accurate power models provide approaches for accurate power flow computation to avoid phase-shift errors. Due to the accurate power model proposed in this paper, the phase-shift errors can be avoided, and the converter can operate in minimum-current-stress and soft-switching state in practical applications.
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