Non-linear Dead-time Error Compensation Method of Dual Active Bridge DC-DC Converter for Variable DC-bus Voltage

Abstract

This paper proposes a transmission power error compensation method for a Dual Active Bridge (DAB) converter with a three-level operation when a DC-bus is varied. The nonlinear transmission power error due to a dead-time is compensated by designing a zero current period to be longer than the dead-time using the three-level operation because the nonlinear transmission power error occurs when an inductor current reaches zero during the dead-time. The proposed method adjusts a zero-voltage period according to the variable DC-bus voltage in order to design the zero current period for compensating the non-linear transmission power error. In addition, the three-level operation is controlled to reduce a circulating current in order to reduce RMS value of the inductor current. The validity of the proposed method is confirmed by a 1.9-kW prototype. As the experimental results, the transmission power error is reduced from 49% to 3.5%.