Abstract: Taking the input-parallel output-series（IPOS）type boost full bridge isolated converter（BFBIC）as the research object. Aiming at the problem that its internal fault cannot be located quickly after it occurs,a fault diagnosis strategy based on the waveform integration method is proposed. This strategy selects fixed measuring points inside the converter,analyzes the waveform characteristics of each electrical quantity when the converter has a hard fault or a DC collection line fault based on the operating mechanism,and identifies the fault location by summarizing the characteristic rules. Aiming at the problem that the existing redundant bridge arm scheme is not applicable to BFBIC-IPOS,a protection strategy using redundant boost units to achieve internal fault ride-through is proposed. This strategy avoids over-current and over-voltage problems in the switching process of the boost unit by changing the device parameters and the standby state of the redundant unit. Finally,through PSIM modeling and simulation,the effectiveness of the fault diagnosis strategy and the redundancy protection strategy is verified.