Electrochemical impedance spectroscopy (EIS) measurement is an important method to diagnose the health status of the fuel cell stacks (FCS). So, how to take the EIS measurement more easily and efficiently is a meaningful research point. At present, the main EIS technique of fuel cells is to inject AC signals into the fuel cell stacks by DC/DC converter, but most of the existing schemes are complicated in the topology structure or controller design. Therefore, in order to reduce the complexity of the hardware and controller, this paper proposes an open-loop current injection method based on the interleaved DC-DC converter floating on the high-voltage side. With open-loop AC injection based on the idea of small-signal perturbations, only one voltage controller is needed to be designed, which is very simple in topology and control scheme. In addition, to satisfy the measurement accuracy, the amplitude of the injected AC duty cycle can be adjusted adaptively according to the frequency of the injected signals, thus keeping the amplitude of the input current of the DC-DC converter approximately 10 amperes. In the proposed control method, only one PI controller is used to stable the floating dc side voltage so that produces a DC bias duty cycle, and the amplitude of the injected AC duty cycle signal was adjusted adaptively by the theoretical calculation based on the AC equivalent circuit. Then, A simulation model is built in MATLAB/Simulink to verify the feasibility and performance of the proposed scheme. From the simulation results, not only the whole control and structure is simple and effective, and also the AC injection current has low harmonics at high frequency, which proves the feasibility and effectiveness of the proposed scheme.

Fuel cell stacks, electrochemical impedance spectroscopy, interleaved DC-DC converter, open-loop current injection, adaptive duty cycle