Seamless boost converter control in critical boundary condition for fuel cell power conditioning system

The boost converter operates either in discontinuous conduction mode (DCM) or in continuous conduction mode (CCM). The operation mode is determined by the duty ratio, load and parameters of the boost converter. The plant model in DCM and CCM are different in the frequency domain response. Therefore, it will be difficult to design a controller with stable operation and fast transient response for both modes. Moreover, the boost converter will be unstable between DCM and CCM. In this paper, the proposed control strategy can transit between DCM and CCM seamlessly by adding a mode detector, the boost converter can be automatically operated by selecting of control loop in both operation modes. The proposed controller still has a voltage control loop in DCM and current/voltage control loops in CCM. Each controller is designed by considering the stability and response time. The proposed mode detector will be explained with a frequency domain analysis. Due to the wide range operation capability of the proposed control strategy, the proposed control strategy is suitable in the fuel cell portable applications. In addition, smooth operation of the converter will also be beneficial to the fuel cell stack reliability. A 20 W boost converter prototype is used to verify the performance of the proposed control scheme.