Effects and Mitigation of Nonzero DCM in Buck-Boost-Derived Hybrid Converter

Hybrid converter having ac and dc outputs, being single stage converter, is an interesting solution for dc nanogrid application. It offers independent control to both ac and dc output. The Buck-Boost-derived hybrid converter (BBDHC) proposed in this paper is capable of providing a wide range of buck/boost output voltage. For better understanding, a theoretical analysis of the converter in continuous current mode (CCM) and discontinuous current mode (DCM) is discussed. Unlike the conventional zero valued DCM, nonzero DCM (NZ-DCM) is a peculiar phenomenon observed in this converter. The NZ-DCM injects ripple in dc link voltage, deteriorating the performance and operation of BBDHC. To mitigate this, modified BBDHC (MBBDHC) is proposed. In MBBDHC, the NZ-DCM is replaced by forced CCM (FCCM). This modification permits the stable operation of MBBDHC under hybrid and standalone loads. Moreover, closed-loop study of MBBDHC is presented under load and voltage variations.