Dynamic modeling and control of interleaved flyback module-integrated converter for PV power applications

For photovoltaic applications, the interleaved flyback module-integrated converters (MICs) (IFMICs) operating in continuous conduction mode (CCM) show the advantages of high power density, low voltage and current stresses, and low electromagnetic interference but demonstrate a difficult control problem compared to the discontinuous conduction mode. This paper concentrates on the control issues and presents detailed modeling, in-depth dynamic analysis, and a two-step controller design approach for IFMIC systems operating in CCM. The proposed modeling approach is based on the fourth-order system considering the dynamics of the output CL filter. This realistic fourth-order system modeling shows the presence of a resonant peak at a certain frequency, which can cause phase loss and constraints of system bandwidth. A decoupled two-step controller design approach is thus proposed to simplify the modeling and control synthesis in the IFMIC development. The decoupled controller consists of a proportional-integral controller (based on the simplified model), followed by a lag term for mitigating the effect of the resonant peak. A 200-W digitally controlled MIC prototype is constructed for evaluation purposes. The simulation and experimental results verify the effectiveness of the proposed modeling and control approaches.