A digital charge-mode control algorithm for power decoupling in a flyback microinverter

This paper proposes a novel implementation scheme for the controller of a single-phase, grid-connected, flyback PV microinverter topology, which employs low-value film capacitors for achieving power decoupling. The proposed charge-balance criterion is used to develop a real-time controller which eliminates parameter-dependence, thereby improving the robustness of the system. A predictive algorithm is used to estimate the flyback transformer current in order to avoid inaccuracies arising from directly sensing the current. A stability analysis of the scheme is also presented, which reveals additional design restrictions on the minimum voltage of the decoupling capacitor. Simulation and experimental results validate the effectiveness of the approach.