A Novel Analog Control Strategy With Simplified Implementation Scheme for Boundary Conduction Mode Flyback Microinverter

With the continuous reduction in the per-watt cost of photovoltaic modules, the complexity and cost of the controller circuit are becoming one of the key factors limiting the competitiveness of flyback microinverters in cost-sensitive PV applications. To address this issue, this article proposes a novel analog control strategy for boundary conduction mode flyback microinverters. This strategy utilizes a minimal number of basic analog components to achieve low total harmonic distortion in grid-connected current and high static and dynamic MPPT efficiencies. To enable peak-current control, a dedicated analog divider circuit, consisting of only three basic components, is designed to perform complex computations typically required for the traditional current reference. Using this divider, low harmonic distortion grid-connected current and a high power factor can be achieved. In addition, an improved analog MPPT strategy with optimized perturbation logic and control timing is introduced to simplify the hardware implementation and eliminate misjudgment issues caused by the double-line frequency power fluctuations. The improved strategy enables both high efficiency and stable MPPT control without the need for additional timers and signal conditioning circuits. Experimental results on a 125 W prototype are presented to validate the advantages of the proposed analog control strategy.