Fully Decoupled Active and Reactive Power Distribution Control for Single Phase Cascaded Connected Microinverter Under Island Mode

Cascaded Connected Microinverter (CCM) system takes the advantage of adapting low voltage stress submodules to build the high voltage output, which makes it easier and safer to achieve for many applications. The distribution of active and reactive power in the CCM system has always been interdependent, resulting in additional communication components in different submodules. Such communication components within different submodules can be avoided by inverse droop control, which is similar to droop control in a parallel inverter system. However, the inverse droop control method can only ensure the power distribution equally among different submodules, and there still exist multiple equilibrium points, which may cause the system to become unstable. This paper delves into the intricacies of power distribution and communication challenges within different submodules, examining both grid-tied and islanded Cascaded Connected Microinverter (CCM) systems. It introduces an enhanced control method designed to address active and reactive power distribution issues in single-phase cascaded Microinverter system without the need for additional communication components. The proposed control method relies on feedback from each submodule's reactive power amplitude and power phase angle to autonomously adjust its output voltage and frequency. The newly proposed approach achieves a wide range of active and reactive power distribution while maintaining full decoupling. This paper conducts a comprehensive analysis of the power distribution range, control stability, and dynamic response associated with the proposed method. Simulation results are presented, and the feasibility of the control strategy is further verified through the construction of a hardware prototype, substantiated by experimental findings.