A Fully Modular Control Strategy for Input-Series Output-Parallel (ISOP) Inverter System Based on Positive Output-Voltage-Amplitude Gradient

In this paper, a fully modular control strategy for input-series output-parallel (ISOP) inverter system is proposed to ensure equal sharing of input voltage and output current among the constituent inverters. Compared with existing control strategies, such as centralized control that restricts the modularity of the system and distributed control, which realizes voltage and current sharing by means of connecting constituent inverter modules through sharing buses, the proposed control strategy can achieve fully modular design without any control signal interconnection among the constituent inverters, leading to superior modularity and reliability. First, the control strategy is deduced and the principle of the control strategy is analyzed. Then, the detailed implementation and stability analysis of the proposed strategy are presented. At last, a two-module ISOP inverter system is tested in the laboratory and the experimental results verify the effectiveness of the proposed control strategy.