Decentralized Control for Fully Modular Input-Series Output-Parallel (ISOP) Inverter System Based on the Active Power Inverse-Droop Method

Abstract

Input-series-output-parallel (ISOP) inverter systems are suitable for the high-input-voltage and large-output-current applications. In this paper, an active power inverse-droop control method is presented for the ISOP inverter system, in which the polarity of active-power feedback is inversed to be positive compared with the traditional droop control while the reactive power droop is still adopted to achieve voltage and power sharing of the system. The modularity and reliability of the system are greatly improved due to that both power circuits and control circuits of the constituent modules are self-contained and independent. The input voltage sharing and output current sharing can be well achieved without the sampling of input voltage, so the high-voltage sensors are eliminated. Thus, the cost and volume of the system can be reduced. The operational principle of the active power inverse-droop control is introduced and the detailed system design is presented based on the proposed control scheme. The stability analysis and the guideline for power sharing loop design are also provided. Finally, simulation and experimental results of a two-module ISOP inverter system verify the effectiveness of the proposed control strategy.