A Input-Series- and Output-Parallel-Connected Inverter System for High-Input-Voltage Applications

This paper presents the configuration and control strategy for input-series- and output-parallel- (ISOP) connected inverter system, which is constructed by connecting multiple inverters in series at input sides and parallel at output sides, such that the inverters share the input voltage and load current equally. The proposed configuration is suitable for high-input-voltage applications. In order to ensure the proper operation of ISOP inverter system, equal sharing of input voltage and sharing of output current among the constituent inverters must be ensured. The relationship between input voltage sharing (IVS) and output current sharing (OCS) is analyzed in this paper. In order to realize equilibrium among the constituent inverters, a three-loop control strategy, consisting of a common output voltage loop, IVS loops, and individual inner current loops, is proposed. The common output voltage loop regulates the inverter system at desired output voltage and provides the basic reference for inner current loops, which is adjusted by the IVS loops to achieve IVS. Both the output current and the output filter inductor current of the individual inverter can be chosen as the feedback signal for the inner current loop and the difference is compared. A 2-kVA two-module ISOP inverter system prototype is fabricated and tested in the laboratory and the experimental results verify the proposed control strategy.