Control strategy to achieve input voltage sharing and output current sharing for input-series-output-parallel inverter

The input-series output-parallel (ISOP) inverter, which consists of multiple inverter modules connected in series at input and parallel at output, is attractive solution for high input voltage and high output current applications. Input voltage sharing (IVS) and output current sharing (OCS) of the ISOP inverter are the basic design requirements. This paper reveals the relationship between IVS and OCS, and shows that if OCS is achieved, IVS is automatically achieved; and if IVS is achieved, only the active components of the output currents of the modules are identical, the root-mean-square (RMS) values or power factor angles of the module output currents should be equal in order to achieve OCS. However, the attempt to achieve OCS is not stable. A control strategy to achieve both IVS and equality of the power factor angles of all the module output currents is proposed in this paper, which ensures both IVS and OCS. A 2 kVA prototype of two-module ISOP inverter is fabricated and tested in the lab and the experimental results verified the proposed control strategy.