A 3C strategy for multi-module inverters in parallel operation to achieve an equal current distribution

A circular chain control (CCC or 3C) strategy for multi-module inverters in parallel operation to achieve an equal current distribution is presented in the paper. In the proposed inverter system, all the modules have the same control configuration and each module includes inner current loop and outer voltage loop controls. The PI controller is adopted as the inner current loop controller to expedite the dynamic response, the H^∞ robust control is adopted to reduce the interactive effect among the inverters connected in parallel. With the 3C strategy, the modules are in circular chain connection and each module has an extra control to track the inductor current of its previous module to achieve an equal current distribution simulation results of a two-module and a three-module inverter systems with different kinds of loads and with module discrepancy have demonstrated the feasibility of the proposed control scheme in equal current distribution and fast regulation. Hardware measurements are also presented to verify the theoretical discussion