Circulating current reduction-based hybrid controller of an electrical drive system fed by two parallel inverters

This paper presents a control technique of an electrical drive system fed by two parallel-connected voltage source inverters (VSIs). Two types of controllers are used to ensure a correct control of the system under different situations, especially, in case of structural or control imbalances between the two VSIs, which leads to parasitic zero-sequence circulating currents (ZSCC) appearance. So, a linear PI controller and a nonlinear sliding mode controller are combined together to act simultaneously based on the frequency separation principle and form hybrid controller. Therefore, the designed controller allows reduced ZSCC and offers stability and robustness against external disturbances. Simulation and experimental investigations shown that the proposed hybrid controller ensures the control of the drive system with ZSCC suppression even in the presence of imbalances.