Modular Current Sharing Control Scheme for Parallel-Connected Converters

A modular current sharing control scheme is proposed in this paper to attain good current distribution between equally rated parallel-connected converters. In this scheme, local information is used by each inverter to achieve the required current control with minimal information sharing between the converters. Unlike conventional current sharing control methods that use a stationary or rotating reference frame representation, the converter currents in the proposed controller are represented by the magnitude of the current space vector. As a result, each converter employs only one proportional-integral compensator to share the load current. The operation of the new current sharing control scheme is demonstrated using two different pulsewidth modulation (PWM) control strategies: conventional space-vector PWM and discontinuous PWM. A mathematical analysis of the proposed control scheme is presented, and the performance of the controller is experimentally verified using a 2.5-kVA test rig. The results show excellent current sharing characteristics with minimal communications between the parallel-connected converters.