Load-sharing between two paralleled UPS systems using Model Predictive Control

Abstract

Increasing the power rating and reliability of a power conversion system are the main reasons for the parallel operation of power electronics converters. However, when linked in parallel, the converters are subjected to a circulating current that compromises optimum system operation. Moreover, due to efficiency and flexibility reasons, a strategy for power-sharing is crucial. This paper proposes a Finite Control Set Model Predictive Control (FCS-MPC) scheme for two parallel connected Uninterruptible Power Supply (UPS) systems based on two 3-Level Neutral Point Clamped (3LNPC) converters. With the proposed control scheme, a precise load-sharing can be defined, with different power being supplied by each UPS system. Simultaneously, the Zero Sequence Circulating Current (ZSCC) can be effectively suppressed. Simulation results validate the proposed control scheme.