Voltage Injection based MPDPC Technique for Individual Phase Loss Reduction in Active Front-End Rectifier

Active front-end (AFE) rectifiers are a well-known solution for industrial applications because of several advantages such as bidirectional power flow, low harmonic distortion of the line currents, and the possibility of the dc-link voltage adjustment. Typically, in three-phase AFE rectifiers, the power is distributed evenly among the phase legs, aiming for a natural balancing of aging over time. However, uneven thermal stress caused by different switching frequencies or design of cooling system and prior replacement of failure power switches might create an unavoidable aging mismatch between phase legs of AFE rectifier. In this article, a per-phase model predictive direct power control with offset voltage injection is proposed. The proposed method notably reduces power loss of the leg having highest aging state to improve the lifespan of rectifier and reduce the maintenance costs. The active power and reactive power of the AFE rectifier are regulated using predicted rectifier voltages, which are modified by injecting proper offset voltage to decrease switching loss in the leg having highest aging state. The minimum power loss in the leg having highest aging state involves avoiding changing the corresponding switching state for two-thirds of the fundamental period. The simulation and experimental results are presented in comparison to conventional model predictive direct power control to confirm the effectiveness of the proposed technique.