Analysis of a New Third Harmonic Injection Active Rectifier Topology Based on an NPC Three-Level Converter Cell

Active three-phase rectifier systems usually cover a wide field of applications where high total power factor (99%+) and low mains current THDi (typ. <5%) are required. Passive three-phase rectifiers on contrary are characterized as highly efficient and robust whereas their power factor is limited to 0.9...0.95 due to rather high harmonic input current components (THDi up to 48%). This paper analyzes a novel circuit topology for passive three-phase rectification. The proposed concept aims to an extension/option for standard diode rectifiers with DC side smoothing inductor based on third harmonic injection. The paper describes the fundamental operating principle and determines the current and voltage stress of the circuit components. Furthermore, design guidelines for a 10kW prototype rectifier including an appropriate control concept are included and proved by simulation.