Loss Comparison of Various Unidirectional Rectifiers for Medium Voltage Applications

Unidirectional rectifiers are being preferred for applications where power flows only from ac side to dc side such as the machine side converter in a permanent magnet synchronous generator (PMSG) based wind energy conversion systems (WECS), as active front end rectifiers for medium voltage (MV) fans, pumps, blowers, compressors, and power supplies for telecommunications, X-ray, naval equipments etc. Absence of the regenerative or reactive power requirements make these converter topologies simpler with reduced number of active switches which increase power density and reliability, and reduce cost. This paper compares various converter topologies that can be used as unidirectional rectifiers for MV applications (3.5 MVA, 4 kV). The topologies compared in this paper are based on the PLECS simulation results which takes various characteristic plots of the semiconductor devices as given in manufacturer’s datasheets. The comparison results show the superiority of the five-level dual flying capacitor based active neutral point clamped (DFC-ANPC) topology in terms of power density, efficiency and even distribution of losses across the devices.