Current Shaping in a Hybrid 12-Pulse Rectifier Using a Vienna Rectifier

This paper presents a hybrid rectifier consisting of a 12-pulse rectifier in parallel with a Vienna rectifier. In the proposed structure, the 12-pulse rectifier supplies the bulk power to the load, whereas the Vienna rectifier shapes the input current to reduce its harmonic distortion. The unidirectional power flow of the Vienna rectifier results in undesirable distortion around the current zero crossing, which deteriorates current shaping in this region. To overcome this problem, besides current shaping, the Vienna rectifier is forced to participate in the active power. In this regard, the share of output power in each rectifier module must be calculated. To shape the input current, the reference current for the Vienna rectifier is generated using instantaneous power theory, and current tracking is carried out using the finite control set model predictive control. A detailed analysis of how to select the output power sharing ratio based on system losses and input current distortion is presented. The theoretical analysis is verified by using simulation and experimental results obtained from a 1 kW laboratory setup.