Low Harmonic 12-Pulse Thyristor-Based Rectifier with an Auxiliary Circuit

To enhance the harmonic suppression capability of a 12-pulse thyristor-based rectifier, this paper introduces a novel harmonic suppression strategy. The strategy improves the input current waveform of the rectifier by adding a Harmonic Suppression Module (HSM) at DC-side. Coupled with a predictive current control strategy, this approach ensures that the input current harmonics comply with the specified requirements across various load conditions. Firstly, according to the current relationship on the AC/DC side of the 12-pulse rectifier, the input current of HSM and its four operation modes are analyzed. Subsequently, the control strategy is introduced, and the target current waveform on the DC side is formulated. Finally, an experimental prototype is built using a Hardware-In-the-Loop (HIL) test system. The proposed rectifier, equipped with the HSM, presents several advantages, such as simple circuit structure, low harmonic content and programmable output current or voltage. By prioritizing the requirement for a rapid dynamic response in load current, the harmonic content is effectively reduced, resulting in a nearly sinusoidal waveform with THD of less than 5%. Simulation and experimental results have corroborated the correctness of the theoretical analysis.