T-Connected Autotransformer-Based 40-Pulse AC-DC Converter for Power Quality Improvement

Design of a T-connected autotransformer based 20-pulse ac-dc converter is presented in this invention. The 20-pulse topology is obtained via two paralleled ten-pulse ac-dc converters each of them consisting of a five-phase (five-leg) diode bridge rectifier. For independent operation of paralleled diode-bridge rectifiers, a zero sequence blocking transformer (ZSBT) is designed and implemented. Connection of a tapped inter-phase transformer (IPT) at the output of ZSBT results in doubling the number of output voltage pulses to 40. The proposed structure has been implemented and simulated using Matlab/Simulink software under different load conditions. Simulation results confirmed the significant improvement of the power quality indices (consistent with the IEEE-519 standard requirements) at the point of common coupling. Experimental results are obtained using the designed and constructed laboratory prototype of the proposed converter to validate the design procedure and the simulation results under varying loads. The VA rating of the magnetic in the proposed topology are calculated to confirm the savings in space, volume, weight, and cost of the proposed configuration.