Commissioning and Testing of a Novel Buck-Boost Phase-Modular Three-Phase AC/DC Converter with Low Component Number

Abstract: In this thesis, a 1kW hardware prototype of a three-phase inverting buck-boost converter, termed as 6 Switch Buck-Boost Y-Inverter (6YI) is commissioned and tested. The 6YI is designed to be used as a motor drive for renewable energy applications such as fuel cell, solar etc powered motor drives with wide input voltage capability. Three modulation schemes i.e., conventional sinusoidal pulse width modulation, third harmonic injection pulse width modulation and discontinuous pulse width modulation are investigated and evaluated experimentally. The thesis presents an analysis of the efficiency improvement with harmonic injection techniques, which allow to improve the converter efficiency by up to 31% compared to conventional modulation. For the commissioning, a simplified controller is developed to reduce the computational burden on the digital signal processor. The measurement system is improved with the use of an opamp circuitry. The efficiency calculation for the converter system is made more detailed and the gate driver performance is assessed. Finally, the dynamic characteristics of the converter are evaluated and presented. The appendix further comprises an investigation of an 11kW prototype of twelve switch Y-rectifier, where system-startup is discussed, and the performance of a electromagnetic interference filter is assessed.