Design and Modulation of High Current Low Voltage Two-Level Multiphase Inverter

Due to the rapidly increasing use of electric motors in transportation and therefore safety-critical applications, inherently fault-tolerant multiphase machines are a topic of research with increasing interest. Besides the possibility of post-fault operation, multiphase machines are also capable of having lower torque ripple and higher power density than their three-phase counterparts. In order to make full use of the increased number of Degrees of freedom (DoFs) in machines with a phase number greater than three, the modulation of the inverter has to be fully understood. This research tries to aid in reaching this goal. Thereby a focus is laid on but not limited to multiphase inverters with a low dc link voltage and MOSFETs as semiconductor switches. Analytic calculations concerning the output voltage harmonics of m-phase inverters concerning different space vector modulation schemes are derived. Modulation schemes are compared to each other and areas of beneficial application of discontinuous modulation schemes identified. Active and passive component stress in the inverter is considered in detail for the general m-phase case. Moreover a five-phase 48V inverter prototype is presented along with detailed design considerations.