A Space Vector Modulator for the High-Switching Frequency Control of Three-Level SiC Inverters

Operating three-level inverters at very high switching frequency improves the dynamics of servo drives. It reduces the cost and size of harmonic filters that lessen the dv/dt stress of drive motor windings and bearings. Low harmonic current distortion is a further benefit. Other applications are line-side front end converters, uninterruptable power supplies (UPS), and photovoltaic installations. The requirements of very high-switching frequency control are beyond the computing power of modern microcontrollers and digital signal processors. The problem is overcome by a three-level space vector modulation scheme that defines the switching sequence by taking a sequence of logic decisions instead of doing time-consuming arithmetic operations. The control of the inverter neutral point potential is an inherent part of the scheme and does not need additional algorithms. Implementation in an FPGA permits operating at switching frequencies up to 100 kHz. Experimental results are presented.