Optimized Pulse Patterns for the 5-Level ANPC Converter for High Speed High Power Applications

This paper presents the analysis of the active neutral-point-clamped 5-level converter (ANPC5L) with regards to the total harmonic distortion (THD) for high speed, high power applications. A 5 MW machine with fundamental frequency of 500 Hz is considered. The converter can be switched up to 2 kHz, thereby making the switching frequency to fundamental frequency ratio in the range of 3-4. Different optimized pulse patterns (OPP) are studied for this case. It is shown that no extra filter is necessary to limit the THD in the considered application, when applying the proposed pulse patterns. Topology specific issues, such as the floating capacitor voltage balancing and the switching frequency of the devices, are investigated in detail for the proposed pulse patterns. The results are compared with a traditional pulse width modulation (PWM) approach