Space Vector Based Hybrid Random Pulse Width Modulation Technique for a 3-Level Inverter

This paper proposes a Space Vector based Random Pulse Width Modulation technique (RPWM) for a 3-level inverter Randomization is achieved by random placement of active vectors in fixed switching time period. Flexibility in random placement is limited when the duration of active vectors is comparable with switching time period. In such case, this paper proposes a hybrid operation where, in addition to random placement of active vectors, switching frequency is also varied randomly for every PWM cycle. In hybrid operation, switching frequency is limited in the range 2.5 +/- 1 kHz by limiting the bounds of the randomization. The proposed scheme uses a mapping technique, by which, randomization is effected to the vectors of a 2-level inverter From random vectors of 2-level inverter, random switching vectors for the 3-level inverter are derived. The proposed scheme does not require any external circuitry and it can be implemented for any 3-level inverter topology. The algorithm is implemented in TMS320LF2407 DSP platform for a 2-hp induction motor driven by a 3-level inverter in open-end winding configuration and experimental results are presented.