Feedback Quantizer vs Sigma-Delta Modulator for Voltage Source Inverters

The authors have recently proposed a novel modulation strategy for Voltage Source Inverters (VSI) which utilizes feedback applied around the inverter treated as a quantizer - Feedback Quantizer Modulator (FBQM). On the surface, FBQM has some similarities with Sigma Delta Modulator (SDM). However, the authors believe that FBQM is a genuine and substantial generalization of the feedback based modulation, and are presenting in this paper a comparative analysis detailing similarities as well as fundamental differences. Distributed spectrum of the inverter noise and flexible noise shaping are the two major features of FBQM which make it an attractive option in certain applications. When using FBQM of VSI as a part of a closed loop current control, current sampling is not ripple-free due to a random nature of generated voltage waveforms. In this paper the authors also propose an effective strategy to reduce the effects of non-ripple-free current sampling. The comparative study and proposed strategies are supported by detailed simulations in physics-based Saber environment, as well as experimental results.