Embedded Estimation of Variable Speed Drive Input Current Distortion

This chapter delves into the estimation of variable speed drive input current distortion, focusing on Total Harmonic Distortion (THD) and Total Harmonic Current (THC) as critical indicators of electromagnetic compatibility (EMC) and drive efficiency. It begins by defining THD and THC according to relevant standards and then explores three different DC bus topologies: DC choke, C-less, and Electronic Smooth Inductance (ESI). The chapter presents a detailed analysis of the dynamic model of the DC bus, stability conditions, and harmonic calculations in the frequency domain. It highlights the differences in THD across various operating points and topologies. A key contribution is the proposal of a simplified THDI estimator that works in both continuous and discontinuous modes, offering high accuracy in normal operating conditions. The chapter concludes with a comparison of THDI for the different topologies, showcasing the practical applicability of the proposed estimator.