Study and evaluation of DC-Link perturbations models for three-level DCI-NPC power amplifiers

This paper presents the most important sources of distortion in high power DCI-NPC amplifiers. These distortions sources are attributed to power supply perturbations due to the DC-link midpoint voltage oscillations. It is presented a classic model for assessing the magnitude of these disturbances and to justify the need to correct the classic model to accommodate the real load impedance variations. It is proposed a new model and this is compared and studied with the classic by analytical, experimental and simulation methods. This work concludes that, in control or cancellation applications, it is necessary to use models that include the load impedance variations regarding the frequency.