Active-Damping for Digital Controlled LC-Type Voltage Source Inverter with Positive Proportional Feedback of Filter Capacitor Voltage

For the LC-type voltage source inverter (VSI), the negative derivative feedback of the filter capacitor voltage is often lieu of the negative proportional feedback of the filter capacitor current for damping the inherent resonance between the filter inductor and the filter capacitor without using additional current sensors. The doing so, however, weakens the noise immunity because of the derivative feedback. By taking advantage of the digital control delay, this paper proposes the positive proportional feedback of the filter capacitor voltage for implementing the digital active-damping. Compared to the one realized by the negative derivative feedback of the filter capacitor voltage, the proposed solution not only enhances the noise immunity performance but also extends the boundary frequency of the positive resistance region formed by the digital active-damping from 1/6 to 1/3 of the sampling frequency. The stability criterion has been derived. Also, the feasibility of the proposed work has been verified on a 3-kVA single-phase LC-type VSI.