Active damping of LC resonance for paralleled indirect matrix converter based on cascaded control

The indirect matrix converters (IMC) offer the advantages of high reliability and compactness in structure due to no large energy storage components in virtual DC side, and thus have a promising application in the future. However, the LC resonance caused by input filter is one reason keeps it from being utilized in industry. Different from pervious solutions of LC resonance damping for single IMC, this paper proposes an active damping strategy for the paralleled IMC with both interleaved operation and cascaded control of input LC filter. The key is to apply the closed-loop control of grid currents to generate the references for capacitor voltages, which are tracked by the inner capacitor voltage loop. By designing the control parameters properly, this method can not only suppress the LC resonance effectively but also offer accurate control of grid currents. In order to further mitigate resonance, the interleaved operation is applied to reduce specific order harmonic around resonant frequency of LC filter. No additional cost will be required for the proposed interleaved and cascaded control strategy. Furthermore, the feed-forward terms of voltage drop on filter inductor and capacitor currents are added to the control, in such a way that the decoupling effects between the d-axis and q-axis are removed and the dynamic response becomes better. Both simulation and experiments are given to verify the correctness and feasibility of the proposed strategy.