Frequency-domain passivity-based current controller design

Current controller design for three-phase voltage source converters, by which a passive input admittance is ideally obtained, is considered. Two design alternatives, with and without voltage feedforward, respectively, are shown to give similar performance. It is demonstrated how additional parts can be added to the controller while preserving the passivity property. This is applied particularly to resonant parts. The design method is finally applied to converters with an LCL input filter, where it is shown in many cases to compare favourably with a scheme where an inner loop is added for improved damping of the LCL resonance.