1 Electric Power Systems, Department of Energy Technology, The Faculty of Engineering and Science, Aalborg University2 The Faculty of Engineering and Science (ENG), Aalborg University3 Department of Energy Technology, The Faculty of Engineering and Science, Aalborg University4 Power Electronic Systems, Department of Energy Technology, The Faculty of Engineering and Science, Aalborg University5 unknown
This letter proposes an active damper with a series LC filter for suppressing resonances in an ac power-electronics-based power system. The added series filter capacitor helps to withstand most of the system voltage, hence, allowing a lower rated converter to be used for implementing the active damper. Unlike an active power filter for mitigating low-frequency harmonics, the proposed damper dampens resonances at higher frequencies, whose values are dependent on interactions among multiple grid-connected converters and reactive elements of the system. Its control requirements are, therefore, different, particularly in the low-frequency range, where the series LC filter is predominantly capacitive, rather than the usual inductive characteristics that exist between voltage-source converters and the grid (or load). This low-frequency challenge can fortunately be resolved by the proposed fourth-order resonant controller, in addition to the second-order resonant controller used for resonance damping. Experimental results obtained have confirmed the effectiveness of these controllers, and hence, the feasibility of the active damper.
I E E E Transactions on Power Electronics, 2015, Vol 30, Issue 8, p. 4037-4041