Hybrid damping of grid-tie inverter output harmonics for resonance rejection & wind park stability under high penetration

Grid-tie inverters are usually connected to Pad-Mount Transformers (PMT) through passive filters. Most grid-tie inverter manufacturers design these passive filters to eliminate high frequency current ripples and switching harmonics generated by the switching actions of inverters. Under high wind power penetration output power filters are susceptible to create severe resonance due to their interaction with the grid voltage harmonics and transmission line impedances. This resonance generates high harmonics which are not only not in compliance with the IEEE 519 power quality requirement, but also are very harmful to power system components. This paper proposes a hybrid damping approach which combines the passive damping of the filter with a physical resistor and an active damping of the inverter output harmonics with grid voltage harmonics feed-forward. The approach takes into account the passive filters interaction with the grid through impedance analysis under high wind power penetration. Simulations and field tests are shown to demonstrate the validity of the proposed approach.