Wideband Harmonic Resonance Characteristics and Coordinated Damping Method for Distributed Generation Power Plants

Impedance interactions generally exist within the networks of distributed generation power plants, which have the potential for wideband harmonic resonances. For exploring these resonance phenomena, the impedance model of a typical distributed generation power plant is initially established in this paper. Furthermore, the distribution of the resonance bands is analyzed, and their classification is discussed. Additionally, a coordinated damping method, which comprises an active damper and a passive damper, is set forth to attenuate these resonance bands. The principle behind the coordinated damping is to dominate the plant's harmonic impedance by introducing the passive damper, and in the meantime to block the harmonic impedance interacting between the plant and the grid by virtue of the active damper. Finally, substantial simulations and experiments are performed. The results indicate that harmonic currents do deteriorate during their propagation along the feeders, the plants are subjected to the wideband resonances caused by both the plant- and feeder-level impedance interactions, and the proposed coordinated damper enables to relieve the intensity of the impedance interactions, thereby fulfilling the demand for the harmonic resonance control of the plants.