An Active Damping Method for Interface Converters of Distributed Generation

With development of sophisticated renewable energy technologies, paradigm shift of both power generation and power distribution is happening and happening fast. Compared with conventional power generation, renewable energy sources are installed to the utility grid in a distributed fashion, which may result in various power quality issues, such as unbalance voltage and harmonic voltage resonance. An active damping method for interface converters of distributed generation is presented in this paper. The converter operates as admittance for fundamental positive-sequence frequency, and various conductance for fundamental negative-sequence frequency and harmonic frequencies. The admittance command is dependent on generator available power and grid voltage regulation; the conductance commands are determined according to required suppression of unbalance voltage and harmonic voltage at the converter installation location. Based on the control, the converter can deliver real power, absorb or release reactive power for grid voltage regulation, and provide active damping for both unbalance voltage and harmonic voltage. Therefore, positive-sequence voltage, unbalance voltage, and voltage distortion of the grid would be simultaneously maintained at an allowable level as the converter delivers real power. Operation principles are explained, and computer simulations are provided to validate the effectiveness of the proposed approach.