A distribution system harmonic compensation approach using DG-grid interfacing converters at low switching frequency

In recent years, embedding ancillary functions of distributed generation (DG) have drawn great attention due to the increasing penetration of renewable energy based DG such as photovoltaic, wind turbines and fuel cells. Among these ancillary functions, harmonics compensation is becoming more interesting and important with the growth of nonlinear loads in today´s power distribution system. When controlled properly, the DG-grid interfacing converters can provide effective harmonic compensation for the distribution power system. However, the conventional harmonic control methods used for active power filters (APFs) may not be suitable for DG units, where the flow of real and reactive power limits the switching frequency to be lower than APFs, especially when the capacity of DG is large. At this low switching frequency, harmonic compensation performance or even the system stability may be affected. In this paper, a harmonic compensation approach suitable for DG-grid interfacing converters at low switching frequency is proposed.