Harmonic Analysis for the Distribution System with Dispersed Generation Systems

This paper is to investigate the impact of dispersed generation systems (DGS) on the harmonic distortion for the distribution systems. An 11.4 kV radial distribution feeder containing 10 load buses in Taiwan has been selected for computer simulation of harmonic power flow analysis. The daily load pattern of the distribution feeder is used to simulate the bus voltage by executing load flow analysis. The harmonic current generated by nonlinear loads on each bus has been measured and applied to calculate the total harmonic distortion (THD). To alleviate the overload and provide the reactive power compensation for the feeder, the photovoltaic generation stations (PVGS) have been considered to connect to the feeder through a three-phase DC/AC converter drive. To investigate the impact of PVGS on the harmonic distortion for the feeder, the power generation and harmonic current produced by the PVGS have been recorded. With various capacities of PVGS connecting to the feeder, the harmonic distortion has been derived by performing the harmonic power flow analysis. Because the harmonic current introduced by PVGS is much smaller as compared to that generated by the existing distribution loads, the PVGS can be used to regulate the bus voltage very well without causing serious harmonic distortion if the proper filters are considered for the reactive power compensation.