Optimal penetration levels for inverter-based distributed generation considering harmonic limits

The installation of inverter-based distributed generation (DG) has been increasing rapidly in recent years, and specifically, photovoltaic power systems. Such increased penetration will result in increased harmonics which could exceed the IEEE 519 allowable harmonic distortion levels. In this paper, the maximum DG penetration level is determined taking into consideration the IEEE 519 allowable voltage harmonic limits. The proposed study is formulated as a mixed integer non-linear programming (MINLP) problem where harmonics are determined using the decoupled harmonic power flow approach. The maximum DG penetration level based on optimal DG size and location is determined using particle swarm optimization (PSO) algorithm. The proposed formulation is tested on 18-bus and 33-bus radial distribution systems considering ten load and DG scenarios. The results show that by decentralizing the DG capacity, higher penetration levels could be achieved. The limiting effect of preinstalled DG at a certain bus on the overall DG penetration is also analyzed.