Grid integration of photovoltaic and wind based hybrid distributed generation system with low harmonic injection and power quality improvement using biogeography-based optimization

This paper investigates the combined operation and performance of the doubly fed induction generator (DFIG) and powerful custom power devices such as dynamic voltage restorer (DVR), static compensator (STATCOM) and unified power quality conditioner (UPQC) with common distributed generation (DG) systems. Improved multilevel inverter based topologies for DVR, STATCOM and UPQC operations using DFIG and PV are proposed in this paper. The proposed technique can efficiently mitigate the power quality problems, for example, voltage sag, swell, flicker, reactive power, voltage interruption, unbalance neutral current, voltage and current harmonics, etc. in the distribution system. The proposed DG connected three phase multilevel converter for photo voltaic (PV) system reduces filtering requirements, increases redundancy and enables transformerless interface with grid. Biogeography-based optimization (BBO) technique is applied in this paper to calculate exact switching angles for the inverter at each modulation index considering low total harmonic distrotion (THD) for the output voltage. The performance of the UPQC mode is compared with both DVR and STATCOM modes. For the proposed topology, the simulation studies with MATLAB are presented which show that the proposed DFIG and PV based UPQC performs significantly better than the DG-DVR and DG-STATCOM combinations.