Power quality compensation in smart grids with a single phase UPQC-DG

Modern electrical energy networks as smart grids use green energy sources such as wind and solar power. One of the impacts of smart grids on distribution systems is power quality compensation. This paper describes a novel structure for single phase UPQC-DG (Unified Power Quality conditioner-Distributed Generation) for DC output DG systems which can be used in smart grids. The proposed configuration can be used not only for compensation of power quality problems but also for supplying of load power partly. In the proposed configuration, a DG system with low voltage output has been connected to the DC side of UPQC. This converter has been composed of one full-bridge inverter, one three winding high frequency transformer and two cycloconverters to achieve a desired output signals with low voltage DG systems. High frequency transformer steps up voltage of the primary side, reduces the converter volume and also provides an electrical isolation between input DG and main grid. Another capability of the proposed configuration is elimination of UPQC DC link capacitor and the bulky power frequency transformer. State space equations for modes of the proposed converter are presented for dynamic analysis and providing proper control based on phase shift with nonlinear control. The nonlinear controller is based on Input-Output feedback Linearization to achieving some prescribed behavior of the proposed UPQC-DG in mitigation of power quality problems. The performance of the proposed system was analyzed via simulation with PSCAD/EMTDC analysis program software. The results are presented to confirm the validity of the proposed approach.