Synchronization and dq Current Control of Grid-Connected Voltage Source Inverter

The increased trend in using the renewable energy instead of fossil fuel based generation due to its low environmental impact and to facilitate the increased consumption has led to extensive use of distributed generation. The use of power electronics with renewable energy offers wide advantages including greater controllability of generated power and fulfilling the requirements for grid connected systems. The interface of renewable energy consists mainly of the Voltage Source inverter therefore its control is an important factor as its output should be completely synchronized with grid. In this paper the synchronization of grid connected voltage source inverter and control of injected current to ensure unity power factor at point of common coupling (PCC) is discussed. Phase locked loop is used to extract grid angle and to lock synchronous rotating dq reference frame with grid voltage in terms of frequency and phase thus making the control parameters as dc values. The current control strategy is Voltage oriented Control (VOC) implemented in synchronous rotating dq frame to control active and reactive power independently by controlling currents in d and q axis respectively. The simulation of system is done in Matlab Simulink environment using the Simpower toolbox.