A Seamless Control Methodology for a Grid Connected and Isolated PV-Diesel Microgrid

In this paper, a seamless control methodology has been proposed for a photo voltaic (PV)- diesel generator (DG) microgrid to operate both in the grid connected and islanded mode. It does not require any islanding detection mechanism, to change the control philosophy from the grid connected mode to the islanded mode. A second order sliding mode control has been used to control the voltage source converter of the PV source whose set points have been generated by PI controllers. The maximum power point tracking algorithm for the PV system has been augmented with an auxiliary signal obtained using the electrical power output of the DG to reduce the output power of the PV system for economical operation of the DG unit. The DG unit is regulated with the frequency of the microgrid while the inverter used in the PV system regulates the voltage at the point of common coupling. Similarly, if the DG is uncontrollable due to any reason, the PV system is further added with an auxiliary signal based on the frequency deviation to maintain frequency stability. Simulation of the system has been carried out in MATLAB/SIMULINK with different levels of insolation and load to verify the proposed control scheme.