Robust Control for Islanded and Seamless Mode Switching of Wind-PV-Grid Tied Generation System

This paper deals with robust control strategy for a distributed generation system (DGS), which operates in both islanded and grid-connected modes. Generally, in the lowvoltage islanded mode of DGS, the PCC (Point of Common Coupling) voltages are unbalanced due to the unbalanced load connection. Therefore, in an islanded mode of DGS, the LSC is controlled using the IPR (Improved Proportional Resonant) controller to maintain the PCC voltages quality within the IEEE-1547 standard. Moreover, the DGS is capable to synchronize to the grid without any transient current. During the change of modes of DGS, large transients occur in the battery current due to the switching of battery control. 

This problem is resolved by the presented bidirectional DC-DC converter control strategy and robust ILQSOGI (Inner Loop Quadrature Second Order Generalized Integrator) based PLL. The effectiveness of this DGS control strategy is verified by the corresponding MATLAB/Simulink platform under load unbalance, solar irradiance changes and during mode of switching. Moreover, the simulation results are validated using the test results and show the robustness of the control strategy during abnormal grid voltage condition.

Keywords— Solar Photovoltaic Array, Power Quality, Bidirectional DC-DC Converter, Load Side Converter (LSC) and Machine Side Converter (MSC).