Modeling and Fault Ride-Through Control of a Photovoltaic-Based Grid Supporting Microgrid Using a Secondary Control DSC Algorithm

This research work proposes a secondary control for a grid supporting microgrid with photovoltaic to ensure grid code compliance and ancillary services. The secondary control achieves the fault ride-through using a delayed signal cancellation (DSC) algorithm for negative sequence detection. The proposed control scheme satisfies grid code requirements by providing voltage control at the secondary level, which is active and more prominent in the transient duration of host grid faults without mode switching. This control also guarantees a continuous supply of the microgrid's sensitive local load while satisfying the grid code stipulations. Similarly, active power injection into the main grid is constrained by systematically shifting the MPPT operating point based on voltage sag depth to maximize reactive power injection to support the grid voltage sag. Using the DSC procedure, the detection algorithm is utilized to discover the instance of fault in a small fraction of a half-cycle under grid disturbance or fault to activate the proposed secondary control. Finally, the strategy developed also ensured that the DC-link voltage and AC grid current raises are suppressed while meeting microgrid load requirements. The detailed time-domain simulation studies of the model with the proposed secondary control schemes are executed using MATLAB Simscape ElectricalTM and Control SystemTM.