Abstract
This research presents a secondary control for a grid-supporting microgrid with photovoltaics sources to guarantee grid code compliance and ancillary services. The secondary control accomplishes the fault ride-through, which implements a delayed signal cancellation (DSC) algorithm for negative sequence detection. Without mode switching, the proposed control strategy meets grid code requirements and ensures voltage regulation at the secondary level, which is active and more salient throughout the transient period of host grid disturbances. This control also ensures a constant supply of the microgrid’s sensitive local load while adhering to grid code requirements. Similarly, active power injection into the main grid is limited by progressively altering the MPPT operating point dependent on the depth of voltage sag to optimize reactive power injection to sustain grid voltage sag. The recommended secondary control is triggered by utilizing the DSC process’s detection algorithm to identify the occurrence of a fault in a tiny fraction of a half-cycle in a grid fault. Consequently, while satisfying microgrid load needs, the devised technique guaranteed that increases in DC-link voltage and AC grid current were controlled. MATLAB Simscape ElectricalTM and OPAL-RT Lab are used to do time-domain simulations of the model using the recommended secondary control systems.
Highlights
According to current grid code standards, in response to a disturbance in the main grid causing voltage sags, grid-connected inverter-based microgrids must stop powering the microgrid loads
This study aims to provide a secondary control strategy that uses a fast delayed signal cancellation (DSC) for reactive power injection and faults current limiting to improve grid inverter-based microgrids with solar PV sources
The injected reactive power complies with the required reactive currents based on the percentage voltage drop specified in the emerging grid codes under different voltage sags caused by faults
Summary
According to current grid code standards, in response to a disturbance in the main grid causing voltage sags, grid-connected inverter-based microgrids must stop powering the microgrid loads. Low-voltage microgrids must be disconnected from the host grid before 120 cycles of voltage sag between 0.5 and 0.9 per unit, according to the IEEE Std 929-2000 standard [1,2]. Ancillary services, such as fault ride-through (FRT), were not considered part of the scope of microgrids and were not required [3]. Existing investigations [7,8,9] have shown that DER may play a substantial role in overall system stability and that photovoltaic systems can provide ancillary services to ease grid and power electronics difficulties [10]
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