Local Secondary Control for Inverter-Based Islanded Microgrids With Accurate Active Power Sharing Under High-Load Conditions

Local secondary control has been successfully used to regulate the frequency of inverter-based islanded microgrids without using communications. In this scenario, noticeable steady-state deviations have been observed in active power sharing caused by the inherent clock drift of the digital processors that implement the local control of inverters. This paper presents a control scheme that performs frequency regulation and improves the active power sharing under high-load conditions, thus alleviating the impact of clock drifts in this situation. The study introduces a theoretical analysis that quantifies the steady-state deviations in active power sharing. It also includes a design procedure for the control parameters based on static and dynamic specifications. Experimental tests validate the expected features of the proposed control. The experimental setup is based on a laboratory microgrid equipped with three independent digital signal processors with different clock drifts.