Design and analysis of active power control strategies for distributed generation inverters under unbalanced grid faults

Distributed power generation systems are expected to deliver active power into the grid and support it without interruption during unbalanced grid faults. Aiming to provide grid-interfacing inverters the flexibility to adapt to the coming change of grid requirements, an optimised active power control strategy is proposed to operate under grid faults. Specifically, through an adjustable parameter it is possible to change the relative amplitudes of oscillating active and reactive power smoothly, while simultaneously eliminating the second-order active or reactive power ripple at the two extremes of the parameter range. The steering possibility of the proposed strategy enables distributed generation inverters to be optimally designed from the perspectives of both the power-electronic converters and the power system. The proposed strategy is proved through simulation and further validated by experimental results.