Research on Control Strategy for a Multiple Grid-Connected-Inverter System

In this paper, the static stability of droop control for a multiple grid-connected-inverter system is analyzed. The equations of droop coefficient to power capacity are derived. However, inverters based on conventional droop control have no inertia support for the power system. Therefore, a modified strategy adding virtual synchronous generator control to the conventional static droop approach is proposed. The inertia and damping for inverters are increased to suppress the variation of voltage frequency, which provides a perfect static stability and transient performance. After that, small-signal models are built to compare the frequency transient of these two control strategies. Finally, simulation experiments verify the effectiveness and validity of the modified strategy.