Emulation of Multi-Inverter Integrated Weak Grid via Interaction-Preserved Aggregation

Simplified weak grid models are widely used to emulate the nonideal power grid for the design and stability analysis of grid-connected inverters. However, the dynamic behavior of a real grid with multiple inverters is complex. In this article, an emulation method is proposed for multi-inverter integrated weak grids using an interaction-preserved aggregation model associated with grid impedance. First, the interaction among inverters in weak grids is analyzed using the state-space model and participation analysis. Then, a two-inverter aggregation is proposed for a large-scale system. This model can preserve the impact of parameters on the interaction modes (IMs) and predict the IM-related instability of multi-inverter systems. Thus, the two-inverter representation is applied to emulation to preserve interactions and to simplify the testing of multiple inverters. The emulation of the 16-inverter system is implemented on a hardware-in-the-loop (HIL) test bench with one practical inverter controller under test and the remaining parts integrated in the OPAL-RT real-time simulator. The test results show that the instability attributed to the interaction can be identified by the proposed emulation method.