Robust damping and decoupling controller for interconnected power network based on distributed energy resources

Converter based distributed energy resource (DER) units are intended to be integrated into the power system using grid-forming converters (GFCs). It proposes to emulate the synchronous machines dynamics and forms the grid voltage/frequency by instantaneously balance the load changes without peer-to-peer coordination. However, the damping and coupling characteristics of GFCs in multi-vendor interoperability-based network have not yet been fully explored. The paper proposes a step-by-step analytic method based on participation factor analysis to efficiently analyze the oscillatory modes and the coupling characteristics in the GFCs-based network, especially where the GFCs are controlled by different control techniques. Moreover, to efficiently damp these oscillatory modes and such control coupling, a hybrid damping method based on an oscillation damper and a decoupling controller is proposed. A mathematical modelling is derived to confirm the role of the proposed decoupling controller especially during transient periods. Design guidelines using pattern search algorithm are presented to identify the optimum parameters of the proposed hybrid damping method. Finally, the experimental results using Controller-hardware-in-the-loop (CHiL) verify the theoretical analysis and the efficient damping against large disturbances.