Frequency Scanning based Design of Supplementary Damping Controllers for Inverter-Based Resources

Adverse controller interactions involving IBRs are a major concern for power system engineers. IBR controllers are not standardized and are proprietary, making it difficult to study and mitigate these interactions. In this scenario, having a supplementary damping controller that modulates an available set point of the existing controller could be a pragmatic solution. There is a vast and positive experience in designing stabilizers for conventional synchronous generators using standardized control structures like washout and lead-lag blocks. The aim is to have similar, straightforward, and easily implementable damping controllers for the emerging IBR based networks. This paper presents an investigation into this issue using a three-IBR system example. For certain controller parameters, the system exhibits poorly damped low frequency oscillations between the IBRs. A simple supplementary damping controller structure using a local feedback signal is found to be feasible for mitigating the IBR oscillations. The frequency scanning approach which is well-suited for black-box system identification is found to be an effective tool for supplementary damping controller design.