Model-based tuning approach for multi-band power system stabilisers PSS4B using an improved modal performance index

Multi-band power system stabilisers (MB-PSSs) PSS4B (IEEE standard 421.5-2005) are advanced power system damping controllers that have evident advantages over conventional PSSs in damping low-frequency oscillatory modes. However, finding optimal settings for such controllers is challenging due to the increased complexity of the PSS4B structure. This study describes a methodology for MB-PSS parameter optimisation based on an improved modal performance index as a measure of the controller's stabilising effect. The tuning problem is formulated as a non-linear constrained optimisation search method: proposed modal performance index is chosen as an objective function to be minimised, while properly selected constraints ensure stability of the closed-loop system and robustness of the proposed design. The methodology is demonstrated on a benchmark system that is based on an existing network. Comparative analysis between the MB-PSSs with optimised settings and speed-based PSS1A-type stabilisers designed using the conventional methods show the practicality and effectiveness of the proposed methodology. The implemented approach has an advantage of being scalable and suitable for the model-based tuning of feedback controller of general structure. Additionally, several performance metrics and non-linear simulations in the ElectroMagnetic Transient Program (EMTP) software confirm superior characteristics of PSS4B.