Frequency Dynamic Characteristic Analysis of Ultra-Low Frequency Oscillation and Multi-Machine GPSS Parameter Tuning Method

[Objective] The growing concern over frequency stability is attributed to the decreasing overall inertia of power systems. To improve the analysis of frequency stability and performance of modern power systems， a frequency dynamic characteristic analysis method for ultralow frequency oscillations is proposed， in addition to a multimachine governor power system stabilizer （GPSS） parameter tuning method aimed at enhancing the frequency regulation performance. [Methods] The proposed method developed a frequency characteristic analysis model that integrates power system stability and frequency regulation performance from the frequency-domain perspective. Initially， a model was derived based on the rotor circuit， thereby demonstrating the properties of constant distribution vector elements and the approximate congruence of the speed response function matrix. Subsequently， leveraging these properties， the model was simplified to form a low-dimensional dynamic framework for analyzing ultralow-frequency oscillations. Finally， a parameter-tuning method for multimachine GPSS was developed based on this model. [Results] The proposed frequency dynamic analysis model was applied to practical power systems， and the GPSS mechanism for suppressing ultralow-frequency oscillations was revealed via vector margin analysis. The validity of the distribution vector and speed response function properties， as well as the overall model were validated using an IEEE 4-machine 11-node case study. The effectiveness of the GPSS parameter tuning method was validated via time-domain simulations and vector margin assessments for both a 10-machine 39-node system and an equivalent model of the Yunnan power grid. [Conclusions] The proposed frequency dynamic characteristic analysis method and its simplified model provide a theoretical foundation for the widely employed unified frequency models in engineering. This approach provides a novel tool for frequency stability analysis of power systems and is of great significance for advancing the frequency regulation capabilities of modern grids. Furthermore， the GPSS parameter-tuning method facilitates effective suppression of ultra-low-frequency oscillations， thereby enhancing the stability and performance of power systems.