An Improved Frequency Response Model for Asynchronously Interconnected Power Systems Considering Voltage Changes Due to Load Variations

Due to the reduction in the capacity of synchronous generator units and the gradual transition of synchronous grids to asynchronously interconnected systems, frequency stability has become increasingly critical for the safe and stable operation of power systems. However, existing equivalent model methods used for frequency analysis do not consider the impact of voltage changes during frequency events, leading to inaccurate calculations of frequency deviation. Therefore, this paper proposes an improved frequency response model (IFR) suitable for asynchronously interconnected grids that takes voltage changes into account. The IFR adds load flow calculations to the initial frequency response model, accurately calculating the actual power disturbance in the system and thereby more accurately predicting the maximum frequency deviation and quasi-steady-state frequency. The correctness of the model is verified in PSCAD/EMTDC on a four machine two area system (4G2A). The simulation results show that the improved frequency response model can better represent the frequency dynamics of the interconnected grid, with the relative error of the maximum frequency deviation reduced by up to 35.24%.