Frequency response Analysis of Doubly-Fed Variable Speed Pumped Storage Unit Based on Simplified Mode

Doubly-fed variable speed pumped storage units (DFVSPSUs) have good regulatory performance and have infinite potential to solve the problem of frequency stability caused by changes in renewable energy sources. However, the system is a nonlinear system with strong coupling of hydraulic electric control, and the model is relatively complex, so it is difficult to get the analytical solution by direct analysis. Therefore, the frequency response characteristics of DFVSPSUs are studied by establishing a simplified model. Firstly, the topological structure and operation characteristics of the variable speed pumped storage unit (VSPSU) using power control method are analyzed, and the simplified frequency modulation model of the VSPSU is established. Then, the frequency modulation model of power grid including constant speed pumped storage unit and DFVSPSU is established respectively, and the model is simplified by order reduction. Finally, a comparative analysis of the two power systems is carried out to further explain the contribution of VSPSUs to the stability of the power grid. The results show that after the DFVSPSU participates in frequency modulation, the damping characteristics of the system are improved, and the damping ratio is increased by 6.26%.