Discrete impedance method for the oscillation analysis of pumped-storage power plants

Abstract

As the proportion of new energy increases in modern power systems, pumped-storage power plant attaches significance to balancing power supply and demand. Its operational stability has attracted extensive attention. Since the hydraulic characteristics of the pumped-storage power plant with a complicated conduit system are rather complex, it is difficult for the traditional continuous impedance method to obtain analytical solutions to the frequency responses directly. Therefore, an equivalent circuit modeling-based discrete impedance method is proposed to address this problem. The discrete impedance method possesses accurate modeling precision and is applied to the oscillation analysis of a pumped-storage power plant with a complex hydraulic network. Furthermore, the influences of the pump-turbine impedance and the pipe friction loss on the oscillation characteristics have been discussed. Numerical results indicate that the variations of the pump-turbine impedance and pipe friction loss impact the decay coefficients of different oscillation orders, thus influencing the system’s stability. However, they can hardly affect the eigen frequencies of the system. The proposed discrete impedance provides an alternative to the complex frequency analysis of complicated hydraulic systems.

Keywords

• Pumped-storage power plant
• Hydraulic impedance
• Equivalent circuit modeling
• Oscillation analysis