The invention provides a stability judgment method for a direct-current
bus of a full-power pumped storage unit, and relates to the technical field of hydroelectric power generation. The method comprises the steps that a direct-current
bus capacitor is equivalent to two parallel equivalent capacitors, and the pumped storage unit is split into a unit side and a network side with a parallel connection point as a boundary; respectively constructing small
signal models of the
electrical devices of the two parts; based on each
small signal model, respectively constructing a corresponding
admittance model, and then constructing a corresponding impedance model; substituting the electrical parameters and the
control parameters into the impedance model, and drawing a corresponding Bode diagram; and under the same working condition, if the
phase difference at the amplitude intersection point of the two Bode diagrams is less than 90 degrees, the
direct current bus does not generate interactive
instability under the corresponding working condition, otherwise, the interactive
instability occurs. According to the method, the modeling difficulty and
model complexity of the full-power pumped storage unit can be effectively reduced, the characteristics of the pumped storage unit can be accurately reflected, and the interaction stability of a power
system on a direct-current bus can be judged.