Equilibrium analysis of doubly fed-based variable-speed pumped storage unit under remote grid fault

Abstract

As the flexible-controlled power source in the power system, the doubly fed-based variable-speed pumped storage unit (DF-VSPSU) has a significant role in the power rebalance and the reactive power support. However, as with the voltage sag in the remote grid side, the DF-VSPSU with the conventional low-voltage ride-through control may lose the synchronization and result in instability due to the absence of an equilibrium point. Thus, taking a DF-VSPSU infinite system as a case, the generator-side, and the grid-side model is well established. The large disturbance instability mechanism of doubly fed-based variable-speed pumped storage unit under remote grid faults is explained in detail, which is caused by the absence of the equilibrium point. Together with the key influencing factors, including the voltage depth and the short circuit ratio, the available gain of the reactive current control is presented. Finally, the availability of the theoretical analysis is demonstrated based on MATLAB/Simulink.

Keywords

• Doubly fed-based variable-speed pumped storage unit
• Equilibrium point
• Style
• Reactive gain coefficient
• Remote grid fault