Control of Variable Speed Pumped Storage Unit Based on Power Electronic Transformer Under Unbalance of Power Grid Voltage

To enhance the power density and improve the grid-connection capability of the variable-speed pumped storage unit, this paper proposes a topology for full-power variable-speed pumped storage based on power electronic transformer. This topology does not require a power frequency transformer and can isolate the double frequency fluctuation of the high-voltage DC bus voltage in the event of asymmetric faults in the grid, so as not to affect the control of the motor side and improve the unit's ability to adapt to the power grid.