Static frequency converter for large pumped storage units

Abstract

When starting a pumped storage unit, it needs large electromagnetic torque and small starting current. Therefore, it is necessary to use a static frequency converter to drive the machine for static starting and variable frequency operation. Hence, a high voltage static frequency converter composed of five thyristors in series for each phase of the rectifier and inverter is introduced. The rectifier adopts double closed-loop control of the speed outer loop and current inner loop, and the trigger pulse is the power frequency control. The inverter adopts different rotor position estimation methods according to the speed range, and the commutation control method of pulse commutation and load commutation is adopted. The trigger pulse is the frequency conversion control. The output of the high-voltage frequency converter can be switched from bypass operation to operation with a transformer or always with a transformer. Through experiments, it is verified that the high-voltage converter has good starting and variable frequency speed regulation performance, effective rectifier and inverter control strategy, and two reliable output operation modes.