A system for driving a pump includes a gas turbine engine having an output shaft, and a torque converter including an input shaft coupled to the output shaft of the gas turbine engine and an output shaft configured to be coupled to an input shaft of a pump. The system further includes a controller coupled to the torque converter, wherein the controller is configured to receive a signal indicative of a pressure at at least one of a pump inlet and a pump outlet, and control a speed of the output shaft of the torque converter based on the signal indicative of pressure.