Turbo-alternator stalling protection using available-power estimate

In environments where electromechanical loads may suffer from disturbances with large magnitude-such as in sampling downhole reservoirs-stalling protection for the power source of the alternator may be critical to prevent potentially catastrophic system failure. First, a real-time estimation method is described to determine the maximum available electrical power produced by a turbo-alternator for a given volumetric flow rate acting on the turbine. Next, the available-power estimate and used electrical power measurement are used to prevent turbine stalling by regulating an electromechanical load-in this case a permanent magnet synchronous motor (PMSM)-to draw less power. The stalling protection is implemented through an additional proportional-integral-derivative (PID) controller for load power, which is cascaded outside already cascaded velocity and torque PID controllers used for control of the PMSM. To ensure fast tracking, the power PID controller implements integral anti-windup. An experimental evaluation of the methodology is presented.