Extremal harmonic active control of power for rotating machines

Most of the time, the speed of rotating machines oscillates in synchronization with the rotor position. Those speed fluctuations, generated by disturbance torques, can be actively controlled with a second torque source coupled to the shaft of the machine. To achieve this active control, the problem is reformulated in the harmonic domain with regard to the main order of the fluctuations. The control objective is to extremalize an energetic criterion like kinetic energy (cancelling the speed ripple), reactive power (to add a virtual flywheel) or active power (to charge a battery). To reach those objectives, two extremal controllers are proposed with implicit or explicit criterion management. The controllers are tested on an academic test bed. The results show that the controllers converge at the extremum of each criterion.