Flatness-based control and observer design scheme for hybrid synchronous machines

In this paper, a nonlinear control-oriented model of the hybrid synchronous machine is developed using the dq-axis transformation. A flatness-based multi-variable controller is proposed to track a predefined reference trajectory for the angular velocity. Furthermore, a comparison is made for two alternative observer designs. In the first case, a combination of a gain-scheduled Luenberger-type state observer and a nonlinear reduced-order observer is used to estimate the angular velocity and the load torque of the mechanical load connected to the hybrid synchronous machine, respectively. In the second case, only a nonlinear reduced-order observer is used to estimate both the angular velocity and the load torque. A simulation analysis highlights the effectiveness of the control strategy with excellent tracking behavior as well as small estimation errors of both angular velocity and load torque.