SDM hybrid control approach for nonlinear systems and its application to power systems

This paper proposes a new approach, which may tentatively be called as SDM hybrid control for affine nonlinear systems. A class of non-minimum phase nonlinear control systems can hardly be linearized completely just via state feedback. It is revealed in this paper that the skill of dynamic extension and so-called SD feedback (state and dynamic feedback) could be helpful to achieve the linearized part with higher dimensions of such kind of nonlinear systems so as to obtain better control effects. Furthermore, for a class of engineering control systems, the models involve some complicated nonlinear functions that can be measured directly. That useful feature could and should be applied to controller design, thereby forming SM feedback (state and measurement feedback), which is defined and employed to simplify the controller design. It is also demonstrated that SM feedback is favorable to apply to decouple interconnected systems and achieve decentralized control. Integrating both SD and SM feedback methods, the SDM hybrid control approach is proposed. As applications of it, the nonlinear optimal governor controller for hydroturbine-generator sets is taken as examples for illustration. The micro-alternator tests are performed on one-machine, infinite-bus (OMIB) system and the computer ones are carried on an 8-machine, 36-buses system respectively. The results of both physical and digital tests manifest that the performances and stability of the system are markedly improved comparing with conventional PID controllers, which also verify the promising prospective of the proposed approach.