Hierarchical control of interconnected systems with slow and fast modes-application to the control of a doubly fed synchronous machine

We study the control of inter-connected systems with slow and fast modes. The classical approach of control was to reduce the model of the system by keeping only the slow modes. This approach has the advantage to simplify the control problem, however it has the disadvantage to lose some states of the system. The hierarchical approach of control is proposed to solve such a problem. In fact, it permits to resolve reduced order models at the lower stages of the control hierarchy by decomposing the global system into several subsystems corresponding to each mode. By this way, the control problem of the global system is resolved with no states lost and by using reduced order subsystems. To validate our approach, we apply the hierarchical control to a doubly fed synchronous machine (DFSM) having a sixth order model with 3 modes