Co-Ordination of multiple Controllers using Non Linear – Control Techniques
Ø Several nonlinear-control techniques have been applied for the design of FACTS controllers. These techniques are likely to yield greatly improved controllers, as they include the effects of system nonlinearities.
Ø Some of these methods are described briefly in the following text. One nonlinear-control technique in which the system nonlinearities are expressed as system changes constituting a function of time is the adaptive control.
Ø If the number of controller parameters to be optimized is not too large, a cost-penalty function technique can be used, which is based on nonlinear simulation.
Ø An effective technique commonly used for enhancing transient stability during large disturbances is the discontinuous control or bang-bang control.
Ø Another nonlinear-control technique is the normal forms, which includes the effects of higher-order terms in Taylor’s series to represent power systems especially during high-power transfers. For damping low-frequency oscillations, FACTS controllers can be designed using the dissipation technique, which is based on the concept that passive systems always absorb energy. For designing the controls of FACTS controllers in large power systems, the energy, or Lyapunov, technique can be used. For stability enhancement, nonlinear fuzzy and neural net techniques are presently being researched.
Ø In the future, these techniques may be extended for coordination of FACTS controllers. One possible approach could be to first do a “coarse” coordination using linear-control techniques, followed by a “fine” coordination employing the nonlinear-control methods.
“The Quantitative treatment of control coordination”
1. Coordination of multiple controllers using linear control techniques.
2. Coordination of multiple controllers using non linear control techniques.
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