INTRODUCTIONTOKAMAKS, AS FUTURE NUCLEAR POWER PLANTS, CURRENTLY PRE...

1. IntroductionTokamaks, as future nuclear power plants, currently present exceptionally significant re-search area. The basic problems are electromagnetic control of the plasma current, shapeand position. High-performance plasma control in a modern tokamak is the complex prob-lem (Belyakov et al., 1999). This is mainly connected with the design requirements imposedon magnetic control system and power supply physical constraints. Besides that, plasma isan extremely complicated dynamical object from the modeling point of view and usually con-trol system design is based on simplified linear system, representing plasma dynamics in thevicinity of the operating point (Ovsyannikov et al., 2005). This chapter is focused on the con-trol systems design on the base of Model Predictive Control (MPC) (Camacho & Bordons,1999; Morari et al., 1994). Such systems provide high-performance control in the case whenaccurate mathematical model of the plant to be controlled is unknown. In addition, thesesystems allow to take into account constraints, imposed both on the controlled and manip-ulated variables (Maciejowski, 2002). Furthermore, MPC algorithms can base on both linearand nonlinear mathematical models of the plant. So MPC control scheme is quite suitable forplasma stabilization problems.In this chapter two different approaches to the plasma stabilization system design on the baseof model predictive control are considered. First of them is based on the traditional MPCscheme. The most significant drawback of this variant is that it does not guarantee stabilityof the closed-loop control circuit. In order to eliminate this problem, a new control algorithmis proposed. This algorithm allows to stabilize control plant in neighborhood of the plasmaequilibrium position. Proposed approach is based on the ideas of MPC and modal paramet-ric optimization. Within the suggested framework linear closed-loop system eigenvalues areplaced in the specific desired areas on the complex plane for each sample instant. Such areasare located inside the unit circle and reflect specific requirements and constraints imposed onclosed-loop system stability and oscillations.It is well known that the MPC algorithms are very time-consuming, since they require therepeated on-line solution of the optimization problem at each sampling instant. In order to re-duce computational load, algorithms parameters tuning are performed and a special methodis proposed in the case of modal parametric optimization based MPC algorithms.The working capacity and effectiveness of the MPC algorithms is demonstrated by the exam-

Bode Diagram

ple of ITER-FEAT plasma vertical stabilization problem. The comparison of the approaches is

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done.

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