| Abstract |
Both in Europe and in USA, the induction motors are the major energy consumers [1]-[3]. According to the estimation of their power distribution and energy consumption, 83% of the total amount of electric motors is consumed by the 0.75-7.5 kW electric motors in Europe [3]. By using a quadratic energetically performance criteria offered by the optimal control theory [5]-[7] the problem formulation was done with fixed time, free-end point, unconstrained, the matrix Riccati differential equation (MRDE) having to be solved. Consequently, in order to cover all power range in [7]-[9] the optimal control based on energetic criteria for squirrel cage induction motors was synthesized. The optimal control law has three components: the state feedback, the forcing component to achieve the desired state x1 and the compensating feed forward of the perturbation w(t). Obviously, the analytical solution supposes the knowledge of the perturbation w(t)=Tl(t), which could be available by using a torque observer as in [10]. The rotor field oriented induction motor (IM) is controlled at constant flux, the optimal control synthesis consisting of the determination of the stator three-phase currents system, based on the longitudinal and transversal components of the stator phasor current. The purpose of this paper is to implement the optimal control such that the properties of the MRDE solution (obtained from the numerical integration) are maintained, and much more, to extend their availability to nonlinear systems or to the systems in which the parameters are unknown. Therefore, the fuzzy logic approach is shown in this paper. The energetic efficient electric drive (EEED) is designed to deliver the same output power with less electrical power input [11]. The result of EEED using is 8 to 25% units increase in efficiency [11]. Through the normalization process of the input and output variables, the optimal solution becomes available for any type of induction motors power. The optimal control law oriented to the vector controlled induction machine provides dynamic regimes, smooth response, no oscillations of the vector state and of the control on the dynamic period, without overshoot, the fast compensation of the load torque with minimal energy consumption, and robust performances. |
