A digital control algorithm capable of separately specifying the desired output voltage and transient response for a synchronous buck converter operating in voltage mode was developed. This algorithm is based on superimposing a small control signal onto a voltage reference at each switching cycle to cancel out the perturbations. A zero steady-state error in the output voltage can be obtained with the aid of additional dynamics to allow the controller to track a load change and update the reference to a new load state. The specifications of the control algorithm are achieved by pole placement using complete state feedback. The control algorithm was implemented on a digital signal processor (DSP)-controlled synchronous buck converter.
A new strategy for controlling voltage and frequency of a self excited induction generator (SEIG) is presented. The SEIG operates in the linear region of the core magnetizing curve, so that efficiency and performance are upgraded. An external excitation circuit, comprising permanently connected capacitors and electronically switched inductances is used. The external circuit allows to compensate for the generator reactive demand. A detailed analysis is performed, showing some salient aspects related to the connection of the external excitation circuit on the control performance. Asynchronous switching is used, but some important considerations must be taken into account related to the instantaneous phase angle between stator voltage and external inductor current at the switching instant, if good transient response is desired. Sliding mode controllers are proposed, showing good dynamic response and robust behavior upon changes in load and generator parameters. Computer simulations are used to demonstrate the validity of the proposed scheme.
The input-output functional relationship of a plant is identified and expressed in explicit form over a finite time horizon, Several schemes (orthogonal expansions, ARMA and MA models) are shown to result in a similar problem formulation. The identified model is operated on the fixed structure of a discrete time PID controller, and the parameters of the latter calculated as to minimize a performance index that penalizes both the quadratic departure of the error from the desired value and large variations in the error signal therefore avoiding abrupt controller actions.Results from simulation are given in terms of tuning the PID controller of a triple effect evaporator that simulates a. real equipment used at the industry to obtain juice concentrate.
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