Nonlinear Pulse Width Modulation Research Articles

One-cycle control application to wind turbine power control

Summary In this paper, a one-cycle control (OCC)-based approach for wind turbines equipped with doubly fed induction generators (DFIGs) is presented. The OCC is used to control back-to-back converter which includes generator-side converter and grid-side converter. The former is used for regulating generator speed, and the latter is used for controlling reactive power. Also, particle swarm optimization is used to improve the accuracy of parameters of PI controllers. The proposed approach is studied under different conditions, including load change, fault and nonlinear loads. Also, uncertainty of wind speed is considered. Moreover, a comparison between pulse width modulation (PWM)-based and OCC-based controllers is done. The OCC is a non-linear PWM method so its control technique turns a non-linear switch into a linear path. In contrast to the traditional PWM method, OCC control realizes PWM and fast/nonlinear control simultaneously by modulating the slope of the saw-tooth waveform. The simulation results show that accuracy and speed control of DFIG converter by OCC are superior in comparison with conventional control strategies from tracking reference signal and oscillations point of view. Copyright © 2014 John Wiley & Sons, Ltd.

Dynamic compensator design in nonlinear aerospace systems

Based on differential algebraic results, dynamic controllers are proposed for the feedback regulation of typical aerospace systems. Fliess's generalized observability canonical form (GOCF) is used for specifying a dynamic compensator that smoothly regulates the plant dynamics. The synthesis approach used is also applicable to the design of nonlinear pulsewidth-modulation (PWM) controllers, as well as to sliding-mode control strategies. The three underlying nonlinear control techniques, explored with the aid of illustrative examples, are commonly encountered in aerospace control system design problems. Simulations are also included. >

Invariance conditions in non-linear PWM controlled systems

A geometric approach is used to demonstrate that Pulse-Width-Modulation (PWM) controlled systems exhibit perturbation invariance properties identical to those exhibited by dynamical systems undergoing sliding motions on discontinuity surfaces. At the core of the result is the existence of an ideal equivalence among sliding regimes of Variable Structure Feedback (VSF) control and Pulse-Width-Modulated (PWM) control responses.