Romeu Reginatto

Analysis of regions of stability for linear systems with saturating inputs through an anti-windup scheme

The purpose of this paper is to study the use of anti-windup gains for obtaining larger regions of stability for linear systems with saturating inputs. Considering that a linear dynamic output feedback has been designed to stabilize the linear system (without saturation), a method is proposed for designing an anti-windup gain that maximizes the estimation of the basin of attraction of the closed-loop system. It is shown that the closed-loop system obtained from the controller plus the anti-windup gain can be locally modeled by a linear system with a deadzone nonlinearity. From this model, stability conditions based on quadratic and Lure type Lyapunov functions are stated. Algorithms based on LMI schemes are proposed for computing both the anti-windup gain and an associated region of stability.

Brief Robust tuning of the speed loop in indirect field oriented control of induction motors

In this paper, we analyze the occurrence of Hopf bifurcations in indirect field-oriented control of induction motors and derive guidelines for setting the PI speed controller in order to keep the bifurcations far enough from the operating conditions in the parameter space.

Adding Active Power Regulation to Wind Farms with Variable Speed Induction Generators

Larger wind power integration in the power system requires generated power regulation in wind farms. In this work, an active power control system for wind farms equipped with variable speed wind turbines is proposed, aiming at minimizing the active power variations due to wind speed variations. The proposed control scheme achieves the active power regulation goal without significative reduction in total power production of the wind farm, and takes advantage of the non-uniform wind distribution along the farm. Employing suitable tools for wind power forecast, such performance can still be improved. With this methodology, the wind power generation drawbacks are reduced, allowing a better integration of the wind energy into the power system.

Instability mechanisms in indirect field oriented control drives: Theory and experimental results

Abstract Analysis of saddle-node and Hopf bifurcations in IFOC drives due to errors in the estimate of the rotor time constant is presented. Experimental results showing such bifurcations are given and guidelines for drive commissioning are derived from these results.

ZERO-HOPF BIFURCATION IN INDIRECT FIELD ORIENTED CONTROL OF INDUCTION MOTORS

Abstract In this paper we explore the occurrence of zero-Hopf bifurcation in indirect field oriented control (IFOC) of induction motors. Codimension-two Bogdanov-Takens bifurcations as well as codimension-one saddle-node and Hopf bifurcations have been reported earlier. In this paper the occurrence of codimension-two zero-Hopf bifurcation in IFOC is analyzed and proven to occur under certain parameter settings. Bifurcations diagrams are also reported illustrating such bifurcations for a particular IFOC drive.

CONSERVATIVITY OF ELLIPSOIDAL STABILITY REGIONS ESTIMATES FOR INPUT SATURATED LINEAR SYSTEMS

Abstract This paper presents a comparative study of different existing algorithms for determining stability domains for linear systems with saturating inputs. Algorithms based on the solution of LMI problems carried out on the basis of three different saturation models, namely regions of saturation, differential inclusion, and sector modeling, are analyzed and compared in terms of their ability to provide large stability domains for the closed-loop system. The main reasons such algorithms incorporate conservativity are highlighted, this being the main contribution of this paper. Results are illustrated by means of an example.

Anti-windup design with guaranteed regions of stability for discrete-time linear systems with saturating controls

The purpose of this paper is to study the determination of stability regions for discrete-time linear systems with saturating controls through anti-windup schemes. Considering that a linear dynamic output feedback has been designed to stabilize the linear discrete-time system (without saturation), a method is proposed for designing an anti-windup gain that maximizes an estimate of the basin of attraction of the closed-loop system in the presence of saturation. It is shown that the closed-loop system obtained from the controller plus the anti-windup gain can be modeled by a linear system connected to a deadzone nonlinearity. From this model, stability conditions based on quadratic Lyapunov functions are stated. Algorithms based on LMI schemes are proposed for computing both the anti-windup gain and an associated stability region.

Application of hybrid and polytopic modeling to the stability analysis of linear systems with saturating inputs

Este artigo trata do problema de determinacao de regioes de estabilidade para sistemas lineares com entradas saturantes. O trabalho foca-se em uma analise critica de duas abordagens conhecidas para o modelamento dos efeitos da saturacao de controle: modelamento hibrido e modelamento politopico. Em cada caso, algoritmos para determinar dominios de estabilidade para a classe de sistemas considerada sao propostos em termos de LMIs. A habilidade de tais algoritmos em fornecer grandes dominios de estabilidade e analisada, enfatizando-se as principais fontes de conservatismo, incluindo o proprio modelamento da saturacao. Dois exemplos sao apresentados a fim de ilustrar o quao diferente podem ser os dominios de estabilidade obtidos com os diferentes algoritmos.

Global stabilizaton with improved performance for linear systems with actuator saturation

This paper deals with the global stabilization problem of linear systems with saturating actuators. Global stabilization is achieved by scheduling a parameterized control law constructed from a parameterized solution of the algebraic Riccati Equation (ARE). The scheduling algorithm is guided by the magnitude of the control signal and reduces conservativeness of similar existing schemes. Several important properties of this algorithm regarding its functionality, design parameters, implementation issues, and capabilities are discussed. Simulation results for a case study are included illustrating the main features of the control scheme and the overall performance of the closed loop system.

A Microcontrolled System Applied to Process Control Analysis and Design

Abstract This work describes a Microcontrolled System which allows simultaneous (or single use) operation of fuzzy logic control, PID control and system simulation. The software is dynamically reconfigurable, to allow on-line changes in the system structure. The main idea is to have a software-hardware system which allows the implementation of many different test patterns related to control systems, such as the performance comparison of control algorithms. The proposed approach supports process simulation as well as real-time interfacing to real processes. Results are presented showing the main features of the system.