A New Control Strategy for Photovoltaic System Connected to the Grid via Three-Time-Scale Singular Perturbation Technique with Performance Analysis

This chapter addresses the problem of controlling single-phase grid-connected photovoltaic system through a full bridge inverter with L-filter. The control objectives are threefold: (i) forcing the voltage in the output of photovoltaic panel to track a reference. This reference has been obtained from the maximum power point tracking strategy; (ii) guaranteeing a tight regulation of the DC-link voltage; and (iii) ensuring a satisfactory power factor correction (PFC) at the grid such as the currents injected must be sinusoidal with the same frequency and the same phase as the grid voltage. The considered control problem entails several difficulties including: (i) the high dimension and strong nonlinearity of the system; (ii) the changes in atmospheric conditions. The problem is dealt with by designing a synthesized nonlinear multi-loop controller using singular perturbation technique, in which a three-time-scale dynamics is artificially induced in the closed-loop system. A formal analysis based on the three-time-scale singular perturbation technique and the averaging theory is developed to proved that all control objectives are asymptotically achieved up to small harmonic errors (ripples). The performance of the proposed approach and its strong robustness with respect to climate changes are evaluated based on the various simulations results carried out under Matlab/Simulink software

State Feedback Nonlinear Control Strategy for Wind Turbine System Driven by Permanent Magnet Synchronous Generator for Maximum Power Extraction and Power Factor Correction

This chapter addresses the problem of controlling the Complete chain of the wind turbine system using the permanent magnet synchronous generator (PMSG) connected with the Distribution network via an AC/DC/AC converters through LCL filter, the control to be applied in different parts of the system, whose objectives are three: (1) adjust the generator speed to track a varying reference signal; (2) the control of the network-side converter must be maintained the current injected into the network in a unit power factor correction (PFC); (3) regulating the DC Link voltage at a constant value. Firstly, the mathematical modeling for all system components studied in d-q frame and its state space equation are established to simplify the proposed control, thereafter a nonlinear backstepping approach is used in this work to achieve the objectives indicated above. The performance of the proposed approach is evaluated based on the various simulations results carried out under Matlab/Simulink/Simpower software

Commande de convertisseurs statiques de puissance AC/DC en vue de la correction du facteur de puissance et du pilotage de la charge ( développement d'une approche formelle pour la synthèse de régulateurs et l'analyse des performances)

Cette thèse porte sur la commande des convertisseurs de puissance AC/DC fonctionnant en commutation à travers un générateur à modulation de largeur d impulsions. L intérêt de cette classe de convertisseurs réside dans son rendement énergétique élevé et sa capacité à fonctionner en mode de conduction continue minimisant ainsi les interférences électromagnétiques, conduites et rayonnées. L objectif de commande est double : (i) régulation du signal de sortie (tension aux bornes d une charge résistive, vitesse d une charge motrice) ; (ii) assurer une connexion avec un facteur de puissance quasi-unitaire (PFC) entre le convertisseur et le réseau de puissance. Le problème est appréhendé en développant une stratégie de commande impliquant deux régulateurs montés en cascade. Le régulateur interne est conçu de telle sorte que le courant absorbé à l entrée du convertisseur soit proportionnel à la tension sinusoïdale du réseau d alimentation. L entrée de référence de ce régulateur (le rapport de proportionnalité mentionné) est aussi le signal de commande du régulateur externe qui vise à réguler le signal de sortie (tension ou vitesse). Les régulateurs sont élaborés à partir du modèle non linéaire du système commandé, en utilisant différentes techniques de synthèse. Le système de commande en boucle fermée résultant s avère non linéaire et temps variant. En utilisant des outils d analyse appropriés, tels que ceux de stabilité et de moyennage, nous démontrons formellement que les objectifs de commande sont réalisables en moyenne avec une erreur qui dépend de la fréquence du réseau d alimentation. Cette erreur est d autant plus petite que la fréquence du réseau est plus élevéeThis thesis deals with switched PWM AC/DC power converters. The interest of this type of converters lies in their high power efficiency and their ability to operate in continuous conduction mode minimizing thus electromagnetic interferences, both conducted and radiated. The control objective is twofold: (i) output signal regulation (output voltage for resistive type load, speed for motor type load); (ii) ensuring a unit power factor (PFC) connection between the converter and the power supply net. The problem is dealt with developing a control strategy involving two regulators in cascade. The inner regulator is designed to make the current absorbed by the converter proportional to the supply net voltage. The reference signal of this regulator is also the control signal of the outer regulator which aims at regulating the system output (voltage or speed). Both regulators are obtained from the nonlinear model of the converter, using different control techniques. The resulting closed-loop system turns out to be nonlinear and time-varying. Using suitable stability and averaging tools, it is formally demonstrated that the control objectives are achieved in the mean with an error that depends on the supply net frequency. The larger the net frequency is the smaller the error..CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

DC motor velocity adaptive control through Buck-Boost AC/DC Converter with Power Factor Correction

International audienceThis paper deals with the problem of velocity control of DC motors taking account the dynamics of the involved power converter. The latter is an AC/DC Buck Boost type. First, a 6th order model is developed for the global system, constituted of the motor and the converter. Based on this model, a regulator is then designed, using the backstepping technique, to achieve speed regulation and unitary power factor operation. The proposed regulator involves three loops: (i) an inner current control loop enforcing the converter input current to be in phase with the electric network voltage (unitary power factor), (ii) an outer speed control loop that regulates the machine velocity, (iii) a parameter adaptation loop that compensates the load torque uncertainty. The resulting multi-loop adaptive nonlinear regulator is formally proved to meet its objectives. This is further checked by simulation

Commande non-linéaire avancée d'un compensateur statique synchrone: analyse théorique des performances en boucle fermée

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Sensorless Adaptive Observer of Wind Synchronous Generator

6 pagesInternational audienceControlling electrical drives without mechanical sensors at the machine shaft has several benefits e.g. low cost and high reliability. To avoid these sensors, state observers must be resorted to get the required information using only measured voltages and currents at the machine terminals. In this paper we are considering the problem of estimating mechanical state variables in permanent magnet synchronous generators driven by wind turbines through AC/DC rectifiers and DC/AC inverters. Only the electrical variables are supposed to be accessible to measurements. Then a sensorless interconnected adaptive observer of the high-gain type is designed to get online estimates of the rotor position and speed as well as the load torque. Parameter adaptation is resorted because the load torque is not supposed to be known. The proposed state observer is formally proved to be globally convergent if its gains are conveniently chosen. This theoretical result is confirmed by simulations which, besides, show that the observer convergence is quite robust with respect to wind speed (or load torque) uncertainties

Formal framework for nonlinear control of PWM AC/DC boost rectifiers - Controller design and average performances analysis

International audienceWe are considering the problem of controlling filtered AC/DC switched power converters of the boost type. The control objectives are twofold: 1) guaranteeing a regulated voltage for the supplied load and 2) enforcing power factor correction (PFC) with respect to the main supply network. The considered problem is dealt with using a double-loop controller developed on the basis of the system nonlinear model. The inner-loop is designed by the backstepping technique to cope with the PFC issue. The outer-loop is designed to regulate the converter output voltage. Experimental tests show that the proposed controller actually meets the objectives it is designed for. While similar performances have been experimentally demonstrated, for different converters and controllers, it is the first time that a complete and rigorous formal analysis, based on averaging theory, is developed to describe the observed performances (PFC and output voltage ripples). As a matter of fact, the averaging theory constitutes the natural framework to analyzing the performances due to the periodic nature of the system input signals

Robust control of synchronous motors through AC/DC/AC converters

International audienceThe problem of controlling synchronous motors, driven through AC/DC rectifiers and DC/AC inverters is addressed. The control objectives are three fold: (i) forcing the motor speed to track a varying reference signal in presence of motor parameter uncertainties;(ii) regulating the DC Link voltage; (iii )assuring a satisfactory power factor correction (PFC) with respect to the power supply net .First, a nonlinear model of the whole controlled system is developed in the Park-coordinates. Then, a robust nonlinear controller is synthesized using the damping function version of the back stepping design technique. A formal analysis based on Lyapunov stability and average theory is developed to describe the control system performances. Despite parameter uncertainties,all control objectives are proved to be asymptotically achieved up to unavoidable but small harmonic errors (ripples)

Nonlinear Control Design and Averaging Analysis of Full-Bridge Boost Rectifier

International audienceWe are considering the problem of controlling AC/DC full bridge converters. The control objectives are twofold: (i) guaranteeing a regulated voltage for the supplied load, (ii) enforcing power factor correction (PFC) with respect to the main supply network. The considered problem is dealt with using a nonlinear controller that involves two loops in cascade. The inner-loop is designed, using sliding mode approach, to cope with the PFC issue. The outer-loop is designed to regulate the converter output voltage. While several double-loop regulators (designed for different converters) can be found in the relevant literature, it is the first time that a so formal average analysis is developed that rigorously describes the controller performances. The development of such theoretical analysis framework is a major motivation of this pape

Modeling and Nonlinear Control of a Wind Turbine System Based on a Permanent Magnet Synchronous Generator Connected to the Three-phase Network

This article presents nonlinear control of wind conversion chain connected to the grid based on a permanent magnet synchronous generator. The control objectives are threefold; i) forcing the generator speed to track a varying reference signal in order to extract the maximum power at different wind speed (MPPT); ii) regulating the rectifier output capacitor voltage; iii) reducing the harmonic and reactive currents injected in the grid. This means that the inverter output current must be sinusoidal and in phase with the AC supply voltage (PFC). To this end, a nonlinear state-feedback control is developed, based on the average nonlinear model of the whole controlled system. This control strategy involves backstepping approach, Lyapunov stability and other tools from theory of linear systems. The proposed state-feedback control strategy is tested by numerical simulation which shows that the developed controller reaches its objective