Optimized servo-speed control of wind turbine coupled to doubly fed induction generator

Optimal control of any variable speed wind turbine needs maximum power point tracking (MPPT) coupled to doubly fed induction generator (DFIG) for better power generation. This paper offers a novel direct power servo-speed control of wind turbine. This latter is based on DFIG optimal hysteresis MPPT inverter current control combined with space voltage modulation (SVM) inverter voltage technique, thus providing a stable and continuous energy flow to power grid. In this design, the asynchronous machine stator is directly connected to the grid. Bidirectional power converter, acting as frequency converter, is rotor circuit located. Rectifier supplies rotor windings with voltages and reference frequency resulting from control procedure of the power exchange between the stator and grid. Inverter is directly controlled by means of SVM technique to maintain direct current (DC) bus voltage constant. Simulation results show that the proposed configuration improves power converters efficiency due that rotor circuit needs less power than stator circuit which is injected into the grid

FPGA-Based Hardware in the Loop of Optimized Synergetic Controller for Active Power Filter

This paper presents a discrete-time synergetic controller (DTSC) enhanced with ant colony optimization (ACO) technique for a shunt active power filter (SAPF). The developed controller is designed under MATLAB/Simulink environment; then, field-programmable gate array (FPGA) in the loop (FIL) technique is used to implement the DTSC model. The proposed DTSC parameters are optimally tuned according to ACO methodology. The DTSC-ACO should enhance power quality and eliminate grid current harmonics using an indirect current-controlled three-phase SAPF. Note that, the designed FPGA controller integrates the items needed to drive the SAPF. This digital implementation satisfies the hardware and recommended performance. In fact, it reduces significant resources and execution time. The experimental validation is carried out on Virtex-6 ML605 FPGA Xilinx Evaluation Kit using VIVADO processing. A total harmonic distortion (THD = 2.72%) is obtained for the grid current. Thus, the results obtained confirm proper operation of the developed approach. In addition, the proposed DTSC shows good dynamic performance during load step change and output voltage variation

Real-Time Genetic Algorithms-Based MPPT: Study and Comparison (Theoretical an Experimental) with Conventional Methods

Maximum Power Point Tracking (MPPT) methods are used in photovoltaic (PV) systems to continually maximize the PV array output power, which strongly depends on both solar radiation and cell temperature. The PV power oscillations around the maximum power point (MPP) resulting from the conventional methods and complexity of the non-conventional ones are convincing reasons to look for novel MPPT methods. This paper deals with simple Genetic Algorithms (GAs) based MPPT method in order to improve the convergence, rapidity, and accuracy of the PV system. The proposed method can also efficiently track the global MPP, which is very useful for partial shading. At first, a review of the algorithm is given, followed with many test examples; then, a comparison by means Matlab/Simulink© (R2009b) is conducted between the proposed MPPT and, the popular Perturb and Observe (PO) and Incremental Conductance (IC) techniques. The results show clearly the superiority of the proposed controller. Indeed, with the proposed algorithm, oscillations around the MPP are dramatically minimized, a better stability is observed and increase in the output power efficiency is obtained. All these results are experimentally validated by a test bench developed at LIAS laboratory (Poitiers University, Poitiers, France) using real PV panels and a PV emulator which allows one to define a profile insolation model. In addition, the proposed method permits one to perform the test of linearity between the optimal current I mp (current at maximum power) and the short-circuit current I sc , and between the optimal voltage V mp and open-circuit voltage V oc , so the current and voltage factors can be easily obtained with our algorithm

Active Power Filtering Using the ZDPC Method under Unbalanced and Distorted Grid Voltage Conditions

In this paper, we propose a new Zero Direct Power Control (ZDPC) technique for active compensation of harmonics and reactive power, using shunt active power filter (SAPF), based on cancellation of instantaneous active and reactive power disturbances by comparison with their zero references. To separate harmonic and fundamental components of the line voltage and current a highly selective filter (HSF) has been used. Depending on the power errors and line voltage vector position, a switching table produces the appropriate control vectors leading to the active and reactive power variation required to reach the zero power references, even under grid voltage unbalanced and distorted conditions. The experimental validation of the proposed ZDPC has been performed. The results are compared to other recent techniques to demonstrate the superiority and feasibility of the proposed strategy

Filtrage actif triphase pour charges non linéaires

Cette thèse s'inscrit dans le cadre d'actions curatives afin d'améliorer la qualité de l'énergie et particulièrement compenser la pollution harmonique, la puissance réactive mais aussi les déséquilibres. Un filtre actif parallèle triphasé (SAPF) constitue le dispositif de dépollution et un pont PD3 alimentant une impédance de type R-L représente la charge non linéaire. Après une modélisation de la structure du SAPF, une synthèse sur l'estimation des paramètres le constituant, tel que la tension du bus continu Vdc, la valeur de la capacité de stockage Cdc et de l'inductance de couplage ou filtre de sortie Lf, nous a permis d'obtenir les paramètres optimaux qui sont exploités en simulation et de façon expérimentale. Avec des techniques de commande du type suivi de consigne, une PLL multivariable et un régulateur de type IP ont été synthétisés et leur stabilité et robustesse ont été confirmées avant d'être introduits dans les stratégies de commande développées. A partir des mesures des courants et des tensions du réseau respectivement isi, vsi, ainsi que de la tension du bus continu Vdc, des techniques de commande en courant, en tension et en puissance ont été élaborées et analysées en simulation puis validées expérimentalement sur le banc d'essai du laboratoire. Une comparaison détaillée est établie avec comme critères la simplicité d'implémentation, la stabilité et la robustesse de la commande aux différents régimes équilibré et déséquilibré, la présence de la HF et finalement la qualité de l énergie fournie relativement aux normes imposées.This thesis is in keeping with the general pattern of curative operations in order to improve energy quality and particularly to make up for harmonic pollution, reactive power but also unbalances. A three-phase shunt active power filter (SAPF) constitutes the disturbances mitigation device and a PD3 bridge feeding a type R-L impedance represents the nonlinear load. After a modelling of the SAPF structure, a synthesis on the parameters estimation, such as the DC voltage Vdc, the value of storage capacity Cdc and the coupling inductance or output filter Lf, enabled us to obtain the optimal values of parameters which are exploited in simulation and in an experimental way. With techniques based on tracking control design, a multivariable PLL and a type IP regulator were synthesized and their stability and robustness were confirmed before being introduced into the developed strategies of order. From network currents and voltages measurements respectively isi, vsi, as well as DC voltage Vdc, control techniques were worked out running in current, in voltage and power and analyzed in simulation then validated in laboratory experiment test bench. A detailed comparison is made with criteria as the simplicity of implementation, the stability and the robustness of the order to the various modes balanced and unbalanced, the HF presence and finally the energy quality provided relating to the imposed standards.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Techniques de commande prédictive et floue pour les systèmes électroniques de puissance (application aux redresseurs MLI)

Cette thèse s'inscrit dans les travaux de recherche menés sur les moyens modernes, à base de l'électronique de puissance, de dépollution harmonique du réseau de distribution de l'énergie électrique. Cette pollution constitue actuellement un problème majeur surtout dans l'industrie. Elle est causée principalement par les charges non linéaires, prélevant sur le réseau des courants non sinusoïdaux. Les convertisseurs statiques, surtout les redresseurs à diodes et à thyristors, sont de nature non linéaire et représentent la principale source d'injection de courants harmoniques. Ils requièrent donc une attention particulière afin de réduire leurs taux d'harmonique en courant. Dans ce contexte, les solutions modernes préventives adoptées, en plus du filtrage actif qui représente une solution curative, consiste à remplacer les redresseurs classiques par de nouvelles structures de convertisseurs AC/DC non polluants, dont le comportement vis-à-vis du réseau est de nature résistive. Ce travail apporte une contribution à la commande du redresseur de tension à MLI à absorption de courant sinusoïdal. En effet, différentes stratégies de commande ont été développées, simulées et validées sur un banc d'essai expérimental dont le but commun est d'obtenir un réglage performant de la tension du bus continu et un prélèvement de courants sinusoïdaux. Ces stratégies sont basées soit sur le contrôle direct des courants absorbés soit sur le contrôle direct des puissances instantanées (DPC). De plus, elles sont combinées avec des commandes dites avancées, comme les approches floue et prédictive appliquées aux deux techniques de contrôle énoncées précédemment. La simulation de ces méthodes a été mise en oeuvre à l'aide du logiciel Matlab/SimulinkTM et l'implantation en temps réel a été élaborée grâce à une carte contrôleur du système dSPACE 1104.This work deals with harmonic elimination in electrical energy distribution networks. In fact, harmonic pollution has become a major field of concern in modern industry. It is usually caused by non linear loads, which draw non sinusoidal current from the network. Current harmonics are mainly caused by static converters, especially diode and thyristor rectifiers, because they have a non linear behaviour and represent the main source of currents harmonics injection. Therefore, some measures must be taken in order to reduce current harmonic distortion caused by this equipment. In this field, the advanced preventive solutions adopted, other than active filters which are curative method, is to substitute the conventional rectifiers with new structures of AC / DC non-polluting converters, which have resistive behaviour towards the network. This research work contributes to the control of PWM rectifier with sinusoidal current absorption. That is why, various control strategies have been developed for this converter in order to obtain an efficient control of the DC bus voltage and nearly sinusoidal input current waveforms. These strategies are based either on direct control of input currents or direct power control (DPC). Moreover, they are combined with advanced controls like approaches with fuzzy logic and predictive control applied to the two preceding methods. Simulations presented in this work are performed with Matlab/SimulinkTM tools, and practical implementation in real time has been done through a system controller board dSPACE 1104.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

A Robust Control of Two-Stage Grid-Tied PV Systems Employing Integral Sliding Mode Theory

This contribution considers an improved control scheme for three-phase two-stage grid-tied photovoltaic (PV) power systems based on integral sliding mode control (ISMC) theory. The proposed control scheme consists of maximum power point tracking (MPPT), DC-Link voltage regulation and grid current synchronization. A modified voltage-oriented maximum power point tracking (VO-MPPT) method based on ISMC theory is proposed for design of an enhanced MPPT under irradiation changes. Moreover, a novel DC-Link voltage controller based on ISMC theory is proposed to achieve good regulation of DC-Link voltage over its reference. To inject the generated PV power into the grid with high quality, a voltage-oriented control based on space vector modulation (SVM) and ISMC (VOC-ISMC-SVM) has been developed to control the grid current synchronization. Numerical simulations are performed in a MATLAB/SimulinkTM (R2009b, MathWorks, Natick, MA, USA) environment to evaluate the proposed control strategy. In comparison with conventional control schemes, the developed control strategy provides an accurate maximum power point (MPP) tracking with less power oscillation as well as a fast and an accurate DC-Link regulation under varying irradiation conditions. Moreover, the transfer of the extracted power into the grid is achieved with high quality

A high-performance control scheme for photovoltaic pumping system under sudden irradiance and load changes

A low-cost photovoltaic (PV) pumping system based on three phase induction motor (IM) without the use of chemical energy storage elements is presented in this paper. The PV generator-side boost converter performs the maximum power point tracking (MPPT), while the IM−side two-level inverter regulates the net DC-link voltage and the developed electromagnetic torque by IM, which is coupled with a centrifugal pump. An improved variable step size perturb and observe (P&O) algorithm is proposed to reduce the steady-state PV power fluctuation, to accelerate the tracking operation under sudden irradiance changes, and to protect IM under load drops. The proposed algorithm is based on a current control approach of the boost converter with a model predictive current controller to select the optimal control action. Moreover, predictive torque and flux control (PTC) is used to control IM drive, due to its advantages such as faster torque response, lower torque ripple, and simplicity of implementation. Furthermore, a Takagi-Sugeno (T-S) type fuzzy logic controller (FLC) is developed in order to regulate the DC-link voltage, by producing the torque reference for PTC algorithm. In order to examine and assess the performance of the proposed control scheme for PV pumping system, a complete simulation model is developed using MATLAB/SimulinkTM environment and confirmed through real-time hardware in the loop (HIL) system. The obtained results indicate the excellent performance of the proposed control scheme, which is much better than the conventional scheme based on conventional techniques (P&O algorithm and direct torque control (DTC))