Search

This paper presents the key parameters of four different Series-Series Inductive Power Transmission (SS-IPT) configurations: (a) single phase with dual control, (b) single phase with primary side control, (c) three phase with dual control and (d) three phase with primary side control, considering two different control strategies; switching frequency and DC voltage regulations.

The work presented in this paper focuses on the estimation of the direct solar radiation on a horizontal surface using Nonlinear Autoregressive Exogenous (NARX) neural network model. This study is a part of a research project which consists in supplying a sailboat with electricity using only renewable sources. Therefore the results will be used to estimate the direct solar radiation on a tilted surface and the amount of available power from Photovoltaic in the sailboat. In this paper, the NARX neural network predicts the daily direct solar radiation using two variables: the determinist component of solar radiation and its statistical component. Due the mobility of the sailboat and the difference between the days of the year, the issue of this research is to find the best neural network to be used for the daily direct solar radiation prediction. Using several simulations, the best performance was obtained when the training phase was done periodically.

In this work, we propose a multi-objective cooperative scheduling for Smart Grids (SG) consisting of two main modules: (1) the Preference-based Compromise Builder and (2) the Multi-objective Scheduler. The Preference-based Compromise Builder generates the best balance or what we call ‘the compromise’ between the preferences or associations of sellers and buyers that must exchange power simultaneously. Once done, the Multi-objective Scheduler proposes a power schedule for the associations, in order to achieve optimal benefits from different perspectives (e.g., economical by reducing the electricity costs, ecological by minimizing the toxic gas emissions, and operational by reducing the peak load of the SG and its components, and by increasing their comfort). Conducted experiments showed that the proposed algorithms provide convincing results.

The aim of this paper is to present an alternative coil topology for ICPT (Inductively Coupled Power Transmission) links, called meander type coil, specifically for dynamic charging. The analysis is carried out using FEM software FLUX® supported by Matlab®. The goal is to design an inductive link in such a way that the coupling keeps constant while the receiver part is moving along the track, in order to make the converter and the control easier to implement. Different geometrical parameters are analyzed and compared to obtain the highest efficiency value.

ISSN : 0306-2619; International audience; MicroGrids (MGs) are one of the most useful and efficient ways to integrate renewable energy technologies in rural areas. In these areas, the biogas produced by transformation of organic waste can be electrically valorized in a MG using a Hybrid Power System (HPS) based on a Solid Oxide Fuel Cell (SOFC) and a Gas microTurbine (GT), in order to obtain a high electrical efficiency. In this study, in order to keep the best efficiency while ensuring a safe operation, the HPS is controlled using a single Three-Level Neutral Point Clamped (3LNPC) inverter. After sizing the hybrid system, digital robust R-S-T type controllers are designed to regulate the SOFC power in the DC side of the inverter and the voltage and frequency in the AC side, in an islanded MG. Then, the feasibility and the performance of the 3LNPC inverter together with the associated controllers are evaluated in simulation and experimentally using a SOFC/GT emulator.

ISSN : 0196-8904; International audience; The aim of this research study has been to design a Hybrid Power System (HPS) which works with biogas and whose main components are a Solid Oxide Fuel Cell (SOFC), a Gas microTurbine (GT), and a module of SuperCapacities (SCs). The HPS is the only power source of a rural isolated microgrid. Its structure, operating strategy, and controller have been designed considering the following criteria: efficiency, power quality, SOFC lifetime and robustness in stability and performance.The HPS structure includes a unique power converter, a 3-Level Neutral Point Clamped (3LNPC) inverter that connects the HPS to the AC microgrid. Regarding the selected operating strategy, it consists in regulating the SOFC power output to its rated value. Thus, the SCs and the GT must respond to the power demand variations. On the other hand, a study of the HPS shows that its dynamic behavior is not linear. Therefore, a special attention is put on designing a robust HPS controller. The control model is identified and the robust digital controller is designed using the “Tracking and Regulation with Independent Objectives” method. Simulation and experimental results show how the proposed structure, operating strategy, and controller allow ensuring a good behavior of the HPS from the point of view of the abovementioned four criteria.

In this paper an adaptive energy management strategy (EMS) based on fuzzy logic and the optimal sizing for a tramway with a hybrid energy storage system (ESS) combining batteries (BT) and supercapacitors (SC) are presented. The EMS applies a sliding window to estimate the forward energy consumption and adapt the instantaneous power target for BT and SC. The hybrid ESS sizing is obtained by an optimization with multi-objective genetic algorithms (GA). The fitness functions are expressed in economic terms, and correspond to the costs of the energy absorbed from the catenary as well as the operation cost of the hybrid ESS (investment and cycling cost). The selected case study is the tramway of Seville, which operates in zones with and without catenary. The aim is to minimize the daily operating cost of the tramway taking into account the BT and SC degradation approach (cycling) and fulfilling the performance of the tramway in the catenary-less zone. The proposed approach (adaptive EMS and optimal sizing) is compared with the current solution in the tramway (SC-based) and with a hybrid ESS managed by a rule-based EMS (RB-EMS) in terms of daily operating cost and energy harnessing during regenerative braking phase. The proposed approach show cost reductions up to 25.5% (from SC-based), 6.2% (from hybrid ESS with RB-EMS) and a global efficiency around 84.4%.

In this paper an optimal energy management strategy (EMS) for a hybrid electric bus (HEB) with a dual energy storage systems (ESS) combining batteries (BT) and supercapacitors (SC) is presented. The scenario considers the hybrid operation (engine+ESS), as well as the full electric operation (only ESS). Optimal targets for the proposed EMS are obtained by an optimization process with a multi-objective genetic algorithm (GA). The fitness functions are expressed in economic terms, and the aim is to minimize the daily operating cost of the HEB taking into account the BT and SC degradation approach and the performance fulfillment during bus operation in the zero-emission zone (full electric).

Regarding doubly fed induction generator (DFIG) operation, unbalanced and harmonically distorted grid voltage conditions have been treated as two separate control problems. This paper reports a solution for the rotor- and grid-side power converters, which allows one to keep the DFIG successfully in operation under both grid voltage conditions. The proposed solution is based on sliding-mode control (SMC). The rotor-side converter is commanded so that the electromagnetic torque and the stator reactive power remain free of fluctuations that arise during grid voltage disturbances. Meanwhile, the grid-side converter ensures both constant DC-link voltage and steady active power output from the overall system. The developed algorithms turn out being robust against parameter variations and of fast dynamic response. In addition, none of the converters need either voltage or current positive and negative sequences extraction. The simulation results presented demonstrate the appropriateness of SMC to face such disturbed scenarios. Finally, the stability proof of both converters' control algorithms is provided in the appendices.

Several strategies have been proposed for operating doubly-fed induction generator (DFIG)-based wind turbine under unbalanced grid voltage conditions. This study focuses on those strategies in which the rotor-side power converter aims at eliminating the oscillations affecting the electromagnetic torque and the stator reactive power. Given the limited size of the DFIG's power converters, and hence their tolerable current and voltage boundaries, this study analyzes which DFIG power generation capability is under unbalanced grid voltage, and therefrom derives rotor current and stator power controllable ranges. Besides, the feasibility regions of the DFIG are also deduced for different types of imbalance. Furthermore, and based on the outcome of previous analysis, a modified rotor current limiter, as also its equivalent stator power limiter, is proposed. In contrast to the conventional ones, the limiters proposed here take into account that imbalances may arise in the grid voltage. As a consequence, system's overall performance is considerably enhanced under unbalanced grid voltage conditions. Finally, simulation results establish the validity of the treated issues.

Nowadays, the importance of electrical generation based on renewable energies is increasing, due to its low emissions of greenhouse gases. At the same time, Distributed Generation and Microgrids (MG) are becoming an important research line because of their peculiar characteristics. MGs are composed of small power sources which can be renewable, placed near customer sites. Moreover, they have the inherent property of islanding: the disconnection of either the MG from the main grid or a portion of a MG from the rest of the MG. There are two kinds of islanding: intentional or planned (for maintenance purposes), and unintentional or unplanned. The latter is mainly due to disturbances and it is used to avoid damages in sources and loads. It is the most critical case because it must be detected as soon as possible to activate all the control systems which allow continuing the energy production and distribution despite the disconnection. In islanding, it is crucial to ensure the power and the electrical signal quality. In grid-connected mode, the inverters use the electrical signal of the main grid as reference. Once in islanding, the main grid reference is lost and new control techniques for the inverters are needed in order to obtain the correct values of voltage magnitude and frequency in the MG. The main objective of this paper is to make a survey on MGs focussed on two important features: unplanned islanding and control of inverters in that scenario. The idea is to present the basic architectures and regulation techniques of MGs and to study the islanding behaviour, mainly the different detection techniques and the inverters’ control once islanded.

International audience; A high penetration of the Renewable Energy Sources (RES) can create stability, reliability and power quality problems in the main electrical grid due to their stochastic nature. The microgrid is one of the analysed solutions to solve this problem. In this context, the storage becomes necessary to better harness the energy generated by RES and to maintain the proper operation of the microgrid. This paper addresses the control of the bidirectional DC-DC converters used to interface a parallel connected Hybrid Energy Storage System (HESS) formed by a Vanadium Redox Battery (VRB) and a SuperCapacitor (SC) bank. The linear controllers have been widely used due to their simple design and implementation. However, their operation is limited to a certain operation range. The variability of the analysed system makes the use of a more robust controller necessary. In this work a PI based two-loop control system and a PI type sliding mode controller (SMC) are compared by means of simulations using the Matlab-Simulink software. Some rules are fixed to facilitate the design process of the SMC and the advantages of using a nonlinear controller are stressed.

This paper reports a first-order sliding-mode control (1-SMC) design for controlling the doubly-fed induction generator (DFIG)-based wind turbine's rotor-side power converter. The design is particularly focused on keeping the generator successfully in operation under unbalanced grid voltage conditions, as today's grid codes require. Aside from controlling the stator-side active and reactive powers’ average value, the rotor-side converter is commanded so as to remove the fluctuations affecting the electromagnetic torque and the reactive power during unbalanced voltage. The paper aims to put forward the bases of the proposed design together with the described algorithm's stability proof. Finally, the appropriateness of the sliding-mode control to deal with the aforementioned disturbed scenarios is supported by means of simulation results.

This paper presents the design of a robust R – S – T controller of a variable speed pitch regulated wind turbine (VSPRWT) for above rated wind speeds (ARWS). An introduction of the subject and a state of the art review for controllers in ARWS are carried out. Afterwards, the studied VSPRWT and its validated model are presented. Then, the operating zone and control scheme are described. This system is non-linear and its linearising allows for the analysis of its behaviour, thereby obtaining the discrete-time control model as well as defining the controller's concrete objectives. The digital controller, which is designed following the pole assignment with sensitivity function shaping method, provides satisfactory simulation trial results.

The aim of this paper is to present the BANCO project and its first results. ESTIA had not experimental setups to make work labs in the discrete-time control courses. It is why some Alecop setups have been improved to use them in these work labs. They were prepared to be used in the Control courses of the second and the third year. The made improvements concern especially an electronic module and its programming. This module allows the students to implement discrete-time control algorithms and to observe the behaviour of some real thermal, hydraulic and mechatronic processes. The main hardware parts of this module designed and constructed in ESTIA are a microcontroller card and a signal shaping card. In addition, the module communicates with a PC in order to program it. Experimental results obtained with a discrete time R-S-T control algorithm programmed in the module are compared to those obtained with an analog PI controller already existing in the Alecop setups. Now, the setups are being improved even more in order to be able to change some parameters of the processes and to apply systems identification algorithm to these processes.

The increase of the wind power penetration in the electrical grids of Denmark, Germany, Spain and other countries and regions is challenging the stability of the system. The subject of this paper is to review the main problems of the connection of wind farms to the grid and how the grid codes must be adapted in order to integrate wind power generation capacity without affecting the quality and stability of the grid. This paper also summarizes the grid codes that have already been modified to incorporate high levels of wind power.

This paper proposes an improved control strategy for a three phase, four leg inverter used for the simultaneous supply of three phase and single phase AC loads in a transformerless hybrid power system (HPS) application. First, the mathematical model of the inverter is obtained by using the average technique, which allows converter systems to be rapidly and accurately simulated. Then, two control strategies are described. The first one uses the conventional dq0 frame rotating with the angular frequency ω (ω = 314 rad/s) and PI (proportional integral) controllers to ensure voltage and current regulation. The second one is an improved control strategy based on the decomposition of the supply three phase voltage and current into instantaneous positive, negative and homopolar sequence components using phasor representation. These three sequences are controlled independently in their own reference frames as DC signals. The positive sequence is regulated by the PI controllers in a positive reference frame, which rotates counterclockwise, while the negative sequence is regulated by the PI controllers in a negative reference frame, which rotates clockwise at the same angular frequency. Since the proposed strategy uses phasor representation, the actually superposed phasors of the homopolar sequence are spatially displaced at 120°. Then, using a negative reference frame system, the obtained DC signals are regulated by the PI controllers. Simulation results show the validity of the innovative control strategy.

The current paper presents a method to identify and estimate gross errors for linear dynamic systems using polynomial approximation. The method presented in a previous paper which uses linear dynamic reconciliation, is extended to allow the dynamic estimation of errors. This method is applied to the doubly fed induction generator (DFIG) of a wind turbine. The technique is validated on an experimental system used to emulate the working of the wind turbine.

INSPEC Accession Number: 15568986; International audience; MicroGrids (MGs) are one of the most efficient ways to integrate the renewable energy sources in the rural areas. The biogas extracted from the organic waste, an often-unused renewable resource, can be electrically valorised through a Solid Oxide Fuel Cell/Gas MicroTurbine hybrid system. In order to preserve the high electrical efficiency obtained with this kind of hybrid system, its integration into à rural MG has been done using only a 3LNPC. The paper focuses on the control strategy designed in order to allows managing the power produced by the two separate sources to meet the power demand. Simulation and experimental results, with a Solid Oxide Fuel Cell/Gas MicroTurbine hybrid system emulator and a 3LNPC prototype connected to a MG experimental platform, confirm the feasibility of the investigated system.

Wind energy technology has experienced important improvements this last decade. The transition from fixed speed to variable speed wind turbines has been a significant element of these improvements. It has allowed adapting the turbine rotational speed to the wind speed variations with the aim of optimizing the aerodynamic efficiency. A classic controller that has slow dynamics relative to the mechanical dynamics of the drive train is implemented in commercial wind turbines. The objective of the work related in this paper has been to evaluate the implementation, on a test bench, of a controller whose dynamics can be adjusted to be faster and to compare in particular its aerodynamic efficiency with the conventional controller. In theory, the higher dynamics of the non-classic controller has to lead to a better efficiency. A 180 kW wind turbine whose simulation model has been validated with field data is emulated on an 18 kW test bench. The emulator has also been validated. Test bench trials are a very useful step between numerical simulation and trials on the real system because they allow analyzing some phenomena that may not appear in simulations without endangering the real system. The trials on the test bench show that the non-conventional controller leads to a higher aerodynamic efficiency and that this is offset by higher mechanical torque and electric power fluctuations. Nevertheless, the amplitudes of these fluctuations are relatively low compared to their rated values.

This paper considers the basic principles for establishing a simulation-model of a variable speed, pitch regulated, wind turbine. This model is used to test various control algorithms designed with the aim of maximising energetic yield and robustness and minimising flicker emission and dynamic drive train loads. One of the most complex elements of such a system is the interaction between wind and turbine. First, a detailed and didactic analysis of this interaction is given. This is used to understand some complicated phenomena, and to help design a simpler and more efficient (in terms of processing time) mathematical model. Additional submodels are given for the mechanical coupling, the pitch system and the electrical power system, before the entire model is validated by comparison with filed measurements on a 180 kW turbine. The complete simulation model is flexible, efficient and allows easy evaluation of different control algorithms.

International audience; A promising solution to face the problems related to the integration of the Distributed Generation (DG) with a high renewable energy penetration level is to redesign the distribution grid using the concept of MicroGrids (MGs). Due to its constitutive components, production capacities, controllable loads and storage systems, a MG can contribute to the market either as load or production and its status can change according with the renewable energy resources availability and the needs of the main grid. The use of storage system in a MG plays an essential role in order to ensure energy balance and also allowing maintaining high power quality. In order to satisfy these two constraints, this paper proposes the association of a Vanadium Redox Battery (VRB) and SuperCapacitor (SC) bank in a Hybrid Energy Storage System (HESS). A Three-level Neutral Point Clamped (3LNPC) Inverter is used as a unique interface between the HESS and the MG. The paper focuses on the modelling and validation of the HESS, the power division limits using the 3LNPC inverter and its operation integrated in the MG. The validity of the proposed solution has been confirmed using both simulation and experimental tests.

International audience; MicroGrids (MGs) are one of the most useful and efficient ways to integrate the renewable energy technologies in the rural area, which has an often unused renewable resource: the organic waste. The biogas produced by the transformation of this primary energy resource can be valorised in a MG using a hybrid system based on a Solid Oxide Fuel Cell (SOFC) and a Gas Microturbine (GM) to obtain a high electrical efficiency. However, the demonstrators of this type of system are very few and the experimental data are rare. To approach the operation of a real system, the design and validation of hybrid SOFC/GM emulator have been proposed. The emulator will be then integrated into a rural MG in order to prove its contribution to the power quality and stability in the context of weak rural grids.

ISSN: 0967-0661; International audience; The aim of the present research work has been to design an optimal MIMO LQG controller to reduce the drive-train, blades and tower mechanical stresses of a wind turbine (WT), and at the same time, to involve the WT in the grid primary frequency regulation when it is operating in full load (FL) zone. To verify the effectiveness of the proposed controller, the achieved results are compared to those obtained by a base-line controller based on a PI regulator. Simulation results show that thanks to these controllers, WT can effectively contribute to the grid frequency regulation, tracking tightly the generator power reference which depends on that frequency. Compared with the base-line controller, the LQG controller significantly reduces the mechanical stresses of the WT׳s most costly components.

The aim of this research study has been to design a gain scheduling (GS) digital controller in order to control the voltage of an islanded microgrid in the presence of fast varying loads (FVLs), and to compare it to a robust controller. The inverter which feeds the microgrid is connected to it through an inductance-capacitor-inductance (LCL) filter. The oscillatory and nonlinear behaviour of the plant is analyzed in the whole operating zone. Afterwards, the design of the controllers which contain two loops in cascade are described. The first loop concerns the current control, while the second is linked to the voltage regulation. Two controllers, one defined as Robust and another one as GS controller, are designed for the two loops, emphasizing in their robustness and their ability to damp the oscillatory plant behaviour. To finish, some simulations are carried out to study and compare the two kinds of controllers in different operating points. The results show that both controllers damp the oscillatory behaviour of the plant in closed loop (CL), and that the GS controller ensures a better rejection of current disturbances from FVLs. The work described in this paper has been supported by European Grouping of Territorial Cooperation (EGTC) Euroregion Aquitaine-Euskadi, in the frame of their Cooperation Funds (project Colaboracion Academica e Investigadora para el Desarrollo de las Energias Renovables (CAIDER) between the University of the Basque Country (UPV/EHU) and the Ecole Superieure des Technologies Industrielles Avancees (ESTIA)).

ISSN: 0196-8904; International audience; This work analyses the use of a Three-Level Neutral Point Clamped (3LNPC) converter to control the power flow of a Hybrid Energy Storage System (HESS) and at the same time interconnect it with the common AC bus of a microgrid. Nowadays there is not any storage technology capable of offering a high energy storage capacity, a high power capacity and a fast response at the same time. Therefore, the necessity of hybridising more than one storage technology is a widely accepted idea in order to satisfy the mentioned requirements. This work shows how the operational limits of the 3LNPC converter can be calculated and integrated in a control structure to facilitate an optimal use of the HESS according to the rules fixed by the user.

International audience; The electrical networks are very complex systems, presently in full evolution. With the increasing penetration and apportionment over large areas of the renewable energies, the centralized nature of the power production evolves toward a more distributed form. In this context, the interest of the microgrids, as subcomponents of the main grid, rises especially by the specific services that they can provide. To ensure the stability and the dependability of a microgrid is a difficult task particularly in islanded mode. The microgrid is a mix of different types of elements and its structure may evolve. The multi-agents systems technique, with its distributed and adaptive character, can be an interesting tool for the control of each microgrid component and for the real time decision making related to the microgrid management. The paper starts with a presentation of microgrids and their specific issues, and follows with some basic concepts on multi-agents systems. Then, a review of the proposed techniques and algorithms that implies multi-agents systems in microgrids management is presented, focusing on the safety and the dependability in microgrids.

RESUMEN: El objetivo de este trabajo ha sido disenar un controlador digital robusto para controlar la tension de un sistema de energia hibrido aislado. La unica carga del sistema es resistiva y variable, y esta alimentada mediante un inversor asociado a un filtro LCL. Despues de plantear el problema, se explica como se obtiene el modelo de la planta. A continuacion se analiza su comportamiento dinamico oscilante y la dependencia de ese comportamiento con respecto a la carga resistiva. Se describe despues la estructura y el diseno del controlador global que contiene dos lazos de control en cascada, el primero de corriente y el segundo de tension. Se disenan los controladores de los dos lazos haciendo hincapie en su robustez y su capacidad de amortiguar el sistema en lazo cerrado. Para acabar, se realizan simulaciones en las que se estudia el comportamiento dinamico de los dos lazos en regulacion y seguimiento en distintos puntos de funcionamiento. Los resultados demuestran la calidad del control en terminos de robustez, amortiguamiento y rapidez de la respuesta. Palabras Clave: Sistema de Energia Hibrido, Control Robusto, Asignacion de Polos, Control Digital, Sistema no Estacionario, Inversores

ISBN: 978-1-4799-2984-9; International audience; The increasing penetration of Distributed Generation systems based on Renewable Energy Sources is introducing new challenges in the current centralized electric grid. Microgrids are one of the most useful and efficient ways to integrate the renewable energy technologies. As the stability of a microgrid is highly sensitive, an energy storage system is essential and it must satisfy two criteria: to have a high storage capacity and to be able to supply fast power variations. In order to satisfy these two constraints, this paper proposes the association of a Vanadium Redox Battery (VRB) and Supercapacitor (SC) bank in a Hybrid Energy Storage System (HESS). A Three-level Neutral Point Clamped (3LNPC) Inverter is used as a unique interface between the HESS and the microgrid. The paper focuses on the dynamic modelling and validation of the HESS, the power division and the modulation strategies used with the 3LNPC to mitigate the neutral point voltage unbalance effect.

ISSN: 0960-1481; International audience; The aim of this paper is to present a linear quadratic Gaussian (LQG) controller designed with two main objectives: to allow the contribution of wind turbines (WTs) to the primary frequency regulation of an island power system, and to reduce the WTs drive-train mechanical stresses. The designed LQG1_CPC_Track controller is compared, in terms of the mentioned objectives, to a more classical controller containing two uncoupled control loops. The comparison is carried out in a simulation model of the Guadeloupian island power system taken as a case study. The model is implemented in Eurostag software. Simulation results show that the contribution of both controllers to the primary frequency regulation is satisfactory, and that the LQG1_CPC_Track allows reducing drive-train mechanical stresses significantly. Thus, thanks to the LQG1_Track, on top of allowing the integration of more wind energy in the grid with the contribution to primary frequency regulation, WTs would have less maintenance costs and could be manufactured with cheaper material.

ISSN : 1553-572X Print ISBN: 978-1-4673-2419-9; International audience; The increasing penetration level of the Renewable Energy Sources (RES) and their variability can compromise the proper operation of an electrical grid. The microgrid is being analysed as a solution to obtain a high penetration of RES in a controlled way. Due to the stochastic nature of the RES, the Energy Storage Systems must be used to maintain the energy and power balance between generation and demand. The limits of the storage technologies that are nowadays available make it necessary to associate more than one storage technology creating a Hybrid Energy Storage System (HESS) in order to satisfy the specifica- tions of a microgrid application: high energy autonomy, power capacity and fast response. This paper analyses by means of simulations and experimen- tally the feasibility of a promising topology based on a Three Level Neutral Point Clamped (3LNPC) converter. The reduced power losses, improved THD and the fact of being an integrated solution are the advantages of this system. An islanding operation case study where a HESS formed by a SuperCapacitor (SC) and a Vanadium Redox Battery (VRB) supplies power to a resistive AC load that is suddenly reduced is analysed by means of simulations and experimentally. The simulation and experimental results prove the feasibility of the presented topology and of the control system to divide the power between the SC (fast power variations) and the VRB (low frequency part of the power).

ISBN: 978-1-4673-4534-7; International audience; Nowadays, a large part of the world population lives without access to electricity, principally due to the location, too far from the main grid. Renewable power sources connected in an autonomous local grid are a real opportunity for these communities. These weak electrical grids composed by several microsources, energy storage systems and loads can be considered as islanded microgrids. As it is disconnected from the main grid, the frequency and the voltage of the microgrid have to be controlled. The frequency is generally controlled maintaining the power balance between generation and consumption, using energy storage or dump loads. The voltage regulation is approached in different ways, according with the controller design objectives and the nature of the loads connected to the grid. This paper proposes a review of several voltage and frequency control strategies in islanded microgrids.

ISSN 0360-5442; International audience; The objectives of this work have been to design and analyze a discrete Linear Quadratic Gaussian (LQG) controller which contributes to the primaryfrequencycontrol of the grid and to the reduction of the drive-train fatigueloads of a WindTurbine (WT). The WT rotational speed and electrical power are controlled using the generator torque and the pitch angle as control variables. The rotational speed and electrical power references are generated in a higher control level depending on the wind speed and a frequency droop. The controller has been designed in Matlab® and has been simulated in Simulink®, in some linear simulation models corresponding to different operating points. These linear models have been obtained from a 5 MW WT model implemented in the commercial windturbine simulation tool Bladed. The results validate the efficiency of the designed controller, in comparison with another discrete LQG controller which has not been designed to reduce drive-train fatigueloads.

ISSN: 0196-8904; International audience; A high penetration rate of the Renewable Energy Sources (RES) can create stability, reliability and power quality problems in the main electrical grid. The microgrid should be a feasible alternative to solve these issues. As it is a weak electrical grid, the microgrid is very sensitive to any variation and consequently an Energy Storage System (ESS) is necessary to reduce their effect. A microgrid needs an ESS with high energy and power densities, but none of the currently available storage technologies satisfies both requirements at the same time. Consequently, it is necessary to associate more than one storage technology creating a Hybrid Energy Storage System (HESS). The objective of this work is to compare by means of simulations three different topologies that are used to control a HESS formed by a SuperCapacitor (SC) bank and a Vanadium Redox Battery (VRB). The compared topologies are the parallel active topology, the floating topology and the Three-Level Neutral Point Clamped (3LNPC) converter topology. The analysed microgrid is formed by the mentioned HESS and different renewable energy sources. This microgrid is interconnected to a weak grid based on a Diesel Generator (DG). Two case studies have been analysed: the effect of the RES while the microgrid is connected to the weak grid and the effect of the disconnection of the microgrid from the weak grid. The different topologies are compared analysing their capability of facing the mentioned variations, their power losses and their Total Harmonic Distortion (THD). The Matlab/Simulink software and the SimPowerSystems toolbox have been used to carry out the simulations.

This paper focuses on the design of Linear Quadratic Gaussian (LQG) controllers for variable-speed horizontal axis Wind Turbines (WT). These turbines use blade pitch angle and electromagnetic torque control variables to meet specified objectives for Full Load (FL) zone. The main control objectives are to reduce structural dynamic loads and to regulate the power of the WT. The controllers are designed in order to optimize a trade-off between several control objectives. Four different LQG using Individual Pitch Control (IPC) are designed, with Wireless-Sensors (WS) placed at the end of the blades for the last one. Their control model is progressively more complex. The first one takes into account a rigid simple behavior, the second control model considers the first mode of the drive-train flexibility, the third model takes into account the drive-train and tower flexibilities and the fourth that of the blades. Likewise, their optimization criteria consider for each controller a new control objective to alleviate fatigue loads in the drive-train, then, also in the tower and finally also in the blades. The evaluation of the fatigue loads affecting the WT components are based on a Rainflow Counting Algorithm (RFC) and the Miner's rule. The results indicate a significant reduction of fatigue loads especially in the drive-train and the blades when its flexibility is taken into account in the control models.

This paper focuses on the design of Linear Quadratic Gaussian (LQG) controllers for variable-speed horizontal axis Wind Turbines (WTs). Those turbines use blades pitch angle and electromagnetic torque control variables to meet specified objectives for Full Load (FL) zone. The main control objectives are to reduce the structural dynamic loads and to regulate the power of the WT. The controllers are designed in order to optimize a trade-off between several control objectives. Four different LQG controllers are designed. Their control model is progressively more complex. The first one takes into account a rigid simple behavior, the second control model considers the first mode of flexibility of the drive train, the third model takes into account the tower flexibilities and the fourth that of the blades. In the same manner, their optimization criteria considers for each controller a new control objective to alleviate fatigue loads in the drive train, then, also in the tower and finally also in the blades. The evaluation of the fatigue loads affecting the WT components are based on a Rainflow Counting Algorithm and the Miner's rule (RFC). The results indicate a significant reduction of fatigue loads in the drive-train when its flexibility is taken into account in the control model.

PurposeNowadays, distributed generation and microgrids (MGs) are becoming an important research line because of their peculiar characteristics. MGs are composed of small power sources which can be renewable, placed near customer sites. Moreover, they have the inherent property of islanding: the disconnection of either the MG from the main grid or a part of a MG from the rest of the MG. The purpose of this paper is to study two different control strategies allowing grid connected and islanding operation of the MG.Design/methodology/approachIn this paper, the behaviour of a particular MG during grid connected and islanding operation is investigated. The studied MG is based on different energy sources: a wind turbine, a photovoltaic array, a backup diesel generator and a storage system. The renewable sources and the storage system are connected on a DC bus which is interconnected with a main grid through a voltage source inverter (VSI). The attention focuses on the control technique of the VSI during grid connected and islanding operation of the MG. The behaviour of the AC signals on the point of common coupling between the MG and the main grid as well as the DC signals on the DC bus on which are connected renewable energy sources of the MG has been investigated by simulation using a MATLAB/Simulink model.FindingsFor the investigated MG, the simulation results show that using a single master VSI and classical control strategies, it is possible to have a good power quality on the MG during grid connection and islanding operation.Originality/valueThis paper investigates the behaviour of a particular MG in order to analyse two different control strategies allowing grid connected and islanding operation.

ISSN 0960-1481; International audience; Senegal is one of the less developed countries in the world (position 158 in a list of 174 countries). 85% of its rural population does not have access to electricity and there's no doubt that this is an important barrier for socio-economic development. In this context, the project Microgrids aims at contributing to solve this problem. This project is part of the Intelligent Energy - Europe Programme supported by the European Commission. Its objective is the promotion and dissemination of the use of micro-grids with high content of Renewable Energy Sources (RES) for the electrification of villages far away from the grid in Senegal. One of the results of the project was the analysis of rural electrification needs, which is described in another paper [Camblong H, Sarr J, Niang AT, Curea O, Alzola JA, Sylla EH, Santos M. Microgrids project, part 1: analysis of rural electrification with high content of renewable energy sources in Senegal. Renewable Energy, submitted for publication.]. This paper presents the design of an electrification kit based on the information provided by that analysis [Analyse des besoins locaux pour l'électrification de zones rurales au Sénégal. Technical report of Microgrids project; 2007. Available from: http://www.microgrids-eie.com.]. After identifying necessary previous conditions for the sustainability of any electrification project, a methodology is proposed for the design of the electrification kit. This methodology is applied to a typical village and results are extended to differently sized villages in the areas of Thies, Fatick and Kaolack. Economic considerations are also included to establish the relationship between electrification costs and paying capability of the communities. Now the Microgrids' consortium hopes to set-up a new project to apply the designed kit on some rural non-electrified villages.

E-ISBN : 978-1-4244-3507-4 Print ISBN: 978-1-4244-3506-7; International audience; This paper presents a DC/DC bidirectional converter with DC-link voltage controller implemented with the PLD-Microcontroller technology. The controller is designed in order to maintain constant the DC-link voltage in a hybrid power system (HPS). The means by which the functionality of the controller is implemented is given. Simulation and experimental tests were carried out using an averaged model and a laboratory prototype respectively in order to analyse the performance of the investigated converter.

Africa is the poorest continent in the world and this poverty is linked to the lack of access to energy of its population. A big part of inhabitants live in rural zones where the lack of energy and in particular of electricity is still more flagrant. The aim of the Micro-grids project was to promote the electrification of rural regions of Senegal by the installation of micro-grids with high content of renewable energies. This paper presents some results of this project. Surveys have been carried out in three regions of Senegal to study the needs of electrical energy of non-electrified rural villages' households. These surveys have led to the estimation of electricity needs of the concerned households. The potential in renewable energies of the three regions has also been examined. It has been concluded that the solar energy potential is excellent while the wind energy potential can be interesting in some specific sites. The biomass could also be an efficient source if livestock farming was properly managed in the future. Moreover, many events have been carried out in the three regions to analyse the obstacles for the development of micro-grids in the Senegalese energy context, and to establish suitable solutions to overcome these obstacles. The results presented in this paper have been used to design a rural electrification kit which is described in another paper. Now the Micro-grids' consortium hopes to set up a new project to apply the designed kit on some rural non-electrified villages.

The diagnosis of dynamic linear systems has been studied in a previous paper by using the polynomial representation of each variable. Data validation and gross error detection were investigated. This paper uses fault signature analysis to detect errors in the doubly fed induction generator (DFIG) of a wind turbine. The major contribution of this paper is that the wind turbine is operating at variable speed.

This paper presents the first results of a research project leaded by LIPSI-ESTIA concerning the association of intelligent micro sensors with advanced wind turbines (WTs) controllers to reduce the overall cost of wind energy. The sensors situated on the blades are above all used to alleviate WT fatigue loads in above rated wind speed operating area. Two multivariable gain-scheduling controllers are designed by minimizing a multiobjective H2/Hinfincriteria. One is associated to a sensor situated in the tower. The second controller is associated to sensors placed at the end of the blades. Some simulations are realized on a model of a two-bladed WT. They show that the second controller with sensors placed on the blades allows considerably alleviating WT fatigue loads.

In this paper, the implementation of an innovative inverter control strategy based on the symmetrical components is presented. Symmetrical components of the inverter output voltage and current are decomposed into dq DC quantities to control a three-phase four-leg inverter. This kind of inverter can be a good choice for the applications with hybrid power system based on renewable energy used to supply unbalanced loads. The addition of a fourth leg provides an extra degree of freedom, making possible to handle the neutral current caused by the unbalanced load. Simulation results are compared with experimental results for a prototype inverter to verify the validity of the proposed control strategy.

RESUMEN: El objetivo de este trabajo ha sido disenar un controlador digital robusto para controlar la tension de un sistema de energia hibrido aislado. La unica carga del sistema es resistiva y variable, y esta alimentada mediante un inversor asociado a un filtro LCL. Despues de plantear el problema, se explica como se obtiene el modelo de la planta. A continuacion se analiza su comportamiento dinamico oscilante y la dependencia de ese comportamiento con respecto a la carga resistiva. Se describe despues la estructura y el diseno del controlador global que contiene dos lazos de control en cascada, el primero de corriente y el segundo de tension. Se disenan los controladores de los dos lazos haciendo hincapie en su robustez y su capacidad de amortiguar el sistema en lazo cerrado. Para acabar, se realizan simulaciones en las que se estudia el comportamiento dinamico de los dos lazos en regulacion y seguimiento en distintos puntos de funcionamiento. Los resultados demuestran la calidad del control en terminos de robustez, amortiguamiento y rapidez de la respuesta. Palabras Clave: Sistema de Energia Hibrido, Control Robusto, Asignacion de Polos, Control Digital, Sistema no Estacionario, Inversores

In this paper, the transient operation of four leg voltage source converter (VSC) under unbalanced load conditions is investigated. The inverter is particularly interesting for simultaneous supply of three phase and single phase load in transformerless Hybrid Power System (HPS) application. A control strategy for the VSC based on the decomposition of the supply voltages and currents into instantaneous positive, negative and homopolar sequence components is described. The three sequences are controlled using two different rotating reference frame systems, so that the disturbance of the output voltage due to the load unbalances is eliminated. Simulation results are presented to verify the transient operation of the VSC under unbalanced load conditions.

This paper present a method to identify and estimate gross errors for linear dynamic systems. This method is applied to the Doubly Fed Induction Generator (DFIG) of a wind turbine. Gross error detection is used not only to improve the estimation accuracy of data reconciliation procedures but also to identify instrumentation problems by using statistical tests.

The purpose of this work is to compare three wind turbine controller synthesis methodologies for the whole operating range of the plant. Wind turbine controllers are designed in order to optimize a trade-off between two main control objectives which are maximization of energy efficiency and alleviation of drive train dynamic loads. The considered control synthesis approach are the linear quadratic Gaussian control approach, the discrete pole placement with sensitivity function shaping method and the inversion of causal ordering graph. Simulations show good performances and robustness of the different controllers.

This paper presents the first results of a research project leaded by LIPSI-ESTIA concerning the use of intelligent micro sensors to optimize the design of Wind Turbines (WTs) controllers. The sensors situated on the blades are above all used to alleviate WT fatigue loads in above rated wind speed operating area. Two LQG controllers are designed. One is associated to a sensor situated in the tower. The second controller is associated to sensors placed at the end of the blades. Some simulations are realized on a model of a two-bladed WT. They show that the second controller with sensors placed on the blades allow considerably alleviating WT fatigue loads.