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In this paper, a dc–dc boost converter with continuous input is investigated. In addition to its input current, the converter offers the advantage of using a reduced number of electronic components. The objective is to design an appropriate controller for the nonlinear model taking into account the system nonlinearities, the uncertainty of the resistance load, the constrained fuel cell current, and the saturation of the control input signal (duty ratio).The point is that the converter presents a no minimum phase feature, and the duty ratio must constrain between 0 and 1. Then, a saturated nonlinear controller is elaborated. Detailed analysis and simulation show that the proposed controller meets all control objectives, namely: tight dc-bus voltage regulation and asymptotic stability of the closed-loop system. Experimental results are also given, which show the effectiveness of the controller. [ABSTRACT FROM AUTHOR]

This paper addresses the nonlinear controller design and the stability analysis of a shunt active power filter (SAPF) interfacing a solar photovoltaic (PV) system that consists of a couple of PV panels, a single‐phase two‐stage IGBT half‐bridge SAPF and two identical DC link capacitors. We seek for the considered system the fulfillment of three control objectives: (a) extracting the maximum PV power using an appropriate maximum power point tracking (MPPT) algorithm; (b) regulation of the DC link capacitor voltages to the reference provided by the MPPT controller hence ensuring the exchange of power between the PV source and the AC power grid; (c) compensation for reactive power and undesired harmonics caused by the nonlinearity of electronic power loads, that is, performing power factor correction (PFC). The control objectives are achieved using a new two‐loop cascaded controller. The Backstepping approach is applied in the inner loop to perform PFC. A filtered proportional‐integral (PI) controller is applied in the outer loop to ensure tight regulation of the PV voltage. The MPPT control is implemented using a perturb‐and‐observe (PO) algorithm. The performance of the closed‐loop system under the two‐loop control strategy is formally analyzed through the Lyapunov approach applied to the averaged model. Numerical simulations are performed in MATLAB/SimPowerSystems environment to validate the design methodology and to confirm the theoretically predicted performances of the system under the proposed nonlinear controller. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of controlling a wind energy conversion system (WECS) based on the doubly fed induction generator (DFIG), by IGBT‐based back‐to‐back rectifier‐inverter. The goal of control is to maximize wind energy extraction letting the wind turbine rotor operate in a variable‐speed mode. Interestingly, the present study features the achievement of the above energetic goal without resorting to sensors for wind velocity. The control strategy involves: (i) an output feedback non‐linear regulator designed by the backstepping technique and based on the use of a high gain observer; (ii) a sensorless online reference‐speed optimizer designed using the turbine power characteristic to achieve the maximum power point tracking (MPPT) requirement. It is formally shown that the proposed controller actually meets its control objectives. This theoretical result is confirmed by several simulations. [ABSTRACT FROM AUTHOR]

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Abstract: This paper addresses the problem of controlling grid connected photovoltaic (PV) systems that are driven with microinverters. The systems to be controlled consist of a solar panel, a boost dc–dc converter, a DC link capacitor, a single‐phase full‐bridge inverter, a filter inductor, and an isolation transformer. We seek controllers that are able to simultaneously achieve four control objectives, namely: (i) asymptotic stability of the closed loop control system; (ii) maximum power point tracking (MPPT) of the PV module; (iii) tight regulation of the DC bus voltage; and (iv) unity power factor (PF) in the grid. To achieve these objectives, a new multiloop nonlinear controller is designed using the backstepping design technique. A key feature of the control design is that it relies on an averaged nonlinear system model accounting, on the one hand, for the nonlinear dynamics of the underlying boost converter and inverter and, on the other, for the nonlinear characteristic of the PV panel. To achieve the MPPT objective, a power optimizer is designed that computes online the optimal PV panel voltage used as a reference signal by the PV voltage regulator. It is formally shown that the proposed controller meets all the objectives. This theoretical result is confirmed by numerical simulation tests. [ABSTRACT FROM AUTHOR]

Highlights: [•] Maximum power point tracking (MPPT) in photovoltaic (PV) arrays is addressed. [•] PV system including a PV panel, a PWM DC/AC inverter connected to triphase grid. [•] Voltage reference must be designed so as to achieve maximum power point tracking. [•] Nonlinear control of the DC link voltage. [•] The power factor correction (PFC) requirement must be satisfactorily realized. [Copyright &y& Elsevier]

Abstract: The problem of controlling single-phase shunt active power filters is addressed in presence of nonlinear loads. The control objective is twofold: (i) compensation of harmonic and reactive currents absorbed by the nonlinear load, this objective is referred to as power factor correction (PFC); (ii) regulation of the inverter output capacitor voltage. A two-loop cascade control strategy is developed that includes an inner-loop designed, using the Lyapunov design approach, to cope with the compensation issue and an outer-loop designed to regulate the capacitor voltage. The controller performances are formally analysed using system averaging theory. The theoretical results are illustrated by simulation. [Copyright &y& Elsevier]

We 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. [ABSTRACT FROM AUTHOR]

This paper deals with nonlinear control and optimal management of wind energy conversion systems connected to HVDC transmission lines. Specifically, the energy system under study consists of a wind turbine driving a permanent magnet synchronous generator, the latter supplies energy to a power grid through a Vienna rectifier and a DC link. To compensate for intermittent nature of wind power and load demand variations, we design a voltage controller as well as a novel energy management strategy that accounts for the available wind power and DC load demands. In the considered management, distinction is made between two operation modes: i) the maximum power point tracking mode using an intelligent adaptive optimizer, where only electrical parameter measurements are used to ensure maximum power extraction; ii) the adaptive power point tracking mode employing demand-driven production. In both modes, the power factor requirement is ensured, regardless the weather conditions and load demand variations, enhancing thus the aerogenerator's efficiency. One more novelty of the proposed control and management system is the online estimation of the DC voltage, avoiding thus the use of a physical sensor. The performances of the control and management system are highlighted by several simulations, showing the achievement all control objectives. • SVPWM applied to the Vienna rectifier. • WECS recursive backstepping nonlinear control design. • ANFIS algorithm-based speed optimizer. • Adaptive high gain observer for HVDC transmission lines. [ABSTRACT FROM AUTHOR]

This paper presents a novel sensorless high-gain observer for wind energy conversion systems (WECS) incorporating Vienna rectifiers. Vienna rectifiers offer several advantages for WECS, including improved efficiency and signal quality. The main contribution of this study is the design of a high-gain observer that provides online estimates of magnetic and mechanical variables, such as rotor speed and load torque, based solely on electrical parameters. Addressing the challenges posed by the nonlinearity and relatively high dimensionality of the system dynamics, the proposed observer's effectiveness is demonstrated through simulations and theoretical analysis. Furthermore, experimental validation using the RTDS (Real-Time Digital Simulator) platform further confirms the performance and reliability of the observer. • Observability analysis. • Online Estimation of Magnetic and Mechanical Variables. • Sensorless control of WECS involve a Vienna rectifier. • Experimental Validation: RTDS (Real-Time Digital Simulator). [ABSTRACT FROM AUTHOR]

• The study focusses on the control development of renewable energy system constituted of a single-phase half-bridge SAPF and a couple PV arrays. • A double loop cascaded structure was adopted to deal with the control design problem. • The cascade controller is completed with an adaptive observer that performs online estimation of the grid state variables, which are not accessible to measurements. • An average large signal model is used for the stability analysis. • Practical cases are considered in simulation to prove the control performances. This paper investigates the problem of controlling a single phase shunt active power filter (SAPF) connected to two photovoltaic arrays through a half bridge inverter involving two DC link capacitors. The control aims are threefold: ensuring a satisfactory power factor correction (PFC) at the grid-power filter connection point by compensating the harmonic and reactive currents produced by the nonlinear loads; extracting a maximum active power in the output photovoltaic arrays by applying the maximum power point tracking (MPPT) block and balancing the power exchange between the photovoltaic source and the AC power grid by regulating the DC link capacitors voltages. The problem is dealt with using a cascade nonlinear adaptive controller. The inner loop is designed using sliding mode and Lyapunov stability techniques so that to ensure a unity power factor. It also includes an adaptive observer that performs online estimation of the grid state variables which are not accessible to measurements. The outer loop is mainly constituted of filtered proportional-integral (PI) regulator, that ensures a tight regulation of the photovoltaic voltage, and the incremental conductance (IC) algorithm to meet MPPT. The resulting controller performances are formally analyzed making use of averaging theory. The theoritical analysis results are confirmed by numerical simulation within MATLAB/SimPowerSystems environment. [ABSTRACT FROM AUTHOR]

• The study focusses on the control development of single stage grid-PV system. • A cascade structure was adopted to deal with the control design problem. • A steady state analysis of the PV system-power converter association is performed. • An average large signal model is used for the stability analysis. • Practical cases are considered in simulation to prove the control performances. This work presents the control development of a single stage grid-connected photovoltaic (PV) system. The topology used by the PV system consists of two PV panels, a single-phase half-bridge inverter using two DC link capacitors, and an LCL filter in the grid side. The aim is to design a nonlinear controller to ensure simultaneously the following three objectives: (i) PV panels to provide their maximum power, (ii) balanced power exchange by regulating the DC link voltage, and (iii) power factor correction, i.e. grid current in phase with grid voltage. In order to fulfill these objectives, a multi-loop controller is designed by using back-stepping and Lyapunov approaches for the power factor correction objective and a filtered PI regulator to ensure the power balance between the grid and the PV panels. The controller performances are formally analyzed using an average large signal model. The performance of the proposed controller is shown by means of simulation results in MATLAB/SimPowerSystems environment. [ABSTRACT FROM AUTHOR]