This paper presents the design and implementation of a photovoltaic emulator, based on an accurate mathematical model of a photovoltaic panel, instead of the look-up table method. The latter requires more memory for increasing accuracy and considering all the desired environmental situations. Furthermore, the proposed approach takes into account the incidence solar angle, as an input parameter, to offer the possibility of evaluating daily losses for different values of tilt angle. The validation of the proposed emulator is carried out by comparing in real-time, both the studied panel output and the emulator output, under variable load, temperature, and irradiation levels. The emulator is able to operate online with connected solar radiation and temperature sensors or offline with recorded measurement vectors. The practical tests were performed on a prototype designed using a MATLAB C MEX S-function, dSPACE board 1104, and a controlled DC/DC converter. The results showed that the emulator was able to behave accurately as the studied photovoltaic panel.

In this paper, an adaptive fault tolerant control strategy is proposed to deal with the three pitch actuator faults in the large-scale wind turbines. Firstly, a simultaneous state and fault estimation was performed through a suitable LMI (linear matrix inequality) based optimal strategy. Hereafter, the new control law is designed using the previously estimated fault information. The actuator efficiency estimator uses as design parameters, respectively, the performance index γ against the wind and the learning rate Ξ. of the fault estimation algorithm. The study shows that the choice of the previous two parameters impacts the response time of the fault estimation and the correlation of the tracking error with the wind. The aim is to choose a small fault estimation response time while keeping a weak correlation between the tracking error and the wind turbulence noise. Finally, a tuning strategy is elaborated to choose the suitable γ and Ξ to match the reconfiguration objective.

An accurate method is proposed to track the maximum power point of a photovoltaic module. The method is based on the analytical value of the maximum power point voltage, determined from a mathematical model of the photovoltaic panel. The method has the advantage of accuracy without any oscillations, as with certain conventional methods. The algorithm has also the ability to track accurately the maximum power point under variable atmospheric conditions and load changes. Experimental results are presented to show the effectiveness of the method. The implementation of the method needs an online measurement of irradiance, panel temperature, and panel current and voltage.

Abstract:In this paper we propose a concept for estimating solar irradiation based on measurements of the current, voltage, and temperature of a photovoltaic (PV) cell.The estimation of the irradiation is obtained by processing these measurements using a PV cell mathematical model combined with a PI controller. Since the PV cell current is very sensitive to the irradiance level, the principle of the method is to force the model to reproduce the same current as that measured on the cell by applying an appropriate irradiance as input, for measured temperature and voltage. The appropriate irradiance, which is the output of our estimator, is provided by the PI controller in such way that the current estimated by the model follows exactly the measured current. The PI controller ensures also self-calibration of the PV reference cell depending on the temperature changes. The effectiveness of the proposed approach has been validated in a simulation and implemented in real time using the dSpace 1104 board.

This paper presents the analysis, design, and simulation of a power system composed of a grid-tied single-phase five-level inverter with an LCL filter. First, the analysis of the proposed system has been carried out in the decoupled Direct-Quadrature frame, where the Phase-Lock-Loop technique has been used for synchronizing the LCL-filter-connected-grid with the five-level inverter. Next, the design of the LCL filter has been discussed. In this paper, we focused on the active power control based on grid current adjustment using a proportional-integral regulator and a high-frequency modulation technique for the switching of a five-level inverter, where the Sinusoidal-Pulse-Width-Modulation technique is selected. All circuit design and control schemes are discussed step by step to provide the effectiveness of the system analysis. The theoretical analysis is verified through simulation results in MATLAB/Simulink environments. An important finding when using the five-level inverter in a grid-connect system is improving the system output voltage; the total standing voltage and the total harmonic distortion are decreased compared to a conventional H-bridge inverter. The results indicate that the total harmonic distortion of grid-current is less than 0.2%, which is according to the international standards.