The energy produced using a photovoltaic (PV) is mainly dependent on weather factors such as temperature and solar radiation. Given the high cost and low yield of a PV system, it must operate at maximum power point (MPP), which varies according to changes in load and weather conditions. This contribution presents an improved maximum power point tracking (MPPT) controllers of a PV system in various climatic conditions. The first is a sliding mode MPPT that designed to be applied to a buck converter in order to achieve an optimal PV array output voltage. The second MPPT is based on the incremental conductance algorithm or Perturb-and-Observe algorithm. It provides the output reference PV voltage to the sliding mode controller acting on the duty cycle of the DC-DC converter. Simulation is carried out in SimPower toolbox of Matlab/Simulink. Simulation results confirm the effectiveness of the sliding mode control MPPT under the parameter variation environments and shown that the controllers meet its objectives.

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The main contribution of this work is to propose an efficient and accurate method for identifying and determining the values of equivalent circuit elements of photovoltaic module using only exact analytical equations and four manufacture's data reference, i.e., the open-circuit voltage (VOC) , the short-circuit current (ISC) and the current and the voltage at the maximum power point (IM , VM). All used equations were obtained with a transparent analytical procedure. To avoid using any mathematical simplifications or other physical assumptions when extracting RS (series resistance) parameter, a fast and accurate iterative numerical method is proposed. For determine a four or five PV parameters model, many authors proposed several procedures that require the entire experimental I-V curves or based on many estimations, assumptions and simplifications for solving non-linear I-V equations. These techniques lead to a PV parameters model with a minimum error. We apply this combined method in order to extract the four-parameter Single-Diode models of photovoltaic modules. The effectiveness of this approach is evaluated and validated by Matlab/Simulink environment, through comparison of simulation results of the model to the data provided by product's manufacturer. It envisaged that this work is very useful for PV power electronics designers who require exact, fast and accurate approach for modeling emulating their photovoltaic modules under various environmental conditions.

This paper focuses on the problem of controlling a single phase DC-AC switched power converter used in Uninterruptible Power Supply (UPS). The control objective is to generate, at the system output, a sinusoidal voltage with amplitude and frequency fixed by the reference signal. To this end, three types of regulators are designed based on Backstepping technique, Sliding Mode approach and linear PID controller. A comparative study of performances of designed controllers is made by simulations in Matlab/Simulink environment.

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