The performance of a photovoltaic (PV) array is affected by temperature, solar insolation, shading, and array configuration. Often, the PV arrays get shadowed, completely or partially, by the passing clouds, neighboring buildings and towers, trees, and utility and telephone poles. The situation is of particular interest in case of large PV installations such as those used in distributed power generation schemes. Under partially shaded conditions, the PV characteristics get more complex with multiple peaks. Yet, it is very important to understand and predict them in order to extract the maximum possible power. This paper presents a MATLAB-based modeling and simulation scheme suitable for studying the I-V and P-V characteristics of a PV array under a nonuniform insolation due to partial shading. It can also be used for developing and evaluating new maximum power point tracking techniques, especially for partially shaded conditions. The proposed models conveniently interface with the models of power electronic converters, which is a very useful feature. It can also be used as a tool to study the effects of shading patterns on PV panels having different configurations. It is observed that, for a given number of PV modules, the array configuration (how many modules in series and how many in parallel) significantly affects the maximum available power under partially shaded conditions. This is another aspect to which the developed tool can be applied. The model has been experimentally validated and the usefulness of this research is highlighted with the help of several illustrations. The MATLAB code of the developed model is freely available for download.

Abstract-Current-voltage and power-voltage characteristics of large photovoltaic (PV) arrays under partially shaded conditions are characterized by multiple steps and peaks. This makes the tracking of the actual maximum power point (MPP) [global peak (GP)] a difficult task. In addition, most of the existing schemes are unable to extract maximum power from the PV array under these conditions. This paper proposes a novel algorithm to track the global power peak under partially shaded conditions. The formulation of the algorithm is based on several critical observations made out of an extensive study of the PV characteristics and the behavior of the global and local peaks under partially shaded conditions. The proposed algorithm works in conjunction with a dc-dc converter to track the GP. In order to accelerate the tracking speed, a feedforward control scheme for operating the dc-dc converter is also proposed, which uses the reference voltage information from the tracking algorithm to shift the operation toward the MPP. The tracking time with this controller is about one-tenth as compared to a conventional controller. All the observations and conclusions, including simulation and experimental results, are presented.Index Terms-Global peak (GP), maximum power point tracking (MPPT), partial shading, power-voltage (P -V ) characteristics.

Abstract-This paper proposes a high performance, single-stage inverter topology for grid connected PV systems. The proposed configuration can not only boost the usually low photovoltaic (PV) array voltage, but can also convert the solar dc power into high quality ac power for feeding into the grid, while tracking the maximum power from the PV array. Total harmonic distortion of the current, fed into the grid, is restricted as per the IEEE-519 standard. The proposed topology has several desirable features such as better utilization of the PV array, higher efficiency, low cost and compact size. Further, due to the very nature of the proposed topology, the PV array appears as a floating source to the grid, thereby enhancing the overall safety of the system. A survey of the existing topologies, suitable for single-stage, grid connected PV applications, is carried out and a detailed comparison with the proposed topology is presented. A complete steady-state analysis, including the design procedure and expressions for peak device stresses, is included. Necessary condition on the modulation index " " for sinusoidal pulsewidth modulated control of the proposed inverter topology has also been derived for discontinuous conduction mode operation. All the analytical, simulation and experimental results are presented.

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Abstract-This paper presents a new algorithm for tracking maximum power point in photovoltaic systems. This is a fast tracking algorithm, where an initial approximation of maximum power point is (MPP) quickly achieved using a variable step-size. Subsequently, the exact maximum power point can be targeted using any conventional method like the hill-climbing or incremental conductance method. Thus, the drawback of a fixed small step-size over the entire tracking range is removed, resulting in reduced number of iterations and much faster tracking compared to conventional methods. The strength of the algorithm comes from the fact that instead of tracking power, which does not have a one-to-one relationship with duty cycle, it tracks an intermediate variable , which has a monotonically increasing, one-to-one relationship. The algorithm has been verified on a photovoltaic system modeled in Matlab-Simulink software. The algorithm significantly improves the efficiency during the tracking phase as compared to a conventional algorithm. It is especially suitable for fast changing environmental conditions. The proposed algorithm can be implemented on any fast controller such as the digital signal processor. All the details of this study are presented.Index Terms-Maximum power point (MPP) tracking, photovoltaic.

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Abstract-A new switching control algorithm based on state trajectory approximation is proposed to regulate the output voltage of a representative second-order dc-dc converter-the boost converter. The essence of the proposed algorithm is to trap the system into a stable limit cycle while ensuring the required voltage regulation. Unlike some of the earlier algorithms, the concept is applicable to both continuous and discontinuous current modes of operation, making it viable over a wide operating range under various load and line disturbances. A hybrid-automaton representation of the converter is used to perform the analysis, and the control problem is simplified to a guard-selection problem. Guard conditions, governing the transition of the converter operation from one discrete state to the other in a hybrid-automaton representation, are derived. The hybrid-automaton-based control system is implemented by using the state flow chart feature of MATLAB, and extensive simulations are carried out to check the suitability of the algorithm. The hybrid control law is also validated in real time by using a laboratory prototype. The experimental and simulation results prove the effectiveness of the proposed control law under varying line and load conditions.

Abstract-This paper presents a novel maximum power point (MPP) tracking (MPPT) algorithm for grid-connected wind energy generation systems (WEGS). This is a rapid tracking algorithm that uses the fact that the value of "β," an intermediate variable, especially defined for the purpose, remains constant (=β M P P ) for a given WEGS at the MPP irrespective of the wind velocity. The value of β M P P is known in advance. The algorithm works in two stages. In the first stage, it uses large steps to quickly drive the operating point to lie within a narrow band with limits β m ax and β m in . In the second stage, exact MPP is tracked using the "perturb and observe" method. No extra hardware or measurements (sensors) are required compared to the existing algorithms. Hence, the cost is not increased. Application of the proposed algorithm to an example WEGS shows that the time taken by the system to reach MPP is much smaller compared to most of the existing algorithms. A prototype matrix converter has been developed for grid interfacing and the proposed MPPT scheme has been implemented in conjunction with Venturini and space-vector-modulation-based switching schemes. All the results of this study are presented.Index Terms-Matrix converter (MC), maximum power point tracking (MPPT) algorithm, space vector modulation (SVM), squirrel cage induction generator (SCIG), Venturini, wind energy generation system (WEGS).