The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.

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Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques

This paper proposes a method of modeling and simulation of photovoltaic arrays. The main objective is to find the parameters of the nonlinear I-V equation by adjusting the curve at three points: open circuit, maximum power, and short circuit. Given these three points, which are provided by all commercial array data sheets, the method finds the best I-V equation for the single-diode photovoltaic (PV) model including the effect of the series and parallel resistances, and warranties that the maximum power of the model matches with the maximum power of the real array. With the parameters of the adjusted I-V equation, one can build a PV circuit model with any circuit simulator by using basic math blocks. The modeling method and the proposed circuit model are useful for power electronics designers who need a simple, fast, accurate, and easy-to-use modeling method for using in simulations of PV systems. In the first pages, the reader will find a tutorial on PV devices and will understand the parameters that compose the single-diode PV model. The modeling method is then introduced and presented in details. The model is validated with experimental data of commercial PV arrays.

Comprehensive Approach to Modeling and Simulation of Photovoltaic Arrays

Maximum power point tracking (MPPT) techniques are used in photovoltaic (PV) systems to maximize the PV array output power by tracking continuously the maximum power point (MPP) which depends on panels temperature and on irradiance conditions. The issue of MPPT has been addressed in different ways in the literature but, especially for low-cost implementations, the perturb and observe (PO moreover, it is well known that the P&O algorithm can be confused during those time intervals characterized by rapidly changing atmospheric conditions. In this paper it is shown that, in order to limit the negative effects associated to the above drawbacks, the P&O MPPT parameters must be customized to the dynamic behavior of the specific converter adopted. A theoretical analysis allowing the optimal choice of such parameters is also carried out. Results of experimental measurements are in agreement with the predictions of theoretical analysis.

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Optimization of perturb and observe maximum power point tracking method

Maximum power point tracking (MPPT) techniques are employed in photovoltaic (PV) systems to make full utilization of PV array output power which depends on solar irradiation and ambient temperature. Among all the MPPT strategies, the incremental conductance (INC) algorithm is widely used due to the high tracking accuracy at steady state and good adaptability to the rapidly changing atmospheric conditions. In this paper, a modified variable step size INC MPPT algorithm is proposed, which automatically adjusts the step size to track the PV array maximum power point. Compared with the conventional fixed step size method, the proposed approach can effectively improve the MPPT speed and accuracy simultaneously. Furthermore, it is simple and can be easily implemented in digital signal processors. A theoretical analysis and the design principle of the proposed method are provided and its feasibility is also verified by simulation and experimental results.

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A Variable Step Size INC MPPT Method for PV Systems

Review of the maximum power point tracking algorithms for stand-alone photovoltaic systems

As the maximum power operating point (MPOP) of photovoltaic (PV) power generation systems changes with changing atmospheric conditions (e.g. solar radiation and temperature), an important consideration in the design of efficient PV systems is to track the MPOP correctly. Many maximum power tracking (MPT) techniques have been considered in the past but techniques using microprocessors with appropriate MPT algorithms are favoured because of their flexibility and compatibility with different PV arrays. Although the efficiency of these MPT algorithms is usually high, it drops noticeably in cases of rapidly changing atmospheric conditions. The authors have developed a new MPT algorithm based on the fact that the MPOP of a PV generator can be tracked accurately by comparing the incremental and instantaneous conductances of the PV array. The work was carried out by both simulation and experiment, with results showing that the developed incremental conductance (IncCond) algorithm has successfully tracked the MPOP, even in cases of rapidly changing atmospheric conditions, and has higher efficiency than ordinary algorithms in terms of total PV energy transferred to the load.

Maximum photovoltaic power tracking: an algorithm for rapidly changing atmospheric conditions

In this paper, the authors have investigated, both by simulation and experimentally, the effect of matching the field and armature windings on the performance of a separately excited DC motor interfaced to two photovoltaic (PV) arrays. Special emphasis has been placed on matching the load line of the field winding which, if directly connected, intersects the I-V characteristics of the array at a voltage close to the open circuit voltage resulting in a very small excitation current and hence poor motor performance. Step-up choppers were used as impedance transformers to match the motor windings to the maximum power lines of the PV arrays. The motor was coupled to a torque meter and the step-up choppers were PWM controlled by a personal computer (PC). The importance of matching the field winding was clearly illustrated whereas matching only the armature winding did not significantly improve the system efficiency.

Field and armature control for separately excited DC motors powered by photovoltaic cells

Charging a SMES Coil using Photovoltaic Energy

In this paper the authors have designed an experimental system to optimize the matching of a separately excited DC-motor interfaced to two PV arrays. Special emphasis has been placed on matching the load line of the field winding which, if directly connected to the PV array, intersects the V-I characteristics of the array at a voltage close to the open circuit voltage resulting in a very small excitation current and hence poor motor performance. Step-up choppers were used as impedance transformers to match the load lines of the field and armature windings to the maximum power lines of the PV arrays. The motor was coupled to a brake torque meter acting as a mechanical load and the step-up choppers were PWM controlled by a personal computer. The system efficiency defined as the ratio between the motor output mechanical power (calculated using the motor torque and speed) to the input power available from the PV arrays, was evaluated for four control modes as follows: applying no control, controlling only the armature winding, controlling only the field winding, and controlling both windings. The importance of controlling the field winding was clearly illustrated whereas controlling only the armature winding didn't significantly improve the system efficiency and this was because most of the input power was wasted in the form of heat in the armature winding due to the poor field excitation.

Khalid Hassan Hussein

Papers

Maximum photovoltaic power tracking: an algorithm for rapidly changing atmospheric conditions

Field and armature control for separately excited DC motors powered by photovoltaic cells

Charging a SMES Coil using Photovoltaic Energy

Maximum Photovoltaic Power Flow to a Separately Excited DC Motor