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 (P&O) maximum power point tracking
algorithm is the most commonly used method due to its ease of implementation.
A drawback of P&O is that, at steady state, the operating
point oscillates around the MPP giving rise to the waste of
some amount of available energy; 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
Abstract-One of the major drawbacks of photovoltaic (PV) systems is represented by the effect of module mismatching and of partial shading of the PV field. Distributed maximum power point tracking (DMPPT) is a very promising technique that allows the increase of efficiency and reliability of such systems. Modeling and designing a PV system with DMPPT is remarkably more complex than implementing a standard MPPT technique. In this paper, a DMPPT system for PV arrays is proposed and analyzed. A dc and small-signal ac model is derived to analyze steady-state behavior, as well as dynamics and stability, of the whole system. Finally, simulation results are reported and discussed.
In double-stage grid-connected photovoltaic (PV) inverters,
the dynamic interactions among the dc/dc and dc/ac stages
and the maximum power point tracking (MPPT) controller may
reduce the system performances. In this paper, the detrimental
effects, particularly in terms of system efficiency and MPPT performances,
of the oscillations of the PV array voltage, taking place
at the second harmonic of the grid frequency are evidenced. The
use of a proper compensation network acting on the error signal
between a reference signal provided by theMPPT controller and a
signal that is proportional to the PV array voltage is proposed. The
guidelines for the proper joint design of the compensation network
(which is able to cancel out the PV voltage oscillations) and of the
main MPPT parameters are provided in this paper. Simulation
results and experimental measurements confirm the effectiveness
of the proposed approach
The use of one-cycle control (OCC) for maximum power point tracking (MPPT) and power factor correction (PFC) in grid connected photovoltaic (PV) applications is discussed. Circuit and operating parameters of the one cycle-based controller of a cost-effective single-stage inverter are optimized in order to obtain the best performances of the system under different irradiance levels. Firstly, design constraints are formulated which allow to get a very efficient OCC operation in terms of power extracted from the PV array, stability, and PFC. Afterwards, such constraints are used to perform the parametric optimization of the one cycle controller by means of suitable heuristic approaches. Various selection criteria of the best parameters set under different conditions are discussed and applied. Finally, a customized perturb and observe (P&O) control is applied to the optimized one cycle controlled single-stage inverter in order to perform a real MPPT in presence of varying irradiance conditions. Subjects described here are covered by the Italian Patent Application SA2005A000014-13.07.2005 and PCT Application PCT/IT2005/000747-20.12.200
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