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Maximum power point tracking (MPPT) is a technique that charge controllers use for wind turbines and PV solar systems to maximize power output. PV solar systems exist in several different configurations. The most basic version sends power from collector panels directly to the DC-AC inverter, and from there directly to the electrical grid. A second version, called a hybrid inverter, might split the power at the inverter, where a percentage of the power goes to the grid and the remainder goes to a battery bank. The third version is not connected at all to the grid but employs a dedicated PV inverter that features the MPPT. In this configuration, power flows directly to a battery bank. A variation on these configurations is that instead of only one single inverter, micro inverters are deployed, one for each PV panel. This allegedly increases PV solar efficiency by up to 20%. New MPPT equipped specialty inverters now exist that serve three functions: grid-connecting wind power as well as PV , and branching off power for battery charging . This article about the application of MPPT concerns itself only with PV solar. Solar cells have a complex relationship between temperature and total resistance that produces a non-linear output efficiency which can be analyzed based on the I-V curve. It is the purpose of the MPPT system to sample the output of the PV cells and apply the proper resistance (load) to obtain maximum power for any given environmental conditions. MPPT devices are typically integrated into an electric power converter system that provides voltage or current conversion, filtering, and regulation for driving various loads, including power grids, batteries, or motors. * Solar inverters convert the DC power to AC power and may incorporate MPPT: such inverters sample the output power (I-V curve) from the solar modules and apply the proper resistance (load) so as to obtain maximum power. * MPP(Maximum power point) is the product of the MPP voltage(Vmpp) and MPP current(Impp). ==I-V curve == Photovoltaic cells have a complex relationship between their operating environment and the maximum power they can produce. The fill factor, abbreviated ''FF'', is a parameter which characterizes the non-linear electrical behavior of the solar cell. Fill factor is defined as the ratio of the maximum power from the solar cell to the product of Open Circuit Voltage Voc and Short-Circuit Current Isc. In tabulated data it is often used to estimate the maximum power that a cell can provide with an optimal load under given conditions, ''P=FF *Voc *Isc''. For most purposes, FF, Voc, and Isc are enough information to give a useful approximate model of the electrical behavior of a photovoltaic cell under typical conditions. For any given set of operational conditions, cells have a single operating point where the values of the current (''I'') and Voltage (''V'') of the cell result in a maximum power output. These values correspond to a particular load resistance, which is equal to ''V'' / I as specified by Ohm's Law. The power P is given by ''P=V *I''. A photovoltaic cell, for the majority of its useful curve, acts as a constant current source. However, at a photovoltaic cell's MPP region, its curve has an approximately inverse exponential relationship between current and voltage. From basic circuit theory, the power delivered from or to a device is optimized where the derivative (graphically, the slope) ''dI/dV'' of the I-V curve is equal and opposite the ''I/V'' ratio (where d''P/dV''=0). This is known as the maximum power point (MPP) and corresponds to the "knee" of the curve. A load with resistance ''R=V/I'' equal to the reciprocal of this value draws the maximum power from the device. This is sometimes called the 'characteristic resistance' of the cell. This is a dynamic quantity which changes depending on the level of illumination, as well as other factors such as temperature and the age of the cell. If the resistance is lower or higher than this value, the power drawn will be less than the maximum available, and thus the cell will not be used as efficiently as it could be. Maximum power point trackers utilize different types of control circuit or logic to search for this point and thus to allow the converter circuit to extract the maximum power available from a cell. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Maximum power point tracking」の詳細全文を読む スポンサード リンク
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