MPPT-Maximum Power Point Tracker is a technology to find out the Maximum Power Point of the solar cells under the sunlight. do you have any idear to this technology? let's discuss!
A maximum power point tracker (or MPPT) is a high efficiency DC to DC converter which functions as an optimal electrical load for a photovoltaic (PV) cell, most commonly for a solar panel or array, and converts the power to a voltage or current level which is more suitable to whatever load the system is designed to drive. PV 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 resistance, which is equal to V/I as specified by Ohm's Law. A PV cell has an exponential relationship between current and voltage, and the maximum power point (MPP) occurs at the knee of the curve, where the resistance is equal to the negative of the differential resistance (V/I = -dV/dI). Maximum power point trackers utilize some type 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. Traditional Solar Inverters perform MPPT for an entire array as a whole. In such systems the same current, dictated by the inverter, flows though all panels in the string. But because different panels have different IV curves, i.e. different MPPs (due to manufacturing tolerance, partial shading, etc.) this architecture means some panels will be performing below their MPP, resulting in the loss of energy.
A new approach offered by a number of companies employs panel-embedded electronics, which enables tracking the MPP of each panel individually. This approach ensures that each panel will perform at its own peak power point, independently of the other panels which may require different current due to uneven shading, soiling or electrical mismatch. Some of these solutions make use of Power Optimizers, a DC to DC converter technology developed to maximize the energy harvest from solar photovoltaic systems. Battery-less grid-tied PV inverters utilize MPPTs to extract the maximum power from a PV array, convert this to alternating current (AC) and sell excess energy back to the operators of the power grid. Off-grid power systems also use MPPT charge controllers to extract the maximum power from a PV array. When the immediate power requirements for other devices plugged into the power system are less than the power currently available, the MPPT stores the "extra" energy – energy that is not immediately consumed during the day – in batteries. When other devices plugged into the power system require more power than is currently available from the PV array, the MPPT drains energy from those batteries in order to make up the lack. MPPT charge controllers are quickly becoming more affordable and are more common in use now than ever before. The benefits of MPPT regulators are greatest during cold weather, on cloudy or hazy days or when the battery is deeply discharged. Solar MPPTs can also be used to drive motors directly from solar panels. The benefits seen are huge, especially if the motor load is continuously changing. This is due to the fact that the AC impedance across the motor is related to the motor's speed. The MPPT will switch the power to match the varying resistance.
How a Maximum Power Point Tracker Works: The Power point tracker is a high frequency DC to DC converter. They take the DC input from the solar panels, change it to high frequency AC, and convert it back down to a different DC voltage and current to exactly match the panels to the batteries. MPPT's operate at very high audio frequencies, usually in the 20-80 kHz range. The advantage of high frequency circuits is that they can be designed with very high efficiency transformers and small components. The design of high frequency circuits can be very tricky because the problems with portions of the circuit "broadcasting" just like a radio transmitter and causing radio and TV interference. Noise isolation and suppression becomes very important. There are a few non-digital (that is, linear) MPPT's charge controls around. These are much easier and cheaper to build and design than the digital ones. They do improve efficiency somewhat, but overall the efficiency can vary a lot - and we have seen a few lose their "tracking point" and actually get worse. That can happen occasionally if a cloud passed over the panel - the linear circuit searches for the next best point, but then gets too far out on the deep end to find it again when the sun comes out. Thankfully, not many of these around any more. The power point tracker (and all DC to DC converters) operates by taking the DC input current, changing it to AC, running through a transformer (usually a toroid, a doughnut looking transformer), and then rectifying it back to DC, followed by the output regulator. In most DC to DC converters, this is strictly an electronic process - no real smarts are involved except for some regulation of the output voltage. Charge controllers for solar panels need a lot more smarts as light and temperature conditions vary continuously all day long, and battery voltage changes. Below is the link to the IR solar battery charger. http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=6262
May i know how actually the maximum power point tracking system work? I mean how to determine the value of the components in boost or buck converter .
From my knowledge, the input to the dc-dc converter is from solar pv while the output of the dc-dc converter is to load. The whole process control by the adjustment of duty ratio.so may i know how to determine the value of the component in dc-dc converter because the output to the load cannot be fixed if the input and duty ratio subject to change
