Overview of MPPT

The MPPT system is an electrical system that can make the photovoltaic panel output more electric energy by adjusting the working state of the electric module, and can effectively store the direct current generated by the solar panel in the storage battery, which can effectively solve the problem that the conventional power grid can not cover. Living and industrial electricity in remote areas and tourist areas do not cause environmental pollution.

The output power of a photovoltaic cell is related to the operating voltage of the MPPT controller. Only when operating at the most suitable voltage will its output power have a unique maximum.

The sunshine intensity is 1000W/down, U=24V, I=1A; U=30V, I=0.9A; U=36V, I=0.7A; the output power is the largest under the voltage of 30.



The principle of MPPT

To charge the battery, the output voltage of the solar panel must be higher than the current voltage of the battery. If the voltage of the solar panel is lower than the voltage of the battery, the output current will be close to zero. Therefore, for safety reasons, the solar panel has a peak voltage (Vpp) of about 17V at the time of manufacture, which is set at a standard temperature of 25 °C. When the weather is very hot, the peak voltage Vpp of the solar panel will drop to about 15V, but in cold weather, the peak voltage Vpp of the solar energy can reach 18V.

The traditional solar charge and discharge controller is a bit like a manual gearbox. When the engine speed increases, if the gear position of the gearbox does not increase correspondingly, it will inevitably affect the speed. However, for the traditional controller, the charging parameters are set before leaving the factory. That is to say, the MPPT controller will immediately track the maximum power point in the solar panel to exert the maximum efficiency of the solar panel. The higher the voltage, the more power can be output through the maximum power tracking, thus improving the charging efficiency. In theory, the solar power system using the MPPT controller will increase the efficiency by 50% compared with the traditional one. However, according to our actual test, the final efficiency can be increased by 20%-30% due to the surrounding environment and various energy losses. . In this sense, MPPT solar charge and discharge controllers will eventually replace traditional solar controllers.



MPPT function

The main function of the MPPT controller is to detect the DC voltage and output current of the main circuit, calculate the output power of the solar array, and track the maximum power point. The disturbance resistor R and the MOSFET are connected in series, and the average current through the resistor is changed by changing the duty ratio of the MOSFET under the condition that the output voltage is substantially stable, thus causing a disturbance of the current. At the same time, the output current and voltage of the photovoltaic cell will also change accordingly. By measuring the change of the output power and voltage of the photovoltaic cell before and after the disturbance, the disturbance direction of the next cycle is determined. When the disturbance direction is correct, the output power of the solar energy panel increases. The cycle continues to perturb in the same direction, and vice versa, in the opposite direction, so that disturbances and observations are repeated to maximize the output of the solar photovoltaic panel.



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