In general electrical equipment, if the load resistance is equal to the internal resistance of the power supply system, the maximum power can be obtained on the load. Since solar cells are an extremely unstable power supply, that is, the output power changes at any time with factors such as the intensity of sunlight, weather, temperature, etc., it is necessary to use maximum power point tracking control technology and circuits to track the changes in the power output of solar cells and obtain the maximum power generation power of solar cells or the value near the maximum power generation power in real time.
At present, the commonly used maximum power point control method is to control the solar cell or array to work at the maximum power point through the power switching device in the DC/DC converter, thereby realizing maximum power tracking control. It can be seen from the output power characteristic P-U curve of the solar cell shown in Figure that the highest point of the curve is the maximum power point of the solar cell output, and the curve is divided into left and right sides with the maximum power point as the boundary.
When the solar cell works at point D on the right side of the maximum power point voltage and is significantly far away from the maximum power point, the tracking control circuit will automatically lower the output working voltage of the solar cell, so that the output power point shifts from point D to point C, and the output power increases; similarly, when the solar cell works at point A on the left side of the maximum power point voltage, the tracking control circuit will automatically increase the output working voltage of the solar cell, so that the output power point shifts from point A to point B, so that the output power increases.
The maximum power point tracking control process is actually a self-optimization process of the tracking control circuit, similar to the "hill climbing method". By detecting the current output voltage and current of the photovoltaic module, the output power of the current photovoltaic module is obtained, and then compared and adjusted with the output power of the photovoltaic module at the previous moment that has been stored, the smaller one is discarded and the larger one is selected, and then detected, compared, and adjusted again. This cycle is repeated continuously, so that the photovoltaic module can dynamically work at the maximum power point.
More complex maximum power point tracking control methods include classical control algorithms such as the perturbation observation method and the incremental conductance method, as well as modern control algorithms such as the optimal gradient method, the fuzzy logic control method, and the neural network control method.