Application of Power Analyzer and MPPT in Photovoltaic Power Generation Industry

In photovoltaic power generation systems, an important way to improve the overall efficiency of the system is to adjust the operating point of the photovoltaic cells in real time, so that they always work near the maximum power point. This process is called maximum power point tracking(maximum power point tracking, MPPT).

1MPPTBasic Principles

In theory, as long as the photovoltaic cell is matched with the load * and directly coupled (such as the load being a charged battery), the volt ampere characteristic curve of the load can coincide or gradually coincide with the trajectory curve of the maximum power point, so that the photovoltaic cell is in the output state. But in daily applications, it is difficult to meet the direct coupling conditions between the load and the photovoltaic cell. Therefore, an important way to improve the overall efficiency of photovoltaic power generation systems is to change the system load characteristics in real time, that is, adjust the operating point of photovoltaic cells so that they can always work near the maximum power point under different sunshine and temperature conditions. This tracking process is called maximum power point tracking, as shown in the figure 1As shownMPPTBasic schematic diagram.

2、 The influencing factors of the maximum power point

Under certain lighting intensity and ambient temperature, photovoltaic cells can operate at different output voltages, but only at a certain output voltage value can the output power of the photovoltaic cell reach its maximum value. At this point, the operating point of the photovoltaic cell reaches the maximum point of the output power voltage curve, which is called the maximum power point.

IIIMPPTProblems in the application of technology

Mistracking phenomenon

mostMPPTThe algorithm only collects the voltage and current of photovoltaic cells and tracks them based on the idea of disturbance observation. However, it is impossible to know whether the change in output power of photovoltaic cells is caused by disturbances or changes in the external environment. Therefore, when the environment changes rapidly, it is prone to false tracking. There are mainly the following types of solutions:

① Open loop control based on the environment;

② Make the power change caused by algorithm disturbance greater than the power change caused by environmental changes;

③ Identify and compensate for power changes caused by environmental changes.