Recently, photovoltaic companies released the financial reports of the first quarter of 2023, compared with the relatively weak market in the first quarter of 2022, the financial reports in the first quarter of this year are very outstanding. The popularity of renewable power is still unabated, the market demand for renewable energy is also growing, and the technology of maximum energy utilization efficiency is also getting more and more attention. Maximum Power Point Tracking (MPPT) technology plays an important role in renewable energy systems such as wind power and solar power generation. This article will introduce the principle of MPPT and how it works, and how it optimizes energy conversion efficiency.
What is MPPT
MPPT, full name for Maximum Power Point Tracking, is a power conversion technology designed to ensure that power generation equipment (such as inverters) is always operating near the maximum power point. The MPPT system monitors and adjusts the working points of power generation equipment in real time to maximize the potential of renewable energy sources and improve energy conversion efficiency.
Why using MPPT
In solar power generation systems, photovoltaic modules have different output power under different environmental conditions, such as different irradiance and different temperatures. Taking JAM72D40-570/MB PV module as an example, the Current-Voltage curves and Power-Voltage curves under different irradiance are shown in Figure 1. Current-Voltage Curves at different temperatures are shown in Figure 2.
As it can be seen from the Figure 1, different environmental conditions have a greater impact on the power generation of photovoltaic modules. In Current-Voltage Curve of Figure 1 (left curve), different irradiance has a great influence on current and voltage, especially on current. The product of current and voltage is power, so the output power of PV modules varies greatly under different irradiation conditions. Under the same irradiance, the current and voltage of the PV modules also have many different combinations, that is, the PV modules has many different operating points, and the different operating points have a great impact on the output power of the PV modules, as shown in the Power-Voltage Curve in the right curve of Figure 1, there must be a maximum power point, which is the point that MPPT tracks.
MPPT Principle
MPPT technology usually use electronic circuits or control algorithms to monitor the output power of the power generation equipment and adjust the operating point of the power generation equipment according to changes in environmental conditions. This maximizes the potential of renewable energy sources, improves energy conversion efficiency, and ensures that as much energy as possible is delivered to the power grid or storage devices. The MPPT principle on the market mainly has the following types: Perturbation & Observation method, Incremental Conductance method, Constant Voltage method, etc. The most commonly used method is the Perturbation & Observation method. This article focus on the principle of the Perturbation & Observation method and how to maximize the output power of the PV modules.
Perturbation & Observation
Perturbation & Observation method, as the name suggests, it will regularly give the PV modules in photovoltaic system a perturbation on output voltage, and observe the power situation after the perturbation, then decide the next action, finally achieve the maximum power output of the PV module.
Figure 3 shows the P-V curve of a PV modules under a certain irradiance, and the maximum power point is at Pmax. Here listed some scenarios to explain the principle of Perturbation and Observation method based on the four power points A,B,C and D.
Scenario 1, assuming that the PV module is working at point A, first record the power Pa at point A, then we give the output voltage of the PV modules A positive perturbation ΔU, after which the module working point reaches point B, and then record the output power Pb of the PV modules at point B. Comparing the power of Pa and Pb, it can be seen from Figure 3 that the power at point B is greater than that at point A. It indicates the direction of the voltage perturbation is correct, and the next step is to continue to give voltage perturbation in the direction of A to B.
Besides the two scenarios mentioned above (A to B, C to D), there are two more scenarios shown in Figure 3, totally four scenarios, which is listed in table 1.