The Introduction of PV inverter MPPT

The PV array is affected by factors such as sunlight intensity, temperature and load resistance, and environmental shading, its voltage and current will change accordingly, and the output power will also be affected accordingly. When there are clouds, trees, and building shadows around it, the output power of photovoltaic modules decreases. When the surface of the module is covered by leaves or dust, the output power of the PV module decreases. In these cases, the output characteristic curve of the PV array is multi-pole points, and how to find the highest point requires MPPT to achieve it. This article will guide readers to understand the MPPT!

What is the MPPT? MPPT is the core technology of the inverter, MPPT voltage is a very critical parameter in the design o photovoltaic power plants.. The full name of MPPT controller is "Maximum Power Tracking" (Maximum Power Point Tracking) solar controller, which is an upgraded product of traditional solar charge and discharge controller.

The MPPT controller can detect the generation voltage of the solar panel in real time and track the highest voltage and current value (VI), so that the system can charge the battery at maximum power output. Applied to the solar photovoltaic system, it is the brain of the photovoltaic system to coordinate the work of solar panels, batteries and loads. The maximum power point tracking system is an electrical system that can effectively store the direct current emitted by the solar panels in the battery by adjusting the working state of the electrical module, so that the photovoltaic panels can output more electric energy, and can effectively solve the domestic and industrial electricity consumption in remote areas and tourist areas that cannot be covered by the conventional power grid, without producing environmental pollution.

Due to the influence of external factors such as light intensity and environment, the output power of the solar cell is changing, and the light intensity emits more electricity, and the photovoltaic inverter with MPPT maximum power tracking is to make full use of the solar cell to make it run at the maximum power point. That is to say, under the condition that the solar radiation is constant, the output power after MPPT will be higher than that before without MPPT, which is the role of MPPT.

With the development of electronic technology, the MPPT control of the current solar array is generally completed by the DC/DC conversison circuit,. The PV cell array and the load are connected through the DC/DC circuit, and the maximum power tracking device continuously detects the current and voltage changes of the PV array, and adjusts the duty cycle of the PWM drive signal of the DC/DC convert according to the change.

For linear circuits, the power supply has a maximum power output when the load resistance is equal to the internal resistance of the power supply. Although both photovoltaic cells and DC/DC conversion circuits, are strongly nonlinear, they can be considered linear circuits in a very short period of time. Therefore, as long as the equivalent resistance of the DC-DC conversion, circuit is adjusted so that it is always equal to the internal resistance of the photovoltaic cell, the maximum output of the photovolltaic cell can be realized, and the MPPT of the photovoltaic cell can be realized. At present, the maximum power point tracking technology of photovoltaic arrays has been studied to a certain extent, and varous contraol methods have been developed, and the following are commenly used. Constanct voltage tracking method is referred to as CVT. Perturbatin and observation method is referred to as P&O. Incremental conductance method is referred to as INC, conductance increment method based on gradient step size, and so on. These algorithms can only be used in unobstructed conditions.