The grid-connected photovoltaic power system can convert the direct current output by the solar cell array into alternating current with the same amplitude, frequency and phase as the grid voltage, and realize the connection with the grid and transmit electric energy to the grid.

The flexibility of this power generation system lies in that when the sunshine is strong, the photovoltaic power generation system supplies power to the AC load while sending excess power to the grid; when the sunshine is insufficient, that is, the solar array cannot provide enough power for the load, It can also obtain power from the grid to supply power to the load.

1. Structure of grid-connected photovoltaic power generation system

The solar photovoltaic power generation system connected to the public grid is called a grid-connected photovoltaic power generation system. The system structure includes solar cell arrays, DC/DC converters, DC/AC inverters, AC loads, transformers and other components.

The grid-connected photovoltaic power generation system can convert the direct current output by the solar cell array into alternating current with the same amplitude, frequency and phase as the grid voltage, and realize the connection with the grid and transmit electric energy to the grid. The flexibility of this power generation system lies in that when the sunshine is strong, the photovoltaic power generation system supplies power to the AC load while sending excess power to the grid; when the sunshine is insufficient, that is, the solar array cannot provide enough power for the load, It can also obtain power from the grid to supply power to the load.

In the past, due to the high cost of solar cells, photovoltaic power generation was mostly only used in some dedicated independent operating systems, such as aerospace, frontier defense islands, or demonstration projects in remote areas. With the emergence of new photovoltaic materials, product prices continue to decline, conversion efficiency has been continuously improved, the introduction of advanced power electronic devices, microprocessors, and the application of advanced control strategies have made the research and mass promotion of photovoltaic grid-connected technology It is becoming more and more possible, and photovoltaic utilization is gradually developing in the direction of urban grid-connected photovoltaic power plants, residential photovoltaic building integration and low-power household photovoltaic grid-connected systems.

2. The form of grid-connected photovoltaic power generation system

The initial form of the combination of photovoltaics and buildings is to install a general solar cell array on the roof or balcony of the building, and equip it with a battery for independent power supply, or connect it in parallel with the public grid through an inverter controller and transformer output, so that the grid Together with the photovoltaic array, it supplies power to the building.

A further form of combining photovoltaics with buildings is to integrate photovoltaic modules with building materials, and use special materials and techniques to make photovoltaic modules into components such as roofs, exterior walls, and windows. In this way, photovoltaic modules can be directly used as building materials and generate electricity, which further reduces the cost of electricity generation.

When the photovoltaic power generation system is combined with buildings, it usually adopts the form of grid-connected power generation. Compared with the independent photovoltaic power generation system, this type of system has the following five outstanding advantages:

1. In rainy days or at night, the power grid supplies power to the load. In this way, the system does not need to be equipped with energy storage devices, which can not only reduce the system cost, but also avoid the trouble of maintaining and replacing solar batteries, and increase the reliability of power supply;

2. The electric energy generated when there is sunshine can be used for the load in the building, and if there is excess, it can be fed back to the grid;

3. In the grid-connected photovoltaic power generation system, it is not limited by the state of charge of the battery, and can access electric energy to the grid at any time;

4. When designing the inclination angle of the solar cell array, the angle corresponding to the maximum solar radiation received throughout the year can be taken to maximize the power generation capacity of the solar cell array;

5. The solar radiation intensity in summer is high, and the electric energy generated by the solar cell array is relatively large, and summer is also the peak period of electricity consumption. The role of peak shaving.