Problems of photovoltaic grid-connected power generation system and its key technologies


According to the different operation modes, photovoltaic power generation systems can be divided into three types: stand-alone, grid-connected and hybrid. Compared with the independent photovoltaic power generation system, the former can use the transmission lines in the power system to realize the long-distance transmission of electric energy, and has the advantages of grid power support, and basically does not need to consider the influence of load characteristics. At present, China's photovoltaic grid-connected power generation system has two development modes: large-scale development, medium and high voltage access and decentralized development, and low-voltage local access, so China's photovoltaic grid-connected power generation system can be divided into centralized and distributed.

1. Characteristics of distributed centralized photovoltaic systems.

The distributed photovoltaic grid-connected power generation system is located on the user side, generating power to supply the local power load, occupying a small area and flexible operation mode. Mainly used in roofs, buildings, greenhouses, fish pond pumps, street lamps and other occasions. Centralized photovoltaic grid-connected power generation system mainly refers to large-scale photovoltaic power stations, which are directly supplied to high-voltage transmission systems as large-capacity power sources. Generally built in the desert, flexible site selection, short construction period, stable output, flexible operation mode, easy to participate in power grid voltage regulation and frequency regulation, low operating cost.

2. There are common problems with distributed and centralized photovoltaic systems.

Currently, distributed and centralized PV systems have the following common problems:

(1) Optimal configuration of photovoltaic arrays. Before installing the photovoltaic array, the module selection, module installation tilt angle, array topology, etc. should be optimized according to factors such as design requirements and the surrounding environment to improve the power generation efficiency of the photovoltaic system.

(2) Temperature rise, mismatch and hot spots of the photovoltaic array. The working environment of photovoltaic systems is relatively complex. Over time, dust accumulates on the surface of the components, and even leaves and bird droppings. Sometimes the component is obscured by surrounding buildings and trees, and the temperature of the component rises significantly. As the temperature of a module increases, its output voltage and power decrease. These conditions can lead to PV array mismatch, and in severe cases, a hot spot effect, reducing the service life of the module.