Characteristics and problems of photovoltaic grid-connected power generation system


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.

(3) The output characteristics of photovoltaic arrays have multi-peak characteristics. Photovoltaic power plants have a large area of photovoltaic arrays, sometimes different types of photovoltaic modules can be combined, or even if the module type is the same, due to clouds, dust, aging and other reasons, the components do not match, so that its output characteristics show multi-peak characteristics, reducing the power generation efficiency of photovoltaic arrays.

(4) Power quality problems generated after the photovoltaic grid-connected power generation system is connected to the grid. For example, the direction of the power flow in the grid will change, resulting in increased line losses and relay protection that needs to be readjusted; PV systems are random and volatile, causing grid voltage fluctuations; A large number of power electronics are used in photovoltaic systems, which can cause harmonic pollution to the power grid.