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The structure of photovoltaic power generation
- Jul 12, 2018 -

1. System composition

Photovoltaic power generation system is composed of solar cell array, battery pack, charge and discharge controller, inverter, AC power distribution cabinet, sun tracking control system and other equipment. The role of some of its equipment is:

1) Battery array

In the case of illumination (whether it is sunlight or the illumination produced by other illuminants), the battery absorbs light energy, and the accumulation of a different type of charge at both ends of the battery produces a "photogenerated voltage", which is the "photovoltaic effect". Under the action of the photovoltaic effect, the two ends of the solar cell generate an electromotive force, which converts light energy into electrical energy, which is a device for energy conversion. Solar cells are generally silicon cells, which are classified into single crystal silicon solar cells, polycrystalline silicon solar cells, and amorphous silicon solar cells.

Portable solar generator-solar panel.jpg

2) Battery pack

Its function is to store the energy emitted by the solar cell array when it is illuminated and to supply power to the load at any time. The basic requirements for solar cell power generation for the battery pack used are: a. Low self-discharge rate; b. Long service life; c. Strong deep discharge capability; d. High charging efficiency; e. Less maintenance or maintenance-free; f. Wide range; g. Low price.

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3) Controller

It is a device that can automatically prevent overcharging and overdischarging of the battery. Since the number of cycles of charging and discharging of the battery and the depth of discharge are important factors determining the service life of the battery, it is indispensable to control the charge and discharge controller of the battery pack for overcharging or overdischarging.

4) Inverter

It is a device that converts direct current into alternating current. Since the solar cell and the battery are DC power supplies,

The inverter is essential when the load is an AC load. Inverter can be divided into independent running inverter and grid-connected inverter according to the operation mode. The independently operated inverter is used in a stand-alone solar cell power generation system to supply independent loads. Grid-connected inverters are used in solar cell power generation systems that operate in parallel. The inverter can be divided into a square wave inverter and a sine wave inverter according to the output waveform. The square wave inverter circuit is simple, low in cost, but has a large harmonic component, and is generally used in systems below several hundred watts and with low harmonic requirements. Sinusoidal inverters are costly, but can be applied to a variety of loads.

2. System classification

Photovoltaic power generation systems are divided into independent photovoltaic power generation systems, grid-connected photovoltaic power generation systems and distributed photovoltaic power generation systems.

1) Independent photovoltaic power generation is also called off-grid photovoltaic power generation. It is mainly composed of a solar cell module, a controller, and a battery. To supply power to an AC load, an AC inverter needs to be configured. Independent photovoltaic power plants include village power supply systems in remote areas, solar household power systems, communication signal power supplies, cathodic protection, solar street lights, and other photovoltaic power generation systems with independent operation.

2) Grid-connected photovoltaic power generation is the direct current that is generated by solar modules directly connected to the public power grid after being converted into AC power that meets the requirements of the mains grid.

It can be divided into grid-connected power generation systems with and without batteries. The grid-connected power generation system with battery has schedulability, can be merged into or out of the grid as needed, and has the function of standby power supply, which can be powered urgently when the power grid is powered off. Photovoltaic grid-connected power generation systems with batteries are often installed in residential buildings; grid-connected power generation systems without batteries do not have the functions of schedulability and backup power, and are generally installed on larger systems. Grid-connected photovoltaic power generation has centralized large-scale grid-connected photovoltaic power plants, which are generally state-level power stations. The main feature is that the power generation can be directly delivered to the power grid, and the power grid can be uniformly deployed to supply power to users. However, this kind of power station has a large investment, a long construction period and a large area, and it has not developed much. Decentralized small-scale grid-connected photovoltaics, especially photovoltaic building integrated photovoltaic power generation, is the mainstream of grid-connected photovoltaic power generation due to its advantages of small investment, fast construction, small floor space and strong policy support.

3) Distributed photovoltaic power generation system, also known as decentralized power generation or distributed power supply, refers to the configuration of a small photovoltaic power generation system at or near the user site to meet the needs of specific users and support the existing distribution network. The economic operation, or both meet the requirements of these two aspects. The basic equipment of the distributed photovoltaic power generation system includes photovoltaic cell components, photovoltaic array brackets, DC combiner boxes, DC power distribution cabinets, grid-connected inverters, AC power distribution cabinets, etc. In addition, power supply system monitoring devices and environmental monitoring Device. The operation mode is that under the condition of solar radiation, the solar cell module array of the photovoltaic power generation system converts the electric energy converted by the solar energy into the DC power distribution cabinet through the DC combiner box, and is converted into the AC power supply by the grid-connected inverter. The building's own load, excess or insufficient power is regulated by connecting the grid.