A solar photovoltaic power generation system refers to a power generation system that directly converts light energy into electrical energy without a thermal process. Its main components are solar cells, accumulators, controllers and photovoltaic inverters. It is characterized by high reliability, long service life, no environmental pollution, independent power generation and grid-connected operation.
The composition of solar photovoltaic power generation system
Photovoltaic power generation systems are usually composed of photovoltaic arrays, battery packs (optional), battery controllers (optional), inverters, AC power distribution cabinets, and sun tracking control systems: high-power concentrating photovoltaic systems (HCPV) also Including the condenser part (usually a condenser lens or mirror).
The functions of each part of the solar photovoltaic power generation system are as follows:
1. Photovoltaic square array
Photovoltaic array (PV Array), called photovoltaic array, is a DC power generation unit composed of several photovoltaic modules or photovoltaic panels assembled together in a certain way and with the same support structure. In the case of light generated by a luminous body), the battery absorbs light energy, and the accumulation of opposite-signal charges occurs at both ends of the battery, that is, a "photo-generated voltage" is generated. This is the "photovoltaic effect". Under the action of photovoltaic effect, electromotive force is generated at both ends of the solar cell, which converts light energy into electric energy and completes the energy conversion.
2. Battery pack (optional)
The function of the battery pack is to store the electric 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 the battery pack used in solar cell power generation are: ① low self-discharge rate; ② long service life; ③ deep discharge Strong ability; ④ high charging efficiency; ⑤ less maintenance or maintenance-free; ⑥ working temperature range is the same; ⑦ low price.
3. Battery controller (optional)
The battery controller is a device that can automatically prevent the battery from being overcharged and overdischarged. Since the number of cycles of charge and discharge and the depth of discharge of the battery are important factors that determine the service life of the battery, the battery controller that can control the overcharge or overdischarge of the battery pack is an essential device.
4. Photovoltaic inverter
An inverter is a device that converts direct current to alternating current. When the solar cell and storage battery are DC power sources and the load is AC load, the inverter is indispensable. According to the operation mode, the inverter can be divided into off-grid inverter and grid-connected inverter. Off-grid inverters are used in stand-alone solar cell power systems to supply power to loads. The grid-connected inverter is used for the solar cell power generation system that is connected to the grid. The inverter can be divided into square wave inverter and sine wave inverter according to the output waveform. The circuit of the square wave inverter is simple and the cost is low, but the harmonic component is large. low system. Sine wave inverters are expensive, but can be applied to various loads.
5. Tracking system
Compared with a solar photovoltaic power generation system at a certain location, the sun rises and sets every day throughout the year, and the sun's illumination angle changes all the time. Only when the solar panels can face the sun at all times can the power generation efficiency reach the highest level. in good condition.
The sun tracking control systems commonly used in the world all need to calculate the angle of the sun at different times of each day of the year according to the latitude and longitude of the placement point, and store the sun position at each time of the year in PLC, single-chip computer or computer software. , that is, by calculating the position of the sun to achieve tracking using computer data theory. It needs the data and settings of the latitude and longitude area of the earth. Once installed, it is inconvenient to move or disassemble. After each move, you must reset the data and adjust various parameters.