The composition of solar photovoltaic power generation system

A power generation system that converts solar radiant energy into electrical energy through solar cells is called a solar photovoltaic power generation system, or it can also be referred to as a photovoltaic power generation system for short. Although the application forms of solar photovoltaic power generation systems are diverse and the scale of application is also large (from small to less than 1W solar lawn lamp applications, to hundreds of kilowatts or even dozens of megawatts of large-scale photovoltaic power plant applications), the composition of the system It is basically the same as the working principle, mainly composed of solar cell components (or array), energy storage batteries (packs), photovoltaic controllers, photovoltaic inverters (used when there is a need to output AC power), etc., and DC combiner boxes , DC power distribution cabinets, AC combiner boxes or power distribution cabinets, step-up transformers, photovoltaic supports, and some auxiliary facilities such as testing, monitoring, and protection.

The composition of solar photovoltaic power generation system
The composition of solar photovoltaic power system

1. Solar cell module

Solar cell modules are also called photovoltaic panels, which are the core components of photovoltaic power generation systems that realize photoelectric conversion, and they are also the most valuable part of photovoltaic power generation systems. Its function is to convert the radiant energy of sunlight into DC electric energy and send it to the storage battery for storage. It can also be used directly to drive DC loads or convert it into AC power through a photovoltaic inverter to supply power to users or connect to the grid. When the power generation capacity is large, it is necessary to use multiple battery modules in series and parallel to form a solar cell array. The solar cell modules currently used are mainly divided into crystalline silicon modules and thin film modules. Crystal silicon components are divided into single crystal silicon components and polycrystalline silicon components; thin film components include amorphous silicon components, microcrystalline silicon components, copper indium gallium selenium (CIGS) components, and cadmium telluride (CdTe) components.

2. Energy storage battery

Energy storage batteries are mainly used for off-grid photovoltaic power generation systems and grid-connected photovoltaic power generation systems with energy storage devices. Its function is mainly to store the electrical energy generated by solar cells and can supply power to the load at any time. The basic requirements of photovoltaic power generation systems for batteries are low self-discharge rate, long service life, high charging efficiency, strong deep discharge capability, wide operating temperature range, little or no maintenance, and low price. At present, photovoltaic power generation systems mainly use lead-acid batteries, lead-carbon batteries, lithium iron phosphate batteries, ternary lithium batteries, etc. In small and micro systems, nickel-hydrogen batteries, nickel-cadmium batteries, lithium-ion batteries or super batteries can also be used. Capacitors, etc. When there is a large-capacity electric energy storage, it is necessary to connect multiple batteries in series and parallel to form a battery pack.

3. Photovoltaic controller

The photovoltaic controller is the main component of the off-grid photovoltaic power generation system. Its function is to control the working state of the entire system, protect the battery; prevent the battery from overcharging, overdischarging, system short circuit, system polarity reversal, and anti-recharge at night. In places with large temperature differences, the controller also has the function of temperature compensation. In addition, the photovoltaic controller has working modes such as light-controlled switches and time-controlled switches, as well as display functions for various working states such as charging status, power consumption status, and battery power. Photovoltaic controllers are generally divided into low-power, medium-power, high-power, and wind-solar hybrid controllers.

4. Photovoltaic inverter

The main function of the photovoltaic inverter is to convert as much of the DC power output by the battery assembly or the energy storage battery as possible into AC power for use by the power grid or users. According to different operation modes, photovoltaic inverters can be divided into grid-connected inverters and off-grid inverters. Grid-connected inverters are used for photovoltaic power generation systems that are connected to the grid. Off-grid inverters are used for independent operation of photovoltaic power generation systems. Because under certain working conditions, the power output of photovoltaic modules will change with the change of the output voltage at both ends of the photovoltaic modules, and the power output of the modules is the largest at a certain voltage value, so photovoltaic inverters generally have the maximum power Point tracking (MPPT) function, that is, the inverter can adjust the voltage at both ends of the battery assembly so that the power of the battery assembly always outputs the maximum.

5. DC combiner box

The DC combiner box is mainly used in photovoltaic power generation systems with tens of kilowatts or more. Its purpose is to centrally input and group the multiple DC output cables of the battery module square array to the DC combiner box, and pass the photovoltaic in the DC combiner box. After the protection and detection of special fuses, DC circuit breakers, surge protectors and intelligent monitoring devices, etc., the confluence is output to the photovoltaic inverter. The use of the DC combiner box greatly simplifies the connection between the battery components and the inverter, improves the reliability and practicability of the system, not only makes the line connection orderly, but also facilitates group inspection and maintenance. When the component square array fails locally, it can be partially separated for maintenance, without affecting the continuous operation of the overall power generation system, ensuring that the photovoltaic power generation system exerts its maximum efficiency.

6. DC power distribution cabinet

In a large-scale grid-connected photovoltaic power generation system, in addition to many DC combiner boxes, several DC distribution cabinets are also used as the second and third-level confluence in the photovoltaic power generation system. The DC power distribution cabinet is mainly to connect the DC cables output by each DC combiner box to converge again, and then connect the output to the grid-connected inverter, which is beneficial to the installation, operation and maintenance of the photovoltaic power generation system.

7. AC power distribution cabinet and combiner box

The AC power distribution cabinet is the power equipment that connects the inverter and the AC load or the public grid in the photovoltaic power generation system. Its main function is to receive, dispatch, distribute and measure the electric energy to ensure the safety of power supply and display various electric energy parameters. And monitor faults. The AC combiner box is generally used in the string inverter system, and its main function is to send the AC power output by multiple inverters into the AC power distribution cabinet after a secondary centralized convergence.

8. Step-up transformer

The step-up transformer is mainly used in the photovoltaic power generation system to boost the low-voltage alternating current (0.4kV) output by the inverter to the same medium and high voltage (such as 10kV, 35kV, 110kV, 220kV, etc.) with the grid-connected voltage level. The network realizes the long-distance transmission of electric energy. Small grid-connected photovoltaic power generation systems are basically directly connected to the grid on the user side, self-generated and used, and the surplus power is directly fed into the 0.4kV low-voltage grid, so there is no need for a step-up link.

9. Photovoltaic bracket

Photovoltaic brackets used in photovoltaic power generation systems mainly include fixed inclination brackets, adjustable inclination brackets and automatic tracking brackets. Automatic tracking bracket is divided into single-axis tracking bracket and dual-axis tracking bracket. The single-axis tracking bracket can be subdivided into flat single-axis tracking, oblique single-axis tracking and azimuth single-axis tracking brackets. In photovoltaic power generation systems, fixed tilt angle brackets and tilt angle adjustable brackets are currently the most widely used.

10. Auxiliary facilities of photovoltaic power generation system

The ancillary facilities of the photovoltaic power generation system include the monitoring and detection system of the system operation, the lightning protection grounding system, etc. The monitoring and detection system comprehensively monitors the operating status of the photovoltaic power generation system, including the operating status of the battery module string or square array, the working status of the inverter, the voltage and current data of the photovoltaic square array, the output power of the power generation, the grid voltage frequency, and the solar radiation data Etc., and can be monitored through remote connection of wired or wireless network, and data can be obtained through terminal devices such as computers and mobile phones.