Composition and classification of solar photovoltaic power generation

Composition of solar photovoltaic power generation

In addition to the solar cell array described above, the solar photovoltaic power generation system also includes anti-reverse charging diodes, battery packs, control equipment, and DC-AC inverters.

1. Anti-reverse charge diode

Anti-reverse charging diodes are also called blocking diodes. When the solar cell fails, it cannot generate electricity normally. In the case of no sunlight at night and rainy days, the solar cell cannot generate electricity. At this time, in the solar cell module, the battery pack can be discharged through the solar cell array. The anti-reverse charging diode is connected in series in the square array circuit of the solar cell and plays the role of unidirectional conduction.

2. Battery pack

The function of the battery pack is to store the electric energy generated by the solar cell array when it is illuminated and to supply power to the load at any time. Batteries are divided into lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lead-acid batteries, etc. At present, the batteries used in China with solar photovoltaic power generation systems are mainly lead-acid batteries and nickel-cadmium batteries.

3. Control equipment

Control equipment is one of the important parts of the solar photovoltaic power generation system. The control equipment in the system should usually have the following functions:

①Signal detection function.

②Control the charging and discharging function of the battery.

③ Other equipment protection.

④Fault diagnosis and positioning.

⑤ Running status indication.

4. Inverter

An inverter is a device that converts direct current into alternating current. It is an important part of photovoltaic system. Since solar cells and batteries emit direct current, an inverter is essential when the load is an alternating current load. In general, inverters can not only convert direct current to alternating current, but also allow solar cells to maximize their performance, as well as protect the system in the event of anomalies and faults.

Specifically in the following aspects:

①Effectively remove the output power of solar cells affected by weather changes, with automatic operation stop function and maximum power tracking control function.

②As a protection system, it has a separate (island) operation prevention function and an automatic voltage regulation function.

③ When the system and the inverter are abnormal, it can be safely separated or the inverter can be stopped.

Classification of solar photovoltaic power generation

Photovoltaic power generation systems, that is, solar cell application systems, are generally divided into two categories: independent operating systems and grid-connected operating systems, as shown in Figure 1. The independent operation system is shown in Figure 1(a), which consists of a solar cell array, an energy storage device, a DC-AC inverter device, a control device and a connection device. The grid-connected operating system is shown in Figure 1(b).

Composition and classification of solar photovoltaic power generation
Figure 1 – Composition of a photovoltaic system

The so-called independent operating photovoltaic power generation system refers to a closed system that does not have any relationship with the power system. Figure 2 shows the classification of stand-alone systems.

The grid-connected photovoltaic power generation system shown in Figure 1(b) is actually the same as other types of power stations, which can provide electricity for the entire power system. Figure 3 is a schematic diagram of the photovoltaic power generation system networking. It can be seen from Figure 3 that there are two types of photovoltaic power generation grid-connected systems: centralized photovoltaic power station grid-connected and rooftop photovoltaic system grid-connected. The former power capacity is usually above the megawatt level, and the latter is between the kilowatt level and the 100 kilowatt level. The modular structure and other characteristics of photovoltaic systems are suitable for the development of this distributed power supply method.

Composition and classification of solar photovoltaic power generation
Figure 2 – Classification of stand-alone photovoltaic power generation systems
Composition and classification of solar photovoltaic power generation
Figure 3 – Schematic diagram of grid-connected photovoltaic power generation system