Introduction to the classification of solar photovoltaic systems

Generally, we divide photovoltaic systems into independent systems, grid-connected systems and hybrid systems. If according to the application form of the solar photovoltaic system, the application scale and the type of load, the photovoltaic power supply system can be divided in more detail. Photovoltaic systems can also be subdivided into the following six types: small solar power system (SmallDC); simple DC system (SimpleDC); large solar power system (LargeDC); AC and DC power supply system (AC/DC); grid-connected system (UtilityGridConnect); Hybrid power supply system (Hybrid); Grid-connected hybrid system. The working principle and characteristics of each system are explained below.

1. Small solar power system (SmallDC)

The characteristic of this system is that there is only DC load in the system and the load power is relatively small. The whole system has a simple structure and easy operation. Its main uses are general household systems, various civilian DC products and related entertainment equipment. For example, this type of photovoltaic system is widely used in the western region of my country, and the load is a DC lamp to solve the home lighting problem in areas without electricity.

2. Simple DC system (SimpleDC)

The characteristic of the system is that the load in the system is a DC load and there is no special requirement for the use time of the load. The load is mainly used during the day, so there is no battery or controller in the system. The system has a simple structure and can be used directly. Photovoltaic components supply power to the load, eliminating the need for energy storage and release in the battery, as well as energy loss in the controller, and improving energy utilization efficiency.

3 Large-scale solar power system (LargeDC)

Compared with the above two photovoltaic systems, this photovoltaic system is still suitable for DC power supply systems, but this kind of solar photovoltaic system usually has a large load power. In order to ensure that the load can be reliably provided with a stable power supply, its corresponding system The scale is also large, requiring a larger photovoltaic module array and a larger solar battery pack. Its common application forms include communication, telemetry, monitoring equipment power supply, centralized power supply in rural areas, beacon beacons, street lights, etc. 4 AC, DC power supply system (AC/DC)

Different from the above three solar photovoltaic systems, this photovoltaic system can provide power for both DC and AC loads at the same time. In terms of system structure, it has more inverters than the above three systems to convert DC power to AC power. The demand for AC load. Generally, the load power consumption of this kind of system is relatively large, so the scale of the system is also relatively large. It is used in some communication base stations with both AC and DC loads and other photovoltaic power plants with AC and DC loads.

5 grid-connected system (UtilityGridConnect)

The biggest feature of this kind of solar photovoltaic system is that the DC power generated by the photovoltaic array is converted into AC power that meets the requirements of the mains power grid by the grid-connected inverter, and then directly connected to the mains network. In the grid-connected system, the power generated by the PV array is not only supplied to AC Outside the load, the excess power is fed back to the grid. In rainy days or at night, when the photovoltaic array does not generate electricity or the generated electricity cannot meet the load demand, it will be powered by the grid.

6 Hybrid power supply system (Hybrid)

In addition to using solar photovoltaic module arrays, this type of solar photovoltaic system also uses diesel generators as a backup power source. The purpose of using a hybrid power supply system is to comprehensively utilize the advantages of various power generation technologies and avoid their respective shortcomings. For example, the advantages of the above-mentioned independent photovoltaic systems are less maintenance, but the disadvantage is that the energy output depends on the weather and is unstable. Compared with a single energy independent system, a hybrid power supply system that uses diesel generators and photovoltaic arrays can provide energy that does not depend on weather. Its advantages are:

1. The use of hybrid power supply system can also achieve better utilization of renewable energy.

2. Has a high system practicability.

3. Compared with a single-use diesel generator system, it has less maintenance and uses less fuel.

4. Higher fuel efficiency.

5. Better flexibility for load matching.

The hybrid system has its own shortcomings:

1. The control is more complicated.

2. The initial project is relatively large.

3. It requires more maintenance than a standalone system.

4. Pollution and noise.

7. Grid-connected hybrid power supply system (Hybrid)

With the development of the solar optoelectronics industry, there has been a grid-connected hybrid power supply system that can comprehensively utilize solar photovoltaic module arrays, mains and reserve oil machines. This kind of system is usually integrated with the controller and the inverter, using a computer chip to fully control the operation of the entire system, comprehensively using various energy sources to achieve the best working state, and can also use the battery to further improve the system’s load power supply guarantee rate , Such as AES’s SMD inverter system. The system can provide qualified power for local loads and can work as an online UPS (uninterruptible power supply). It can also supply power to the grid or obtain power from the grid.

The working mode of the system is usually to work in parallel with the mains and solar power. For local loads, if the electrical energy generated by the photovoltaic module is sufficient for the load, it will directly use the electrical energy generated by the photovoltaic module to supply the demand of the load. If the power generated by the photovoltaic module exceeds the demand of the immediate load, the excess power can be returned to the grid; if the power generated by the photovoltaic module is not enough, the utility power will be automatically activated, and the utility power will be used to supply the demand of the local load. When the power consumption of the load is less than 60% of the rated mains capacity of the SMD inverter, the mains will automatically charge the battery to ensure that the battery is in a floating state for a long time; if the mains fails, the mains power fails or the mains power If the quality is unqualified, the system will automatically disconnect the mains power and switch to an independent working mode. The battery and inverter provide the AC power required by the load.

Once the mains power returns to normal, that is, the voltage and frequency are restored to the above-mentioned normal state, the system will disconnect the battery and change to grid-connected mode operation, powered by mains. In some grid-connected hybrid power supply systems, system monitoring, control and data acquisition functions can also be integrated in the control chip. The core components of this system are the controller and inverter.