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21-22 System Classification and Configuration: Characteristics and Classification of Photovoltaic System

Author: Source: Datetime: 2016-12-24 11:34:42
Photovoltaic power generation system without greenhouse gas emissions, which is called "green" energy. It has the following main advantages:

① without fossil fuels, solar energy around the world, access to inexhaustible;

② no moving, rotating parts, pollution-free, no noise, life can be as long as 30 years:

③ construction period is short, even large - scale photovoltaic power plants, from design to construction and installation can be completed in 3 to 6 months;

④ operation and maintenance costs are very low, only about 1/10 of conventional power stations;

⑤ can be adapted to local conditions, the nearest set, the application is very convenient;

⑥ modular structure, the scale can be adjusted to large GW-scale centralized power plant, small to distributed household roof photovoltaic systems, and even solar energy products.

The shortcomings of photovoltaic power generation system is volatile, not continuous, as wind power and other renewable energy sources. There are three technical ways to deal with such intermittent energy use:

① system configuration energy storage device;

② grid-connected power generation, the generated energy can be "stored" on the grid for storage regulation;

③ more complementary power generation, and the construction of micro-grid.

Photovoltaic systems (PV systems) are classified, usually in the relationship to the public grid, into two categories: stand-alone and grid-connected. Which independent type and load type is divided into special load and general load, or by system structure is divided into mixed type, no energy storage battery type, battery type. Grid-type system is divided into reversible flow and irreversible flow two. The system classification is shown in Figure 2-1.

PV system classification
Figure 2-1 PV system classification

The so-called independent photovoltaic power generation system, refers to the power system does not have any relationship between the closed system. It is typically used for portable power supplies, remote areas of existing power grids or equipment, and for any power supply that does not want to be connected to the grid.

(1) with a dedicated load of photovoltaic power generation system

A photovoltaic system with a dedicated load may be constructed and designed only in accordance with its load requirements. Therefore, the output power of DC or for any frequency of AC, is more applicable. This kind of system, uses the frequency conversion velocity modulation movement to be technically feasible. If the pump in the PV system, click on the load case, start by the inverter can inhibit the impact of current, while the inverter can be miniaturized.

(2) with the general load of photovoltaic power generation system

A photovoltaic power generation system with a general load is a power supply system in which an unspecified load is in a certain range. As a load, usually electrical products, to run more convenient frequency. If the DC load, you can save the inverter. Of course, the actual situation may be AC, DC load has. Generally with a battery energy storage device, in order to solar panels generated during the day the electricity stored in the battery for night or rainy days to use. If the load is only for agricultural machinery can not set the battery - the load of photovoltaic power generation system can also be divided into local load system and distributed load system. The former as the remote areas of the family or some equipment, power, is a place in the use of local power generation and electricity systems. While the latter need to set up a small-scale distribution lines, so that the location of photovoltaic power plants outside the farther load can also supply power.

In the PV system, if the residual power is generated, the reversible system uses a system in which the power company buys surplus power. Now, almost all residential PV systems use reversible flow systems.
Grid-on system diagram

Figure 2-2 Grid-connected system

The irreversible flow system, in which the power demand in the area is generally larger than the output power of the PV system, is adopted without generating countercurrent power. In PV systems, it is not possible to confirm that the surplus power does not flow back into the grid. Therefore, even if a small current is generated, the system should automatically reduce the output power of the PV system or suspend the operation of the PV system.

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