How to build a reasonable and perfect large-scale photovoltaic power station is a complex system engineering, which requires a series of designs, such as capacity design, structural design, electrical design (including auxiliary equipment matching), square array bracket design of photovoltaic system. Fire protection, lightning protection, grounding and other safety design, thermal environment design, architectural design, packaging and transportation, installation, commissioning and operation design, maintenance and inspection design, as well as personnel training, data management, etc., and finally cost accounting and economic and social Benefit analysis, etc.
Capacity design of grid-connected photovoltaic system
Capacity design is the software design of the PV system and the most important key step in determining the performance of the PV system.
1. Factors affecting power generation
The factors affecting the power generation of grid-connected photovoltaic power plants can be summarized into the following three aspects.
(1) Installed capacity of grid-connected photovoltaic system
The so-called photovoltaic power plant installed capacity refers to the sum of the actual power of all solar modules in the system. In applications where the nominal power of the component is allowed to deviate, the actual power is often less than the nominal power.
Obviously, the installed capacity plays a decisive role in the power generation effect of the grid-connected photovoltaic power station. When the other conditions are the same, the larger the installed capacity (power) of the grid-connected photovoltaic power station, the more power generation.
(2) Performance ratio (PR)
PR (Performance Ratio), also known as system comprehensive efficiency, is an important indicator to measure the performance of a photovoltaic system. It is defined as the ratio of the amount of energy that the PV system outputs to the grid to the amount of solar energy received by the square matrix. It has nothing to do with the capacity of the photovoltaic system, the solar radiation at the installation site, and the inclination and orientation of the square.
In the grid-connected photovoltaic power station, the size of the PR and the system design, installation, quality of the parts, the efficiency of the balancing components (including inverters, control equipment, etc.) and the losses caused by the connection lines, as well as the operation and maintenance, etc. Related factors can be roughly divided into the following aspects.
1 mismatch loss. The square array of solar panels of grid-connected photovoltaic power plants consists of a large number of solar panel components. Even with all components of the same power, the optimum operating voltage and current of each component may not be exactly the same. In principle, when the components are connected, they should be classified in advance, the working currents are substantially the same in series, and the operating voltages in the component strings are substantially the same in parallel. However, in actual installation, often because of the large number of components, it is too late to select, so you have to mix and match, so that the total power of the entire array will be less than the sum of the power of each component.
2 connection loss. Cables need to be connected between components or components to the combiner box, inverter, etc. Since the cable itself has resistance and a large number of connection points, a slight carelessness during installation may result in poor contact. Some connecting cables are too thin and can cause large line losses.
3 cover loss. During operation, dust is deposited on the surface of the square. Since the solar cell array of the grid-connected photovoltaic system has a small inclination angle, it is often impossible to clean the square surface by relying only on rainwater scouring. If it is not cleaned in time, it will affect the power generation of the photovoltaic system. In addition, some solar battery squares have trees or building floating objects in front of them, and some systems are designed so that the distance between the front and rear squares is too small, which will cause speed loss.
Many modern solar cell modules have been developed in large scale, and many cells are often connected in series. Even if the area to be shielded is small, the output power will be greatly affected.