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Selection Principles Of Inverters In Industrial And Commercial Power Stations

In the process of building an industrial and commercial power station, there are many issues that need to be considered, such as power consumption level, construction site, grid connection, process approval, etc. All owners pay more attention to the initial investment cost, because it is related to the cost of electricity, which is defined as follows:

LCOE(Standardized cost of electricity generation)=(total initial investment cost + Total cost of operation and maintenance – System residual value)/ Cumulative power generation in 25 years of life cycle * total decay rate

As an important control device in a photovoltaic power station, the selection and configuration of the inverter is not only related to the stability and output capacity of the system, but also has an important impact on the cost of electricity. Therefore, the selection of the inverter is crucial important.

一.Growatt Inverters for industrial and commercial power stations should be large rather than small

The big here refers to the output power of the inverter. The total capacity of industrial and commercial power stations is generally several hundred kilowatts to 10MW+. If you choose an inverter with a smaller rated output, the number will increase greatly. Correspondingly, you need to increase cables, power distribution facilities, grid-connected devices (grid-connected points), and more Construction costs. For example, for a 1.2MWp rooftop power station built by a textile company in East China, eight 125kW string inverters can be directly selected, compared with 20 50kW, ten 100kW, or nine 110kW inverters. It is basically the same, but the price of purchasing inverters must be different; in addition to the above-mentioned increased costs, it also increases potential failure points.

Therefore, when the number of strings is determined, the model with higher power is given priority. In addition, attention should also be paid to the uniformity of the equipment in the selection of the model, and the selection of the model should not be too complicated, so as to minimize the troubles caused by the later measurement and operation and maintenance.

二.Choose a model that supports high-current components

At present, the mainstream components in the market are mainly 182 and 210 types. The 182 type components have a high open circuit voltage, generally at 49.XX V, and the current is relatively small, generally at 13.XX A; while the 210 components have a low open circuit voltage, generally around 40V. , but the current is very large, ranging from 17A to 20A+. The corresponding inverters of various manufacturers allow an input current of about 16A. Matching 182 modules is very flexible and can be connected serially and can achieve the required capacity ratio, but matching 210 modules will be limited by capacity. Growatt recently launched the MAX series upgraded inverter with 22.5A string current, which can perfectly solve this problem.

三.Distributed components and inverters need to be centralized

Industrial and commercial power stations are mostly built on the roofs of factory buildings or buildings, and often a power station covers multiple roofs. The sizes of the roofs or sites are different, and the number of installed components is different, so the power carried is also different. If you simply choose the inverter according to the power of each area, there may be many types. In this way, it will be more troublesome when selecting cables and power distribution devices, and it will increase the probability of errors during installation.

Therefore, this kind of project should generally be considered as a whole first, and the appropriate inverter should be selected according to the total component power, and the model should be as uniform as possible; drop to lowest.

Situations that cannot be included as a whole include: component arrays installed too far away, component arrays with completely different orientations, component arrays with hard occlusions, components with inconsistent specifications or models, etc.

The picture above is a very typical example. A sewage treatment plant built a photovoltaic power station on the roof of its factory and in the open space of the factory area. The total capacity is 3MW. The power generation is mainly used for the production of the factory area and lighting power supply. It is relatively scattered, the capacity of each place is not large, and the distance between each installation point is relatively close. At this time, it should not be selected one by one, but should be considered as a whole. According to 183 pieces*540Wp=98.82Wp, choose the appropriate inverter. Specifically, the difficulty of wiring, the location of the transformer, and the delivery date of the equipment should also be considered.

四.Always pay attention to improving the capacity ratio

The capacity ratio is also very important in industrial and commercial power plants, which is related to the initial investment cost and the power generation efficiency of the system.

Due to the different sunlight resources in different regions and the changes in radiation in different seasons of the year, the output of the same type of photovoltaic modules varies greatly. If only the nominal power of the modules is used to calculate, it will be very different from the actual power generation. Similarly, if the inverter is selected according to the nominal power of the components at 1:1, in most of the resource areas of the three regions, the inverter cannot run at full load for a long time all year round, and the input cannot be guaranteed, resulting in Generation yields have been very different from expectations. The professional design principle is to make a reasonable over-allocation when selecting the model, so that the inverter can keep running at a high level, and the power generation effect will be good. It is generally recommended that the capacity and matching ratio of Class III areas should be between 1.15 and 1.35, and the median value is recommended to be 1.2 to 1.25.

The above summarizes several main principles for inverter selection in industrial and commercial projects. The purpose is to reduce the system cost of equipment, increase the power generation capacity of the system, reduce the construction cost of the system, the cost of auxiliary materials, and the difficulty of construction and operation and maintenance. In the implementation of specific projects, it is recommended to refer to and apply flexibly.

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