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Inverters for photovoltaic power plants: three design options you need to know

Nov 21, 2020

Inverters for photovoltaic power plants: three design options you need to know

With the rapid development of the photovoltaic industry, competition in the industry has gradually become greater, technical routes are diverse, and the quality of photovoltaic equipment is uneven. Many photovoltaic users do not understand the composition of power stations and equipment selection, and do not know how to identify and maintain photovoltaic products. As the core equipment of photovoltaic power generation system-inverter, it is very important for users to have a detailed understanding of its type and applicable environment.

Inverter solution for centralized photovoltaic power station

The centralized inverter has a history of more than ten years of application and is currently the most technologically mature photovoltaic power plant inverter solution. The photovoltaic power station is composed of components, combiner boxes, inverters, box transformers, and power grid. The centralized inverter scheme is photovoltaic module power generation. The current is collected by the combiner box, and the DC is transmitted to two 500KW inverters, and then through double splitting Box transformers are connected to the grid.

Features of the centralized inverter solution:

1. Mature technology, suitable for large ground power stations;

2. The transmission voltage is low and the loss is large;

3. The number of MPPT (Maximum Power Tracking) is small and the power generation is not high;

4. Centralized grid connection, good grid adaptability;

5. The inverter cost is lower.

Inverter solution for string photovoltaic power station

The string inverter scheme is that the photovoltaic modules are directly transmitted to the inverter to be converted into AC power after the power is generated, and then transmitted to the dual-winding box transformer and grid-connected through the AC combiner box. Compared with the centralized type, the string inverter has lower power, a single inverter is only between 5k and 50kw, and each inverter has MPPT. Therefore, the number of MPPTs in the case of 1MW is far more than that of the centralized type. The power generation capacity has also increased.

Features of the string inverter solution:

1. The inverter is small, suitable for distributed projects or home photovoltaic projects;

2. Power generation is more than centralized;

3. Due to the small power of a single unit, more inverters are needed per MW, and the corresponding cost is higher;

4. Maintenance is relatively easy and can be replaced directly;

5. There are many grid-connected points, which are prone to resonance, and the adaptability of the grid is not good.

Inverter solution for distributed photovoltaic power station

Compared with the centralized inverter solution, the difference is that the distributed inverter solution moves the MPPT forward to the combiner box, increases the number to be consistent with the string type, and increases the boost function in the combiner box to reduce transmission loss. Solve the two major shortcomings of centralized.

Features of the distributed inverter solution:

1. Centralized grid connection, good grid adaptability;

2. The cost is between the centralized type and the string type;

3. The power generation is improved, while the loss is reduced, and the system efficiency is high;

4. It is suitable for large power stations and also for distributed projects.

At present, both string and distributed inverter solutions have gradually become the mainstream of the market. Just as 50% of the projects in the "Lead Runner" plan use string inverters, another investment hotspot, photovoltaic distributed projects, For example, household photovoltaic power plants and photovoltaic poverty alleviation projects basically use string inverters. For distributed inverters, there are still comparative advantages in large-scale distributed projects and large-scale mountain photovoltaic power stations.